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stourel avatar image
stourel asked

Cerbo DC Power

Hi everybody,


I have a Cerbo GX, together with a Quattro Multiplus 12V/5000, a BMV712 and a MPPT Solar from Victron.


I have been wondering about the power consumption of the Cerbo, which you can see on the picture is in the range of 70w to 130w. It is quite far away form the 20w mentioned in the forum and I wondering what is going on. Cerbo is the only 12v device connected to the battery,


I also noticed that the Ah deducted by the BMV 712 is higher that the real Ah consumed. for example, overnight the % of the batterie decrease from 100 to 90% and the following day, the battery charge to 95% reaching floating. The BMV noticed that the battery are full and reajust the SOC to 100%.


The problem is if I am not reaching the required voltage corresponding to 100%, the SOC reduce too much from about 5% everyday. for example 1 week ago, my battery voltage was 12,8V under 250w consumption but the SOC was 60%. This can not be right.


Can somebody help me? I hope it is quite understandable.


Thank you.




Best



Sylcerbo-gx-160522.jpg

cerbo gx
cerbo-gx-160522.jpg (41.4 KiB)
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Alexandra avatar image Alexandra ♦ commented ·

@stourel

If you disconnect averything from the bmv do you see a current draw?

You may have to do a zero current calibration.


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stourel avatar image
stourel answered ·

Hi Alexandra,

Thank you for your reply. How can I disconnect everything from the BMV? Inverter off, cerbo unconnecting. what else?

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Alexandra avatar image Alexandra ♦ commented ·

Hi @stourel

The instructions are here.

Once everything is off, you have to physically disconnect everything from the load side of the shunt.

Use Victron Connect to see what the BMV says is happening. If it sbows no current draw then you dont need to do the zero current calibration.

If it is showing current draw with nothing connected then go to battery settings and at the bottom you will see the option.

screenshot-20220516-192617.jpg


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stourel avatar image stourel Alexandra ♦ commented ·
Dear Alexandra,


Thank you for you help. I was not close to my installation, and I could first check last friday.

Indeed I had to do a zero current calibration. The consumption of the cerbo droped from 70w down to about 35w. And the calculated SOC seem to get calculated better.

I have an other question to you: Can you explain to me why the cerbo consume more enegy when the load on AC1 increase? 150w by 1000w AC load.

The consumption of the cerbo is proportinal to the AC load, and I can't find a logic explaination.

What do I am missing? Thank you in advance for your help.

Best


Sylvain


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seb71 avatar image seb71 stourel commented ·
That is not the power drawn by Cerbo GX.
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stourel avatar image stourel seb71 commented ·

Hi Seb71,

Thank you for your answer.

The thing is that I don't have anything on DC connected to the battery except Cerbo, BMV, MPPT solar and the inverter.

So I still wondering why my comsuption increase on the DC side when the consumption on the AC side change strongly: by charging and discharging. You can see it on the provided picture.1655714969595.png

1655715225958.png

1655715408183.png


Maybe you have a good explanation? maybe Network with the inverter?

Best


Syl

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stourel avatar image stourel stourel commented ·
Hi Everybody,

did anybody observed this as well?

Best


Syl


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stourel avatar image stourel seb71 commented ·
Hi SEb71,


Thank you for your answer. Have you seen my previous reply? Do you have an idea from where does it come from?


Best


Syl


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seb71 avatar image seb71 stourel commented ·
First of all, you don't have a DC system, so disable that in Cerbo's settings.

Then go from there.

You should be aware that all components draw some power (the inverter is drawing the most) for self-consumption.


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Tien avatar image Tien Alexandra ♦ commented ·
I'm curious, when you do a zero current calibration. Removing everything, which will still leave the Smart Shunt.

Will it take into account the consumption of the Smart Shunt after the calibration?

Because if you calibrate it to 0, would it not be inaccurate because the Smart Shunt would still be consuming power which now has been zeroed out.

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seb71 avatar image seb71 Tien commented ·

No current goes through the shunt (between "Battery" side and "Load" side) when the "Load" side is disconnected. This is the current which the shunt measures.


Obviously the SmartShunt draws a little current (to power itself), but that's a tiny amount (under 0.001A, according to the specifications). The SmartShunt has a separate wire to connect to the battery positive terminal.


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Tien avatar image Tien seb71 commented ·

Yes that's right, but you can't disconnect the SmartShunt out of the system. You need it powered.

But you're right, I just checked the datasheet and it uses bugger all less than 1mA.

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stourel avatar image
stourel answered ·

one is sure, the consumption was more inacurate before the zero calibration


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