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jbates5873 asked

Multiplus-II 5K Derating

Hi all.

I have a MP2 gx 5k.

I have an issue where it de-rates its self due to the enclosuren its in. No biggie this is expected due to the constraints on the install.

However, I'm building an automation in node red that controls it based on my electricity company rates. I have this all worked out, however, I have an issue where my output value for pv inerter control is fighting with the derating of the multi (originally I hardcoded in for it to do about 65A)

This was an issue over the weekend where the output of my tooling sent the PV inverters to essentially 0W output.

So, I'm looking for an endpoint that I can get the max charge rate of the multi, that factors in its de rated output.

I.e, normally it runs at 3500w, however it gets warm, and tunes down to 2500w, I want to query it and get the 2500w value.

I'm just not sure where to point it. I have looked at all the endpoints in the Victron Node Red package, but none give the value I'm expecting to see.

So asking for some help on locating the correct endpoint.

I could possibly look to map it based on the whitepaper and the info in it (source: https://www.victronenergy.com/upload/documents/Output-rating-operating-temperature-and-efficiency.pdf). But am looking to avoid the extra math and potential mis calculations if i can just get the value directly. Im sure that the number would need to exist somewhere, as it limits the unit when the threshold is met.

Failing the maximim current charge rate endpoint existing, from what i understand the internal temp sensor is also not available to be read so that i can load in the mapped values from the whitepaper to perform the calculation. So im not exactly sure how to approach it.

Cheers

Multiplus-II
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Alexandra avatar image Alexandra ♦ commented ·
Have you tried adding your own temperature sensor? One comes in the box with the multi 2. Good physical placement ie in or on top of the unit, and when plugged into t sense it does report to the vrm so the value probably be intercepted and used in your flows.

Just throwing down ideas. Have baked. I have not tried it.

If you have a cerbo, then you can see it that way as well.


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jbates5873 avatar image jbates5873 Alexandra ♦ commented ·
As mine is a GX, and the battery temp is reported by the BMS, I was under the impression that using the temp sensor won't work. As its fir the battery temps.


Could be wrong though. But yes, the idea has crossed my mind. I just don't want to book a perfectlyntuned system. Haha

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Alexandra avatar image Alexandra ♦ jbates5873 commented ·

You can connect the inverter temp sensor to the cerbo.


It does not have to be connected to the battery at all. I use several in my home install for room temp battery compartment and top of the inverter temps.


They do sometimes need calibration when used with the cerbo, but is easily done as a super user, a quick google search will get you what you need to know. I had to calibrate one of the three installed.

On my mobile system I have it connected to the inverter and can see the compartment temp on the vrm advanced widget.

https://www.victronenergy.com/live/temperature_sensors

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jbates5873 avatar image jbates5873 Alexandra ♦ commented ·
i dont have a cerbo though. i have the multilus II GX. from what i can gather, as i have DVCC enabled on it so that the temperature comes to the MULTI from my BMS, i cant use the tem probe. so my options are

1. Get the correct endpoint that gives me the vaule

2. put an external system in place to get the temps, and then do a map across from that.


so hopefully, someone from Victron chimes in and tells me the enspoint i need :)

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Alexandra avatar image Alexandra ♦ jbates5873 commented ·

Since you arent using temperature compensated charging, the temp sensor wont affect anything.

You can connect it to the inverter and place the terminal ring side where you want to measure the temperature.

You can load an advanced widget in VRM and see the temp it measures there

I know this works i have done it....

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larsea-dk avatar image larsea-dk Alexandra ♦ commented ·
Just note that it "only" goes to 60degree and then cuts out. I have mine connected to the bolt on the ring trafo...and it exceeds the 60degrees.

So I'm working on an add-on cooling solution with additional fans. Just need to find out where to take the power to the fans. My battery max is 63volts, so this is too much for a std. 48v fan. Also not many stepdown converters to find above the 65volts...

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