WARNING
To avoid personal injury and/or vehicle damage, refer to the service precautions at the beginning of this section.
An automobile’s charging system provides electrical power for the operation of the ignition, starting system, and all electrical accessories. The battery serves as a storage device holding a supply of electricity and is regenerated by the generator when the engine is running. The generator is constantly in motion while the engine is running. To prevent too much energy from being stored in the battery the generator is equipped with a regulating device designed to read the amount of voltage in the battery and to turn itself on and off at specific times to maintain the proper charge. On newer vehicles, the computer also maintains a vigil on battery storage capacity activating the regulator when needed.
Storage batteries are a chemical device incorporating parallel lead plates in a tank containing a solution of sulfuric acid and water. Adjacent plates are dissimilar and the chemical reaction of the two dissimilar plates produces electrical energy. The chemical reaction is reversible, so that when the generator is producing current greater than that produced by the battery, electricity is forced into the battery, and the battery is returned to full charge.
The generator is belt driven by a pulley from the engine’s crankshaft. Generators actually produce alternating current (AC) commonly used in homes. As the current leaves the generator it is converted to direct current (DC) that is used by the storage battery, ignition and accessories. An generator contains a rotating field winding (or rotor), a stationary induction winding (or stator) and a diode assembly (or rectifier bridge). There is also a voltage regulator built into the generator and two internal fans to promote cooling to the circuits.
As the generator spins with engine rpm, two stationary carbon brushes ride on two rotating slip rings located at one end of the rotor. The rotor field winding is attached at either end to a slip ring permitting current to flow through the field winding. The regulator monitors the battery and stator voltage and changes the rotor field current to adjust generator output. The conversion of AC to DC is done by the Diode Rectifier Bridge. An alternating magnetic field is formed as the rotor assembly rotates within the stator winding. This spinning induces an AC voltage into the stator. Depending on the speed of the rotor and the magnetic field the voltage provided to the stator will vary.