How car charging system work ?

A car charging system is used to provide electric current in all car conditions. When the car engine is off, the battery will be an electrical source for all-electric car's components. While the engine is run, the alternator will replace the battery function to provide electric energy.

A car charging system have several components: a battery, ignition switch, alternator, wiring harness, fuses, and charging warning light. For more detail about each function of these parts, you can read about car charging system components and functions I wrote before.

The alternator and the battery are the main components of the car charging system. The battery function is to keep the electric energy and use it when it's needed. The alternator provides electrical energy to use in all-electric car's components when the engine is running. At the same time, the alternator recharges the battery.

So, how do they work? In this post, I will give you some information about how a car charging system work. Here's how the car charging system work.

STAGE I: Ignition Switch to ON - engine stopped

The first state of car charging system work is ignition switch to ON position, but the engine is not running. As soon as the ignition switch is turned ON, the current flow (red lines) from the battery through the IG switch, charging lamp, rotor coil, transistor 1 (TR1) collector, transistor 2 (TR2) collector. See the current flow from the images of the simple charging system diagram below.

At the same time, the current flow (purple lines) through the L terminal on the voltage regulator to Base TR1 and Base TR2. The TR1 and TR2 transistors are activated when current flow to the Base on TR1 and TR2. The current (light blue lines) will flow to the ground.

As the current reach the ground, two conditions will happen:

• The charge warning lamp turns to ON
• The rotor coil being a magnet (with an electromagnetic principle)

STAGE 2: Ignition switch to ON - engine running, alternator output below the reference voltage

The next state of car charging system work is when the ignition switch to ON position and the engine is running. Still, the alternator output is below the reference voltage.

After starting the engine, the crankshaft pulley will drive the alternator pulley. In this condition, the rotor coil will rotate inside the stator coil. As the rotor coil (with electromagnet fields) rotates, the windings in the stator coil generate voltages. The current (yellow lines) flow from the rectifier (diodes) to the battery through the B terminal.

Because the voltage between the charge warning lamp wires is at the same value, the charging warning lamp will turn OFF. The electric current (light green lines) will flow through the rotor coil, TR1, TR2, Diode.

In front of the TR3 base, there is a Dz (Zener diode). The Zener diode works if the voltage source is higher than the voltage reference from the Zener diode. At this time, the voltage source is supplied from the stator coil.

Because the Zener diode is in the OFF position, the rotor coil is still an electromagnet, and the stator always produces voltages.

The longer time the rotor coil rotates will increase the voltage value in the stator coil. And now, the voltage produced by the stator coil can be used to charge the battery and provide the electric current to another car electric components to replace the battery function.

Read also:

• Alternator, how it works?
• How to check if your alternator is bad?
• Car alternator functions

STAGE 3: Ignition switch to ON - engine running, alternator output above referencevoltage

The longer time the rotor coil acts as a magnet, also increases the output voltage from the stator coil. When the output voltage is higher than the Zener diode voltage reference, it makes the Zener diode to ON and let the current (brown lines) flow to the base of TR3.

When the current flow to the base of TR3, it makes the TR3 switch ON. It stops the electric current (blue lines) tha flow to the base of TR1, and TR2. As the TR1 and TR2 are stopped to work, it makes the electric current (red lines) only flow from the L terminal to the ground. And also, when the TR1 and TR2 stop flowing electric currents, it makes the rotor coil lose its magnet (black lines).

If the rotor coil loses its magnet, the stator coil will stop producing the electric current. Then the voltage is decreased. When the voltage is decreased, the charging process will stop until the Zener diode start to OFF again.

The Zener diode holds an important function to control the electromagnetic field on the rotor coil. The charging will process if the Zener is OFF and the charging stops when the Zener is ON.