This is a battery holder for the batteries that come with the Tetrix systems. There are two variations in the files. One has mounting tabs on the short ends that have the Tetrix "flower" mounting holes. The other does not have the mounting tabs. Underneath the flower pattern is indented in the bottom. So if you choose to mount it through the bottom, just take a drill and finish the holes that you need.
All you need to add to this model is a strap of velcro to hold the battery in.
There will likely be another version with only one exterior mounting tab added soon. We have one on our current robot and it is mounted securely to our 80/20 frame with just one fastener.
If you have any questions or anything you'd like changed, drop us a line at [email protected] or catch us on Facebook "Trial and Error Robotics"
I recommend to use shells. I printed this with 5 shells and it is strong even though the walls are pretty thin.