Victron Venux GX displays strange calculated dc values

DIY
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1

My current setup is Victron GX with Rec Q-bms connected through can bus, and a victron 500A shunt connected to the bms unit.
Other connected units :1. MP 5000/24V, 2. Victron MPPT 250/100 charge controllers

For some reason the Venus is displaying a high calculatedd dc value during charging, and subsequent low charging values. im wondering why this happens.
I have controlled the charge currents going through the main battery cable with a clamp meter and that shows significantly higher current compared to the Shunt ( infact approx the sum of calculated dc+ displayed charge current)

any sggestions to why this occurs`?

Screenshot_20250323_104733_VRM
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2

Do you really have separate loads that draw power only from the battery?
If not, disable “Has DC System”.

In your case, I believe it was a particular case when the info on the PV charger was not updated and it’s a little bit off.

Generally the PV charger value is the same (well a little bit bigger) than the DC power.
And then the DC power is split between battery, loads and internal Easysolar consumption.
At least these are the values from my system, as seen below.
I don’t have DC loads, but if I activate it, this is how it looks.
Anyway, that DC power is a little bit strange sometimes, as it’s a calculated value.
Correct or not, this is what it is…
Difference PV power ↔ DC power = MPPT efficiency.
Difference DC power ↔ Charging + AC loads = (inverter + charger) efficiency.

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3

Thanx for your swift reply, its kind of reassuring that you experience more or less the same as i do. :smiley:

4

The shunt shows current going or leaving the battery.
The shunt wont show current being used by dc loads.
DC loads are a GX calculated figure.

Is the REC BMS or the Victron shunt selected as the battery monitor?

5

There is a DIY FAQ explaining the DC box.

6

Nevertheless, I didn’t see a formula until today in order to verify the things said above in @pwfarnell tutorial.

For example, in my situation above:

  • the PV charger power is correct (1896W)
  • the battery power is correct, calculated correctly by the BMS (1427W)
  • the AC loads are correct (396W)
  • the battery monitor is the BMS
  • the grid is disconnected
  • the system is Multi RS, which also has quite exact current measurements
  • don’t have DC loads, except Cerbo, but that, at about 3W consumption, could be ignored.

So, the difference: PV charger - battery - AC loads = 73W lost in various places. This is also pertinent/correct.

From where those 1887W on DC power?
Which is the formula for DC power?

Note to self: search the scripts/binaries for the formula, unless a more knowledgeable person here knows it and is willing to share…

7

Find out the problem in my case…

When having an AIO system, like Multi RS, the charging current from panels to battery is also flowing through the inverter system because of the hardware design and, in that case, it should be ignored and then the values will be correct.

That’s not the case of MultiPlus or EasySlolar where the current for battery is from solar charger system when the grid is disconnected or not used.

Also take into consideration that the inverter(s) power (V x I) is considered into formula and the inverter(s) power is not shown anywhere on the VRM picture/flow for reference when making the calculus by yourself.
In other words we are trying to compute a figure from a screen where not all variables are shown… :wink: