THE BATTERY.

Putaruru Press, Volume VIII, Issue 368, 11 December 1930, Page 7

THE BATTERY.

TO GET EFFICIENCY. Care to be Taken. The storage battery may seem to be an insignificant unit of the autounobile, but on most of the presentday cars it is so important that its failure will mean the failure of the entire car. On those cars which defend on the storage battery for the current for the ignition system, if the battery be dead, the engine will be just as useless as if the petrol tank were empty. The storage battery consists of a number of cells, called accumulator cells, each cell being capable of yielding a current having a voltage of 2.1 Thus, if a six-volt battery is needed, the battery is made up of three cells, while, if twelve volts are needed, six cells are used. %Eaeh cell is made up of a jar, ' generally of hard rubber, in which are two sets of plates, positive and negative. These plates are made of lead, in the form of a grid. In the .grid of one set of plates a paste of grey, spongy lead is forced, while in the other set a paste of red oxide of lead is forced. The plates are then set together, so that there will be a grey plate, then red, then grey, etc., all the red plates being connected to a common binding post, and likewise the grey. The plates are kept from touching by made either of specially treated wood or porous

rubber, and are then placed in jars. The jars are then covered and sealed, and the plates of the various cells connected, the positive of one to the negative of the next. Thus the cells will be in series. When the battery is ready for service, a solution, called the electrolyte, made of a mixture of sulphuric acid and water, is then poured into the "cells, and an electric current sent into the battery. Chemical Action. As the current enters the battery the water of the electrolyte is decomposed into hydrogen and oxygen. The hydrogen will escape as a gas and the oxygen combine with the soft lead of negative plates, which lead will leave this plate and be deposited in the form of oxide of lead on the positive plates, until no more can be deposited. The battery is then' fully charged. Note that the hydrogen of the water escapes, but that the sulphuric acid is not affected. When the battery has been charged, if a circuit be made on the outside, the reverse chemical action will take place, and electric current flow from the battery. In this case the oxide of lead gives up its oxygen, which escapes as a gas, and the lead is deposited back on the soft-lead plates. Note that now the oxygen escapes, but that the sulphuric acid again is unaffected. The relation between the above chemical action and the flow of electricity is explained by what is known as the theory of ions. This theory

cannot be explained here, but notice how the water disappears, while the acid does not.

For this reason one of the most important things which must be done to the battery is to fill it with water regularly. The water used must be distilled, so as to be chemically pure. Filtered water will not do. Acid must never be added to the battery, even though it be years old. When the electrolyte is poured into the battery, the first thing that happens is that much of the acid is absorbed by the plates, but as the plates are charged they cannot hold so much of the acid by absorption, and so the acid goes back into the solution as the battery becomes charged. As the acid is much heavier than the water, the solution will be lighter when the battery is discharged and much of the acid has been absorbed out of the solution, and heavier when the battery is charged and the acid is back in the solution. This gives a means for seeing how well charged the battery is; namely, by seeing how heavy the electrolyte is. For this purpose a hydrometer is used. If some of the solution is drawn out of the battery with a syringe and the hydrometer put into it, the depth to which it sinks will indicate the weight of the electrolyte. A battery must never be left standing in a discharged state, as a coating will form on the plates, making it hard to charge them. For this reason, if the car is not used, the battery should be stored with a battery service station, where is can be charged periodically. An idle battery loses its charge. Charge and Discharge. A battery must not be charged or discharged too quickly, as this will generate heat and warp the plates.

On most cars the battery is charged at about a 10-ampere rate, which is the maximum safe charge. When the self-starter motor is used, however, a current of an amperage from 150 to 250 will flow, which will result in a very quick discharge. Therefore, if your engine does not start promptly, do not use the starter constantly, but stop and give the battery a rest: It would be well to find the reason for the slow starting, and, if the day be cold, to give -the engine a few preliminary turns by hand before switching on the ignition.

Note that when the starter is used the battery is discharged from fifteen to thirteen times as fast as it is charged when the engine is running. This means that it takes about thirty minutes of car driving at a fair speed to make up for the current used in one minute of starter use. From this you can judge if you are sending it back to the battery. Care must be taken to keep the top of the battery clean. Before filling with water it would be well to wipe the top of the battery before unscrewing the filler caps. If the smallest pieces of iron or copper, etc., get into the battery quite a portion of the plates will be coated with an iron or copper sulphate, and so be put out of service. It is advisable to rub the lead terminals with a cloth on which is some vaseline, as this will protect them from being corroded by any acid which might be spilled. In taking the battery out of the car or putting it back care should be taken to keep it in a vertical position. Some sediment may be in the bottom of the jars, and tipping them may cause this sediment to get between the plates and so short-circuit them.