My RB800C seems to have
I struggled to work out what was going on with mine (I had the same problem) and concluded that it was either an issue with the electronics, which was beyond my skills to fix, or something much simpler. We all tend to assume the more complicated answer, so I focused on the very thin and nasty spring inside the battery housing cap. I wondered if that spring was deforming in some way and causing a short circuit. So a couple of months ago I unscrewed the two tiny retaining screws that hold the plate on which the spring sits, took the plate out, removed the spring, and replaced it with a much thicker, gold plated spring taken from a small flashlight I no longer had a use for. I soldered the spring into location on the plate, returned the plate to the battery housing cap, and inserted a new battery. Two months later, the battery is still showing full power.
