In this system the MultiPlus is the battery monitor.
If we set min SOC 5% everything is fine. Multi stops discharging the battery at 5% SOC.
Question:
If we set the SOC 0% the Multi continues discharging the battery.
Is this a normal behaviour?
asked
ESS min. SOC reached but discharging continues
ESS does not work when you set it to 100% (the algo has a hysteresis, both positive and negative, around the minimum set SOC for ESS to work).
Because you can't get more than 100% SOC nor less than 0%, ESS logic will not work right at those extreme opposite ends.
I would also add here the ve bus SOC is not the best way to determine SOC is has no way of knowing the current moving and is likely not accurate. So it will be using voltage all the way down to the c rating cut off set in the ESS assistant.
Use a BMV for SOC.
Maybe a dumb question, but why on earth one would want to discharge a battery to 0% SOC?
Now onto your question, the logic inside ESS is based on 5% increments and decrements.
No, it's not normal behavior and maybe somewhere, in programming, a check is missing for these (almost nonexistent) cases below 5% SOC.
Afaik, if you set SoC to 0%, the system will keep discharging until stopped by the BMS, or until the low voltage threshold is met. Which makes sense in a few situations.
I've set my systems' SoC to 0% a few times on purpose, to bring the batteries all the way down, in order for their BMSs to properly calibrate at the bottom. It turned out that they were hiding around 10% of capacity.
Generally how it works. It is how they get to their warranty periods with consistent use. If you dip into that with any regularity you will regret it later.
I wouldn't say hiding the capacity. Basically to guarantee a certain useable capacity for a period of time, the bank is oversized to allow degradation and still keep the advertised capacity.
Thank you for all the comments.
Of course discharing (until it the cut off voltage of the battery is reached) to SOC 0% is risky. It was just a question to understand the system better.
I agree a BMV is a much better measurement than the internal Battery Monitor of the Multis.
So there is no ESS regulation at the SOC limits (0% and 100%).
