Jumper cables are a gear you always want to have with you but hope you’ll never actually need to use. These cables can be a lifesaver when your battery is dead and your car won’t start, or when you get the chance to help out someone who’s been stranded by a bad battery.
Knowing how to use the cables appropriately and how to store them safely will make it that much easier to help both yourself and others out of a sticky situation.
You might have a hard time finding the battery under the hood of some vehicles. That’s because it may be in the trunk or, in the case of some SUVs, under the load floor in the cargo area. In these installations, you’ll likely find an access panel that lifts up over the positive terminal of the battery, alongside a ground terminal that might not be the actual battery ground itself. Your owner’s manual can help you find the battery as well.
Jumper cables, also called booster cables, seem pretty straightforward. The black alligator clamps connect to the negative ( – ) or ground on each vehicle, while the red alligator clamps connect to the positive ( + ) terminal on each car’s battery, completing the electric circuit between the two vehicles and allowing them to share the electricity needed to run the starter on the dead automobile. It’s not as simple as just connecting the clamps, however. With both vehicles off, you’ll want to use the following sequence:
1. Connect to the positive terminal on the good battery.
2. Connect the positive terminal on the bad battery.
3. Connect the negative terminal on the bad battery. Don’t connect the negative clamp to the good battery.
4. Look for an unpainted piece of metal in the engine bay to use as a ground, and clamp there instead — it will offer a better connection, without risking damage to the good battery.
5. Once clamped on, start the car with the good battery, let it idle for a minute and then crank the car with the dead battery for five seconds, or until it starts.
Wait a minute or two between each five-second pull to make sure you don’t drain the other vehicle’s electrical system. Jumper cables need to stay clean and free of corrosion to ensure they can transmit enough power to get a car started. Most cables come with a protective bag you can use to store them in your trunk, but it’s important not to get that bag wet and to clean off any dirt or rust that could form on the leads. Cables can corrode on the inside, too — this is harder to spot, but generally if you keep them dry you won’t have to worry.