Talk to the folks at Peter White Cycles. That is where I got my SON 28, and tail light as well. Now here's the thing with charging that I found out on tour last year. Start out every morning with a full charge. Plug in while you are riding to keep the charge up- if you are using a cycling app for instance, I have a WaHoo RFLKT and used the Cyclemeter app. If you are riding a lot in the mountains, you will not be charging up hill, as you will be pedalling too slow. You must be going at least 12 mph to charge, and maintaining that speed or better for long periods of time. When you are going downhill, the dynamo will charge up the cache battery first, then switch over to charge your device. By that time, you may be on your way up the next hill, and not charging again. On the flats, it worked very well, and it also did well in rolling hills that were short ups and downs. The other issue I had, was I was always plugged in. If you are intending on using your phone as your primary camera, you will be constantly be plugging in and unplugging, and after a week of that 20-30 times a day it gets annoying. But that will depend on how many pictures you take or even if you use your phone as a camera. I also took a full size DSLR, but uploading pictures took forever, if it got done at all. So carrying a couple cards took care of that problem.