Lenovo laptop with Intel CPU remains at lowest clock

After many trial & error attempts, I found out what the issue was: My Laptop (cannot confirm if all Lenovo Laptops have this behavior) will throttle the CPU to the lowest setting if no battery is plugged-in. I don't know what the fine Lenovo engineers have been thinking...

I have a similar setup (Lenovo T440, i5 4300U, 8GB DDR3 800mhz, SSD with Windows 7 preinstalled), and also experienced the computer running at the base clock speed randomly.

I opened the Lenovo Power Manager 6 app, and found that under the 'Advanced View' the system's Performance was set to 2 out of 7 green circles (7= max performance, 1= lowest performance) for all of the predefined scenarios (1: Video Playback; 2: Power Source Optimized; 3: Maximum Battery Life; 3: Times off (Presentation); 4: Airplane). I went to Maximum Performance and clicked the "Restore Default Settings" and saw the green circles increase from 2 to 6 (much better!) for the Performance setting. I then checked the Core Temp application I installed, and saw the CPU pick up some speed: jumping from 800mhz to 1.8ghz!

I'm not sure where the software wires got crossed, but refreshing the settings in Lenovo Power Manager 6 app seemed to fix my issue, at least for now! Good luck with your settings!