Originally posted by: TheLonelyPhoenix
I believe either NiMH or NiCad batteries (or both, don't remember exactly) weren't supposed to be left charged for long periods of time. Part of recommended maintenance was a battery "exerciser" that totally discharged and recharged the battery during a long period of low usage.
You can get away with a lot using lithium ion batteries though, so I wouldn't worry about it if that's what you have.