Expandable interlock battery holder

A battery tray that can be expanded as necessary with the size you need, simply locks with the dovetail joints.
The is no limit to how many can be connected.

Panel size: 35 x 35 mm
Height: 11 mm

Wanted to make it tight enough to be able to mount it vertically on a wall or board.
The hole in the middle you get when connecting 4 panel can be used to drive a 3mm Non-Countersunk Screw Head to hold the board up.
Batteries shouldn't fall out.

In a previous iteration I had 4 AA batteries on 1 panel
The 18650 battery tray is still a bit too tight, will fix it soon.