When I first got the Power Bear Samsung Galaxy S5 7800mAh extended battery I charged it over night. Upon turning on my phone there was a quick drop to 99%, which surprised me. I'd have thought there would not have been any drop in power for a while. It's been a week and I have been charging it overnight. I have been doing  a lot of political phone canvassing recently, which covers a 3 hour block of time and averages 65 calls.