[77newell]

If you have the batteries merged and only one is "boiling" then in all probability you got yourself a bad one. If it were mine here is what I would do; turn off the merge to isolate the chassis batteries from the coach batteries and then disconnect the ground wires from the chassis batteries to electrically isolate each of them, check the voltage across the posts, wait awhile and check the voltage again. If you have a bad one you will know. All this checking just ensures that you do indeed have a bad one, I would kick myself if I replaced an OK battery, I prefer to check prior to writing a check.