Originally Posted by kf_man
I just wanted to let you know that there's actually a known battery drain issue when upgrading a Surface RT (doesn't affect Pro) from 8.1 Preview to 8.1 RTM. Upgrades directly from 8.0 to 8.1 RTM won't see the issue.
You can fix the issue on affected devices by following the instructions on the Surface support page (Sorry I can't post a link, bing for "Surface RT and Surface 2 battery and power" and you should find it).
I'll copy them here for reference.
Here is the thread on the surface support site: http://www.microsoft.com/surface/en-...tery-and-power
Note that this is Surface RT specific, not applicable to the Pro, nor other RT devices.