Terrie you have to leave the key on the towed car on so the steering does not lock up.. but if just left like that the batt will be dead after some time..
My setup is this, we got a Jeep Wrangler Unlimited that I set up with Blue Ox tow bars,, I put a batt disconnect right next to the batt so it's as simple as just turning the knob and no drain on the batt.. after doing my resurch on systems i figured I only wanted to do this one time and wanted it to be as painless after the fact as possible, so I went with the Unified brake system for a couple of reasons.. once installed it stays on the car.. nothing to move off the drivers floor or disconnect from the petal. It uses the Jeeps power brake system via a vacuum pump so its not just jamming the brakes. Only thing I need to do or undo is the big 7 way light plug from the RV to the Toad.. that's it..
With this set up the only issue I have, is I have to reset the clock and the stations on the radio each time.. And I can say the RV will stop shorter with the Jeep in tow than without it..
I did the entire install with the help of a couple of friends in one day.. if I had to do this entire setup again I would go the same rout in every way..