Recently some iPhone 4S users, and some iPhone 4 users who upgraded to iOS 5, experienced terrible battery drain. The causes of the battery drain may be different for different cases. Here is what I experienced.
My wife has an iPhone 4 bought August 2011. Recently my daughter upgraded my wife’s iPhone 4 with iOS 5 to use iTunes Match feature. I don’t remember since when, my wife started crying for the battery drain.
We try various adjustments to the settings and can not figure out why. Accidentally, I noticed her phone is doing the iTunes WiFi Sync when we come back home from outside. So I stop the auto sync feature. Since then, every full charge will work for a long time.
By the way, my iPhone 4S always works great!
Hope this may be helpful to you.
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