Almost all drivers know that a car with a dead battery can be started by jumping it from a car with a charged battery. Automotive batteries are designed to produce the high electrical current required to start the engine. This routine procedure can become dangerous if the jumper cables are connected improperly — if the positive terminal on each battery is mistakenly connected to the negative terminal on the other battery. Damage will result from very high current flow, and possibly from incorrect polarity on the “dead battery” vehicle.
Damage to the Batteries
Connecting the positive terminal of each battery to the negative terminal of the other battery will result in a huge surge of electrical current between the two batteries.