The charging system keeps a charge in your battery and provides electrical energy for the radio, lights and other features while the car is running. The modern charging system consists of the alternator, battery, wiring and electronic control unit (ECU). Older cars may have a regulator, but in newer cars, that is now part of the car's computer.
The alternator creates electrical power to run accessories and recharge the battery. It turns mechanical energy from the car's crankshaft into electrical energy.
The computer (or in older cars, the regulator) acts as a "traffic cop" to control the alternator's output. It senses when the battery needs charging or when the demand for electricity changes.
The battery is a reservoir of electrical power. Its biggest job is to crank the engine to start the car. The battery also supplies power to the accessories when the engine isn't running.
If something is not right with the charging system, you'll see a warning light. The warning light may be labeled "Gen", "Bat" or "Alt". If this warning lamp lights up while the engine is running, it means that there is a problem in the charging system, usually that the battery has gone bad or the alternator has stopped working.
Sometimes if your car or truck won't start, you have a bad battery, one that can't hold a charge. Sometimes it means you left a light or other accessory on, and it drained the battery. And sometimes the problem is really that the alternator isn't filling it up with new energy. Not sure what the issue is? A free inspection at any of our stores is the place to start.
ref link- http://m.bigotires.com/article-detail/What-is-the-battery-charging-system
