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How to jump start a car

Feeling flat? Here's how to use jump leads

Jump leads are a handy way of starting a car with a flat battery, but they can cause real damage to both cars and people if they’re not used properly. For your safety, and our peace of mind, we’d always prefer you to give us a call and leave the jump starting to our experienced technician.

Broken down?
Call us on 0800 88 77 66
or request help via the AA app

If you’re determined to do it yourself, make sure you read the instructions in your handbook and follow those if they’re different to our guidelines below.

Using jump leads

Using jump leads safely

Before you attempt to jump start your car, remember than batteries produce flammable gases. Here's how to stay safe:

  • Never try to jump start a battery that looks damaged or is leaking.
  • Don’t use jump leads that are damaged.
  • Stop using the jump leads if they get hot.
  • Never smoke or allow naked flames anywhere near either battery.
  • Don’t let any metal objects come in contact with the cars’ batteries, as these could cause a spark and possibly make the battery explode. That includes rings, necklaces, watch straps, hand tools, clips, stray wires etc.
  • Don't remove the jump leads while the cars’ engines are running. This can cause serious damage to the cars’ electronics.
  • Before you start, remove any loose-fitting clothing – like a scarf or tie – as these could get caught up in the moving engine parts.

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A step-by-step guide to jump starting a car

Find someone with a car who’s happy to help. Their car must have a fully charged battery with the same voltage as yours (usually 12 volts).

1. Line up both cars

  • Park both cars so their batteries are within easy reach of one another (without the cars actually touching).
  • Keep the handbrakes on and the ignitions off.

2. Connect the red jump lead

  • Use the red jump lead to connect the working battery’s positive (+) terminal to the flat battery’s positive (+) terminal.

3. Connect the black jump lead

  • Take the black jump lead and attach it to the negative (-) terminal on the working battery.
  • Then attach the other end to an earthing point (unpainted metal on the engine block or chassis) well away from the flat battery and fuel system.

4. Start the other car

  • Keep both engines off and wait for 3 minutes, then start the working car’s engine and let it run for a minute.

5. Start your car

  • Turn on the engine in the car with a flat battery.

6. Let both cars run

  • Leave both cars to idle, at a fast pace, for around 10 minutes

7. Turn off and disconnect

  • Turn off both cars’ engines and carefully disconnect the leads in the reverse order to the way they were connected (remove the black lead from your car first and finish with the red lead from the other car).
  • Make sure the leads don’t touch one another, or either car, as you remove them

8. Restart your car

  • Try turning the keys in the ignition to see if your car will start up.

9. Call for help

  • If your car won’t start there’s probably a more serious problem requiring professional help
  • If you’re still stuck, you can call us on 0800 88 77 66 or by using the AA app.

How often should you change a car battery?

On average, batteries do last between 5 and 7 years, but you should only consider changing a car battery when it's showing signs of deterioration. 

If the battery is more than 5 years old and there's any sign of it struggling to start the car, get it checked out. It's much better done at your convenience than as a roadside emergency or on a cold morning when the load on the battery is higher and you're already late for work.

Battery Assist will replace your battery and have you ready to be on the move again on the same day.

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