Well, it just means that something, somewhere, is staying on in your Taurus when towing it (with key in ACC mode), and that is draining the battery. Not uncommon at all.
Your choices to solve this go something like this:
1. Find out what is causing the drain, and turn it off when towing, if you can do so without hurting anything. Usually done by pulling a fuse or installing a switch of some kind.
2. Disconnect the battery whenever you tow.
3. Install a charge line from Motorhome to your toad, to keep battery charged.
I personally recommend option #3. Tis the easiest, simplest solution, and costs very little. I had to do that with my 2013 Ford Fusion Hybrid that we tow, and its worked great. Battery stays completely fresh and charged up when towing.
Will and Cheryl
2021 Newmar Baystar 3014 on F53 (7.3 V8) Chassis ("Brook")
2018 Jeep Wrangler JK ("Wilbur")