Big problems with SMA Feed-in limiting and SMA Home Manager.
Despite the warning in the PV Inverter menu, I decided to test the new feed-in limiting feature in my system with SMA SunnyBoy and SMA Home Manager 2.0 installed.
This was definitely a bad idea!
I got lots of event messages in the event log of the SunnyBoy, telling that active power limit had changed, every few seconds. I ignored the issue for about 24 hours and ended up with a PV inverter that is completely refusing any further parameter changes whatsoever.
I am not able to change ANY parameter of the PV Inverter, and there’s a lot of them!
Even if I try to reset the event log, I get an Event Number 10120 logged, with the Info that “The current number of parameter changes has been exceeded”.
So: Don’t try this at home!
Currently I am in contact with SMA Installer Support, to get the issue fixed. No solution so far.
“Curiosity killed the cat”…
Follow-up:
SMA support reported that Modbus items, which are marked with an exclamation mark in the SMA Sunspec specification, must not be used for cyclic writing. Otherwise the flash memory of the device may break. Obviously this cyclic writing must have been happening, either by the Venus OS side or by the Home Manager side.
They recommended to disable modbus communication and then restart the device.
After doing so, I was able tor change ONE single parameter of the device via the web interface. A second try was rejected again with the same 10120 event.
I am trying to get more info from SMA support on the reasons of this strange behaviour.
Hi @Baloo , do you have a link to a copy of the documentation with the exclamation marks? As far as I can determine, this is not a sunspec limitation, but rather something specific to how SMA implemented it. I’d like to be sure.
Hi Izak,
SMA support gave me two links. The first one is regarding the sunspec implementation of SMA, and the second one is a zip container with all modbus items listed in HTML format. The second one contains the exclamation marks.
Here are the links:
https://files.sma.de/downloads/PARAMETER-HTML_SBxx-1AV-41-GG10_V16.zip
Follow-Up:
SMA support replied, that my case would be forwarded to the developer department. I hope that they can find a solution or at least an explanation for this strange behaviour.
They told me to be patient, because currently there would be many support cases pending.
I keep you informed.
Thank you for that. This is the important bit:
WMaxLimPct can be written cyclically, but it seems the other registers cannot. So it is complaining about our repeated writing of WMaxLimPct_RvrtTms (timeout for the power limit), and WMaxLim_Ena (which enables the limiter). This helps, thanks a lot.
@Baloo, first I would like to apologise for this. This is not a limitation I’ve seen with any other manufacturer.
From my research, it also seems that changing parameters will become possible again, after some time has passed. Forum posts suggests that it backs off within a few days. From what you reported, it seems one parameter change per day is allowed.
They clearly implemented a rate limiter, that allows a limited number of parameter changes within a certain time period.
I am working on a solution that will only write WMaxLimPct. This means the other parameters (enabling the limiter, and setting the timeout) will have to be done manually, once during commissioning. Do you know if this is possible, and which values to set?
@iburger , no need to apologize! It was my own decision to disregard your warning, so it was solely my own fault.
I am really very pleased with the great job you and your colleagues at Victron are doing, and I am looking forward to all the new stuff that you will be coming up with.
As to the timeout, I’m afraid I cannot help you there, but the limiter might be enabled at this item:
PCC.WMaxMod can be set to “off”, “Fixed specification in percentages”, or “Fixed specification in Watt”.
But I am not at all sure about that!
I believe that you may find more infos in the specs of the “Home Manager 2.0”, which is able to limit grid feed-in via Modbus, and which I was using to do so.
Regarding the rate limiter: I myself thought it would be something like that, but it seems to be not so easy. I changed one parameter yesterday, but today could still not change another one.
I hope that I will get more info from SMA customer service, as time passes.
I have a solution already that should address this issue. For the benefit of all our readers, I will just explain the differences between the platforms.
For Fronius, I must write both the power limit value (called WMaxLimPct in SunSpec parlance), and I must also write the enable flag (WMaxLimPctEna in Sunspec parlance) on every update. I don’t have to cyclically write the reversion timeout (WMaxLimPctRvrtTms) though. So for Fronius, and also ABB/Fimer, I have to keep writing multiple registers, otherwise it will stop working.
With SMA, I am not allowed to write anything except WMaxLimPct. So I have to rely on WMaxLimPctEna and WMaxLimPctRvrtTms being correctly set on the inverter already.
I can write those values once, so that the device “auto-configures”, which is nice, but because it seems you are only allowed one parameter change per day, I think it is best to leave this up to commissioning by the installer and rather not use any of the parameter-writing budget at all.
The change in implementation will do this: It will check that WMaxLimPctEna is already set (I don’t know what the SMA parameter is that corresponds with that). If it is set, the limiter will be available, and if enabled, it will only cyclically write WMaxLimPct.
I would however like to write come kind of documentation for what is needed for SMA, and that is where the difficulty comes in. I need to know which parameters to set, so that it can be modbus controlled in the suggested manner.
I’ve watched some videos by SMA technicians where they explain how to set it up for external control, via modbus. From those, it seems this plan will work.
Maybe the solution is to put this into a beta release, and let people test it.
This morning I tried again to change a single parameter of the SMA inverter via the web interface.
The inverter keeps rejecting it.
Modbus ist still deactivated.
2 Days have passed now since I was allowed to make the last change.
So the allowed timeout between 2 parameter changes is definitely longer than one day now!
I can remember that I was able to change several parameters within a few minutes, when I was installing the SMA inverter some two years ago, to set it up for normal operation.
The behaviour now is very different.
So: Beta testers, please be careful!
Still waiting for an answer from SMA support.
Hi @Baloo ,
On other forums, I saw that the restrictions seems to let off after 5 days. I hope you’ve had success in the mean time.
I looked into this a bit further. The Sunspec documentation, in the chapter about immediate controls, states:
Each of the immediate control functions, except connect/disconnect, has an associated enable (Ena) register. Each time a control value is changed, the associated enable register must be written with the ENABLED value (1).
You have to write both registers on each update. SMA however does not allow writing the Ena register and is therefore technically not fully Sunspec compliant. A workaround will be in the next beta.
@iburger I am getting a bit worried about my SMA Inverter (running without SMA Home-Manager).
I see info messages in the SMA log, like
11/29/2024 4:31:47 PM STP 20000TL-30 481 Dynamic settings established
Before v3.60, these messages did come once per day, normally at sunrise when the solar intake was enough to start PV production.
Sine v3.60, I see these coming every 5 seconds !!! - regardless if Feed-In limiting is switched on or off.
Please immediately disable the power limiting option. You can find that here (this is a screenshot of a development version, it won’t look exactly like this):
Thanks for the fast response, @iburger
I already did disable the limiting function (without reboot) , but the log messages kept coming still and now reverted back to 3.52 (with reboot, naturally) and they have stopped.
Will you be working on a fix or is this a dead end, with the SMA sunspec implementation?
Edit: moved to v3.60~9 … PV-Inverter setting shows as being capable of limiting (so modbus-tcp comms is enabled)
Should I dare to enable it?
Follow-Up:
Today I was able to change another parameter. Did not dare to try one more. 
Still no response from SMA support.
Did the messages in the SMA log at least stop? That’s the first important question. I don’t know exactly what that message means and when SMA will log it, but 5 seconds is exactly the update rate of the power limiter, so seeing it every 5 seconds means a limit was being written.
I would say it is safe to try enabling it, in fact it would help me a lot if it can be tested. But if you see any adverse effects please disable it again and also let me know.
If you know how to access the dbus-fronius log on the GX (it is in /data/log/dbus-fronius/current), it should also show something like this:
info Using SMA profile 1.1 limiter
That indicates that it has detected that the inverter is SMA, and is using the alternate limiter code that writes only the one allowed register.
Yes, they did stop after a reboot and did not reappear after installation of v3.60~9, regardless if limiting has been enabled or disabled in the PV-Inverter settings (also setting/enabling a grid-feed-in limit in ESS setting has no effect, regarding the message). However, the message appears once a day, after sunrise (when PV-Production starts, which is normal).
This is an Info message in the inverter log, not of type warning, failure or error.
Edit: OK, I talked too soon…the message is back in 5secs intervall (the PV-Inverter log, I have access to in the SMA cloud, is lacking behind approx 2hrs.) As it seems, the messages appear as soon as the limiting feature gets enabled in PV Inverter settings on the GX
It is not in the “current” file, but as it seems in an older one…that message seems to appear only after reboot, and only once, regardless if limit settings have been altered.
Also, in mqtt, the Info regarding “LimiterModel” is not set:
I am willing to test, but Solar intake is so low atm…would it make sense to set the limit in ESS to something like 500W?
Edit2: when activating the limiter in PV-Inverter settings, the PowerLimit value in mqtt changes from “null” to “20000.0”, which is the MaxPower of that inverter, regardless if grid-feed-in limit in ESS is activated and set to something lower that 20000W.
Thanks for reporting that. That is a small bug. It does not affect operation, it just fails to report the information model’s number.
It is normal for the PowerLimit to change to the maximum. That indicates that limiting is supported. It will always initialise to the maximum power.
If it shows null (invalid), it means limiting is not supported. The power limiter (which is implemented elsewhere) will not write this path if it is invalid. So far everything looks correct to me.
I assume power limiting actually works, since you were concerned about setting a limit on a bad solar day as you have today?
I double-checked the code again, I have the correct offsets. If limiting works, then I must have the correct offset.
I’m beginning to get the idea SMA logs that informational message even if I write a register that is allowed to be cyclically written. Their documentation is also not clear whether this is something to be concerned about, or not.
Would you like me to log into your system to inspect the network traffic itself, to be 100% certain?
I actually haven’t tested it yet. normally I’d set the grid-feed-in limit to 70% of installed PV kWp, in my case that limit is 13.9kW.
With limiting enabled, the value is driven by the number of PV excess (grid-feed-in limit), which is after direct self consumption and charges to the battery. At least I would have to disable the battery charger, set the grid-feed-in limit to something like 500W and then wait for a moment where there is some PV excess (my home baseload is around 400W), i.e. 1200W of PV and check that the expected limit of the PV inverter will change to 900W (direct load + allowed feed-in) at that moment. (unfortunately, the last days PV intake seldomly reached over 1kWp for longer than a minute.
Yes, of course - if this is of help. Do I need to enable remote access in the GX for this? Then let me know.
Hi guys,
Please allow me to ask a question to Izak @iburger that could be a tad off-topic.
Is there any similar situation with the Victron products?
In other words, are there any settings that if cyclically/periodically written could lead to a premature failure of the product?
Thank you in advance!