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matthias48 asked

ESS - Too high AC Load values

Hi altogether!

There are already some posts about incorrect AC values, but none of them with the exact same situation or the same information.

My system: 3-phase ESS with MultiPlus-II 48/8000/110-100
PV chargers:
 4x MPPT 250/100 VE.CAN
GX device:
Cerbo GX
Batteries:
4x Pylontech US5000 (1 currently out of order)
Mode: Optimized (without BatteryLife)
Grid metering: Inverter/Charger
Multiphase regulation: Total of all phases
Grid setoint: 0W
Firmware Multis: v502
Firmware GX: v3.01


Sometimes the GX device shows way too high values for AC loads.
On the example screenshots below it displays 1667 W whereas the correct value is around 379 W.

post-1.jpg

I visualize the data (from MQTT) in Grafana. But for Energy Consumption I use data from a separate ABB meter installed at the output of the Multis.

The 13,3 kW feed-in match more or less with the value shown on the grid provider's smart meter and the 379 W consumption agree with the ABB meter.

So, where does the rest of the PV energy go?

If I take the values from the GX, the calculation adds up more or less.
15 139 W - 13 299 W - 1667 W = 173 W

But if I use the correct AC Loads value:
15 139 W - 13 299 W - 379 W = 1 461 W ?!?

The deviation can also be seen on my graphs:

post-2.png

post-3.png


Yesterday (when we had constant sunny weather) the deviation began after the the batteries were fully charged and today (changing weather) it only appeared during a phase where the PV power was at maximum.

So it seems to occur, if

  • the battery is fully charged and
  • PV production is at maximum


Does anyone experience the same thing?
Battery is full, Grid value is correct, PV values seem also correct (if I look at the graph from yesterday). So, where does the rest of the PV energy go?

Thanks,
Matthias

Multiplus-IIcerbo gxESSmonitoringaccuracy
post-1.jpg (129.0 KiB)
post-2.png (281.2 KiB)
post-3.png (114.2 KiB)
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2 Answers
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matthias48 answered ·

One explanation could be that AC Load is calculated from the other values, so that the calculation adds up, and that both the PV power reported by the MPPTs as well as the reported battery power are about 10% higher than the real value.
This would explain why the deviation is most visible when the PV power is at maximum and only becomes visible when the battery charge, which is also reported too high, stops.

Could it be that both measurements have a deviation of 10% and more?

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jonofe answered ·

Load is usually calculated by PV Production + Grid Load - Battery Charging Power. As these values are measured by different devices (grid meter and MP II) they may not be synchronized very well. So these diviations can happen, thats at least my experience.

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