Battery bug

That's about 4%/day or 25 days of battery life.  The 51mm versions will do that all day without always on display.

But not the fenix 8 AMOLED 47mm... ;-)

Well then you got a real good one.  :-)

Give it a couple of days and see what it looks like.  Might fall in line with expectations.

Steffen said:

I had a battery level of 100%, which has now jumped to 99%. That means a battery consumption of 1% within 6:30 hours.

If the fenix 8 behaves like all the Garmin watches I know so far, a change of the display from 100% to 99% does not necessarily mean that you have just used 1%. Internally, Garmin only changes the display in 0.5% increments.
So if the battery still has 99.6%, the watch still shows 100%. At 99.5% it changes to 99%.
So even if it has displayed 100% and has now jumped to 99%, it is possible that you have only used 0.1%.

The watch consumes a very small amount of power, even when it is switched off, to keep the internal watch synchronized. But this can be neglected.

But when you switch the watch on, it consumes additional power because the operating system and all data are loaded. This means that the watch certainly did not have 100.00 % after booting.

It is therefore possible that the watch would have consumed less power if you had left it switched on overnight without activating the display.

Edit : So if you have switched off the watch itself at 100.00 %, it will not have 100.00 % after the start process.

The starting process in particular consumes a lot of power. And it still shows 100% up to 99.6%.

Steffen said:

Yesterday evening I charged my fenix 8 to 100%

Are you sure it was 100.00%? Even if the battery only has 99.6%, the display is 100%.
How long did you keep the watch on the charger after it jumped from 99% to 100%? To be sure that the battery is really fully charged, you should leave the watch on the charger for at least 30 minutes longer.

Another source of error is the battery calibration. The display is not always 100% accurate. To calibrate the display, you should charge the watch to a real 100% and then discharge it completely through normal use until it switches itself off. Then charge it again to real 100%. This should calibrate the battery meter.