Sorry if this is a dumb/newbee question but I need to know if the MultiPlus II units will rely (or can be programmed to rely) on PV power to the inverter if there is sufficient PV power to run the loads and then augment (or default to) the batteries when PV power is insufficient. In other words, my system design should be able to run all loads when it’s sunny and only use battery power during cloudy days and at night. If the MultiPlus II is unable to do that, is there another Victron product? This is entirely off grid. Thank you all in advance.
If the PV is going to DC then the PV power will run as hard as possible to run loads AND charge batteries simultaneously. If the PV is less than combined ac and dc loads then the batteries make up the difference. If the PV is more than the combined ac and dc loads then the surplus goes to the batteries. This is nothing to do with the inverter settings it is just how electrical systems work.
Additionally, if the PV power is higher than the combined ac and dc loads and the batteries are full, the MPPT will automatically throttle the PV power to cover just the loads and not over charge the batteries.
I haven’t yet installed the system but I’m assuming the PV is going to an MPPT 450/200 then on to the batteries. The MultiPlus II (Inverter) is going from the batteries to a 200Amp AC panel. Of course, both units will be communicating through Victron equipment. However, it’s unclear to me how the inverter can take the DC directly from the MPPT (bypassing batteries) when both units are attached to the batteries.
A Victron ESS will try to holt a defined grid set point e.g. 0W grid.
If PV > load, charge surplus to battery
If load > PV, take from battery.
It doesn’t matter if AC or DC PV or even 3rd party.
System boundaries apply, e.g if AC PV is bigger than MP2 charge capacity, surplus AC PV go to grid. If loads are bigger than AC PV + MP2 inverter, surplus is taken from the grid.
All DC units are connected by a DC bus, e.g. Lynx Distributor. Current from MPPT can go through the DC bus directly to the MP2.
I recommend DC and AC PV, e.g. RS 450/100 + Fronius 5kW
Thank you. Your penultimate sentence answered my question: “All DC units are connected by a DC bus, e.g. Lynx Distributor. Current from MPPT can go through the DC bus directly to the MP2.” The key is that the Lynx Distributor will allow DC current to go directly from the MPPT and bypass the batteries (if they are full) or allow excess to go to the batteries if needed. That is what I was missing from my analysis.