What one should do is use a multimeter across the battery terminals. If the battery is somewhat charged it will read 12.6-7VDC
If you connect your trailer to shore power or generator this DC VOLTAGE should jump up to 13.6VDC or higher depending what charge mode your on-board converter-charger is doing at the time.
If your battery is showing a charge mode with the terminals being 13.6VDC or higher then operate your disconnect switch yo OFF. If the battery terminals is still showing the 13.6VDC or higher DC VOLTAGE then the battery is still charging. If it drops back to 12.6-7 VDC it is not charging...
This is what I would do to confirm questions like this... Every thing always seems to work a little different between the various models of RV's...
Roy Ken