Hello,
I've bought my 645 16 months ago and recently I discovered it had the typical cracks over the HR sensor, so I contacted customer support and they had me send in my old watch in exchange for a refurbished one. The problem is that the battery on the “new” watch doesn’t last more than 30h without any activity. It’s loosing about 3.7% /hr regardless of the HR sensor being turned off as well as the phone connectivity. Obviously I contacted customer support and I’m currently waiting for them to answer, which usually takes some time. But I hope that this is something about software rather than hardware and that there’s something I can do without having to send the watch again and wait once again more than a week without the watch.
Here’s what I’ve tried so far:
1-Factory reset and sync to my Garmin connect account.
2-Factory reset without sync
3-Factory reset HR sensor and phone connectivity turned off
4-Followed a guide from this forum that instructed to set the music provider to either “my music” or “phone control” and do a normal shut down of the watch.
5-Left it charging for several hours after 100%
6-Factory reset and allow the battery to drain without setting anything, once drain, connected to power supply watch turned on and apply settings. (as if it where brand new)
Needless to say nothing has worked so far, I assume that the battery on refurbished watches are new, and even if it’s not it should last more than one day, my old watch was lasting almost a week without activities.
Any help will be welcome, thanks 
