Fenix 5X Plus - only 3,5 days battery run

Try turning off Pulse Ox. It's a battery hog.

Have you done a factory reset? 

From the manual: NOTE: Turning on all-day acclimation mode decreases battery life. (Pulse Ox)

Phillip is right. Pulse Ox is a major power thief. On my watch, Pulse ox increases the battery drain by a factor of nearly 3. (At least it did on FW 5.53 and 6.51)

How do I know?

I have the complete battery usage history for my F5X+ since I got it 11 months ago. Carefully entered in a spreadsheet to calculate consumption rates both for activity mode and watch mode separately, supported by relevant data of operating mode , FW versions etc.

With my setup I get 8,5 days between each charging on average since day one, with 4,5 % of the time in Activity Mode (mostly cycling). This in turn corresponds to 13,2 days in pure watch mode or 23,6 hours in pure activity mode.

And I’m perfectly happy with that, even if it is a bit off Garmin’s “Up to” consumption figures in the manual. I could possibly tweak my setup to get more time out of the watch between chargings, but when I spend NOK 8000,- on a device like the F5X+, I prefer to use all the features it offers.

BTW, my standard setup is:

Stock analog watch face displaying HR

24/7 HR monitoring

BT always on, connected to Android phone with GCM

WIFI enabled, but only setup with my home network.

Recording it set to Smart as default, but since I have PM’s on my bikes, most activities are 1 sec.

GPS set to GPS only

I avoid CIQ apps unless I really need them. Currently Battery Gauge and Running power only installed.

Feel free to have a look at my data:

Other possible power thieves are: Backlight, BT connection to phone and GPS+Galileo.

Stig

SImilar to you Stig... I use the stock watch face + HR. GPS only though my only changes are

Leave on Pulse Ox during sleep

CIQ - one data field for ultra's (Pace Assist) but normal runs are stock only

Two CIQ widgets (UV INdex and Accuweather)

Seeing a little better than you but only within the limits of statistical noise

Thanks for materials. From my side I'll try to disable PulseOX, decrease light interval and test again.  I Will let know the results of test. 

I've turned off PulseOX. 

Without PulseOX - I've got 10% battery usage per 24 hours. 

I currently use 1.5 - 2 % per day. But I was going through about 10% a day. 

I removed all but one of the watch faces that I had downloaded (Garmin Support has told me multiple times that watch faces, widgets, etc downloaded from Garmin Connect IQ can burn power sometimes if they aren't updated when the watch's software/firmware is updated), turned Settings/Phone to "Off" , turned "Off" Activity Tracking, left Settings/Sensors & Accessories/HRM Strap in "Searching" mode, took all the widgets out of the widget loop, and left the two data fields I had downloaded from Connect IQ.  Pulse OX and Wrist HR senors are "Off".  WiFi is "Off".

It may just be that I am fortunate in that I am mainly interested in monitoring my workouts, and using the watch to navigate when hiking.