Keyless entry is growing increasingly common among more prestigious cars. Changing the battery in keyless entry devices is important in preventing being locked out of the car. When the battery light begins to flash, it is a simple process to replace the battery. Most modern BMWs use the CR2032 battery, so you must have one of these on hand in order to replace the old one. However, once you have bought one, you don't need specialised equipment to complete the procedure.
Place the keyless entry fob on a flat surface facing away from you. Press the button to release and remove the spare key.
Press the spare key into the small indentation inside the keyless entry fob. This will remove the cover and allow the battery to be exposed.
Remove the old battery and replace it with the new one. Ensure that the new battery is correctly situated by looking at the old one before you remove it and replace it with the new one.
Click the key fob cover into place and ensure that it is properly sealed. If the battery does not work, check to make sure it is right side up.