The short answer
Connect the red (+) clamp to the dead battery's positive, the other red (+) to the donor's positive, the black (−) to the donor's negative, and the last black (−) to bare metal on the dead car's engine block — not its battery's negative post. Start both, drive 15–20 minutes, then disconnect in reverse order.
What do you need to jump-start a car?
You need three things: a working donor vehicle with a charged 12-volt battery, a set of jumper cables (or a portable lithium jump pack), and both batteries' positive and negative terminals identified. Positive is marked "+" or red; negative is "−" or black. Park the cars close but not touching, both in park or neutral with ignitions off.
- Jumper cables: heavier gauge (4–6 AWG) carries more current and works better on larger engines.
- A donor vehicle with a healthy battery — or a portable jump-starter pack, which removes the need for a second car.
- Eye protection and gloves are worth wearing; batteries contain corrosive acid and vent hydrogen.
- The owner's manual if either car is a hybrid or EV, since the jump point may not be the battery itself.
Before you start, confirm the dead battery isn't cracked, leaking, or visibly bulging — a damaged battery should not be jumped. If the battery keeps going flat after jumps, see why a car battery keeps dying.
In what order do you connect jumper cables?
Connect in this order: red clamp to the dead battery's positive (+), the other red clamp to the donor's positive (+), the black clamp to the donor's negative (−), and the final black clamp to unpainted metal on the dead car's engine block — away from the battery. This last step grounds the circuit while keeping any spark clear of battery fumes.
- Red to dead positive. Clamp one red (+) clip to the positive terminal of the dead battery.
- Red to donor positive. Clamp the other red (+) clip to the positive terminal of the good battery.
- Black to donor negative. Clamp one black (−) clip to the negative terminal of the good battery.
- Black to bare metal on the dead car. Clamp the final black (−) clip to an unpainted metal bolt or bracket on the dead car's engine block — not the dead battery's negative post.
- Start the donor, then the dead car. Start the donor vehicle, let it run two to three minutes, then start the dead car.
- Disconnect in reverse. Once it's running, remove the clamps in the exact reverse order: bare-metal black, donor black, donor red, dead red.
Consumer Reports and AAA both specify grounding the final clamp to bare metal rather than the dead battery's negative terminal, because that connection is the one most likely to spark near hydrogen gas.
How long should you run the engine after a jump-start?
Run or drive the revived car for at least 15 to 20 minutes so the alternator can recharge the battery. A jump only supplies enough power to crank the engine; the battery itself is still nearly empty. Steady driving recharges faster than idling, so take it on a highway rather than letting it sit.
- Don't shut it off immediately. Stopping the engine within a couple of minutes can leave the battery too low to restart.
- Drive, don't idle. The alternator spins faster and charges more at driving speeds than at idle.
- Skip heavy loads. Hold off on the AC, heated seats, and stereo while the battery rebuilds its charge.
- Won't restart after? If it dies again after a 20-minute drive, the battery or alternator is failing, not just discharged.
The 15–20 minute recharge guidance reflects standard advice from Consumer Reports and AAA. A battery that repeatedly needs jumps is near the end of its life — see how long a car battery lasts.
When should you replace the battery instead of jump-starting it?
Replace the battery, rather than relying on jumps, once it's 3 to 5 years old or won't hold a charge after a proper recharge. Most car batteries last 3–5 years, and one that dies again within a day or two of a 20-minute drive has lost capacity it won't recover. Repeated jump-starts are a workaround, not a fix.
- Age 3–5 years: a battery past this window is on borrowed time even if it still cranks.
- Won't hold a charge: if it dies again soon after a recharge, the cells are worn out.
- Slow cranking and dim lights on cold mornings signal a weakening battery before it strands you.
- Free load test: auto parts stores like AutoZone and O'Reilly test batteries free and confirm whether it holds spec.
If the battery keeps draining for reasons other than age — a parasitic drain or a bad alternator — read why a car battery keeps dying before swapping it. For the full timeline, see how long a car battery lasts.
Can you jump-start an EV or hybrid the same way?
You can jump the 12-volt battery in many EVs and hybrids, but never the high-voltage drive battery. Most EVs and many hybrids also can't be used as the donor vehicle — their 12-volt systems aren't built to deliver a high cranking surge. The 12-volt jump point and procedure vary by model, so the owner's manual is essential before connecting cables.
- Only the 12-volt battery: it powers the computers and door locks; the high-voltage pack is never jumped.
- Often not a donor: using an EV or hybrid to jump another car can damage its electronics.
- Hidden jump points: many EVs route the positive terminal to a remote post under a fuse-box cover, not the battery.
- Check the manual first: connecting to the wrong point can blow fuses or trip safety systems.
Edmunds notes that EV and hybrid jump procedures differ enough that the owner's manual should be your first stop, since locations and limits vary widely by automaker.
Frequently asked questions
Why does the last jumper-cable clamp go to bare metal, not the battery?
Because a charging lead-acid battery vents flammable hydrogen gas, and the final connection is the one most likely to spark. Clamping the last black clip to an unpainted metal ground on the dead car's engine block, away from the battery, keeps any spark clear of those fumes and lowers the risk of ignition.
How long should you let a car run after a jump-start?
Run or drive the revived car for at least 15 to 20 minutes so the alternator can recharge the battery. Idling alone charges slowly, so highway driving is better. If you shut the engine off too soon and it won't restart, the battery is likely worn out and the jump only masked the problem.
Can you jump-start an electric car or hybrid the same way?
You can jump-start the 12-volt battery in many EVs and hybrids, but never the high-voltage drive battery. Most EVs and hybrids also cannot serve as the donor vehicle. Locations and steps vary by model, so check the owner's manual for the 12-volt jump point before connecting any cables.
What should you do if the dead car still won't start after a jump?
Double-check that all four clamps are tight and making clean metal contact, rev the donor car to about 2,000 rpm, and wait several minutes. If it still won't crank, the battery is likely dead or there is a deeper electrical fault. A battery older than 3 to 5 years that won't hold a jump usually needs replacement.
Sources
CarsLens is editorial guidance, not individualized advice. This page draws on Consumer Reports, AAA, and Edmunds.