This is what I just did in attempting to solve the battery problem: I wipe the phone (Setting, erase all), set up the phone as new, then connect to iTunes to restore from a backup. After that, I reset my settings. I turn off location service, data, bluetooth, and turn my screen brightness to the lowest. I only keep my wifi on.(edit: correction, wifi was not connected) I then do the music playback with the phone switched off, with occassional checking of the battery usage. I was surprised to see that after 45 minutes (as of now), the battery stays at 100%! This can't be right, can it? I'm using a 64GB iPhone 5.