Flexing battery holders with 2- and 3-cell compartments

thingiverse

Thingiverse user pcoulbourne asked me to extend my flexing battery holders with integrated spring project to support multi-cell compartments that house two or three cells in series and are held together by a single plastic spring. With more than one cell lined up, the pushing force of the spring is likely to lift the batteries up at their joining point and push them out of the compartment. Longer cells also tend to cause warping. To solve these problems, I added cutouts at the center of each cell to allow for a better grip when handling the cells, thus reducing warping, and an inside overhang between the cutouts to prevent batteries from popping out. The included fully parametrized SCAD file is an extension to the initial version, so it can also be used to generate all single-cell compartment battery holders from the initial project. However, the STLs provided here are only for 2- and 3-cell compartments of some common cell types. I started by including ready-to-print STLs for AA, AAA, C, and 18650 type cells, with others potentially following. You can easily generate multi-cell holders for any other cell type yourself by adding the corresponding module calls in the OpenScad source file. It's worth noting that when securing two or three cells with a single plastic spring, even small variations in cell length become critical since the differences are duplicated or tripled. Small differences can be compensated to some extent by adjusting the thickness of the pole contacts. I recommend loading and unloading batteries from the plus end of the compartment (opposite side of the spring) and sliding the cells in as shown in one of the pictures. Pushing batteries through the overhang generates stress on the side walls of the case, especially for smaller cells. For further details, please check out the initial version of this project.