Related Terms • Alternator • Ampere • Charging System

Definition: The battery is a storehouse of electrical energy for starting the engine. All cars and light trucks today have a 12-volt battery. Most are also maintenance-free, meaning you don't have to add water to them periodically. Some even have built-in charge indicators to tell you if they need charging. A green dot in the window means the battery is at least 75% charged, no dot means it needs recharging, and a clear or yellow window means you need a new battery because the water level inside is low. Don't try to jump start or charge such a battery. You might be able to salvage the battery if you can pry the sealed caps open and add water, but usually the battery must be replaced. Batteries are rated according to their Cold Cranking Amp (CCA) capacity. As a rule of thumb, an engine needs a minimum of one CCA for every cubic inch of displacement, and preferably two. The higher the CCA rating of the battery, the better. A typical passenger car battery might be rated at 500 CCA or higher.

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Electrical Troubleshooting: Part 2
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The Charging System - Part 2: The Alternator
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