I remember reading somewhere that LiPO do best stored partially charged. As for the other technologies, the big danger with not charging them before use is (especially in higher current applications) is if they are in series and one is very low while another is fully charged, you run the risk of reverse charging the very low one which is bad for the cell. Better to start with them all in the same state (and use ones with the same mah capacity). Batteries can do bad things when abused - I just saw on the news that Samsung has halted their Note 7 after several of the replacements for the ones with battery fires also had battery problems on an airplane which really gets people excited !! :o