Does the battery powers the vehicle or the alternator

I would say that the battery powers the vehicle, and the alternator keeps the battery charged. If the alternator stops working, the car will still run until the battery is out of juice. If the battery quits, the alternator will keep the car running until you shut it off, and then it will not start without addressing the battery or getting a jump start.

Good morning.

You are half right. The battery will keep the car running without the alternator working until the voltage goes below 12 volts.

The alternator will not keep the engine running when the battery is bad. The alternator needs at least 12 volts to activate the magnets inside to make the alternator work. When the battery goes dead, the voltage stops and the engine will only run until the magnets are out of voltage, then it will die. The alternator depends on battery voltage for it to work. No battery voltage, no alternator function.

Roy

Roy that is if the battery is totally completely shot. Usually a bad battery just will not hold charge, but is not a big enough draw to completely keep the alternator from doing its thing.