1988 BMW 118d • 6 cylinder •

Engine is running, when I disconnect the negative terminal from the battery, the engine is still running. But when I disconnect the positive terminal from the battery, suddenly the engine is stop.
In a normal condition when the engine is running, even if I remove the battery from the car must be the engine continue running because of alternator give power to the engine.
April 2, 2011.

Yes, the alternator will support the electrical system.