5 min read
How to Jump Start a Car Safely (and When Not To)
To jump start a car, connect red to the flat battery's positive terminal, red to the donor's positive, black to the donor's negative, and the last black clamp to bare metal on the stalled car's engine — not to its battery. Start the donor, wait a few minutes, start the stalled car, then remove the cables in reverse order. If the battery is swollen, cracked or leaking, do not jump it at all.
A jump start borrows current from a healthy battery for the few seconds your starter motor needs. It is a simple job, but a modern car carries a lot of sensitive electronics, and most jump-start damage comes from one of two things: clamps connected in the wrong order, or clamps touching each other.
If you are not sure of any step below, stop. A wrong connection can cost far more than a call-out. Our technicians carry professional booster packs and can reach most areas of Abu Dhabi, Dubai and Sharjah at any hour.
Before you connect anything
Look at the flat battery first. Walk away from the jump start if you see any of these:
- A swollen, bulging or cracked battery case.
- Liquid leaking from the battery, or a strong rotten-egg smell.
- Heavy corrosion that has eaten into a terminal or a cable.
- A hybrid or electric car on either side, unless that car's manual says it can give or receive a jump.
The safe order, step by step
You need a set of jump leads in good condition and a donor car with a battery of the same voltage — 12 volts for almost every passenger car.
Park and switch everything off
Bring the donor car close enough for the cables to reach without the two cars touching. Both engines off, both in park or neutral, handbrakes on. Turn off lights, AC and the stereo in both cars.
Red to the flat battery's positive
Clamp one red lead to the positive (+) terminal of the flat battery. Many newer cars hide the battery and give you a marked jump post under the bonnet instead — use that.
Red to the donor's positive
Clamp the other end of the red lead to the donor battery's positive (+) terminal. Keep the free black clamps away from both cars' metalwork while you do it.
Black to the donor's negative
Clamp one black lead to the donor battery's negative (−) terminal.
Last black clamp to bare metal, not the battery
Clamp the final black end to an unpainted metal point on the stalled car's engine block or a marked earth point, well away from the battery. This is the step that keeps any spark away from battery gases.
Start the donor, then the stalled car
Run the donor engine for two or three minutes, then try the stalled car. If it does not start within a few seconds, stop, wait a minute and try once more. Repeated long cranks overheat the starter.
Remove the cables in reverse
Black off the stalled car's earth point, black off the donor, red off the donor, red off the car that was flat. Do not let the clamps touch while any of them is still connected.
Why the order matters
A charging battery gives off a small amount of hydrogen. The last clamp you connect is the one that sparks, so it goes on bare metal away from the battery rather than on the terminal itself. Every manufacturer's instructions agree on that final step.
The first two steps vary slightly between manuals — some, Varta's among them, attach the red lead to the donor car first. If your owner's manual gives an order, follow the manual.
After the engine starts
Keep the engine running and drive for at least 30 minutes so the alternator can put some charge back. Do not switch off at the first shop you reach — a battery that was flat ten minutes ago may not restart.
Then get it tested. A jump start is a way to move the car, not a repair. If you left a light on overnight, the battery may recover. If it went flat on its own, it is usually near the end of its life, and in UAE heat it will leave you stuck again within days.
When to call instead
Call a technician if the car is in a basement or a tight bay where a second car cannot get close, if you drive a European car with the battery in the boot or under a seat, or if the car clicks rapidly even with the leads connected. That last one usually means the battery is too far gone for a jump, or the fault is somewhere else.
A technician-led jump start also ends with a battery and charging-system test, so you know whether you need a new battery before you drive away.
Common questions
Can jump starting damage my car?
Done in the right order, no. Damage comes from reversed clamps, clamps touching, or jump starting a battery that is cracked or swollen. On cars with a lot of electronics, use the marked jump posts rather than the battery itself.
How long should I drive after a jump start?
At least 30 minutes of continuous driving. Short trips will not replace what the starter took, and the battery should still be tested afterwards.
The car still won't start with jump leads on. What now?
Stop trying. Either the battery is too deeply discharged to accept a jump, the cables are too thin for the engine, or the fault is in the starter or wiring. A technician can test it where the car is parked.
Dead battery right now?
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Sources
Last reviewed by the 800BATTERIES team.