I've seen contradictory reports about how much a Li-Ion battery can be safely discharged, but 3V per cell seems to come up most often.
I tested a Panasonic video camera, and it shuts off at 3.15V. Are they just being conservative?
The problem I have is that I'm shutting off a circuit at 6.3V (2 cell) that's run from a generic Sony video camera battery and only getting half it's rated capacity.
Although I don't expect the full capacity from an after-market battery, these batteries come from WES Components, not eBay, so I wouldn't expect them completely fake, so I'm guessing that I'm cutting off too soon.