Games lagging after few minutes

[Gabikts]

I have my notebook only 2 months and I don't know why every game that is running on dedicated GPU starts lag after few minutes (5-20 minutes) when it's on charger without battery.


Games: Battlefield 4 Normal settings and everything enabled (45-50 FPS) after few minutes (1-12 FPS) and still lagging on lowest settings
Counter-Strike Global Offensive high settings and shadows on normal (60-150 FPS) after few minutes (5-20 FPS)


Only thing that I can do is restart game but it starts lagging again.


charger + battery = lagging
only charger = lagging
only battery = everything is working fine but after 2 rounds of CS GO on high performance power mode 40% of baterry is down that's reason why I can't play on battery



My specs:
CPU: Intel Core I5 4200u 1.6 ghz up to 2.6 ghz
GPU: Nvidia GeForce GT 840m 2 GB (latest 347.52)
RAM: 8GB
OS: Windows 8.1 64 bit
Resolution: 1366x768 60hz
specifications are good enough to run this games fine



My plug and battery power option is set on high performance

I don't know if it's caused by cooling or power settings or it's GPU driver problem like there:
https://forums.geforce.com/default/topic/800968/geforce-mobile-gpus/geforce-gt-840m-underperfoming-after-a-while-performance-cap-power/

Please help.

 

[WildCard999]

Get a program that can monitor/record your temps for both your cpu/gpu like HWmonitor. It sounds like either the cpu and/or gpu is overheating and causing performance drops.

 

[Gabikts]

Thank you for answer I will try it