I came up against the commonly reported problem when updating maps to 2024.20 that I didn't have enough space. I contacted Garmin support in line with the guidance in Garmin Express. The support person initially suggested that I buy an SD card with the maps on it. Of course the Edge 840 doesn't have a slot for an SD card. She then suggested that I delete the img files for the regions that I don't need. I said that I only need a part of Europe so the SD card seemed like overkill. She then sent me a link to a web page about deleting img files. However, the page wasn't about Edge devices, and she didn't tell me which img files to delete. I found some guidance online but it wasn't enough and the result was a mess.
I rescued my device by putting all of the deleted files back into the Garmin folder and then doing the updates the proper way, as follows:
1. Connect the Edge to Garmin Express.
2. Click on Manage Maps.
3. Deselect the regions that you do not need on the device (for me, it was a case of deleting North America, and deleting all of Europe apart from Western Europe).
4. Confirm the selection (I think this is when the unwanted img files are deleted0.
5. Go back into Manage Maps and tick the Update box which applies to your selected region(s).
6. Update.
The Basemap and Trailforks map required separate update processes.
I followed this procedure on my son's device and it worked fine, all done in well under an hour compared with many hours spent wrecking my own device and then rescuing it.
I hope this is useful.
