Battery Disconnect Switch

Marine ON-OFF switches will do what you want. Here is one rated for 450 amps continuous, 1,200 intermittent.

http://www.perko.com/catalog/battery_switches/99/heavy_duty_battery_disconnect_switch/

You didn't say whether you wanted an electrically or manually operated. Surprised that your rig is equipped with battery disconnects.
This unit from Intellitec should handle your needs.
Intellitec Big Boy
Remember that you should not be connecting or disconnecting under a heavy load. The circuit to the inverter if equipped should not be going through the disconnect.

What loads are you switching? You need to size the disconnect switch for the current the load consumes, not for the current the battery could theoretically produce. Your battery can producing a short circuit current that's a lot higher than should ever be possibly required of it. A lead-acid battery is capable of doing things like melt wrenches that are accidentally dropped across the terminals.

If you're switching the main input to your 12V distribution panel (only), you'll never be switching more than the main fuse there or, if it has no main fuse(s), the sum of the branch circuit fuses. Typically this would be on the order of 100A or so, but it could vary depending on the RV and what all devices it's equipped with and how its wired.

If you have a nontrivial inverter you're running through the disconnect switch, the current rating needs to be a lot higher.

enblethen wrote:

Remember that you should not be connecting or disconnecting under a heavy load.

Absolutely right. As near to zero as possible. But the switch must be capable of carrying the same load as the main cables.

The circuit to the inverter if equipped should not be going through the disconnect.

That last comment is confusing and, I think, wrong.
A battery disconnect switch should disconnect the batteries from EVERYTHING.....except a battery tender (solar or otherwise) that you want running all the time.

You might want to look at Flaming River products.

http://www.flamingriver.com/index.php/products/c0015?gclid=CP_2q5Dy78kCFdgHgQodztEKYA

Their larger switches can handle 2,500 amps of cranking power. We used one for over 12 years on our 2001 Winnebago Adventurer. We didn't need one with that high a power rating, but did like the mounting brackets and solid connections. They aren't cheap, but they will handle just about any load you throw at them for may years to come.

enblethen wrote:
You didn't say whether you wanted an electrically or manually operated. Surprised that your rig is equipped with battery disconnects.
This unit from Intellitec should handle your needs.
Intellitec Big Boy
Remember that you should not be connecting or disconnecting under a heavy load. The circuit to the inverter if equipped should not be going through the disconnect.

He must not have a switch(disconnect(?) otherwise he would not be asking such info/.The problem is if u don't run the inverter/converter through the disconnect your battrys will drain albeit slower they will drain

I have this exact problem,I have the 12v house shut down but the inverter/converter are direct and batterys slowly drain

Surprised your MH does not already have one.

rvten wrote:
Surprised your MH does not already have one.

lots of Diesel A do not. my 08 allegro bus does not have a manual main house battry disconnect.it has a 12V bypass but not a direct manual disconnect as what the op is asking about

Not sure if wiring diagrams are available from Fleetwood for your rig.
Get your serial number and vin number, then contact them for wiring diagrams.
I haven't seen any Fleetwood MHs without battery disconnects for the coach.

Our friends Revolution has a simple light switch next to the entrance steps for the house batteries ( I guess what you would call a salesman's switch) and a large dial switch screwed to the radiator in the engine compartment for the chassis batteries.