I was having same problem with my battery. I tried rebooting it and it did no good. Then I tried restoring it to factory setting and reloading it one application at a time. After that, the screen would say "loading" upon waking my phone up. And it would freeze randomly as well.
I called Nokia, explained the situation and they took me to a link at nokiausa.com. From there, I downloaded Nokia recovery and repair tool to my computer. That file extracted the 8.1 from my phone. (They asked if my upgrade was the predeveloper's--which it wasn't. It was from ATT.) After using that tool for bug fixes, I then reloaded 8.1 from my phone's update setting and everything seems to be fine. I am using less than 3% battery life per hour. Not as good as before with 8.0, but much better than when I first upgraded to 8.1. I feel this is good because I am now keeping location activated constantly which I never did with 8.0. This "fix" from Nokia seems to have cured my freezing problem as well. Of course, I just did this yesterday evening, so it remains to be seen exactly how well the phone will perform. But for now, it seems Nokia has solved my problem. Gotta love Nokia!