Below are the steps to replace the battery of your BMW remote:
When replacing the battery of your BMW remote, you will need to remove the metal blade key from the fob first. Its metal key can be used as a pry tool to open the key fob. The battery is located under the back cover. Remove the battery cover and simply lift the battery out of place to remove it. Install the new battery then close the remote and snap the cover back together
Some remotes are called non-comfort access version which has a built-in rechargeable battery. Remove the valet key from the BMW key fob. This is the metal key blade that can be used in case of emergency to open your car door or trunk. To remove the valet key, you will need to press the small tab in the keyfob then pull the valet key.
After you remove the valet key you will notice a small access port on the keyfob. Use the valet key or the flat screwdriver to remove the key battery cover.
Once you remove the battery cover, you will see the battery. Remove the dead battery and install the new one. Press the battery cover on the key with your fingers. Reinsert the valet key.
BMW key that has the side indent has a rechargeable battery. It wasn’t designed to be serviced that’s why you can’t easily open the case.
The battery gets charged when it is inserted in the ignition. If you are only taking short trips, you are not allowing enough time for the key to charge.
Take at least a two hour or longer trip to recharge this BMW key. If the battery has completely died, you can open the case but it will require cutting the plastic part of the key.
You can then replace the built-in battery with a new rechargeable CR2032 battery. The other option is to purchase a new key from your dealer which typically ranges between $180-$290.