What happens if you connect the positive to negative while jumping your car?

This is a very dangerous situation and should be avoided at all costs. Connecting the positive terminal of one battery to the negative terminal of the other battery (or vice versa) can cause a dangerous electrical short circuit. This can cause both batteries to overheat and explode and could also cause a fire in the vehicles involved. In addition, the sudden surge of electricity can damage the electrical components in both vehicles and can even cause bodily injury.

To prevent this from happening, it's important to always double-check the connections before starting the jump. Make sure that the positive terminal of the good battery is connected to the positive terminal of the dead battery, and that the negative terminal of the good battery is connected to a metal part on the frame of the dead vehicle (not the negative terminal of the battery).

If you do accidentally connect the positive and negative terminals, immediately disconnect the jumper cables and do not attempt to start the vehicles. Allow both batteries to cool down for at least 30 minutes before attempting to jump the vehicle again.