I had this problem too. Incorrect battery % and my battery seemed to drain faster. At one point it was fully charged and with on 3 hours of use it was down to 10% and then it shut down. So I was looking through the forums and some of them said to to restart the phone. Backup. Erase all content and settings and let it reboot and then restore from the previous back up. It worked for me. My battery than went back to being normal the way I'm used to using my phone. So for those having battery issues, trying restoring your phone. Maybe it will work, maybe it won't but I'm just telling my experience.