Xbee powered by a battery and connected with usb at the same time

So I trying to use the Xbee with the xbee explorer board connected with an U-blox, but I want to power the xbee with a battery. I haven’t tryed yet and I want to know if I powered the xbee explorer board with 2x AA batteries and, at the same time, connect it with the U-blox via usb, which one the xbee will be powered?
The 2x AA batteries or the U-blox via usb?

That is something you need to ask Spark Fun Electronics as the board you are using is theirs and not Digi’s.