For some time now, I've wanted a way to run my Baofeng on batteries that could be recharged in the field, off of a solar panel or other USB device. Since I use an 18650 battery charger as a power bank and run my headlamp on an 18650, this seemed like the best cell to use.

Two small squares of brass with nubs of solder on them form the primary contacts between the cells and the radio. The brass I used was cut from a strip 13mm wide by 0.5mm thick.

Two ends of a small spring I purchased from the local hardware store (~6.5mm⌀) keep the batteries held fast. They're connected by a diode to prevent reverse polarity from frying your radio.

This is a major work in progress. Though it's functional, it's not very refined. The springs are a bit tricky to solder since they need to be soldered in place with the current design--not optimal. The brass plates also don't make contact with the radio without blobs of solder. I'll most likely update it at some point.

EDIT: Added + and - polarity indicators for each cell, to add redundancy or obviate the diode. I also Cut away some of the central septum to allow the bottom springs to be installed a fair bit more easily.

I'm having a hard time coming up with ways to simplify the post-print build without sacrificing structural integrity. I'll let you guys know if I come up with anything.