Still no Body Battery with Fenix 6X

The other thread was closed but the problem persists.After more than 7 days and the sleep index monitor still does not generate a Body Battery value. Only after I put on my Fenix 6X in the morning a number is shown (but the night remains blank). However, stress and HRV and sleep are well recorded by the monitor during the night. The workaround proposed by Garmin (see below) does not work.

If this will not be resolved I due course I will send the monitor back because it just doesn't work as advertised.

Please fix it Garmin.

"

Hello!

We have made improvements to this interaction in the 12.70 software update for users who have fenix 8 Series, Forerunner 570/970, Vivoactive 6, and Venu X1.

Users who have an older device may need to use the following workaround to eliminate the possibility of false on-wrist detection by their paired wearable.

Ensure Garmin Connect mobile app is open and running on the phone.
Verify the watch synced in the last 5 minutes. You may need to go to More > Garmin Devices > Device Name to manually sync.
Put on Index Sleep Monitor and verify that it vibrates indicating it has connected and is recording heart rate.
Remove watch from their wrist and power off.
Go to sleep.
Upon waking, remove ISM and turn it inside out, OHR facing up.
Verify that the Index Sleep Monitor is syncing to the Garmin Connect mobile app.
Power on watch and put on wrist.
Verify that watch syncs. The 2 devices may need to sync multiple times for a full True Up of all data.
If you experience this issue after updating your watch to 12.70 please create a new thread.

  • AFAIK the Fenix 6 does not support Body Battery TrueUp, and that is required for it to gather Body Battery data from other devices.

  • That would explain everything. But then Garmin should state that the sleep monitor is not compatible with the Fenix 6X and older. I'll send it back then unless Garmin-Tracy offers a solution.

  • I just found this in Garmin support. So basically it will only work with very new models. What a shame. Also, they should clearly have this compatibility list in technical data of the sleep monitor. There it is stated that the sleep monitor does Body Battery. Very misleading.

    Which Watch Models Keep Body Battery Data in Sync? 
    Body Battery TrueUp keeps your Body Battery data in sync across multiple Garmin products. For example, the Index Sleep Monitor syncs your sleep data with your Garmin Connect account, which then shares this data with your watch. TrueUp utilizes this information to maintain accurate Body Battery readings. See the compatible list below for this feature.


    Compatible Watch List
    Enduro 3

    fēnix® 8 - AMOLED Edition | fēnix® 8 - Solar Edition

    fēnix® E

    Forerunner® 165 | Forerunner® 165 Music

    Forerunner® 255 | Forerunner® 255S | Forerunner® 255 Music | Forerunner® 255S Music

    Forerunner® 265 | Forerunner® 265S 

    Forerunner® 570 - 42mm | Forerunner® 570  - 47mm

    Forerunner® 955 | Forerunner® 955 Solar

    Forerunner® 965

    Forerunner® 970

    Lily® 2 | Lily® 2 Classic

    Lily® 2 Active

    tactix® 8 - AMOLED | tactix® 8 - Solar

    Venu® 3 | Venu® 3S

    Venu® X1

    vívosmart® 5

    vívoactive® 6

    You can still use a non-listed Garmin watch to update your Body Battery in Garmin Connect, and that data will sync with any compatible watches you own. However, Body Battery data from a compatible watch will not transfer to a non-compatible device.

  • I just followed the exact workaround given, with the ISM updated to 2.70 and the Garmin Index Solar watch. 

    Results are the same as before the software update:

    After donning ISM and removing the watch, live HR disappears from the app. 
    After powering off the watch, the Connect app starts showing live HR from ISM.
    While wearing ISM, the app records stress when synced, but not body battery. 
    Upon removing ISM and powering on and wearing the watch, the app starts displaying a body battery trace, starting when I put the watch on. 

    There is never any body battery recorded for the time wearing only the ISM, even after syncing both devices five or more times each.

  • I have the same behaviour on Venu 2 Plus.

  • Again, if your watch is not on the list of compatible devices (see above) it wont work.

    I`ll send my sleep monitor back.

  • Hello Everyone!

    When you are missing body battery data from the Index Sleep Monitor, are you missing it from the Garmin Connect App? Another paired device? or both?

    If you are not seeing Body Battery data from your Index Sleep Monitor in the Garmin Connect App, May we review your Garmin Connect Data? Can you specify dates for which this is the case? We have an active support ticket continuing to research this behavior and I would like to get you added to it.

    If you are seeing Body Battery in the app, but not on your device, is the device on this list? Which Watch Models Keep Body Battery Data in Sync?  Devices not on this list are not capable of syncing body battery from the Garmin Connect App via True Up. May we review your Garmin Connect Data? Can you specify dates for which this is the case?

  • I've got a Instinct 2X and the ISM since yesterday. Interestingly the Body Battery data is synched from the ISM to the watch and the graph is displayed on my watch. But the graph over night is missing in the Garmin connect app. Same issue with the training readiness. It is displayed on the watch but missing on the app. Date is from 26.08.2025 to 27.08.2025 over night and yes, you may review my data.