Sparesbox Blog

How does a Car Alternator work?

By James Andrew

Tue Sep 29 2015

Even the most basic of vehicle electrical systems require substantial energy to operate. Even more so with today’s modern cars that are chocked full of electronic wizardry. Like anything that’s battery powered, eventually the battery will go flat. This is hardly ideal for cars that are required to travel tens of thousands of kilometres fault free, start each time you turn the key, and keep the occupants comfortable and safety with audio systems, air conditioning and electronic assists. Enter the Alternator.


Alternators Explained


An Alternator, for lack of a better comparison, is an onboard battery charger. It uses the turning motion of the engine to turn a rotor that is surrounded by metallic fingers with alternating magnetic poles. As the rotor spins it creates an electromagnetic field and produces a AC (Alternating Current) which is induced via the “stator windings”. Kilometres of wires wound around the entire unit.


AC creates a higher voltage that DC (Direct Current), but our vehicles cannot use AC, so the alternating current is moved through Diodes which acts as a one way valve, converting it to DC.
This DC current is then distributed by the Voltage Regulator, which controls the charge rate by controlling the initial supply voltage and into our battery. This effectively charges the vehicle battery as you drive.


Need to replace the Alternator in your car? Check out the huge range at Spares Box here: