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kw4np avatar image
kw4np asked

Smart Shunt - Selecting "DC System" Reverses Current Flow Indication

Perhaps I should clarify that this is just a bit of information about my system for reference:

I'm trying to use a Smart Shunt to measure my DC system which has both loads and chargers (solar). There are three Quattros connected directly to the batteries that measure their own usage and report it via VE.Bus to a Cerbo GX. The Smart Shunt is also connected to the Cerbo GX, and the Cerbo GX should be able to keep track of total SOC by using the data from the Smart Shunt (in DC System mode) and Quattros. The manual seems to indicate that all other modes just display the data. https://www.victronenergy.com/media/pg/CCGX/en/installation.html#UUID-d0c1e103-df9e-4691-b369-33d047b01491

This is the question that's also in the title:

With the Smart Shunt in DC System mode, the current flow from the solar charger is displayed as a negative value. Switching to a different mode in the SmartShunt menu, such as Solar Charger, causes the current to be displayed properly as a positive value. The Shunt is installed properly with loads and chargers (excepting Quattros, which track their own usage) on the System terminal, so that should not be the issue.

Any ideas on why the DC System mode shows a negative value for current entering the batteries?

SmartShunt
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2 Answers
JohnC avatar image
JohnC answered ·

Hi @KW4NP

This is just the way Victron define it. In VRM a 'DC Load' is a positive value. So I guess it's the same for a shunt set up to measure the same thing.

You mention the Cerbo calculating SOC. It doesn't do that. You'd need another shunt that includes all charge/load of the battery.

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kw4np avatar image kw4np commented ·
Hi @JohnC , I see now that the battery power graph goes up when the DC Load goes down, so that makes sense (although it's not very intuitive). Too bad that the Cerbo can't calculate SOC. It has all of the information, and I don't want to split my bus bar. I guess that's another question.

Thanks for your help!


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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @KW4NP,

You say that the Quattros are connected directly to the batteries.

But then also that the Shunt is installed correctly with the loads on the system terminal.


The Quattros negative should be connected to the system terminal of the SmartShunt, not directly to the batteries. The only thing that should be connected to the negative side of the batteries is the SmartShunt battery terminal.

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kw4np avatar image kw4np commented ·
Hi @Guy Stewart (Victron Community Manager) , if I were using it as a battery monitor that's the way it should be connected. But I'm trying to use it to monitor my DC system, so everything except the Quattros are going through the shunt.
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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ kw4np commented ·
Ahh ok,

Why don’t you want to use it as a battery monitor?

It will also measure your DC loads that way, and if wired as above the cerbo GX will automatically subtract the inverter charger loads.

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kw4np avatar image kw4np Guy Stewart (Victron Community Manager) ♦♦ commented ·

@Guy Stewart (Victron Community Manager) I wanted to use it as an energy monitor because so I could use a single bus for all inverter and battery connections. I might have to rethink that as I need to use ESS and it's not clear if the Cerbo will be able to track the other loads and chargers to calculate SOC. I asked another question about that here https://community.victronenergy.com/questions/154665/cerbo-gx-calculate-battery-soc-from-multiple-shunt.html

Thanks!

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