I know this is an ongoing discussion, however I was never too preoccupied with it until recently. I tried to research the subject, but found so much contradicting info I have no idea what to think now. I'd like to invest in a battery case or a powerbank (thinking about Mophie's Juice Air pack or one of their power reserves), but I'm worried that even casual use of either of them will drain the iPhone's actual battery when it's on its own (or limit its internal capacity, so to say?); how wrong am I? How to use them to prevent the suppositional battery drain? Any tips? Or maybe I should forget and it's not worth to invest in such things at all? Every info and advice on the matter is greatly appreciated .