Two full sized battery's give you more than the cool points.
To run things as winches extra off road lighting and such you need the amps to do so.
By running two full sized battery's that are isolated with a one way isolator all electronics in the vehicle are protected from massive power drain and low voltage during hard use. Plus the main fact that your primary battery is always fully charged for starting and standard vehicle requirements.
Christine_208 your hand held battery pack and solar packs are fine for light duty occasional use but not for what he is trying to achieve..
Not saying that they are not good in a emergency for a jump start in the out back when your by yourself. But they are like having a battery run drill on a rooftop fine as long as it's charged up. But you might as well have a rock in hand when it's not charged and I haven't seen too many current bushes in the boonies to recharge off of.

 

This thread from expeditionportal is what I'm going to use to build the isolator. I'll be using the high amp constant duty solenoid he talks about later in the thread, also, all my wiring will be 1/0, so plenty of current capacity.

 

For those of you that have never hooked up a dual isolated system it's pretty easy.
Just remember that the leads always hook up positive to positive and negative to negative, Positive to negative gives you 24 volts
To those that read my post before edit sorry I was over thinking it.

 

cleburne red
You posted while I was typing,
I would switch the isolator with it's own separate switch so during heavy voltage draw you can totally isolate the two battery's from each other.
. And yes a heavy duty solenoid will be advised for any long term voltage swap rather than like a ford starting solenoid.
His point of two fuses is something that I never thot of but it is a good way to protect the system.

 

I put a second battery mounted in the toolbox of my old Toyota once... Offroad lights, stereo system, and was soon to have a winch. That second battery never ended up making a difference to my setup, and in the end I pulled the battery out and gave it to my dad for his 69 Nova :P

For what it's worth, the single deep cycle yellow top Optima that I have installed in my Blazer along with a 150 amp alternator is handling my 800 watt stereo, 52" and 24" LED light bar, and 8k lb winch just fine. And even let the wife and I run a 1200 watt inverter when we lost power for a few days due to Florida's lovely hurricane season a couple years back.

 

I was wondering just that... Wouldn't you have too upgrade too a more powerful alternator? This is a very interesting thread by the way...

 

I don't think you would necessarily have to upgrade the alt, but with the additional electrical loads, it might put more strain on it.

Although, whether there are two batteries or just one, the load is the same. So once both batteries were fully charged, would it really make a difference? Hmmm

Either way, I've been kinda thinking about upgrading the alt, anyway. Probably wait till the one I have craps the bed, then get a higher amp one
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I got a friend who is into all the "off road lights" thing and he said he could not actually turn all of them on at the same time with his current alternator... He bought a much bigger, powerful 1 if you will so he could "light it up lol"