Ans. When a battery is taken down the electrolyte may be saved and used when re-assembling the battery, providing great care be exercised when pouring it out of the jar, so as not to draw off with it any of the sediment. It should be stored in convenient receptacles, preferably carboys, which have been thoroughly washed and never used for any other purpose.
Fig. 1,091.—Phantom view of an "Exide" sparking or ignition battery. It contains three cells. In this type, the terminal lug has been designed to obviate the creeping of the electrolyte with its accompanying corrosion. The positive and negative terminals are for identification.
The electrolyte saved in this manner will not, however, be sufficient to refill the battery, and as some new electrolyte will be required, in general it is recommended that the old supply be thrown away and all new electrolyte (1.200 specific gravity) be used when re-assembling.
Voltage of a Secondary Cell.—This depends on the density of the electrolyte, the character of the electrodes and condition of the cell; it is independent of the size of the cell.
The voltage of a lead sulphuric acid cell when being charged is from 2 to 2.5 volts. While the cell is being discharged, it decreases from 2 to 1.7 volts. The voltage due to the density of the electrolyte may be calculated from the following formula:
V = 1.85 + .917 (S - s)
in which
V = voltage;
S = specific gravity of the electrotype;
s = specific gravity of water at the temperature of observation.