Question CPU at 800 mhz when AC is plugged and 2500 mhz on battery

[Hell Guy]

Hello computer specialists.
I have repaired lots of computers so far but apparently when it comes to my own laptop I'm unable to fix it.

So, the problem is that my laptop's CPU (intel i5 2520M) only goes at 800 mhz(24% in Task manager) when AC power cord is connected. As soon as i remove the cord and the laptop runs on battery the clock goes to 2.5GHZ(up to 100% in Task Manager)
The laptop is a Dell E6420 running Windows 10 Pro v.1903
The windows is OEM(I have a product key), (Someone suggested on a thread the this might be because activator modifying the UEFI files wich store processor running states)

This is what i have tried so far:
upgrading the BIOS
restoring BIOS to the defaults
Removing the battery
Checking Charger's voltage ( 19.4V )
modifying the power plans(I am curently in high performance mode)
Restoring my Windows (Which removed EVERY SINGLE program i had installed, including Office, and all Adobe programs)
Testing my CPU with Intel CPU check tool. when i checked my CPU with this software the CPU actually went to 70 %.
Also the CPU went to 100% right after the windows restored (on first boot) but only worked for about 2 minutes then went back to 25% (witch is at 800mhz)
What else should I try?


y

 

[OllympianGamer]

Do you have access to cpu options in the bios, can see there the voltage is alot lower but what happens if you just force a constant higher voltage like 1.1v.

 

[Hell Guy]

So, i actually fixed it myself by disabling Intel Speed Step in BIOS.
Apparently this is a charger problem, my laptop thinks I do not use Dell Original Charger anymore and puts my laptop to the lowest power state when connected to AC.
Thanks OllympianGamer for your answer.