I don't know what kind 16650 you use but if they can power up 20W bulb with first click, then no problem. Keeppower works fine.I have this one G4 Xenon Bi-Pin Socket from tad. Will that work? But using 2X16650's I don't want a 6V bulb do I?
Using 2X16650's you want a 6V bulb to overdrive it by 7.2V for brighter and whiter beam.