This is a triple D-cell battery box in a triangular arrangement designed to fit within a round/hexagonal enclosure.

Originally intended to replace the battery holder in an old LED camping lantern, the D-cell battery holders could easily be used individually or for any purpose that accepts a battery holder with a diameter of ~80mm. Each D-cell battery holder is printed separately (for strength and ease of printing), and then riveted together using 1.75mm filament (you could use CA glue instead, if you prefer).

The battery contacts are 16mm x 16mm 18650/C/D type contacts from Amazon.

Assembly Instructions:

1. Print 3x D-cell holders and 6x connectors
2. Insert the battery contacts into each D-cell holder in the desired configuration and solder wires appropriately. How you do this depends on whether you want the batteries wired in series or parallel.
3.  Position the D-cell battery holders in a triangle (side-to-side) and slide the connectors over the top and bottom wings.
4. Slide a short piece of filament through each hole (2 per connector) and melt each end (I used a soldering iron) to lock the connectors in place.
5. slide more short pieces of filament through the adjoining holes in each D-cell battery holder (6 per holder) and melt both ends to lock them together.