Why Does the Battery Cable Spark When Placed on a Post?

by Kristine Brite
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dead battery image by Katrina Miller from Fotolia.com

Batteries power a vehicle's starter and other electrical systems. The spark comes from the metal's reaction to the battery. If the cables are connected normally, sparking is not dangerous to people or the vehicle.

Electrical System

Items turned on in the car, such as the radio and clock, might have been turned on before the battery died. These items will attempt to draw power from the battery. This means the electrical system is drawing current, and the battery is part of that system. Sometimes this can cause the battery jumper cable to spark when it's connected to the battery post.

Cable Installation

The battery cables can spark if the cables are installed in the improper order. When attaching the battery cables, place the positive cable on first and then the ground cable. Do not allow the cables to touch on the free end not yet hooked into another battery while the cables are connected to the first battery. Also, the ground, or negative cable, should not be touching anything metal while the positive cable is hooked up.


Sparks from the battery cables present some dangers. The battery is filled with explosive gases. The spark could potentially light the gases, and the battery could explode. Also, anyone touching the cables could get shocked from touching them.

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