The wiring diagrams show a few different ways to run dual batteries you can use a Isolator, a Solenoid, or a combination of the two:

1)Using a isolator which is maintenance free but does not allow you to tie the batts togther in case of a emergency.  If you plan on using a isolator get one rated for 20 amps more than max alternator output. The isolator will equally charge both batts all of the time. Isolators are large diodes so you will have some voltage drop across them



2)Using a solenoid, which is the most flexible, allowing charging of the main batt only, charging both batts, and connecting both batts using the aux batt for power when the main is dead.The downside of using a solenoid by itself is thet both batts must be the same type so they have equial charge rates and wont draw current from one another. Solenoids need to be rated for continuous duty around 300 amps with a 600 amp surge capacity.





3))If you are already using a isolator in you system you should consider adding a solenoid into the system between the batt positive terminals.  It will allow you to connect them in emergency situations or when drawing high amps.



If you want to run dual batts on dual alternators for seprate charging systems, first find a suitable mounting place for the aux. alternator.  A few guys on the board have had success using the air pump brackets.Wiring is fairly easy and I suggest using chrysler parts this way you will have spares with you if needed.



Here is a good source for electrical componets
http://www.wranglernw.com