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marekp asked

VRM DC current question

Can someone explain why DC current in advanced view is different from the dashboard view?

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Update.

Here is the situation from today.

This morning Sun was up and battery was discharged down to 30%.

Battery is being charged with 133A but Advanced view shows DC current at 76A

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After battery gets to 100%, Advanced view reports DC current of -65A but the actual current, measured by SmartShunt, is 8A

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I am not very confident in numbers I see on VRM.

Maybe someone from VRM team would care to explain what is happening.

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2 Answers
marekp avatar image
marekp answered ·

@Alexandra

If We look at the VE.Bus DC current numbers from the Inverter/charger point of view, than if DC current flows out of it, it is a positive value if DC current flows in to it, it is negative value.

At this moment:

Shunt DC current is 127.3A

screen-shot-2022-02-15-at-94006-am.png

MPPT DC current (battery side) is 34A + 19.2A = 53.2A
screen-shot-2022-02-15-at-94028-am.png

So, the VE.Bus DC current should be 127.3A - 53.2A = 74.1A.

Close enough. :)

VE.Bus DC current from Advanced view is +71.1A

screen-shot-2022-02-15-at-93952-am.png

Out of 127.3A, flowing into the battery,the Inverter/charger must supply 74.1A (from AC-out connected Fronius) This value is positive because current flows out of inverter/charger.

Concusion.

VE.Bus Summary in the Advanced view, is informing us about Inverter/charger situation on the AC and DC side.

It is not a bug than.


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Alexandra avatar image Alexandra ♦ commented ·
@MarekP

Neat. Learn something new everyday.

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Stefanie (Victron Energy Staff) avatar image
Stefanie (Victron Energy Staff) answered ·

Hi @MarekP,

I think it's because advanced lags a little behind. It updates only every minute or so while the dashboard updates are almost in real time.

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marekp avatar image marekp commented ·

@Stefanie

Thank you your quick response.

I think it is not it.

Look at my 24 hour graph for battery volts and apms.

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The last time the current was so negatively high was about 20 hours ago.

At the moment this -66A were shown, battery was fully charged and PV was supplying power to the house and feeding to the grid.

Advanced view constantly showing DC current well below the actual one.

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At the same time SmartSunt is registering this:

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It looks like another VRM bug.

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Stefanie (Victron Energy Staff) avatar image Stefanie (Victron Energy Staff) ♦♦ marekp commented ·
Not everything is a bug per se only because a behaviour cannot be explained.

Maybe there has been a load just for a short time and not long enough to be registered for the widget.

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marekp avatar image marekp Stefanie (Victron Energy Staff) ♦♦ commented ·

@Stefanie

This negative current in advanced view is constant.

There is no load, constant or short, that would explain this discrepancy.

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Stefanie (Victron Energy Staff) avatar image Stefanie (Victron Energy Staff) ♦♦ marekp commented ·

What is the DC box and what's the source of it's values? Another BMV or SmartShunt configured as DC-Meter?

FWIW, as far as I know DC -39.9A means that there is a charger charging with 39.9A, where the charger is not known by the System and/or DVCC. It's not a negative current going out of the system/battery but into the battery. That's how it is working in my installations. But I think your DC box is the not the DC Power box like in my screenshot. Maybe a battery or another device?

Here is an example:

A Phoenix Smart Charger IP 43 currently charging. the Dashboard displays this as negative value, but it is accounted for (charge current minus loads) in the SmartShunt left to the DC box.

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Alexandra avatar image Alexandra ♦ marekp commented ·

@MarekP

The widget in advanced view there is not the bmv reading, it it the system reading. (I could be corrected - but this is the conclusion I have alsways come to) Is that not the one from DC bus on multiplus that has no measurement of current? So more an assumption? If your system is ESS programmed then it could be power assist that is drawing from battery. I am guessing since obviously we are not seeing this real time. Dont forget each component is polled for information at different times and possibly at different rates.

The minute by minute logging is different to realtime viewing so it is possible that the graph is connecting dots and the bmv is showing the more transient power movements of power. And the update rates of each part of VRM is not the same, that combined with internet lag etc makes vrm monitoring more of an overview type thing. That is why local monitoring is needed.

And if you want to be more serious with monitoring and statistics use Grafana.

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