i have the USBPT for my 901 and 801, i have to disagree on running it through a computer vs main. I get the same throat hit either way (both considerably better the batts) It probably depends on your comps power supply. I have a 1200wt PC power and cooling. I bet if its a 500 or less, or off a laptop it will probably be considerably weaker then a direct shot to the wall.