****WARNING! You could easily GRINDWEAR DOWN the PRIMARY or SECONDARY drive gear, rendering the dynamo unit USELESS unless you have spare gears! Keep this in mind!!**** br br It's probably not good for the radio's circuitry, or batteries. The "pop" you heard was from a capacitor, later discovered, and the unit still functions normally without it. br br The radio was modified to charge any AA or AAA sized batteries inside it's own compartment, using the original wires from the battery pack inside of it.