The automotive storage battery is not capable of supplying the demands of the electrical system for an extended period of time. Every vehicle must be equipped with a means of replacing the current being drawn from the battery. A charging system is used to restore the electrical power to the battery that was used during engine starting. In addition, the charging system must be able to react quickly to high load demands required of the electrical system. It is the vehicle’s charging system that generates the current to operate all of the electrical accessories while the engine is running.
Two basic types of charging systems have been used. Hie first was a DC generator, which was discontinued in the 1960s. Since that time the AC generator has been the predominant charging device. The DC generator and the AC generator both use similar operating principles.
The purpose of the conventional charging system is to convert the mechanical energy of the engine into electrical energy to recharge the battery and run the electrical accessories. When the engine is first started, the battery supplies all the current required by the starting and ignition systems.
As the battery drain continues, and engine speed increases, the charging system is able to produce more voltage than the battery can deliver. When this occurs, the electrons from the charging device are able to flow in a reverse direction through the battery’s positive terminal. The charging device is now supplying the electrical system’s load requirements; the reserve electrons build up and recharge the battery.
FIGURE. Current flow when the charging system is operating.
If there is an increase in the electrical demand and a drop in the charging system’s output equal to the voltage of the battery, the battery and charging system work together to supply the required current.
The entire conventional charging system consists of the following components:
- Drive belt.
- Voltage regulator.
- Charge indicator (lamp or gauge).
- Ignition switch.
- Cables and wiring harness.
- Starter relay (some systems).
- Fusible link (some systems).
This chapter also covers the operation of the charging systems used on HEVs. The HEV can recharge the HV battery by running the engine and using the ISG or AC motors as generators. They can also use regenerative braking. To charge the auxiliary battery they may use a DC/DC converter.