I have a grid-tie PV inverter, and an on-grid connected ESS setup. Right now my PV is parallel with the AC-In of my Multi, not the AC-Out, meaning it will not work in a blackout, which I would like to fix.
Typically, due to a number of reasons I won't go into detail, when operating on-grid using ESS, my battery SOC is kept at 100% during the daytime, until 2:00PM, at which point they discharge in tandem with the solar, selling back as much energy as possible.
When I say 100% SOC, that is my self-imposed limit, meaning my actual Lithium battery can charge up to 29.4V. My Multiplus is configured with an absorption voltage of 28.6 to extend the lifespan.
Battery is not connected using CANbus or other communication with the MultiPlus, it has its own internal BMS that can control the charge/discharge switch.
I am interested in knowing what will happen in this scenario: It is 12PM noon, the sun is the highest, and my PV interver is outputting its maximum. AC load is nearly 0, as nobody is home typically during the week, so all of that is going back to the grid. The grid fails, and all of that energy instead of going to the grid, then gets dumped into the batteries (this would be after I move the inverter to the AC-Out obviously). The batteries had already been at, what the MultiPlus thinks is 100% soc, and is at the maximum absorb voltage of 28.6, which, when 10Kw is dumped in, obviously starts to spike a bit.. Let's assume the PV inverter power isn't enough to make it rise above 29.4 when the BMS would step in the sever the connection, but does rise about 28.6V which is the maximum absorb voltage.. Will my MultiPlus trip in a DC over-voltage alarm? Or will it allow the energy to flow into the battery, raising the voltage above 28.6 for a short time until frequency shifting steps in?
