Try search the forums for your inquiry.

Your answer however is that the G750 series isn't a laptop, it's more of a desktop replacement. The battery alone isn't enough to 'feed' the GPU enough power, so it goes into a low-power state sort of and waters down the performance. You can fix this by removing Power4Gear hybrid, but expect your battery to last much lesser.

This specific computer is at it's peak performance when plugged in.