The smart key remote intelligence (lock/unlock) infrared and rf is battery powered. The engine start and unlock is powered by inductive energy (from the key collar) in the car. The circuit board slides out of the housing after releasing the small catch in the metal key slot. It slides out similar to a match box.
As everyone knows the smart key can not be reprogrammed but if you have a slightly damaged housing you can swap your circuit board into one of those E-Bay remotes and throw the rest away.MB has warned about having too much weight, keys and junk putting a strain on the catch. Of course you dont know what you get with an E-Bay remote. The new one ,chrome, is much nicer and under $200