BMW automobiles with the Comfort Access option (allows you to open the car and start it without having to pull the key out of your pocket) has an internal battery (battery # 2032) that needs to be replaced on occasion.

Below is a picture of a BMW Comfort Access Key next a normal key.

****************************

The BMW Comfort Access Key has a small battery door that is easily pulled open with your finger nail or small flat head screw driver.

You must first remove the internal fixed key first (see picture below) and then pull the batter door open and replace the 2032 battery.

It is also recommended to use the BMW Comfort Access Key in the ignition periodically to that the internal non-replaceable battery can be charged.