Great article on iOS (iPhone) battery issue and properly diagnosing them:
I worked on the Genius Bar for almost two years, and the most difficult issue to solve was short battery life. It was extremely difficult to pinpoint the exact reason why someones battery was draining.
I made it my mission to discover the specific reasons for iOS battery drainage. This article is a product of my years of research and anecdotal evidence I gathered in the hundreds of Genius Bar appointments I took during my time as a Genius and iOS technician, as well as testing on my personal devices and the devices of my friends.
This is not one of those Turn off every useful feature of iOS posts that grinds my gears. My goal is to deliver practical steps to truly solve your iOS battery woes.