Open the key fob without damaging it
Most Audi key fobs split into two halves along a seam that runs around the edge. Look for a small slot or notch on one side — this is where you insert a flat tool to pry the halves apart. A flathead screwdriver, a coin, or a plastic spoon works well. Do not use a sharp knife, which can slip and cut your hand or gouge the plastic.
Insert your tool gently into the slot and twist slightly to create a gap. Once you see daylight between the halves, work your way around the edge, lifting a little at each point rather than forcing one spot. The two halves will separate to reveal the battery compartment and the circuit board inside.
Key Takeaways
- Audi key fobs use a CR2032 battery, a coin-shaped cell about the size of a dime that costs between $3 and $8.
- The battery sits in a metal holder on the circuit board and slides out sideways — do not pry it straight up, which can damage the holder.
- When reassembling, align the two halves so the seam is even all the way around, then press firmly until you hear or feel a click.
- If your key fob still does not work after a new battery, the problem is usually a worn circuit board contact or water damage, not the battery itself.
Remove the old battery and note its position
The battery sits in a metal cradle on the circuit board. It is a flat, round cell about the size of a dime, stamped with "CR2032" or a similar code. The positive side (marked with a + symbol) faces up toward you.
Slide the battery sideways out of its holder — do not pry it straight up. If it is stuck, use a plastic tool or your fingernail to nudge it gently from the side. Metal tools can scratch the circuit board or short the battery. Once the old battery is out, set it aside. Do not throw it in the trash; most pharmacies and electronics stores take used batteries for recycling.
Install the new CR2032 battery
Buy a CR2032 replacement battery from a pharmacy, grocery store, hardware store, or online retailer. They are inexpensive and widely stocked. Check the expiration date on the package — an old battery may have lost charge already.
Slide the new battery into the metal holder with the positive side (+ symbol) facing up, the same way the old one sat. It should fit snugly and lie flat. If it does not slide in smoothly, double-check that the positive side is facing up and that you are not trying to force it in backward. Once it is seated, the battery should not move when you gently shake the fob.
Reassemble the key fob halves
Line up the two plastic halves so the seam is even all the way around. Start at one end and press the halves together firmly, working your way along the seam. You should feel or hear a small click when the two halves snap into place. If they do not click, the seam is probably misaligned — separate them and try again.
Once assembled, test the fob by pressing each button. The lock and unlock buttons should work when ready. If nothing happens, open the fob again and check that the battery is seated properly in its holder and that the positive side is facing up.
Test all buttons and troubleshoot if needed
Press the lock button, the unlock button, and any other buttons on your fob. You should see the car respond — lights flashing, doors locking or unlocking, or a chirp from the horn. If one button works but others do not, the problem is usually a worn contact on the circuit board, not the battery.
If no buttons work, open the fob again and look at the circuit board. If you see white or green corrosion around the battery holder or on the metal contacts, the fob has water damage. Dry the inside thoroughly with a soft cloth and let it sit open in a warm, dry place for a few hours. Then reinstall the battery and test again. If the fob still does not work after drying, the circuit board may need replacement.
When to replace the whole fob instead
A new battery fixes most key fob problems, but not all. If your fob has been dropped in water, sat in a hot car for months, or is several years old, the circuit board contacts may be worn or corroded beyond cleaning. In that case, a new battery will not help.
Replacement key fobs for Audi vehicles vary in price depending on the model year and whether you buy from a dealer or a third-party seller. A dealer fob typically costs more but comes programmed to your car. Third-party fobs are cheaper but require programming at a dealer or by a locksmith. If your current fob is not working after a battery change and drying, contact your Audi dealer or a local locksmith for a replacement and programming.
Frequently Asked Questions
What battery does an Audi key fob use?
Audi key fobs use a CR2032 battery, a coin-shaped lithium cell. It is the same battery used in many watches, calculators, and small electronics. You can find it at any pharmacy, grocery store, or hardware store for a few dollars.
How long does a key fob battery last?
A CR2032 battery in an Audi key fob typically lasts two to four years, depending on how often you use the fob. Heavy use drains it faster. If your fob stops working suddenly, the battery is the most likely cause.
Can I damage the fob by opening it myself?
Opening the fob is safe if you use a plastic or soft tool and work slowly. The main risk is cracking the plastic if you force the halves apart too hard. Use gentle pressure and work your way around the seam rather than prying hard at one spot.
Why does my key fob still not work after I put in a new battery?
If a new battery does not fix the problem, the circuit board contacts are likely worn or corroded. This happens with age or water exposure. Try drying the fob thoroughly and cleaning the battery contacts with a dry cloth. If that does not work, the fob needs replacement.
Do I need to reprogram my key fob after changing the battery?
No. Changing the battery does not erase the fob's programming. Once you install the new battery and reassemble the fob, it should work when ready without any reprogramming.