The Automobile Storage Battery: Its Care And Repair

Produced by George Davis, Mark Posey and Richard Allain

The Automobile Storage Battery Its Care And Repair

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Radio Batteries, Farm Lighting Batteries

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A practical book for the repairman. Gives in nontechnical language, the theory, construction, operation, manufacture, maintenance, and repair of the lead-acid battery used on the automobile. Describes at length all subjects which help the repairman build up a successful battery repair business. Also contains sections on radio and farm lighting batteries.

BY O. A. WITTE Chief Engineer, American Bureau of Engineering, Inc.

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Third Edition Completely Revised and Enlarged Fourth Impression Published 1922 by

The American Bureau Of Engineering, Inc. Chicago, Illinois, U. S. A.

Copyright, 1918, 1919, 1920, and 1922, by American Bureau of Engineering, Inc. All Rights Reserved.

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Entered at Stationers' Hall, London, England.

First Impression April, 1918. Second Impression December, 1919. Third Impression October, 1920. Fourth Impression September, 1922.

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Preface =======

Many books have been written on Storage Batteries used in stationary work, as in electric power stations. The storage battery, as used on the modern gasoline car, however, is subjected to service which is radically different from that of the battery in stationary work. It is true that the chemical actions are the same in all lead-acid storage batteries, but the design, construction, and operation of the starting and lighting battery, the radio battery, and the farm lighting battery are unique, and require a special description.

Many books have been written on Storage Batteries used in stationary work, as in electric power stations. The storage battery, as used on the modern gasoline car, however, is subjected to service which is radically different from that of the battery in stationary work. It is true that the chemical actions are the same in all lead-acid storage batteries, but the design, construction, and operation of the starting and lighting battery, the radio battery, and the farm lighting battery are unique, and require a special description.

This book therefore refers only to the lead-acid type of starting and lighting battery used on the modern gasoline Automobile, the batteries used with Radio sets, and the batteries used with Farm Lighting Plants. It is divided into two sections. The first section covers the theory, design, operating conditions, and care of the battery.

The second section will be especially valuable to the battery repairman. All the instructions given have been in actual use for years, and represent the accumulated experiences of the most up-to-date battery repair shops in the United States.

The first edition of this book met with a most pleasing reception from both repairmen and battery manufacturers. It was written to fill the need for a complete treatise on the Automobile Storage Battery for the use of battery repairmen. The rapid sale of the book, and the letters of appreciation from those who read it, proved that such a need existed.

The automobile battery business is a growing one, and one in which new designs and processes are continually developed, and in preparing the second and third editions, this has been kept in mind. Some of the chapters have been entirely rewritten, and new chapters have been added to bring the text up-to-date. Old methods have been discarded, and new ones described. A section on Farm lighting Batteries has been added, as the automobile battery man should familiarize himself with such batteries, and be able to repair them. A section on Radio batteries has also been added.

Special thanks are due those who offered their cooperation in the preparation and revision of the book. Mr. George M. Howard of the Electric Storage Battery Co., and Mr. C. L. Merrill of the U. S. Light & Heat Corporation very kindly gave many helpful suggestions. They also prepared special articles which have been incorporated in the book. Mr. Henry E. Peers consulted with the author and gave much valuable assistance. Mr. Lawrence Pearson of the Philadelphia Battery Co., Mr. F. S. Armstrong of the Vesta Accumulator Co., Messrs. P. L. Rittenhouse, E. C. Hicks and W. C. Brooks of the Prest-O-Lite Co., Mr. D. M. Simpson of the General Lead Batteries Co., Mr. R. D. Mowray and Mr. C. R. Story of the Universal Battery Co., Mr. H. A. Harvey of the U. S. Light and Heat Corporation, Mr. E. B. Welsh of the Westinghouse Union Battery Co., Mr. S. E. Baldwin of the Willard Storage Battery Co., Mr. H. H. Ketcham of the United Y. M. C. A. Schools, and Messrs. Guttenberger and Steger of the American Eveready Works also rendered much valuable assistance.

The Chapter on Business Methods was prepared by Mr. G. W. Hafner.

O. A. WITTE, Chief Engineer, American Bureau of Engineering, Inc. September, 1922

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Contents --------

1. Introductory

Gasoline and electricity have made possible the modern automobile. Steps in development of electrical system of automobile. Sources of electricity on the automobile.

2. Batteries In General

The Simple Battery, or Voltaic Cell. Chemical Actions which Cause a Cell to Produce Electricity. Difference between Primary and Secondary, or Storage Cells. A Storage Battery Does Not "Store" Electricity. Parts Required to Make a Storage Battery.

3. Manufacture Of Storage Batteries

Principal Parts of a "Starting and Lighting" Battery. Types of Plates Used. Molding the Plate Grids. Trimming the Grids. Mixing Pastes. Applying Pastes to the Plate Grids. Hardening the Paste. Forming the Plates. Types of Separators. Manufacture of Separators. Manufacture of Electrolyte. Composition and Manufacture of Jars. Types of Cell Covers. Single and Double Covers. Covers Using Sealing Compound Around the Cell Posts. Covers Using Lead Bushings Around the Cell Posts. The Prest-O-Lite Peened Post Seal. Batteries Using Sealing Nuts Around Cell Posts. Construction of Vent Tubes. Exide and U. S. L. Vent Tube Design. Vent Plugs, or Caps. Manufacture of the Battery Case. Assembling and Sealing the Battery. Terminal Connections. Preparing the Completed Battery for "Wet" Shipment. Preparing the Completed Battery for "Dry" Shipment. "Home-Made" Batteries.

4. Chemical Changes In The Battery

Chemical Changes in the Battery. Plante's Work on the Storage Battery. Faure, or Pasted Plates. How Battery Produces Electricity. Chemical Actions of Charge and Discharge. Relations Between Chemical Actions and Electricity.

5. What Takes Place During Discharge

What a "Discharge" Consists of. Voltage Changes During Discharge. Why the Discharge Is Stopped When the Cell Voltage Has Dropped to 1.7 on Continuous Discharge. Why a Battery May Safely be Discharged to a Lower Voltage Than 1.7 Volts per Cell at High Rates of Discharge. Why Battery Voltage, Measured on "Open Circuit" is of Little Value. Changes in the Density of the Electrolyte. Why Specific Gravity Readings of the Electrolyte Show the State of Charge of a Cell. Conditions Which Make Specific Gravity Readings Unreliable. Why the Specific Gravity of the Electrolyte Falls During Discharge. Why the Discharge of a Battery Is Stopped When the Specific Gravity Has Dropped to 1.150. Chemical Changes at the Negative Plates During Discharge. Chemical Changes at the Positive Plates During Discharge.

6. What Takes Place During Charge

Voltage Changes During Charge. Voltage of a Fully Charged Cell. Changes in the Density of the Electrolyte During Charge. Changes at the Negative Plates During Charge. Changes at the Positive Plates During Charge.

7. Capacity Of Storage Batteries

Definition of Capacity. Factors Upon Which the Capacity of a Battery Depend. How the Area of the Plate Surfaces Affects the Capacity. How the Quantity, Arrangement, and Porosity of the Active Materials Affect the Capacity. How the Quantity and Strength of the Electrolyte Affect the Capacity. Why Too Much Electrolyte Injures a Battery. Why the Proportions of Acid and Water in the Electrolyte Must Be Correct if Specific Gravity Readings Are to Be Reliable.

8. Internal Resistance

Effect of Internal Resistance. Resistance of Grids. Resistance of Electrolyte. Resistance of Active Materials.

9. Care Of Battery On The Car

Care of Battery Box. How to Clean the Battery. How to Prevent Corrosion. Correct Battery Cable Length. Inspection of Battery to Determine Level of Electrolyte. How to Add Water to Replace Evaporation. When Water Should Be Added. How Electrolyte Is Lost. Danger from Adding Acid Instead of Water. Effect of Adding Too Much Water. When Specific Gravity Readings Should Be Taken. What the Various Specific Gravity Readings Indicate. Construction of a Syringe Hydrometer. How to Take Specific Gravity Readings. Why Specific Gravity Readings Should Not Be Taken Soon After Adding Water to Replace Evaporation. Troubles Indicated by Specific Gravity Readings. How to Make Sure That Sections of a Multiple-Section Battery Receive the Same Charging Current. How Temperature Affects Specific Gravity Readings. How to Make Temperature Corrections in Specific Gravity Readings. Battery Operating Temperatures. Effect of Low and High Temperatures. Troubles Indicated by High Temperatures. Damage Caused by Allowing Electrolyte to Fall Below Tops of Plates. I-low to Prevent Freezing. Care of Battery When Not in Use. "Dope" or "Patent" Electrolyte, or Battery Solutions.

10. Storage Battery Troubles

Normal and Injurious Sulphation.-- How Injurious Sulphate Forms. Why An Idle Battery Becomes Sulphated. Why Sulphated Plates Must Be Charged at a Low Rate. How Over discharge Causes Sulphation. How Starvation Causes Sulphation. How Sulphate Results from Electrolyte Being Below Tops of Plates. How Impurities Cause Sulphation. How Sulphation Results from Adding Acid Instead of Water to Replace Evaporation. Why Adding Acid Causes Specific Gravity Readings to Be Unreliable. How Overheating Causes Sulphation.

Buckling.-How Overdischarge Causes Buckling. How Continued Operation with Battery in a Discharged Condition Causes Buckling. I-low Charging at High Rates Causes Buckling, How Non-Uniform Distribution of Current Over the Plates Causes Buckling. How Defective Grid Alloy Causes Buckling.

Shedding, or Loss of Active Material.-- Normal Shedding. How Excessive Charging Rate, or Overcharging Causes Shedding. How Charging Sulphated Plates at Too High a Rate Causes Shedding. How Charging Only a Portion of the Plate Causes Shedding. How Freezing Causes Shedding. How Overdischarge Causes Loose Active Material. How Buckling Causes Loose Active Material.

Impurities.-- Impurities Which Cause Only Self-Discharge. Impurities Which Attack the Plates. How to Remove Impurities. Corroded Grids.-How Impurities Cause Corroded Grids. How Sulphation Causes Corroded Grids. How High Temperatures Cause Corroded Grids. How High Specific Gravity Causes Corroded Grids. How Age Causes Corroded Grids.

Negatives.-- How Age and Heat Cause Granulated Negatives. Heating of Charged Negatives When Exposed to the Air. Negatives with Very Hard Active Material. Bulged Negatives. Negatives with Soft, Mushy, Active Material. Negatives with Rough Surfaces. Blistered Negatives.

Positives.-- Frozen Positives. Rotten, Disintegrated Positives. Buckled Positives. Positives Which Have Lost Considerable Active Material. Positives with Soft Active Material. Positives with Hard, Shiny Active Material. Plates Which Have Been Charged in the Wrong Direction.

Separator Troubles.-- Separators Not Properly Expanded Before Installation. Improperly Treated Separators. Rotten and Carbonized Separators. Separators with Clogged Pores. Separators with Edges Chiseled Off.

Jar Troubles.-- Jars Damaged by Rough Handling. Jars Damaged by Battery Being Loose. Jars Damaged by Weights Placed on Top of Battery. Jars Damaged by Freezing of Electrolyte. Jars Damaged by Improperly Trimmed Plate Groups. Improperly Made Jars. Jars Damaged by Explosions in Cell.

Battery Case Troubles.-- Ends of Case Bulged Out. Rotted Case.

Troubles with Connectors and Terminals.--Corroded and Loose Connectors and Terminals.

Electrolyte Troubles.-- Low Gravity. High Gravity. Low Level. High Level. Specific Gravity Does Not Rise During Charge. "Milky" Electrolyte. Foaming of Electrolyte.

General Battery Troubles.-- Open Circuits. Battery Discharged. Dead Cells. Battery Will Not Charge. Loss of Capacity. Loss of Charge in an Idle Battery.

11. Shop Equipment

List of Tools and Equipment Required by Repair Shop. Equipment Needed for Opening Batteries. Equipment for Lead Burning. Equipment for General Work on Cell Connectors and Terminals. Equipment for Work on Cases. Tools and Equipment for General Work. Stock. Special Tools. Charging Equipment. Wiring Diagrams for Charging Resistances and Charging Circuits. Motor-Generator Sets. Suggestions on Care of Motor-Generator Sets. Operating the Charging Circuits. Constant Current Charging. Constant Potential Charging. The Tungar Rectifier. Principle of Operation of Tungar Rectifier. The Two Ampere Tungar. The One Battery Tungar. The Two. Battery Tungar. The Four Battery Tungar. The Ten Battery Tangar. The Twenty Battery Tungar. Table of Tungar Rectifiers. Installation and Operation of Tungar Rectifier. The Mercury Are Rectifier. Mechanical Rectifiers. The Stahl Rectifier. Other Charging Equipment. The Charging Bench. Illustrations and Working Drawings of Charging Benches. Illustrations and Working Drawings of Work Benches. Illustrations and Working Drawings of Sink and Wash Tanks. Lead Burning Outfits. Equipment for Handling Sealing Compound. Shelving and Racks. Working Drawings of Receiving Racks, Racks for Repaired Batteries, Racks for New Batteries, Racks for Rental Batteries, Racks for Batteries in Dry Storage, Racks for Batteries in "Wet" Storage. Working Drawings of Stock Bins. Working Drawings for Battery Steamer Bench. Description of Battery Steamer. Plate Burning Rack. Battery Terminal Tongs. Lead Burning Collars. Post Builders. Moulds for Casting Lead Parts. Link Combination Mould. Cell Connector Mould. Production Type Strap Mould. Screw Mould. Battery Turntable. Separator Cutter. Plate Press. Battery Carrier. Battery Truck. Cadmium Test Set and How to Make the Test. Paraffine Dip Pot. Wooden Boxes for Battery Parts. Acid Car boys. Drawing Acid from Carboys. Shop Layouts. Floor Grating. Seven Architects' Drawings of Shop Layouts. The Shop Floor. Shop Light.

12. General Shop Instructions

Complete instructions for giving a bench charge. Instructions for Burning Cell Connectors and Terminals. Burning Plates to Strap and Posts. Post Building. Extending Plate Lugs. Moulding Lead Parts. Handling and Mixing Acid. Putting New Batteries Into Service (Exide, Vesta, Philadelphia, Willard, Westinghouse, Prest-O-Lite). Installing Battery on Car. Wet and Dry Storage of Batteries. Age Codes (Exide, Philadelphia, Prest-O-Lite, Titan, U.S.L., Vesta, Westinghouse, Willard). Rental Batteries. Terminals for Rental Batteries. Marking Chapter Page Rental Batteries. Keeping a Record of Rental Batteries. General Rental Policy. Radio Batteries. Principles of Audion Bulb for Radio. Vesta Radio Batteries. Westinghouse Radio Batteries. Willard Radio Batteries. Universal Radio Batteries. Exide Radio Batteries. Philadelphia Radio Batteries. U.S.L. Radio Batteries. Prest-O-Lite Radio Batteries. "Dry" Storage Batteries. Discharge Tests. 15 Seconds High Rate Discharge Test. 20 Minutes Starting Ability Discharge Test. "Cycling" Discharge Tests. Discharge Apparatus. Packing Batteries for Shipping. Safety Precautions for the Repairman. Testing the Electrical System of a Car. Complete Rules and Instructions for Quickly Testing, Starting and Lighting System to Protect Battery. Adjusting Generator Outputs. How and When to Adjust Charging Rate. Re-insulating the Battery. Testing and Filling Service. Service Records. Illustrations of Repair Service Record Card. Rental Battery Stock Card.

13. Business Methods

Purchasing Methods. Stock Records. The Use and Abuse of Credit. Proper Bookkeeping Records. Daily Exhibit Record. Statistical and Comparative Record.

14. What'S Wrong With The Battery?

"Service." Calling and Delivering Repaired Batteries. How to Diagnose Batteries That Come In. Tests on Incoming Batteries. General Inspection of Incoming Batteries. Operation Tests for Incoming Batteries. Battery Trouble Charts. Causes of Low Gravity or Low Voltage. Causes of Unequal Gravity Readings. Causes of High Gravity. Causes of Low Electrolyte. How to Determine When Battery May Be Left on Car. How to Determine When Battery Must Be Removed from Car. How to Determine When It Is Unnecessary to Open a Battery. How to Determine When Battery Must Be Opened.

15. Rebuilding The Battery

How to Open a Battery.-- Cleaning Outside of Battery Before Opening. Drilling and Removing Connectors and Terminals. Removing the Sealing Compound by Steam, Hot Water, Hot Putty Knife, Lead Burning Flame, and Gasoline Torch. Lifting Plates Out of Jars. Draining Plates. Removing Covers. Scraping Sealing Compound from the Covers. Scraping Sealing Compound from Inside of Jars.

What Must Be Done with the Opened Battery?-- Making a Preliminary Examination of Plates. When to Put in New Plates. When Old Plates May Be Used Again. What to Do with the Separators. Find the Cause of Every Trouble. Eliminating "Shorts." Preliminary Charge After Eliminating Shorts. Washing and Pressing Negatives. Washing Positives. Burning on New Plates. Testing Jars for Cracks and Holes. Removing Defective Jars. Repairing the Case.

Reassembling the Elements.-- Putting in Now Separators. Putting Elements Into Jars. Filling Jars with Electrolyte. Putting Chapter Page on the Covers. Sealing the Covers. Burning on the Connectors and Terminals. Marking the Repaired Battery. Cleaning and Painting the Case. Charging the Rebuilt Battery. Testing.

16. Special Instructions

Exide Batteries.-- Types. Type Numbers. Methods of Holding Jars in Case. Opening Exide Batteries. Work on Plates, Separators, Jars, and Case. Putting Plates in Jars. Filling Jars with Electrolyte. Sealing Covers. Putting Cells in Case. Burning on the Cell Connectors. Charging After Repairing. Tables of Exide Batteries.

U.S.L. Batteries.-- Old and New. U.S.L. Covers. Special Repair Instructions. Tables of U.S.L. Batteries.

Prest-O-Lite Batteries.-- Old and New Prest-O-Lite Cover Constructions. The "Peened" Post Seal. Special Tools for Work on Prest-O-Lite Batteries. The Peening Press. Removing Covers. Rebuilding Posts. Locking, or "Peening" the Posts. Precautions in Post Locking Operations. Tables of Prest-0-Lite Batteries.

Philadelphia Diamond Grid Batteries.-- Old and New Types. The Philadelphia "Rubber-Lockt" Cover Seal. Philadelphia Rubber Case Batteries. The Philadelphia Separator. Special Repair Instructions.

Eveready Batteries.-- Why the Eveready Batteries Are Called "Non-Sulphating" Batteries. Description of Parts of Eveready Battery. Special Repair Instructions.

Vesta Batteries.-- Old and New Vesta Isolators. The Vesta Type "D" Battery. The Vesta Type "DJ" Battery. Vesta Separators. The Vesta Post Seal. Special Repair Instructions for Old and New Isolators and Post Seal.

Westinghouse Batteries.-- The Westinghouse Post Seal. Westinghouse Plates. Types of Westinghouse Batteries. Type "A" Batteries. Type "B" Batteries. Type "C" Batteries. Type "E" Batteries. Type "H" Batteries. Type "J" Batteries. Type "0" Batteries. Type "F" Batteries.

Willard Batteries.-- Double and Single Cover Batteries. Batteries with Sealing Compound Post Seal. Batteries with Lead Inserts in Cover Post Holes. Batteries with Rubber Casket Post Seal. Special Repair Instructions for Work on the Different Types of Post Seal Constructions. Willard Threaded Rubber Separators.

Universal Batteries.-- Types. Construction Features. Putting New Universal Batteries Into Service.

Titan Batteries.-- The Titan Grid. The Titan Post Seal.

17. Farm Lighting Batteries

Comparison of Operating Conditions of Farm Lighting Batteries with Automobile Batteries. Jars for Farm Lighting Batteries. Separators. Electrolyte. Charging Equipment. Relation of the Automobile Battery Man to the Farm Lighting Plant. Rules Governing the Selection of a Farm Lighting Plant. Location and Wiring of Farm Lighting Plant. Installation. Care of Plant in Service. Care of Battery. Charging Farm Lighting Batteries. Rules Governing Discharging of Farm Lighting Batteries. Troubles Found in Farm Lighting Batteries. Inspection and Tests on Farm Lighting Batteries. Description of Prest-O-Lite Farm Lighting Battery. Rebuilding Prest-O-Lite Farm Lighting Batteries. Description of Exide Farm Lighting Batteries. The Delco-Light Battery. Rebuilding and Repairing Exide Farm Lighting Batteries. Westinghouse Farm Lighting Batteries. Willard Farm Lighting Batteries.

Definitions

Condensed Dictionary of Words and Terms Used in Battery Work.

General Index

A Visit To The Factory

Photographs showing factory processes.

BUYERS' INDEX. (Omitted.)

For the Convenience of Our Readers We Have Prepared a List of Companies from Whom Battery Shop Equipment May Be Obtained.

ADVERTISEMENTS (Omitted. Outdated; high bandwidth)

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Section I ---------

Working Principles, Manufacture, Maintenance, Diseases, and Remedies

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The Automobile Storage Battery

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Chapter 1. Introductory.

Gasoline and electricity have made possible the modern automobile. Each has its work to do in the operation of the car, and if either fails to perform its duties, the car cannot move. The action of the gasoline, and the mechanisms that control it are comparatively simple, and easily understood, because gasoline is something definite which we can see and feel, and which can be weighed, or measured in gallons. Electricity, on the other hand, is invisible, cannot be poured into cans or tanks, has no odor, and, therefore, nobody knows just what it is. We can only study the effects of electricity, and the wires, coils, and similar apparatus in which it is present. It is for this reason that an air of mystery surrounds electrical things, especially to the man who has not made a special study of the subject.

Without electricity, there would be no gasoline engine, because gasoline itself cannot cause the engine to operate. It is only when the electrical spark explodes or "ignites" the mixture of gasoline and air which has been drawn into the engine cylinders that the engine develops power. Thus an electrical ignition system has always been an essential part of every gasoline automobile.

The first step in the use of electricity on the automobile, in addition to the ignition system, consisted in the installation of an electric lighting system to replace the inconvenient oil or gas lamps which were satisfactory as far as the light they gave was concerned, but which had the disadvantage of requiring the driver to leave his seat, and light each lamp separately, often in a strong wind or rain which consumed many matches, time, and frequently spoiled his temper for the remainder of the evening. Electric lamps have none of these disadvantages. They can be controlled from the driver's seat, can be turned on or off by merely turning or pushing a switch-button, are not affected by wind or rain, do not smoke up the lenses, and do not send a stream of unpleasant odors back to the passengers.

The apparatus used to supply the electricity for the lamps consisted of a generator, or a "storage" battery, or both. The generator alone had the disadvantage that the lamps could be used only while the engine was running. The battery, on the other hand, furnished light at all times, but had to be removed from the car frequently, and "charged." With both the generator and battery, the lights could be turned on whether the engine was running or not, and, furthermore, it was no longer necessary to remove the battery to "charge," or put new life into it. With a generator and storage battery, moreover, a reliable source of electricity for ignition was provided, and so we find dry batteries and magnetos being discarded in a great many automobiles and "battery ignition" systems substituted.

The development of electric lighting systems increased the popularity of the automobile, but the motor car still had a great drawback-cranking. Owing to the peculiar features of a gasoline engine, it must first be put in motion by some external power before it will begin to operate under its own power. This made it necessary for the driver to "crank" the engine, or start it moving, by means of a handle attached to the engine shaft. Cranking a large engine is difficult, especially if it is cold, and often results in tired muscles, and soiled clothes and tempers. It also made it impossible for the average woman to drive a car because she did not have the strength necessary to "crank" an engine.

The next step in the perfection of the automobile was naturally the development of an automatic device to crank the engine, and thus make the driving of a car a pleasure rather than a task. We find, therefore, that in 1912, "self-starters" began to be used. These were not all electrical, some used tanks of compressed air, others acetylene, and various mechanical devices, such as the spring starters. The electrical starters, however, proved their superiority immediately, and filled such a long felt want that all the various makes of automobiles now have electric starters. The present day motor car, therefore, uses gasoline for the engine only, but uses electricity for ignition, starting, lighting, for the horn, cigar lighters, hand warmers on the steering wheel, gasoline vaporizers, and even for shifting speed changing gears, and for the brakes.

On any car that uses an electric lighting and starting system, there are two sources of electricity, the generator and the battery, These must furnish the power for the starting, or "cranking" motor, the ignition, the lights, the horn, and the other devices. The demands made upon the generator are comparatively light and simple, and no severe work is done by it. The battery, on the other hand is called upon to give a much more severe service, that of furnishing the power to crank the engine. It must also perform all the duties of the generator when the engine is not running, since a generator must be in motion in order to produce electricity.

A generator is made of iron, copper, carbon, and insulation. These are all solid substances which can easily be built in any size or shape, and which undergo very little change as parts of the generator. The battery is made mainly of lead, lead compounds, water and sulphuric acid. Here we have liquids as well as solids, which produce electricity by changes in their composition, resulting in complicated chemical as well as electrical actions.

[Fig. 1 The Battery]

The battery is, because of its construction and performance, a much abused, neglected piece of apparatus which is but partly understood, even by many electrical experts, for to understand it thoroughly requires a study of chemistry as well as of electricity. Knowledge of the construction and action of a storage battery is not enough to make anyone an expert battery man. He must also know how to regulate the operating conditions so as to obtain the best service from the battery, and he must be able to make complete repairs on any battery no matter what its condition may be.

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Chapter 2. Batteries In General

There are two ways of "generating" electricity on the car: 1. Magnetically, 2. Chemically. The first method is that used in a generator, in which wires are rotated in a "field" in which magnetic forces act. The second method is that of the battery, and the one in which we are now interested.

If two unlike metals or conducting substances are placed in a liquid which causes a greater chemical change in one of the substances than in the other, an electrical pressure, or "electromotive" force is caused to exist between the two metals or conducting substances. The greater the difference in the chemical action on the substances, the greater will be the electrical pressure, and if the substances are connected together outside of the liquid by a wire or other conductor of electricity, an electric current will flow through the path or "circuit" consisting of the liquid, the two substances which are immersed in the liquid, and the external wire or conductor.

As the current flows through the combination of the liquid, and the substances immersed in it, which is called a voltaic "cell," one or both of the substances undergo chemical changes which continue until one of the substances is entirely changed. These chemical changes produce the electrical pressure which causes the current to flow, and the flow will continue until one or both of the substances are changed entirely. This change due to the chemical action may result in the formation of gases, or of solid compounds. If gases are formed they escape and are lost. If solids are formed, no material is actually lost.

Assuming that one of the conducting substances, or "electrodes," which are immersed in the liquid has been acted upon by the liquid, or "electrolyte," until no further chemical action can take place, our voltaic cell will no longer be capable of causing a flow of electricity. If none of the substances resulting from the original chemical action have been lost as gases, it may be possible to reverse the entire set of operations which have taken place. That is, suppose we now send a current through the cell from an outside source of electricity, in a direction opposite to that in which the current produced by the chemical action between the electrodes and electrolyte flowed. If this current now produces chemical actions between electrodes and electrolyte which are the reverse of those which occurred originally, so that finally we have the electrodes and electrolyte brought back to their original composition and condition, we have the cell just as it was before we used it for the production of an electrical pressure. The cell can now again be used as a source of electricity as long as the electrolyte acts upon the electrodes, or until it is "discharged" and incapable of any further production of electrical pressure. Sending a current through a discharged cell, so as to reverse the chemical actions which brought about the discharged conditions, is called "charging" the cell.

[Fig. 2 A complete cell; Negative group; Positive group]

Cells in which an electrical pressure is produced as soon as the electrodes are immersed in the electrolyte are called it "primary" Cells. In these cells it is often impossible, and always unsatisfactory to reverse the chemical action as explained above. Cells whose chemical actions are reversible are called "storage" or "secondary" cells. In the "storage" cells used today, a current must first be sent through the cell in order to cause the chemical changes which result in putting the electrodes and electrolyte, in such a condition that they will be capable of producing an electrical pressure when the chemical changes caused by the current are complete. The cell now possesses all the characteristics of a primary cell, and may be used as a source of electricity until "discharged." It may then be "charged" again, and so on, the chemical action in one case causing a flow of current, and a reversed flow of current causing reversed chemical actions.

We see from the above that the "storage" battery does not "store" electricity at all, but changes chemical into electrical energy when "discharging," and changes electrical into chemical energy when "charging," the two actions being entirely reversible. The idea of "storing" electricity comes from the fact that if we send a current of electricity through the cell for a certain length of time, we can at a later time draw a current from the cell for almost the same length of time.

[Fig. 3 Complete Element]

Fig. 3. A complete element, consisting of a positive and negative group of plates and separators ready for placing in the hard rubber jars.

Three things are therefore required in a storage cell, the liquid or "electrolyte" and two unlike substances or electrodes, through which a current of electricity can pass and which are acted upon by the electrolyte with a chemical action that is greater for one substance than the other. In the storage cell used on the automobile today for starting and lighting, the electrodes are lead and peroxide of lead, and the electrolyte is a mixture of sulphuric acid and water. The peroxide of lead electrode is the one upon which the electrolyte has the greater chemical effect, and it is called the positive or "+" electrode, because when the battery is sending a. current through an external circuit, the current flows from this electrode through the external circuit, and back to the lead electrode, which is called the negative, or electrode.

When starting and lighting systems were adopted in 1912, storage batteries had been used for many years in electric power stations. These were, however, large and heavy, and many difficult problems of design had to be solved in order to produce a battery capable of performing the work of cranking the engine, and yet be portable, light, and small enough to occupy only a very limited space on the automobile. As a result of these conditions governing the design, the starting and lighting battery of today is in reality "the giant that lives in a box." The Electric Storage Battery Company estimates that one of its types of batteries, which measures only 12-5/8 inches long, 7-3/8 wide, and 9-1/8 high, and weighs only 63-1/2 pounds, can deliver enough energy to raise itself to a height of 6 miles straight up in the air. It must be able to do its work quickly at all times, and in all sorts of weather, with temperatures ranging from below 0° to 100° Fahrenheit, or even higher.

The starting and lighting battery has therefore been designed to withstand severe operating conditions. Looking at such a battery on a car we see a small wooden box in which are placed three or more "cells," see Fig. 1. Each "cell" has a hard, black rubber top through which two posts of lead project. Bars of lead connect the posts of one cell to those of the next. To one of the posts of each end cell is connected a cable which leads into the car, and through which the current leaves or enters the battery. At the center of each cell is a removable rubber plug covering an opening through which communication is established with the inside of the cell for the purpose of pouring in water, removing some of the electrolyte to determine the condition of the battery, or to allow gases formed within the cell to escape. Looking down through this opening we can see the things needed to form a storage battery: the electrolyte, and the electrodes or "plates" as they are called. If we should remove the lead bars connecting one cell to another, and take off the black cover, we should find that the posts which project out of the cells are attached to the plates which are broad and flat, and separated by thin pieces of wood or rubber., If we lift out the plates we find that they are connected alternately to the two lead posts, and that the two outside ones have a gray color. If we pull the plates out from each Other, we find that the plates next to the two outside ones, and all other plates connected to the same lead post as these have a chocolate-brown color. If we remove the jar of the cell, we find that it is made of hard rubber. Pouring out the electrolyte we find several ridges which hold the plates off the bottom of the jar. The pockets formed by these ridges may contain some soft, muddy substance. Thus we have exposed all the elements of a cell, posts, plates, "separators," and electrolyte. The gray colored plates are attached to the "negative" battery post, while the chocolate-brown colored ones are connected to the "positive" battery post. Examination will show that each of the plates consists of a skeleton metallic framework which is filled with the brown or gray substances. This construction is used to decrease the weight of the battery. The gray filler material is pure lead in a condition called "spongy lead." The chocolate-brown filler substance is peroxide of lead.

We have found nothing but two sets of plates--one of pure lead, the other of peroxide of lead, and the electrolyte of sulphuric acid and water. These produce the heavy current necessary to crank the engine. How this is done, and what the chemical actions within the cell are, are described in Chapter 4.

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Chapter 3. Manufacture Of Storage Batteries. ---------------------------------

To supply the great number of batteries needed for gasoline automobiles, large companies have been formed. Each company has its special and secret processes which it will not reveal to the public. Only a few companies, however, supply batteries in any considerable quantities, the great majority of cars being supplied with batteries made by not more than five or six manufacturers. This greatly reduces the number of possible different designs in general use today.

The design and dimensions of batteries vary considerably, but the general constructions are similar. The special processes of the manufacturers are of no special interest to the repairman, and only a general description will be given here.

A starting and lighting battery consists of the following principal parts:

1. Plates 2. Separators 3. Electrolyte 4. Jars 5. Covers 6. Cell Connectors and Terminals 7. Case Plates

Of the two general types of battery plates, Faure and Plante, the Faure, or pasted type, is universally used on automobiles. In the manufacture of pasted plates there are several steps which we shall describe in the order in which they are carried out.

Casting the Grid. The grid is the skeleton of the plate. It performs the double function of supporting the mechanically weak active material and of conducting the current. It is made of a lead antimony alloy which is melted and poured into a mould. Pure lead is too soft and too easily attacked by the electrolyte, and antimony is added to give stiffness, and resistance to the action of the electrolyte in the cell. The amount of antimony used varies in different makes but probably averages 8 to 10%.

The casting process requires considerable skill, the proper composition of the metal and the temperature of both metal and moulds being of great importance in securing perfect grids, which are free from blowholes, and which have a uniform structure and composition. Some manufacturers cast two grids simultaneously in each mould, the two plates being joined to each other along the bottom edge.

Trimming the Grids. When the castings have cooled, they are removed from the moulds and passed to a press or trimming machine which trims off the casting gate and the rough edges. The grids are given a rigid inspection, those having shrunken or missing ribs or other defects being rejected. The grids are now ready for pasting.

[Fig 4. Grid, Trimmed, and Ready for Pasting]

Fig. 4 shows a grid ready for pasting. The heavy lug at one upper corner is the conducting lug, for carrying the current to the strap, Fig. 5, into which the lugs are burned when the battery is assembled. The straps are provided with posts, to which the intercell connectors and terminal connectors are attached. The vertical ribs of the grids extend through the plate, providing mechanical strength and conductivity, while the small horizontal ribs are at the surface and in staggered relation on opposite faces. Both the outside frames and the vertical ribs are reinforced near the lug, where the greatest amount of current must be carried.

The rectangular arrangement of ribs, as shown in Fig. 4, is most generally used, although, there are other arrangements such as the Philadelphia "Diamond" grid in which the ribs form acute angles, giving diamond shaped openings, as shown in Fig. 6.

Pastes. There are many formulas for the pastes, which are later converted into active material, and each is considered a trade secret by the manufacturer using it. The basis of all, however, is oxide of lead, either Red Lead (Pb30 4), Litharge (PbO), or a mixture of the two, made into a paste with a liquid, such as dilute sulphuric acid. The object of mixing the oxides with the liquid is to form a paste of the proper consistency for application to the grids, and at the same time introduce the proper amount of binding, or setting agent which will give porosity, and which will bind together the active material, especially in the positive plate. Red lead usually predominates in the positive paste, and litharge in the negative, as this combination requires the least energy in forming the oxides to active material.

[Fig. 5 Plate Straps and Posts]

The oxides of lead used in preparing the pastes which are applied to the grids are powders, and in their dry condition could not be applied to the grids, as they would fall out. Mixing them with a liquid to make a paste gives them greater coherence and enables them to be applied to the grids. Sulphuric acid puts the oxides in the desired pasty condition, but has the disadvantage of causing a chemical action to take place which changes a considerable portion of the oxides to lead sulphate, the presence of which makes the paste stiff and impossible to apply to the grids. When acid is used, it is therefore necessary to work fast after the oxides are mixed with sulphuric acid to form the paste.

In addition to the lead oxides, the pastes may contain some binding material such as ammonium or magnesium sulphate, which tends to bind the particles of the active material together. The paste used for the negatives may contain lamp black to give porosity.

Applying the Paste. After the oxides are mixed to a paste they are applied to the grids. This is done either by hand, or by machine In the hand pasting process, the pastes are applied from each face of the grid by means of a wooden paddle or trowel, and are smoothed off flush with the surface of the ribs of the grid. This work is done quickly in order that the pastes may not stiffen before they are applied.

U. S. L. plates are pasted in a machine which applies the paste to the grid, subjecting it at the same time to a pressure which forces it thoroughly into the grid, and packs it in a dense mass.

Drying the Paste. The freshly pasted plates are now allowed to dry in the air, or are dried by blowing air over them. In any case, the pastes set to a hard mass, in which condition the pastes adhere firmly to the grids. The plates may then be handled without a loss of paste from the grids.

[Fig. 6 Philadelphia diamond grid]

Forming. The next step is to change the paste of oxides into the active materials which make a cell operative. This is called "forming" and is really nothing but a prolonged charge, requiring several days. In some factories the plates are mounted in tanks, positive and negative plates alternating as in a cell. The positives are all connected together in one group and the negatives in another, and current passed through just as in charging a battery. In other factories the positives and negatives are formed in separate tanks against "dummy" electrodes.

The passing of the current slowly changes the mixtures of lead oxide and lead sulphate, forming brown peroxide of lead (PbO2), on the positive plate and gray spongy metallic lead on the negative. The formation by the current of lead peroxide and spongy lead on the positive and negative plates respectively would take place if the composition of the two pastes were identical. The difference in the composition of the paste for positive and negative plates is for the purpose of securing the properties of porosity and physical condition best suited to each.

[Fig. 7 Formed plate, ready to be burned to plate connecting strap]

When the forming process is complete, the plates are washed and dried, and are then ready for use in the battery. If the grids of two plates have been cast together, as is done by some manufacturers, these are now cut apart, and the lugs cut to the proper height. The next step is to roll, or press the negatives after they are removed from the forming bath so as to bring the negative paste, which has become roughened by gassing that occurred during the forming process, flush with the surface of the ribs of the grid. A sufficient amount of sulphate is left in the plates to bind together the active material. Without this sulphate the positive paste would simply be a powder and when dry would fall out of the grids like dry dust. Fig. 7 shows a formed plate ready to be burned to the strap.

Separators

In batteries used both for starting and for lighting, separators made of specially treated wood are largely used. See Fig. 8. The Willard Company has adopted an insulator made of a rubber fabric pierced by thousands of cotton threads, each thread being as long as the separator is thick. The electrolyte is carried through these threads from one side of the separator to the other by capillary action, the great number of these threads insuring the rapid diffusion of electrolyte which is necessary in batteries which are subjected to the heavy discharge current required in starting.

In batteries used for lighting or ignition, sheets of rubber in which numerous holes have been drilled are also used, these holes permitting diffusion to take place rapidly enough to perform the required service satisfactorily, since the currents involved are much smaller than in starting motor service.

[Fig. 8]

Fig 8. A Pile of Prepared Wooden Seperators Ready to be Put Between the Positive and Negative Plates to Form the Complete Element.

For the wooden separators, porous wood, such as Port Orford cedar, basswood, cypress, or cedar is used. Other woods such as redwood and cherry are also used. The question is often asked "which wood makes the best separators?" This is difficult to answer because the method of treating the wood is just as important as is the kind of wood. The wood for the separators is cut into strips of the correct thickness. These strips are passed through a grooving machine which cuts the grooves in one side, leaving the other side smooth. The strips are next sawed to the correct size, and are then boiled in a warm alkaline solution for about 24 hours to neutralize any organic acid, such as acetic acid, which the wood naturally contains. Such acids would cause unsatisfactory battery action and damage to the battery.

The Vesta separator, or "impregnated mat," is treated in a bath of Barium salts which form compounds with the wood and which are said to make the separators strong and acid-resisting.

[Fig. 9 Philco slotted retainer]

Some batteries use a double separator, one of which is the wooden separator, while the other consists of a thin sheet of hard rubber containing many fine perforations. This rubber sheet is placed between the positive plate and the wooden separator. A recent development in the use of an auxiliary rubber separator is the Philco slotted retainer which is placed between the separators and the positives in Philadelphia Diamond Grid Batteries. Some Exide batteries also use slotted rubber separators. The Philco slotted retainer consists of a thin sheet of slotted hard rubber as shown in Fig. 9. The purpose of the retainer is to hold the positive active material in place and prevent the shedding which usually occurs. The slots in the retainer are so numerous that they allow the free passage of electrolyte, but each slot is made very narrow so as to hold the active material in the plates.

Electrolyte

Little need be said here about the electrolyte, since a full description is given elsewhere. See page 222. Acid is received by the battery manufacturer in concentrated form. Its specific gravity is then 1.835. The acid commonly used is made by the "contact" process, in which sulphur dioxide is oxidized to sulphur trioxide, and then, with the addition of water, changed to sulphuric acid. The concentrated acid is diluted with distilled water to the proper specific gravity.

Jars

The jars which contain the plates, separators, and electrolyte are made of a tough, hard rubber compound. They are made either by the moulding process, or by wrapping sheets of rubber compound around metal mandrels. In either case the jar is subsequently vulcanized by careful heating at the correct temperature.

The battery manufacturers do not, as a rule, make their own jars, but have them made by the rubber companies who give the jars a high voltage test to detect any flaws, holes, or cracks which would subsequently cause a leak. The jars as received at the battery maker's factory are ready for use.

Across the bottom of the jar are several stiff ribs which extend up into the jar so as to provide a substantial support for the plates, and at the same time form several pockets below the plates in which the sediment resulting from shedding of active material from the plates accumulates.

Covers

No part of a battery is of greater importance than the hard rubber cell covers, from the viewpoint of the repairman as well as the manufacturer. The repairman is concerned chiefly with the methods of sealing the battery, and no part of his work requires greater skill than the work on the covers. The manufacturers have developed special constructions, their aims being to design the cover so as to facilitate the escape of gas which accumulates in the upper part of a cell during charge, to provide space for expansion of the electrolyte as it becomes heated, to simplify inspection and filling with pure water, to make leak proof joints between the cover and the jar and between the cover and the lead posts which project through it, and to simplify the work of making repairs.

Single and Double Covers. Modern types of batteries have a single piece cover, the edges of which are made so as to form a slot or channel with the inside of the jar, into which is poured sealing compound to form a leak proof joint. This construction is illustrated. in Exide, Fig. 1.5; Vesta, Fig. 264; Philadelphia Diamond Grid, Fig. 256; U. S. L., Figs. 11 and 244; and Prest-0-Lite, Fig. 247, batteries. Exide batteries are also made with a double flange cover, in which the top of the jar fits between the two flanges. In single covers, a comparatively small amount of sealing compound is used, and repair work is greatly simplified.

In the Eveready battery, Fig. 262, compound is poured over the entire cover instead of around the edges. This method requires a considerable amount of sealing compound.

The use of double covers is not as common as it was some years ago. This construction makes use of two flat pieces of hard rubber. In such batteries a considerable amount of sealing compound is used. This compound is poured on top of the lower cover to seal the battery, the top cover serving to cover up the compound and brace the posts. Fig. 10 illustrates this construction.

[Fig. 10 Cross-section of Gould double cover battery]

Sealing Around the Posts. Much variety is shown in the methods used to secure a leak proof joint between the posts and the cover. Several methods are used. One of these uses the sealing compound to make a tight joint. Another has lead bushings which are screwed up into the cover or moulded in the cover, the bushings being burned together with the post and cell connector. Another method has a threaded post, and uses a lead alloy nut with a rubber washer to make a tight joint. Still another method forces a lead collar down over the post, and presses the cover down on a soft rubber gasket.

Using Sealing Compound. Some of the batteries which use sealing compound to make a tight joint between the cover and the post have a hard rubber bushing shrunk over the post. This construction is used in Gould batteries, as shown in Fig. 10, and in the old Willard double cover batteries. The rubber bushing is grooved horizontally to increase the length of the sealing surface.

[Fig. 11 U.S.L. cover]

Other batteries that use sealing compound around the posts have grooves or "petticoats" cut directly in the post and have a well around the post into which the sealing compound is poured. This is the construction used in the old Philadelphia Diamond Grid battery, as shown in Fig. 254.

Using Lead Bushings. U. S. L. batteries have a flanged lead bushing which is moulded directly into the cover, as shown in Fig. 11. In assembling the battery, the cover is placed over the post, and the cell connector is burned to both post and bushing.

[Fig. 12 Lead bushing screwed into cover]

In older type U. S. L. batteries a bushing was screwed up through the cover, and then burned to the post and cell connector.

An old type Prest-O-Lite battery used a lead bushing which screwed up through the cover similarly to the U. S. L. batteries. Fig. 12 illustrates this construction. The SJWN and SJRN Willard Batteries used a lead insert. See page 424.

The modern Vesta batteries use a soft rubber gasket under the cover, and force a lead collar over the post, which pushes the cover down on the gasket. The lead collar and post "freeze" together and make an acid proof joint. See page 413. The Westinghouse battery uses a three part seal consisting of a lead washer which is placed around the post, a U shaped, soft gum washer which is placed between the post and cover, and a tapered lead sleeve, which presses the washer against the post and the cover. See page 417.

[Fig. 13 Cross section of old type Willard battery]

The Prest-O-Lite Peened Post Seal. All Prest-O-Lite batteries designated as types WHN, RHN, BHN and JFN, have a single moulded cover which is locked directly on to the posts. This is done by forcing a solid ring of lead from a portion of the post down into a chamfer in the top of the cover. This construction is illustrated in Fig. 247.

Batteries Using Sealing Nuts. The Exide batteries have threaded posts. A rubber gasket is placed under the cover on a shoulder on the post. The nut is then turned down on the post to force the cover on the gasket. This construction is illustrated in Fig. 239. The Titan battery uses a somewhat similar seal, as shown in Fig. 293.

Some of the older Willard batteries have a chamfer or groove in the under, side of the cover. The posts have a ring of lead in the base which fits up into the groove in the cover to make a tight joint. This is illustrated in Fig. 13. The later Willard constructions, using a rubber gasket seal and a lead cover insert, are illustrated in Figs. 278 and 287.

Filling Tube or Vent Tube Construction. Quite a number of designs have been developed in the construction of the filling or vent tube. In double covers, the tube is sometimes a separate part which is screwed into the lower cover. In other batteries using double covers, the tube is an integral part of the cover, as shown in Fig. 10. In all single covers, the tube is moulded integral with the cover.

[Fig. 14a Vent hold in U.S.L. battery]

Several devices have been developed to make it impossible to overfill batteries. This has been done by the U. S. L. and Exide companies on older types of batteries, their constructions being described as follows:

In old U. S. L. batteries, a small auxiliary vent tube is drilled, as shown in Fig. 14. When filling to replace evaporation, this vent tube prevents overfilling.

[Fig. 14b Filling U.S.L. battery]

A finger is placed over the auxiliary vent tube shown in Fig. 14. The water is then poured in through the filling or vent tube. When the water reaches the bottom of the tube, the air imprisoned in the expansion chamber can no longer escape. Consequently the water can rise no higher in this chamber, but simply fills up the tube. Water is added till it reaches the top of the tube. The finger is then removed from the vent tube. This allows the air to escape from the expansion chamber. The water will therefore fall in the filling or vent tube, and rise slightly in the expansion chamber. The construction makes it impossible to overfill the battery, provided that the finger is held on the vent hole as directed.

[Fig. 14c Filling U.S.L. battery (old types)]

Figure 15 shows the Non-Flooding Vent and Filling Plug used in the older type Exide battery, and in the present type LXRV. The new Exide cover, which does not use the non-flooding feature, is also shown. The old construction is described as follows:

[Fig. 15a Sectional view of cover in older type Exide battery. Top view of cover and filling plug, plug removed]

[Fig. 15b Old and new Exide covers]

From the illustrations of the vent and filling plug, it will be seen that they provide both a vented stopper (vents F, G, H), and an automatic device for the preventing of overfilling and flooding. The amount of water that can be put into the cell is limited to the exact amount needed to replace that lost by evaporation. This is accomplished by means of the hard rubber valve (A) within the cell cover and with which the top of the vent plug (E) engages, as shown in the illustrations. The action of removing the plug (E) turns this valve (A), closing the air passage (BB), and forming an air tight chamber (C) in the top of the cell. When water is poured in, it cannot rise in this air space (C) so as to completely fill the cell. As soon as the proper level is reached, the water rises in the filling tube (D) and gives a positive indication that sufficient water has been added. Should, however, the filling be continued, the excess will be pure water only, not acid. On replacing the plug (E), valve (A) is automatically turned, opening the air passages (BB), leaving the air chamber (C) available for the expansion of the solution, which occurs when the battery is working.

Generally the filling or vent tube is so made that its lower end indicates the correct level of electrolyte above the plates, In adding water, the level of the electrolyte is brought up to the bottom of the filling tube. By looking down into the tube, it can be seen when the electrolyte reaches the bottom of the tube.

Vent Plugs, or Caps. Vent plugs, or caps, close up the filling or vent tubes in the covers. They are made of hard rubber, and either screw into or over the tubes, or are tightened by a full or partial turn, as is done in Exide batteries. In the caps are small holes which are so arranged that gases generated within the battery may escape, but acid spray cannot pass through these holes. It is of the utmost importance that the holes in the vent caps be kept open to allow the gases to escape.

Case

The wooden case in which the cells are placed is usually made of kiln dried white oak or hard maple. The wood is inspected carefully, and all pieces are rejected that are weather-checked, or contain worm-holes or knots. The wood is sawed into various thicknesses, and then cut to the proper lengths and widths. The wood is passed through other machines that cut in the dovetails, put the tongue on the bottom for the joints, stamp on the part number, drill the holes for the screws or bolts holding the handles, cut the grooves for the sealing compound, etc. The several pieces are then assembled and glued together. The finishing touches are then put on, these consisting of cutting the cases to the proper heights, sandpapering the boxes, etc. The cases are then inspected and are ready to be painted.

A more recent development in case construction is a one-piece hard rubber case, in which the jars and case are made in one piece, the cell compartments being formed by rubber partitions which form an integral part of the case. This construction is used in several makes of Radio "A" batteries, and to some extent in starting batteries.

[Fig. 16 Exide battery case]

Asphaltum paint is generally used for wooden cases, the bottoms and tops being given three, coats, and the sides, two. The number of coats of paint varies, of course, in the different factories. The handles are then put on by machinery, and the case, Fig. 16, is complete, and ready for assembling.

Assembling and Sealing

The first step in assembling a battery is to burn the positive and negative plates to their respective straps, Fig. 5, forming the positive and negative "groups", Fig. 2. This is done by arranging a set of plates and a strap in a suitable rack which holds them securely in proper position, and then melting together the top of the plate lugs and the portion of the strap into which they fit with a hot flame.

A positive and a negative group are now slipped together and the separators inserted. The grooved side of the wood separator is placed toward the positive plate and when perforated rubber sheets are used these go between the positive and the wood separator. The positive and negative "groups" assembled with the separators constitute the "element," Fig. 3.

Before the elements are placed in the jars they are carefully inspected to make sure that no separator has been left out. For this purpose the "Exide" elements are subjected to an electrical test which rings a bell if a separator is missing, this having been found more infallible than trusting to a man's eyes.

In some batteries, such as the Exide, Vesta, and Prest-O-Lite batteries, the cover is placed on the element and made fast before the elements are placed in the jars. In other batteries, such as the U. S. L. and Philadelphia batteries, the covers are put on after the elements are placed in the jars.

After the element is in the jar and the cover in position, sealing compound is applied hot so as to make a leak proof joint between jar and cover.

[Fig. 17 Inter-cell connector]

The completed cells are now assembled in the case and the cell connectors, Fig. 17, burned to the strap posts. After filling with electrolyte the battery is ready to receive its "initial charge," which may require from one day to a week. A low charging rate is used, since the plates are generally in a sulphated condition when assembled. The specific gravity is brought up to about 1.280 during this charge. Some makers now give the battery a short high rate discharge test (see page 266), to disclose any defects, and just before sending them out give a final charge. The batteries are often "cycled" after being assembled, this consisting in discharging and recharging the batteries several times to put the active material in the best working condition. If the batteries are to be shipped "wet," they are ready for shipping after the final charge and inspection. Batteries which are shipped "dry" need to have more work done upon them.

Preparing Batteries for Dry Shipment

There are three general methods of "dry" shipment. The first method consists of sending cases, plates, covers, separators, etc., separately, and assembling them in the service stations. Sometimes these parts are all placed together, as in a finished battery, but without the separators, the covers not being sealed, or the connectors and terminals welded to the posts. This is a sort of "knock-down" condition. The plates used are first fully charged and dried.

The second method consists of assembling a battery complete with plates, separators, and electrolyte, charging the battery, pouring out the electrolyte, rinsing with distilled water, pouring out the water and screwing the vent plugs down tight. The vent holes in these plugs are sealed to exclude air. The moisture left in the battery when the rinsing water was poured out cannot evaporate, and the separators are thus kept in a moistened condition.

The third method is the Willard "Bone Dry" method, and consists of assembling the battery complete with dry threaded rubber separators and dry plates, but without electrolyte. The holes in the vent plugs are not sealed, since there is no moisture in the battery. Batteries using wooden separators cannot be shipped "bone-dry," since wooden separators must be kept moist.

Terminal Connections

When the battery is on the car it is necessary to have some form of detachable connection to the car circuit and this is accomplished by means of "terminal connectors," Fig. 18, of which there are many types.

[Fig. 18 Battery terminal]

Many types of terminals are in two parts, one being permanently attached to the car circuit and the other mounted permanently on the battery by welding it to the terminal post, the two parts being detachably joined by means of a bolted connection.

In another type of terminal, the cable is soldered directly to the terminal which is lead burned to the cell post. In this construction there is very much less chance of corrosion taking place, and it is therefore a good design.

Homemade Batteries

The wisest thing for the battery shop owner to do is to get a contract as official service station for one of the well known makes of batteries. The manufacturers of this battery will stand behind the service station, giving it the benefits of its engineering, production, and advertising departments, and boost the service station's business, helping to make it a success.

Within the past year or so, however, some battery repairmen have conceived the idea that they do not need the backing of a well organized factory, and have decided to build up their own batteries. Some of them merely assemble batteries from parts bought from one or more manufacturers. If all the parts are made by the same company, they will fit together, and may make a serviceable battery. Often, however, parts made by several manufacturers are assembled in the same battery. Here is where trouble is apt to develop, because it is more than likely that jars may not fit well in the case; plates may not completely fill the jars, allowing too much acid space, with the results that specific gravity readings will not be reliable, and the plates may be overworked; plate posts may not fit the cover holes, and so on. If such a "fabricated" battery goes dead because of defective material, there is no factory back of the repairman to stand the loss.

If the repairman wishes to assemble batteries, he should be very careful to buy the parts from a reliable manufacturer, and he should be especially careful in buying separators, as improperly treated separators often develop acetic acid, which dissolves the lead of the plates very quickly and ruins the battery. Batteries made in this way are good for rental batteries, or "loaners." These batteries are assembled and charged just as are batteries which have been in dry storage, see page 241.

If the repairman who "fabricates" batteries takes chances, the man who attempts to actually make his own battery plates is certainly risking his business and reputation. There are several companies which sell moulds for making plate grids. One even sells cans of lead oxides to enable the repairman to make his own plate paste. Even more foolhardy than the man who wishes to mould plate grids is the man who wishes to mix the lead oxides himself. Many letters asking for paste formulas have been received by the author. Such formulas can never be given, for the author does not have them. Paste making is a far more difficult process than many men realize. The lead oxides which are used must be tested and analyzed carefully in a chemical laboratory and the paste formulas varied according to the results of these tests. The oxides must be carefully weighed, carefully handled, and carefully analyzed. The battery service station does not have the equipment necessary to do these things, and no repairman should ever attempt to make plate paste, as trouble is bound to follow such attempts. A car owner may buy a worthless battery once, but the next time he will go to some other service station and buy a good battery.

No doubt many repairmen are as skillful and competent as the workers in battery factories, but the equipment required to make grids and paste is much too elaborate and expensive for the service station, and without such equipment it is impossible to make a good battery.

The only battery parts which may safely be made in the service station are plate straps and posts, intercell connectors, and cell terminals. Moulds for making such parts are on the market, and it is really worth while to invest in a set. The posts made in such moulds are of the plain tapered type, and posts which have special sealing and locking devices, such as the Exide, Philadelphia, and Titan cannot be made in them.

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Chapter 4. Chemical Changes. -----------------

Before explaining what happens within one storage cell, let us look into the early history of the storage battery, and see what a modest beginning the modern heavy duty battery had. Between 1850 and 1860 a man named Plante began his work on the storage battery. His original cell consisted of two plates of metallic lead immersed in dilute sulphuric acid. The acid formed a thin layer of lead sulphate on each plate which soon stopped further action on the lead. If a current was passed through the cell, the lead sulphate on the "anode" or lead plate at which the current entered the cell was changed into peroxide of lead, while the sulphate on the other lead plate or "cathode" was changed into pure lead in a spongy form. This cell was allowed to stand for several days and was then "discharged," lead sulphate being again formed on each plate. Each time this cell was charged, more "spongy" lead and peroxide of lead were formed. These are called the "active" materials, because it is by the chemical action between them and the sulphuric acid that the electricity is produced. Evidently, the more active materials the plates contained, the longer the chemical action between the acid and active materials could take place, and hence the greater the "capacity," or amount of electricity furnished by the cell. The process of charging and discharging the battery so as to increase the amount of active material, is called "forming" the plates.

[Fig. 19 Illustration of chemical action in a storage cell during charge]

Plante's method of forming plates was very slow, tedious, and expensive. If the spongy lead, and peroxide of lead could be made quickly from materials which could be spread over the plates, much time and expense could be saved. It was Faure who first suggested such a plan, and gave us the "pasted" plate of today, which consists of a skeleton framework of lead, with the sponge lead and peroxide of lead filling the spaces between the "ribs" of the framework. Such plates are known as "pasted" plates, and are much lighter and more satisfactory, for automobile work than the heavy solid lead plates of Plante's. Chapter 3 describes more fully the processes of manufacturing and pasting the plates.

We know now what constitutes a storage battery, and what the parts are that "generate" the electricity. How is the electricity produced? Theoretically, if we take a battery which has been entirely discharged, so that it is no longer able to cause a flow of current, and examine and test the electrolyte and the materials on the plates, we shall find that the electrolyte is pure water, and both sets of plates composed of white lead sulphate. On the other hand, if we make a similar test and examination of the plates and electrolyte of a battery through which a current has been sent from some outside source, such as a generator, until the current can no longer cause chemical reactions between the plates and electrolyte, we will find that the electrolyte is now composed of water and Sulphuric acid, the acid comprising about 30%, and the water 70% of the electrolyte. The negative set of plates will be composed of pure lead in a spongy form, while the positive will consist of peroxide of lead.

The foregoing description gives the final products of the chemical changes that take place in the storage battery. To understand the changes themselves requires a more detailed investigation. The substances to be considered in the chemical actions are sulphuric acid, water, pure lead, lead sulphate, and lead peroxide. With the exception of pure lead, each of these substances is a chemical compound, or composed of several elements. Thus sulphuric acid is made up of two parts of hydrogen, which is a gas; one part of sulphur, a solid, and four parts of oxygen, which is also a gas; these combine to form the acid, which is liquid, and which is for convenience written as H2SO 4, H2 representing two parts of hydrogen, S one part of sulphur, and 04, four parts oxygen. Similarly, water a liquid, is made up of two parts of hydrogen and one part of oxygen, represented by the symbol H2O. Lead is not a compound, but an element whose chemical symbol is Pb, taken from the Latin name for lead. Lead sulphate is a solid, and consists of one part of lead, a solid substance, one part of sulphur, another solid substance, and four parts of oxygen, a gas. It is represented chemically by Pb SO4. Lead peroxide is also a solid, and is made up of one part of lead, and two parts of oxygen. In the chemical changes that take place, the compounds just described are to a certain extent split up into the substances of which they are composed. We thus have lead (Pb), hydrogen (H), oxygen (0), and sulphur (S), four elementary substances, two of which are solids, and two gases. The sulphur does not separate itself entirely from the substances with which it forms the compounds H2SO4 and Pb SO4. These compounds are split into H2 and SO4 and Pb and SO4 respectively. That is, the sulphur always remains combined with four parts of oxygen.

Let us now consider a single storage cell made up of electrolyte, one positive plate, and one negative plate. When this cell is fully charged, or in a condition to produce a current of electricity, the positive plate is made up of peroxide of lead (PbO2), the negative plate of pure lead (Pb), and the electrolyte of dilute sulphuric acid (H 2SO4). This is shown diagrammatically in Fig. 19. The chemical changes that take place when the cell is discharging and the final result of the changes are as follows:

(a). At the Positive Plate: Lead peroxide and sulphuric acid produce lead sulphate, water, and oxygen, or:

[Image] Formula (a). PbO2 + H2SO4 = PbSO4 + H20 + 0

(b). At the Negative Plate: Lead and sulphuric acid produce lead sulphate and Hydrogen, or:

[Image] Formula (b). Pb + H2SO4 = PbSO4 + H2

[Fig. 20 Chemical Reaction in a Storage Cell during Discharge]

The oxygen of equation (a) and the hydrogen of equation (b) combine to form water, as may be shown by adding these two equations, giving one equation for the entire discharge action:

[Image] Formula (c). PbO2 + Pb + 2H2SO4 = 2PbSO4 + 2H2O

In this equation we start with the active materials and electrolyte in their original condition, and finish with the lead sulphate and water, which are the final products of a discharge. Examining this equation, we see that the sulphuric acid of the electrolyte is used up in forming lead sulphate on both positive and negative plates, and is therefore removed from the electrolyte. This gives us the easily remembered rule for remembering discharge actions, which, though open to question from a strictly scientific viewpoint, is nevertheless convenient:

During discharge the acid goes into the plates.

The chemical changes described in (a), (b), and (c) are not instantaneous. That is, the lead, lead peroxide, and sulphuric acid of the fully charged cell are not changed into lead sulphate and water as soon as a current begins to pass through the cell. This action is a gradual one, small portions of these substances being changed at a time. The greater the current that flows through the cell, the faster will the changes occur. Theoretically, the changes will continue to take place as long as any lead, lead peroxide, and sulphuric acid remain. The faster these are changed into lead sulphate and water, the shorter will be the time that the storage cell can furnish a current, or the sooner it will be discharged.

Taking the cell in its discharged condition, let us now connect the cell to a generator and send current through the cell from the positive to the negative plates. This is called "charging" the cell. The lead sulphate and water will now gradually be changed back into lead, lead peroxide, and sulphuric acid. The lead sulphate which is on the negative plate is changed to pure lead; the lead sulphate on the positive plate is changed to lead peroxide, and sulphuric acid will be added to the water. The changes at the positive plate may be represented as follows:

Lead sulphate and water produce sulphuric acid, hydrogen and lead peroxide, or:

[Image] Formula (d). PbSO4 + 2H2O = PbO2 + H2SO4 + H2

The changes at the negative plate may be expressed as follows: Lead sulphate and water produced sulphuric acid, oxygen, and lead, or:

[Image] Formula (e). PbSO4 + H2o = Pb + H2SO4 + O

The hydrogen (H2) produced at the positive plate, and the oxygen (0) produced at the negative plate unite to form water, as may be shown by the equation:

[Image] Formula (f). 2PbSO4 + 2H2O = PbO2 + Pb + 2H2SO4

Equation (f) starts with lead sulphate and water, which, as shown in equation (c), are produced when a battery is discharged. It will be observed that we start with lead sulphate and water. Discharged plates may therefore be charged in water. In fact, badly discharged negatives may be charged better in water than in electrolyte. The electrolyte is poured out of the battery and distilled water poured in. The acid remaining on the separators and plates is sufficient to make the water conduct the charging current.

In equation (f), the sulphate on the plates combines with water to form sulphuric acid. This gives us the rule:

During charge, acid is driven out of the plates.

This rule is a convenient one, but, of course, is not a strictly correct statement.

The changes produced by sending a current through the cell are also gradual, and will take place faster as the current is made greater. When all the lead sulphate has been used up by the chemical changes caused by the current, no further charging can take place. If we continue to send a current through the cell after it is fully charged, the water will continue to be split up into hydrogen and oxygen. Since, however, there is no more lead sulphate left with which the hydrogen and oxygen can combine to form lead, lead peroxide, and sulphuric acid, the hydrogen and oxygen rise to the surface of the electrolyte and escape from the cell. This is known as "gassing", and is an indication that the cell is fully charged.

Relations Between Chemical Actions and Electricity.

We know now that chemical actions in the battery produce electricity and that, on the other hand, an electric current, sent through the battery from an outside source, such as a generator, produces chemical changes in the battery. How are chemical changes and electricity related? The various chemical elements which we have in a battery are supposed to carry small charges of electricity, which, however, ordinarily neutralize one another. When a cell is discharging, however, the electrolyte, water, and active materials are separated into parts carrying negative and positive charges, and these "charges" cause what we call an electric current to flow in the apparatus attached to the battery.

Similarly, when a battery is charged, the charging current produces electrical "charges" which cause the substances in the battery to unite, due to the attraction of position and negative charges for one another. This is a brief, rough statement of the relations between chemical reactions and electricity in a battery. A more thorough study of the subject would be out of place in this book. It is sufficient for the repairman to remember that the substances in a battery carry charges of electricity which become available as an electric current when a battery discharges, and that a charging current causes electric charges to form, thereby "charging" the battery.

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CHAPTER 5. WHAT TAKES PLACE DURING DISCHARGE. ----------------------------------

Considered chemically, the discharge of a storage battery consists of the changing of the spongy lead and lead peroxide into lead sulphate, and the abstraction of the acid from the electrolyte. Considered electrically, the changes are more complex, and require further investigation. The voltage, internal resistance, rate of discharge, capacity, and other features must be considered, and the effects of changes in one upon the others must be studied. This proceeding is simplified considerably if we consider each point separately. The abstraction of the acid from the electrolyte gives us a method of determining the condition of charge or discharge in the battery, and must also be studied.

[Fig. 21 Graph: voltage changes at end and after charge]

Voltage Changes During Discharge. At the end of a charge, and before opening the charging circuit, the voltage of each cell is about 2.5 to 2.7 volts. As soon as the charging circuit is opened, the cell voltage drops rapidly to about 2.1 volts, within three or four minutes. This is due to the formation of a thin layer of lead sulphate on the surface of the negative plate and between the lead peroxide and the metal of the positive plate. Fig. 21 shows how the voltage changes during the last eight minutes of charge, and how it drops rapidly as soon as the charging circuit is opened. The final value of the voltage after the charging circuit is opened is about 2.15-2.18 volts. This is more fully explained in Chapter 6. If a current is drawn from the battery at the instant the charge is stopped, this drop is more rapid. At the beginning of the discharge the voltage has already had a rapid drop from the final voltage on charge, due to the formation of sulphate as explained above. When a current is being drawn from the battery, the sudden drop is due to the internal resistance of the cell, the formation of more sulphate, and the abstracting of the acid from the electrolyte which fills the pores of the plate. The density of this acid is high just before the discharge is begun. It is diluted rapidly at first, but a balanced condition is reached between the density of the acid in the plates and in the main body of the electrolyte, the acid supply in the plates being maintained at a lowered density by fresh acid flowing into them from the main body of electrolyte. After the initial drop, the voltage decreases more slowly, the rate of decrease depending on the amount of current drawn from the battery. The entire process is shown in Fig. 22.

[Fig. 22 Graph: voltage changes during discharge]

Lead sulphate is being formed on the surfaces, and in the body of the plates. This sulphate has a higher resistance than the lead or lead peroxide, and the internal resistance of the cell rises, and contributes to the drop in voltage. As this sulphate forms in the body of the plates, the acid is used up. At first this acid is easily replaced from the main body of the electrolyte by diffusion. The acid in the main body of the electrolyte is at first comparatively strong, or concentrated, causing a fresh supply of acid to flow into the plates as fast as it is used up in the plates. This results in the acid in the electrolyte growing weaker, and this, in turn, leads to a constant decrease in the rate at which the fresh acid flows, or diffuses into the plates. Furthermore, the sulphate, which is more bulky than the lead or lead peroxide fills the pores in the plate, making it more and more difficult for acid to reach the interior of the plate. This increases the rate at which the voltage drops.

The sulphate has another effect. It forms a cover over the active material which has not been acted upon, and makes it practically useless, since the acid is almost unable to penetrate the coating of sulphate. We thus have quantities of active material which are entirely enclosed in sulphate, thereby cutting down the amount of energy which can be taken from the battery. Thus the formation of sulphate throughout each plate and the abstraction of acid from the electrolyte cause the voltage to drop at a constantly increasing rate.

Theoretically, the discharge may be continued until the voltage drops to zero, but practically, the discharge should be stopped when the voltage of each cell has dropped to 1.7 (on low discharge rates). If the discharge is carried on beyond this point much of the spongy lead and lead peroxide have either been changed into lead sulphate, or have been covered up by the sulphate so effectively that they are almost useless. Plates in this condition require a very long charge in order to remove all the sulphate.

The limiting value of 1.7 volts per cell applies to a continuous discharge at a moderate rate. At a very high current flowing for only a very short time, it is not only safe, but advisable to allow a battery to discharge to a lower voltage, the increased drop being due to the rapid dilution of the acid in the plates.

The cell voltage will rise somewhat every time the discharge is stopped. This is due to the diffusion of the acid from the main body of electrolyte into the plates, resulting in an increased concentration in the plates. If the discharge has been continuous, especially if at a high rate, this rise in voltage will bring the cell up to its normal voltage very quickly on account of the more rapid diffusion of acid which will then take place.

The voltage does not depend upon the area of the plate surface but upon the nature of the active materials and the electrolyte. Hence, although the plates of a cell are gradually being covered with sulphate, the voltage, measured when no current is flowing, will fall slowly and not in proportion to the amount of energy taken out of the cell. It is not until the plates are pretty thoroughly covered with sulphate, thus making it difficult for the acid to reach the active material, that the voltage begins to drop rapidly. This is shown clearly in Fig. 22, which shows that the cell voltage has dropped only a very small amount when the cell is 50% discharged. With current flowing through the cell, however, the increased internal resistance causes a marked drop in the voltage. Open circuit voltage is not useful, therefore to determine how much energy has been taken from the battery.

Acid Density. The electrolyte of a lead storage battery is a mixture of chemically pure sulphuric acid, and chemically pure water, the acid forming about 30 per cent of the volume of electrolyte when the battery is fully charged. The pure acid has a "specific gravity" of 1.835, that is, it is 1.835 times as heavy as an equal volume of water. The mixture of acid and water has a specific gravity of about 1.300. As the cell discharges, acid is abstracted from the electrolyte, and the weight of the latter must therefore grow less, since there will be less acid in it. The change in the weight, or specific gravity of the electrolyte is the best means of determining the state of discharge of a cell, provided that the cell has been used properly. In order that the value of the specific gravity may be used as an indication of the amount of energy in a battery, the history of the battery must be known. Suppose, for instance, that in refilling the battery to replace the water lost by the natural evaporation which occurs in the use of a battery, acid, or a mixture of acid and water has been used. This will result in the specific gravity being too high, and the amount of energy in the battery will be less than that indicated by the specific gravity. Again, if pure water is used to replace electrolyte which has been spilled, the specific gravity will be lower than it should be. In a battery which has been discharged to such an extent that much of the active material has been covered by a layer of tough sulphate, or if a considerable amount of sulphate and active material has been loosened from the plates and has dropped to the bottom of the cells, it will be impossible to bring the specific gravity of the electrolyte up to 1.300, even though a long charge is given. There must, therefore, be a reasonable degree of certainty that a battery has been properly handled if the specific gravity readings are to be taken as a true indication of the condition of a battery. Where a battery does not give satisfactory service even though the specific gravity readings are satisfactory, the latter are not reliable as indicating the amount of charge in the battery.

As long as a discharge current is flowing from the battery, the acid within the plates is used up and becomes very much diluted. Diffusion between the surrounding electrolyte and the acid in the plates keeps up the supply needed in the plates in order to, carry on the chemical changes. When the discharge is first begun, the diffusion of acid into the plates takes place rapidly because there is little sulphate clogging the pores in the active material, and because there is a greater difference between the concentration of acid in the electrolyte and in the plates than will exist as the discharge progresses. As the sulphate begins to form and fill up the pores of the plates, and as more and more acid is abstracted from the electrolyte, diffusion takes place more slowly.

If a battery is allowed to stand idle for a short time after a partial discharge, the specific gravity of the electrolyte will decrease because some, of the acid in the electrolyte will gradually flow into the pores of the plates to replace the acid used up while the battery was discharging. Theoretically the discharge can be continued until all the acid has been used up, and the electrolyte is composed of pure water. Experience has shown, however, that the discharge of the battery should not be continued after the specific gravity of the electrolyte has fallen to 1.150. As far as the electrolyte is concerned, the discharge may be carried farther with safety. The plates determine the point at which the discharge should be stopped. When the specific gravity has dropped from 1.300 to 1.150, so much sulphate has been formed that it fills the pores in the active material on the plates. Fig. 23 shows the change in the density of the acid during discharge.

[Fig. 23: Variation of Capacity with Specific Gravity]

Changes at the Negative Plate. Chemically, the action at the negative plate consists only of the formation of lead sulphate from the spongy lead. The lead sulphate is only slightly soluble in the electrolyte and is precipitated as soon as it is formed, leaving hydrogen ions, which then go to the lead peroxide plate to form water with oxygen ions released at the peroxide plate. The sulphate forms more quickly on the surface of the plate than in the inner portions because there is a constant supply of acid available at the surface, whereas the formation of sulphate in the interior of the plate requires that acid diffuse into the pores of the active materials to replace that already used up in the formation of sulphate. In the negative plate, however, the sulphate tends to form more uniformly throughout the mass of the lead, because the spongy lead is more porous than the lead peroxide, and because the acid is not diluted by the formation of water as in the positive plate.

Changes at the Positive Plate. In a fully charged positive plate we have lead peroxide as the active material. This is composed of lead and oxygen. From this fact it is plainly evident that during discharge there is a greater chemical activity at this plate than at the negative plate, since we must find something to combine with the oxygen in order that the lead may form lead sulphate with the acid. In an ideal cell, therefore, the material which undergoes the greater change should be more porous than the material which does not involve as great a chemical reaction. In reality, however, the peroxide is not as porous as the spongy lead, and does not hold together as well.

The final products of the discharge of a positive plate are lead sulphate and water. The lead peroxide must first be reduced to lead, which then combines with the sulphate from the acid to form lead sulphate, while the oxygen from the peroxide combines with the hydrogen of the acid to form water. There is, therefore, a greater activity at this plate than at the lead plate, and the formation of the water dilutes the acid in and around the plate so that the tendency is for the chemical actions to be retarded.

The sulphate which forms on discharge causes the active material to bulge out because it occupies more space than the peroxide. This causes the lead peroxide at the surface to begin falling, to the bottom of the jar in fine dust-like particles, since the peroxide here holds together very poorly.

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Chapter 6. What Takes Place During Charge. -------------------------------

Voltage. Starting with a battery which has been discharged until its voltage has decreased to 1.7 per cell, we pass a current through it and cause the voltage to rise steadily. Fig. 24 shows the changes in voltage during charge. Ordinarily the voltage begins to rise immediately and uniformly. If, however, the battery has been left in a discharged condition for some time, or has been "over discharged," the voltage rises very rapidly for a fraction of the first minute of charge and then drops rapidly to the normal value and thereafter begins to rise steadily to the end of the charge. This rise at the beginning of the charge is due to the fact that the density of the acid in the pores of the plates rises rapidly at first, the acid thus formed being prevented from diffusing into the surrounding electrolyte by the coating of sulphate. As soon as this sulphate is broken through, diffusion takes place and the voltage drops.

[Fig. 24 Graph: voltage changes during charge]

As shown in Fig. 24, the voltage remains almost constant between the points M and N. At N the voltage begins to rise because the charging chemical reactions are taking place farther and farther in the inside parts of the plate, and the concentrated acid formed by the chemical actions in the plates is diffusing into the main electrolyte. This increases the battery voltage and requires a higher charging voltage.

At the point marked 0, the voltage begins to rise very rapidly. This is due to the fact that the amount of lead sulphate in the plates is decreasing very rapidly, allowing the battery voltage to rise and thus increasing the charging voltage. Bubbles of gas are now rising through the electrolyte.

At P, the last portions of lead sulphate are removed, acid is no longer being formed, and hydrogen and oxygen gas are formed rapidly. The gas forces the last of the concentrated acid out of the plates and in fact, equalizes the acid concentration throughout the whole cell. Thus no further changes can take place, and the voltage becomes constant at R at a voltage of 2.5 to 2.7.

Density of Electrolyte. Discharge should be stopped when the density of the electrolyte, as measured with a hydrometer, is 1.150. When we pass a charging current through the battery, acid is produced by the chemical actions which take place in the plates. This gradually diffuses with the main electrolyte and causes the hydrometer to show a higher density than before. This increase in density continues steadily until the battery begins to "gas" freely.

The progress of the charge is generally determined by the density of the electrolyte. For this purpose in automobile batteries, a hydrometer is placed in a glass syringe having a short length of rubber tubing at one end, and a large rubber bulb at the other. The rubber tube is inserted in the cell and enough electrolyte drawn up into the syringe to float the hydrometer so as to be able to obtain a reading. This subject will be treated more fully in a later chapter.

Changes at Negative Plate. The charging current changes lead sulphate into spongy lead, and acid is formed. The acid is mixed with the diluted electrolyte outside of the plates. As the charging proceeds the active material shrinks or contracts, and the weight of the plate actually decreases on account of the difference between the weight and volume of the lead sulphate and spongy lead. If the cell has had only a normal discharge and the charge is begun soon after the discharge ended, the charge will proceed quickly and without an excessive rise in temperature. If, however, the cell has been discharged too far, or has been in a discharged condition for some time, the lead sulphate will not be in a finely divided state as it should be, but will be hard and tough and will have formed an insulating coating over the active material, causing the charging voltage to be high, and the charge will proceed slowly. When most of the lead sulphate has been reduced to spongy lead, the charging current will be greater than is needed to carry on the chemical actions, and will simply decompose the water into hydrogen and oxygen, and the cell "gasses." Spongy lead is rather tough and coherent, it, and the bubbles of gas which form in the pores of the negative plate near the end of the charge force their way to the surface without dislodging any of the active material.

Changes at the Positive Plate. When a cell has been discharged, a portion of the lead peroxide has been changed to lead sulphate, which has lodged in the pores of the active material and on its surface. During charge, the lead combines with oxygen from the water to form lead peroxide, and acid is formed. This acid diffuses into the electrolyte as fast as the amount of sulphate will permit. If the discharge has been carried so far that a considerable amount of sulphate has formed in the pores and on the surface of the plate, the action proceeds very slowly, and unless a moderate charging current is used, gassing begins before the charge is complete, simply because the sulphate cannot absorb the current. The gas bubbles which originate in the interior of the plate force their way to the surface, and in so doing cause numerous fine particles of active material to break off and fall to the bottom of the jar. This happens because the lead peroxide is a granular, non-coherent substance, with the particles held together very loosely, and the gas breaks off a considerable amount of active material.

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Chapter 7. Capacity Of Storage Batteries. ------------------------------

The capacity of a storage battery is the product of the current drawn from a battery, multiplied by the number of hours this current flows. The unit in which capacity is measured is the ampere-hour. Theoretically, a battery has a capacity of 40 ampere hours if it furnishes ten amperes for four hours, and if it is unable, at the end of that time, to furnish any more current. If we drew only five amperes from this battery, it should be able to furnish this current for eight hours. Thus, theoretically, the capacity of a battery should be the same, no matter what current is taken from it. That is, the current in amperes, multiplied by the number of hours the battery, furnished this current should be constant.

In practice, however, we do not discharge a battery to a lower voltage than 1.7 per cell, except when the rate of discharge is high, such as is the case when using the starting motor, on account of the increasing amount of sulphate and the difficulty with which this is subsequently removed and changed into lead and lead peroxide. The capacity of a storage battery is therefore measured by the number of ampere hours it can furnish before its voltage drops below 1.7 per cell. This definition assumes that the discharge is a continuous one, that we start with a fully charged battery and discharge it continuously until its voltage drops to 1.7 per cell.

The factors upon which the capacity of storage batteries depend may be grouped in two main classifications:

1. Design and Construction of Battery 2. Conditions of Operation

Design and Construction.

Each classification may be subdivided. Under the Design and Construction we have:

(a) Area of plate surface. (b) Quantity, arrangement, and porosity of active materials. (c) Quantity and strength of electrolyte. (d) Circulation of electrolyte.

These sub-classifications require further explanation. Taking them in order:

(a) Area of Plate Surface. It is evident that the chemical and electrical activity of a battery are greatest at the surface of the plates since the acid and active material are in intimate contact here, and a supply of fresh acid is more readily available to replace that which is depleted as the battery is discharged. This is especially true with high rates of discharge, such as are caused in starting automobile engines. Therefore, the capacity of a battery will be greater if the surface area of its plates is increased. With large plate areas a greater amount of acid and active materials is available, and an increase in capacity results.

(b) Quantity, Arrangement, and Porosity of Active Materials. Since the lead and lead peroxide are changed to lead sulphate on discharge, it is evident that the greater the amount of these materials, the longer can the discharge continue, and hence the greater the capacity.

The arrangement of the active materials is also important, since the acid and active materials must be in contact in order to produce electricity. Consequently the capacity will be greater in a battery, all of whose active materials are in contact with the acid, than in one in which the acid reaches only a portion of the active materials. It is also important that all parts of the plates carry the same amount of current, in order that the active materials may be used evenly. As a result of these considerations, we find that the active materials are supported on grids of lead, that the plates are made thin, and that they have large surface areas. For heavy discharge currents, such as starting motor currents, it is essential that there be large surface areas. Thick plates with smaller surface areas are more suitable for low discharge rates.

Since the inner portions of the active materials must have a plentiful and an easily renewable supply of acid, the active materials must be porous in order that diffusion may be easy and rapid.

(c) Quantity and Strength of Electrolyte. It is important that there be enough electrolyte in order that the acid may not become exhausted while there is still considerable active material left. An insufficient supply of electrolyte makes it impossible to obtain the full capacity from a battery. On the other hand, too much electrolyte, due either to filling the battery too full, or to having the plates in a jar that holds too much electrolyte, results in an increase in capacity up to the limit of the plate capacity. There is a danger present, however, because with an excess of electrolyte the plates will be discharged before the specific gravity of the electrolyte falls to 1.150. This results in over discharge of the battery with its attendant troubles as will be described more fully in a later chapter.

It is a universal custom to consider a battery discharged when the specific gravity of the electrolyte has dropped to 1.150, and that it is fully charged when the specific gravity of the electrolyte has risen to 1.280-1.300. This is true in temperate climates. In tropical countries, which may for this purpose be defined as those countries in which the temperature never falls below the freezing point, the gravity of a fully charged cell is 1.200 to 1.230. The condition of the plates is, however, the true indicator of charged or discharged condition. With the correct amount of electrolyte, its specific gravity is 1.150 when the plates have been discharged as far as it is considered safe, and is 1.280-1.300 when the plates are fully charged. When electrolyte is therefore poured into a battery, it is essential that it contains the proper proportion of acid and water in order that its specific gravity readings be a true indicator of the condition of the plates as to charge or discharge, and hence show accurately how much energy remains in the cell at any time.

A question which may be considered at this point is why in automobile, work a specific gravity of 1.280-1.300 is adopted for the electrolyte of a fully charged cell. There are several reasons. The voltage of a battery increases as the specific gravity goes up. Hence, with a higher density, a higher voltage can be obtained. If the density were increased beyond this point, the acid would attack the lead grids and the separators, and considerable corrosion would result. Another danger of high density is that of sulphation, as explained in a later chapter. Another factor which enters is the resistance of the electrolyte. It is desirable that this be as low as possible. If we should make resistance measurements on various mixtures of acid and water, we should find that with a small percentage of acid, the resistance is high. As the amount of acid is increased, the resistance will grow less up to a certain point. Beyond this point, the resistance will increase again as more acid is added to the mixture. The resistance is lowest when the acid forms 30% of the electrolyte. Thus, if the electrolyte is made too strong, the plates and also the separators will be attacked by the acid, and the resistance of the electrolyte will also increase. The voltage increases as the proportion of acid is increased, but the other factors limit the concentration. If the electrolyte is diluted, its resistance rises, and the amount of acid is insufficient to give much capacity. The density of 1.280-1.300 is therefore a compromise between the various factors mentioned above.

(d) Circulation of Electrolyte. This refers to the passing of electrolyte from one plate to another, and depends upon the ease with which the acid can pass through the pores of the separators. A porous separator allows more energy to be drawn from the battery than a nonporous one.

Operating Conditions.

Considering now the operating conditions, we find several items to be taken into account. The most important are:

(e) Rate of discharge. (f) Temperature.

(e) Rate of Discharge. As mentioned above, the ampere hour rating of a battery is based upon a continuous discharge, starting with a specific gravity of 1.280-1.300, and finishing with 1.150. The end of the discharge is also considered to be reached when the voltage per cell has dropped to 1.7. With moderate rates of discharge the acid is abstracted slowly enough to permit the acid from outside the plates to diffuse into the pores of the plates and keep up the supply needed for the chemical actions. With increased rates of discharge the supply of acid is used up so rapidly that the diffusion is not fast enough to hold up the voltage. This fact is shown clearly by tests made to determine the time required to discharge a 100 Amp. Hr., 6 volt battery to 4.5 volts. With a discharge rate of 25 amperes, it required 160 minutes. With a discharge rate of 75 amperes, it required 34 minutes. From this we see that making the discharge rate three times as great caused the battery to be discharged in one fifth the time. These discharges were continuous, however, and if the battery were allowed to rest, the voltage would soon rise sufficiently, to burn the lamps for a number of hours.

The conditions of operation in automobile work are usually considered severe. In starting the engine, a heavy current is drawn from the battery for a few seconds. The generator starts charging the battery immediately afterward, and the starting energy is soon replaced. As long as the engine runs, there is no load on the battery, as the generator will furnish the current for the lamps, and also send a charge into the battery. If the lamps are not used, the entire generator output is utilized to charge the battery, unless some current is furnished to the ignition system. Overcharge is quite possible.

When the engine is not running, the lamps are the only load on the battery, and there is no charging current. Various drivers have various driving conditions. Some use their starters frequently, and make only short runs. Their batteries run down. Other men use the starter very seldom, and take long tours. Their batteries will be overcharged. The best thing that can be done is to set the generator for an output that will keep the battery charged under average conditions.

From the results of actual tests, it may be said that modem lead-acid batteries are not injured in any way by the high discharge rate used when a starting motor cranks the engine. It is the rapidity with which fresh acid takes the place of that used in the pores of the active materials that affects the capacity of a battery at high rates, and not only limitation in the plates themselves. Low rates of discharge should, in fact, be avoided more than the high rates. Battery capacity is affected by discharge rates, only when the discharge is continuous, and the reduction in capacity caused by the high rates of continuous discharge does not occur if the discharge is an intermittent one, such as is actually the case in automobile work. The tendency now is to design batteries to give their rated capacity in very short discharge periods. If conditions should demand it, these batteries would be sold to give their rated capacity while operating intermittently at a rate which would completely discharge them in three or four minutes. The only change necessary for such high rates of discharge is to provide extra heavy terminals to carry the heavy current.

The present standard method of rating starting and lighting batteries, as recommended by the Society of Automotive Engineers, is as follows:

"Batteries for combined lighting and starting service shall have two ratings. The first shall indicate the lighting ability, and shall be the capacity in ampere hours of the battery when discharged continuously at the 5 hour rate to a final voltage of not less than 1.7 per cell, the temperature of the battery beginning such discharge being 80°F. The second rating shall indicate the starting ability and shall be the capacity in ampere-hours when the battery is discharged continuously at the 20-minute rate to a final voltage of not less than 1.5 per cell, the temperature of the battery beginning such discharge being 80°F."

The discharge rate required under the average starting conditions is higher than that specified above, and would cause the required drop in voltage in about fifteen minutes. In winter, when an engine is cold and stiff, the work required from the battery is even more severe, the discharge rate being equivalent in amperes to probably four or five times the ampere-rating of the battery. On account of the rapid recovery of a battery after a discharge at a very high rate, it seems advisable to allow a battery to discharge to a voltage of 1.0 per cell when cranking an engine which is extremely cold and stiff.

(f) Temperature. Chemical reactions take place much more readily at high temperatures than at low. Furthermore, the active materials are more porous, the electrolyte lighter, and the internal resistance less at higher temperatures. Opposed to this is the fact that at high temperatures, the acid attacks the grids and active materials, and lead sulphate is formed, even though no current is taken from the battery. Other injurious effects are the destructive actions of hot acid on the wooden separators used in most starting and lighting batteries. Greater expansion of active material will also occur, and this expansion is not, in general, uniform over the surface of the plates. This results in unequal strains and the plates are bent out of shape, or "buckled." The expansion of the active material will also cause much of it to fall from the plates, and we then have "shedding."

[Fig. 25 Graph: Theoretical temperature changes during charge and discharge]

When sulphuric acid is poured into water, a marked temperature rise takes place. When a battery is charged, acid is formed, and when this mixes with the diluted electrolyte, a temperature rise occurs. In discharging, acid is taken from the electrolyte, and the temperature has a tendency to drop. On charging, therefore, there is danger of overheating, while on discharge, excessive temperatures are not likely. Fig. 25 shows the theoretical temperature changes on charge and discharge. The decrease in temperature given-in the curve is not actually obtained in practice, because the tendency of the temperature to decrease is balanced by the heat caused by the current passing through the battery.

Age of Battery.

Another factor which should be considered in connection with capacity is the age of the battery. New batteries often do not give their rated capacity when received from the manufacturer. This is due to the methods of making the plates. The "paste" plates, such as are used in automobiles, are made by applying oxides of lead, mixed with a liquid, which generally is dilute sulphuric acid, to the grids. These oxides must be subjected to a charging current in order to produce the spongy lead and lead peroxide. After the charge, they must be discharged, and then again charged. This is necessary because not all of the oxides are changed to active material on one charge, and repeated charges and discharges are required to produce the maximum amount of active materials. Some manufacturers do not charge and discharge a battery a sufficient number of times before sending it out, and after a battery is put into use, its capacity will increase for some time, because more active material is produced during each charge.

Another factor which increases the capacity of a battery after it is put into use is the tendency of the positive active material to become more porous after the battery is put through the cycles of charge and discharge. This results in an increase in capacity for a considerable time after the battery is put into use.

When, a battery has been in use for some time, a considerable portion of the active material will have fallen from the positive plates, and, a decrease in capacity will result. Such a battery will charge faster than a new one because the amount of sulphate which has formed when the battery is discharged is less than in a newer battery. Hence, the time required to reduce this sulphate will be less, and the battery will "come up" faster on charge, although the specific gravity of the electrolyte may not rise to 1.280.

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Chapter 8. Internal Resistance. --------------------

The resistance offered by a storage battery to the flow of a current through it results in a loss of voltage, and in heating. Its value should be as low as possible, and, in fact, it is almost negligible even I in small batteries, seldom rising above 0.05 ohm. On charge, it causes the charging voltage to be higher and on discharge causes a loss of voltage. Fig. 26 shows the variation in resistance.

[Fig. 26 Graph: Changes in internal resistance during charge and discharge]

The resistance as measured between the terminals of a cell is made up of several factors as follows:

1. Grids. This includes the resistance of the terminals, connecting links, and the framework upon which the active materials are pasted. This is but a small part of the total resistance, and does not undergo any considerable change during charge and discharge. It increases slightly as the temperature of the grids rises.

2. Electrolyte. This refers to the electrolyte between the plates, and varies with the amount of acid and with temperature. As mentioned in the preceding chapter, a mixture of acid and water in which the acid composes thirty per cent of the electrolyte has the minimum resistance. Diluting or increasing the concentration of the electrolyte will both cause an increase in resistance from the minimum I value. The explanation probably lies in the degree to which the acid is split up into "ions" of hydrogen (H), and sulphate (SO4). These "ions" carry the current through t he electrolyte. Starting with a certain amount of acid, let us see how the ionization progresses. With very concentrated acid, ionization does not take place, and hence, there are no ions to carry current. As we mix the acid with water, ionization occurs. The more water used, the more ions, and hence, the less the resistance, because the number of ions available to carry the current increases. The ionization in creases to a certain maximum degree, beyond which no more ions are formed. It is probable that an electrolyte containing thirty per cent of acid is at its maximum degree of ionization and hence its lowest resistance. If more water is now added, no more ions are formed. Furthermore, the number of ions per unit volume of electrolyte will now decrease on account of the increased amount of water. There Will therefore be fewer ions per unit volume to carry the current, and the resistance of the electrolyte increases.

With an electrolyte of a given concentration, an increase of temperature will cause a decrease in resistance. A decrease in temperature will, of course, cause an increase in resistance. It is true, in general, that the resistance of the electrolyte is about half of the total resistance of the cell. The losses due to this resistance generally form only one per cent of the total losses, and area practically negligible factor.

3. Active Material. This includes the resistance of the active materials and the electrolyte in the pores of the active materials. This varies considerably during charge and discharge. It has been found that the resistance of the peroxide plate changes much more than that of the lead plate. The change in resistance of the positive plate is especially marked near the end of a discharge. The composition of the active material, and the contact between it and the grid affect the resistance considerably.

During charge, the current is sent into the cell from an external source. The girds therefore carry most of the current. The active material which first reacts with the acid is that near the surface of the plate, and the acid formed by the charging current mixes readily with the main body of electrolyte. Gradually, the charging action takes place in the inner portions of the plate, and concentrated acid is formed in the pores of the plate. As the sulphate is removed, however, the acid has little difficulty in mixing with the main body of electrolyte. The change in resistance on the charge is therefore not considerable.

During discharge, the chemical action also begins at the surface of the plates and gradually moves inward. In this case, however, sulphate is formed on the surface first, and it becomes increasingly difficult for the fresh acid from the electrolyte to diffuse into the plates so as to replace the acid which has been greatly diluted there by the discharge actions. There is therefore an increase in resistance because of the dilution of the acid at the point of activity. Unless a cell is discharged too far, however, the increase in resistance is small.

If a battery is allowed to stand idle for a long time it gradually discharges itself, as explained in Chapter 10. This is due to the formation of a tough coating of crystallized lead sulphate, which is practically an insulator. These crystals gradually cover and enclose the active material. The percentage change is not high, and generally amounts to a few per cent only. The chief damage caused by the excessive sulphation is therefore not an increase in resistance, but consists chiefly of making a poor contact between active material and grid, and of removing much of the active material from action by covering it.

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Chapter 9. Care Of The Battery On The Car. -------------------------------

The manufacturers of Starting and Lighting Equipment have designed their generators, cutouts, and current controlling devices so as to relieve the car owner of as much work as possible in taking care of batteries. The generators on most cars are automatically connected to the battery at the proper time, and also disconnected from it as the engine slows down. The amount of current which the generator delivers to the battery is automatically prevented from exceeding a certain maximum value. Under the average conditions of driving, a battery is kept in a good condition. It is impossible, however, to eliminate entirely the need of attention on the part of the car owner, and battery repairman.

The storage battery requires but little attention, and this is the very reason why many batteries are neglected. Motorists often have the impression that because their work in caring for a battery is quite simple, no harm will result if they give the battery no attention whatever. If the battery fails to turn over the engine when the starting switch is closed, then instruction books are studied. Thereafter more attention is paid to the battery. The rules to be observed in taking care of the battery which is in service on the car are not difficult to observe. It is while on the car that a battery is damaged, and the damage may be prevented by intelligent consideration of the battery's housing and living conditions, just as these conditions are made as good as possible for human beings.

1. Keep the Interior of the Battery Box Clean and Dry. On many cars the battery is contained in an iron box, or under the seat or floorboards. This box must be kept dry, and frequent inspection is necessary to accomplish this. Moisture condenses easily in a metal box, and if not removed will cause the box to become rusty. Pieces of rust may fall on top of the battery and cause corrosion and leakage of current between terminals.

Occasionally, wash the inside of the box with a rag dipped in ammonia, or a solution of baking soda, and then wipe it dry. A good plan is to paint the inside of the box with asphaltum paint. This will prevent rusting, and at the same time will prevent the iron from being attacked by electrolyte which may be spilled, or may leak from the battery.

Some batteries are suspended from the car frame under the floor boards or seat. The iron parts near such batteries should be kept dry and free from rust. If the battery has a roof of sheet iron placed above it, this roof should also be kept clean, dry and coated with asphaltum paint.

[Fig. 27 "Do not drop tools on top of battery"]

2. Put Nothing But the Battery in the Battery Box. If the battery is contained in an iron box, do not put rags, tools, or anything else of a similar nature in the battery box. Do not lay pliers across the top of the battery, as shown in Fig. 27. Such things belong elsewhere. The battery should have a free air space all around it, Fig. 28. Objects made of metal will short-circuit the battery and lead to a repair bill.

3. Keep the battery clean and dry. The top of the battery should be kept free of dirt, dust, and moisture. Dirt may find its way into the cells and damage the battery. A dirty looking battery is an unsightly object, and cleanliness should be maintained for the sake of the appearance of the battery if for no other reason.

Moisture on top of the battery causes a leakage of current between the terminals of the cells and tends to discharge the battery. Wipe off all moisture and occasionally go over the tops of the cell connectors, and terminals with a rag wet with ammonia or a solution of baking soda. This will neutralize any acid which may be present in the moisture.

The terminals should be dried and covered with vaseline. This protects them from being attacked by acid which may be spilled on top of the battery. If a deposit of a grayish or greenish substance is found on the battery terminals, handles or cell connectors, the excess should be scraped off and the parts should then be washed with a hot solution of baking soda (bicarbonate of soda) until all traces of the substance have been removed. In scraping off the deposit, care should be taken not to scrape off any lead from terminals or connectors. After washing the parts, dry them and cover them with vaseline. The grayish or greenish substance found on the terminals, connectors, or handles is the result of "corrosion," or, in other words, the result of the action of the sulphuric acid in the electrolyte upon some metallic substance.

[Fig. 28 Battery installed with air space on all sides]

The acid which causes the corrosion may be spilled on the battery when hydrometer readings are taken. It may also be the result of filling the cells too full, with subsequent expansion and overflowing as the temperature of the electrolyte increases during charge. Loose vent caps may allow electrolyte to be thrown out of the cell by the motion of the car on the road. A poorly sealed battery allows electrolyte to be thrown out through the cracks left between the sealing compound and the jars or posts. The leaks may be caused by the battery cables not having sufficient slack, and pulling on the terminals.

The cap which fits over the vent tube at the center of the top of each cell is pierced by one or more holes through which gases formed within the cell may escape. These holes must be kept open; otherwise the pressure of the gases may blow off the top of the cell. If these holes are found to be clogged with dirt they should be cleaned out thoroughly.

The wooden battery case should also be kept clean and dry. If the battery is suspended from the frame of the car, dirt and mud from the road will gradually cover the case, and this mud should be scraped off frequently. Occasionally wash the case with a rag wet with ammonia, or hot baking soda solution. Keep the case, especially along the top edges, coated with asphaltum or some other acid proof paint.

[Fig. 29 Battery held in place by "hold-down" bolts]

4. The battery must be held down firmly. If the battery is contained in an iron box mounted on the running-board, or in a compartment in the body of the car having a door at the side of the running-board, it is usually fastened in place by long bolts which hook on the handles or the battery case. These bolts, which are known as "hold-downs," generally pass through the running board or compartment, Fig. 29, and are generally fastened in place by nuts. These nuts should be turned up so that the battery is held down tight.

Other methods are also used to hold the battery in place, but whatever the method, it is vital to the battery that it be held down firmly so that the jolting of the car cannot cause it to move. The battery has rubber jars which are brittle, and which are easily broken. Even if a battery is held down firmly, it is jolted about to a considerable extent, and with a loosely fastened battery, the jars are bound to be cracked and broken.

5. The cables connected to the battery must have sufficient slack so that they will not pull on the battery terminals, as this will result in leaks, and possibly a broken cover.

The terminals on a battery should be in such a position that the cables may be connected to them easily, and without bending and twisting them. These cables are heavy and stiff, and once they are bent or twisted they are put under a strain, and exert a great force to straighten themselves. This action causes the cables to pull on the terminals, which become loosened, and cause a leak, or break the cover.

[Fig. 30 Measure height of electrolyte in battery]

6. Inspect the Battery twice every month in Winter, and once a week in Summer, to make sure that the Electrolyte covers the plates. To do this, remove the vent caps and look down through the vent tube. If a light is necessary to determine the level of the electrolyte, use an electric lamp. Never bring an open flame, such as a match or candle near the vent tubes of a battery. Explosive gases are formed when a battery "gasses," and the flame may ignite them, with painful injury to the face and eyes of the observer as a result. Such an explosion may also ruin the battery.

During the normal course of operation of the battery, water from the electrolyte will evaporate. The acid never evaporates. The surface of the electrolyte should be not less than one-half inch above the tops of the plate. A convenient method of measuring the height of the electrolyte is shown in Fig. 30. Insert one end of a short piece of a glass tube, having an opening not less than one-eighth inch diameter, through the filling hole, and allow it to rest on the upper edge of the plates. Then place your finger over the upper end, and withdraw the tube. A column of liquid will remain in the lower end of the tube, as shown in the figure, and the height of this column is the same as the height of the electrolyte above the top of the plates in the cell. If this is less than one-half inch, add enough distilled water to bring the electrolyte up to the proper level. Fig. 31 shows the correct height of electrolyte in an Exide cell.

Never add well water, spring water, water from a stream, or ordinary faucet water. These contain impurities which will damage the battery, if used. It is essential that distilled water be used for this purpose, and it must be handled carefully so as to keep impurities of any kind out of the water. Never use a metal can for handling water or electrolyte for a battery, but always use a glass or porcelain vessel. The water should be stored in glass bottles, and poured into a porcelain or glass pitcher when it is to be used.

[Fig. 31 Correct height of electrolyte in Exide cell]

A convenient method of adding the water to the battery is to draw some up in a hydrometer syringe and add the necessary amount to the cell by inserting the rubber tube which is at the lower end into the vent hole and then squeezing the bulb until the required amount has been put into the cell.

In the summer time it makes no difference when water is added. In the winter time, if the air temperature is below freezing (32° F), start the engine before adding water, and keep it running for about one hour after the battery begins to "gas." A good time to add the water is just before starting on a trip, as the engine will then usually be run long enough to charge the battery, and cause the water to mix thoroughly with the electrolyte. Otherwise, the water, being lighter than the electrolyte, will remain at the top and freeze. Be sure to wipe off water from the battery top after filling. If battery has been wet for sometime, wipe it with a rag dampened with ammonia or baking soda solution to neutralize the acid.

Never add acid to a battery while the battery is on the car. By "acid" is meant a mixture of sulphuric acid and water. The concentrated acid, is of course, never used. The level of the electrolyte falls because of the evaporation of the water which is mixed with the acid in the electrolyte. The acid does not evaporate. It is therefore evident that acid should not be added to a cell to replace the water which has evaporated. Some men believe that a battery may be charged by adding acid. This is not true, however, because a battery can be charged only by passing a current through the battery from an outside source. On the car the generator charges the battery.

It is true that acid is lost, but this is not due to evaporation, but to the loss of some of the electrolyte from the cell, the lost electrolyte, of course, carrying some acid with it. Electrolyte is lost when a cell gasses; electrolyte may be spilled; a cracked jar will allow electrolyte to leak out; if too much water is added, the expansion of the electrolyte when the battery is charging may cause it to run over and be lost, or the jolting of the car may cause some of it to be spilled; if a battery is allowed to become badly sulphated, some of the sulphate is never reduced, or drops to the bottom of the cell, and the acid lost in the formation of the sulphate is not regained.

If acid or electrolyte is added instead of water, when no acid is needed, the electrolyte will become too strong, and sulphated plates will be the result. If a battery under average driving conditions never becomes fully charged, it should be removed from the car and charged from an outside source as explained later. If, after the specific gravity of the electrolyte stops rising, it is not of the correct value, some of the electrolyte should be drawn off and stronger electrolyte added in its place. This should be done only in the repair shop or charging station.

Care must be taken not to add too much water to a cell, Fig. 32. This will subsequently cause the electrolyte to overflow and run over the top of the battery, due to the expansion of the electrolyte as the charging current raises its temperature. The electrolyte which overflows is, of course, lost, taking with it acid which will later be replaced by water as evaporation takes place. The electrolyte will then be too weak. The electrolyte which overflows will rot the wooden battery case, and also tend to cause corrosion at the terminals.

If it is necessary to add water very frequently, the battery is operating at too high a temperature, or else there is a cracked jar. The high temperature may be due to the battery being charged at too high a rate, or to the battery being placed near some hot part of the engine or exhaust pipe. The car manufacturer generally is careful not to place the battery too near any such hot part. The charging rate may be measured by connecting an ammeter in series with the battery and increasing the engine speed until the maximum current is obtained. For a six volt battery this should rarely exceed 14 amperes. If the charging, current does not reach a maximum value and then remain constant, or decrease, but continues to rise as the speed of the engine, is increased, the regulating device is out of order. An excessive charging rate will cause continuous gassing if it is much above normal, and the temperature of the electrolyte will be above 100° F. In this way an excessive charging current may be detected.

[Fig. 32 Cell with level of electrolyte too high]

In hot countries or states, the atmosphere may have such a high temperature that evaporation will be more rapid than in temperate climates, and this may necessitate more frequent addition of water.

If one cell requires a more frequent addition of water than the others, it is probable that the jar of that cell is cracked. Such a cell will also show a low specific gravity, since electrolyte leaks out and is replaced by water. A battery which has a leaky jar will also have a case which is rotted at the bottom and sides. A battery with a leaky jar must, of course, be removed from the car for repairs.

"Dope" Electrolytes

From time to time within the past two years, various solutions which are supposed to give a rundown battery a complete charge within five or ten minutes have been offered to the public. The men selling such "dope" sometimes give a demonstration which at first sight seems to prove their claims. This demonstration consists of holding the starting switch down (with the ignition off) until the battery can no longer turn over the engine. They then pour the electrolyte out of the battery, fill it with their "dope," crank the engine by hand, run it for five minutes, and then get gravity readings of 1.280 or over. The battery will also crank the engine. Such a charge is merely a drug-store charge, and the "dope" is generally composed mainly of high gravity acid, which seemingly puts life into a battery, but in reality causes great damage, and shortens the life of a battery. The starting motor test means nothing. The same demonstration could be given with any battery. The high current drawn by the motor does not discharge the battery, but merely dilutes the electrolyte which is in the plates to such an extent that the voltage drops to a point at which the battery can no longer turn over the starting motor. If any battery were given a five minutes charge after such a test, the diluted electrolyte in the plates would be replaced by fresh acid from the electrolyte and the battery would then easily crank the engine again. The five minutes of running the engine does not put much charge into the battery but gives time for the electrolyte to diffuse into the plates.

Chemical analysis of a number of dope electrolytes has shown that they consist mainly of high gravity acid, and that this acid is not even chemically pure, but contains impurities which would ruin a battery even if the gravity were not too high. The results of some of the analyses are as follows:

No. 1. 1.260 specific gravity sulphuric acid, 25 parts iron, 13.5 parts chlorine, 12.5, per cent sodium sulphate, 1 per cent nitric acid.

No. 2. 1.335 specific gravity sulphuric acid, large amounts of organic matter, part of which consisted of acids which attack lead.

No. 3. 1.340 specific gravity sulphuric acid, 15.5 per cent sodium sulphate.

No. 4. 1.290 specific gravity sulphuric acid, 1.5 per cent sodium sulphate.

No. 5. 1.300 specific gravity sulphuric acid.

If such "dope" electrolytes are added to a discharged battery, the subsequent charging of the battery will add more acid to the electrolyte, the specific gravity of which will then rise much higher than it should, and the plates and separators are soon ruined.

Do not put faith in any "magic" solution which is supposed to work wonders. There is only one way to charge a battery, and that is to send a current through it, and there is only one electrolyte to use, and that is the standard mixture of distilled water and chemically pure sulphuric acid.

7. The specific gravity of the electrolyte should be measured every two weeks and a permanent record of the readings made for future reference.

The specific gravity of the electrolyte is the ratio of its weight to the weight of an equal volume of water. Acid is heavier than water, and hence the heavier the electrolyte, the more acid it, contains, and the more nearly it is fully charged. In automobile batteries, a specific gravity of 1.300-1.280 indicates a fully charged battery. Generally, a gravity of 1.280 is taken to indicate a fully, charged cell, and in this book this will be done. Complete readings are as follows:

1.300-1.280--Fully charged.

1.280-1.200--More than half charged.

1.200-1.150--Less than half charged.

1.150 and less--Completely discharged.

[Fig. 33 and Fig. 34: battery hydrometers]

For determining the specific gravity, a hydrometer is used. This consists of a small sealed glass tube with an air bulb and a quantity of shot at one end, and a graduated scale on the upper end. This scale is marked from 1.100 to 1.300, with various intermediate markings as shown in Fig. 33. If this hydrometer is placed in a liquid, it will sink to a certain depth. In so doing, it will displace a certain volume of the electrolyte, and when it comes to rest, the volume displaced will just be equal to the weight of the hydrometer. It will therefore sink farther in a light liquid than in a heavy one, since it will require a greater volume of the light liquid to equal the weight of the hydrometer. The top mark on the hydrometer scale is therefore 1.100 and the bottom one 1.300. Some hydrometers are not marked with figures that indicate the specific gravity, but are marked with the words "Charged," "Half Charged," "Discharged," or "Full," "Half Full," "Empty," in place of the figures.

The tube must be held in a vertical position, Fig. 35, and the stem of the hydrometer must be vertical. The reading will be the number on the stem at the surface of the electrolyte in the tube, Fig. 36. Thus if the hydrometer sinks in the electrolyte until the electrolyte comes up to the 1.150 mark on the stem, the specific gravity is 1.150.

[Fig. 35 Using hydrometer for reading specific gravity]

For convenience in automobile work, the hydrometer is enclosed in a large tube of glass or other transparent, acid proof material, having a short length of rubber tubing at its lower end, and a large rubber bulb at the upper end. The combination is called a hydrometer-syringe, or simply hydrometer. See Figure 34. In measuring the specific gravity of the electrolyte, the vent cap is removed, the bulb is squeezed (so as to expel the air from it), and the rubber tubing inserted in the hole from which the cap was removed. The pressure on the bulb is now released, and electrolyte is drawn up into the glass tube. The rubber tubing on the hydrometer should not be withdrawn from the cell. When a sufficient amount of electrolyte has entered the tube, the hydrometer will float. In taking a reading, there should be no pressure on the bulb, and the hydrometer should be floating freely and not touching the walls of the tube. The tube must not be so full of electrolyte that the upper end of the hydrometer strikes any part of the bulb.

The tube must be held in a vertical position, Fig. 35, and the stem of the hydrometer must be vertical. The reading will be the number on the stem at the surface of the electrolyte in the tube, Fig. 36. Thus if the hydrometer sinks in the electrolyte until the electrolyte comes up to the 1.150 mark on the stem, the specific gravity is 1.150.

If the battery is located in such a position that it is impossible to hold the hydrometer straight up, the rubber tube may be Pinched shut with the fingers, after a sufficient quantity of electrolyte has been drawn from the cell and the hydrometer then removed and held in a vertical position.

Specific gravity readings should never be taken soon after distilled water has been added to the battery. The water and electrolyte do not mix immediately, and such readings will give misleading results. The battery should be charged several hours before the readings are taken. It is a good plan to take a specific gravity reading before adding any water, since accurate results can also be obtained in this way.

[Fig. 36 Hydrometer reading showing cell charged, half-charged, and discharged]

Having taken a reading, the bulb is squeezed so as to return the electrolyte to the cell.

Care should be taken not to spill the electrolyte from the hydrometer syringe when testing the gravity. Such moisture on top of the cells tends to cause a short circuit between the terminals and to discharge the battery.

In making tests with the hydrometer, the electrolyte should always be returned to the same cell from which it was drawn.

Failure to do this will finally result in an increased proportion of acid in one cell and a deficiency of acid in others.

The specific gravity of all cells of a battery should rise and fall together, as the cells are usually connected in series so that the same current passes through each cell both on charge and discharge.

If one cell of a battery shows a specific gravity which is decidedly lower than that of the other cells in series with it, and if this difference gradually increases, the cell showing the lower gravity has internal trouble. This probably consists of a short circuit, and the battery should be opened for inspection. If the electrolyte in this cell falls faster than that of the other cells, a leaky jar is indicated. The various cells should have specific gravities within fifteen points of each other, such as 1.260 and 1.275.

If the entire battery shows a specific gravity below 1.200, it is not receiving enough charge to replace the energy used in starting the engine and supplying current to the lights, or else there is trouble in the battery. Use starter and lights sparingly until the specific gravity comes up to 1.280-1.300. If the specific gravity is less than 1.150 remove the battery from the car and charge it on the charging bench, as explained later. The troubles which cause low gravity are given on pages 321 and 322.

It is often difficult to determine what charging current should be delivered by the generator. Some generators operate at a constant voltage slightly higher than that of the fully charged battery, and the charging current will change, being higher for a discharged battery than for one that is almost or fully charged. Other generators deliver a constant current which is the same regardless of the battery's condition.

In the constant voltage type of generator, the charging current automatically adjusts itself to the condition of the battery. In the constant current type, the generator current remains constant, and the voltage changes somewhat to keep the current constant. Individual cases often require that another current value be used. In this case, the output of the generator must be changed. With most generators, a current regulating device is used which may be adjusted so as to give a fairly wide range of current, the exact value chosen being the result of a study of driving conditions and of several trials. The charging current should never be made so high that the temperature of the electrolyte in the battery remains above 90° F. A special thermometer is very useful in determining the temperature. See Fig. 37. The thermometer bulb is immersed in the electrolyte above the plates through the filler hole in the tops of the cells.

Batteries used on some of the older cars are divided into two or more sections which are connected in parallel while the engine is running, and in such cases the cables leading to the different sections should all be of exactly the same length, and the contacts in the switch which connect these sections in parallel should all be clean and tight. If cables of unequal length are used, or if some of the switch contacts are loose and dirty, the sections will not receive equal charging currents, because the resistances of the charging circuits will not be equal. The section having the greatest resistance in its circuit will receive the least amount of charge, and will show lower specific gravity readings than for other sections. In a multiple section battery, there is therefore a tendency for the various sections to receive unequal charges, and for one or more sections to run down continually. An ammeter should be attached with the engine running and the battery charging, first to one section and then to each of the others in turn. The ammeter should be inserted and removed from the circuit while the engine remains running and all conditions must be exactly the same; otherwise the comparative results will not give reliable indications. It would be better still to use two ammeters at the same time, one on each section of the battery. In case the amperage of charge should differ by more than 10% between any two sections, the section receiving the low charge rate should be examined for proper height of electrolyte, for the condition of its terminals and its connections at the starting switch, as described. Should a section have suffered considerably from such lack of charge, its voltage will probably have been lowered. With all connections made tight and clean and with the liquid at the proper height in each cell, this section may automatically receive a higher charge until it is brought back to normal. This high charge results from the comparatively low voltage of the section affected.

In case the car is equipped with such a battery, each section must carry its proper fraction of the load and with lamps turned on or other electrical devices in operation the flow from the several sections must be the same for each one. An examination should be made to see that no additional lamps, such as trouble lamps or body lamps, have been attached on one side of the battery, also that the horn and other accessories are so connected that they draw from all sections at once.

Some starting systems have in the past not been designed carefully in this respect, one section of the battery having longer cables attached to it than the others. In such systems it is impossible for these sections to receive as much charging current as others, even though all connections and switches are in good condition. In other systems, all the cells of the battery are in series, and therefore must receive the same charging current, but have lighting wires attached to it at intermediate points, thus dividing the battery into sections for the lighting circuits. If the currents taken by these circuits are not equal, the battery section supplying the heavier current will run d