I used a Raspberry Pi 3 to make a "Pi-Hole" (https://pi-hole.net/) local caching DNS server, and ad and tracker blocker. Being a full-time part of my network, I wanted reliability. The thing about Raspberry Pi's is that if power is interrupted you can sometimes have the SD card get corrupted and require re-imaging. Not hard but the network gets interrupted.
I added a smart UPS from LiFe PO4wered (https://lifepo4wered.com/lifepo4wered-pi3.html) to keep from corrupting the SD card but now it wouldn't fit any of the other 3D-printable cases. And that's where this comes in. That LiFePO4 UPS is very cool. Best to let their features page explain it, but it's amazingly powerful both in battery and configurability. The hole in the top of the case is to get to the touch pad power button.
It's drawn from the ground up but I followed the design of Baudler ArtDesign. This case is taller since I didn't cut out the the USB and network connectors, and it needed to clear the LiFePO4 battery and holder. I put some ducting in to help with the air flow over the chip heatsinks and recessed the fan down into the case for a cleaner design.
The fan is just a 30mm x 30mm x 8mm Pi-Fan I got at Amazon and it's a friction fit into the recess. The fan really makes a difference in chip temperatures. It was running 115F with no fan and no case as reported by the Pi-Hole software, but with the fan in this case, the temperature comes in at 96F while running the 5 volt fan off 3.3 volts since the LiFePO4 UPS covers the 5 volt terminals. I might modify things to get 5 volts for the fan, but that's another story. It's still just shy of a 20F drop in operating temperature.
The top part is a bit of a problem. Just about no matter how you print it, there is going to be a lot of support. The bottom prints clean with no support.