I did the same thing on both of our Suburbans. The sound systems, video systems, lighter sockets, and a pair of rear-facing floodlights on the back of the Sub roof for camping were connected to a second battery (deep-discharge type). In my case, there was room under the hood for the second battery.
I agree with the others that there doesn't seem to be much height available in the well. Some batteries can be mounted on their side (like Optimas) so you might think about that to reduce their height.
I used an isolater/combiner from the following place:
Isolater/CombinerThese have been very reliable and have a lot of features. They are more expensive than relays and regular diode isolaters, however.
Steve
