I updated 2 nights ago, and yesterday was my first full day using my 1520 with 8.1. Maybe I was using the phone a little more yesterday, but it seems like the battery is performing not quite as well as it used to. Any suggestions on this?
If you go to Battery Saver, under usage, take a screenshot and post it here. I am curious to see what would be running in the background more to cause this.
This is a preview build (not the final build ) and since you are using your lumia 1520 more than your normal usage it's normal to have such results. You may also try a hard reset which will also solve many problems including battery drain.