That's what most laptops do when you unplug to conserve power. The design is to drop the CPU speed, switch off the GPU and more.
Are you reporting that the seller and maker were unable to answer this question?
The Lenovo's here have too many control panels so without me getting the product manual out, your best bet is to dive into the user manual and learn about power controls.
Hello, I have been noticing a slight bug/software setting with the Lenovo y400 model laptop. Basically whenever I am playing a game or doing heavy processing it runs fine, while plugged in to the wall. However the second I unplug the laptop from its power source it gets very slow almost by 1/2 what it was running at. Is there a fix for this or is it built in and not editable?