[supdawg]

Taken from a post I did at XDA inquiring about USB fast charging...

"the ma rating of the charger really makes no difference as the phone (and prior htc phones) will pull <500ma if they detect they are plugged into a computer or non-official charger and 1a if they detect an htc charger (which can even damage 500ma chargers). The way this is detected is through grounding of one of the microusb pins in the official charger (and indeed many generic chargers but not all will be detected this way). Absent this grounding (I forget which pin), it will charge at a slower speed. I know of cheap 500ma chargers which have been caused to smoke by attaching a cable with that grounding fooling the phone into thinking it is an oem charger. Many chargers labeled 1a will charge at the 500ma rate as well."