Could anyone give an explanation for this? Not the first time it's happening.
Auto updating on or off?
Good question. Mine just drained 39% in 20 hrs and battery usage showed 2% Tablet Idle and 2% WiFi On - that's it. And I'm on 6.0. I'm generally seeing 7% drain/day with zero usage of the tablet and WiFi and Location turned off (as well as WiFi scanning turned off, etc.).
Auto updating on or off?
Looks like your Google app has run amok. I assume you've tried rebooting? Weird battery/app behavior is hard to pin down after just one cycle. You'll need to watch what it does over a day or two (after rebooting) to see if you can figure out a pattern.
How would you be able to tell if the battery itself is reaching end of life?