So I just got me one of these. And a heavy rainstorm just blew over, and I don't trust it not to have lightning at some point. So it's charging my GSM Gnex, on the slower output it seems to be gaining a percent of my Gnex's reported battery level every few minutes, and having kicked it from 50% up to 70%, the Anker is still reporting full (all four LEDs still lit.
Lovely gizmo, thanks for letting us know about it.