I have two of these batteries hooked up to my 5thWheel. One battery started overheating and steaming out of one of the vents. The other battery did not heat up. What do you think the cause of that is? Thank you?

Hello, there a several reasons why your battery could've overheated. Bad terminal connection, short circuit, forced charging and heating up the battery too much. I would check the connection or take your battery to get checked out and see if there could possibly be something else going on.