Car battery function.
The electrical system of cars with internal combustion engines consists of two sources of electricity: battery and generator. If the installations are operational, these sources perform functions alternately, i.e. they do not simultaneously supply energy to the electrical circuits. When the engine is not running or the crankshaft speed is too low, to excite the generator, the battery supplies electricity to all receivers connected to the circuit. When the engine starts, the current required to power the starter motor and this part of the electrical circuit is drawn, where high voltage is generated (ignition system) necessary to create a spark on the candles. When the engine starts, but the driver does not start driving yet, engine crankshaft speed is usually too low, generator to take over the function of the power source, especially direct current (komutatorowa). When an AC generator is installed in the car (alternator), the relatively low engine idling speed is sufficient, that it supplies the electrical system with sufficient energy at least to power the ignition system. When the battery ceases to function as a power source, becomes its receiver, i.e. begins to be charged with the current generated by the generator.
In installation, where the commutator generator is located, it takes over the function of a power source practically instantaneously, when the vehicle starts driving (engine crankshaft speed increases). The driver is constantly informed about the nature of the battery operation (source - receiver), because the battery charging indicator is mounted on the instrument panel of each car (most often a red control and signaling lamp). Its glow indicates, that the energy to power the vehicle's electrical circuits is taken from the battery. When it goes out, means, that the battery is starting to charge.