WHY DOES MY CAR BATTERY KEEP DYING? HOW DOES MY CAR BATTERY WORK?The primary purpose of your car battery is to start your car. How does a car battery do that? It provides electricity to the spark plugs, which ignite the fuel that produces internal combustion in the engine. That's a lot to ask of a standard 12-volt battery, which is why it's crucial to ensure yours has enough juice to get the job done.Drained