Put the last jump lead on bare metal away from the battery
To jump-start a petrol or diesel car, check for damage, follow the clip order, and put the last black clip on bare engine metal.
From people’s advice and experience shared online; the jump-start steps and warnings are checked against the RAC in the UK, October 2026.
The car will not start, and you think the battery is flat. You have another car, or a set of cables, or a phone. Someone may have told you the order of the clips does not matter. Some people report that it went fine for them either way, but there is one step where getting the order right costs nothing, and it is the last one.
If neither battery nor either lead is damaged and both cars are ordinary petrol or diesel ones, check your owner’s manual first, switch both engines off, then connect the red lead to the flat battery’s plus, then the good battery’s plus, then the black lead to the good battery’s minus, and last of all the black lead to bare metal on the flat car’s engine, not to its battery.
If a battery is cracked, leaking or boiling, or you are in a car that is not an ordinary petrol or diesel one, this is not the page to follow; the safety box above and the last section say why.
The steps, in order
These are the RAC’s steps, with what people add.
- Switch off the lights and anything electrical in the flat car. One person says to have the headlights and electronics off in both cars.
- Park the helping car close to the flat one without the cars touching. Switch both engines off, take the keys out and open both hoods (bonnets).
- Clip one end of the red lead to the positive (+) terminal of the flat battery.
- Clip the other end of the red lead to the positive (+) terminal of the good battery.
- Clip one end of the black lead to the negative (−) terminal of the good battery.
- Clip the other end of the black lead to a good earth point on the flat car (a ground, in the US), which the RAC says is usually a solid metal part of the engine, and not the battery. One person says to look for unpainted metal, because paint or coating can stop the clip gripping.
- Start the helping car and let it run for up to five minutes, the RAC says.
- Try the flat car. If it does not start, the RAC says to wait another couple of minutes and try again.
- If it starts, leave it running for about five minutes, the RAC says.
- Switch both engines off, then take the leads off in the reverse order: black from the flat car’s engine metal, black from the good battery, red from the good battery, red from the flat battery. The RAC says to check that the engine starts again. One person says to keep the loose clips from touching each other while you move them.
One person gives a rhyme for it: red to the dead battery, red to the live one, black to the live one, black to bare metal on the dead car. Some people find “red to dead” confusing and say matching colours is easier to remember. Use whichever sticks, as long as the last clip goes on metal.
Why the last clip goes on metal
People disagree about the reason. Some people say a spark near the battery could set off hydrogen that a battery can give off, and that is why the final clip goes on metal away from it. Others say the risk is very small, that the hydrogen clears quickly once the hood is up, and that the real hazard is a clip touching metal where it should not and shorting. The RAC gives the metal-not- battery rule as a way to avoid sparks.
Some people say they clip the black lead straight to the battery and have never had trouble, and that it grips better. Those are their accounts. Following the RAC costs a minute of looking for bare metal, and if you cannot find bare metal, your manual or your breakdown service is the next step, not the battery terminal.
If it does not start
The RAC says that if repeated tries fail, there may be another fault, and you should call a breakdown service or a mobile mechanic. One person says the helping car’s battery runs down with repeated cranking, so wait between tries. Some people say a battery that keeps going flat after a long parking spell may have something drawing power from it. This page does not cover how to find that, or how to test whether a battery is worn out.
Other ways out
Many people say a portable jump starter beats cables, and some say to carry cables as well. Some people say a longer set of cables, around 25 feet, lets you park in any direction. One person says cheap cables can melt, and that decent ones are worth paying for. Some people say insurance, a card or a car policy may already include roadside help with jump starts, so check what yours covers before you pay anyone.
One person says standing by the car with the hood up and the cables out is a signal that gets people to stop. Some people warn about letting unknown people work under your hood. Those are the people’s accounts, and you are the one who knows where you are and who is near you.
Who this page is not for
If either battery is cracked, leaking or boiling, do not jump it. If the car is electric or hybrid, this page does not cover it, and the RAC says not to use one as the helping car unless its manufacturer permits it. If your battery is hidden in the boot, under a seat or behind a panel, the connection points may be somewhere else on your car, and the manual shows where. If the problem is a key fob with a low battery, not the car’s own battery, it is a different fix. Elsewhere, this page checked only the RAC, and the roadside numbers are your own.
Common questions
Does the order really matter?
People disagree. Some people say that any order works and that they have never had trouble connecting plus to plus and minus to minus. Others say the order matters. The RAC gives one order, ending with the last black clip on engine metal to avoid sparks, and following it costs you nothing, so it is the order on this page. People also disagree about why it matters. Some say a spark near the battery could ignite hydrogen gas that a battery can give off. Others say that risk is very small and that the real hazard is a loose clip touching metal and shorting the battery. One person says the only explosion they know of involved open battery caps, an enclosed space and a cigarette.
Can I clip the last black lead straight to the battery’s negative terminal?
The RAC says to use a good earth point on the flat car, a solid metal part of the engine usually being best, and not the battery itself. Some people say clipping to the negative terminal works more reliably, because painted or coated metal can give a poor contact. If a spot gives a poor contact, look for another bare metal part of the engine rather than moving the clip to the battery. If you cannot find one, your owner’s manual shows where to connect on your car, and your breakdown service can do it for you. This page does not say more than that.
Should I buy a jump pack instead of cables?
Many people say a portable jump starter is better than cables, because you need no second car, no waiting for a helper and no cable order to remember. People also give cautions. One person says packs often cannot start a completely drained battery, work poorly in cold weather, and that generic ones can be a fire hazard, and recommends cables as the more reliable backup. One person says a pack left in a car loses its charge over time. Some people suggest checking a pack’s charge and topping it up about once a month, or on the days the clocks change. This page could not check how any pack behaves, so follow the instructions that come with yours.
Can I ask a stranger, or call a taxi, for a jump?
One person says strangers are often willing to help when asked politely, especially by someone who carries their own cables. Some people warn that asking a stranger to work under your hood carries a risk of theft or harm, especially if you are alone or somewhere isolated. Many people say calling a taxi or ride-share driver with cables is an option; some people say licensed taxi companies train drivers to refuse because of liability, and one person says it works in their city while others say it does not in theirs. One person says standard car insurance may not cover injuries or damage that happen while someone jumps another car, so check your own policy before you ask.
It still will not start. What now?
The RAC says to wait another couple of minutes and try again, and that if it still does not work there may be another fault, and you should call a breakdown service or mobile mechanic. One person says repeated attempts to crank a dead car drain the helping car’s battery too, so let the cars sit connected for a few minutes between tries. Some people point out that on a push-button car, a dead key fob is a different problem from a dead battery: many such cars start if you hold the fob against the start button, and many fobs hide a mechanical key. Your owner’s manual says what yours does.
How do I stop it happening again?
Many people say a car that is not driven every day should be run for a good while, often given as 15 to 30 minutes or more, weekly or monthly. Some people say modern cars charge well enough that this is unnecessary, or that doing it badly does harm. People disagree. Some people say a car that sits for weeks may have something drawing power, such as a phone charger left in the socket or a dash camera, which they say can flatten a battery if it stays plugged in while parked. For long storage, one person says disconnecting the battery works and another says a battery maintainer is better where there is a power socket, since it holds the charge up; one person says a cheap basic charger can overcharge. One person points out that cold does not kill a healthy battery, it exposes a weak one, and that heat wears batteries out faster.
Questions this step helps with
Same situation, another step
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