It's been identified before and also have now noticed that the battery life of the phone has been changing drastically for the last few weeks after upgrading to Android Nougut, especially draining very quickly after reaching the 25-30% mark.
Anyone else having the same problem with the update?
Perhaps the new release of Android 7.1 may help rectify this problem but not sure…
For what it's worth, I'm in the beta program and running 7.1 and it's been excellent - battery life remains outstanding.