MUCH-ABUSED BATTERIES

Press, Volume LXX, Issue 21179, 1 June 1934, Page 6

MUCH-ABUSED BATTERIES

ACTION OF IMPORTANT UNIT kuminatim; common TKOriiLKS A. unit which is very important to tlie satisfactory operation of the automobile is the starting, lighting and ignition battery, and yet, because its construction is little understood, it is a much abused, much neglected, piece of apparatus, the useful life and efficiency of which could be greatly increased by attention to a few precautions. If two dissimilar materials (usually metals), both conductors of electricity are submerged in a liquid which acts chemically upon one of them, an electrical pressure is set up between ih'; two mel a Is. If these are then connected outside the liquid, a current of electricity will (low through the circuit consisting of the (wo metals, the outside connexion and the liquid. The electrical pressure or voltage between lie.; two metals depends upon the character of the materials used, while the amount of the current flowing is proportional to the areas of the surfaces acted upon. Action in Cells

Such a device is called an electric cell, the term battery being applied to a number of individual cells connected together. In each cell the metals acted upon are called the electrodes, the one from which the current llows being termed tlie positive ol< eliode, the one to which it return.'! the negative. The chemical used is called the electrolyte. As the current is produced by the liquid attacking one of the metal conductors or electrodes, the battery will continue to give out electricity until either the chemical is exhausted or one or both of the electrodes are either consumed, or, i:i the case of' the "storage'' battery, changed into another chemical compound. When the latter operation has developed it is possible to reverse the operation by sending a current of electricity through the battery in a direction opposite to the flow of the current, which was produced by the chemical action, thereby bringing the electrode and liquid back to their original composition and condition. In other words, sending a current through the so-called storage battery simply puts the metals and chemical hack into a condition to promote chemical action which in turn will produce electrical energy. The Storage Battery In the storage battery the electrodes are in the form of thin plates, a considerable number being employed in order to increase the amount of current. The plate on which the electrolyte has a chemical effect is made of a chemical combination of lead and oxygen, known as peroxide of lead, which is a brown material, supported in a lead framework or grid. The other group is made up of spongy lead which is also held in lead grids. The first group is the positive one from which the current flows, the other the negative to which it returns. The electrolyte or chemical in which the plates are submerged is a mixture of sulphuric acid and water. Much battery trouble results from the fact that with mis-use some of the lead sulphate becomes irreducible by recharging and then cannot be broken up by the current. Hence, if the battery is not kept fully charged, its capacity may be reduced by this formation. This also occurs when the upper ends of the plate are not covered with solution. As the water in the solution is evaporated this necessitates its regular replenishment. The use of water free from any chemical compounds is also essential, because these set up chemical actions which interfere with the normal action of the electrodes —hence the need for using distilled water for filling batteries. Danger of Jarring Excessive jarring on the battery shakes the active material from the plates and may cause short circuits due. to the accumulation of deposit in the bottom of the jars until it touches both plates. Broken or defective separators between the plates will have the same effect. Any dirt accumulations on the outside of the battery are likely to cause a slow discharge of the battery. The need for keeping the battery clamped tightly in its container and for keeping it

clean externally will therefore be apparent. Loss of battery discharge capacity during cold weather is due to the fact that low temperatures retard all chemical action. With the storage battery the capacity at zero is only 50 per cent, of that at 80 degrees. This explains why a car may fail to start after standing several days in a cold garage, and emphasises the need for keeping the battery fully charged during cold weather.