Hi.
I have a 3 phase MPII setup with AC coupling (fronius symo) on AC OUT, grid feed in is allowed
I use a small battery bank (I know, but a larger bank is not economical at this point.)
I need the system to use the grid for surge loads (e.g. switching on of induction cooker ) not the batteries!
It makes much more sense to draw 3kw for 10-30s from the grid than from the battery.
If I use scheduled charge during the day with a low SOC (when I expect the batteries to be charged from AC coupled PV) the surges still are drawn from the battery if minimal SOC is below current SOC, so this is a NO GO.
If I limit the inverter power to 0 during day, it wont invert surplus PV power from e.g. L1 to L2 if there is surplus.
My current idea is to use node-red and gradualy increase minimum SOC as the battery is beeing charged, so that it is always 2-3% above current SOC, this enables maximum inverter power between L1/L2/L3, disables battery discharge and enables battery charge from surplus AC coupled PV. And is AC coupled PV is not enough to power loads, grid will be used.
Then, at night, I will drop the minimum SOC to 40% and the battery will be gradualy discharged till morning with a constant draw of 300-500w.
Any other ideas?
Thank you