Since I failed to install Dec 2013 update, My sp2 works only for around 3 hours. 100% charge and count says 2 hour XXmin left. And 100% for more than 2 Hr... Now I found reason why... Not the sollution This is the powercfg screen capture right after (volume +key with power button) boot Check Full Charge Capacity This is the next charging captrue Everytime I restart Full charge capacity is chaging.... It seems 40,404mWh is normal charging cpacity. but most of time Full charge capacity is set to 20,000 ~ 30,000 Is this Firmware problem? or defect SP2... I am tired to ask MS supprt they know nothing about serious thing.