I have drawn up a very rough flow chart of what SHOULD happen when AC coupled and on grid. With just a pair of CT's at the grid meter, the hybrid inverter has all the information it need.
Have a configuration field for "Max grid input power while charging" "Max battery charge current" "Max grid export power while inverting" "Max battery discharge current" "Battery charge time window" "Battery discharge time window"
In the morning, the sun is not quite up yet. The battery charge window opens, but we are still pulling from the grid, so it waits. Once the sun starts making power, the grid current starts to fall. It goes below the maximum grid import current, so then the charger will start to charge and the current will adjust so we stay pulling less than the max grid current while charging. If solar power increases, it keeps raising the charge current until we reach our maximum charge rate, at which point, any less load or more solar with reduce the draw from the grid even more. This Max grid consumption could be close to zero. When the batteries become full, the charge current must stop, so it will allow the grid export current to climb as it has no way to control that.
At some point, it will reach the end of the charge window, and that will also stop charging, if the batteries did not get full.
Then the export time window begins. If the solar is pushing out past the Max grid export limit, it won't start inverting, but as the sun falls and/or load increases, then the inverter will start pushing current to try and keep the system at the max export limit. If the loads become too great, and it reaches the maximum battery discharge power, or the battery is running low, then the export current will have to drop off and you may have to start buying power again to cover the loads. If the load falls again (A/C compressor cycles off) the export current will rise again, and the inverter output will drop to keep the export at the desired power. This can also be set to zero export.
I also see allowing multiple charge and export windows, with separate current settings in each window. I do not suggest more than one charge and discharge cycle per day, but it could go to a faster charge when we know the sun is well up, or a higher export current for an hour to help run A/C but limit it later to preserve battery power.
In each time window, it should have it's own battery voltage and/or state of charge limit values. It should have a choice if you want it to charge even from a higher state of charge, rather than waiting for the low "must charge" setting like it does now.
And also add a complete separate set of charge and invert power limit setting when the system detects it is off grid, and another for on generator?
With all the hype about the increased memory and processing power, these should be easy features for them to add.
