How to Jump-Start a Car: The Clamp Almost Everyone Connects Wrong

You leave the lights on, the car sits for a week, and one morning nothing turns over. Jump-starting is the best-known fix, but the order in which you connect the cables matters for your safety.

Before you begin

Park the two cars close enough for the cables to reach, but not touching. Switch both off, set the parking brakes, and put them in Park (or first gear or neutral for manuals). If the dead battery is cracked, swollen or leaking, leave it alone.

The right connection order

1. Red clamp on the positive (+) terminal of the dead battery.
2. The other red clamp on the positive terminal of the healthy battery.
3. Black clamp on the negative (-) terminal of the healthy battery.
4. The last black clamp on bare, unpainted metal of the car with the dead battery, away from the battery itself. A bolt or a metal bracket on the engine works well.

Why bare metal?

This is the detail that makes the difference. Lead-acid batteries can release flammable hydrogen gas, and the final connection is the one most likely to throw a small spark. Make it on the battery's negative post and the spark happens right where the gas collects. Make it away from the battery, on clean metal, and the circuit closes safely. The metal needs to be bare because paint insulates and blocks the current.

After it starts

Start the donor car first and let it run for a few minutes, then try the other one. If it does not catch, do not keep cranking, wait a moment and try again. Once running, remove the cables in reverse: black from the bare metal, black from the healthy battery, then the reds. Keep the clamps from touching each other. Drive for about half an hour, and if the battery dies again, get it tested, since it has probably reached the end of its life.

One last tip: always check your owner's manual, as some models specify their own connection points.