Question about Samsung Inductive Powerbank EB-U3300

I bought such a powerbank and after 11h 30 min it only reached 75% charging capacity. When it was finally at 100%, I put the phone on it and then the powerbank was empty. Samsung said that the powerbank would be charged in 3 hours via the phone. I am worlds away from that. How long does it take you? Are you otherwise satisfied with it?