Ans. The danger to be avoided in rapidly charging a cell is its tendency to heat.
Ques. What apparatus is necessary in charging a battery?
Ans. The battery may be charged from direct current mains having the proper voltage. A current as near uniform as possible is required, and existing conditions must be met in each separate case. Sometimes a motor dynamo set with a regulating switchboard is used. Such an apparatus consists of a direct current dynamo, driven direct from the shaft of a motor, which, in turn, is energized by current from the line circuit.
With a direct current on the line, a direct current dynamo may be used; but with an alternating current an induction motor is required. The speed of the motor is governed by a rheostat, and the output of the dynamo is thus regulated as desired.
Charging Through the Night.—If an electric vehicle, after a late evening run, is to be used in the morning, the battery may be charged during the night without an attendant being present; but in doing this great care must be taken not to excessively overcharge.
A careful estimate of the amount of current required should be made and the rate of charge based on this estimate.
If, say, 72 ampere hours be required to recharge, and the time available is nine hours, the average rate of charge must be 8 amperes.
If charging from a 110-volt circuit, the rate at the start should be about 10 amperes; if from a 500-volt circuit, about 9 amperes; as, in charging from a source with constant voltage, such as a lightning or trolley circuit, the rate into the battery will fall as the charge progresses. This also applies if the charging be done from a mercury arc rectifier without attendance.
Ques. What precautions should be taken in charging a battery out of a vehicle?
