USB carries 5 Volts but what is the maximum amperage? From what I read it is 500 mA for USB 2.0, so my question is, what is the point of a 2.1 Amp charger? Or am I mistaken and USB 2.0 can support higher?
The purpose of a 2.1 amp charger if USB 2.0 can only draw 500mA
usb
Best Answer
The USB2 standard mandates that a USB port on a computer is able to support supplying 500mA and that while connected to a computer the device should limit itself to drawing that much.
Outside of that specific situation so long as the device can safely draw more current then it is more than able to do so.
A lot of consumer devices that support higher current draw rates (such as mobile phones) look for very specific resistances on particular USB pins. Those resistances would be out of specification on any computer but on a wall charger they simply do not matter and can be used as a form of classification of how much current can be supplied. If they see a resistance that matches an internal list that effectively says "high current charger" then the device knows it can draw more current than the standard amount.
So yes USB2 is ostensibly limited to 500mA, and while connected to a computer almost all devices will honour that limit, but when you can ignore the standard slightly (I.e. your own devices with their own chargers) then you have some leeway and can supply whatever current you like.