lum1988:
So you should be able to upload over the USB cable, remove it then send data over bluetooth? Even though they are on different COM ports?
Yes.
as soon as I swap the cable from the PC to a battery (5V Powerbank) it can no longer talk to the PC.
Probably has nothing to do with communications, and quite a lot to do with power supply. Where is the 5v connected to on Arduino?