I suspect I might have encountered a bug in Dynamic ESS (DESS) today, potentially related to the recent firmware update.
The Issue: According to my DESS schedule, the battery was supposed to be charging during a specific timeframe today. However, when I checked the VRM, I noticed the system was deviating significantly from the Target SOC. The charging behavior was extremely erratic, rapidly cycling on and off. Additionally, I noticed on the physical Victron display that the AC loads were dropping to 0W every few seconds.
The Data (see attached screenshot): I’ve attached a screenshot showing the log from one of my BMS’s (Total Power/W). You can clearly see three phases:
09:00 - ~12:00: A constant “sawtooth” charging pattern. (Side question: Is this sawtooth pattern normal behavior for DESS? I see this almost constantly).
~12:00 - ~13:30: The system goes completely haywire. Massive, rapid fluctuations in wattage, essentially turning charging on/off continuously.
13:30 onwards: The system normalizes after manual intervention.
The Workaround: To fix it, I toggled DESS OFF and then back ON, and briefly enabled the “Keep batteries charged” function. Immediately after doing this, the system normalized and returned to the regular (sawtooth) charging pattern.
Suspected Cause (v3.70?): I have never seen this erratic behavior before. The only recent change to my system was upgrading to firmware v3.70 yesterday. Furthermore, I know at least one other person who experienced the exact same issue today, which makes it feel like more than just a coincidence.
Has anyone else noticed this behavior since updating to v3.70? Are the developers aware of a potential DESS bug causing this?
System specs:
MultiPlus-II 48/5000 x 3 in parallel (only AC-in connected, Victron 3P75ct power meter on mains)
It only happened march 1st between approx 12:00 and 13:30 (so exact same time as TS). I rebooted my GX at some point, not sure if that fixed it.. or if it was something else (seeing it stopped at the same time).
On a Facebook group, I noticed two other people reporting the same issue. So far, the only common factor seems to be that everyone experiencing this problem is using the 3p75 energy meter on the grid.
The Facebook post suggested grid instability as the cause. However, I am located in a different region than the original poster, so that seems unlikely in my case. What is striking is that the issue started and stopped at exactly the same time for all of us.
It also happend to me again last sunday. I already suspected it to be the same issue.
I don’t use a 3p75, so thats not the cause. I don’t use DESS directly at the moment (i let it create the schedule, but have my own control logic on that).
According to my control logic I tried to charge the battery with 3000 watt, but the Multiplus 5000 had a hard time reaching the target.
My hunch is indeed that it somehow has to do with the grid.
In the screenshot you see that untill 11:00 it followed the setpoint perfectly, then untill approx 14:30 it’s batteling trying to reach it (the dip at 12:30 is me restarting the Multiplus)
You cannot do that, your system needs to be hooked up to L1. Almost every calculation / control logic is considering a single unit to be attached to L1. Attaching it to any other phase will yield wrong results and unexpected behaviour.
(If your system IS on L1, then you might have swapped phases on the meter?)
I had the Multiplus (no MultiRS) running in external control, so there is no grid feedback loop here. I just set the setpoint based on the percentage diff from the DESS schedule (which is approx 3000 watt). The Multiplus then charges with this value (i am not feeding in here), not taking grid activity into account.
The Multiplus is on L1 (as it should be). L3 was the car charging also, L2 is what is left of the 3 fase solar to actually go back to the grid.
So the situation was rather simple: ESS mode 3, charge with 3000 watt on L1… but the multiplus could not get the 3000 watt in a stable manner for a few hours.
The previous time this issue occured, it was running under DESS control, but the same erratic Multiplus behaviour occured.
Thanks @dognose for reaching out. And @dantm then, the 3p75 is not a common factor anymore indeed.
I will refrain from drawing conclusions without sufficient evidence and will stick to reporting facts only from now on. Hopefully, the Victron experts may occasionally be able to identify what is happening.
My system consists of:
3x MultiPlus-II 48/5000
No loads connected to AC-out; all loads are on AC-in (and also feed in from battery is over AC-in)
A 3P75 grid meter communicating with the Cerbo GX via LAN
4x JK-BMS Yixiang battery boxes
I previously observed this issue on Venus OS 3.70, and I am now seeing it again on 3.80~14 beta.
I have also found multiple reports of the same issue. At least one other affected user (@dantm) has reported it on this forum, and I am aware of two additional cases mentioned in a Facebook post. This therefore does not appear to be a unique situation.
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