Hi, today I've just make a simple ON/OFF switch to my axo box, allows me to keep the micro USB input for doing two things :
1. Still have access to the axo-board for making new patch or everything else from outside the box
2. Charging the battery power bank I've placed inside my box.
Now my axo can be turned on & off from be battery powered and work everywhere, or used like just before with my computer or any usb 5v devices.
So for the community I think it might be nice to explain how to do it.
This is what I've done :
First you need to understand that the power bank don't transmit any data info to your axo. Because of this I draw in black the USB cable needs data, and in red the usb who don't need usb data. It really matter because inside a USB cable you'll have 4 colors of cable. Green & white for data info, red for 5v and black for GND like this picture : 
You'll only use a stereo bipolar on/on switch. Make sure it will have 6 branches. like this one I've used : 
And I've soldered it like this :
So now :
1 : when I plug a USB cable to my female micro USB input, my axo turn on, I still have access to the data info so I still can use it with the axo-patcher or sequence it from a DAW, and the battery is charging in the same time.
2 : when nothing is pluged to this female USB in, the axo is OFF.
3 : Even if nothing is pluged to the female USB in, I can turn on the axo by switching on my little "switch on/on" and the battery start powering the axo-board.
Now set up these little things inside a box, let the switch in a place where you have access, and go outside to play with your new patch & new box everywhere 
Cheers !