To be able to charge the LiPo battery without opening the rear cover (and to optionally use a USB power supply during longer software test phases), I wanted to add a USB socket to the main case. I also wanted to keep the Micro-USB form factor that is already used on the Raspberry Pi and PowerBoost module. Fortunately, there are small USB DIY connectors available.

I drilled a hole in the slanted bottom side of the shell, centered below the hinges, close to the shell's back side, in a 90 degree angle to keep a flat surface. Then I carefully filed the hole rectangular to the size of the plastic housing of the USB socket.

Before I applied the glue I made sure to have the correct rotation for the plastic shell: The socket's solder stripes should be accessible from the maintenance door. I glued the USB housing in place with ultra-strong epoxy and let it dry overnight.

The next day I carefully sanded off the protruding glue on the outside of the USB socket and inserted the metal USB socket. And a couple of days later I soldered flexible, stranded wires to the tiny pins...

With the DIY USB plug I could make a custom connection to the PowerBoost board and keep it beeing replaceable. I wasn't sure yet if I would persue this idea, since the other PowerBoost wires are also soldered to the board so I could't replace the PowerBoost easily anyway. Well, let's see...