How to Jump Start a Car, Step by Step (with Cables or a Jump Starter)

You turn the key and get a click, a slow crank, or nothing at all. Before you pick up the cables, open the owner’s manual to its jump-start page, because some cars have a specific jump point and the maker’s steps win over any general list. If the manual adds nothing, the order that AAA and several automakers describe is this: red clamp to the dead battery’s positive terminal, red clamp to the good battery’s positive terminal, black clamp to the good battery’s negative terminal, and the last black clamp to bare, unpainted metal on the dead car, away from the battery. That last clamp never goes on the dead battery’s negative post.

Do not jump a battery that is frozen, low on fluid, cracked, leaking, or swollen. If you are unsure at any point, call roadside assistance or a technician. If anyone is hurt or it turns into an emergency, call 911. When in doubt, don’t.

Before you connect anything

A short check up front covers the two risks the manuals warn about most: a battery that ruptures and a spark near the battery.

• Read the manual’s jump-start page. AAA notes that some newer vehicles, including hybrids and electric cars, may need manufacturer-specific steps. It also points out that some batteries sit under the back seat or in the trunk, so the manual is the quickest way to find yours.
• Look at the battery. Mazda’s manual says jump-starting a frozen battery or one with a low fluid level is dangerous, and that it may rupture or explode. Kia’s manual gives the same warning about a frozen battery. In a Road & Track interview published on Car and Driver’s site, a technician says a case that is swollen beyond its normal shape is a sign to stop, and that terminals that look physically damaged, or acid built up around them, point to replacing the battery rather than jumping it.
• Match the voltage. Both Mazda and Kia say to use only a 12-volt source. A 24-volt supply, such as two 12-volt batteries wired in series, can destroy the starter and the ignition system.
• Protect your eyes and skin. Kia’s manual warns that battery acid is poisonous and highly corrosive and says to wear protective glasses.
• Check the cables. AAA says to use cables in good condition, with no frayed wire or exposed metal.

If you drive a hybrid or an electric car, read the section on those below before you start.

How to jump start a car with jumper cables

You need a second vehicle with a healthy 12-volt battery and a set of jumper cables long enough to reach between the two engine bays. AAA describes cables between 10 and 20 feet and says longer ones mean less maneuvering.

Set up the cars.

1. Park the helper car close enough for the cables to reach, but with the vehicles not touching. AAA suggests nose to nose about 18 inches apart if the spot allows it, and warns to watch the doors so the cars don’t bump.
2. Put both cars in park (automatic) or neutral (manual), set the parking brakes, turn off the ignition, and take the keys out. Turn off the lights, radio, and other accessories in both cars.
3. Open both hoods and find the battery terminals. The positive terminal is marked with a plus sign and the negative with a minus. If the terminals are dirty, AAA says to knock the dirt off with a rag or brush so you can see the markings and get a good grip.
4. Untangle the cables and keep the four clamps apart. Kia warns that letting the positive and negative cable ends touch can cause sparks. Mazda adds that cables should be routed away from the fans and belts, since a lead can get caught when the engine starts.

Make the four connections in this order.

1. Red clamp to the dead battery’s positive terminal. Wiggle the clamp until it bites. Ram’s manual adds that you should jump directly off the positive post, not off a fuse.
2. The other red clamp to the good battery’s positive terminal.
3. Black clamp to the good battery’s negative terminal.
4. The last black clamp to bare, unpainted metal on the dead car. A bolt, a bracket, or part of the engine block works if it is away from the battery. Ram’s manual describes a good ground as an exposed metal part of the engine, frame, or chassis, such as an accessory bracket or a large bolt, and says it must be away from the battery and the fuel injection system. Some manuals show a specific ground point in a drawing, so look for that first.

Why the last clamp goes on metal and not the battery. According to AAA, a dead battery can give off hydrogen gas, and if there is going to be a spark you want it away from the battery. Mazda’s manual says hydrogen gas produced during normal battery operation can ignite and cause the battery to explode. The final connection is the one most likely to spark, so it goes somewhere else. Ram’s manual warns that connecting the negative cable to the discharged battery’s negative post could cause the battery to explode, and Kia’s says it can make the discharged battery overheat and crack. This is the step most likely to go wrong, because the dead battery’s negative post looks like the obvious place for the clamp.

Start the cars.

1. Start the helper car and let it run for a few minutes. AAA, Mazda, and Ram all say to let it idle for a few minutes before you try the dead car.
2. Try the dead car. If it doesn’t start, AAA says to let the helper car run a few more minutes and try again.
3. Once it starts, remove the cables in the reverse order: the black clamp from the bare metal, the black clamp from the good battery, the red clamp from the good battery, and last the red clamp from the formerly dead battery. Don’t let the clamps touch each other while the other ends are still attached. If your battery has a protective cap over the positive post, Ram’s manual says to put it back.

How to jump start a car with a portable jump starter

A portable jump starter is a battery pack with cables and clamps attached, so you don’t need a second car. AAA notes they are bulkier than plain cables and shouldn’t be stored in a hot car. If you are still choosing one, our guide to the best portable jump starters compares them from published specs and maker claims. Keep the owner’s manual for your unit with it, because jump starters vary more than cables do.

For one example, the maker’s guide for the NOCO Genius Boost GB40 tells you to read your vehicle’s owner’s manual first, confirm you have a 12-volt lead-acid battery, and make sure the unit itself is charged. The general sequence for a unit like that:

1. Turn off everything in the car: lights, radio, air conditioning.
2. Connect the red clamp to the dead battery’s positive terminal.
3. Connect the black clamp where your unit’s manual says. This is the one place the manuals disagree. NOCO’s GB40 guide allows the negative battery terminal or the vehicle chassis, while the automaker manuals above point to bare metal away from the battery. If your jump starter’s manual gives you a choice, bare metal away from the battery matches what Mazda, Kia, and Ram describe.
4. Turn the unit on and check the indicator your manual describes. On the GB40, a white light means it is ready and a red light means the clamps are on backward.
5. Start the car. The GB40 guide says most vehicles start right away, some need the unit connected for up to 30 seconds, and if it doesn’t start you should wait 20 to 30 seconds and try again. It also says to stop after five consecutive attempts in a 15-minute period and let the unit rest for 15 minutes.
6. When the car is running, disconnect the clamps and remove the unit.

Some units have a manual override button for batteries below the voltage the unit can sense. On the GB40 that mode turns off the spark-proof and reverse-polarity protection, and the guide says to use it with extreme care or seek professional help. If your car’s battery is that flat and you are not sure, call for help instead.

Hybrids, electric cars, and remote jump terminals

Every hybrid and electric car also has a regular 12-volt battery, and the car will not start without it, even if the large drive battery is full. AAA’s guidance on electric cars says to use a gas-engine vehicle or a jump pack to jump the 12-volt battery, never another electric car or hybrid, and never to try to jump the main high-voltage battery.

Where that 12-volt battery is varies. AAA says it is usually under the hood, but the manual will tell you if not. Some cars, like the Toyota Prius V in Toyota’s quick reference guide, keep the battery in the cargo area and use a remote positive terminal in the engine bay’s fuse box. You remove the fuse box cover, open the positive terminal cover, and clamp the positive cable there, with the negative cable on a solid ground. Toyota’s guide also says the high-voltage battery cannot be jump started. Your car’s manual shows its own spot, which is why it comes first in this guide.

If it still won’t start, or dies again

If the car only clicks or does nothing, first check that each clamp has a firm grip on clean metal. Then wait a few minutes and try once more, as AAA suggests. If it still won’t start, AAA says it may be something other than the battery, such as corrosion, a fuse, or the starter, and a professional can diagnose it.

If the car starts but dies after the cables come off, the problem may be the charging system rather than the battery. A technician quoted in Road & Track points to the alternator or an accessory belt. Ram’s manual says that if you need frequent jump starts, you should have the battery and charging system inspected. A jump gets the engine running; it doesn’t tell you why the battery went flat.

After the jump

AAA Oregon/Idaho says to let the car run for at least 30 minutes, ideally with a short drive, so the alternator can recharge the battery and the car is less likely to stall again. AAA’s electric-car article says at least 20 minutes, so the sources vary, and neither is a promise that the battery is healthy. AAA says to have the battery fully charged and tested at a repair shop once the car is running. A test is how you find out whether the battery can still hold a charge.

Keep the right gear in the car

Ready.gov lists jumper cables as part of a car emergency kit:

Create an emergency supply kit for your car. Include jumper cables, sand, a flashlight, warm clothes, blankets, bottled water and non-perishable snacks. Keep a full tank of gas.

Source: Ready.gov, Winter Weather (ready.gov), accessed November 2026.

A jump starter can do the same job without a second car, and you can see what to look for in a jump starter on our resources page. Our winter driving car kit lists the rest, and the guide to the best car emergency kits covers ready-made options. A small extinguisher is another common car item, but whether yours is right for a hot car depends on the model, so read is it safe to keep a fire extinguisher in a car first.

If the jump doesn’t work and you are stuck in the cold, our guides on how to prepare for a winter storm and how to stay warm without power cover what to do while you wait. Follow your local emergency officials and call 911 if anyone is in danger.

The Family Emergency Binder has a Car Kit page with year-round and winter lists, so you can check off the cables and the rest of the kit before the next cold snap.