Eli5. How do car batteries work? What do they do?

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Eli5. How do car batteries work? What do they do?

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They use a chemical reaction, almost always between lead and a strong acid, to generate electricity. That electricity is used to turn the starter motor when you turn the key to get the engine running. Once the engine is running a special generator (called an “alternator”) takes over generating electrical power for the car and charges the battery. During operation that electricity is used to run the radio, screens, instruments, etc. and also to fire the spark plugs that keep the engine going.

If you’re running stuff in your car with the engine off, like the radio or lights, the battery also does that. This is why, if you leave your lights on, your car won’t start…you ran the battery down powering the lights and now there’s nothing left to turn the starter.

Car batteries are just like any other battery. They store and discharge electrical power.

The most important function of a battery is starting the car. An engine can’t self-start; the crankshaft needs to start moving so that the engine can pull in fuel, and the battery also needs to energize the spark plug or glow plug that ignites it.

Additionally, the battery is needed to act as a stable voltage source for all of the car’s electronics.