Somewhere, there has to be a freewheel on the motor setup or you would not be able to coast or peddle without the motor very well. I'm assuming you never found the controller in you setup........correct?

You do know a car battery is only 12v right? So you would need 2 of them. That's a hell of a lot of lead to carry around. In the old days when I first started ebiking I bout 4 12v 18ah batteries. Total weight 52 pounds. I get more power and distance from a single 24v 20ah lifepo4 pack now.

Bob