How to jump-start a car without damaging anything

Red to dead, red to donor, black to donor, black to bare metal.

Order matters, and the last connection matters most. With both engines off: red clamp to the positive terminal of the flat battery, other red clamp to the positive terminal of the good battery, black clamp to the negative terminal of the good battery, and the final black clamp to an unpainted metal point on the engine or chassis of the flat car, away from the battery.

That last step keeps the inevitable small spark away from the battery, which can vent hydrogen. Start the donor car, let it run a couple of minutes, then try the flat one. Remove the clamps in exactly the reverse order.

Check the vehicle manual first. Many modern cars specify a designated jump point rather than the battery terminals, some hybrids and electric vehicles must never be used as the donor, and a few have particular requirements to protect their electronics. If the battery case is cracked, swollen or leaking, or if it is frozen, do not jump it at all.

A jump gets you moving; it does not fix anything. If a battery needed jumping twice in a week, it or the charging system needs attention.

Part of the Stalwart guides. See all guides.