If I'm understand your question, NO. You do NOT want to run your outlet that powers your brake system off your rv. It must be powered by the toad battery.
Because of your brake a way switch. If your toad breaks a way for any reason, the brake system, powered by the toad battery will work
If you power it off the rv, if the connection is broken the break a way switch will not work cause there won't be any power.
You have to remember that even using the Direct Kit, everytime you hit your brakes, the supplemental brake system activates, and uses a bit of power from the toad's battery. A few days of driving, especially stop and go, will slowly drain your toads battery unless you drive it awhile daily.
The easiest way to keep your toad battery charged is by using a simple 12 volt battery charger.
Again, I'll direct you to the RVI2 web site, and look up their Towed Battery Charger.. When hooked up, it will charge your toad's battery while your driving. I have one on my Subi, powered via the hot wire in my Lexi's 7 wire factory tow harness.
If you don't have a harness, it's a simple matter of running a hot and negative wire from rv battery back to the rear and using a simple trailer plug to connect. Check their web site out...pics and vidios on how to hook up everything.
The 12 Volt Direct Kit will power your toad from the toad battery.
The Towed Battery Charger will charge the toad battery while your driving.
Only reason I direct you to RVI2 is that I have their stuff, it works, but its the only one I'm fimilar with.
Steve & Cheryl + Charlie & Casey, our furry kids.
2012 Forrest River Lexington 283ts
Toad, 2013 Subaru XV Crosstrek
Camping trips this year so far...8