Storage Battery Care and Maintenance.—Regularly once every week during the summer, and every two weeks during the winter, add water to each of the three cells of the battery, until the tops of the plates are covered. Use water only; never add acid of any kind. Water for battery purposes should be distilled fresh rain or melted ice, and must be free from alkali, iron, or other impurities. The battery should be kept clean and free from dirt. Use only clean non-metallic vessels for handling and storing water for battery purposes.
The state of charge of a battery is indicated by the specific gravity or density of the solution. [Fig. 103] shows a hydrometer syringe used for taking specific gravity readings. The filler or vent plug in the top of the cell is removed and the rubber tube of the hydrometer syringe inserted into the cell so that the end of the tube is below the solution. Then squeeze the rubber bulb slowly, drawing the solution into the acid chamber until the hydrometer floats.
Fig. 103. Hydrometer Syringe
The reading on the graduator stem at the point where it emerges from the solution is the specific gravity or density of the solution.
[Fig. 103] shows an enlarged section of the hydrometer floating so that the reading of the graduated scale is 1.280 at the point where it emerges from the solution. This is the specific gravity or density of the solution.
After testing, the solution must be returned to the cell from which it was taken.
Never take specific gravity readings immediately after adding water to the cells.
The specific gravity readings are expressed in “points,” thus the difference between 1.275 and 1.300 is 25 points.
When all the cells are in good condition the specific gravity will be approximately the same in all cells and the difference should not be greater than 25 to 30 points.