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pieslinger avatar image
pieslinger asked

Cerbo GX open battery switch monitor

Hello, I recently left my battery isolation switch open ( it is between my multi plus 2 and a 48v battery string that has a smart shunt monitoring it. ) and was caught with no power when my utility failed.


User error I know. But I found it odd that I can leave it open and nothing report’s anything is abnormal. The cerbo is powered off the battery itself so it is happy and the smart shunt will just sit there in storage mode.


I was thinking of using a relay powered by the DC voltage present at the MP2 DC terminals to return an input to the cerbo.


I assume people have come across this issue before?


Am I doing something wrong?

cerbo gx
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ejrossouw avatar image ejrossouw commented ·
I am curious as to why you would want to disconnect the battery? Do you also turn the inverter off?
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kevgermany answered ·

Unless the MP2 is in inverter mode, there will always be voltage on those terminals, 'on' and 'charger only' will provide power there.

However, if there's a voltage difference between battery plus and inverter plus you have a trigger. Trouble is you'll have a constant alarm every time you isolate the battery.

There's a low battery voltage alarm in the multi, but that's going to give the same problem.

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pieslinger avatar image pieslinger commented ·
An alarm when I isolate the battery is ok with me. That’s basically what I am trying to create.


Does the MP2 have some internal battery monitoring I could tap into? It seems ignored because the smart shunt has taken over the battery control.

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Alexandra avatar image Alexandra ♦ pieslinger commented ·

If you compare the ve battery terminal voltage compared to the shunt voltage you can usually see when there is a disconnect between them.

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pieslinger avatar image pieslinger Alexandra ♦ commented ·
I will try that and report back. Thanks!
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pieslinger avatar image pieslinger pieslinger commented ·
I can poll .Vebus and that returns the DC voltage of the charger and .battery which returns the voltage from the smart shunt and the. .system which returns the DC voltage from the cerbo. And they are all the same. I think because the multiplus defers to the smart shunt, I cannot see it’s reading of the battery voltage.


So I am not sure to compare the items.


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Alexandra avatar image
Alexandra answered ·

If you compare the ve battery terminal voltage compared to the shunt voltage you can usually see when there is a disconnect between them.

You could use a well placed micro switch and a cerbo gx digital input configured as a door open alarm.

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