I had it initially setup to run on Wi-Fi too, battery or charging.
Then I had my battery drain to 30-40% during afternoons, when I’m used to reaching evenings above 60%. Check app usage on settings: Syncthing.
Since I use it mostly for backing up photos, I found it better to enable it only when charging.
Probably good to add a /s somewhere here.
I suspect people are down voting without checking the piece.
I know I would, but I saw it shared on Mastodon in a cheeky way first.