I have a Mag 1D P7 that I bought from Britelumens (Jo) with the d2flex and I asked him the same question. I believe he said like 50 minutes on a 18650. I'll have to see if I still have the e-mail from him. Yesterday I charged my KD D Li ion and I ran my Mag P7 for about an hour and 10 minutes before turning it off. I really didn't see much difference in brightness from when I first turned it on till I turned it off. The light got warm, and thats it. It wasn't hot. I might try it again to see how long it will go before it gets dim.