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How to Use Jumper Cables

A jumper cable hooked up to the terminal of a car battery.

Dead batteries happen to the best of us, often at the worst of times. In these cases, you’re lucky if you have jumper cables and a friend or neighbor who can give you a boost. Otherwise, you’re going to be left asking a stranger to help and hoping that whomever you flag down is more prepared than you were. But do you know how to use jumper cables when the time comes to hook them up? Do you know what pitfalls to avoid and safety precautions to follow to keep you and your vehicle safe?

The SetupHow to Use Jumper Cables

Park the two vehicles facing each other if you can. Keep in mind that the jumper cables will have to reach from one battery to the other, and you’ll need to be clear of any surrounding hazards, such as traffic. Make sure both cars are in park with their engines off and parking brakes on.

The Hookup

Open the hood and locate the batteries or jumper connection points (check your owner’s manual). Each end of the cable has one black and one red clamp, generally corresponding to battery positive charges (red+) and battery negative charges (black-), but it’s always important to verify on the battery itself.

  1. Start by connecting the first red clamp to the positive terminal of the dead battery marked with a “+” or “pos” on the battery housing. Ensure good contact between the clamp and the terminal so it doesn’t pop off mid procedure and the electrons can get through to recharge.

  2. Next, connect the 2nd red clamp to the positive (+) terminal of the good battery. As before, ensure good contact, perhaps by giving it a wiggle to make sure it doesn’t immediately slip off.

  3. Connect the first black clamp to the negative (-) terminal of the good battery. Note that once you’ve got both sides of the jumper connected to a battery, it’s very important not to let the other two clamps come into contact with each other. If they do, they will short, creating potentially dangerous sparks.

  4. Lastly, connect the second black clamp to any unpainted metal surface of the vehicle with the dead battery that isn’t immediately next to the battery. Yes, the jump would work if it were connected to the negative terminal, but if the dead battery is emitting invisible flammable gasses, a spark arising from the connection could cause the battery to explode.

The Startup

Start the engine of the vehicle with the good battery and let it run for a few minutes at idle to get the dead battery charging. Then try to start the vehicle with the dead battery, but don’t force it for more than a few seconds or else you risk burning out the starter. You might have to be patient here. When the engine starts up, disconnect the clamps in the exact opposite order of how you hooked them up.

Once your vehicle is running, drive it for at least 20 minutes to give the alternator a chance to fully recharge the battery. And that’s it! Note, however, that unless you left a light on or the vehicle was sitting for a long time, your dead battery might be trying to tell you that you need a new battery or alternator, and it’s worth looking into that to avoid another incident.

Keeping an eye toward maintenance can help you prevent these surprises in the first place, but it’s best to be prepared with jumper cables of your own if you find yourself stranded.

Check out all the batteries, cables and related parts available on NAPA Online, or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on how to use jumper cables, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photos courtesy of Blair Lampe.


Blair Lampe View All

Blair Lampe is a New York-based professional mechanic, blogger, theater technician, and speechwriter.  In her downtime she enjoys backpacking wherever her boots will carry her, rock climbing, experimental theatre, a crisp rosé , and showering love on her 2001 Sierra truck.

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