17 R5, low performance after removing the battery

I have a two year old Alienware 17 R5 Laptop, which I had to open to remove the battery (bloated). The battery was removed and not replaced.

Now my laptop is running 100% of the time plugged in the outlet. However, the performance drastically lowered.

E.G:. When running CSGO, before removing the battery I would have a constant 300 FPS (of course with a minor variation). Now without the battery, it is varying from 90-100 FPS.

No changes in the software/hardware were made besides the removal of the battery.

How to solve this? Shouldn't it be running full performance now that its 100% of the time plugged in? Any suggestions or solutions?

My Specs:

Alienware 17 R5

Core i7 8th Generation

32 GB Ram DDR 4 2666MHZ (2x16)

256 GB SDD + 1Tb HDD

GeForce GTX 1070