Not all USB ports charge at the same rate. All are 'current limited' based upon their design. Cheap universal chargers tend to be more limited, IMO. The charger that comes with the Hero, so far, is my favorite as it seems to do a complete charge in less than 2 hours. The charger I use overnights (cheap universal model) will NOT fully charge the phone if I leave the display running as a nightlight. The USB port on my office computer takes about 4 hours to ramp the battery back to 100 percent. All different devices with different charge rates.