I have an iPhone 6+ (running IOS 9) and I go to sleep every night using the Nature Sound app to lull me to sleep. I have about a 2 hour and 5 minute playlist of various sounds that it cycles through. The past two mornings, my iphone has been "dead" meaning I have to do a hard reset to get it to respond, which of course means that my alarm doesn't go off in the morning. The battery is fine and once I get it to reset it shows up at 100% since the phone is plugged in overnight. Luckily my cats still wake me up early enough that I haven't been late to work but still, frustrating!