[bradart]

USB ports are only rated at 500mA. The optimized charger that come in the box with a wall adapter chargers at 1A. A lithium battery can charge at a rate equal to that of its mAh rating (a 1600 mAh battery can charge at a current of 100mA) but anything higher than that can damage the battery. The dual plug usb cords for external dvd drives and hard drives plug into two ports in series to double the power rating of 500mA and make it 1000mA (1A). So, if you really want to charge as quickly as possible from usb, thats the way to do it.