Generator Running during cool down period but does not shed loads

My system is installed in a Class A, motorhome and I am currently dry-camping in the Arizona desert.

My system includes two Multiplus-II 24/3000/70-50 2x120 running in parallel. My Cerbo GX is running v3.52 software. I have set the Warm-Up time at 120 seconds and the Cool-Down time to 240 seconds.

My Generator Start/Stop is controlled by Relay #1 on the Cerbo GX. When the relay operates, picks, the start signal is passed to the Generator control and the generator, after the start-warm-up delay time will start. When the generator starts, the coach’s transfer switch sends a digital signal to the Cerbo GX digital input #1 with Generator selected as the meaning of this signal. When the generator starts, the system recognizes that the generator is running and reports the same.

Today, I had the opportunity to watch the system operate during a Periodic Run for battery charging.

Towards the end of the periodic run, the generator load was at about 25%-50%. I was paying particular attention to the end of the run time hoping to see how the Cool-Down time period worked.

On the venus-gui-v2 screens, I found that the system reported that the generator was running in the Cool-Down time period. The load on the generator had not changed and did not change during this time period. It was still running between 20%-40% depending what systems in the coach were using power.

My expectation of the Cool-Down period was that the loads on the generator would be completely removed. As far as I could see, the Cool-Down period did not reduce the generator loading and, therefore, did not unload the generator. So my basic question is, how is the generator supposed to cool down if the load on the generator is not reduced?

I would like to add that I had created a warm up and cool down function before the Venus software was updated. My solution involved using the Assistants in the Multiplus-IIs and multiple timer relays. My approach was to tell the Multiplus-IIs to ignore the AC inputs during the Cool Down period which effectively took the generator load to less than 1%. While my approach worked, it was not clean and easy to adjust. When the Venus software updates that included the Warm Up and Cool Down functions were release, I removed my timer relays and removed the Assistants and the signals to affect the Assistant operation.

Any help, thoughts, or suggestions are greatly appreciated.

Hi that’s odd as i understand this below that is what should happen. (i could be misunderstanding it tho…)

Cool-down time:

  • The time required for the generator to cool down before the engine is stopped. During this time, the Multi/Quattro will disconnect the AC and run the load from the batteries. At the end of this time period, the GX will signal the generator to stop.

16. GX - Generator auto start/stop (victronenergy.com)

@pwfarnell beat me to it…

Have you got firmware 502 or higher in the Multipluses.

@nesswill , @pwfarnell , When I was running my own, cobbled together Cool-Down routine, during the Cool-Down time, I used an assistant to tell the Multis to ignore the AC Input. During the Cool-Down time, all coach AC was supplied from the Inverters using battery power. This is what I expected to see in the updated Venus software.

What I observed yesterday was the batteries still charging off of the generator right up to the generator shutdown.

I am currently running v552 on the Multis, which is reported to be up to date.

Just an update.

I decided to recheck that I had removed the ‘Ignore AC Input’ assistants in the Multiplus-IIs. I found that I had removed the assistant on one of the Multis but not on the other.

I removed the ‘Ignore AC Input’ assistant and after the system re-booted, I ran a test run of the generator. After the 30 minute timed run, the Gui reported that the generator was running in Cool Down mode. The load on the generator load remained at about 83% of maximum. I had sure hoped that the removal of the ‘Ignore AC Input’ assistant would have made a difference.

Have you double checked all your setting against the link below?
16. GX - Generator auto start/stop (victronenergy.com)

@nesswill, I have checked and re-checked. I keep hoping that I have missed something simple.

I am using Relay #1 on the Cerbo GX to start and to stop the generator. My coach has a transfer switch that gives a signal if the AC is coming from the generator. That signal is connected to digital input #1 and labeled generator in the software.

It is my understanding that when the conditions are met in the Cerbo GX to run the generator, the Cerbo picks Relay #1. That closes contact to my generator control. So long as Relay #1 is picked, my control starts the generator. When the generator starts, power is supplied to my coach transfer switch. That switch is wired to favor the generator if I am currently connected to shore power. Whether connected to shore power or not, when the generator starts, the coach transfer switch delays connecting the generator to the lines for about 30 seconds to allow the generator time to stabilize. When the transfer switch transitions, it sends the signal to the Cerbo that the power source is the generator. So long as the generator is running, the transfer switch does not transition back and the digital signal stays in the generator position.

When the Cerbo decides that the ‘Stop Generator’ conditions have been met, it drops relay #1. When relay #1 drops, it sends a signal to the generator controls to stop the generator.

I make an assumption, which may not be valid, that the current Venus software must control the Multiplus to tell it to “Ignore AC Input” during any warm up or cool down time periods. I do not know if there is another way to unload the generator during warm up and cool down times.

As an aside, before the software was updated, I had implemented a warm up and cool down function using timer relays and the ‘Assistants’ in the Multiplus units. As I remember, I used the General Flag to signal when to ignore the AC Input, and sent a signal using a timer relay to trigger this function. When the Cerbo sent a start command by picking relay #1, the generator would start but the load application would be delayed by the transfer switch and my delay relay. When the Cerbo decided to stop the generator, it would drop relay #1. My timer relays would keep the generator running for a timed period with no load and then shut down the generator. My solution worked, but it was not elegant. When I saw that the software had been updated to include the warm up and cool down features, I tried the new software and the warm up/cool down features did not work. I was advised to remove my circuitry and update the Multiplus software.

I do not know if this could be a problem, but please remember that I am running my two units in a parallel configuration. Could it be that one unit is being told to ignore the input but the other unit is not? When I am looking for the unloading of the generator, my battery charge is substantially complete and one charger could be supplying all of the loading on the generator. I do not know how I would check to see if one Multi is ignoring the input AC but the other Multi is not.

To answer one more thought, all power to my coach, whether from a shore power source or the generator goes through the transfer switch and then to the Multis. This is to say that any load on the generator must pass through the Multi first.

I appreciate the help.

Ok well not much more i can suggest maybe one of Victron Experts can comment, @JohnC or @pwfarnell could you help?

I am out of ideas, @johnjaymack beat me to checking both Multiplus units were clear of assistants. The only other snippet I have seen is that if the Multiplus believes it goes into overload during warm up / shut down it will draw from the generator and ignore these settings.

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Split phase I suspect. Maybe ‘Switch as a Group’ is unchecked?

If you’re watching it on VRM, there’s issues there with how it reports genset running. Stick with NewUI.

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I do not know if this was a question, but the generator does not supply split phase. Initially I thought that since the output was on a ganged breaker that it was split phase. I was told later that it is not and I confirmed that it is not using a meter.

I am using one assistant on one unit to signal that I have shore power or not. When I have shore power or generator, the unit picks its relay. This turns on a green led inside the coach confirming that I have power. When shore power or the generator does not provide power, the relay drops illuminating a red warning led. In parallel with the red led I have an audible alarm that can be armed when on true shore power. If shore power drops unexpectedly, the audible alarm alerts us immediately.

I have another issue that I am not asking about at this time, but I will mention it in case it sparks a thought. My Cerbo has been randomly re-booting multiple times each day. This issue started after the software update last January or March. Working with my vendor, we were going to replace the Cerbo, and maybe that is the path that I should follow, but while waiting for the replacement, I decided to do a clean software install. At the same time, I decided to move the location of the Cerbo out of the basement and into the coach where the ambient temperature is better controlled.

After the clean software install, the number of reboots decreased. Two days ago while doing my daily battery recharge, the Cerbo was rebooting about every 15-20 minutes. Every time the Cerbo comes back up, it continues with the scheduled recharge. After the batteries were charged, I decided to unplug the Cerbo for about a minute, and then plug back in. Yesterday, the Cerbo did not reboot that I know of, but I was not at the coach and cannot be sure. Thinking that maybe the cpu was being over used, I have been running the ‘top’ command. ‘cpu’ percentage is running between 25%-33% with a high of 49%.

I do not want to address the rebooting in this thread since I believe that it is a separate issue. I mention it though so that those who understand the software better may see a connection between the problems that I do not see.

Just a short update. I am using the new GUI and I clicked on the upper left corner area to show the generator on the left panel. I watched this panel as I started the generator. After I started the generator, the panel reported that the generator was running and that it was in a warm up mode. My coach transfer switch has a built in warm up period before it transfers. When my transfer switch connected the generator, the load on the generator was immediately applied even though the GUI was still reporting that the warm up period was still in effect. When the warm up period expired, the load on the generator did not change.

So a question that I have is how does the system unload the generator? I start the generator by picking Relay #1 on the Cerbo. The “generator is running” signal is connected to digital input #1. Are there supposed to be any other connections?

I am back on shore power for now, but I would like to resolve this issue. Any suggestions or advice would be greatly appreciated. Especially if the problem is caused my me.

Hi John, how,s this going?

What Generator do you have? I have one on these DHY18KSEm i ask because of the type of controller it has mine is InteliLite so for me its via Modbus, using the ComAp CM3-Ethernet module.
Below are a few links that might be worth a read.
https://www.victronenergy.com/media/pg/CCGX/en/connecting-supported-non-victron-products.html#UUID-73fa2d0e-1d42-a05f-5dc2-c81c6273659a
https://www.victronenergy.com/live/multiplus_faq
https://www.victronenergy.com/media/pg/Automatic_Generator_start-stop/en/index-en.html

Hello Dave,

Things are going well here in Northern Arizona. I will apologies for the long answer, but I sense that some are missing what is happening. The short answer is that the Cerbo GX has been controlling the Start and Stop of the generator without problems since December of 2022. There are ONLY two connections between the generator and the Cerbo: Relay #1 on the Cerbo to Start and stop the Generator, and Digital Input #1 from the coach transfer switch to indicate that the generator is running. The Warm Up and Cool Down functions do not work.

I have an Onan 8Kw generator. Originally, it used a Precision Circuits AGS for automatic Start and Stop. I also have manual Start/Stop switches both in the coach and on the generator. This is a three wire system.

When I upgraded my coach’s electrical system, I removed the original Precision Circuit AGS because it was no longer functioning. I decided to replicate the generator Start/Stop functions using a timer relay system which is triggered by the Cerbo GX relay #1. My timer relays cost me about $60 US to implement. Since that time, I have found several other Generator Control Modules that replicate my timer relay functions for $200 US. Here is how my system currently works.

In the Venus software, AutoStart functionality is set to ON. Under Settings-Conditions, the various conditions for Starting and Stopping the generator are set. For example, I am currently on shore power so I have Battery SOC and Battery Voltage set to start the generator automatically if my shore power connection is broken. As an example, we lost shore power one evening at around 1730. Since we were fully charged and expected the power company to restore power within a few hours, we did not start our generator. We also did not revert to Dry Camping power consumption for heating. Instead, I left two of the heat pumps operating on the batteries.

The power company must have had a difficult issue to resolve because the power was off for 14 hours. Leaving the heat pumps running drained the batteries, as expected, causing a SOC generator start.

So, when the Generator Start conditions are met in the Venus software, the Cerbo GX picks relay #1. The NO contacts of this Cerbo relay apply power to my START timer relay. My Start Relay is configured as an Interval On relay. My relay applies a start signal for about 45 seconds. This signal parallels and simulates my manually operating a start button for 45 seconds. The 45 second operation of the signal insures that the generator start routine is completed whether the outside weather is hot or cold. At the end of 45 seconds, the Start signal is removed from the generator.

When the Generator Stop conditions are met in the Venus software, the Cerbo drops Relay #1. The NO contacts of Relay #1 remove power from my Start relay. The NC contacts apply power to My Stop relay. My Stop relay is configured as an Interval On relay. This relay applies a Stop signal to the generator stop circuitry for 20 seconds causing the generator to stop running. At the end of 20 seconds, the stop signal is removed.

To make this very simple, the Cerbo Starts the generator by picking Relay #1, and Stops the generator by dropping Relay #1. What I see happening by watching the Venus gui is that the generator reports that it is running. I believe that that piece of information is provided by the digital signal from my transfer switch to the Cerbo Digital input #1.

The Venus gui reports that the generator is warming up. However, when my transfer switch connects the generator output to the Multiplus IIs, they immediately begin drawing power even though the gui is reporting that the Warm Up Period is still operator… If the Venus software was actually controlling the warm up time, then the Multiplus IIs should Not be drawing power until after the Warm Up time period has expired.

After the Run Conditions have been met and the Cerbo is going to Shut Down the generator, I noticed that the Venus gui reports that a Cool Down period in in operation. However, during the Cool Down period, the Multiplus IIs continue to place a full load on the generator. At the end on the Cool Down period, the Cerbo drops Relay #1 which stops the generator. The Generator Running signal is removed.

In December, 2023, I had created a Warm Up and Cool Down control by using some Assistants in the Multiplus IIs. By using a couple of timer relays, I applied a Warm Up and a Cool Down signal to the Multiplus IIs during the start and stop time. My circuitry worked but it was not elegant and did not report on the gui what was happening. When the Venus software was updated to provide the Warm Up and Cool Down function in an easily programmable manner, I made the choice to change back to a more standard, software controlled operation.

My question to the Victron software engineers and software experts is, **how does the software control the load imposed on the generator? With my load-shedding method, I told the Multiplus IIs to Ignore AC Input using Assistants. With that signal in place, the Multiplus IIs removed all load from the generator. What is the current software process for removing the load? Is it possible to see some process happening in software that would verify what is happening? I am not a software engineer so what I report is my observations. I have run the Top command from the command line, but I really do not know what I am looking at or looking for.

All for now. I hope that I have explained the problem properly.

I will be changing locations tomorrow, staying in a RV park for 4 days and then off to the desert.

I updated the software to v3.54. When in the desert, I run the generator daily for battery recharge. I will see if the warm up/cool down function will work in v3.54.

I still would like to know how the generator ‘unloading’ for warm up/ cool down is accomplished. Is there a write up somewhere that explains how the software accomplishes this function? I know that using Assistants can tell the Multiplus IIIs to ignore the AC input even though it is connected. Would that function be the one that the software is supposed to control during warm up/cool down time?

I am running the two Multiplus IIs in a parallel configuration. Could the software be telling one of the Multiplus IIs to ignore AC input but not the other one?

When I first tried the Warm up/Cool Down features, I remember being told that the Cerbo needed two digital inputs to tell it that the generator was running. I cannot find that post and suspect that it was on the old post system. Does it make any sense that the Cerbo would require two digital signals to tell it that the generator is running? I only have one signal but I can parallel it into two digital inputs. The Cerbo already reports correctly when the generator is running, but if telling twice is needed, I can do that.

Any thoughts are appreciated.