These instructions apply to the Hyundai i10 Mk3 (AC3) 2020-Present.
For other models, please choose your vehicle here.
If the remote on your Hyundai i10 Mk3 (AC3, 2020–present) only locks the car when you are standing right next to it, flashes weakly, or has stopped responding altogether, the coin cell inside the fob is almost certainly flat. Across the AC3 range the standard key is a three-button folding “flip” remote (the one whose metal blade swings out at the press of a catch), while higher trims fitted with keyless entry and an engine start button carry a smart proximity fob instead. Both take the same inexpensive battery and neither needs reprogramming after a swap — here is how to tell a dying cell from a real fault, the exact battery to buy, and the correct way to open each fob without cracking the case.
How to Tell the Fob Battery Is Dying
- Shrinking range. You have to be almost touching the door handle before the car locks or unlocks. This gradual loss of range is the classic first sign on the i10.
- The fob’s LED goes dim or dark. The little indicator light that blinks when you press lock will fade or stop flashing entirely once the cell voltage drops too low — a quick way to confirm it is the fob, not the car.
- A “key battery low” warning. On keyless (smart-key) i10s the instrument cluster shows a low-key-battery message when the proximity fob is running down.
- Intermittent operation in the cold. A near-flat lithium cell struggles at low temperature, so buttons that work in a warm garage may fail on a frosty morning.
- Push-button start hesitates. On keyless cars, holding the fob against the start button to start the engine (a designed-in backup) is a strong hint the battery is nearly dead.
A coin cell in an i10 remote typically lasts two to four years. If yours is that old and showing any of the above, fit a fresh cell before you start suspecting the receiver or immobiliser.
The Battery You Need
Both the folding flip remote and the smart proximity fob use a single CR2032 — a 3-volt lithium coin cell, 20 mm across and 3.2 mm thick. It is the most common fob battery made, sold in any supermarket, hardware shop or newsagent. Buy a good-quality branded cell: cheap ones sag under the brief high current the transmitter draws and can give poor range even when “new”. One battery does the job whichever key you have.
Method 1 — Folding “Flip” Remote (Most i10 Mk3 Trims)
- Fold the metal key blade closed so the fob is a solid block and easier to hold.
- Find the notch or seam along the edge of the case. Slip a fine flat-blade screwdriver, a coin or a plastic pry tool into it and gently twist to pop the two halves apart. Work slowly around the seam rather than forcing one spot — the plastic clips are small.
- Lift the back cover away to expose the CR2032 sitting in its holder.
- Note which way the old cell faces before you touch it. On the i10 flip remote the new CR2032 normally goes in with the positive (+) side facing up (the marked, lettered face visible). Copying the orientation of the cell you removed is the safest rule.
- Press the fresh cell fully home under its retaining clip, then line the two halves up and squeeze until they click shut all the way round. Test every button.
Method 2 — Smart (Keyless) Proximity Fob
- Release the emergency blade first. Slide the small catch on the fob and pull the mechanical key blade straight out — this is the metal key you would use to unlock the door by hand.
- Insert the blade, a coin or a flat plastic tool into the slot the blade leaves behind and gently twist to split the case along its seam.
- Ease the old CR2032 out of its holder. Note its orientation carefully and fit the new cell exactly the same way — smart fobs do not always seat the cell the same way up as a flip key, so match what you removed rather than assuming.
- Click the two halves back together, then push the mechanical blade back in until it latches.
⚠️ Get the polarity right. A coin cell fitted the wrong way round will not power the fob and can slowly discharge against the contacts — so always copy the exact orientation of the battery you took out. If in doubt, photograph the holder on your phone before removing the old cell.
Make Sure It Took
Stand back a few metres and lock, then unlock, the car. Full range should return straight away and the LED should blink brightly again. On a keyless i10 the “key battery low” message clears the next time the car reads a healthy fob — sometimes instantly, occasionally only after one full drive cycle.
If a Fresh Cell Doesn’t Fix It
- Re-check the polarity and seating. An upside-down or loose cell is the single most common cause of a “new battery that still doesn’t work.” It must sit flat and firm under its clip.
- Clean the contacts. A smear of finger grease or a little corrosion on the terminals is enough to cause dropouts — wipe them with a dry cloth or a cotton bud.
- Confirm the cell is genuinely good. Batteries that have sat in a drawer for years can read low; try another fresh one from a different pack.
- Warning still showing? On some cars the low-key alert only clears after the fob has been read a couple of times. Rarely, a weak car 12 V battery can mimic key faults — if the i10 itself is slow to wake or the dash flickers, have the vehicle battery checked.
New Key or Spare — Why It’s a Dealer Job
Swapping the coin cell leaves the fob’s existing coding untouched, so the remote keeps working with no reprogramming. Cutting and coding a new key is a different matter: the i10’s immobiliser has to be accessed with diagnostic equipment, and a blank remote or smart fob must be ordered and matched against the car’s VIN before it will start the engine. That makes adding a spare or replacing a lost key a job for a Hyundai dealer or an auto-locksmith — so keep the battery in your spare key fresh too, and you are never down to a single working remote.
Frequently Asked Questions
What battery does a Hyundai i10 Mk3 key take?
A single CR2032 3-volt lithium coin cell. The same cell fits both the folding flip remote on standard trims and the smart proximity fob on keyless models.
Which way up does the cell go?
On the flip remote the CR2032 usually seats positive (+) side up. Whichever fob you have, the reliable rule is to fit the new cell the exact same way as the one you removed — fitting it upside down simply leaves the key dead.
Do I need to reprogram the key after changing the battery?
No. A battery swap does not affect the fob’s coding, so the remote works the moment you reassemble it. Only a brand-new key needs programming to the car.
How do I open the i10 key without breaking it?
On the flip key, fold the blade shut and prise the seam apart with a coin or fine flat screwdriver, working gently around the edge. On the smart key, pull out the emergency blade first and use the gap it leaves to split the case. Never force a single point — the plastic clips are delicate.
How long should an i10 key battery last?
Typically two to four years. Heavy use of the remote, or leaving a keyless fob sitting close to the car so it wakes constantly, shortens that.
Can I still drive the i10 if the fob is completely dead?
Yes. Use the mechanical blade hidden in the fob to unlock the driver’s door. On keyless models you can still start the engine by holding the fob against the start button, which the system is designed to detect even with a flat battery, so a dead cell won’t strand you.
If the remote stopped working suddenly right after the car battery was disconnected — rather than fading gradually — the cause is more likely the pairing or a stored fault than the coin cell. You can look up any related code and what it means on autodtcs.com.
Independent guide — not affiliated with Hyundai. Always follow your official service manual and safety precautions. Read our full disclaimer.