Last updated: 22 September 2026
A dead battery is one of the most common reasons drivers get stranded — and also one of the easiest to fix, if you have jumper cables and a second vehicle. Here’s the quick version: connect the cables in the right order (positive-to-positive first, then negative-to-an-unpainted-metal-surface last), run the donor car for a few minutes, then try starting yours. The full steps, the connection order that matters most for safety, and what to do if it still won’t start, are below.
This guide covers cars with a standard 12-volt battery under the hood. If your battery is in the trunk or under a seat (common on some hybrids), check your owner’s manual for the remote jump-start terminals first.
Table of Contents
What You’ll Need
- Jumper cables — at least 10–12 feet long, so both cars don’t need to be right next to each other
- A running vehicle with a healthy battery to act as the “donor”
- Gloves and eye protection (optional but smart — batteries can release corrosive gas)
No second car available? A portable jump-starter pack works the same way and skips the donor-vehicle step entirely.
Step-by-Step: How to Jump Start a Car
- Park the working car close to the dead one, close enough for the cables to reach both batteries, but without the vehicles touching. Turn off both engines and put both cars in Park (or Neutral with the parking brake on).
- Find the battery terminals. The positive terminal is marked with a + and usually has a red or red-tinted cover; the negative is marked −. If you can’t see the battery at all, check your manual — some cars hide it away from the engine bay.
- Connect the cables in this exact order — this order is what keeps the connection safe:
- Red clamp → dead battery’s positive terminal
- Red clamp → donor battery’s positive terminal
- Black clamp → donor battery’s negative terminal
- Black clamp → a bare, unpainted piece of metal on the dead car’s engine block — not the dead battery’s negative terminal (see why below)
- Start the donor car and let it idle for 2–3 minutes. This sends a small charge into the dead battery before you try starting the other car.
- Try starting the dead car. If it doesn’t catch, wait about a minute and try again — but avoid cranking the starter for more than 5 seconds at a stretch, as it can damage the starter motor.
- Once it starts, keep it running for at least 20–30 minutes, or take it for a drive, so the alternator can rebuild the battery’s charge. A jump gets you going; it doesn’t fully recharge the battery on its own.
- Disconnect the cables in reverse order: black from the engine block, black from the donor car, red from the donor car, then red from the car you just started.
Why the Last Connection Matters
The single most important detail in this whole process is where you attach the final black clamp. Never connect it directly to the dead battery’s negative terminal.
Batteries — especially older or partially dead ones — release small amounts of hydrogen gas. Making that last connection right at the battery can create a spark exactly where that gas collects, which is how jump-starting injuries happen. Clamping onto bare metal elsewhere on the engine block still completes the circuit, but keeps any spark well away from the battery itself.
If the Car Still Won’t Start
| What happens | What it likely means |
|---|---|
| No crank at all, or a very slow/weak crank | The battery may be too deeply discharged to accept a jump — it may need replacing rather than jumping |
| Engine cranks fine but won’t fire up | Probably not the battery — could be the fuel system, ignition, or starter |
| Battery looks swollen, is leaking, or heavily corroded | Don’t attempt a jump. Call roadside assistance instead — a damaged battery can be dangerous to work with |
If you’d rather not do this yourself, or the battery looks questionable, AAA offers on-the-spot battery testing and jump-start service as an alternative.
Frequently Asked Questions
Can jump-starting damage my car’s electronics?
It’s uncommon when the cables are connected in the correct order. The real risk is reversed polarity — connecting positive to negative — which can damage sensitive electronics. Double-check each clamp before starting the donor car.
How long do I need to run the donor car before trying to start mine?
2–3 minutes is usually enough for a first attempt. If the car doesn’t start, give it another minute or two rather than repeatedly cranking the starter.
Will I need a new battery after this? Not necessarily.
Not necessarily. If the battery simply drained — lights left on overnight, very cold weather — it will typically recover once it’s had time to recharge while driving. If the same battery keeps dying every few days, that’s usually a sign the battery itself needs replacing — see our guide to changing a car battery.
Is it safe to jump-start a car in the rain?
Best avoided if you have another option. If you must do it in wet conditions, keep the clamp connection points as dry as you can and avoid touching the metal clamps directly.
What if I don’t have a second car?
A portable jump-starter (battery pack) does the same job without a donor vehicle — connect its clamps the same way, in the same order.
Dealing with car trouble on the road? Here’s how to change a flat tire too.
Sources and further reading
This article was researched and fact-checked by the AutoExpertsHub editorial team against the sources above and manufacturer documentation. Learn how we work in our Editorial Policy. Spotted an error? Let us know.
