You might be having an issue with Windows Update getting stuck checking for updates. It's really good at running only when you're not using the computer, but if it's having issues, it will use up CPU, RAM, and Disk resources like there is no tomorrow. Because of that, it will kill your battery faster than you can spit.
The first thing to try is the Microsoft Update trouble shooter (
http://go.microsoft.com/?linkid=9830262). As soon as it is finished, select close, and go to the control panel, windows update, and check for updates.
If that doesn't work, try from an elevated command prompt (i.e. Command Prompt (Admin)):
Dism /Online /Cleanup-Image /RestoreHealth
Then if that still doesn't work, try it again while booted in Safe Mode with Networking.
And if that doesn't work, backup your data (twice) and reset back to factory. But make sure you have your battery fully charged, and have the power adapter plugged in. After the reset, make sure you have all your windows store apps re-installed and run at least once, reboot.
Then start the windows update processes and finish every update possible (keep going back and check for updates, You might get a firmware update or two, again). After all the updates are installed, reboot one more time, then re-install your desktop programs (Office, Quicken, PhotoShop, etc.).