Significant Battery Drain Issues with Fenix 8 - Request for Assistance or Exchange

if you are seeing unexpected battery drain, probably the first suggestion is to reboot both your phone and watch. This resets the bluetooth connection between them, which can often be the culprit.

I alway do that since 2 months perhaps sometimes i forgot but it is for me like a reflex . i do not know why suddenly i lost 30 percent . and for example since this morning i lost only 1 % . my is at 99% now 

I've experimented exactly the same with Fenix 8 SOLAR 47 (firmware 12.35). Some days it consumes 4% and other days up to 30%, with no changes, no activities, nothing different.I've note that is the last 30% wich is consumed in only 1 day (14 days from 100% to 30% and 1 day from 30% to 0%)

Are you using any CIQ watch faces/apps?  Often they can kill battery.  If you are using one, switch to a stock watch face and see if any improvement.  Also, do you have pulse ox set to manual?

Möglicherweise läuft eine Aktivität weiter, nachdem sie sie beendet haben. Rufen sie ihre letzte Aktivität auf, starten sie diese und beenden sie diese gleich wieder, um sie endgültig zu stoppen

I'm still having the same sort of problems with v12.35. 50% in one day (with one 45min GPS activity). AOD off. No SPO2. Nothing clever turned on.
It's not really good enough. 
Need some transparency here on the issue and what's being done to fix it.

After Many months , the only solution , i have and there is no others after updating with beta and normal firware, is to restart the swatch.

It could be activities like hiit oe running or bike, the fenix 8 continue to lost battery.

It is crazy , i can not continue like this: if the product is not finish i ask to have my money back . i am not a beta tester and for this price, thegame is finish . So give me a final solution 

Same problem here. Lost 4% of battery life per day in the first week of ownership, now it can be anywhere between 5% and 40% in a single day. There seems to be no rhyme nor reason.  I'm running a 51mm with software V12.35.  This is nuts and far from what's advertised.  I suggest that Garmin get a wriggle on with a fix or this watch is going back.

I have exactly the same problem.  Fenix 8 51mm OLED running V12.35.  In my first month of ownership it used to consume c5% of the battery life each day (0430 start and 2300 finish).  Now it's somewhere between 10 and 30% daily without changing any of the settings.

This watch was the best part of £1000.  It isn't functioning as advertised and support has been distinctly lacking.  I suggest that Garmin push out a software update that resolves this in the next 28 days or my (and I suspect, many other) watch will go back.  Not fit for purpose.

I've since re-started the watch and charged it to 100%. Has stayed at 100% for 4 hours so far. Let's see if it stays 'improved'.