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How to jump start a car safely

The steps, in the right order, and when a jump start is the wrong answer.

The short answerConnect the red clamp to the flat battery's positive terminal, then to the good battery's positive. Connect the black clamp to the good battery's negative, and the other end to bare metal on the stalled car, away from the battery. Start the good car, wait a few minutes, then start the flat one.

Before you start

  • Read the owner's manual. Some cars, especially hybrids and EVs, have a special jump point or shouldn't be jump started the usual way.
  • Use proper jumper leads, thick and in good condition. Switch both cars off.
  • Don't try if the battery is cracked, leaking or frozen.

The steps

  • Park the cars close, not touching, handbrakes on.
  • Red clamp on the positive (+) terminal of the flat battery.
  • Other red clamp on the positive (+) terminal of the good battery.
  • Black clamp on the negative (-) terminal of the good battery.
  • Last black clamp on bare metal of the stalled car's engine or body, away from the battery. This keeps any spark away from battery gases.
  • Start the good car and let it run for a few minutes.
  • Start the stalled car. If it doesn't start, wait a few more minutes and try once more.
  • Once running, remove the clamps in the reverse order. Keep the engine running for a good drive afterwards.

Why it died matters

If the car started and stays running, the battery may simply have been left drained. If it goes flat again within days, the battery is worn or the charging system is faulty. Ask a workshop to test both, and get the price in writing. If the car won't start at all, see My car won't start.

Hybrids and EVs

Many hybrids have a small 12 volt battery that can go flat just like any car, and a high-voltage battery you must never touch. Check the manual or ask a hybrid specialist.

Questions drivers ask

Can I jump start a car in the rain?

It can be done, but take extra care. Keep the clamp ends dry and off the ground, and if you are unsure, call roadside help instead.

How long should I drive after a jump start?

A good drive, ideally 20 to 30 minutes or more, helps the alternator put some charge back. A short trip may leave it flat again.

Will jump starting damage my car?

Done correctly it is normally fine. Connecting the leads the wrong way round can damage electronics, which is why the order matters.

Checked by AutoPlace editorial team. General information, not professional advice. Updated 15 October 2026.