This is a useful battery holder 3mf file that utilizes a dummy battery stl from wdwhite and a gridfinity 2x1 template by Zach Freedman I used it to clear up a stack I had. 

These are not stackable at the moment

It's noted in the part descriptions that you may want to scale up the battery models by a percentage or two in the.3mf.

I printed in PETG with a prusa mini uzing a 0.8mm nozzle

1 perimeter at 0.4mm layer height and 15% infill worked perfectly and fast