These instructions apply to the Hyundai i40 Mk1 (VF) 2011-2019.
For other models, please choose your vehicle here.
A flat 12 V battery is the usual reason a Hyundai i40 (VF, 2011–2019) won’t crank. Here is the safe order for jump-starting it from another car. If your i40 has ISG stop-start, read the AGM-battery note at the end.
How to Jump-Start the i40
- Park the donor car close but not touching the i40, and switch both ignitions off.
- Connect one red (+) clamp to the i40’s flat-battery positive terminal, and the other red (+) clamp to the donor battery’s positive terminal.
- Connect one black (−) clamp to the donor battery’s negative terminal.
- Connect the other black (−) clamp to a bare metal point or engine bracket on the i40, well away from the battery — not the flat battery’s negative post.
- Start the donor car and let it run at about 2,000 rpm, then start the i40.
- With the i40 running, remove the clamps in reverse order (last connection off first).
ISG Stop-Start Cars (AGM Battery)
If your i40 has stop-start it uses an AGM battery. After a jump or a disconnect, the stop-start (ISG) function won’t work until the battery sensor re-calibrates — leave the car with the ignition off for about four hours. Only ever fit a genuine AGM battery to an ISG car.
Safety
Use a 12 V donor only; a 24 V supply will ruin the electrics. Keep sparks and flames away from the battery (it gives off hydrogen), and never jump a frozen battery. A manual i40 must not be push- or tow-started, and automatics cannot be push-started.
Frequently Asked Questions
Why doesn’t stop-start work after a jump?
The AGM battery sensor needs about four hours with the ignition off to re-learn the battery state. ISG stays disabled until then.
My i40 keeps going flat — why?
Have the battery and charging system tested. See our car won’t start checklist to narrow it down.
If a warning light stays on after jump-starting, look the code up on our sister site autodtcs.com.
Independent guide — not affiliated with Hyundai. Always follow your official service manual and safety precautions. Read our full disclaimer.