I guess I need to be more specific for some people. When I said fully automatic, I was refferring to turning on and of the correct sources, and loads, not the funnction of the charger and it's accessories to make it perform.

Which battery bank gets charged is a function of the charger itself, boiling of the batteries in normal situations is a function of the charger, it's application, and maintenance. Obviously the heat sensor will only detect heat if the entire battery gets hot, or the area where the sensor is located.

It sounds like Robby inadvertantly had an input line connected to an output line, a problem not to difficult to make automatic, so switching sources seemless.