My Note8 loses charge quickly. Not sure what is going on.
Go into battery settings, there is an app running all of the time. Turn it/them off to not notify you, always run in background.
Got a new pixel 2 a few months ago, leaving the Samsung line because of their curved screen edge. Pixel 2 battery lasts about 2 days.
Bought one of those activity monitors and installed its app. That app would drain my battery in less than a day. Easy to find what was doing it.