Make sure you get good LiIon's with a nice button on top, or a magnetic spacer... I've tried my Kroma/s 2 times now with a 17670 and not gotten it to light up... today when I tried it (after reading this post and checking out the leef tube, which I like BTW, might need one myself) I pulled the head off and did some testing with a meter as the connection for the back end..
17670 definitely will light the kroma up, no problem, pulls just under 1A, however the cell I have, for some reason will not light up when assembled, I think it's because of the alignment and the fact the cell doesn't have much of a button top to it... the spare 18650 I have laying around is even worse yet.
So I'd highly recommend trying to find a cell with a good buton top to it, or picking up one of the magnetic spacers to help it out...
This is just what I've figured out on my own... I would like to run at least one of my Kroma's off rechargeable, but had been unsuccessful up until now, I'll probably get a spacer and new 17670 since the one I had is already in use in my E2W