Consumers are connected to the positive power source by a wire, and to the negative power source - through the car body (ground). This method allows to reduce the number of wires and simplify installation.
Low-maintenance or maintenance-free batteries are installed on cars.
The electrical system has a twelve-volt supply with negative ground and consists of a battery, generator, starter, electrical consumers and electrical circuits.
The battery is charged by a generator, which is driven by a belt from the crankshaft pulley.
The starter is a DC motor with compound excitation and an electromagnetic traction relay. When the engine is started, the traction relay moves the pinion into engagement with the flywheel ring gear before the starter receives power from the battery. After the engine is started, the freewheel clutch disconnects the starter armature from the flywheel ring gear.
Precautions
When working on the electrical system, to avoid damaging semiconductor devices (diodes and transistors) the following requirements must be met:
- do not disconnect the battery, alternator or any electrical connectors while the engine is running;
- when performing any work, remove the negative terminal from the battery;
- when performing electric welding work on a vehicle, turn off the alternator and electronic control device;
- do not allow the engine to run with the generator disconnected from the electrical system;
- do not check the generator's functionality by shorting its output contacts to ground.