How to jump start a car

Have a flat battery? Here’s how to use jump leads

A jump start is a handy way to start a car with a flat battery. But jump leads can cause 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 trained mechanics.

If you’re keen to do it yourself, take a look at our advice on how to jump start a car. But make sure you read the instructions in your handbook and follow those if they’re different to our steps.

Read carefully all off the instructions

What you’ll need to jump start a car:

    • A pair of working jump leads.
    • The vehicle with the flat battery, which needs to be in a spot where jump leads can easily reach the battery.
  • Another vehicle with a fully-charged battery (avoid a hybrid or electric car as this could cause damage).

Fell unsure to jump start your car, call us now

Safety measures

Before you try to jump start a car, remember that batteries produce flammable gases. Here’s how to stay safe:

Check the battery and jump leads
  • 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.
Safety environment
  • Before you start, remove any dangling clothing – like a scarf or tie – as it could get caught up in the moving engine parts.
  • Don’t let any metal objects touch the car batteries – these could cause a spark and possibly make the battery explode. That includes rings, necklaces, watch straps, hand tools, clips, stray wires etc.
  • Never smoke or allow naked flames anywhere near either battery.
Removing the jump leads
  • Don’t remove the jump leads while the car engines are running. This can cause serious damage to the cars’ electronics.

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 1 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 020 3633 3330.

How to remove the jump leads

You remove the jump leads in the reverse order to how you attached them. But if you’re not sure, here are the steps:

  • Switch off the engines on both vehicles.
  • Take the black jump lead off the earthing point.
  • Remove the other end of the black jump lead from the working battery’s negative (-) terminal.
  • Disconnect the red jump lead from the working battery’s positive (+) terminal.
  • Remove the other end of the red jump lead from the positive (+) terminal on the flat battery.


If the battery’s more than 5 years old and seems like it’s struggling to start the car, get it checked out. It’s better to be safe than sorry – it’ll be worse if it’s a roadside emergency or on a cold morning when you’re already late for work.

Alliance 24/7 Vehicle Recovery / Transportation

We offer transport of all vehicles throughout the UK up to 2600 kg, Battery Jump Start In London , Roadside Assistance London . Breakdown recovery services for All type of vehicle in London up to 2600kg

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