Hi Bart Champagne,
I understand well what you say. Okay - it’s an idea to check the switching process in an acceptable time with a suitable adaption of the thresholds. We can do this tomorrow.
The problem with a dark time recovery I know well - in a pure island grid it is uncomfortable… - in our case, we can connect the Tanzanian grid directly (if it’s available …) und getting power via AC-in of the Multiplus.
Just a question: I read somewhere that the Cerbo has to be rebootet after the changement of any settings - otherwise the changements wouldn’t come into effect. Is that true?
Nope. No reboots required. I forgot to say that.
Sorry I wasn’t clear, but I think Bart made my point better than I did.
You can set the low SOC to whatever you like, could be 25%, but then it won’t be triggered until 24%.
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Actually I’d say we complemented each other 
Your statement that the “generator” will only start when SoC is actually below minimum configured SoC (so when minimum SoC is set to 10%, it will only trigger at 9%) is mathematically correct.
My addition to that is that a minimum SoC of 20-30% (that would trigger at 19-29% SoC) is a more conservative and battery-friendly value.
The stealthy denominator keyword is, as all too often, hysteresis.
You don’t want to trigger an event too early (0 sec delay to trigger) because the conditions to trigger may be balancing on the “trigger / don’t trigger” scale.
You want to introduce a delay so that the “OK, GO” condition is really really present and not caused by a variable dancing around the trigger value.
The “Stop” condition shouldn’t be too close to the “Start” condition either, or you risk ending up in a Start/Stop/Start/Stop oscillation.
For a grid connecting relay that isn’t so bad (actually it is, by the excessive wear caused by the short & multiple connect/disconnect cycles) but an actual generator could very well drain it’s starting battery if it has to start too often to run for a too short time.
Repeated short runs (for a relay or a generator) are never a good thing by the way.
This is why there’s a start delay and minimal runtime in the Victron config 
Hi @Bart Champagne und hi @Guy Stewart,
again it was very interesting to hear about your ideas. I understand very well the issue with the hysteresis and, it’s true, temporarily I was on the wrong way with the understanding of the “10%” and “9%”. But due to your precise explications everything is clear now. Thank you very much!
Today we checked the automatic triggering of the relay 1 - but, I am a bit desperate - it didn’t work again. We managed like this:
The current SOC was 85%. My Tanzanian colleague set the lower threshold to 84% and we waited until 83% and some minutes more. But nothing happened…
It’s really strange.
Currently, my colleague meanwhile finished work and went home, I by myself, sitting in Germany, tried to switch the relay manually by the VRM from the remote console. This works correctly - I can start and stop the “generator” from my remote place manually. But I have no idea what the hell goes on with our configuration of the Cerbo…
Good evening again to you all,
when I was again thinking about the problem I came to the conclusion that something with the software in our Cerbo must be wrong so that it can’t trigger the relay by the value of SOC.
The Version of our Cerbo’s firmware is v3.41
Would it be reasonable to download v3.41 again from the official Victron website, to put it on a stick and to “update” the Cerbo with the same (but properly downloaded) firmware? If something was wrong with the firmware by any reason then it might be fixed on this way?
Or is my idea unreasonable?
v3.41 is kind of an old version (dates back from July 31, 2024), why didn’t you mention it earlier that you were running VenusOS antique ?
Not that I expect it to have a bug in the generator start routines, I was using the Generator start feature (to start an actual generator) in even older versions than v3.20 and can’t recall ever seeing a bug with it.
Instead of the USB option, why not simply do an over-the-air upgrade to latest stable v3.55 ?
Settings → Firmware → Online updates → Check for updates → Upgrade
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It’s one of the reasons I would encourage people to install an intermediate slave relay from the Cerbo to energise the larger contactor relay coil.
Thank you so far.
Well, the reason that I hesitated updating the firmware was a comment which I read somewhere that “you shouldn’t update a stable running system” - unless you have convincing reasons for that.
But now I updated directly over-the-air without any problems to v3.55.
Just I tested the function of the relay again in the usual way: While the running state of SOC in the evening was 77% (during the discharge period) I set the threshold for the relay switch-on to 76% and waited until the SOC went down to 75% and furthermore beyond that long enough that the relay should have had switched.
It didn’t - it’s really frustrating.
I can trigger it manually without any problem but the automatic trigger doesn’t work.
I have no idea what to do now and in which way I could approach the failure by doing additional checks…
Please post screenshots from your CerboGX WEBUI settings for:
CERBO WEBUI → Settings → Relay (and appropriate sub-menu options)
CERBO WEBUI → Settings → Generator Start / Stop (and sub menus).
Hi Neptune UK,
thank you for your asking. I will add some pictures.
There were the steps which we had been following:
1st step:
Settings → Relay → Function Relay 1 → Generator start/stop (see pictures 1-2)
2nd step:
Settings → Generator start/stop → auto start functionality → (slider in position „on“) (see picture 3)
3rd step:
Settings → Generator start/stop → Settings (in submenu “generator start/stop”) → Conditions → Battery SOC enabled → Use battery SOC value to start/stop → start when battery SOC is lower than 10% → stop when battery SOC is higher than 40% (see pictures 4-5)
4th step:
Settings → General → reboot
I’d be very thankful if you can give some further advice!
Greetings
There’s no need to reboot after changing settings, it can even cause problems (if the device is rebooted before settings are written to flash disk).
15% SoC seems on the low side to kick in but otherwise that config looks OK.
“Minimum run time” I’d change to 5 minutes.
What’s under the “Warm-up & cool-down” section ?
@BartChampagne has made good suggestions.
Why 'warm-up' a generator
The reason for a warm-up of a generator is allow it to start and get up to operating performance before applying a load.
The application of a load on the generator output before it even starts properly could cause the start sequence for a generator to terminate.
For some peace of mind I would also, if it is possible, measure if the relay closes on the autostart conditions being met, with a simple multimeter, just test for continuity through the relay, before, during and after the autostart sequence.
If the relay is closing as expected this points to something with the ‘autostart’ system of your ‘generator’ in this case is it a ‘contactor’ or other relay of some description. If the Cerbo relay doesn’t close (and remain closed) then it is Cerbo related (setting etc).
You could also try to see what happens on a ‘Periodic’ start for the generator. See my later post as to why you might want to test this.
OP doesn’t have an actual generator but is using the Generator Start function to drive a relay to connect to the grid
And it works with a manual start.
Dear friends,
thank you for your replys. It is like Bart Champagne and pwfarnell said: The contacts of the relay are not the problem as well as the generator (because it’s the grid). It is something with the configuration…
I am following this failure now over more than 1 year…
If my Cerbo might have an interior problem?
Is there a help by Victron’s company over remote access, isn’t it? Did you ever need that or have experiences with it?
Which shows the dedicated internal software switching of the relays works, using the in-built software flow which is basically changing the value of the . E.g 1/0, on/off, true/false. This is very basic.
It’s established the relay does function in this regard.
The test I suggested should demonstrate if the additional logic that has been created is functioning as expected, and actually terminates with the closing of the relay when the logic conditions have been met.
This means we don’t have to rely on assumption as to what has happened. It should only take 1-2 minutes (as the OP has been at this for a year, 2 mins is nothing). Disconnect relay wiring, connect multimeter probes, observe measurement when condition logic runs.
Alternatively if they were running V3.60 (EDIT: This is also true for V3.52):
WEBUI (Main Dashboard)->Settings->Debug->Values->settings->0->Settings->Relay->0->InitialState
0 for off/false, 1 for on/true (NO relay)
As the relay state changes, the current state will be displayed as the value for ‘InitialState’.
If this changes as expected as a result of the logic conditions being met, then I would get physical confirmation by testing the relay outputs with a multimeter.
As I mentioned this factually establishes if the logic is functioning and physically closing the relay.
This was the reason for doing a test with the periodic start which employs AND/OR logic and not a simple 1/0 like the manual start.
Then we are back to the overall Cerbo settings, so we could ask the OP to obtain the settings XML file and see how the Cerbo is actually configured. This is comparable against a known good setup with the relay[1] being used in it’s generator stop/start configuration.
We then rule out a lot and guess about nothing.
I can’t imagine any professional engineer who simply uses an isolator to ensure the system is de-energised and then sets about working on it, via assumption, without confirming the system is de-energised with a multimeter also (and yes, I do a continuity test with the probes before and after testing the system), as it only takes seconds to do.
I’ve edited my previous response to be less directed at the OP. As others may search the forum, and you mentioned:
Also this post refers to ‘relay 1’ and a good number of people will be using the generator autostart capabilities of relay 1 to start a generator.
I simply thought it may have been appropriate to explain why someone may want to use these settings with a little background.