1. Charging System Fundamentals

2. Learning Objectives:
You will be able to explain the basic parts of a charging system
Explain the charging system operation using the correct terminology
Demonstrate basic troubleshooting on a charging system
You will be able to explain charging system indicators

3. Charging System Function
It recharges the battery after engine cranking or after the use of electrical accessories with the engine shut off.
It supplies the entire car’s electricity when the engine is running.
It provides a voltage output that is slightly higher than battery voltage.
It changes output to meet different electrical loads.

4. Types of charging systems
There are two basic charging systems: Alternator (A/C generator) system and (D/C generator) systems. Alternator charging (A/C) systems have replaced the older direct current (D/C) systems.
The D/C Generator
was fine for producing electricity on early model vehicles. However, today’s vehicles have more electrical components requiring high-current output.
A D/C generator would not be able to supply enough current for a modern vehicle at idle speed. The efficiency of a generator is poor at low engine speeds.

5. DC Generator

6. A/C Generator
It is smaller, lighter, and more dependable than a DC generator. The alternator will also produce more output at idle than a DC generator.
The alternator has a spinning magnetic field.

7. Alternator operation
The two main parts of a simplified alternator are the rotor and stator.
alternator rotor is located in the centre of the alternator housing. Two claw shaped pole pieces surround the field windings to increase magnetic field strength. It creates a rotating magnetic field. The alternator drive belt turns the rotor, making the field rotate.

8. Alternator Brushes
Alternator brushes ride on the slip rings to make a sliding electrical contact. The brushes feed battery current into the slip rings and rotor windings, creating an electro-magnet.

9. Alternator Stator
The stator consist of three groups of windings. The coils are wrapped around a soft laminated iron core.
The stator produces the electrical output of the alternator. The stator windings connect to the diode assembly.

10. Alternator Rectifier
A diode assemble commonly uses 6 diodes to convert stator output which is alternating current (AC) into direct current (DC). The rectifier diodes are mounted in a diode heat sink.

11. Alternator Fan
To provide cooling for the alternator, an alternator fan is mounted on the front of the rotor shaft.
This cools the windings and diodes to prevent overheating and damage. Normally the fan is located between the pulley and the front bearing.

12. Voltage Regulator
A voltage regulator controls alternator output by changing the amount of current flowing through the rotor windings.
Any change in rotor winding current changes the field strength acting on the stator.
The voltage regulator can maintain a preset charging voltage around 13.0 – 13.9 volts.

13. Voltage Regulator Styles
Internal Regulator External Regulator

14. Alternator Warning Light
An alternator warning light is wired into the charging system so that it will glow when alternator output drops to a specified level.
If a problem develops in the charging system, or the field current is trying to increase the alternator output, this will cause the indicator bulb to glow.