[Richard and Rhonda]

Jimmy,

I don't know what the black boxes in the first photo are. The blue box in the second photo is a standard one way battery isolator used on RV's. It allows the alternator to charge the house batteries and the chassis batteries at the same time, but it does not allow current from the chassis batteries into the house system to prevent you from killing your chassis batteries while boondocking.

I have seen them wired with the positive side, but who knows.