There are a lot of different types of battery isolators on the market for the off road vehicle. One thing that I have noticed is that most of these isolators contain a lot of electronics and are over complicated for the job they have to do. One thing above all when going bush is to keep it simple. My own 4wd is a 1991 Nissan Patrol and even still has ignition points. These whole car is simple so that I can carry out bush repairs if something breaks down. I have seen plenty of new 4WD stuck in the bush because the electronic ignition system went dead. The same applies to the dual battery systems, keep it simple as there is less to go wrong. Always use a system with an external relay or contactor as you can hard wire these in the case of an electronics failure.