I recently installed a three phase setup with three MultiPlus-II 48/3000/35 (fw 459) with four Pylontech US3000 battery modules.
Everything works. During normal loads ESS balances the grid setpoint and optimizes for self-consumption just fine. Now I discovered an unexpected behaviour regarding what happens when one of the Multis reaches it's load limit during grid connected inverter mode while the other two are not doing much at all.
What I expected:
When one Multi reaches it's load limit additional power is taken from the grid. ESS balances to the configured grid setpoint as the other two are able to provide additional energy.
One Multi reaches it's load limit at 3000VA. Additional power is taken from the grid. The other two Multis are only providing their (very small) loads. Power is taken from the grid without balancing to the grid setpoint - energy is bought from the grid altought it could be taken from the battery.
My batteries can provide around 7000VA easily so this can not be the problem. Also the system balances out during normal operation just fine. Is this expected behaviour for ESS? If so, why? Makes no sense to me.