BMW has in the past had two variations of the same key fob remote type; keys with “comfort access” features, and those “non-comfort access” keys. Comfort Access is a feature on BMW vehicles that allow you to unlock your vehicle just by touching the door handle, you can keep your key fob in your pocket. The vehicle senses the key once it is 5 or so feet away, and allows you to unlock or start the car while keeping your key fob remote stashed away in a backpack, or your pocket. For all BMW key models see the all BMW Key Fob Batteries page.
Now, changing the battery on a non-comfort access key is very different then a key fob remote WITH comfort access enabled. The main difference is that comfort access key fobs have replaceable non-rechargeable batteries that are relatively easy to pop in and out of the key fob. Non-comfort access keys requiring prying apart the key fob, and de-soldering a rechargeable VL2020 battery from the circuit board.
Here’s a video I made showing the difference between two variations of popular BMW keys with and without Comfort Access and how to change the battery in each:
Non-Comfort Access Remote Key Battery: VL2020
Comfort Access Remote Key Battery: CR2032