Quote:
Originally Posted by mbovenka
That's 4.25W (5 x 0.85). A USB2 port is rated for 0.5A (2.5W) and a USB3 port for 0.9A (4.5W). So if your computer has USB2 ports, that fits. If it has USB3 ports, it should be as fast as your Kindle charger.
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Officially, or originally. Apple was first with a higher current USB-A port that did USB 2.0 speed and 1A or more for a DVD writer or something similar.
Then there is the compatibility issue. Quite a few standards for the gadget to measure the D- & D+, or communicate and then decide what current can be taken. The 0.5A (=500mA) is a common default if it makes no sense, but it used to be 0.1A (100mA).