Forerunner 45 - Software 5.10, battery life

no problem here try a hard reset, push the Light button (upper left) until the watch stop.

then start it, sometimes this procedure help to "reset" the watch to usual behaviour.

Thanks, will give that a try.

Same for me.  I've not noticed any change in battery life - certainly nothing as dramatic as yourself.  As in my other post, I did have to do what I would all a "hard reset" when my 45 stopped syncing its data up to the server, although it did seem to be still talking to Garmin Connect on my Android smartphone.  In other words I did a reset to factory settings, deleting all of the data - just a reset preserving the data didn't work.  Since I did that reset, I've had no problems over the last couple of days. [Just to clarify my terminology... What "6127890" described, I would call a restart not a reset - just "switching it off and on again".  Actually, the Garmin manual calls it "restarting the device".  The manual calls what I did "resetting all default settings".]

you right (and i don't know why my profile sometimes is not mine).

-Restarting the Device-

https://www8.garmin.com/manuals/webhelp/forerunner45/EN-US/GUID-FE7137DB-B929-4BD6-B76F-EC5E27AD50B3.html

-Resetting All Default Settings-

https://www8.garmin.com/manuals/webhelp/forerunner45/EN-US/GUID-6742ACA9-80F0-4460-B4ED-D68056741A23.html

In this last case some explanation on the link below on how not to loose everything on the watch.

You will not loose everything already sync (activities for example) with Garmin Connect.

https://forums.garmin.com/outdoor-recreation/outdoor-recreation/f/fenix-5-plus-series/149936/hard-reset-firmware-reinstall-data-location-and-backup

I have the same problem. new firmware decreases the battery life dramatically! before it was about 5 days but now i have to charge it every couple of days. i did a reset factory but haven't noticed any change in battery life.

Current state of mine: charged in full last Saturday morning. Since then it's recorded 5 runs/55km/4.5 hrs and I charged it from an indicated 20% back to full on Tuesday. It's down to 1% on waking this morning (Friday). I wear it all day/night and only connect to my phone to sync after each activity. So not great but not as bad as I found initially after the new update.

My 45 battery was poor for the past six months, 3 days max. The 55 battery looks like 12 days. The battery in the 45 did not degrade evenly over time, but jumped down occasionally in performance, those jumps were probably tied into the updates on the device.

I have the same issue, the Bluetooth connection also not stable. When lost connect it doesn't automatically re-connect.