Hi Roger, being a simple builder all this technical talk is unfortunately above me, but do i take it that the Nasa instrument is only designed to connect to one battery. On Storm Dragon at present have a 2 battery system with 1 dedicated to the engine alone and the other runs everything else, however i am thinking of adding a 2nd battery as back up for extended cruising and longer times at anchor, but will the Nasa instrument be capable of monitoring both batteries…..Ed Holmes