How To Jump-Start a Car Using Jumper Cables Safely

Updated: Mar. 21, 2024

Learn how to jumpstart a car safely. Follow these four simple steps to make good, safe connections and jump a car.

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I grew up with a dad who made sure that when he taught me to drive, the lessons included things like oil and filter changes, tire patching and changing and, of course, how to jump-start a dead battery. "You'll need every single one of these skills at some point in your driving career, Robert," he often said.

Nearly two decades later, I can confirm he was right. I hadn't been driving on my own for long when I had my first dead battery experience. I was parked in my dad's 1990 Ford F150 and was approached by a worried-looking man. He sheepishly asked if I could give his dead SUV battery a boost. I was a little nervous, since I had never boosted a vehicle without dad looking over my shoulder. Thankfully, I remembered how to do everything safely, and five minutes later the man pulled away and with a look of gratitude.

Before we get to the how-to steps, it's worth noting that as useful as jumper cables are, they're not the only way to boost a dead car battery. In fact, they're not even the best way. Portable battery boosters do the same job as cables, but more conveniently because they don't require another vehicle. That's why I carry both jumper cables and a fully charged battery booster in my vehicle at all times.

When To Call a Pro

Call in a professional if you're trying to boost a dead vehicle battery and nothing happens. But first, double check you've done everything right and that the connections of the cables to the battery terminals are solid. If everything checks out and the dead vehicle still isn't turning over, you'll need some outside help.

Another reason to call a pro is if the vehicle being boosted has a battery that's hard to access. I've seen some modern vehicles with the air filter housing installed right above the battery, making it nearly impossible to reach or even see one or both terminals. In this situation parts would need to be removed to get at the battery, and that's best left to a pro.

Time: 5-15 minutes

Cost: $20 (if you don't already own jumper cables)

Complexity: Simple

Project step-by-step (5)

Step 1

Park an operational vehicle near the one being boosted

  • Find a vehicle that’s running normally, then park it close to the vehicle with the dead battery.
  • Be sure to park with the front of the operational vehicle close enough to the front of the dead vehicle so your jumper cables can reach between the two. This could be nose-to-nose, or with one vehicle beside the other facing the same direction.
  • Lift the hoods of both vehicles.

Park Vehicle side by sideRobert Maxwell for Family Handyman

Step 2

Prepare to boost the dead vehicle

  • Ensure both vehicles have 12-volt batteries by examining their labels. This isn’t a huge concern, because all modern vehicles come with 12-volt batteries, with only some antique vehicles using a 6-volt system If you happen to come across an antique vehicle with a flat battery, call in a pro.
  • Put on eye protection and safety gloves (either natural rubber rated for electrical work or the fabric safety gloves that sometimes come with jumper cables), then inspect both terminals on each battery, using a small wire brush to remove any dirt or debris you find.
  • Inspect the terminals of both batteries and determine which are negative and which are positive. Look for + and – signs on the battery casing next to each terminal.

Prepare To BoostRobert Maxwell for Family Handyman

Step 3

Connect the jumper cables

  • Be aware that the orientation in which you connect your jumper cables to the vehicle batteries is very important. Connecting the two sets of battery terminals together wrong could cause a dead short (an electrical circuit with lots of amperage but very little resistance), cause sparking, melt your jumper cables and possibly damage [the batteries and electronic systems of both vehicles.
  • Clamp the red side of your jumper cables to the positive battery terminal of the vehicle doing the boosting. Jiggle the cable clamp slightly as you attach it to the terminal to ensure it’s settled and has a good grip.
  • Clamp the other end of the red side of your jumper cables to the positive terminal on the vehicle being boosted.
  • Clamp the black end of your jumper cables to the negative terminal of the vehicle being boosted.
  • Clamp the other black end of your cables to the negative terminal of the vehicle doing the boosting.

Connect Jumper CablesRobert Maxwell for Family Handyman

Note: Some people say you shouldn’t connect the cable directly to the negative terminal of the weak battery for safety reasons. In practice, I’ve always connected directly to the terminal and never had an issue. I’ve also spoken with multiple professional mechanics who do the same, and have for decades without incident. The potential risk is incredibly small, and some serious difficulties can arise when trying the recommended alternative of finding a prominent part of the metal vehicle frame to connect the negative cable to instead.

Step 4

Jump-start the dead vehicle

  • Double-check that your jumper cable connections are all solid, then start up the operational vehicle.
  • Wait several seconds, then attempt to start the dead vehicle. If it partially turns over but doesn’t start, wait 10 minutes then try again. If a dead battery was the problem, it should start up no problem.

Jump start the dead vehicleRobert Maxwell for Family Handyman

Step 5

Disconnect the jumper cables

  • Get ready to disconnect your jumper cables once both vehicles are running.
  • Disconnect the black clamp from the negative terminal of the battery being boosted, then disconnect the other black clamp from the negative terminal of the vehicle doing the boosting.
  • Disconnect the red cable in the same way, beginning with the vehicle you’ve just boosted, then the other vehicle.
  • Close the hoods of both vehicles and put away your jumper cables.

Disconnect the jumper CablesRobert Maxwell for Family Handyman