Like to share my verified working solution on X230, Windows 8.1(and for those looking for ThinkPad Power Manager in Windows 8.1):
0) disable anti-virus software
1) install Lenovo Settings Dependency package for Windows 8.1(no need to reboot when prompted)
2) Install Power Management Driver for Windows 8.1(reboot if prompted)
3) Download Power Manager for Windows 7
support.lenovo.com/eg/ar/downloads/migr-70601 (it won't let me post the link, add http in the front)
3a) run .exe file to extract files, which are stored, by default, at C:\DRIVERS\VISTA\PWRMGRV
manually set one by one on all .exe files to run in Windows 7 compatible mode.
3b) run setup.exe to install power manager(reboot if prompted)
verify that installed .exe at C:\Program Files (x86)\ThinkPad\Utilities are all set to run in Windows 7 compatible mode (if not, set it each again manually)
4) Now launch pwmui.exe and everything works as before like in Windows 7.
Final note: when running Battery Maintenance->Batter Gauge Reset, be patient and set Windows 8.1's
power options to "Maximize Performance". Keep AC power attached and wait 3 hours or more until reset is completed. The Status tells it's doing discharging or charging, time remaining shown is not accurate and sometimes doesn't seem to be moving/changing, just be patient!
I have my X230 one year and a half. The battery suddenly stops holding power and appears losing capacity. Remembering Lenovo used to have Power Manger which can calibrate/reset battery gauge, I searched Lenovo and the Internet and found nothing nor real solution for Windows 8.1. Some suggests adding/editing Windows registry to set battery "start charging" and "stop charging" thresholds, which I did but didn't seem to help much.
After pulling some hairs and a day trying, I finally got it working. Initially it showed my battery condition "poor" and holding only 10% of original capacity. Now it's in "good" condition and holds 99% of original.