I would imagine the battery is under the bed, but how you would remove this I can't say as I don't have one to take a look at it. If you really do want to change the battery I would buy an old battered and or faded one just to take it apart to see if it's possible to do.
I think also that it is under the bed but very difficult to access even after severals trials. As I am not sure, I am afraid to broke it as the one I have is in a really good conditions and complete. ... more