My common sense is tingling.
How can this possibly work on USB? USB 3.0 (the newest iteration of the technology) can support up to 900 mA on one port. A typical laptop battery will need like what- 3,000 to 4,000 mA? You're going to need to at least use a 3 way usb splitter on this. And that's only if you have USB 3.0. You're going to need a lot of USB 2.0 ports, and you're pretty much in the dark (pun not intended) with USB 1.0.
However, given the size of the cable. I want to guess that this is the netbook model. 900mA might be sufficient.