What Part Is Positive and Negative on a Jumper Cable? (with Video)

Dead car batteries can result from leaving the lights or radio on with the engine off. Knowing how to properly jump a battery is an imperative skill for any motorist. Jumper cables are designed to transfer electricity from one car's full battery to another car's dead battery in order to start the alternator, which will eventually recharge it. Jumper cables have both positive and negative leads, and knowing the difference between the two is necessary for successfully jump-start a vehicle.

Basics

The jumper cables are colored black and red. Red is positive and black is negative. Red is positive and black is negative. Each end has alligator clips made of copper that attach the leads of each car's battery. The black cable is the negative (-) part and the red cable is the positive (+) part. The two should never be confused and you may wish to mark the handles of each cable with a (-) or (+) sign.

Dangers

The two colors represent the respective polarities for the batteries' direct current system. Mixing the two up may cause the battery to short circuit and possibly even explode or lead to blown fuses or circuit boards. The leads of the car batteries' are typically color-coded to match the colors of the jumper cables.

Procedure

Both cars should initially be turned off. Connect the positive (red) clip of one end of the cable to the positive lead of the battery in the non-working car, then connect the negative (black) to the negative lead. Repeat this process with the working car using the same pattern. Start the working car, then attempt to start the non-working car until it successfully jump-starts. Disconnect the positive jumper cable clips first and the negative clips last.

Alternatives

There are several alternatives to using another car for jump-starting a dead car battery, but they use the same color-coding system. Portable battery chargers use cables that connect to your battery and use black as the negative color and red as the positive color. Some chargers use sensors to determine whether the polarity is correct and will not send electricity through the cables until it is fixed, avoiding potential damage to the car's electronics.