The CAD Guy and Airwaves Ted created both nice battery storage systems. I prefer the simpler version of Ted's design (it doesn't need an additional bottom to be stackable), but both look great!

Here, I remix the empty box to be printed more easily than the original one.

I hope this might help some of you, because the original ideas are really nice :)

Have fun and keep printing, and thank you, Ted, for your design!

PS: This box is designed to be scaled to your needs :)

New: 4 18650 batteries in a box. (This model is pre-scaled to 80%)

I printed mine in PLA, with 5-10% infill and 130% speed at 0.2 mm.