Car Battery

What it does

Your car battery is a 12-volt power pack made of lead plates and acid that stores the electrical energy needed to spin the starter motor — which in turn cranks the engine. Once the engine is running, the alternator takes over and keeps the battery charged. Batteries fail because the lead plates corrode and the acid weakens over years of heat cycles. When the battery can no longer deliver enough current to spin the starter, all you hear is rapid clicking (insufficient current) or complete silence (battery totally dead).