Jump-starting a car battery can cycle over 300 volts through the jumper cables and batteries. Connecting and disconnecting the cables in the proper order decreases the risk of damage or explosion. Always disconnect the negative clamps first.
Loose cables produce sparks when they touch metal parts of the car. Disconnecting the negative clamps first helps minimize the creation of sparks.
When all four connections are made, a large amount of volts is running through the circuit. By disconnecting the negative clamp from the dead car first, the circuit is broken. This minimizes the chance of sparking and explosion.
Disconnecting the cables in the wrong order can damage electrical equipment in the car. Anything plugged into the car is in danger of being damaged.
