Openscad code for this and other battery holders is available on github: https://github.com/adgaudio/3dPrinter/blob/master/random_parts/battery_holder.scad Can be wired in series or parallel, or even just used to store 4 AA batteries together. The contacts fit in a slot that can extend to 2 batteries :) There is a nut trap through the center designed to fit m3 bolts and nuts, if you'd like to secure the batteries onto the contacts.I hope you print one!