How to Jump Start a Vehicle: Step by Step, 12V and 24V

Published 24 September 2020. Last updated 29 October 2026.

It has probably happened to you: you turn the key and get a slow groan, or nothing at all. Maybe a mate in the caravan park asks for a hand. Knowing how to jump start a vehicle safely turns a ruined morning into a ten-minute job. Here is how to do it, from a family car to a 24V truck.

Durst X500 jump starter connected to the battery of a Ford Ranger with the bonnet up

Before you start: is it really the battery?

If you turn the ignition and the engine cranks normally but won't fire, a flat battery isn't the problem and jump starting won't help. If the engine cranks slowly, or you only hear a click, a jump start is probably the answer.

Check the owner's manual for its jump starting section before you begin. If your car is a hybrid or EV, it is usually recommended not to jump start it, as it may damage the hybrid system and there is a risk of electric shock. Follow the manufacturer's instructions.

Find the battery. It is usually under the bonnet, but some newer vehicles have it in the boot, and some European cars have it under the passenger seat. Identify the terminals: positive has a (+) symbol and is usually the larger one; negative has a (-) symbol.

Not sure which jump starter suits your vehicle? Our guide to choosing a jump starter can help.

How to jump start a vehicle with a portable jump starter

A portable jump starter gets you going without needing a second car, which makes it a lot more convenient than jumper cables.

Read the manual for both the vehicle and the jump starter.
Make sure the jump starter is charged.
With the ignition and accessories off, attach the red clamp to the positive (+) terminal of the flat battery.
Attach the black clamp to the negative (-) terminal, or to the earth point your manual specifies.
Turn on the jump starter. Most Durst jump starters check polarity before sending power, with reverse polarity and anti-spike protection.
Start the vehicle. If it starts, leave the engine running.
Turn off the jump starter, remove the black clamp, then the red clamp, and pack it away.

Watch the method: video guide on YouTube.

After the jump start

Drive for at least 15 minutes to put some charge back in the battery. It is a good idea to top it up properly with a battery charger at home too. If the vehicle won't start next time, the battery probably needs replacing.

Jump starting a 24V truck or bus

Trucks, buses and most heavy machinery run on 24 volts, often from two 12V batteries in series. The steps are the same, but the jump starter must match the system:

Use a 24V unit, or a 12/24V unit with the selector set to 24V.
Never try to start a 24V system with a 12V jump starter. It won't have the voltage to do the job.
Connect to the points the vehicle maker specifies, which on a series pair is usually across the full 24V output, not one battery.

Durst's HYPASTART range and the BJC-4000-V2 and BJT-200-V3 all cover 12V and 24V. Our 12V and 24V jump starter guide explains which model suits which fleet.

Keeping a jump starter in a hot car this summer

A jump starter often lives in the glovebox or the back of the 4WD all summer. Battery-less units like the HYPASTART X500 use supercapacitors instead of a lithium cell. Read more in why the best 4WD jump starter has no battery.

Jump starter or charger?

We recommend both: a portable jump starter to keep you moving on the road, and a battery charger at home to fully recharge. Portable jump starters, also known as jump packs, battery boosters, emergency boosters, battery jumpers and jump boxes, can be used pretty well anywhere. Browse the jump starter range.

Frequently asked questions

How do I know if my battery needs a jump start?

If the engine cranks slowly or you only hear a click, the battery is likely flat. If it cranks normally but won't start, the problem is probably elsewhere.