The factory makes a pretty sweet one. They come installed in models with the aux battery under the passenger seat. It is basically a switch that shuts off the underhood battery when the vehicle is off so that you can use all you accesories off of the under seat battery and not drain your starting battery.

Where can I get more information on installing a aux battery and the isolator under the passenger seat. I did not get this installed from the factory, so now I have to make due, also looking at installing a inverter under the seat also, and the next thing would be moving the ac on the roof to the aux battery. Any comments would be greatly appreciated. Sorry for the mouth full....

Try this company: http://www.surepower.com/products.html. In essense, you can isolate, or switch, the secondary battery, but not "split" the two systems. While running, I join them through a solenoid. When stopped, I separate them. Seems to work OK.

Here is a link that will show you step by step on how to install the battery and isolator. Hope it helps.

http://www.berrysprinter.com/sprinterbattery.pdf


Steady