My offgrid farmhouse 12 V 9.6 kWh flooded lead acid battery has just died and been replaced by 2 Dumfume 12 V 300Ah (each with internal BMS) in parallel providing ~7.2 kWh, after equalising and fully charging batteries as per manufacturer’s instructions. The solar set up is 8 Trina 300 W panels charging the batteries through a Victron SmartSolar 150/100 MPPT controller with a 2 kW Girandel inverter providing 240VAC output. A 12 V marine water pump avoids requiring the inverter to run to pressurise the cold water system which feeds an unpressurised solar HWS that is also linked to a thermosyphon connection to a slow combustion wood stove.
My concern is that with intermittent occupancy and zero power useage, the batteries will be kept fully charged for the majority of the time and this may/will adversely affect battery life. While the batteries could be partially discharged and then disconnected when the farmhouse is not occupied, the pressurised cold water feed to the solar HWS needs to be maintained at all times to avoid possible overheating and damaging the HWS should eg leaks, evaporation or leaky taps reduce water levels in the HWS.
I intend to buy Victron SmartShunt and Cerbo GX to allow remote monitoring and control of the system but the local internet is unreliable, perhaps a simpler local system using a dummy 12 V load bleed could be fed from the solar controller street light function to reduce average battery voltage when farmhouse is unoccupied. Alternative suggestions welcomed.