What is an alternator on an engine? What is it used for? Why is it important?

What is an engines charging alternator? What is it used for?

You might believe that the battery powers the electrics in your car, but that’s not actually true. The battery actually only provides the electricity to make the starter motor crank the engine, which should start the engine. In fact the engines alternator creates power when the engine is running to not only run any components on the engine, but also to put electrical charge back into the battery.

How does an alternator on an engine work?

The alternator on an engine is usually mounted on the block with bolts and maybe a bracket. In order to create the electrical energy needed, the alternator must be spun. The alternator is normally connected to the engines crank pulley by a rubber belt. As the engine rotated, the belts turn the alternators rotor inside the stator. Both the stator and rotor are made from wound copper and electrical steel. The rotor has an electrical current flowing through it which induced a magnetic field. This magnetic field creates a current in the alternators stator winding as it cuts through it. This AC current then needs to be rectified with diodes to create DC current like the battery holds and the engines electrical system requires. Generally engines use either 12 or 24 volts with smaller engines using the lower 12volts and larger engines using the higher 24V system.

Why is it important?

Without the engines alternator, the battery would very quickly run out of charge while the engine is running. Although cranking the engines takes a lot of current, it lasts a short period of time. The engine could be running for several days and all the electrical equipment on the engine will draw some power. Examples of items that may need to be powered are the ECU or ECM, sensors or the fuel solenoid. It may also have an electronic lift pump or electronic governor.

The alternator used to be called a generator, but that term is now normally reserved for petrol and diesel generators.