How do I jump start a car safely?

Updated October 21, 20266 sources3 min read

Short answer

Connect red to the dead battery's positive (+), red to the good battery's positive, black to the good battery's negative (-), and the last black clamp to bare, unpainted metal on the dead car away from its battery, not to the dead battery's negative post. Run the good car a few minutes, start the dead one, then remove the clamps in exactly the reverse order and keep the jumped car running for at least 20 to 30 minutes.

Safety first. Batteries give off hydrogen gas that can explode from a single spark, which is why the last clamp goes on bare metal away from the battery. Wear eye protection, take off rings and bracelets, don't lean over the battery, and never let the red and black clamps touch each other. Never jump a battery that is frozen, cracked or leaking. Only use a 12-volt car or jump pack, and on a hybrid or electric car, jump only the 12-volt battery as the owner's manual shows, never the high-voltage battery.

On this page

Step by step
The cable order at a glance
What you need
The safety rules that matter
If it starts, you’re not done
If it doesn’t start
Hybrids and electric cars
Follow-up questions
Sources

Step by step

1
Park and shut everything off
Pull the good car close enough for the cables to reach, but don't let the two cars touch. Put both in Park (or Neutral for a manual), set both parking brakes, turn off both engines, and switch off lights, radio and climate control.
2
Find the terminals
Open both hoods and find each battery's positive (+, usually red cover) and negative (-) terminal. If you can't find the battery or a clear negative terminal, your owner's manual shows the jump points. Look for cracks, leaks or a bulging case first, and stop if you see any.
3
Red clamp on the dead battery's positive
Attach one red clamp to the positive (+) terminal of the dead battery.
4
Other red clamp on the good battery's positive
Attach the other red clamp to the positive (+) terminal of the good battery or the jump pack.
5
Black clamp on the good battery's negative
Attach one black clamp to the negative (-) terminal of the good battery.
6
Last black clamp on bare metal on the dead car
Attach the final black clamp to a solid, unpainted metal point on the dead car's engine or frame, away from the battery and from belts and the fan. Hyundai's manual and Consumer Reports both say not to use the dead battery's negative post, because a spark there could ignite battery gas.
7
Start the good car, then the dead one
Start the good car and let it run a few minutes (Hyundai and Nissan manuals say at about 2,000 rpm, a light touch on the gas). Then try the dead car. Nissan says not to crank longer than 10 seconds; if it doesn't start, turn the key off, wait, check the clamps and try again.
8
Remove the clamps in reverse order
Black off the dead car's metal first, then black off the good battery, then red off the good battery, then red off the jumped battery. Keep the clamp ends apart until they're all off.
9
Keep it running
Drive or idle the jumped car for at least 20 to 30 minutes so the alternator can recharge the battery (Hyundai says a fully drained battery may need up to 60 minutes). Then get the battery and charging system tested, because a battery that died once often dies again.

The cable order at a glance

Step	Clamp	Goes on
1	Red (+)	Dead battery, positive terminal
2	Red (+)	Good battery (or jump pack), positive terminal
3	Black (-)	Good battery (or jump pack), negative terminal
4	Black (-)	Bare, unpainted metal on the dead car’s engine or frame, away from the battery

To disconnect, go 4, 3, 2, 1. Sources: Hyundai owner’s manual and Consumer Reports.

What you need

Jumper cables, or a charged portable jump starter (jump pack). A jump pack takes the place of the second car; Hyundai’s manual treats it the same way (red to positive, black to a bare metal ground), and its own instructions cover the rest.
A helper car with a 12-volt battery. Nearly every gas car qualifies. Don’t use a hybrid or EV as the helper for an EV (AAA).
Eye protection and gloves if you have them.

The safety rules that matter

The last clamp goes on bare metal, not the dead battery. Batteries give off hydrogen gas. The final connection can spark, so keep it away from the battery.
Red and black never touch while any clamp is connected to a battery.
Keep hands, hair and cables away from the fan and belts, even with the engines off (Hyundai).
Don’t jump a damaged or frozen battery. Cracked, leaking, bulging or frozen means stop and get help.
Don’t push-start a modern car to get around a dead battery; Hyundai’s manual says it can damage the vehicle.

If it starts, you’re not done

A jump gets you going; it doesn’t fix why the battery died. Keep the car running for at least 20 to 30 minutes, avoid shutting it off at the first stop, and have the battery and alternator tested. Some shops test batteries for free; Les Schwab, for one, says it does. If the battery dies again in a day or two, see why a car battery keeps dying. If the battery light comes on while you drive, the alternator may not be charging; see battery light on while driving.

If it doesn’t start

Rapid clicking: the battery is still too low or a clamp isn’t biting. Re-seat the clamps on clean metal and let the good car run a few more minutes.
One click, bright dash lights: more likely the starter or its relay. Our clicking but won’t start page explains how to tell.
Cranks normally but won’t fire: the battery did its job; the problem is fuel, spark or something else. A jump won’t help.

Nissan’s manual says not to crank for more than 10 seconds at a time. After a few tries, stop and call roadside assistance or a shop.

Hybrids and electric cars

Hybrids and EVs still have a regular 12-volt battery, and AAA notes an EV with a fully charged main battery still won’t start if the 12-volt battery is dead. Where that battery and its jump posts are varies by model; Firestone and AAA both say to follow your owner’s manual for the exact points. Never connect anything to the high-voltage battery or its orange cables.

Common follow-up questions

What order do you connect jumper cables?

Red to the dead battery's positive, red to the good battery's positive, black to the good battery's negative, then black to bare metal on the dead car. A short way to remember it: positives first, starting at the dead battery, and the last connection is the ground on the dead car. Take them off in exactly the reverse order.

Why not put the last black clamp on the dead battery's negative post?

The last connection you make can spark, and a battery gives off hydrogen gas that can explode. Putting that last clamp on bare metal away from the battery keeps the spark away from the gas. Some guides, like Les Schwab's, allow the negative post, but owner's manuals such as Hyundai's say not to, so we follow the manual.

How long should I leave the cars connected before trying to start?

A few minutes with the good car running. The Hyundai and Nissan owner's manuals say to run the helper car at about 2,000 rpm for a few minutes first; AAA's EV guidance says about five minutes, and another five if the first try fails.

How long do I need to drive after a jump start?

At least 20 to 30 minutes. Consumer Reports says to let it run at least 20 minutes; Hyundai's manual says at least 30, and up to 60 for a completely drained battery. Short trips after a jump may not put back enough charge, so the car can be dead again the next morning.

The car still won't start after a jump. What now?

Check that every clamp is biting on clean metal and try once more after a few more minutes of charging. If you hear rapid clicking, the battery may be too far gone or the connection poor; a single click with bright lights points to the starter. If it cranks but won't fire, it's not a battery problem. Don't keep cranking; call roadside assistance or a shop.

Can you jump start a hybrid or electric car?

Yes, but only its 12-volt battery, which is what wakes the car up. AAA says never to try to jump the main high-voltage battery and warns against using another EV or hybrid as the helper car for an EV, because it can damage both cars' electrical systems. Use a gas car or a jump pack, and follow your owner's manual for where to clamp.

Is a portable jump starter worth it?

For most drivers, yes. Consumer Reports describes them as roughly paperback-sized batteries that usually hold a charge for months, and some also charge phones. You don't need a second car or a stranger's help. Check its charge every few months and pick one rated for the heat inside a parked car.

Can you jump a frozen battery?

No. The Hyundai and Nissan manuals both warn never to jump a frozen battery because it can explode. If the battery case is bulging or you see ice, let it thaw or have it towed and tested.

Sources

General information only, not a diagnosis. Your owner’s manual comes first. How we write these