Good Day! I have encountered a huge battery drain issue with IOS 8.4 on my Iphone 4s. Battery drains even during sleep. Using the wifi/3G just kills it very rapidly and makes the phone very hot too. Battery is not faulty or warned out. Battery drains with the rate about 1% / minute while browsing with safari and about 1-2% / hour while sleeping. Everything that had a switch are turned off , and the phone was clean-restored several times. Has someone encountered similar issue? Thanks.