Switching immersion heater on ACOUT2 using external BMS SoC

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iand asked 4 days ago

Switching immersion heater on ACOUT2 using external BMS SoC

I have an immersion heater on my boat connected to ACOUT2 (Quattro 48/10000), this is switched on by an assistant near 100% SoC to make use of spare solar power. However with an external BMS controlling the Quattro (REC-BMS in my case) it only seems possible to do this using battery voltage not SoC.

This works OK with just solar charging, for example turn on at 53.8V (about 99% SoC) and off at 53.2V (about 95% SoC). But with generator or shoreline charging the battery voltage rises and the immersion turns on too soon, using generator/shoreline power which I don't want (I only want to use excess solar).

Is there any way to use the BMS SoC to trigger the switching instead of battery voltage?

Or can the assistant only turn it on when there's no AC input?

Needs to be done just with assistants on the Cerbo or Quattro not Node Red, the firmware setup is currently supported and maintained by the boatbuilder who doesn't use this.

solar quattro 10kva

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Al commented · 4 days ago

Yep, as mentioned I think you need to make sure 'use battery monitor' is selected in veconfig. You may need to select the battery monitor in Cerbo settings as your REC BMS but this should have been done already. I have set a couple of systems all on boats and houseboats using Pylontech batteries and assistants to control ACout2 dedicated to an immersion for hot water. Both Multi's and only a few days ago again on a Quattro. Both work, although I still can't believe Victron haven't created a dedicated comprehensive heater diversion assistant without reversed logic, or a dedicated hot water diversion relay control in Venus after how many years we're waiting..

Unfortunately as of today the way to do it is a bit clunky as the assistant logic is reversed, I've tried playing around with the Cerbo generator controls for relay 1 to trigger the Multi aux input, but then you lose actual generator controls and it gets confusing really quickly and I just didn't like it.

I did though use the Cerbo generator control as a simple secondary dumb logic remote immersion on off switch (so it could be used to heat up the water tank on your way home from the VRM app) On the latest Quattro system it's wired into the Quattro Aux in / or it could instead use Cerbo relay 2 output to Quattro Aux in, but only Cerbo relay 1 is currently accessible easily on the GX screen without also installing GuiMods.

Here's the latest Quattro assistants, remember the "generator start and stop" logic is reversed: (Turn immersion off if loads are over 7000w - turn on Immersion when loads are below 5000w etc)

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working.jpg (90.2 KiB)

iand Al commented · 4 days ago

Hi Al

Thanks for the reply, but I'm a bit confused...

The way the boat was set up by the builder, I already use generator autostart/autostop on the Cerbo using relay1 to control the generator (via a couple of pulse generators because that's what the Kohler genny needs). The battery monitor is selected to be the REC-BMS.

The immersion is connected to ACOUT2 and a Quattro assistant turns it on and off accoording to battery voltage, SoC is not an option with the Quattro externally controlled (BMS is the master).

Is the generator assistant you're referring to different to the one I already use? I don't see how I can have two in the system, one controlling the generator via relay1 and one controlling the immersion via ACOUT2 -- or is this just a second copy of the assistant and the two work independently?

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Al iand commented · 4 days ago

Hi @IanD

Ok if you're already using relay 1 on the Cerbo for genny start, then you'd use relay 2 for other functions instead.

I'm not sure why you keep saying: "SoC is not an option with the Quattro externally controlled (BMS is the master)."

SOC to trigger assistants works fine for me on the systems I've set up and many others use SOC for assistants with external BMS's.

You can use the VeConfig generator start stop assistant as many times as you want, to do multiple different things (not just for generators!), and it is not linked in any way to the Cerbo generator control, so yes you can run them both at the same time for different tasks.

Maybe show your current assistants on the Quattro, or create a new one as I showed above and see if it works for you. If you're not needing a second on off for the immersion on top of the main SOC based assistant you don't need to worry about using relay 2 and connecting it to an Aux input on the Quattro, so could ignore the two programmable relay assistants above it in my screengrab.

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Modifications Space

Node Red Space

Answer 1 · 2024-07-22T21:06:32Z

pwfarnell answered · 4 days ago

This is not 100% definitive because I have Multiplus not Quattro. On the Multiplus settings tab "General" you can enable the battery monitor but with a GX device the inverter SOC mirrors the GX SOC which comes from the device that has been specified as the system battery monitor and should be available to assistants to use. However, I have also seen people recommend that it is disabled if you have another source for SOC.

There have been previous posts about using the generator assistant to control AC Out2 for water heating because the generator assistant has the ability to have multiple triggers. The output needs inverting, i.e. you want the heater on when a generator would be off. I assume that this can also be done with several assistants but I have not tried that.

https://community.victronenergy.com/questions/57414/help-with-assistants-to-use-ac2-as-dumload.html

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