how do i change the battery in the key remote

How to Replace a Battery on the Fob of a Mercedes E-320 The E320 requires a lithium CR 2025 battery, available most places where batteries are sold. How to Open a Key Fob How to Replace the Car Key Battery in a Mercedes Benz New battery Place the key fob on a table with the locking tab facing up. Push the locking tab to the left. Pull the metal mechanical key out of the fob housing. Push the metal key into the hole to the left of the locking tab and slide it to the right to unlock the battery compartment. Pull the battery compartment out of the fob. Remove the two batteries from the compartment from under the contact springs. Push the new batteries under the two springs with the positive sign facing up. Hold the new batteries with a clean, lint-free cloth. Press the battery compartment back into the fob housing. It will click into place. Reverse steps 2 through 4 to reassemble the key fob.