Quote:
Originally Posted by JMikeD
You need one that will provide at least 0.85A. If it's less, then you may only get trickle charging.
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No. A computer USB port is only rated for 500mA with USB 1/2.0 and it is possible to supply less due to having a nonpowered hub or unusual hardware restrictions such as a battery powered device. The Kindle doesn't require 850mA to charge properly and will work fine with less current but with a corresponding longer charge time. Not all Kindles even come with the wall charger and you are expected to provide your own or charge via a computer.
What does matter is how the two data lines in the USB connection are wired. They're used to signal the device being charged as to the capabilities of the charger and how much current it can draw safely. The way it does this is to connect the data lines with specific values resistors to the ground and power lines in the USB connection. The issue is that there are several different wiring schemes for this along with differing values of the resistors. If the device doesn't see this or the values aren't what it is expecting then it may refuse to charge or charge very slowly.