Surface Book loses battery incredibly fast?

Have the Surface Book (1st generation) and when I take the screen, it loses so extremely fast battery. (But also if I use it as a laptop). Now, for example, I'm on the road, I've made the screen for it and used it briefly to read me a PDF and delete a few apps. Within about 10 (!) Minutes the battery has dropped from 80% to 45%. I do not remember what to do.

Replace battery

Well, there's probably the battery is now pretty broken. Whether you can exchange the you have to look.