The key is to find where the problem is. There is a simple way to see whether you have a problem with your battery charging system. Remember when you turn the ignition key, there are two stops: stop I -power electrical system and fuel pump, and stop II-start engine. When you turn the key to stop I, you should see several lights on from the instrument panel (including battery light). That indicates battery charging testing system is working. Once you start the engine (and it is running), the battery light should go off which indicates battery charging system is working fine. Have you see any light on when the engine is running? If the changing system is fault, there are three possibilities: bad battery, alternator or regulator (which controls power flow to the battery).