If you're just using the computer to transfer files, I wouldn't worry about the message. I think a recent security update has changed the way the "slow charging" notification works, and makes it pop up more consistently. It's normal that a computer would not have the fast-charge ability through the standard USB ports. It IS charging, just at the standard slow rate, while it's connected. Unfortunately, a side effect seems to be that the "slow charging" warning is popping up even for people using the original Samsung quick chargers, and certified 3.0 quick charge charger units. I get it at random on any wired connection now, but it still seems to charge fast in those situations, so I dunno. I never see it when using my Qi fast wireless charger, though. It's very strange behavior.
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