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Car battery dead: how to jump-start it safely

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The short answer

To jump-start a car, connect the cables in a set order between the dead battery and a good battery, start the good car, then start yours. Always follow your owner's manual. Do not jump a battery that is cracked, leaking or damaged. If you are unsure, call for help.

How do I know if my battery is dead?

A dead battery often shows up as a clicking sound, dim lights, a dash that flickers or a car that does nothing at all when you turn the key or press the button.

Other problems can look the same. A bad starter, a loose cable or a fuel problem can also stop a car from starting. If a jump does not work, you likely need help.

What is the safe order for jumper cables?

The standard order is positive to positive, then negative on the good battery, then a bare metal spot on the dead car. That last connection keeps a spark away from the battery.

Removing the cables goes in the opposite direction. The exact points can differ by car, and some cars have jump posts under the hood. Follow your owner's manual.

  • Red on the dead battery positive.
  • Red on the good battery positive.
  • Black on the good battery negative.
  • Black on bare metal on the dead car, away from the battery.
  • Remove in the reverse order.

When should I not try to jump-start a car?

Do not jump a battery that is cracked, leaking, bulging or frozen, or one that smells like rotten eggs. Do not jump a car if you see a fuel leak, smoke or damage under the hood.

Also skip it if the manual says not to, or if you are not comfortable. Batteries can give off gas and sparks, so wear eye protection, and never smoke or allow an open flame near either battery. No jump is worth a burn or a fire. Call for help.

What about hybrid and electric cars?

Hybrid and electric cars often have a small regular battery that runs the computers, and the rules for jumping it can be different. Some have special points, and some should not be used to jump other cars.

Read the manual before you try anything. If you cannot find the answer, call your roadside assistance plan or a local tow company. Many can do a jump on the spot.

Step by step

  1. Read your owner's manual first

    It shows where the battery or the jump points are and any special rules for your car. Follow it over any general advice.

  2. Protect your eyes and keep flame away

    Wear eye protection if you have it. Keep cigarettes, lighters, matches and any open flame well away from both batteries, because a battery can give off flammable gas.

  3. Check the battery

    Do not jump a battery that is cracked, leaking, bulging or visibly damaged, or if you smell rotten eggs. Call for help instead.

  4. Park the cars close, not touching, and turn everything off

    Turn off both engines, lights and radios. Set both parking brakes. Keep the cars from touching.

  5. Connect the red clamps

    Clip one red clamp to the positive terminal of the dead battery. Clip the other red clamp to the positive terminal of the good battery.

  6. Connect the black clamps

    Clip one black clamp to the negative terminal of the good battery. Clip the last black clamp to bare, unpainted metal on the dead car, away from the battery and moving parts.

  7. Start the good car and let it run

    Let it run for a few minutes. Keep cables away from fans and belts.

  8. Try to start the dead car

    If it starts, let it run. If it does not, wait a couple of minutes and try once more. If it still will not start, stop and call for help.

  9. Remove the cables in reverse order

    Take off the last black clamp first, then the other black clamp, then the red ones. Do not let the clamps touch each other. Keep the engine running and drive for a while.

Frequently asked questions

What if my car starts and then dies again?

The battery may be too weak, or the car may not be charging it. Have it checked soon. If it dies again, call for help so you do not get stuck somewhere unsafe.

Can I jump-start a car in the rain or snow?

It can be done, but take extra care. Keep the clamps and your hands dry where you can, and keep cables out of puddles. If conditions are bad, call for help.

How long should I drive after a jump?

Your manual or a mechanic can advise. A common idea is to drive for a while so the car can recharge the battery. If the battery is old, it may need to be replaced.

Who can jump my car if I have no cables?

Your roadside assistance plan or a local tow company can often do it. Give them your location and say that the car will not start.

Stuck right now?

If anyone is hurt, or you are stopped in traffic, call emergency services first. Then get to a safe spot away from moving traffic.

Once you are safe, call your local tow company or your roadside assistance plan. This page is general information and cannot send help.

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