Attach the red positive clamp to the dead battery’s + terminal first; then red to donor +, black to donor −, and black to a metal ground.
What goes first and why
Positive goes first. Start with the red clamp on the dead battery’s + post, then red to the donor’s +, black to the donor’s −, and finish with the last black clamp on unpainted metal under the hood of the car with the dead battery. This order limits sparks near a battery that may vent hydrogen gas and it completes the circuit only at the end, where a grounded engine bracket or strut bolt can handle it.
Correct jumper-cable order (step by step)
- Park nose-to-nose if possible, set both cars to Park (or Neutral) and set parking brakes. Switch off lights and accessories.
- Open hoods. Find the + and − marks or caps. If a remote jump post is provided, use it.
- Attach RED to the DEAD car’s positive (+) terminal.
- Attach the other RED to the BOOST car’s positive (+) terminal.
- Attach BLACK to the BOOST car’s negative (−) terminal.
- Attach the last BLACK to clean, bare metal on the DEAD car, away from the battery, lines, and hoses and hoses.
- Start the BOOST car and let it idle for 2–3 minutes. Lightly raise idle if needed.
- Try starting the DEAD car for up to 10 seconds. If no start, wait a couple of minutes and try again.
- Once running, keep both engines idling for a few minutes before removing cables.
Clamp order cheat sheet
| Step | Connection | Why it matters |
|---|---|---|
| 1 | Red → dead + | Builds the path without sparking at the end point |
| 2 | Red → boost + | Completes the positive side of the circuit |
| 3 | Black → boost − | Prepares the return path on the donor |
| 4 | Black → dead car ground | Final connection away from battery to avoid sparks |
Prep, position, and safety setup
Keep metal tools and jewelry away from the posts. Wear eye protection. Check both batteries and cables for cracks, leaks, or heavy corrosion. If a battery case looks swollen or vents a strong rotten-egg smell, call roadside help instead of jumping. Make sure clamps never touch each other while any end is attached.
Finding terminals and remote posts
Many cars hide the battery or place a remote post under a red cap near the fuse box. If you see a marked positive post and a separate ground stud, use those. They’re designed for jump starts and give you solid metal to clamp on.
Why the last clamp goes to a ground point
Lead-acid batteries can release hydrogen gas during charge. A spark at the negative post can ignite that gas. Clamping the final black lead to an engine hook, a thick strut bolt, or a bare bracket and frame metal keeps any tiny spark away from the battery top.
Which cable goes first when you jump-start a car?
For the connection phase, the positive cable goes first and it goes on the discharged battery before anything else. During removal, the sequence flips to keep sparks away from the battery and to prevent the clamps from touching live metal.
How to remove the cables safely
- Leave both engines idling.
- Remove the BLACK clamp from the ground on the formerly dead car.
- Remove the BLACK clamp from the donor’s − terminal.
- Remove the RED clamp from the donor’s + terminal.
- Remove the RED clamp from the revived car’s + terminal.
- Close panels, stow cables, and drive the revived car for at least 20–30 minutes to recharge.
Portable jump-starter pack: same order, fewer cables
A jump pack removes the second car from the picture, but the clamp order stays the same: red to the dead car’s +, black to a solid ground on the dead car. Most packs have a reverse-polarity alarm; stop and reconnect if it beeps. Keep the pack off hot parts and follow its on/off directions.
Common mistakes to avoid
- Letting the red and black clamps touch while connected to any battery.
- Putting the last black clamp on the dead battery’s − post instead of a ground point.
- Skipping the wait time before cranking and then cranking non-stop.
- Clamping onto painted or oily metal that won’t conduct.
- Connecting to the wrong posts because the red cap was flipped onto the − terminal.
- Jumping a leaking, frozen, or badly swollen battery.
Troubleshooting after a successful start
Once the engine runs, watch and listen. Headlights should look steady, warning lights should clear, and idle should smooth out. If the car stalls at idle, the battery may be weak or the alternator may not charge well. If the dash clock and radio reset every time you start, the battery may be near the end of its life.
If it still won’t start: clues and fixes
| What you notice | Likely cause | Next move |
|---|---|---|
| Dash lights drop to black when you turn the ignition | Weak battery or poor clamp contact | Clean clamps, wait 2–3 minutes, try again |
| Rapid clicking, no crank | Low voltage reaching the starter | Charge longer; check ground point and cable bite |
| Starter turns, engine fires then dies | Immobilizer or fuel issue | Use a spare fob; check fuel level |
| Nothing at all, even with lamps on | Blown main fuse or loose battery cable | Inspect main fuses and cable ends |
| Starts, then stalls at idle | Alternator output low | Drive with loads off and test charging system soon |
Special cases: hybrids, EVs, and tricky locations
Hybrid and EV powertrains still use a 12-volt system for computers and locks. You can jump a discharged 12-volt battery on many of these cars, but never try to boost a high-voltage pack. Some models provide a dedicated under-hood post even if the battery sits in the trunk or under a seat. Follow the under-hood labels and the owner’s manual. If your car offers a dedicated jump point, use it instead of digging for the battery.
Aftercare for the revived battery
Take a longer drive with headlights, rear defogger, and seat heaters off. Short hops won’t bring a weak battery back. If the starter feels slow again the next morning, arrange a battery test. Age, heat, and short trips shorten battery life, and a fresh battery beats repeated boosts.
Cable quality, length, and clamp bite
Thick copper cable moves more current with less drop. A set labeled 4-gauge or 2-gauge helps on trucks and in cold weather. Ultra-long cables are handy for bad parking angles, but longer wire drops voltage. Spring clamps should bite hard and expose clean metal teeth. If a clamp only nibbles at a rounded post, rotate it for better contact or use the side of the jaw where the teeth are sharp.
Cold weather tips
Batteries lose cranking power as the temperature drops. Give the donor a minute or two at a raised idle before you try the first crank. If the dead battery sat outside in deep cold, a five-minute pre-charge often helps more than a long grind on the starter. Do not jump a frozen battery. A case that looks bowed or frosty can burst. If you suspect a freeze, warm the battery first or call for service.
Corrosion and dirty posts
White or green crust on the posts blocks current. You do not need a full cleaning to get moving, but you do need a clean patch of metal. Twist each clamp gently as you seat it to cut through the film. If you carry supplies, a quick spritz of water and a stiff brush can help. Save a proper baking-soda wash for a garage visit, when the battery can be disconnected safely.
Reverse polarity: what happens and how to recover
If a clamp lands on the wrong post, many modern cars trip a protection fuse or the jump pack screams a warning. Stop at once and remove the clamp. Look for a small spark, heat, or a strong odor; if you see any of that, wait before touching things again. Once you correct the hookup, you may still need to replace a blown fusible link. That part sits near the battery in many cars and protects the wiring from damage.
Time on the cables: how long to wait
A dead battery acts like a sponge. Give it time to take charge. Two to five minutes is typical for a car left with the dome light on. After a failed crank, pause a couple of minutes to let heat clear from the starter. On a deeply discharged battery, a 10-minute pre-charge makes the first start more likely.
After the start: what to switch off or on
Keep heavy loads off while the alternator works on the battery. Lights, seat heat, and rear defogger can wait. If the engine idles rough, a low blower setting can steady it. After the drive, shut down and try an immediate restart. If that restart drags, schedule a battery test.
A simple memory trick for the order
Think “red-dead, red-donor, black-donor, black-ground.” Say it out loud while you work. The rhyme sticks, and the last word reminds you to land that final clamp on metal away from the battery.
When to call it and tow
If you see melted plastic, split cases, or liquid seeping from a cap, skip the jump. The same goes for burnt wiring smells, smoking cables, or a car that shuts off the moment you remove the cables. Roadside battery service can test, replace, and recycle the battery and check the charging system so you are not stuck again tomorrow.