The SC5 and SC53 series, yes nimh only though I stuck a 14500 in the SC53c before based on threads here saying it would be fine, just to test it out. The SC52 series get some 14500s when I feel like running them. I'm happy to have the programming. That way I can have 1 click medium instead of high. For my uses nimh is plenty sufficient.Are you all running these lights on nimh batteries only?