The Facebook app for iOS was recently accused of consuming battery life by refreshing even when you turn off the “Background App Refresh” feature. Since then though, there has been no official statement on the issue until today when Ari Grant who is the engineering manager at Facebook said they have found the issues and are working to rectify that. There will b an update today to fix that so if your phone is not set to auto update, you might have to manually do this.
“The first issue we found was a “CPU spin” in our network code. A CPU spin is like a child in a car asking, “Are we there yet? Are we there yet? Are we there yet?”with the question not resulting in any progress to reaching the destination. This repeated processing causes our app to use more battery than intended. The version released today has some improvements that should start making this better.”
iOS 9 comes with improved battery life features which makes the battery life of average newer versions of the iPhone last longer