A dead battery is the #1 reason drivers call for roadside help. The good news: with jumper cables, a working car, and five minutes, you can usually get yourself moving again. Here's exactly how to do it without damaging either vehicle.
Before you start
What you'll need
- A set of jumper cables (or a portable jump starter)
- A running donor vehicle with a healthy battery (same voltage — almost all passenger cars are 12V)
- Safety glasses and gloves (recommended)
- A clean rag
Step-by-step: jumping a car with jumper cables
Park the cars correctly
Pull the donor car nose-to-nose with the dead car — close enough that the cables reach, but not touching. Put both cars in Park (or Neutral for manual), set the parking brakes, and turn off the donor car's engine.
Turn off all electronics in both cars
Headlights, radio, A/C, phone chargers — all off. Voltage spikes during a jump can fry sensitive electronics that are powered on.
Identify the battery terminals
The positive terminal is marked (+) and usually has a red cover. Negative is (−), usually black. If terminals are crusted with corrosion, wipe them clean with the rag — current can't flow through corrosion.
Connect the cables — in this exact order
- RED clamp → positive (+) terminal of the dead battery
- RED clamp → positive (+) terminal of the good battery
- BLACK clamp → negative (−) terminal of the good battery
- BLACK clamp → bare metal ground on the dead car's engine block (NOT the dead battery's negative terminal)
Why the last clamp goes to a ground, not the battery
Start the donor car and wait
Start the donor car and let it idle for 2–3 minutes. This gives the dead battery time to take a surface charge. Rev the donor engine gently to about 1,500 RPM for the last minute.
Try starting the dead car
Crank for no more than 5 seconds at a time. If it doesn't start, wait 30 seconds and try again. If it still won't start after 3 attempts, the battery is likely dead beyond a jump — or there's another problem.
Disconnect the cables in REVERSE order
- Black clamp from the previously-dead car's ground point
- Black clamp from the donor battery negative
- Red clamp from the donor battery positive
- Red clamp from the previously-dead battery positive
Don't let the clamps touch each other or any metal while the other end is still connected.
Drive — don't just idle
Drive the revived car for at least 20–30 minutes. Idling barely charges the battery; driving lets the alternator do real work. If the car dies again after shutting it off, the battery needs replacement.
Using a portable jump starter (the easier way)
Portable jump packs are the modern solution and don't require a donor car. The process is the same: red to dead positive, black to a ground point, push the start button on the pack, then start the car. Most modern packs have reverse-polarity protection, so even if you connect them backwards they won't damage anything.
When NOT to attempt a jump start
- The battery is visibly damaged, leaking, or frozen
- You hear a fast clicking sound but no crank — usually a starter motor, not a battery
- The car cranks normally but won't start — that's a fuel or ignition problem, not the battery
- You're not 100% sure which terminal is which
Common mistakes that fry electronics
- Reversing the polarity. Connecting red to negative even for a split second can blow fuses, ECU components, or the alternator.
- Letting the clamps touch each other while connected on one end — direct short.
- Disconnecting in the wrong order — same risk as connecting wrong.
- Trying to jump a hybrid or EV's main battery. Most hybrids/EVs have a small 12V battery in the trunk or under the hood that can be jumped, but the high-voltage pack cannot. Check your owner's manual.
Still stuck? We're 30 minutes away.
If you don't have cables, don't have a donor car, or the jump isn't working — call STUCK at 872-250-4864. Our techs carry professional jump packs and battery testers and can tell you on the spot whether you need a new battery or just a boost.
Frequently Asked Questions
How long should I let the dead car run after a jump start?
Let the dead car run for at least 20–30 minutes — ideally while driving — so the alternator can recharge the battery. If the car won't start again after shutting it off, the battery likely needs replacement.
Can I jump start a car in the rain?
Yes, jump starting in light rain is generally safe because the 12V system is low voltage. Keep clamps dry, avoid touching metal contacts together, and don't let cables sit in puddles.
What's the correct order to connect jumper cables?
Red to dead battery positive, red to good battery positive, black to good battery negative, black to a bare metal ground on the dead car (NOT the dead battery's negative terminal). Reverse the order when disconnecting.
Why won't my car jump start even with cables connected?
Common causes: corroded battery terminals, loose cable connections, a completely failed battery (won't hold any charge), a bad starter motor, or the donor car's battery is also weak. If clamps aren't biting clean metal, the current can't flow.
Is it bad for the donor car to give a jump start?
Modern cars handle jump-starting fine, but in rare cases a voltage spike can damage sensitive electronics. To minimize risk, connect the negative clamp to a ground point (not the battery) and let both cars run for a couple minutes before disconnecting.