Is there a way to retrieve data after battery dies?

This was originally posted in the German language forum, which might explain why zero responses. The 935 English forum was archived, so moved it here. 

If the battery died and the recording ceased, there is nothing that can be done. Is the data at least partially synced with Garmin Connect Web? Are you seeing it on your watch?

plug it in to a computer device that runs garmin express app and synch it there. depending when it died and when it was last synched you may get more data into your garmin connect. 

From what I've seen elsewhere on the internet (and from my vague recollection when my battery died once during a super cold run), if your battery dies during an activity, then the activity may be automatically saved at that point.

If that happened, but no activity synced to Connect (or is visible in the watch's history), then it's *possible* that an activity file was saved, but in a corrupt/damaged form.

- Plug your Garmin into a computer using the USB cable (your garmin will appear as a drive in File Explorer or Finder)

- navigate to the \GARMIN\ACTIVITY (or ACTIVITIES) folder

- look for a FIT file matching the date and time of your activity

- if found, copy the FIT file to your computer

- open the Garmin Connect website

- click on the upload / cloud icon in the upper right hand corner and select Import Data

- select the FIT file

If you get an error message about the file being corrupt:

- you can try fixing the file at https://www.fitfiletools.com/ using the corrupt time fixer

or

- you could try fixing the file with https://www.fitedit.io/ (works with Windows and Mac)

or

- you could try posting a request to fix the FIT file here or in the forum for the Connect website (https://forums.garmin.com/apps-software/mobile-apps-web/f/garmin-connect-web) (some people on the forums have access to FIT File Repair Tool, which isn't free, but is probably the most powerful and comprehensive tool for repairing FIT files)