[Harveystyles]

"The AC charger is delivering 5V at 1A max.
USB ports are also 5V, but typically deliver less amps (as far as I know it is supposed to be below 500mA per port). I think the hero negotiates for a lower current than 500mA, but plugging in a power only cable will basically max out the port."

"So I tried one of those split usb cables you get with portable 2.5" hard drives. I plugged it into my phone, and then connected the power usb point and not the data point to my laptop. Now my Hero said it's charging from AC, and charging speed was a lot better (I use vizBattery to see stats)."

again, hope this helps!