How to jump start a car safely

Before you start

A flat battery is the most common “won’t start” Google query on cold UK mornings. Jump leads work — if you use the right order and the right donor points. Get it wrong and you can fry electronics. Modern cars, start-stop systems and EVs with a 12V battery all have handbook footnotes people skip.

What you’ll need

• Quality jump leads or a lithium jump pack rated for your engine size
• Donor car with a healthy battery (same voltage system)
• Handbook for remote earth / jump points
• Eye protection and gloves

Watch a good how-to

Popular walkthroughs that match this job. Watch for technique — always follow your handbook for torque figures, jacking points and fluids.

Step-by-step guide

1. 1

   Read the handbook jump-start page. Many cars want the positive on a stud under a red cap and the negative on a marked earth point — not always straight on the battery.

2. 2

   Both cars in Park/Neutral, parking brakes on, ignitions off, accessories off.

3. 3

   Red clamp to dead battery positive (+), other red to donor positive (+).

4. 4

   Black clamp to donor negative (−), then black to an unpainted earth on the dead car (engine bracket / designated stud) — not casually onto a weak battery negative if the handbook says otherwise.

5. 5

   Start the donor, wait a minute, then try the dead car. If it starts, remove clamps in reverse order.

6. 6

   Drive at least 20–30 minutes or use a proper charger — a 5-minute idle often leaves you flat again tomorrow.

Pro tips

• A jump pack avoids finding a donor in a supermarket car park.
• Repeated flat batteries mean alternator, parasitic drain or an old battery — test, do not keep jump-starting forever.
• After a jump, some cars need windows/clock/radio reset and a few drive cycles for idle relearn.

FAQs