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 coachâs 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.