Hello everyone. I've been charging my N900 from solar for the past year or two using various methods. I am currently doing final testing of my proto USB solar charger Maximum Power Point direct regulator which charges to a maximum of 800mA from a 5w solar panel (ie %80 efficient into the battery). Before I tried this I direct charged my batteries in an adapted external charger. A home-built external charger can be easily modified to run off a bicycle dynamo (as opposed to off a solar charger) with the addition of a low-dropout full-bridge rectifier and some decent capacitance.