How do you know if you have a bad alternator?
How can you tell if its the starter or the battery?
Your car starter has a really important job to perform – frequently. The battery sends a burst of energy to the start which uses this energy to turn the engine over and get it car started. If you put the key in the ignition, but only hear a click when you turn the key, you've got a problem with your starter.
What happens if you disconnect the battery while the car is still running?
If the engine's already running, disconnecting the battery will still keep the engine running. If you're trying to start a car without a battery or with a very dead battery, it won't start (even with push start in a manual car) because there's no electrical supply (spark) to the combustion chamber.