I agree with you, don't try this at home. I'm not an electrical engineer, I just build stuff. I can tell you from my own personal experience that a SON Dynohub connected to a bridge rectifier and 4 AA nimh batteries will not regulate the voltage to 5.2 volts. When the batteries are fully discharged, the voltage from the hub is limited to 8 volts, too much for a usb device. As an added bonus, the batteries will overheat when charged at this rate.