This page will teach you how to wire two batteries together without a dual battery isolator, and it will also show you how to use multiple 6 volt batteries as well.
Multiple Battery Write Up (http://rk-enterprises.home.att.net/connectingbatteries.htm)

Good info BeerBud! :thumbup

fer sher ;)

Thank you for the kind words. :cheers:

Thanks for the addition to the Tech section :thumbup

Good job beerman!! :thumbup

Good reference, cause i'm about to do that

Same here.
I am going to be running two Optima Red top batteries.

I have a yellow top now and it is a good battery but after I get the rest of my crap installed and my electric fan I will need all teh current I can ask for.

i built a tray & installed a second battery. the guy at the battery store said run pos to pos & neg to neg. the only thing that would void the warranty is if i used an isolator. AXE

good tech info :cheers:

My 78 came with the factory dual battery setup. :D
No brain, no pain.

lucky bitch

With this dual battery setup: if a winch or some other electrical device drains the first battery, will it drain the secondary also, won't it? Or will it leave the second battery safe and full?

i think it depends on how you have it wired. and if you used an isolator :shrug

When I installed the second battery I ran ground to the body and positive to the solinoid on the fender with the other battery positive cable and put a quick disconect battery post (cost about $2) if I am parked camping with lights and radio on or worried about draining both (redneck welding or winching) I just disconnect the one positve. seems to work fine so far

Running in series (pos to neg) will add together the voltage of the batteries. e.g. two 6V batts to equal 12V. Beware of running two 12V in series in a 12V system. You'll be pumping 24V through it. Running in parallel (pos to pos and neg to neg) will just give you the capacity of both batteries at their listed voltage.

With both these setups the batteries get drained at the same time. What I'm going to do in my Bronco is two batteries seperated by an isolator. One is a regular car battery. It will be responsible for starting me up and such. The other is a deep cycle marine battery. It will give me lots of time with power for all the accessories. The isolator will keep both batteries seperate and allow the alternator, which will be connected to the isolator, to charge both batteries. Now if all my accessories drain my deep cycle battery I still have a full charge on the regular battery to start me up and start charging the system again.