How Does an Alternator Recharge a Car Battery?

Posted on Sep 8, 2024

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Alternators in cars are called that because they generate alternating current (AC), which is then converted to direct current (DC) to charge the battery and power the vehicle’s electrical system.

Here’s how an alternator works to recharge the car battery:

The alternator is driven by a belt connected to the engine’s crankshaft pulley. As the engine runs, it spins the alternator.
Inside the alternator, a rotor spins within a stator. The rotor acts as an electromagnet, creating a magnetic field. As it spins, this magnetic field induces an alternating current (AC) in the stator windings.
The induced AC current is then passed through a rectifier, which converts it to direct current (DC). The rectifier uses diodes to allow current to flow in only one direction.
The rectified DC current is used to charge the car’s battery and power the electrical system. The battery provides the initial power to start the engine, but once running, the alternator takes over powering the electrical components and recharging the battery.
A voltage regulator controls the alternator’s output to maintain the proper charging voltage for the battery, typically between 13.5-14.5 volts.

So in summary, the alternator generates AC power which is converted to DC to keep the battery charged and power the car’s electrical loads while the engine is running. The name “alternator” refers to the fact that it generates alternating current.

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