The Use of Distilled Water In the Upkeep of a Storage Battery

Poverty Bay Herald, Volume LXI, Issue 18467, 4 August 1934, Page 9

The Use of Distilled Water In the Upkeep of a Storage Battery

THE importance of replenishing tlie | the cells of the storage battery to compensate for the fall in tho level of the. electrolyte, or solution, in each cell is recognised by most car owners, but but sometimes mistakes are made which are, very harmful to £he battery. If the active material of the plates is exposed to the atmosphere not. only is the efficiency of the battery reduced in proportion to the degree of exposure, but the material on the plates will deteriorate rapidly. It is therefore essential that, in all circumstances, the solution should be kept well above'the tops of the plates, but the cells should not be refilled to such an extent that there is a risk of the solution leaking out through the vent boles of the filler plugs, thereby possibly causing some degree of shortcircuiting: between the lead lugs of the cells, as well as corroding the thimbles of the main terminals. The solution consists of a mixture of pure (distilled) water and chemically pure sulphuric acid, and if any foreign substance is inadvertently introduced its effects oil the plate material may ho disastrous. It might lie thought that, when it was necessary to refill the cells to make good the loss of the electrolyte. due to evaporation, a water-acid solution of the approved specific gravity should ho used. Actually, however, only distilled water should be employed, for tlie acid content doos not evaporate, and if more acid were added the right balance of the solution would he upset. As the cells discharge, the acid in the liquid combine with the active material of the plates to form lead sulphate, and the density or specific gravity of the electrolyte ir, consequently reduced.

It is for that reason that a batterytestingi hydrometer which registers the specific gravity of the solution enables a good 1 estimate to lie made as to tlie state of charge of the cells. But such readings are misleading if the electrolyte has been tampered with and extra, acid added. It is, for instance, quite possible to fake a weak battery, which is so badly sulphated or otherwise defective that it will not take a full charge, and by adding acid to raise the recorded specific gravity, although other electrical tests which can be carried out at any well-equipped service station would soon reveal its real condition. Tu ordinary service the only occasion when it is permissible to top-up the cells with fresh electrolyte instead of distilled water is when the solution lias been spill- 1 ed or has leaked away. In such cases the best course is to refer the matter to a dependable garageman who will bo able to supply new fluid of the correct density. j

Sometimes distilled water is not readily procurable, and country motorists might be ill a quandary, having to determine whether it is better to use supposedly pure water which has not been distilled, or to allow the tops of the plates to remain exposed. If the delay will nob be too long the latter course is probably the better.

: From a scientific standpoint no water from natural sources, is absolutely pure, and often the percentage of foreign ingredients is high. Any iron in the solution is peculiarly destructive. Although the water may have been drained from a slate or tile roof, or come from a, city simply which is noted for its purity, it will be quit© unsuitable because of having been stored in an iron tank or passed through iron mains. The nearest approach to the desired product is rain water, which has been trapped directly in a glass or glazed vessel after the rain has been falling long enough to bring down the dust and other impurities in tho atmosphere, and even then the. water is not as good 1 as when distilled.