One of my keys failed (would not charge). Couldn't find a way to get at the battery (the back plate seems to be just for show). $276 for a new one.

Whilst I was waiting at the service desk - One of the employees casually told me that they get about 20 a day. I replied that it's a nice little earner. He replied that they were built to fail. I sincerely doubt that that is the case, but it strikes me that it is a bit of a design flaw that entails the purchase of an entirely new key for what is most probably a duff battery.
2001 Silver/Red