The Ultimate Guide to Solving iOS Battery Drain
appinstructor.com/blog/2014/the-ultimate-guide-to-solving-ios-battery-drain
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
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.