These instructions apply to the Kia Stonic Mk1 (YB) 2017-Present.
For other models, please choose your vehicle here.
When the remote on a Kia Stonic (YB, 2017–present) starts working only from arm’s length, flashes nothing when you press a button, or throws a low-key warning on the cluster, the cause is nearly always the coin cell inside the fob rather than anything wrong with the car. The Stonic shipped with two different keys depending on trim: a folding “flip” remote (the blade swings out of the body) on lower-spec cars, and a smart keyless-entry fob with push-button start on higher trims. Both take the same battery, but they open in slightly different ways — here is the exact method for each, how to be sure it really is the battery, and why cutting a brand-new key is the one part of this job you can’t finish at home.
How to Tell the Fob Battery Is Dying
- Shrinking range. You find yourself standing right next to the Stonic — or pressing the fob against the door handle — before it will lock or unlock. This is almost always the first sign.
- No LED on the button press. The little indicator light on the flip remote stops flashing when you press a button. If the LED is dead, the cell is flat — a quick way to confirm the fob is at fault, not the receiver.
- A “key battery low” message. Smart-key Stonics show a low-key-battery warning in the instrument cluster when the fob’s cell is getting weak. Don’t ignore it — it usually appears weeks before the fob quits entirely.
- Intermittent response, worse in the cold. Buttons that work sometimes and not others, especially on a frosty morning, point to a near-flat cell that can’t hold voltage under load.
A coin cell in a Stonic fob typically lasts two to four years. If yours is around that age and doing any of the above, fit a fresh battery before you start suspecting the immobiliser or the car’s own 12 V battery.
The Battery You Need
Both the folding remote and the smart fob use a single CR2032 3-volt lithium coin cell. It’s the most common fob battery there is — any supermarket, hardware shop or petrol station will have one. Buy a good-quality branded cell rather than the cheapest multipack: budget cells sag under the brief burst of current the transmitter draws and can give poor range even when they read as “new” on a meter.
Method 1 — Folding “Flip” Remote
- Fold the metal blade closed so the fob sits flat and is easier to hold.
- Find the seam that runs around the edge of the case. Insert a slim flat tool into the slot and gently prise the two halves apart. Some flip remotes instead have a small cross-head screw holding the battery cover — if you see one, undo it with a fine Phillips screwdriver and lift the cover off.
- Note which way the old cell sits, then ease it out. Fit the new CR2032 the same way up as the one you removed — copy the orientation exactly.
- Press the case back together until the seam clicks flush (or refit and gently retighten the screw — don’t force it, the housing is plastic), then test every button.
Method 2 — Smart (Keyless) Fob
- Release the emergency blade first. Slide or press the small catch on the fob and pull the mechanical key blade straight out of the body.
- Insert a slim flat tool (or the blade itself) into the slot the blade leaves behind and gently prise the two halves of the case apart. Work your way round the seam rather than levering hard at one point.
- Lift out the old cell and drop in the new CR2032 in the same orientation — match the writing/plus side to the cell you took out. On many Kia smart fobs the printed face sits downward, but always let the old cell be your guide rather than assuming.
- Snap the halves back together all the way round, then slide the emergency blade home until it latches.
⚠️ Get the polarity right. Kia’s own instructions warn that a cell fitted the wrong way round will quietly discharge and can leave the key unusable — so before the old battery comes out, look at which face is up and put the new one back exactly the same way.
Check It Worked
Stand back a few metres and lock, then unlock, the Stonic. Full range should return straight away and the flip remote’s LED should flash cleanly on each press. On a smart-key car the “key battery low” message clears once the vehicle next reads a healthy fob — sometimes instantly, sometimes after a drive cycle, so don’t panic if it lingers for a few minutes.
If a Fresh Cell Doesn’t Fix It
- Re-check the orientation and seating. An upside-down cell is the single most common mistake — and the battery must sit firmly under its clip against clean contacts.
- Wipe the contacts. A smear of finger grease or a trace of corrosion on the terminals is enough to cause dropouts; clean them with a dry cloth before blaming the fob.
- 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 Stonic itself is slow to wake, look at the vehicle battery too.
- LED still dead with a known-good cell? If a new branded CR2032 the correct way up gives nothing, the transmitter itself may have failed — uncommon, but it happens after water ingress.
New Key or Spare — Why It’s a Dealer Job
Swapping the coin cell leaves the fob’s existing coding untouched, so nothing needs reprogramming and the key works the moment it powers back up. Cutting and coding a new key is a different matter: the Stonic’s immobiliser has to be accessed with diagnostic equipment, and a blank smart fob must be ordered and paired against the car’s VIN. That makes adding a spare or replacing a lost key a job for a Kia dealer or an auto-locksmith — so keep the battery in your spare fresh too, and you’re never down to a single working key.
Frequently Asked Questions
What battery does a Kia Stonic key fob take?
A single CR2032 3-volt lithium coin cell. It’s the same size whether you have the folding flip remote or the smart keyless fob.
Does the flip key use a different battery from the smart key?
No — both the folding remote and the smart fob use the CR2032. The only difference is how the case opens: the flip key may have a small screw or a pry seam, while the smart key opens by prising the seam after you remove the emergency blade.
Which way up does the battery go?
Match the cell you removed. There isn’t a single “always plus-up” rule across both fob types, so note the orientation before you lift the old battery out — fitting it the wrong way round can flatten it and disable the key.
Do I need to reprogram the key after changing the battery?
No. A battery swap doesn’t touch the fob’s coding, so it works immediately. Only a brand-new key needs programming to the car.
How long should a Stonic key battery last?
Usually two to four years. Heavy remote use — or leaving a smart fob sitting near the car so it keeps waking to talk to it — will shorten that.
Can I still drive the Stonic if the fob is completely dead?
Yes. Use the mechanical blade hidden in the fob to unlock the driver’s door, and on smart-key cars you can still start the engine by holding the fob against the start button as the handbook describes — a flat cell won’t strand you.
If the remote died suddenly right after the car battery was disconnected — rather than fading over weeks — the fault is more likely the pairing or a stored electrical code than the coin cell. You can look up what a logged fault code means on autodtcs.com.
Independent guide — not affiliated with Kia. Always follow your official service manual and safety precautions. Read our full disclaimer.