Last updated November 30, 2021
Jump starting a car is the most common way to start a car in the event of a flat battery. However, it can be very dangerous to jump start a vehicle if you misuse the jump leads.
Our simple step-by-step guide explains how to jump start your car correctly and includes a dedicated section on jump starting your car with a battery booster pack.
You’ll need a set of working jump leads that have no faults, to link the flat car battery to the working battery of another car.
You’ll need a donor car with a working battery to transfer electricity to the flat battery on your car.
Sometimes there are dangerous sparks created when jump starting a car. To protect your eyes, you should always wear safety goggles.
When jump starting a car, you mustn’t take any unnecessary risks. Stay safe by following the guidelines below:
Before you jump start your car, remove any loose clothing that could get tangled in the engine. Next, remove your jewellery and put on your protective glasses.
You’ll need to park the two cars nose-to-nose. Ensure enough space is left between each car to open both bonnets and connect the jump leads.
With both ignitions turned off and the parking brakes engaged on both cars, attach the red lead to the donor car's positive (+) terminal and the other end to the flat battery’s positive (+) terminal.
Once the red jump lead is attached, connect the black jump lead to the negative (-) terminal on the donor car. The other side of the jump lead should be attached to an unpainted metal surface, well away from the fuel system and the battery on the car with a flat battery as an earthing point.
Once the jump leads are securely connected, start the donor vehicle’s engine and allow it to run for 3-5 minutes. It should remain in park or neutral with the handbrake locked.
After the donor vehicle has been running for 3-5 minutes, start the car with the flat battery.
Leave both cars in idle and allow them to run for 10 minutes with the jump leads still attached.
After you’ve left both cars to run for ten minutes, turn off both cars. In reverse order to how you applied them, disconnect the cables without letting them touch each other.
Once you’ve safely removed all jump leads, turn on the car with a newly charged battery and leave it running for 15-20 minutes. Next, drive the car for 20-30 minutes on a route where stop-start driving is unlikely to further charge the battery.
A 24-volt battery is simply two 12-volt batteries combined in one unit, and you can use the same boosting process detailed above to jump start them.
Before changing the cables from one battery to the other, turn off the assisting vehicle’s engine or booster pack before removing and reconnecting the cables. Conveniently, you can charge both batteries simultaneously using a working vehicle and a booster pack.
Not everybody will be comfortable jump starting a car, even with the detailed step-by-step process we’ve provided. It might also be the case that you need to replace your cars battery if it still isn’t working after you’ve followed our instructions, which will require an expert to diagnose and fit.