When jump-starting a car, you always connect the positive (+) cables first and the negative (-) cables last. The correct, safe order is: positive to the dead battery, positive to the good battery, negative to the good battery, and finally, the negative cable to an unpainted metal surface on the dead car's engine block—not the dead battery itself.
This sequence is critical for safety. Connecting the positive cables first completes the electrical circuit through the car's intended grounding system. The final step of grounding the negative cable away from the battery is the most important safety measure. A dying battery can emit highly flammable hydrogen gas. Connecting the negative clamp directly to the dead battery's terminal can create a spark, potentially causing the battery to explode. Attaching the clamp to a bare metal engine part, like a bracket, provides a safe path to ground without the spark risk near the battery.
Here is a quick reference for the connection steps:
| Step | Cable Clamp | Connection Point | Car |
|---|
| 1 | Red (+) | Positive Terminal | Dead Battery |
| 2 | Red (+) | Positive Terminal | Good Battery |
| 3 | Black (-) | Negative Terminal | Good Battery |
| 4 | Black (-) | Unpainted Metal (Engine Block) | Dead Car |
After the cables are securely connected, start the car with the good battery. Let it run for a few minutes to transfer charge, then attempt to start the dead car. Once it's running, carefully disconnect the cables in the reverse order: negative from the grounded metal on the previously dead car, negative from the good battery, positive from the good battery, and finally, positive from the now-running car. Drive the jumped car for at least 20-30 minutes to allow the alternator to recharge the battery sufficiently.
