All I could find was this on the outside of the box: USB 2.0 high-power port required for Hi-speed transfer and charging.
But inside the instruction manual it says "The battery can also be charged using an AC adapter (not included) or a car adapter(not included) and you will be able to play your device while charging with one of the adapters.
NOTE: Some low-power USB ports may not be able to provide enough charge power."
Good luck!
