Yep power-cranks. I use the lighting setup like this because of run-time in cold weather. I only run one at a time. I started with the NR Digital Evolution and tail-light with the planet-bike 3-LED blinky as a backup. The NR on 10W setting with the taillight usually got me about 1/2 mile from home before fizzling out (1.5 hrs) so I started looking for alternatives (spare battery, etc. etc.). Then my NR crapped out on me altogether and I had only the planet-bike light which doesn't cut it on a rural road with no streetlights on a dark misty night. NR took forever to respond to me, so I got the cygolite so I could keep riding. The cygolite has had no trouble keeping the candles lit for up to 2 hrs in 10-20F temps. When the NR finally returned, I just slapped it on there for when its raining/misty/foggy/snowy and I need extra illumination or for if/when the cygolite runs out of juice. In the rain a few days ago I was running both of them (NR on 10W) and my wife said she could see me from about a mile away. Not bad for a dark rainy night. I don't worry about not being seen. If I'd gotten the cygolite first I wouln't have gotten the NR.