How to Replace Key Fob Battery in a BMW 3 Series

Say goodbye to unreliable keyless entry with our foolproof guide on key fob battery replacement. We’ve simplified the steps so you can enjoy the benefits of a fully operational key fob without the hassle. Try these instructions out on your BMW 3 Series. 

2011 – 2023 Models

1. Flip the key fob over and locate the release button or area on the backside. Press the button to remove the internal key from the fob.
2. On the side where the key was removed, you’ll find a small hole. Insert a flat-head screwdriver into the hole and gently pry the backing off.
3. Once the backing is off, you’ll see the battery. Use a flat-head screwdriver to carefully pop out the old battery.
4. Purchase a new CR 2450 battery. You can easily find these batteries online, for example, on Amazon.
5. Place the new battery into the battery compartment with the correct orientation.
6. After inserting the new battery, carefully put the backing of the key fob back into place. Align it correctly and gently press until it snaps back into position.
7. Before using the key fob, test it to make sure the new battery is working correctly.

1998 – 2005 Models

1. On the edge of the key fob, you will notice a line that separates it into two halves.
2. Using a sharp knife, carefully score and cut through the plastic all the way around the key. Take your time to avoid damage.
3. Start cutting from the top of the key, ensuring a clean separation of the two halves.
4. Once the key fob is separated, you will see the circuit board inside.
5. Remove the circuit board by tapping it out or using small tweezers.
6. Locate the rechargeable VL2020 battery on the circuit board; it is connected to the board through two soldered legs.
7. Use a soldering iron and a soldering vacuum to desolder the old battery’s legs. Melt the solder and remove it to free the battery.
8. Acquire a new VL2020 rechargeable battery with legs offset at 90 degrees.
9. Double-check that the new battery’s legs align with the soldering points on the circuit board.
10. Place the new battery onto the circuit board, ensuring its legs fit into the soldering points.
11. If needed, clear off any excess solder to create space for proper attachment.
12. Use the soldering iron to attach the new battery securely to the circuit board.
13. Melt solder onto the soldering points and the battery’s legs, ensuring a strong connection.
14. Carefully place the circuit board back into its original position within one of the key fob halves.
15. The buttons on the circuit board should align with the corresponding buttons on the key fob half.
16. Apply a small amount of superglue around the edges of the key fob half that houses the circuit board.
17. Realign the two halves of the key fob and press them together firmly, allowing the superglue to bond them.
18. Make sure the key fob is securely sealed and there are no gaps.

Test the key fob by pressing the buttons.