Dual battery bed mount advice?

I want a dual battery setup, but I've already got my on board air under the hood so there's very little room under there.. I've also got a big marine battery sitting in my garage.
Rather than relocate the compressor - huge PITA-

My idea is to run some big welding cables or wire to the bed somehow, & make some kind of quick disconnect so that I can mount it back there when I go out & leave it and the extra 30 lbs at home when I'm not camping.

Questions/ concerns:
Anyone know what gauge wire ill need to do this?
When I wire up a winch down the road, am I going to light my shit up with such a long wiring run?
Anyone know where to buy cables/ a quick connect setup for this?
Will I need to wire in a breaker or cutoff switch for this? If so, any recommendations?

Thanks in advance guys!

 

Crickets bump chirp
Chirp

 

Have you tried doing a search yet (of this forum)?

 

I've done a search and have the tray for group 27 but am having trouble figuring out how to mount it

 

Anyone know what gauge wire ill need to do this? Depends on how long the wire is, but I would suggest 0 or 00 gauge.
When I wire up a winch down the road, am I going to light my shit up with such a long wiring run? If you use too small a gauge, you will risk melting a wire.
Anyone know where to buy cables/ a quick connect setup for this? I would suggest buying bulk wire and make your own terminal ends (solder them!)
Will I need to wire in a breaker or cutoff switch for this? If so, any recommendations? I would get a battery isolator, and a battery cutoff switch. The isolator will, depending on how you have the second battery connected, will allow the second battery to always stay charged. This way if you accidentally leave your key on, or headlights, you can turn a switch on the isolator and jump start yourself. The cutoff switch of course will be located on the positive cable between the isolator and the second battery, so that you can disconnect and then remove the second battery as needed.

 

What's the difference between an isolates and a cutoff switch? Does this make the power go one way (only charge) unless I click it?
& not sure where to buy a breaker that will break at 300+ amps... I know many winches pull more than this much power, making fuses etc basically useless...

Yes but I haven't found anyone that has done it Like I'm planning- to be more clear, I want to wire in leads from the main battery back into the bed Into two flush mounted quick disconnect plugs like you would find in a welder



Then I'll make a battery tray in the bed and bam dual battery when I need it, and no need to get an expensive compact one that'll fit under the hood

 

Just an idea to add to your setup:

In the past I ran an isolator but the voltage drop was too high to keep the aux battery charged in my particular case. This was in an 18 wheeler w/ 3 stock batts. I added a 4th as a deep cycle, fused it at the + terminal on BOTH batteries (since even if one fuse blows a short can still be completed by the other battery resulting in a car-beque). I was running multiple inverters rated from 1k-2k watts continuous, and always had things running like a small fridge, computers, and a home theater system for my audio...and the killer was when I fired up the microwave or shop vac. I removed the isolator and the truck was able to keep aux battery charged. The downside to this is that there is nothing to prevent a high load on the aux batt to deplete the ones the rest of the truck needed to start.

The idea I wanted to air is what I did to a passenger car dual-batt setup: Instead of an isolator, I ran a constant-duty solenoid (was about $15 from a local parts store - make sure it's constant duty (100% duty cycle)...a standard ford starter solenoid isn't rated to be left energized all the time), which I controlled via an in-dash toggle to manually isolate the positive terminals as needed.

The solenoid method also gives you the ability to jump-start yourself by flipping a switch if you leave your headlights on or something and drain the under-hood battery (assuming you turned the solenoid off when parked...just flip it on and turn the key).