From Feedback report:
Chromebook does not seem to sleep when connected to external display for
screen extension.
When i turn off the lid and shut down power to the display - it seems that the chromebook does not go to sleep and seems to keep consuming power -
leading to discharged battery by morning when I use it again.
If I disconnect the usb cord connecting to the monitor - seems to hold
power better.
CHROME VERSION: 71.0.3578.85 beta
CHROMEOS_RELEASE_DESCRIPTION: 11151.51.0
report id: 85838899199
Comment 1 by marcheu@google.com
, Dec 20