battpack-scad

Snap-together battery holders for cylindrical cells, designed in OpenSCAD, with a box and cover to hold the pack. Each holder takes one end of one cell and has dovetails on two sides and sockets on the other two, so holders slide together into any grid. A pack is two grids, one on each end of the cells, joined by nickel strip through slots in the holders’ lips.

Use it

Open battpack.scad in OpenSCAD, pick a cell and a grid, and export each part:

• holder: print cells_x × cells_y × 2 of them, lip side up;
• box and cover: the cover slides over the box and rests on its flanges, so one screw through each pair of holes mounts both;
• grid and assembly are for looking at.

Parameter	Default	Description
cell	"18650"	AAA, AA, C, D, CR123A, 18650, 21700 or 26650, from cells.scad.
diameter, length	0	Your cell’s size in mm, overriding the listed one. Real cells vary: measure yours.
cells_x, cells_y	2, 2	Grid size.
holder_height	6	Depth of each holder’s bore.
wall_thickness	2	A holder’s block is the cell diameter plus this.
connector_depth	3	Depth of the dovetails.
retainer_thickness	1.4	Thickness of the lip under the cell.
retainer_radius, wire_cut	0	How far the lip reaches under the cell, and the strip slot width. 0 uses diameter / 10 and (diameter − 2 × reach) / 2.
cell_allowance, connector_allowance	0.2, 0.2	Bore diameter over the cell; socket width over the dovetail.
arc_cutout	true	Arch the slot roofs, so a holder printed lip up needs no support.
tie_slot	true	Leave a gap at one socket’s end for a cable tie.
retainer	true	false leaves the lip out, for an open bore.
flange_width, mounting_hole_diameter	10, 4	Mounting flanges, one hole per row of cells.
box_wall_thickness, box_floor_thickness	2, 3
box_allowance	0.3	Clearance around the grid in the box, and between box and cover.

The console prints the holder pitch and box height:

2 x 2 18650 cells; holder pitch 23.4 mm; box 70.9 mm tall

just prints exports the holder, box and cover STLs for the default 2 × 2 18650 pack into prints/.

In your own model

use <battpack-scad/cells.scad>
use <battpack-scad/battery_holder.scad>

battery_holder(diameter = cell_diameter("18650"), height = 6, wall_thickness = 3, retainer_thickness = 2);

battery_holder.scad also has batteryHolderConfig() to lay out a grid, battery_holder_box() for the box and cover, and holder_pitch() and grid_span() for their sizes. examples/minimal.scad is the snippet above.

Checks

just test takes about 7 s on OpenSCAD 2026.10.15. At four settings (2 × 2 18650, the defaults; 1 × 1 AA; 3 × 2 26650 without the tie slot; 4 × 1 21700 with an open bore) it checks that:

• a holder is one piece of the expected size, and a grid is separate holders spanning grid_span();
• a cell drops into the bore clear of it and the lip stops it, or with no lip passes through;
• neighbouring holders don’t touch, and their dovetails lock: they meet within 0.3 mm pulled apart, 0.2 mm pushed together and 0.1 mm sideways;
• the pack stands in the box clear of it, and no looser than box_allowance;
• the cover seats on the box clear of it and of the pack, and its flanges rest on the box’s with the holes lined up;
• the box and cover are one piece each, of the expected size.

just images renders the pictures.

Licence

MIT; see LICENSE.