I just ordered one of these. I already own an AXA Luxx light with a USB port as discussed above. The price of the biologic was so cheap I could not resist. My experience with these chargers is somewhat lukewarm. I try to charge external batteries but with mixed results. In any event the charge out of a dynamo hub isn't much and it takes a long time to top off a battery. I am always on the look out for something better but I am unwilling to pay some of the high prices for these devices.