I have an iphone 5 and my battery sometimes drops by 20% or more instantly. Just now, it dropped from 30% to 7%... This happens quite often. I think some of my battery cells are dead and am wondering if the car charger has anything to do with shorting a battery life. I got a battery replacement under warranty last October, was fine for a while, until it started acting up in the past couple months. Recently, I started using a car charger more often because I have been on the roads a lot. I heard from somewhere car chargers should be used only for temporary due to its electricity not being as clean as from the wall outlets. Is this true?