When you get in your car in the morning, you turn the ignition key and start the engine. Then, depending on the weather and daylight you may turn on your lights and windshield wipers. You turn on the heater fan, and then the radio; now you're ready to go.
None of this would happen without a car charging system. Accepted, you may be able to get your car started because of the battery, but if the component necessary to charge your battery and to run your electrics isn't working you won't get far before all the electrics stop working and your battery goes dead.
The component that does all this is known as the alternator. You start your car using energy from the battery, but as soon as the engines fires up, the alternator takes over all your electrics and charges your battery at the same time.
The alternator contains several coils of wire wrapped around a central spindle. Surrounding the spindle and attached to the internal casing are more coils of wire. There is a pulley on the front of the alternator spindle which a belt goes around; the belt also goes around another pulley wheel on the front of the engine. When the engine turns, the belt rotates the alternator spindle and an electric current is produced. This electric current feeds all your electrical items and charges the battery via an enormous of amount of wire; there are several miles of wires inside every car.
However, the speed your car engine rotates directly affects the speed the alternator turns. The faster the alternator turns the more electricity it produces. You car's electrical system is set to operate on about 12 volts; much more and the fuses will blow and you battery will get damaged; it could also overheat and explode.
To prevent any of this occurring, the electricity generated by the alternator is controlled by a device known as a voltage regulator. The regulator senses the amount of voltage being produced and maintains it at about 13 to 15 volts; it's slightly higher than the 12 volts your electrics need, because the wiring in your car creates resistance and therefore some of the voltage dissipates.
The voltage regulator constantly monitors the alternator output, keeping it at a safe level. However, when you car's engine is running at idle speed, perhaps at traffic signals, or in a traffic queue the alternator doesn't produce enough voltage to run all the electrical items. The voltage regulator senses the drop in voltage and switches to battery power so all you electrics keep working. As soon as the voltage increases due to an increase in engine speed, the voltage regulator switches back to the alternator to power your electrics. At the same time electricity flows to the battery to recharge any energy that it has used, thereby keeping your battery fully charged.
You alternator is a fairly simple device that will run for thousands of miles trouble-free, but it is essential to keeping your car running so if you ever see the red ignition light come on while you are driving, get your alternator checked very quickly, because it means it isn't producing electricity.