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How to use jump cable leads

About the author

Chris Pollitt is an award-winning automotive word-wrangler, editor of the website Not 2 Grand and a keen collector of crappy old cars.

You need to be somewhere, you jump into your car, you turn the key and… click. CLICK CLICK CLICK. Nothing. Your face, now full of rage, shimmers in the fading glow of the dashboard lights.

What you need is a jump start - some sweet, sweet volts from another vehicle. It’s the simplest thing in the world, but shockingly people still get it wrong and end up frying their cars.

We don’t want you to suffer the same fate. That’s why we’ve put this handy guide together for you, so you can be back on the road and motoring as soon as possible.

01 Check your leads

Hopefully, your jump leads aren’t something you need to use often. Though if that’s the case, you do need to give them a once over before using them. Is there any corrosion on the teeth? Are there any nicks or cuts in the wires? If so, wire brushes the corrosion off or, if the leads are damaged, replace them. They’re heavily insulated for a reason.

02 Identify the terminals

Get the other car in a position where both batteries are close, open the bonnets and make sure both cars are off. Then inspect the battery. It sounds so simple, but not every car is as simple as ‘red, positive. Black, negative’.

Sometimes the wires are well-hidden or insulated in a neutral colour. As such, look at the battery and be 100% sure you know which terminal is positive and which is negative – there will be a logo moulded into the battery next to each terminal.

If you get this wrong, you’ll kill the cars. In the old days of points and condensers, it might have fried a radio. In today’s world of ECUs and myriad electronics, it will cook the car and possibly render it completely terminal (heavy-handed pun intended).

03 Red cable first

Remember a game of snooker. Red first, black last. Connect the red, live lead to your battery’s positive terminal, then connect it to the positive terminal of the car giving you a jump.

04 Black cable last

Now take the black cable. This needs to go from the jump car’s negative terminal to your car. BUT NOT YOUR BATTERY. This is where people go wrong. They attach the lead to the flat car’s negative terminal. Don’t do that, as the flat battery could become overwhelmed by the sudden jolt, rupturing in the process. Instead, connect the negative lead to an earthed point on the engine or car.

05 Leave it alone

Leave the leads connected for a couple of minutes. Don’t turn on either car.

06 Crank it

After a couple of minutes, fire up the jump car and leave it running for a minute or two. Let those electrical juices gently flow into your ailing machine.


Now it’s time to revive the patient. Fire up your car, which should hopefully bark into life. Once running, let both cars sit running for about ten minutes. You may both need to sit in your cars and hold the revs up for this time. More revs, more electricity!

08 Shut it down

That’s it, you’re done. In a perfect world, you should be able to shut your car off and have it start again. This is because you really should remove the cables whilst the cars are off. Take them off in the reverse order you put them on. From here, you should be on your way.

It’s all fairly straightforward stuff, but before you crack on, there are a few things to be aware of.

  • A tiny 1.0 hatchback isn’t going to jump-start a Range Rover. You need cars of comparable size.
  • If it’s cold, it might take longer. Batteries perform slower when the temperature is down, so you might need to leave the cars running longer to get enough juice into your flat battery.
  • A jump-start should be a rarity, not an everyday occurrence. If you’re having to jump your car three times a week, it might be time to think about getting a new battery fitted.
  • Jump packs are your friend. Modern times bring modern tech, and that means you can buy pocket-sized lithium-ion battery packs that will jump your car. They’re about fifty quid and are an absolute godsend.