How do you replace key battery on Mercedes c class?

To replace the key battery on a Mercedes C-Class, first, locate the small notch or groove on the key fob. Use a small flathead screwdriver or a similar tool to gently pry open the key fob, separating the two halves. Remove the old battery, noting its orientation, and insert a new battery of the same type (commonly CR2025 or CR2032, depending on the model). Finally, snap the fob halves back together and test the key to ensure it functions properly.