How to change battery in BMW key fob

Most BMW key fobs use a replaceable coin-cell battery, commonly a CR2032 or CR2450. Always check the number printed on the old battery before buying a replacement.

How to change battery in BMW key fob: Replacement steps

1. Remove the mechanical key
   Find the small release button on the back or side of the key fob. Press and hold it while pulling out the metal key.
2. Locate the opening slot
   After removing the mechanical key, look inside the empty key slot or along the edge of the rear cover. You should see a small notch.
3. Open the battery cover
   Insert the tip of the mechanical key into the notch and twist gently. The rear cover should begin to separate. Avoid using excessive force, as the plastic clips can break.
4. Remove the old battery
   Lift the battery out carefully. Before removing it completely, note:
   • The battery model number
   • Which side faces upward
   • The position of the positive “+” symbol
5. Install the new battery
   Insert the replacement in exactly the same orientation. On many BMW keys, the positive side faces upward, but this varies—follow the markings inside the fob.
6. Close the key fob
   Align the rear cover and press around its edges until all clips snap securely into place.
7. Reinsert the mechanical key
   Slide it back into the fob until you hear or feel it click.
8. Test the key
   Stand near the vehicle and test the lock, unlock, trunk, and panic buttons. The key normally does not need to be reprogrammed after a simple battery replacement.

If the key still doesn’t work

• Confirm that the battery is installed in the correct direction.
• Make sure you removed any protective film from the new battery.
• Clean the battery contacts gently with a dry cloth.
• Try another fresh battery from a reliable brand.
• Check that the cover is fully closed.
• If only Comfort Access fails, try locking and unlocking the car with the buttons first.

Important exceptions

Some older BMW “diamond-shaped” keys contain a sealed rechargeable battery that charges while the key is in the ignition. These are not designed for a simple coin-battery replacement and may require soldering or professional repair.