http://www.amazon.com/Post-Battery-Mast ... disconnect
This is one type of battery disconnect, just make sure it is strong enough for your amp pull, you will need one for each battery so if one battery goes bad it will not damage the other.
I can agree with using more than a 2amp charger,
But to make sure you did not kill or severely age the battery you still need to:
Make sure it is properly filled with distilled water,
Take the battery out (or at least disconnect it) and charge it for a day or two,
Then once charged let it sit overnight and then test with a multimeter,
Otherwise you wont know how it will perform in a few months or when the temp drops.
My bus starts fine in the summer with a single 700cca car battery, I tested it just for fun, (1990 7.3)
I tried it again with the temp at 45 degrees and it could barely turn over the engine.