Signs of a Failing Battery

The easiest way to tell if a battery isn't performing at optimal levels is to attach a voltmeter to it to see whether or not it is holding a charge. The first sign most drivers will notice is it takes longer to start the vehicle, as the starter motor isn't receiving the appropriate amount of power to work efficiently. As the problem gets worse, it can cause numerous unpredictable issues as the battery actually begins to impede the electric flow through the various subsystems. Lights might dim unexpectedly, certain electric systems may stop working properly or become erratic, or fuses and relays can blow. Generally speaking, when electric components aren't working as they should, the battery is the first thing to test, followed by the alternator.