How to Jump Start a Car
Learn how to jump start a dead car battery safely with jumper cables. Step-by-step guide with the correct cable order.
We sat in a parking lot for 45 minutes once because our battery died and we did not know which cable went where. Someone eventually helped us, and the whole thing took about three minutes once we knew the order.
A dead battery is one of those things that feels like a crisis until you learn the fix. Then it is just a minor inconvenience. The process is straightforward, but the cable order matters. Connecting them wrong can damage electronics, blow a fuse, or in rare cases cause the battery to spark.
This guide covers the safe way to do it with regular jumper cables and a second car. Follow the cable order exactly and you will be driving again in about 15 minutes.
A set of jumper cables, which you should keep in your trunk at all times. Check them now and then, because clamps corrode and insulation cracks over time. You also need a second car with a working battery, parked close enough for the cables to reach between both batteries. That usually means nose to nose or side by side.
Position the cars and turn everything off
Park the working car close enough so the jumper cables can reach both batteries. This usually means nose to nose, about 18 inches apart. Put both cars in park with the parking brake engaged. Turn off both engines and all accessories, including lights, radio, and air conditioning. Pop both hoods and locate each battery. Most batteries are in the front of the engine bay, but some cars have them in the trunk or under a seat.
Connect the red cable to both positive terminals
Pick up the red (positive) jumper cable. Clamp one end to the positive terminal on the dead battery. The positive terminal is marked with a plus sign and usually has a red cap or cover. Then clamp the other end of the red cable to the positive terminal on the good battery. Make sure the clamps have a solid grip on the metal terminal. Loose connections will not transfer enough power.
Heads up: Never let the red and black clamp ends touch each other while connected to a battery. This creates a short circuit that can damage the electrical system, blow fuses, or cause sparks near the battery. Keep them separated at all times.
Connect the black cable carefully
Clamp one end of the black (negative) cable to the negative terminal on the good battery. The negative terminal is marked with a minus sign. Now here is the important part. Do NOT connect the other end to the negative terminal on the dead battery. Instead, clamp it to an unpainted metal surface on the dead car's engine block. A bolt, bracket, or metal strut works well. This prevents sparks near the battery where hydrogen gas can accumulate.
Good to know: Look for a bare metal bolt or bracket on the engine block away from the battery. Some cars have a designated grounding or jump-start point, and a few put the battery somewhere awkward. Your owner's manual shows where to connect, and AAA advises checking it before you attempt a jump.
Start the working car and wait
Start the working car and let it idle for 5 to 10 minutes, as AAA advises. This charges the dead battery enough to turn the starter motor. If the dead battery seems badly depleted (the dashboard lights did not come on at all when you tried to start it), hold the donor engine at a fast idle around 1,500 to 2,000 RPM. An alternator produces more current the faster its rotor spins, and at a normal idle it is putting out well below what it can. Light steady pressure is all it takes, and flooring it does not help.
Start the dead car
Try to start the dead car. If it turns over and starts, great. Let it idle for a few minutes before disconnecting anything. If it does not start, wait another three to five minutes with the working car running and try again. If it still does not start after two or three attempts, check that every clamp has a solid grip and try once more. If that fails, the battery may be too far gone and needs replacing, or the problem might not be the battery at all. A clicking sound with no engine turnover usually means the battery. Complete silence might mean the starter motor.
Disconnect cables in reverse order
Remove the cables in the exact reverse order you connected them. First, remove the black clamp from the engine block of the car that was dead. Then remove the black clamp from the good battery. Then remove the red clamp from the good battery. Finally, remove the red clamp from the previously dead battery. Drive the jump-started car for at least 30 minutes without turning it off, which is what AAA recommends. That is the alternator putting charge back in, and it does that faster at driving speed than sitting at idle.
Heads up: Do not turn off the jump-started car right away. The battery needs time to recharge from the alternator. If you turn it off within the first 30 minutes, it may not have enough charge to restart and you will need to jump it again.
That is the whole thing. A few minutes of cable connecting, a 5 to 10 minute charge, and you are back on the road. We keep a set of jumper cables in every car we own now. If you are buying a set, or you want the connection sequence in more depth including terminal identification and cleaning corroded posts, our guide on how to use jumper cables goes deeper on the equipment side. Our cables have paid for themselves many times over. If you want to skip the second car entirely, portable jump starter battery packs work great and can start many cars without needing another vehicle. They are small enough for a glove box, though the heat warning in the FAQs below applies. Get one if you often drive alone.
Questions we get asked about this
Answers from experience, not a textbook.
Car batteries produce small amounts of hydrogen gas, especially when they are dead or being charged. Connecting the last cable directly to the battery terminal can create a spark, and a spark near hydrogen gas can cause the battery to explode. By grounding to the engine block instead, any spark happens away from the battery. AAA gives the same instruction, and your owner's manual will show the grounding point to use.
If you follow the correct cable order, the risk is very low. The main way to cause damage is connecting cables to the wrong terminals, which can send a voltage spike through the electrical system. Modern cars have fuses and surge protection for minor issues, but a reversed connection can still blow a fuse or damage sensitive modules. Follow the order in this guide exactly and you will be fine.
If you turn the key and hear rapid clicking but the engine does not turn over, the battery is likely dead. If the dashboard lights come on dim or not at all, that also points to the battery. If you turn the key and hear nothing at all, it could be the starter motor or a loose connection. If the engine cranks normally but does not start, the problem is probably not the battery. It could be fuel, spark plugs, or something else entirely.
Yes, and they work surprisingly well. Modern lithium-ion jump starter packs are about the size of a smartphone and can start most four-cylinder and six-cylinder engines multiple times on a single charge. They take up almost no space, and many double as a USB power bank for charging phones. Before you leave one in the glove box, check the storage temperature range in its manual. A car parked in summer sun can get hotter than lithium packs are rated for, so in hot weather it may belong in the house rather than the car.
Check the owner's manual before you connect anything. Hybrids and EVs still carry a conventional 12-volt battery for the electronics, and a flat one will stop the car starting even when the main traction battery is full. The catch is that the designated jump points are often not the battery itself, and several manufacturers specify their own procedure. Some also prohibit using the vehicle to jump someone else, because the DC-to-DC converter is not built to deliver starter-motor current. This is the one case where guessing can get expensive, so spend the two minutes on the manual first.
Car Owner Essentials
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How to Check Your Oil
How to Jump Start a Car
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How to Use Jumper Cables