I just got my new phone about a month ago and have had a problem happen a few times. I always plug in my phone to charge while I'm sleeping, and it always is at 100% when I get up. By the time I get to work (an hour or two later) the battery level is down to 40-50%. When I look at the battery level chart in Settings, there is a huge spike downward right away, then it levels off to normal battery drainage (see attached screenshot)