Engine starting or running at low speed, as a result of automobile generator or not hair bai electricity voltage is very low, starter, ignition system, and at this time the car need electricity, electrical equipment all by battery supply, normal operation of the engine, generator to the vehicle power supply, electrical equipment for battery charging at the same time, when the automobile electrical equipment power consumption is too large, more than the generator power supply, battery supply power to the car electrical equipment together with the generator.

At the same time, the battery is also a large capacity capacitor, which can absorb the instantaneous high voltage generated in the circuit of the car, thus protecting the electrical equipment in the car. Automotive battery is the important component parts, if have no battery, the vehicle even the normal starting difficulties, not only can provide electricity for vehicles, battery can store electricity, this is the origin of the name of the storage battery, power supply "and" battery "corresponding battery recharge and discharge process, battery belong to dc power supply.