We all can lament on how horrible it is charging something over USB with Android. Seriously, that stuff takes all day. Well now, thanks to the rather well known Chad (of AnthraX kernel fame), a method has been developed for A/C charging on any input device; be it USB, car charger, or lightning-powered-taco.
Granted, this is of no use to you if you're not a kernel developer. But if you are, then you can add this patch into your kernel build to allow A/C charging over anything. You'll still be limited to the actual output of your charging device, but at least now your phone won't be the bottleneck. "But how do I get this magical patch," is what you're most likely shouting right now. Well, calm down, because you can find it on this very site. In fact, you can find it right here. If you're just a regular old rooter and end user, make sure to let your favorite kernel dev know about this so they can add it in! Hop to it!