Can I make a 3 hour drive if the battery is not being charged at all? The battery would be fully charged before I take off.

I would not dare try that drive. But if you do not use any electric power (ie a/c, lights, windows) and you have some one jump you of to start the car you probably will get an hour out of it being that the car naturally uses power for the idrive and other systems. I once made it two hours on a charge in my 98 accord but then again it doesnt have nearly as many systems as a BMW