Fenix BT20 running on 3400Ah Panasonic 18650 batteries run around 24+ hours, 8,75 hours, and 5.5 hours on 100, 300, and 450 lumen settings. The 300 lumen setting is much brighter with more throw than any dynamo setup with the one considerable drawback that one needs to make a battery change on very rides. I carry a spare pack with batteries already in it or sometimes I mount redundant lighting systems. I had thought my parsimonious lighting choice would be a disadvantage on 1200k randonnees but I have had no real problems with batteries on such rides. Obviously a generator is convenient but I prefer the extra brightness and portability of battery powered lights accepting the slight inconvenience of changing batteries.