A car battery is powerful, containing 12 volts of electricity. The human body can handle this level of voltage. The danger of shock and spark when handling a car battery results from the metal objects, including tools and jewelry, that come into contact with the terminals. Metal acts as a conduit for the voltage to pass from one terminal to another, to other parts of the car or to you. Wrapping black electrical tape around a wrench, except for the gripping end, will help diffuse some of this voltage.
Turn off the vehicle and open the hood.
Remove any metal accessories that could accidentally touch the battery cables. This includes necklaces, rings, bracelets or watches. If these metals contact the cables, it could create a spark or shock.
Throw an old blanket, towel or other cloth over the area of the fender that you will lean over to access the battery. This will keep any battery acid from leaking on the vehicle.
Remove the negative (black) terminal with a wrench first. Many metal wrenches are long enough to make contact between the positive and negative terminals when held horizontally. To avoid an accidental spark, hold the wrench as far away from the positive (red) terminal as possible, and remove the negative terminal first. Since the negative terminal contains the same voltage as the rest of the car, if you accidentally touch other parts of the car, no spark will result.
Remove the positive (red) terminal with the wrench last. The positive terminal contains 12 volts of electricity. If this terminal was removed first, and the wrench accidentally touched other surfaces of the car, it would arc 12 volts of electricity to the vehicle, which would cause a spark.
