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hoeken avatar image
hoeken asked

DVCC with two different inverters + Cerbo + Lynx Smart BMS

I have a sailboat with a lithium battery system, cerbo, lynx smart bms, a 5000w 230v Quattro and a separate 5000w 120v Quattro. The 230v Quattro is connected to the cerbo directly via VE.Bus. The 120v Quattro is connected to the Cerbo via a USB MK3. The system is working well and I can see and control both inverters from the Cerbo.

I'm trying to set it up so that both inverters shut off when the battery gets to a certain SOC (20%). I found that in the Lynx Smart BMS I can set the discharge floor with Victron Connect and that will disable the ATD. The 230v quattro that is connected directly via VE.Bus turns on and off as expected, but the 120v quattro over the USB MK3 is not turning on or off.

Are there any settings I need to change to get the 2nd inverter to follow the DVCC instructions from the Cerbo? I've looked around quite a bit and nothing is jumping out at me.

cerbo gxDVCClynx bms
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nickdb avatar image
nickdb answered ·

You can't control multiple, independent inverters with a single GX. It is not designed to work that way. You will only have partial functionality and DVCC will not work in that scenario.

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hoeken avatar image hoeken commented ·
This seems like a strange oversight on Victron's part. Do you know what the technical reason behind it is? I don't know how the code underneath the hood runs, but it seems like it should be a pretty straightforward software change. Instead of hardcoding as a single inverter, loop through any available inverters / VE.Bus connections when sending ATC and ATD.


To be clear, they are separate inverters, on separate VE.Bus'es. It is already working for me to see both of them on the Cerbo, as well as control on/off/charger state through the cerbo for both. So its definitely possible to do this, but whether it is a software development priority is a different question.

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nickdb avatar image nickdb ♦♦ hoeken commented ·

The GX and DVCC can only work with a single logical system of devices on a shared VEBUS, configured as 3phase/Parallel. These inverters will appear as one logical system, but with multiple phases (in a 3 phase setup).

Parallel systems are in a master/slave configuration.

This is all fairly clear from the docs.

There is a lot that goes on in the coordination of a multi-inverter setup, trying to do this reliably across independent systems is likely more complex than it appears.

It is a bit of a niche requirement.



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hoeken avatar image hoeken nickdb ♦♦ commented ·

I agree it is somewhat of a niche requirement, but then again I think this is a somewhat common setup on boats that travel internationally and want to have a boat that is voltage agnostic. I know this is the standard setup for the manufacturer of my boat and a few others as well.

I am not trying to run a parallel system, master/slave, split, etc. These are two completely independent inverters that are connected to the same battery bank. One of the inverters 230v / 50hz, and one of the inverters is 120v / 60hz. Each inverter has its own separate shore power input, separate AC outputs, and separate VE.Bus connection to the Cerbo. The only thing they share is a DC connection to the same battery bank.

The Cerbo side connections are:

Cerbo VE.Bus Port -> 230v Inverter VE.Bus

and

Cerbo -> USB MK3 -> 120v Inverter VE.Bus


I'd also like to re-iterate that the Venus OS can definitely handle multiple VE.Bus systems. I can see and control both inverters from the main screen on the Touch. On/Off, current control, the works. It just isn't sending the ATC/ATD to the second inverter.

Anyway, it seems it is not possible at this point in time. I'm not trying to start an internet fight, but I just wanted to make sure that my issues and my setup are understood in case someone from Victron reads this and can help.

In the meantime, it looks like I will have to wire the 2nd inverter up and use a 2-wire BMS. Not the end of the world, but it sure would be nice to have it all be plug and play and not have to mess with assistants, etc.

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nickdb avatar image nickdb ♦♦ hoeken commented ·

If you are dev savvy, you could consider a second gx and try automate from a higher level so you have control.

Node red on the current gx may also give you some additional capability.

You can put a feature request on the modifications section, you may also get some helpful ideas from the people that go off piste with victron systems. Chances are there is already some third party dev work you could borrow.

So I will relocate this to that section as its better placed there.

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hoeken avatar image hoeken nickdb ♦♦ commented ·
Thanks, I appreciate that.


I've been meaning to check out Node Red. I've already got a Raspberry Pi running on the system pulling in data from the Cerbo, so maybe that will be an option as well.
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nickdb avatar image nickdb ♦♦ hoeken commented ·
If you trawl the mods section, chances are you will find some ideas, as you said, your use-case isn’t unique. Good luck.
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najab avatar image najab hoeken commented ·

I would have thought the way to be 'voltage agnostic' would be a single 230V inverter and an autotransformer to provide 115V as needed. That would be a lot simpler overall and likely has a higher efficiency as well.

On the charging side, you could have a 115V Skylla.

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hoeken avatar image hoeken najab commented ·

We went back and forth on this during the design phase, and dual inverter/chargers won out for a few reasons. Mainly the autotransformer only changes the voltage, and doesn't change the frequency. Some appliances don't like that.

Also, the boat is a 48v system. The only 48v charger is the Skylla TG that does 50A. The 5kw inverter/charger will do 70A. Also the Skylla charger is "dumb", so no data in VRM or Grafana on power usage, etc. Definitely not any DVCC.

Assuming the main inverters are 230v, then to get 10kw 230v and 5kw of 120v (what I have now), then we'd need an extra 5kw of 230v, the auto transformer, and a Skylla charger. That's a lot of complexity (and weight!) for no real benefit. Also the Quattro/Multiplus products are very popular, well supported, and easily available.

For those reasons we added a 5kw 120v quattro. It shows up on the Cerbo, in VRM, and I can get the data into Grafana. The only real gripe I have is that it doesn't get controlled with the VE.Bus for ATC/ATD. I set it up with a 2 wire BMS assistant and now it works fine.



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semlohnhoj avatar image semlohnhoj hoeken commented ·

I suspect that part of the reason this isn't possible at present is that most of the internal registers for the state of an inverter are mapped to specific variables ( in the case of Modbus, to specific addresses) so there is no way to uniquely identify the units for some features. I've got this issue with a Multi RS Solar and an Inverter RS Smart. The Modbus address are identical. I'm hoping it gives them unique identities in NodeRed but I'm not confident.

I haven't even started trying to work this out as the second inverter hasn't arrived yet but as @nickdb has suggested, it's probably a second instance of Venus on a Raspberry Pi if you want full access. No idea how you'd get the DVCC working at that point though.

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