This print combines one of the cheap Powerbank modules with a single 18650 cell.
The modules are readily available on eBay and the likes when searching for “Powerbank module" for like 1…2 Euros.
It's just two wires soldered to the module; one is wrapped around an internal bridge for the positive side, the negative goes along the battery through the tube and is pressed against the negative side by the screw-on cap.
The module is glued into the cover from the back, can be pushed in and is hold on place with two screws M3x8 …16, which taps directly into the plastics.
Prints without supports, I used a brim for the main body.
The author marked this model as their own original creation.