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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.

solarquattro 10kva
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Al avatar image Al commented ·

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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pwfarnell answered ·

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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