To fix the battery idle, find out which apps are consuming most power, clear cache and temp files for those apps. Use cleaner to remove temp files. If this does not work, then another method is there. Let the battery discharge to 0% once and phone will switch off. Now charge the phone to 100% . Now check the battery backup time again. Discharging resets the battery manager. Let 2-3 battery charge discharge cycles happen. Idle power usage will definitely improve. Also if you are using third party power manager, please remove it. It will unnecessarily use battery power while phone is idle to monitor other app power usage!!!