Hi,
I use mode 3 ESS using a script on the Cerbo. This basically works fine.
My main reason for this mode is that when power demands are low, I move them to a single phase to for example have 1 multiplus doing 400W at 90+% efficiency rather than have 3 multiplusses doing 133W each at 70+% efficiency. Plus some other tricks and nice-to-haves.
However, I run into one quirk:
Suppose my BMS reports a max charging current of 85A, or roughly 4300W from the AC side.
At this point, the Multiplus limits each phase to at most 1/3 of this. Meaning, if I set:
/Hub4/L1/AcPowerSetpoint = 4300
/Hub4/L2/AcPowerSetpoint = 0
/Hub4/L3/AcPowerSetpoint = 0
L1 will not charge at any more than 1433 W and my battery only gets ~28A.
If I set all 3 phases to 1433W, I get the full 3x1433=4300W charging.
I have confirmed this by experimenting with different max charging current settings, it always limits me to 1/3rd of the allowed charging currents, but without considering the other 2 phases which could be 0.
I get that the ESS assistant respects max charge limits, but it would add a lot of flexibility if it would restrict phases proportionally to their setpoint rather than a hard fixed limit.
Another common example of this issue is people charging their battery from the grid but needing to respect the main breaker sizes, for example 20A per phase, so if a load in the house is already using 12A on L1 and another is using 4A on L2 and 1A on L3, the ESS controller script could ask for 8A-16A-19A, dynamically updated to account for loads, which will not work if the battery reports less than 60A(AC) as a charging limit since there will be a hard cap on each phase in that case.
A possible non-intrusive solution would be a new configuration key that determines the method of restriction, with the default being the current approach of a fixed cap per phase, with another option being a proportional reduction of each phase, or a reduction of the highest phase, etc.
Assuming this is however the intended behavior, what is the best way to determine what limit is currently active for each phase, so that I can account for it? The 'Ac/ActiveIn/L1/P` shows the actual inverter power which can also just be slowly ramping so is difficult to use as a limit indicator.
Thank you,
Dennis
