BMW 4 Series key fob battery
2 of the 12 model years listed for the BMW 4 Series have a proven battery. The most common answer is CR2450. Rows below run oldest to newest; a year can appear twice when the car came with more than one kind of key.
- 2014-2017Smart key
Not confirmed yet
- 2018Smart key
CR2450
Owner's manual: manua.ls (checked Nov 1, 2026)
Manual text: “Insert a type CR 2450 battery with the positive side facing up.”
Find CR2450 on Amazon - 2019-2020Smart key
Not confirmed yet
- 2021-2024Smart key
Not confirmed yet
- 2025Smart key
CR2032
Owner's manual: manua.ls (checked Nov 1, 2026)
Manual text: “Insert a CR2032 3V battery with the positive side facing up.”
Find CR2032 on Amazon
Changing the battery
Smart key (push-button start)
- Find the small release on the edge or back of the fob and hold it while you pull out the metal emergency key.
- Look inside the empty key slot for a notch. Put the tip of the metal key or a small flat screwdriver wrapped in tape there and twist gently until the shell splits.
- Note which side of the old coin cell faces up (usually the side with the writing), lift it out with a plastic tool, and press the new one in the same way.
- Close the case until it clicks all the way round, put the metal key back, then try the buttons and a push-button start.
A CR2032 is 20 mm across and 3.2 mm thick. CR2032, CR2025 and CR2016 share the same width but not the same thickness, so a swap between them can leave a loose contact or a case that will not close.
A CR2450 is 24.5 mm across and 5.0 mm thick, much fatter than a CR2032. A thinner cell will rattle and lose contact, so buy the exact size.
Keep spare coin cells away from small children. A swallowed coin cell can burn the throat within hours; if it happens, go to an emergency room at once.