Which lead do I connect first?

Positive on the flat battery, then positive on the donor, then negative on the donor, then the final black clamp to an unpainted earth point on the flat car, away from the battery.

How long should I drive after a jump start?

At least twenty to thirty minutes at steady speed, and ideally follow it with a mains charge. Short town journeys will not restore a deeply discharged battery.

Can I jump start a hybrid or electric car?

Never the high voltage system. Many hybrids have a twelve volt auxiliary battery that can be jumped using the manufacturer's designated points, so check the handbook first.

Why does my car go flat every few days?

That points to a charging fault or a parasitic drain rather than a worn battery. It needs a load test and a drain test rather than repeated jump starts.

Is a jump pack better than jump leads?

For most drivers, yes. There is no second vehicle to position, less risk of connecting incorrectly, and it works when nobody else is around.

How to Jump Start a Car Safely: UK Step-by-Step Guide

Confirm it really is the battery

A flat battery has a distinctive signature: the dashboard lights dim or flicker when you turn the key, the starter motor turns over slowly or clicks rapidly, and interior lights and central locking are weak or dead. If the dashboard lights are bright and steady and the engine cranks at normal speed but simply will not fire, the problem is more likely fuel, spark or an immobiliser fault, and jump starting will not help. A battery that goes flat repeatedly overnight usually points to a charging fault or a parasitic drain, not a battery at the end of its life.

What you need and where to park

You need either a set of jump leads rated for the engine size, or a lithium jump pack. Jump packs are safer for most drivers because there is no second vehicle to position and no risk of the two cars touching. If you are using leads with a donor car, park the vehicles close enough for the leads to reach comfortably but do not let the bodywork touch at any point. Switch off both engines, remove the keys, turn off headlights, heated screens, air conditioning and stereos, and put both cars in neutral or park with handbrakes applied.

The correct connection order

Connect the red lead to the positive terminal of the flat battery first, then the other red end to the positive terminal of the good battery. Connect the black lead to the negative terminal of the good battery, then connect the final black clamp to an unpainted metal earthing point on the flat car's engine block or chassis, not directly to the negative battery terminal. That last connection is deliberate: it keeps the small spark it creates away from the battery, which vents flammable hydrogen when discharged. Many modern cars have a designated remote jump point under a plastic cover in the engine bay precisely for this purpose, and it should be used where fitted.

Starting the engines

Start the donor vehicle and let it run for two or three minutes to put some charge into the flat battery. Then try the flat car. If it starts, leave both engines running for a few minutes before disconnecting. If it does not start after two attempts of around ten seconds each, stop. Repeated long cranking overheats the starter motor and rarely fixes anything the first two attempts did not. Disconnect in the exact reverse order: earth point, negative on the donor, positive on the donor, positive on the flat car.

After it starts

A jump start puts almost nothing back into the battery. To recharge it meaningfully, drive for at least twenty to thirty minutes at steady speeds rather than in stop start traffic, or better, put it on a proper mains charger overnight. Avoid switching the engine off until you are somewhere you would be happy to be stranded again. If the battery warning light stays on while driving, the alternator is not charging and the car will stop again once the remaining charge is used, so head somewhere safe rather than continuing a journey.

When not to jump start

Do not jump start if the battery casing is cracked, swollen, leaking or visibly frozen, because it can rupture. Do not attempt it on a hybrid or electric vehicle's high voltage system under any circumstances, although the small twelve volt auxiliary battery on many hybrids can be jumped using the manufacturer's designated points. Some modern vehicles with sensitive battery management systems, stop start technology or advanced driver assistance can throw persistent faults if jump started incorrectly, so check the handbook first. If in doubt, a recovery operator can test the battery and charging system properly rather than guessing.

Getting to the underlying cause

A healthy battery in a car that is driven regularly should not go flat. If yours has, something caused it: an interior light left on, a boot or door not fully closed, a failing alternator, a corroded earth strap, or a component drawing current after the ignition is off. Batteries also age, and most last between four and six years in UK conditions, with cold weather exposing weak ones first. A quick load test and a parasitic drain check at a garage cost far less than being recovered twice in a fortnight.

Frequently asked questions

Which lead do I connect first?: Positive on the flat battery, then positive on the donor, then negative on the donor, then the final black clamp to an unpainted earth point on the flat car, away from the battery.
How long should I drive after a jump start?: At least twenty to thirty minutes at steady speed, and ideally follow it with a mains charge. Short town journeys will not restore a deeply discharged battery.
Can I jump start a hybrid or electric car?: Never the high voltage system. Many hybrids have a twelve volt auxiliary battery that can be jumped using the manufacturer's designated points, so check the handbook first.
Why does my car go flat every few days?: That points to a charging fault or a parasitic drain rather than a worn battery. It needs a load test and a drain test rather than repeated jump starts.
Is a jump pack better than jump leads?: For most drivers, yes. There is no second vehicle to position, less risk of connecting incorrectly, and it works when nobody else is around.

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Call 07402 666 687

How to jump start a car safely