The last thing you want to deal with is a dead battery in your BMW. Every car has a rechargeable battery that powers the headlights, cabin lights, and provides the means to start the car. It’s the first source of electrical current that enables the starter to begin the combustion process for your engine.

After that initial burst of electrical power from the battery, the alternator keeps the electrical systems working in your BMW. The alternator converts mechanical energy from the engine into electrical energy. The battery doesn’t have enough power to do that, but …