The alternator is good but it charge the battery?

The alternator charges the battery by converting the engine's mechanical energy into electrical energy. The alternator is driven by the engine's crankshaft, and the rotor is connected to the voltage regulator. The voltage regulator controls the amount of current that flows through the field windings, which in turn controls the output of the alternator. When the engine is running, the alternator produces electricity that flows to the battery. The battery stores this electricity and then supplies it to the vehicle's electrical systems when needed.