Should be no reason to disconnect the Jeep battery. Plus, some aux. braking systems need power to work. Just run a good heavy gauge wire from the MH battery to the 7-way plug.
Ken from Telford,Pa
2013 4-Door Wrangler Sahara Bright White- Stock
2012 2-door Wrangler Sport S-"Dozer Clear Coat" w/ manual- Stock- Sold 3/2013
2005 Liberty w/ 2.8 Diesel-50K miles- Sold 2/2012
1998 Wrangler w/ 4.0 manual trans-89K miles- Stock