THE BATTERY
When a battery is exhausted, or nearly so, it will not magnetize the core of the coil sufficiently to induce a current that will give a strong enough spark to ignite the mixture. The length of time that a battery should last, or the mileage that it should give, is learned from experience, and when it is exhausted in less time there is evidence that it has either been short-circuited or that the current has been used too extravagantly.
The extra source of current that should be provided should not be switched into circuit until the short circuit that exhausted the regular source has been located and removed, or there will be a further waste of current. It occasionally happens that through carelessness the battery is so connected that one of the cells is reversed, in which case the current will be reduced by the loss of the current from two cells, for the energy of the reversed cell will neutralize that of another. If both sets of battery have become exhausted by short circuit, current for further running may be obtained by connecting the two sets together in multiple, supposing that each set is, as is usual, connected in series.
An apparently exhausted dry battery will recuperate, or pick up, if allowed to stand, but a storage battery that shows 1.8 volts or less for each cell should be immediately recharged, for further use will cause fatal injury.