How to jump start a car safely (without frying the electronics)

We get called out to two kinds of jump-start jobs: ones where the customer just needs a hand, and ones where someone tried to jump it themselves and now there's a bigger problem. This guide is for both — the right way to do it, the mistakes that turn a $200 battery job into a $2,000 alternator job, and the cases where you absolutely shouldn't try.

Before you start — three quick checks

1. 1Is it really the battery? Headlights dim or no click at all when you turn the key usually means battery. Crank but no fire means fuel or ignition, not battery — jump starting won't help.
2. 2Look at the battery. If it's swollen, leaking, smells like rotten eggs, or has obvious corrosion mounding on the terminals, do not jump it. Call us.
3. 3Both cars should be off, with keys removed and in park / handbrake on.

The correct jump-start sequence (jumper cables)

1. 1Park the donor car nose-to-nose with the dead car, close enough that the cables reach. Both engines off.
2. 2Red clamp to the POSITIVE (+) terminal of the dead battery first.
3. 3Other end of the red clamp to the POSITIVE (+) terminal of the donor battery.
4. 4Black clamp to the NEGATIVE (-) terminal of the donor battery.
5. 5Other end of the black clamp to an UNPAINTED metal bracket or engine block on the dead car — NOT directly to the dead negative terminal. This prevents sparks near the (potentially gassing) dead battery.
6. 6Start the donor car and let it idle for 2-3 minutes.
7. 7Try to start the dead car. If it doesn't fire within 3-5 seconds, stop and wait another minute.
8. 8Once started, remove the clamps in REVERSE order: black off your car first, black off donor, red off donor, red off your car.
9. 9Drive (don't idle) for at least 20-30 minutes to put real charge back into the battery.

Jump starter packs (lithium booster boxes)

Lithium jump-starter packs (NOCO, Projecta, etc.) are now cheap and brilliant for solo jump starts. They're safer than cables because most have reverse-polarity protection. The sequence is the same as above, just with the pack standing in for the donor car. They won't always start a totally flat battery on a cold morning — you might need to wait 30 seconds with the pack connected before cranking.

Why your car died in the first place

A jump-start gets you running, but it doesn't fix the underlying problem. If your battery is older than 3 years, this is almost certainly the end of its life and you should replace it within the week. If it's newer, the cause is one of:

• Lights or accessories left on overnight (one-off — drive 30 min to recharge and you're fine).
• Parasitic drain (something staying powered when the car is off). Common culprits: faulty dashcam wiring, aftermarket alarms, glove-box lights stuck on.
• Alternator failure — battery isn't being recharged while driving. You'll usually see the battery warning light on the dash.
• Heat damage (see our guide on summer battery failure).

When NOT to jump start

• Swollen, hot, leaking, or visibly damaged battery. Walk away and call us.
• Hybrid or EV main battery (the 12V auxiliary is fine to jump, but follow the manufacturer's specific procedure).
• Battery older than 5 years — even if you get it started, replace immediately. The cells are likely beyond recovery.
• Car still won't start after 3 attempts — something else is wrong. Calling someone out costs less than blowing a starter motor.

Save yourself the guesswork

If you'd rather skip the cables and the alternator-roulette, we'll come out and do it properly — and bring a replacement battery in case it doesn't take a charge. Anywhere in Perth, 24/7, average 30 minutes.