My battery darin was related to the GPS and Google GPS tracking,
disabled both ....
System is good again...
That is a known issue with Android 6 and affected a lot oft manufactures...
Google it....
The calculation is for sure a bug.
The is also sometimes related to GPS, like on mine.
Plesse Google for it, there are multiple factors which can cause this and even more solutions...
Besteht would be to have Nougat installed..