The physics in Back to the Future doesn't work either. How do you convert plutonium into electrical energy? You'd have to have a tiny nuclear reactor in the car. And as far as I know, a nuclear reactor would not generate a burst of 1.21 gigawatts. You'd need some kind of energy storage device.
Any nuclear physicists believe this power source is even theoretically possible? Or were the writers of Back to the Future just making sh!t up?