It was fine before but since October 26, 2015, my Samsung Galaxy S4 suddenly kept losing battery so fast! It loses 1% every 5 minutes or so... This only happens when I'm not using it despite the screen being off. The "Auto brightness" setting is enabled and "Power saving mode" is also enabled. In the "Power saving mode" settings, the "Use low brightness level for screen" and the "Turn off haptic feedback" options are both enabled. Why did this happen? I've been using auto brightness for more than a month and it has been working fine until now. I tried enabling the "low brightness level" option in the "Power saving mode" but it didn't work! When I'm using my Samsung Galaxy S4, it doesn't lose battery so fast, but when the screen is off and I'm not using it, it loses battery so fast! How do I fix this?