Failure of the alternator and failure of the battery are frequently confused. As it works with the engine, the alternator charges the battery within the vehicle. Charging the battery while the automobile is operating transforms the pulley's motion into electricity. A quick test can be used to determine which of them is failing. Disconnect the positive cable from the battery while the engine is running. If the automobile breaks down, you'll know the alternator is broken and isn't supplying power to the vehicle's electrical system.