These instructions apply to the Infiniti Q30 (H15) 2015-2019.
For other models, please choose your vehicle here.
When the remote for an Infiniti Q30 (H15, 2015–2019) only locks the car from arm’s length, needs a second or third press, or stops responding altogether, the coin cell inside the key is almost always the reason. The Q30 is worth understanding on its own terms here: although it wears an Infiniti badge, it was built on the Mercedes-Benz A-Class / GLA platform, and it carries a Mercedes-style SmartKey rather than the usual Nissan-Infiniti Intelligent Key. That matters for two reasons — the fob opens differently from other Infinitis, and it takes a thinner CR2025 cell, not the CR2032 you’ll read about for the rest of the range. Get those two details right and it’s a five-minute job.
How to Tell the Fob Battery Is Dying
- Shrinking range. You find yourself standing right beside the car, or holding the key against the door handle, before it will lock or unlock. This is usually the first sign.
- You have to press twice. A cell that is nearly flat can still fire once the button is jabbed a few times, but the intermittent response is a warning that it is on the way out.
- A key-battery message in the cluster. Because the Q30 is a keyless car, it watches the fob’s signal strength and will show a low-key-battery warning on the dash display when the cell is weak.
- Keyless start hesitates. The car may ask you to hold the key against the start button before the engine will crank — the backup method it uses when it can no longer read the fob at normal range.
- Worse in the cold. Lithium cells lose voltage in low temperatures, so a marginal battery often fails first on a frosty morning and seems to recover by mid-afternoon.
A CR2025 in a Q30 SmartKey typically lasts two to four years. If yours is older than that and doing any of the above, fit a fresh cell before you start suspecting the car’s receiver or immobiliser.
The Battery You Need
The Q30 SmartKey takes a single CR2025 3-volt lithium coin cell. This is the Mercedes-derived specification for this key, and it is the detail people get wrong most often — the CR2025 is the same 20 mm diameter as the common CR2032 but noticeably thinner (2.5 mm versus 3.2 mm). Buy a good-quality branded cell; budget cells sag under the brief high current the transmitter draws and can give short range even when brand new.
How to Change the Q30 SmartKey Battery
- Slide out the emergency key blade. Press the small release catch on the fob and pull the mechanical metal blade straight out of the body. It comes fully away and doubles as a handy lever for the next step.
- Lift off the cover. With the blade removed, a slim cover panel unclips from the fob in the Mercedes SmartKey style. Slide it in the direction the blade came out and lift it away, or gently work a fingernail or a flat plastic tool into the seam to release the clips. Take it steadily — the case is plastic and you should feel it unclip rather than crack.
- Note the cell’s orientation, then lift it out. Before you touch anything, look at which face of the coin is showing. On the Q30 the CR2025 sits with its positive (+) side facing down, against the base of the battery bay — but the reliable rule is simply to copy whatever you see before you remove the old one.
- Drop in the new CR2025 the same way round. Handle it by the edges — skin oils on the flat faces can shorten a coin cell’s life — and seat it firmly under its retaining clip.
- Refit the cover and blade. Press the cover back on until the clips click home, then slide the emergency key blade back into the body until it latches. Test every button.
⚠️ Get the polarity right. A coin cell fitted upside down will not power the fob, and left in the wrong way it can slowly discharge and even damage the key’s electronics — so always match the orientation of the cell you took out rather than guessing.
Confirm It Worked
Stand back several metres and lock, then unlock, the car. Full range should return straight away. Any key-battery warning in the cluster usually clears on its own the next time the Q30 reads a healthy fob — sometimes instantly, sometimes after one short drive cycle rather than the moment you close the door.
If a Fresh Cell Doesn’t Fix It
- Re-check the polarity and seating. An upside-down or loosely seated cell is by far the most common reason a “new” battery changes nothing. The coin must sit flat and firm under its clip.
- Clean the contacts. A smear of finger grease or light corrosion on the metal terminals is enough to cause dropouts — wipe 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. And rarely, a weak car 12 V battery can mimic key faults — if the Q30 itself is slow to wake or the interior lights are dim, look at the main battery next.
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 you close the cover. A new key is a very different matter. Because the Q30 shares its Mercedes-based electronic architecture, a replacement SmartKey has to be ordered against the car’s VIN and married to the immobiliser with dealer-level diagnostic equipment — it is not a job an ordinary locksmith can always do, and blank fobs are not cheap. The sensible move is to keep the battery in your spare key fresh too, so you are never down to a single working fob and forced into that expense unexpectedly.
Frequently Asked Questions
What battery does an Infiniti Q30 key fob take?
A single CR2025 3-volt lithium coin cell. The Q30 uses the Mercedes-style SmartKey from its A-Class / GLA platform, which takes the thinner CR2025 rather than the CR2032 fitted to most other Infinitis.
Can I use a CR2032 instead of a CR2025?
It is best not to. A CR2032 is the same width but thicker, so while it may squeeze in and work briefly, it can strain the contacts and the cover clips. Fit the correct CR2025 that the key was designed for.
Which way up does the battery go?
On the Q30 SmartKey the CR2025 seats with its positive (+) side facing down into the battery bay. The safest approach is always to note the orientation of the cell you remove and fit the new one exactly the same way.
Do I need to reprogram the key after changing the battery?
No. Replacing the coin cell does not affect the fob’s coding, so it pairs with the car straight away. Only a brand-new or replacement key needs programming.
How long should a Q30 key battery last?
Usually two to four years. Leaving a keyless fob sitting close to the car so it wakes constantly, or heavy daily use of the remote, will shorten that.
Can I still drive the Q30 if the fob battery is completely dead?
Yes. Use the emergency metal blade hidden in the fob to unlock the driver’s door, then hold the key against the marked spot on the start button — the keyless system is designed to still start the car with a flat fob, so a dead cell will not strand you.
If the remote died suddenly right after the car’s 12 V battery was disconnected or went flat — rather than fading gradually — the problem is more likely the electronics waking up than the coin cell, and the car may have logged a fault in the process. You can look up what any stored code means on autodtcs.com.
Independent guide — not affiliated with Infiniti. Always follow your official service manual and safety precautions. Read our full disclaimer.