ESS Broken (FW 3.67) on Zero FEED IN with FRONIUS GRID TIED on AC INPUT

Q&A and troubleshooting
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1

System configuration:

Two Multiplus II units in parallel

Cerbo GX (Firmware 3.67)

Fronius Primo 8.2 (Firmware 3.32.1-2) connected on AC input

DC PV: MPPT 250/100 and 150/45

Six Hubble AM2 batteries

This is a grid-tied system with an external grid meter. Loads are connected on both the AC1 input and AC1 output (critical loads).
The Hubble batteries are managed via Cloud link, with fixed limits of CVL 53.6 V and CCL 600 A.
Battery CAN communication is functioning correctly. For testing purposes, the Hubble batteries were replaced with Freedom batteries, and the issue persisted, indicating that the batteries are not the cause.

ESS is configured:
The grid setpoint is 300 W.
Zero Feed in from PV INVERTER as well as DC PV

Problem description:
The Fronius inverter consistently enters a dynamic power limit, restricting output to only 30–40% of the available PV capacity. When loads increase, the batteries begin discharging instead of PV output increasing.
The Fronius inverter refuses to raise its power output because the ESS does not increase the power limit request. Since the Fronius can only be controlled via Modbus, it does not respond otherwise.

On ESS Grid Feed in can be activated with limited lets say 300w feed in, then system start to increase DYNAMIC POWER LIMIT and the batteries start to charge and all loads is then getting fed with PV Inverter power.
Many post refer to the problem at startup that DYNAMIC POWER LIMIT is at 0w in the mornings, it is true, BUT WHY?
IF I set PV INVERTER FEED IN active and wait for a few moments and set FEED IN to NO then system works correctly for a few minutes BUT WHY? (Izak Burger (Victron Staff) also mention this from previous posts), But this cant be a solution to the problem.

This is not an off-grid system, so frequency-related explanations can be disregarded.

Question:
After Venus OS version 3.60, has there been a change that affects ESS behavior, or is this a known bug?

I would appreciate input from someone with more experience, as this is an interesting and unexpected issue and I Believe a lot of installers have the same problem with the current firmware!

2

I will post pictures to make it easier to understand

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3

Have you stepped through the config guide to be sure something is not set incorrectly in the fronius?

4

First of all thank you for the quick reply.

Yes, checked 3 times.

Limiting is partially working, If I set ESS system to do GRID FEED IN AC INVERTER ONLY and limit to 300w, the system is more or less working much better, but still not as advertise. The point is the ZERO FEED IN use to work much better on OS firmware 3.57. The DYNAMIC POWER LIMIT was not that aggressive.

5

I can’t find a record of 3.57, only 3.55.
3.60 provided sunspec (zero feed in) support for other PV inverters beyond Fronius.
The rest of the releases were minor fixes that didn’t affect your scenario.

This is a widely deployed config, we would certainly know about any bugs that were common place.

It is not easy to try diagnose this remotely. Typically there is something missed in the configuration somewhere.

Sorry, can’t be more helpful.
Maybe someone else can chime in.

6

Thank you so far.

It still remains that PV inverters is getting Dynamically Throttled with 40 to 50 present (in efficient) while pv energy is available, in stead it will discharge battery, to supply loads.

Very interesting.

I am happy to share login details, maybe me and 3 other installers did miss something.