Y2KW57 has some serious breakers for his batteries. Check them out in his photo gallery. If I ever go the breaker/disconnect route, I will be getting what he has.

 

Breaker? No - way too much juice. Battery disconnect? Refer to any marine website and check out the electrical goodies.

 

 

Care to share with the rest of us what path you decided on?

As I mentioned earlier, the picture below is the route that Y2KW57 took with a disconnect.

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From your second post it sounds like you are looking for a circuit breaker to protect the wiring to accessories. I do have circuit breakers installed, but they are not what Sous showed my photos of. What Sous posted were photos of my manual battery quick disconnects. On the other hand, my circuit breakers look like this:



They are rated for the wire they supply power to. In this case, this particular circuit breaker is feeding power to a small accessory fuse panel I have at the rear of the vehicle.
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Uh... the battery is rated for 800 cold cranking amps, and we have two of them. Where are you planning on using that breaker?

 

 

Now see there? You led us down the garden path when you asked to fit a battery disconnect under the hood. I thought you were talking about a breaker for the truck batteries. I'm curious to see what you come up with - I've been going through my trailer wiring recently because it's electrically and mechanically shot.

 

The circuit breaker of mine seen above was something I used in lieu of a factory fuse for the factory trailer wiring harness. (Different brand of truck, but the basic principles are the same).

As we all know full and well, Ford's factory 7 way trailer wiring harness has a wire inside of it that is intended to distribute some of the engine alternator's charging benefit to the trailer batteries. For cargo trailers like mine, the main benefit is charging the emergency trailer brake battery. The wire in the factory harness is only yay big... maybe 10 GA? 12 GA? I'd look at the wiring diagram, but Ford didn't put wire gauge sizes in the wiring diagrams until after 2002, which is a different diagram than our 2000.

Anyway, the point is, since the fuse is to protect the wire from burning, and has nothing to do with the size or ampacity of the battery, I could go no higher than 40 amps on the circuit breaker, since the factory had determined that a 40 amp fuse was appropriately sized for the trailer battery charge wire they installed in the harness. In the case of this particular truck, I added an additional battery, and removed trailer battery charging duties from the starting battery, and reassigned them to the spare battery. And since this lighter truck doesn't tow as much as my 550, I wired an additional accessory fuse panel at the rear of the truck, powered by same hot lead that would otherwise be charging trailer batteries. Why waste the built in factory made functionality and copper, if no trailer is being towed? Why not use it. Hence, the circuit breaker.

Since the OP is taking it to the next level, using a thicker wire (2/0) to deliver more charging current to his trailer batteries, it stands to reason that he is using a higher amp circuit breaker, since the point is to size the fuse or the breaker for the wire carrying the current, not the capacity of the power source (battery or alternator) delivering the current. So the size of the battery (or batteries) is essentially meaningless in terms of fuse or circuit breaker selection.