when jumping a car battery which cable goes on first

[SanBrandon]

When jump-starting a car, you must always connect the positive (red) cable to the dead battery first, followed by the positive cable to the good battery. Then, connect the negative (black) cable to the good battery's negative terminal, and finally, attach the last negative clamp to an unpainted metal surface on the dead car's engine block, not the battery itself. This specific order is critical for minimizing the risk of a spark near the battery, which could ignite hydrogen gas and cause an explosion.

The reason for this sequence is safety. Car batteries can emit highly flammable hydrogen gas. Connecting the positive cables first completes the electrical circuit through the car's chassis and systems. By attaching the final negative clamp to a bare metal engine bolt or bracket—a point called a ground—you ensure any spark occurs far away from the battery, drastically reducing the hazard.

Correct Order (Safe)	Incorrect Order (Risky)	Primary Risk
Red to Dead (+)	Red to Dead (+)	Sparks near battery
Red to Good (+)	Black to Dead (-)	Hydrogen gas explosion
Black to Good (-)	Black to Good (-)	Battery damage
Black to Engine Ground	Red to Good (+)	Electrical system damage
Start Good Car	Start Good Car	Personal injury

After the dead car is running, carefully disconnect the cables in the reverse order: negative from the ground on the previously dead car, negative from the good battery, positive from the good battery, and finally, positive from the revived car. Let the jumped car run for at least 15-20 minutes to allow the alternator to recharge the battery sufficiently. If the battery dies again soon after, it likely needs replacement.

[VanOlivia]

Red on dead first, always. That’s the rule my dad drilled into me. You hook up the red clamp to the dead battery’s positive terminal. Then the other red to the good battery’s positive. For the black cables, you connect one to the good battery’s negative, but the last one doesn’t go on the dead battery. You find a shiny, unpainted metal part under the hood of the dead car—like a bolt—and clamp it there. This way, if there’s a spark, it’s away from the battery. It’s a simple habit that keeps you safe.

[MaximusLee]

The most critical step is the first connection: the positive cable to the dead battery. This establishes the circuit's starting point safely. The final connection is equally important; you must attach the last negative clamp to an unpainted metal surface on the dead car's engine block. This acts as a ground point. Any spark generated will happen at this remote location, not near the battery where flammable gases can accumulate. This procedure is a standard safety protocol recommended by AAA and other automotive authorities to prevent accidents.

[Truman]

Think of it like this: you’re managing risk. The positive cable is your “live” wire. You connect it to the dead battery first because it’s the point of need. The final step is your “spark management.” By clamping the last negative cable to a bare metal part of the engine, you’re sending the electrical current to ground safely. It’s like lighting a match away from a gas leak instead of right next to it. That last connection to a ground point is what makes the process safe instead of dangerous.

[Gloria]

The sequence is designed to isolate potential sparks. Start with both positive connections: red to the dead car, then red to the donor car. This completes the high-potential side of the circuit. Next, connect the black negative cable to the donor car's battery. The crucial final step is attaching the remaining negative clamp to a solid, unpainted metal component on the dead car's engine. This ensures the circuit is completed through the chassis, and the final connection—the one most likely to spark—is made a safe distance from the battery, mitigating the risk of ignition.