Battery issue

Two weeks ago I purchased a Vivoactive 4s -

Before bed last night my battery was at 84%, and when I woke up it was off. I turned it on and it was at 4%. 

I charged back up to 100%, and 5 hours later its still at 100%? 

Has anyone had this issue?

I've updated it,  and have turned it off for 5 mins.