Following up on my post further up this chain: I received word back from Mastervolt tech support whether it is safe to leave the boat plugged into shore support and connected to the Mastervolt smart charger. The response came both from Spain and the US: yes, no problem leaving the boat plugged in. The Spanish MV technician recommended turning off the charger once a month and putting a load on the battery (i.e. turn on some electrical loads) for 30-45 minutes and then reconnect the charger. Since the Spanish dealer has also certified the installation, I will not worry too much about running the batteries at 100%.
