It would work but it wouldn't serve as a backup battery. Both batteries would charge together and both would drain together. The isolator allows your alternator to keep the backup battery charged but does not allow your electrical system to drain it. When/if you need the backup battery power, you flip a switch and it is available. I used the Hell Roaring solid state isolator http://www.hellroaring.comdanny_carbone said:great information guys,i also have an 07 Av and been thinking of hooking up a secondary battery ,lets say if i didn't go with any of the products you mentioned,lets just hypothetically say if i just hooked up red to red and black to black from the primary and snake it along the firewall to the side of the fender to the secondary battery,what would happen?1st would that work??2nd would i over load the alternator(over working from charging 2 battery)2nd would it really work and charge the secondary battery??