Before I made my good DIY solar charger, I just had this simple charger. So I made this crank backup to survive times when there wasn’t enough sun for the simple charger.

I had this old hand crank flashlight lying around. The flashlight has an outlet with an odd jack that seems to cut off at 5.8V. With the right connector I could connect that to USB (I bet the device came with some adapters). The motor voltage seems to go up to around 20V. So that sounds like a great solution for charging a lead acid battery. Internally it has a 3.2V lithium rechargeable battery. I’m supposing that is to keep the light going when you’re not cranking.

I took it apart and un-soldered one of the motor leads to disconnect it from the flashlight. I then added some leads to the motor and made an exit for them. I connected a diode (negative facing the positive battery terminal).

It seems to work. I may try and use the USB out on it as well. Then it could charge the phone directly.