Mercedes-Benz A-Class key fob battery
1 of the 4 model years listed for the Mercedes-Benz A-Class have a proven battery. The most common answer is CR2032. Rows below run oldest to newest; a year can appear twice when the car came with more than one kind of key.
- 2019-2020Smart key
Not confirmed yet
- 2021Smart key
CR2032
Owner's manual: manualslib.com (checked Nov 1, 2026)
Manual text: “You require a CR 2032 3 V cell battery.”
Find CR2032 on Amazon - 2022Smart key
Not confirmed yet
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.
- Use the slot where the metal key sat. Twist, do not lever hard, and work along the seam until the halves separate.
- Pop the old battery out with a toothpick or plastic pick, not a metal blade, and seat the new one with the + side matching the old one.
- Snap the halves back together, slide the metal key home, and press each button, then try the start button from the driver's seat.
On the common chrome Mercedes key, a slide at the back frees the mechanical key, and pushing that key into the opening releases the battery tray.
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.
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.