If you just upgraded your iPhone to a new version iOS system from the old version for example from iOS 10 to iOS 11 or iOS 9 to iOS 11, you may notice that your battery is draining twice as fast or more after the upgrade. Sometime system can be lagging too. You may heard that you can turn off some features to help the battery to stay longer. However, if a smart phone needs to turn off all the features, what is the point of having a smart phone right? Here is what you can do if you experience battery issue after upgraded.