Car Key Battery Replacement: Which Battery Every Key Takes and How to Change It (2026)

The battery in a car key lasts two to four years, then the car starts asking you to hold the key closer, the doors stop unlocking from across the car park, and one morning nothing happens at all. The fix costs about two euros and takes five minutes. This guide tells you which battery your key takes, how to open it without snapping a clip, and what to do if the car still won't start afterwards.

How to tell the battery is dying

A key does not usually die overnight. It gives you a few weeks of warning first:

• Range shrinks. You used to unlock from across the street; now you have to be next to the door.
• Keyless entry becomes patchy. The handle works on the second or third pull instead of the first.
• A message on the dash. Almost every car since 2010 shows something like "Key battery low" or "Replace remote battery" on start-up.
• The car asks you to hold the key to a marked spot on the steering column or start button to get going.

If you see any of these, change the battery now, while the key still works well enough to open the car. The emergency procedure below works, but it is a lot less convenient in the rain.

Which battery does your car key take?

This table covers the keys we see most. Treat it as a starting point, not gospel: carmakers change suppliers mid-generation, and a replacement key ordered years later can take a different cell from the original. The battery you remove has its code printed on the flat side. Buy that one.

Brand	Most common battery	Also seen	How the key opens
Audi	CR2032	—	Remove the emergency blade, slide the back cover off (2013 onwards) or lever the halves apart at the seam (flip key)
BMW	CR2032	Display Key is rechargeable; some early F01/F10 keys are rechargeable	Remove the blade, push its tip into the slot at the base, lever the cover up. Full BMW guide
Mercedes-Benz	CR2032 (flat key)	2 × CR2025 (chrome arrow key)	Remove the blade, push it into the slot on the end of the key, the battery cover pops off. Full Mercedes guide
Porsche	CR2032	—	Remove the blade, push the tip into the slot on the back, twist to lift the cover
Volkswagen, Škoda, SEAT, Cupra	CR2032	—	Flip key: lever the two halves apart at the seam behind the blade. Keyless key: slide the back cover off
Volvo	CR2032 (2016 onwards)	CR2430 (roughly 2008 to 2016)	Press the button, slide the blade out, lever the back cover up from the slot
Range Rover, Land Rover, Jaguar	CR2032	—	Slide the back cover off, the battery sits in a tray underneath
Tesla	CR2032	—	Press the thin side of the fob, the back cover lifts away. Key card has no battery
Toyota	CR2032	CR1632 (many 2012 to 2019 smart keys)	Remove the blade, lever the halves apart at the slot it came out of
Lexus	CR1632 or CR2032	—	Same as Toyota: remove the blade, lever at the slot
Honda	CR2032 (smart key)	CR1616 (older flip key)	Remove the blade, insert it in the notch, twist
Mazda	CR2025	—	Slide the release, remove the blade, lever the halves apart at the slot
Ford	CR2032	CR2450 (some 2011 to 2017 keyless fobs)	Flip key: lever at the slot behind the blade. Keyless fob: remove the blade, pry the end cap
MINI	CR2032	—	Same as BMW: blade out, lever at the base
Subaru	CR2032 (smart key)	CR1620 (older flip key)	Remove the blade, lever at the slot
Jeep, Alfa Romeo, Fiat, Maserati	CR2032	CR2450 (some older Jeep fobs)	Remove the blade, lever the halves apart at the seam
Peugeot, Citroën	CR2032	CR1620 (older flip key)	Flip key: remove the screw on the back if there is one, then open at the seam
Kia, Hyundai	CR2032	—	Remove the blade, lever the halves apart at the slot
Lamborghini, Bentley	CR2032	—	Audi-style: remove the blade, slide or lever the back cover

Buy a known brand. Panasonic, Varta, Energizer, Duracell and Maxell cells all last about the same; the no-name ten-packs often arrive half-discharged and you will be doing this again in a year. A CR2032 should cost between one and three euros.

How to change the battery, step by step

1. Take a photo of the key before you open it. You will want to remember which way the battery faced.
2. Release the emergency blade. Almost every key has a small sliding button or catch. Hold it in and pull the metal blade out.
3. Find the opening point. Look for a thin slot where the blade sat, or a notch along the seam between the two halves. That is where the key is designed to be opened.
4. Lever gently. Push the tip of the blade into the slot and twist. The cover should lift. If it does not move, stop and look for a second catch; forcing it breaks the clips.
5. Note the battery orientation. The side with the text is the positive side. In nearly every key it faces up, towards the cover, but check before you lift it.
6. Lift the old battery out with a plastic pick or a fingernail. Avoid metal tweezers across the contacts.
7. Fit the new one the same way round. Touch it by the edges only; grease from fingers on the contacts is the most common reason a fresh battery "doesn't work".
8. Snap the key shut, slide the blade back in, and test it at the car.

Do you need to reprogram the key afterwards?

No. The key's pairing with the car is stored in a chip, not in the battery. You can leave the key open for an hour and it will still work when you close it. The only thing you might notice is that the first press after a battery change takes a second longer while the key wakes up.

The one exception is a key that has sat completely dead for many months. A few older systems need the key presented to the ignition or start button once to re-sync. That is a ten-second job, not a trip to the dealer.

The key is dead and you need to drive now

Every keyless car has a fallback for exactly this situation, and it is in the owner's manual under "emergency start" or "key battery discharged". The pattern is the same across brands:

• Open the door with the emergency blade. The lock is usually hidden under a small cap on the driver's door handle. Lever the cap off with the blade, unlock, and expect the alarm to sound until you start the car.
• Start the car by holding the key to a marked spot. BMW, MINI and Mercedes: hold the key against the steering column or the start button. Audi, VW, Škoda, Porsche: hold it against the start button or the marked area on the steering column. Volvo: put the key in the cup holder reader. Toyota, Lexus, Honda, Mazda: touch the key's logo to the start button, then press. Tesla: hold the fob or card against the console reader.

The car reads the chip in the key by induction, which needs no battery at all. It works every time; it is just inconvenient.

Changed the battery and it still doesn't work?

• Battery in upside down. The most common cause. Open it again and flip it.
• Contact not touching. On older keys the spring contact can flatten. Lift it a fraction with a pick.
• Wrong size. A CR2025 is thinner than a CR2032 and will rattle without making contact. The last two digits are the thickness in tenths of a millimetre.
• Dead on arrival. It happens, especially with bulk packs. Try a second cell before assuming the key is broken.
• Damaged key. If the key has been through the washing machine or dropped on tile one time too many, the circuit board may have cracked. A locksmith can test it in seconds.

Make the next battery last longer

Two things drain a key battery faster than age: heat and constant transmitting. Keys left on a dashboard in summer die early. Keys kept near the car at home keep talking to it; store them a few metres away or in a signal-blocking pouch and the battery will last noticeably longer. The pouch also stops relay theft, which we cover in Do car key covers stop relay theft?.

And while the key is open on the table, look at the plastic. If it is scratched, worn shiny or the buttons are cracking, that is what a key cover is for. An Alcantara or leather cover slides off in a second for the next battery change, and a replacement key from a dealer costs two to four hundred euros, which makes a thirty-euro cover a reasonable precaution.

Brand guides

Step-by-step guides with photos of each key type:

Common questions