Fig. 1,116.—Four Edison cells (type A-4) in wooden tray.

Ques. What indicates the completion of a charge?

Ans. When a cell is fully charged the electrolyte apparently boils and gives off gas freely. The completion of a charge may be determined by the voltmeter, which will show whether the normal pressure has been attained.

Ques. How should the voltage be regulated during the first charge?

Ans. It should be allowed to rise somewhat above the point of normal pressure.

Electrical Data Edison Cell
B-2B-4B-6
Normal output, ampere hours4080120
Maximum output, ampere hours4895142
Normal rate of discharge, amperes for five hours81624
Average voltage on normal discharge1.21.21.2
Normal rate of charge, amperes for seven hours8 16 24
Maximum rate of "boosting charge" (for short time only)50 100 140
Length of containing can (determined by number of plates)1½2⅝313/16
Width of containing can5⅛5⅛5⅛
Height " " "715/16713/167¾
Height over all8¾8¾8⅞
Weight of each cell alone, lbs.4.67.410.5
Average weight per cell of battery, assembled in trays5.58.711.8

Fig. 1,117.—Cell of Edison storage battery. The jar or container is of nickel plated sheet steel with welded seams; the walls are corrugated to give strength. The cell cover, of sheet steel, has four mountings, two being pockets to contain stuffing boxes about the terminal posts. One of the other two is a separator which separates spray from the escaping gas while the battery is charging. The fourth mounting is for filling with electrolyte. The electrolyte consists of a 21% solution of potash in distilled water with a small per cent. of lithia. The density of the electrolyte does not change on charge or discharge.

Ques. How often should a battery be charged?

Ans. At least once in two weeks, even if the use be only slight in proportion to the output capacity.

In charging a storage battery, it is essential to remember the fact that the normal charging rate is in proportion to the voltage of the battery.