What you need
- A set of jumper cables, or a portable jump-starter pack.
- A second working vehicle with a healthy battery of similar voltage (unless using a jump-starter pack).
- Both cars in park or neutral, parking brakes on, and engines off before you begin connecting anything.
Connect the cables in this exact order
- Park the working car close enough that the cables reach both batteries, without the vehicles touching. Turn off both engines and any electrical accessories (lights, radio, AC).
- Red (positive) clamp onto the positive (+) terminal of the dead battery.
- Red (positive) clamp onto the positive (+) terminal of the working battery.
- Black (negative) clamp onto the negative (−) terminal of the working battery.
- Black (negative) clamp onto an unpainted, bare metal part of the dead car's engine block or frame, such as a bolt or bracket, deliberately not the dead battery's negative terminal and not right next to the battery.
This order matters because the final connection is the one most likely to spark, and a spark right at the dead battery's terminals can ignite hydrogen gas the battery vents during charging. Grounding that last connection away from the battery keeps any spark away from where the gas collects.
Start the engines
Start the working vehicle first and let it idle for roughly five to ten minutes to let some charge transfer, then attempt to start the dead vehicle. If it doesn't start, double-check all four connections are secure and on the correct terminals, and make sure the clamps aren't touching each other while connected to a battery. If the dead battery shows signs of damage such as swelling, cracking, leaking, or a rotten-egg smell, stop — that battery may be failing and shouldn't be jump-started at all.
Disconnect in reverse order
Once the previously-dead car is running, remove the cables in the reverse sequence: black clamp off the grounded metal on the now-running car first, then black off the working battery, then red off the working battery, then red off the now-running car's battery.
After the jump
Keep the jump-started car running for a while, and drive it if possible, so the alternator can recharge the battery. A car that needed a jump often has a battery or charging-system problem that a single jump doesn't fix — if it stalls again shortly after, the battery or alternator likely needs professional attention rather than repeated jump-starts.
Safety precautions
- Red is positive, black is negative — reversing polarity can damage the electrical system or cause sparking and injury.
- Never make the final connection directly on the dead battery's negative terminal, since hydrogen gas near the battery is an explosion risk if ignited by a spark.
- Work in a ventilated area, and don't lean directly over either battery while connecting cables.
- Some hybrid and electric vehicles have manufacturer-specific jump-starting procedures, or in some cases don't support conventional jump-starting at all — check your owner's manual first if you're unsure.
- If you're not confident doing this yourself, professional roadside assistance is a reasonable and safer alternative, particularly for repeat dead-battery issues.
People also ask
Which jumper cable do I connect first?
The red (positive) clamp goes on first — dead battery's positive terminal, then the working battery's positive terminal — before either black clamp.
Why shouldn't the last clamp connect to the dead battery's negative terminal?
That final connection is the one most likely to spark, and connecting to a metal ground point away from the battery keeps any spark away from vented hydrogen gas.
What should I do right after the jump-started car starts?
Keep it running and drive it if you can, so the alternator recharges the battery — a single jump doesn't fix an underlying battery or charging-system problem.