That Crazy Guy on a Bike review said 15 watts if you go fast enough.
This link:
http://www.ctc.org.uk/file/public/feature-hub-dynamos.pdfhas a graph on page 3 with output against speed for several different hubs. Even at 50 km/hour, none of the tested hubs beat 5 watts. So, I don't think 15 watts is going to happen any time soon. And at the speeds that I ride, that certainly is not going to happen ever. That makes me question the soundness of the review.
I discussed my search for a USB charger and my final decision on what to buy at this link:
http://thorncyclesforum.co.uk/index.php?topic=11153.msg81461#msg81461And my opinion has not changed, I am still happy with the Luxx 70 Plus. But if I was going to buy a dedicated USB charger without headlight, I would have bought the Sinewave Revolution. I have no idea if the Revolution has greater current capacity than what I have, but it has outstanding waterproofing and good overvoltage protection. And I do not want to mount it on the stem cap, so that rules out some options.
Additional information since I wrote that review:
1. I have picked up a couple cheap small Li Ion storage batteries that I found I can plug a USB charging cable into and simultaneously plug in another USB cable to draw power out of them. That acts like a cache battery and smooths out the power fluctuations in addition to maintaining charging to whatever I want charged when I stop for stop lights, etc. And it would be nice to have a couple of those cheap storage batteries charged up when I am not moving in the campsite. That is the only change since I wrote that review of the Luxx headlight.
2. I have commented before that I use a batter powered taillight, thus did not buy a dyno powered taillight. I checked the power at the taillight connectors on the Luxx and it only sends power to a taillight when the headlight is on. Thus, if I wanted to use a dyno powered taillight while using the USB charger, it would not work. I learned this after I wrote the review.
