I designed this model for people to create a 18650 accupack with. I left the connector holes internally on 3mm so you can use your own connectors of choise to connect the 18650 batteries together. The top and bottom have lanes, also for easy connection of the 18650 batteries. The 3mm holes can be drilled out to the size that is needed / you want. You can stack as high as you like with this design. Just print more models and stack them. This is the large 18650 accupack wich has space for 50 18650 batteries per layer.

I also have a model on CGTrader wich has space for 25 18650 batteries per layer. This accupack can be found here: http://www.cgtrader.com/3d-print-models/hobby-diy/electronics/18650-accupack

I also have a model on CGTrader wich has space for 100 18650 batteries per layer. This accupack can be found here: http://www.cgtrader.com/3d-print-models/hobby-diy/electronics/18650-accupack-mega