This video shows how you can replace the batteries in your Mercedes C300 Key. This key / key remote uses one 3V CR2025 battery. Please check the type of a battery that your key uses. I replaced them with the same CR2025 type made by Energizer. You can also use other major brands such as Duracell.
Note: There are a few variations of Mercedes keys / SmartKeys and the methods you use to replace the batteries. This video shows the key where the plastic cover opens from the back of the key. Make sure your key uses the same design before using this method.
Keywords: Smart Key, SmartKey, keyfob, Key, Key Remote, Remote, Battery Replacement, C300 Mercedes 2015