Hi,
I have a problem with current oscilations with my MultiPlus-II 48/5000/70-50 GX paired with a Shelly Pro 3EM-3CT63 as grid meter. As batteries I have two Pylontech US5000 in series rsulting in 10kWh capacity. Solar is ac coupled.
The Shelly Pro 3EM-3CT63 dumps its readings via Outbound websocket into the Multiplus which does work. The multiplus is configured as ESS and this works most usually.
However after big steps in energy consumption the ESS current sometimes starts to oscilate. This happened in the night with no solar power.
Is this caused by too slow readings of the Shelly energy meter?
I have to stop this, it’s burning energy, money and destroying my batteries.
The readings of the energy meter show correctly in the remote console (however they keep disappearing for a couple of days in the VRM Portal, but that’s another topic)
How does the Cerbo or Venus OS device know how to talk to the Shelly Pro 3EM over the web socket? Is this a modification you made to allow this, or is that a supported device now?
I would suspect that a delay is the culprit, what the the period of the oscillations in seconds?
That may tell you something.
Are the CTs oriented correctly?
Do you have ESS Multiphase Regulation setup for “Total of all Phases”?
No modifications, I just put the GX’s ip in the outbound websocket section in the Shelly settings.
The period time seems to be 10s. But it’s difficult to measure.
Yes, ESS works fine most of the time, when everything is steady. The battery gets charged when sun is shining and discharged in the night. Just sometimes those oscilations start.
Yes. As mentioned, when consumption or solar generation is within the limits of the Multiplus’ capabilities it manages to adjust the Total of all Phases to ~30W, which I defined as setpoint.
OK, can you watch the updates to the grid power on the console (as you did above) and guess at the update rate?
I’m seeing reports that the default for the Pro 3EM is a 15 second update rate, and the best it can do is a 2 second update rate. Even 2 seconds may not be fast enough for the ESS to track. Most energy meters give 1 Hz update. Some like the EM540/EM530 and Victron’s are up to 10 Hz.
