With that as a guide, he designed and 3D printed a case for it made up of four printed parts. The case was needed because the 18650 doesn’t fit in the NDS Lite’s battery compartment.

The core of the battery is just five 18650 cells in a 3D-printed holder with a BMS, but the real magic is in the external components. The outer body is a brass tube with the logo etched through ...