While many people know what the battery does in a modern automobile, very few people ever give a second thought to their vehicle's alternator. The alternator converts the engine's power into a usable form which which is constantly introduced into the vehicle's battery. This energy is used to power the radio, heater and other essential electronic components. The alternator consists of a few major components, including the rotor, the stator and the diodes which actually convert the current.
An alternator works by converting the mechanical kinetic energy created by the engine. Because the alternator is connected to the vehicle's engine by a belt, the motion of the engine also turns the parts of the alternator, generating power for the vehicle. The engine's crankshaft turns the belt, which is connected to the rotor shaft on the alternator. The alternator contains several diodes, as well as a voltage regulator. As the rotor spins, it rotates past wire coils. These coils are wrapped around a solid iron core. This movement of copper coils around and iron core creates electromagnetic current which is fed into a series of diodes. Since diodes allow current to pass in only one direction, the AC current produced by the alternator is converted into usable DC current which can be accepted by the vehicle's battery.
A voltage regulator is attached to the alternator to ensure that the stream of power is both constant and lacks the surges that are typically caused by electromagnetic power generation. A voltage spike that is too large can severely damage the vehicle's battery, so the regulator controls the amount of energy that can pass into the battery at any given point. The regulator senses changes in in the amount of energy reaching the battery and either blocks or allows more power through from the alternator to compensate. When there is a drop in battery power, the regulator senses this and permits more of the current to reach the battery. The amount of current produced by the alternator varies very little. Only the amount of current allowed to reach the battery varies. In theory, it's possible to run a vehicle without the battery once the engine has been started, since once the engine is in motion the power is self-sustaining, but without the battery the power created by the alternator may be too strong and could severely damage the vehicle's electronics.
