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How-To 10 minutes Easy–Medium

How to Jump Start Your Car

A flat battery doesn't have to mean a call to the breakdown service. Here's how to safely jump start your car using another vehicle.

Critical: The order in which you connect and disconnect the cables is important. Getting it wrong can cause sparks, damage the car's electronics, or in rare cases cause battery explosion. Follow the steps exactly.

What You'll Need

  • A set of jump leads (jumper cables), longer cables are easier to work with
  • A donor vehicle with a working battery of similar voltage (12V for standard cars)

Never jump start a hybrid or electric vehicle without checking the manufacturer's guidance, the procedure can be different.

Step-by-Step: Connecting the Cables

Position the donor vehicle so the batteries are close together (nose-to-nose usually works). Turn off both vehicles.

  1. Red cable to flat battery +, Connect the red (positive) cable to the positive terminal (marked + or red) on the flat battery.
  2. Red cable to donor battery +, Connect the other end of the red cable to the positive terminal on the donor battery.
  3. Black cable to donor battery −, Connect the black (negative) cable to the negative terminal (marked − or black) on the donor battery.
  4. Black cable to earth on flat car, Connect the other end of the black cable to an unpainted metal part of the engine or chassis on the dead car, NOT to the negative battery terminal. This reduces the risk of a spark near the battery, which can emit hydrogen gas.

Starting the Cars

  1. Start the donor vehicle and let it run for 2–3 minutes at a slightly raised idle.
  2. Try to start the flat car. If it doesn't start, wait another minute and try again.
  3. If the car starts, let both vehicles run for a few minutes.

Disconnecting the Cables (Reverse Order)

Remove the cables in the exact reverse order you connected them:

  1. Black cable from the earthing point on the previously flat car
  2. Black cable from the donor battery −
  3. Red cable from the donor battery +
  4. Red cable from the previously flat battery +

After Jump Starting

Drive the car for at least 20–30 minutes to allow the alternator to partially recharge the battery. If the battery dies again quickly, it needs replacing. A single flat battery event can be bad luck (e.g. a light left on), but recurring flat batteries usually mean the battery has failed and should be tested or replaced.

Tip: Keeping a compact lithium jump starter pack in your car means you don't need another vehicle to jump start. They cost £30–80 and are small enough to fit in the glovebox.