Figured out how to repurpose the cells and part of their holder. Found a load balancing charge controller, and I’m going down to 3 cells, that should work out to 11.1 to 12.6 volts. Turns out 4 cells could have gone as high as 16.8V at full charge.
Nice thing about researching how to do this, is I’ve learned how to make my own battery packs to any reasonable scale. Good for many other future uses.
Thanks for the link! Will have to look at SMAKN next time. Got a feeling I’ll be using this again.