I ride day or night and my lights are always on. The dyno runs head and taillights that are very bright. I use an AxA pico30 and a spaninga taillight with the stand light feature. I now have this setup on both my bikes and will never go back to batteries. My dyno is a cheap Sanyo and I can't feel any undo drag at all. Its orders of magnitude better than a bottle in that regard. I put about 3000 miles on my bikes this year and almost all of those miles were with the Sanyo h27.