Count me in for battery weirdness as well along with closing the lid problems. Battery is at 10% and won't charge above that (shows plugged in but not charging). Strangely, the battery doesnt seem to be going below 10% either and shows no remaining battery estimate.
Hold the Power Rocker Up for 15 seconds as you power the unit up from a cold boot, this brings you to UEFI Boot Screen, exit and save and it should reset the battery.
I also have the issue of my SP2 not going into sleep mode properly and waking with little battery power left sitting overnight.
Secondly, the other day the battery was saying "9% battery left" and didnt increase when plugged in. I saw a fix on another forum that seems to have worked for me.
Unplug and power down, let it sit for 20 min or so, then plug back in (still powered down). Let charge for 20 min or so, then unplug it and power it back up.