I have a SolarEdge 6kW grid-tied inverter (SE6000HD) with an oversized 9.3kW PV array at our home with a single phase supply. I would like to add battery storage that will allow the inverter as an essential load and thus keep the existing PV generating in a powercut.
The Victron/SolarEdge details show that the MultiPlus 48V is well suited to this and how it would be done (https://www.victronenergy.com/live/venus-os:gx_solaredge). However, Factor 1.0 means that I need 6000VA (plus sufficient battery capacity, which appears to be 19.2kWh). This leads me to the MultiPlus-II 8000VA, but this is quite a step up in price from the 3000VA and 5000VA units. The cost of 2 x 3000VA units is only two-thirds of the price of 1 x 8000VA unit.
Victron's specific instructions for parallel systems makes for a more complex installation (https://www.victronenergy.com/live/ve.bus:manual_parallel_and_three_phase_systems). However, provided these are followed, is there a good reason for going for the larger single unit at much greater cost over two parallel units that fit our sizing requirements? We may add some DC PV, either now or in the future, but I don't think we would need the extra capacity of the 8000VA unit (we are restricted to 6kW export).
Beyond a simpler install, the benefits I can currently see for the 8000VA are the 6.4kW output over 4.8kW (2 x 2.4kW for the pair of 3000VA units) and the 110A battery charge current over 70A (2 x 35A). I understand the former, but don't yet know how the latter would affect us in practice.
Having a pair would allow for some flexibility/redundancy (following some reconfiguration) in the event that one of the units needed to be repaired.
Thanks in advance for any assistance.