Bubbles is correct. Unless you wired your toad with that wire nothing should happen.
I have mine hooked up to charge my car battery but I have a special monitor and charger added to my battery that stops from the toad battery from over charging.
So if you do not have the hot wire attached to your battery don't worry about it and it will NOT discharge your coach batteries.
If you want to use it you should have something like this added to your toad battery.
https://www.rvupgradestore.com/RVibr.../tbc-12014.htm
I have one from RVIBrake3 which report back to my tablet inside the motorhome.
https://rvibrake.com/products/towed-...y-charger-plus