A dead battery is one of the most common reasons a car won't start — and jump starting it takes five minutes if you connect the cables in the right order. Get the order wrong, though, and you risk sparks near the battery or damaging sensitive electronics.
This guide walks through jump starting a car safely, the exact clamp order that matters, and what a repeated no-start actually tells you.
What you need
- ✓A set of jumper cables (or a portable jump pack).
- ✓A working 'donor' vehicle with a charged battery of the same voltage (most cars are 12V).
- ✓Both engines off to start, and the handbrakes on.
Step-by-step
- 1
Position and switch off
Park the working car close (not touching), both in park/neutral with handbrakes on and ignitions off. Pop both bonnets and locate the batteries and their + and − terminals.
- 2
Connect the red (positive) clamps
Attach one red clamp to the dead battery's positive (+) terminal, then the other red clamp to the good battery's positive (+) terminal.
- 3
Connect the black (negative) clamps carefully
Attach one black clamp to the good battery's negative (−) terminal. Attach the other black clamp to a bare metal ground point on the dead car's engine block — NOT the dead battery's negative terminal. This keeps any spark away from battery gases.
- 4
Start the donor, then the dead car
Start the working car and let it run a couple of minutes to feed some charge. Then try to start the dead car. If it cranks and starts, leave it running.
- 5
Remove cables in reverse order
With the car running, remove the clamps in the exact reverse order: black from the ground point, black from the donor, red from the donor, red from the revived car.
- 6
Keep it running
Drive or idle the revived car for 20–30 minutes so the alternator can recharge the battery. Turning it straight off may leave you stranded again.
Examples
- After leaving the lights on overnight, a 12V car jump-started in one attempt and held a charge after a 30-minute drive — a classic flat, not a failed, battery.
- A car that clicks but won't crank even with a strong jump often points to a failing starter or a battery at the end of its life, not just a flat charge.
Tips
- →Order matters: red to dead +, red to good +, black to good −, black to bare metal on the dead car.
- →Grounding the last black clamp to the engine block, not the battery, avoids igniting battery gases.
- →A portable jump pack means you don't need a second car — keep one charged in the boot.
- →If the battery is visibly swollen, leaking or cracked, don't jump it — replace it.
- →Never let the clamps touch each other while any are connected to a battery.
Common mistakes
- Clamping the last black to the dead battery. Ground it to bare engine metal instead to keep sparks away from battery gases.
- Mixing up the order. Follow red-dead, red-good, black-good, black-ground; reverse to remove.
- Switching the car off too soon. Drive or idle 20–30 minutes so the alternator recharges the battery.
- Jumping a damaged battery. A swollen, leaking or cracked battery must be replaced, not jumped.
Conclusion
Jump starting is safe and quick when you respect the clamp order and ground that final black clamp to the engine, not the battery. Let the car run to recharge afterwards — and if it keeps dying, get the battery and charging system tested rather than jumping it again and again.