battery charge life

I got a Garmin Forerunner 45s for Christmas. I am able to get at most 280 mins (4.7 hours) of activity before it needs to be recharged. I have followed every trouble-shooting suggestion on Garmin Connect. When I am not using it for running (that's what the 4.7 hours is), I have the connection to my phone turned off. I have the most basic analogue face. Today I went for a run. The battery charge was at 20 %, at 45 minutes into the run, the charge ran out. The weather was not exceptionally cold (-2 C).

I did contact Garmin Support but the email response was say the least. I've never owned a fitness tracker before, but it seems to me that I have a dud watch.

Before I make a stink about the battery charge being unacceptable, and seeking a refund, am I missing something?