But they are something you should only use if you understand when and how to use them safely. Here to help then is our guide to using jump leads correctly on a car.

What do jump leads do?

Jump leads, also known as jumper cables or booster cables, are easy to purchase either online or in stores.

But what do they look like and how do they even work? They consist of a pair of cables which contain insulated wires inside and have alligator clips at each end that can connect to car batteries.

The length of the cables can vary depend on what exact set you buy. There are also different specifications sold which better suit different kinds of battery and engine size.

The alligator clips are usually coloured with red and black handles to represent the two polarities of the vehicle’s direct current system. The red alligator clip is for the battery’s larger ‘positive’ pole and the black clip is for the smaller ‘negative’ pole.

It’s important to understand all of this because attaching the clips to the opposite polarities they’re meant for could cause damage and even a safety hazard.

Preparing to use jump leads

Before attempting to use jump leads, there are some important safety tips worth keeping in mind.

Consult your vehicle’s handbook for details on what type of jump leads are most suitable and how to use them. Check this for both cars involved in a battery recharge. You’ll also want to confirm that the jump leads you have are compatible with your car’s engine and battery.

There are general rules for jump starting engines, but certain cars could carry specific procedures and you should always follow them.

Keep metal objects, cigarettes, and loose fitting clothing out of the way while attaching jump leads to your car engine to minimise the risk of fire or explosions. Keep your hands as far away from the engine as possible too.

Also, make sure that the bodies of the two cars involved in the use of jump leads are not directly touching one another. Both cars should also have their handbrake on and ignition off.

If you’re still in any doubt at all about how to prepare, then you’re better off leaving the task to someone else, preferably a professional you could call from an emergency breakdown service.

Using jump leads on your car

Use the red jump lead to connect to the positive pole/terminal of the donor car with the working battery to the positive terminal of the car with the flat battery.

Then use the black jump lead to connect between the negative terminal of the working battery to a suitable earthing point on the engine or chassis of the vehicle with the dead battery. Unlike with the red jump lead, you shouldn’t simply connect from battery to battery and don’t connect the black lead to the faulty car’s fuel system either.

When both leads are connected to their suitable points, wait for at least three minutes before you start the engine of either car involved.

Afterwards, start the engine of the donor car (with the functional battery) first and let it run for a minute. Then, with the donor car’s engine still running start the engine of the other car and leave both running for ten minutes.

When enough time has passed, turn off the ignition on both cars BEFORE you carefully disconnect the jump leads in the reverse order to the way they were connected.

Once the jump leads have been used and removed properly, start the engine of the car that had the dead battery. It should now be able to run without the aid of another vehicle.

If you notice any of the jump leads are getting hot, then safely remove then as soon as you can and let them cool off to avoid a potential fire.

Assuming you’ve followed the procedure correctly, if the car with the flat battery still won’t start then this indicates the car has a serious problem with the charging or ignition system. You’ll therefore be better off getting mechanics at a garage to investigate your car.