I'm open to other options... For $$ reasons, just not wanting to replace the National Luna setup.
I'm not sure it would keep the main battery above 13.1 volts to keep the solenoid engaged, especially since the house battery is the one with constant loads. I'm only guessing but once say everything is charged the starting battery would fall below 13.1v and the solenoid disconnects, the house will begin to draw down and with the starting battery fully charged it wouldn't be reengage the solenoid to get the house battery charged back up or topped off. Thoughts?
I should add that both batteries aren't the same. One's a 31 and the other is a 34.