The Surface Book 2 is sleek, svelte, and damn powerful. Sadly, it also struggles with a maddening battery drain issue during intense loads or when gaming, even while plugged in. This tends to affect the 15-inch model most. Thankfully, there is a workaround you can try to mitigate this problem.

from https://www.windowscentral.com/how-fix-surface-book-2-battery-drain-issue-while-gaming
https://www.windowscentral.com/sites/wpcentral.com/files/styles/large/public/field/image/2018/10/surface-book-2-scaling.jpg?itok=5AYwvyaH