Quick answer
Park the cars nose to nose with both engines off. Clamp red to the dead battery's positive terminal, then red to the good battery's positive terminal, then black to the good battery's negative terminal, and the last black clamp to bare metal on the dead car's engine block — never to the dead battery's negative post. Start the donor car, wait 2–5 minutes, then start the dead car with a 10-second crank. Remove the clamps in reverse order and drive for at least 30 minutes.
A dead battery is the most common reason a car refuses to start, and the fix takes ten minutes with nothing but a pair of jumper cables and a second car. The clamps are color-coded for a reason: connect them in the wrong order or place the final clamp carelessly and you can damage both cars — or, in the worst case, make a small spark right next to a battery that is venting hydrogen gas.
The honest headline first: a jump start gets you going. It does not fix a dying battery. If your car needs a jump more than once a month, the battery is on its way out — replace it before it leaves you stranded in a parking lot with no cables nearby.
1. Park the cars close, engines off, everything off
Position the donor car so the cables comfortably reach — nose-to-nose or side by side. Both engines must be off, both parking brakes on, and both cars in Park (or neutral with the handbrake). Never let the bumpers touch.
Switch off everything that draws power: headlights, radio, heater blower, heated seats, rear defroster. Any draw competes with the jump and slows the whole process down.
2. Find both batteries and give them a quick look
The battery is usually under the hood, but some cars keep it in the trunk or under a seat — and many hybrids have remote jump terminals under the hood even when the battery is elsewhere. Check the owner’s manual if you cannot find it.
Before clamping, inspect the dead battery:
- Corroded terminals (white or green dust) — brush the dust off the terminals first; corroded contacts are the number one reason a jump fails.
- Cracked or swollen case, or leaking acid — do not jump it. Replace the battery.
- Frozen battery — if it has been below freezing and the battery is dead, a frozen battery can explode when current passes through it. Do not jump; let it thaw or get a replacement.
3. Red clamp on the dead battery’s positive terminal
The positive terminal is the one marked +, usually with a red plastic cover. Clamp the red cable to the metal post itself, not the cover.
4. Other red clamp on the good battery’s positive terminal
Run the other red clamp to the + terminal of the donor battery. Same rule: metal on metal.
5. Black clamp on the good battery’s negative terminal
The negative terminal is marked − and is usually black. Clamp the first black end here.
6. Final black clamp on bare metal — never the negative post
This step is what separates a safe jump start from a dangerous one. The last black clamp goes on an unpainted metal bolt, bracket or strut on the dead car’s engine block, at least 30 cm away from the battery. Do not attach it to the dead battery’s negative post.
Why: a dying battery can be venting hydrogen gas, and a single spark near the terminals can ignite it. Grounding the final clamp on the engine block moves that spark as far from the battery as possible.
| Clamp | Connect to |
|---|---|
| Red 1 | Dead battery positive (+) terminal |
| Red 2 | Good battery positive (+) terminal |
| Black 1 | Good battery negative (−) terminal |
| Black 2 | Bare metal on the dead car’s engine block — never the negative post |
Keep the four clamps away from each other and clear of moving parts like the radiator fan.
7. Start the donor car and wait 2–5 minutes
Start the donor car and let it idle. Gently raise the revs to about 1,500–2,000 rpm for a couple of minutes — the alternator charges much more efficiently above idle.
If you follow the steps and nothing happens when you try to start the dead car, check the clamps: some batteries have plastic covers that look like metal at a glance. The red clamp sitting on a plastic cap is the most common silent failure.
8. Start the dead car — 10 seconds maximum
Turn the key (or press the Start button, with the key fob inside). Crank for no more than 10 seconds, then wait about 30 seconds before trying again. Two to three attempts is the limit.
If the engine turns over but will not start after a few attempts, stop cranking: the problem is not the battery. A starter that cranks for minutes on end overheats and can die with it.
9. Remove the clamps in reverse order, then drive 30 minutes
With both engines running, remove the clamps in the exact reverse order: black first from the dead car’s engine block, then black from the good battery’s negative terminal, then red from the good battery, and red from the dead battery last.
Then drive. At least 30 minutes of driving lets the alternator put back the energy the starter used. Idling with the cables still attached for 10–15 minutes also works — a five-minute trip to the shop does not.
If it still will not start: battery vs. alternator
A jump start only proves the right amount of power is arriving — it says nothing about what broke. Three patterns tell you what is going on:
- Starts only with a jump, dead again next morning — the battery is worn. Batteries last about 3–5 years. Have it tested at a garage (most do it free) and replace it.
- Battery warning light stays on after the jump — the alternator is not charging. You have maybe 30–60 minutes of driving before the car dies again, so drive straight to a shop.
- Rapid clicking, weak interior lights — a nearly empty battery or badly corroded terminals. Clean the terminals and try again with a longer charge.
How to jump start a car without another car
Portable jump starter packs (battery packs with clamps — brands like NOCO make a popular line) replace the donor car entirely. They are the practical choice if you drive alone in areas with little traffic: no second car means your own battery pack is the only way out.
The procedure is identical, minus the donor car: red clamp to the positive terminal, black clamp to bare metal on the engine block, switch the pack on, wait for the ready light, start the car within a few minutes, then disconnect in reverse order. Check the peak current rating before you buy one — around 500 amps covers most gas engines, while diesels and large SUVs need more. Recharge the pack every few months, or it will be empty the day you need it.
What to keep in the car
- Jumper cables (or a portable pack).
- A phone charger or power bank — jump starters have USB ports, but your phone is the thing that saves you if the jump fails.
- A small flashlight and hi-vis vest for doing this at night or on the roadside.
A set of cables costs little and weighs almost nothing — and a jump starter pack is exactly what an emergency fund is for, so pick one up before you need it. And if you are planning a weekend road trip, get the battery tested first: on a rainy Sunday in the middle of nowhere is the wrong place to meet a tired battery for the first time.
How to prevent the next dead battery
- Winter is the killer. Cold cuts a battery’s cranking power by a third, while the heater and lights demand more. Test the battery every autumn.
- Short trips never fully recharge the battery. If your commute is ten minutes, put the battery on a trickle charger once a month.
- Check the terminals once a year. Clean corrosion with a paste of baking soda and water, then grease the posts.
- Watch the warning signs. Slow cranking on a cold morning, dim interior lights at start, or needing a jump twice in a month — the battery is telling you it is done.
- Buy a battery by age, not by failure. A four-year-old battery that is still working is living on borrowed time; replace it on a weekend, not on a Monday morning in January.
Do these, keep cables in the trunk, and a dead battery becomes a ten-minute annoyance instead of a stranded evening.
Hero image: Tony Webster, CC BY 2.0, via Wikimedia Commons.
Frequently Asked Questions
Can you jump start a car without another car?
Yes — a portable jump starter pack does the same job. Connect the red clamp to the positive terminal, the black clamp to bare metal on the engine block, switch the pack on, wait for the ready light, and start the car within a few minutes. Check the pack's peak current rating: around 500 amps covers most gas engines, while diesels and large SUVs need more.
How long should you leave the cars connected?
Leave them connected 2–5 minutes before starting the dead car, then keep the engine running. Drive for at least 30 minutes afterwards so the alternator can recharge the battery. A five-minute drive to the corner shop is not enough — and if the car only starts with a jump start, the battery is worn and should be tested.
Which battery terminal do you connect first?
Red (positive) on the dead battery first, then red on the good battery, then black (negative) on the good battery, and finally the second black clamp on bare metal on the dead car's engine. The last clamp goes to metal, never to the dead battery's negative post — that is where a spark could ignite hydrogen gas.
Why won't my car start even with a jump start?
A jump start only supplies power — if the engine turns over but still won't start, the problem is fuel, the starter, the immobilizer or a battery that cannot hold a charge. If the battery warning light stays on after the jump, the alternator is not charging and you should drive straight to a shop.
