Since installing the first iOS 9 beta, many users are experiencing abnormally quickly-draining batteries.
Users from /r/Apple, MacRumors Forums, and elsewhere report it’s difficult to get through a single day of normal-to-light usage without recharging, with battery drain continuing without use. While this is the first iOS 9 beta and some poor battery life is expected, user reports seem to indicate this is abnormal for even for iOS betas.
Reports indicate that iOS’s Settings app shows a large percentage of battery use attributed to Home & Lock Screen, despite statistics showing a low time on screen. Some users theorize this is because of lack of optimization with iOS 9’s new Search features with Siri suggestions. Other users believe that iOS is ignoring Background App Refresh settings, leaving 3rd party-apps unoptimized for iOS 9 running rouge in the background.
In my third day of iOS 9 beta use, my iPhone 6 has been below 50% battery every day before lunchtime after a full charge overnight. There seems to be no difference between using iOS 9’s new Low Power Mode or not.