I purchased the LightCharge USB charger and an external battery pack. I connected the charger to the dynamo hub and hooked up the battery and took off pedaling and everything worked perfectly. I rode for about half an hour and I could see the charging bars went from two lights to three at the end of my ride. Today I am going to go out for a longer ride and charge it up all the way to five bars. Now I am trying to think of things other than just my cell phone that I can charge off the battery when I am out touring- eg a USB camp lantern. Really cool.