How to jump start your car

Your battery is flat, you can’t wait for roadside assistance and someone kindly agrees to help jump start your car. Here’s how to do it safely.

car battery and jumper leads

Sometimes you’ll need a jump start when your car battery is too flat to turn the car’s starter motor, so you can get it home or to a repairer to check the health of the battery.

It’s very handy if you have your own set of jumper cables as it makes finding someone to help you much easier. These should have inbuilt surge protection to protect the electronics of both yours and the donor car.

car jump start

Even with surge protection some modern cars, especially luxury vehicles, aren’t suitable for jump starting if they’re brimming with electronics or have a sensitive engine control unit. Check the manual before having your car jump started or helping someone else. If in doubt call your roadside assistance service to start the car for you as the mechanic will have suitable equipment.

If your car is less sophisticated, or you simply have no choice but to jump start, it’s important to do it properly. Even if you have done it before its worth going through the following steps as there may be some things you’ve been doing wrong that could cause considerable damage, particularly to newer cars.

Before attempting to jump-start the car ...

  • If the dead car is in a garage, roll it outside if possible as you don’t want the fumes of cars running their engines in an enclosed space
  • Turn off everything that drains power such as lights and radio
  • Make sure the ignition switch of both vehicles is off and not on accessories, or ‘ACC’
  • Position the cars so the batteries are close together but the cars aren’t touching
  • Make sure the car batteries are the same voltage. Almost all cars use a 12V system
  • Ensure the cars have their handbrakes on and are in Park (auto) or not in gear if manual
  • Remove the caps off the batteries (not applicable for maintenance-free batteries)
  • Clean any powdery residue off the battery terminals to ensure a good connection. 

How to connect the jumper leads

jumper leads battery
  • Connect one end of the red coloured jumper lead to the positive (+) terminal of the flat battery and the other end to the positive (+) terminal of the donor car’s battery
  • Connect one end of the black jumper lead to the negative (-) terminal of the donor car’s charged battery and the other end of the black jumper lead to a good earth point – such as a non-painted part of the engine block or car’s frame, making sure it is safely away from moving parts such as the fan belt. DO NOT attach this end of the black cable to the dead battery as it could cause a dangerous spark.

Now it’s time to jump start the car

  • Make sure everyone is clear of both engines and start the donor car
  • Now, start the dead car
  • If it turns over and fires up, switch on the headlights to help absorb any voltage spike and let it run for a few minutes before driving away
  • If it doesn’t start, let the battery rest for a couple of minutes and try again. If that doesn’t work check your jumper cable connections
  • If the car has started and has run for a few minutes, disconnect the jumper cable in the reverse order that you connected them, starting with the negative on the recipient car. You want the engine to keep running so make sure it’s safe
  • Thank the person who helped start your car
  • Be sure to get the battery checked and charged using a multi-stage charger as the car’s alternator won’t charge your battery back to full strength


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