These instructions apply to the Hyundai Kona Mk2 (SX2) 2023-Present.
For other models, please choose your vehicle here.
When the smart key on the second-generation Kona shows a low-battery message or only works at close range, the coin cell inside needs replacing. It takes a single CR2450 battery and no recoding, so you can do it at home in a couple of minutes.
Before you start
- Have a fresh CR2450 coin cell ready.
- Handle the new cell by its edges and note which way up the + side faces before removing the old one.
- Slide the mechanical key blade out of the smart key.
- Use the blade slot to gently prise the fob open along its seam.
- Lift out the old CR2450 coin cell.
- Fit the new CR2450, observing the same polarity as the cell you removed.
- Press the two halves back together until they click, and reinsert the mechanical key blade.
- Test lock, unlock and start to confirm the fob works again.
FAQ
Do I need to reprogram the key after changing the battery?
No. Swapping the coin cell does not affect the key’s coding, so the fob keeps working immediately once the new battery is fitted correctly.
My fob is dead and the car will not detect it. Can I still start?
Yes. With the brake pressed, touch the smart key directly to the Start button. The car reads the transponder at close range and lets you start even with a flat fob battery, so you can drive to get a replacement cell.
Which battery does the smart key use?
A single CR2450 lithium coin cell. Using the correct type matters, as a thinner or lower-capacity cell may not seat properly or may give a short service life.
Independent guide — not affiliated with Hyundai. Always follow your official service manual and safety precautions. Read our full disclaimer.