How to Jump-Start a Car Safely

Safety first. A dead battery can release small amounts of hydrogen gas, which is flammable. The connection order below makes sure any spark happens away from the battery.

The connection order (memorize this)

1. 1Red clamp to dead car's + terminal
2. 2Red clamp to donor car's + terminal
3. 3Black clamp to donor car's - terminal
4. 4Black clamp to unpainted metal on the dead car (engine bolt, chassis ground). NOT the battery.

To disconnect, do the reverse: black ground, black donor, red donor, red dead.

Step 1. Park the donor car close enough

Position the donor close enough that the jumper cables reach both batteries. Front-to-front is ideal. Both cars in Park (neutral for manuals), engines off, parking brakes engaged.

Step 2. Identify the battery terminals

Pop the hood on both cars. Identify the positive (+, usually a red cover) and negative (-, usually black) terminals on each battery. If the terminals are corroded (white or green crust), clean them gently with a wire brush before attaching cables.

Steps 3 through 6. Connect the cables in order

Follow the numbered order above. Don't let the clamps touch each other or any metal while you're doing this. While holding unclamped ends, keep them separated.

The reason the final connection goes to unpainted metal (chassis ground) instead of the dead battery: that connection can spark, and you want any spark to happen away from the dead battery's hydrogen gas.

Step 7. Start the donor car

Start the donor vehicle's engine and let it run for 2 to 3 minutes. This charges the dead battery and confirms the donor's alternator is supplying power.

Step 8. Start the dead car

Try to start the dead car. If it cranks slowly, wait another 2 to 3 minutes with the donor running and try again. If after 5 minutes it still won't start, the battery is likely too far gone for a jump. Call for service or replace the battery.

Step 9. Remove the cables (reverse order)

Once the dead car is running, remove the cables in the reverse order you connected them: black on the jumped car (ground), black on donor, red on donor, red on formerly-dead battery. Again, keep clamps from touching each other or any metal while handling.

Step 10. Drive the jumped car for at least 20 minutes

Drive the formerly-dead car for at least 20 minutes to let the alternator recharge the battery. Avoid short trips for the next few days. If the battery dies again within a day or two, it needs replacement.

When to use a portable jump pack instead

A lithium-ion jump pack ($60 to $150) lets you self-jump without a donor car. Keep one in the trunk. They hold charge for months, work in cold weather, and skip the "who do I call at 6am?" problem. Good options: NOCO GB40 (budget), NOCO Boost Plus (reliable mid-range), Stanley J5C09 (includes a compressor).

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