Alienware 17 R3 switches between charging / battery whilst gaming

Hi,

I've been having a problem with my alienware 17 R3 (970M) for the past 3 months.

When I play games (such as overwatch or witcher 3), the laptop alternates between charging and using battery power, which causes the FPS to drop significantly and to lag. I have a 240w charger and a 180w charger, and they both have the same problem.

This problem only exists when I am gaming.

I have done a forum search, and I found 2 people with the same problem as I have:

Alienware 15 R2 battery not charging while gaming (If you look at the comments section, you will find a youtube video which is exactly the same problem I am having. However, the blue light on my charger (240w) also gets dimmer and then disappears. for the 180w charger, it just alternates between charging / battery). 

r2 15 charge problems 

Neither of their posts have any solutions, so I've decided to post it here. This problem is quite infuriating, as I can no longer play games on this laptop.

I have tried the F12 diagnostics (which returned no errors), and I have also updated the bios via the dell website.