A dead battery is inconvenient, not complicated — as long as you connect things in the right order. Here's the sequence that keeps it safe, whether you're using another car's battery or a portable jump starter.
Before you connect anything
Turn off both vehicles' ignitions. Check that your portable jump starter (or the donor car) is actually rated for your engine size — most portable units list a peak amp rating, and a small unit rated for a compact sedan won't reliably start a truck or SUV.
The connection order
- Red clamp to the dead battery's positive terminal
- Red clamp to the donor battery's (or jump starter's) positive terminal
- Black clamp to the donor battery's (or jump starter's) negative terminal
- Black clamp to an unpainted metal surface on the dead car's engine block — not the dead battery's negative terminal
Why that last step matters
Connecting the final clamp directly to the dead battery's negative terminal creates a small spark right next to a battery that may be venting hydrogen gas. Grounding to the engine block instead moves that spark away from the battery itself.
Starting the car
With a donor car, let it run a minute or two before attempting to start the dead one. With a portable jump starter, most modern units are ready instantly — try starting as soon as it's connected. If it doesn't turn over in the first few tries, stop and check your connections rather than repeating attempts.
After it starts
Remove the clamps in reverse order, and let the car run for at least 15–20 minutes (or drive it) to let the alternator recharge the battery. If it dies again shortly after, the battery itself likely needs replacing, not just a jump.
Never connect a portable jump starter or jumper cables backwards — reversed polarity can damage both vehicles' electronics. If you're ever unsure which terminal is which, check for the + and − markings molded into the battery case before connecting anything.