To jumpstart a car safely, attach the red jumper cable to the dead battery’s positive (+) terminal, attach the other red end to the donor battery’s positive (+) terminal, connect the black cable to the donor battery’s negative (-) terminal, and clamp the final black end to an unpainted metal surface on the dead car’s engine block. Grounding the final black clamp to bare chassis metal away from the battery prevents sparks from igniting flammable hydrogen gas emitted by a discharged lead-acid battery.
Jumper Cable Connection & Removal Order
Adhering to the strict 4-step connection and disconnection sequence prevents electrical arcing, voltage spikes, and blown engine control unit (ECU) fuses.
| Cable Order | Clamp Color | Target Vehicle & Terminal | Purpose / Safety Rationale |
| Step 1 (Attach) | Red (+) | Dead Battery Positive Terminal | Establishes main power connection on discharged vehicle. |
| Step 2 (Attach) | Red (+) | Donor Battery Positive Terminal | Connects positive 12V voltage source from good vehicle. |
| Step 3 (Attach) | Black (-) | Donor Battery Negative Terminal | Establishes ground path at functional power source. |
| Step 4 (Attach) | Black (-) | Dead Vehicle Engine Block Ground | Completes ground circuit away from battery gas emissions. |
| Removal Sequence | Reverse Order | Remove Step 4 $\rightarrow$ Step 3 $\rightarrow$ Step 2 $\rightarrow$ Step 1 | Prevents accidental grounding and short circuits during removal. |
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