A handy, cheap option for powering the QCX would be the 18650 cells commonly used in e-cigs. ?Chargers and cells are commonly available at every vape shop. ?You can get battery holders that put 3 in series and you will get between 10 and 12.6V over the discharge cycle. ?You could do 4 in series, but you would be looking at 16.6V fully charged, which might be a bit much for the QCX. ?Cheap cells will get you a 2600mAh battery, good ones could be up to 3600mAh, plenty for the QCX?
You will need to work out yur own power management system though - You don't want to draw them lower than about 3.3v per cell for best life, and below around 3.0V per cell can be actually dangerous. ?Either closely monitor your voltage on the QCX or build in some kind of voltage alarm or shutoff. ?You can buy protection PCBs on Ebay for cheap that should do it, or you can buy protected 18650 cells that may be harder to find.
Alternately, get a drone battery for a neat premade package- Zippy Flightmax or Turnigy are two brands, I have a Turnigy. ?Again, chargers are easily available, but you will need to protect them against overdischarge.
I would worry USB chargers like you are planning might introduce noise... ?they typically run on a lithium battery, and might use a boost circuit that could cause some RF noise. ?May ir may not be a problem, but just using straight lithium cells would be cheaper and there is no chance of noise.
