How to Change a Mercedes Key Fob Battery

1. Remove the mechanical key from the Smart Key by sliding the button on the end of the Smart Key and pulling the mechanical key straight out.
2. Insert the mechanical key into the opening on the end of the Smart Key and push it in until the cover on the back of the key opens. Remove the cover to expose the battery tray.
3. Tap the Smart Key against your palm until the battery falls out. Use a lint-free cloth to insert the new battery, with the positive side facing up.
4. Reinstall the battery cover by inserting the plastic tabs, then pushing the cover closed. Test the buttons to make sure the new battery works.