Mercedes-Benz SLK key fob battery
5 of the 19 model years listed for the Mercedes-Benz SLK have a proven battery. The most common answer is CR2025. Rows below run oldest to newest; a year can appear twice when the car came with more than one kind of key.
- 1998-2008Unknown
Not confirmed yet
- 2009Smart key
2 x CR2025
Owner's manual: manualslib.com (checked Nov 2, 2026)
Manual text: “always replace both batteries ... Lithium, type CR 2025”
Find CR2025 on Amazon - 2010Smart key
2 x CR2025
Owner's manual: manualslib.com (checked Nov 2, 2026)
Manual text: “always replace both batteries ... Lithium, type CR 2025”
Find CR2025 on Amazon - 2011Smart key
Not confirmed yet
- 2012-2013Unknown
Not confirmed yet
- 2014Smart key
CR2025
Owner's manual: manualslib.com (checked Nov 1, 2026)
Manual text: “You require a CR 2025 3 V cell battery.”
Find CR2025 on Amazon - 2015Smart key
CR2025
Owner's manual: manualslib.com (checked Nov 1, 2026)
Manual text: “You require a CR 2025 3 V cell battery.”
Find CR2025 on Amazon - 2016Smart key
CR2025
Owner's manual: manualslib.com (checked Nov 1, 2026)
Manual text: “You require a CR 2025 3 V cell battery.”
Find CR2025 on Amazon
Changing the battery
Smart key (push-button start)
- Start by freeing the hidden metal key: there is a latch or slide on the case, and the blade comes out once it moves.
- The gap left by the metal key usually has a pry point. A slow twist with a thin flat tool (tape on the tip saves the plastic) opens the two halves.
- 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.
- Reassemble, refit the emergency key, and check that the car sees the fob when you press start.
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.
This key takes two CR2025 cells. Change both at the same time and stack them the way the old pair sat; mixing a fresh cell with a tired one shortens the life of the new one.
A CR2025 is 20 mm across and 2.5 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.