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sinuous6895 avatar image
sinuous6895 asked

calculated Yield differs from Mobile App results

Hi There,

With the mobile App, I am able to read out yesterday's total yield, which is 5.49kWh as seen in the screenshot below.

1694713936197.png

I am trying to calculate this number by myself, but if I take all the stored database values, it always differs a bit.

My setup is as follows:

1. The SCC is connected via the VE.Direct port to a RaspberryPi4 with VenusOS running on it.

2. Node-Red is keeping the MQTT flow successfully alive by publishing every 30 seconds the "keepalive" message

1694714378427.png

3. Node-Red receives the by the VenusOS published messages from the solarcharger and stores them in an Influx Database. The question here relates to the values published on topic
"N/e......59/solarcharger/289/Yield/Power"

4. to not make this a Flux question, I have taken all stored yesterdays Power values and calculated them in a spreadsheet program (I hided most of the rows), to find out that the by me calculated Yesterdays yield should have been 5593.675 Wh = 5.593675 kWh which is not the same as in the mobile App shown 5.49 kWh.

1694715231997.png

F.Y.I. With a flux linear integral query, I get the same result.


Could somebody explain this difference?


Any help would be very appreciated!

Venus OSNode-REDVE.DirectMQTT
1694713936197.png (276.2 KiB)
1694714378427.png (5.2 KiB)
1694715231997.png (33.5 KiB)
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2 Answers
kevgermany avatar image
kevgermany answered ·

@Sinuous6895

You're calculating to a high level of precision, which is probably higher than the recorded values/equipment. It's also mathematically incorrect.

The data is averaged before export, whereas the MPPT will measure continuously. This will introduce discrepancies unless there's a sophisticated averaging algorithm.

Moving this to modifications space. Belongs there.

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sinuous6895 avatar image
sinuous6895 answered ·

@kevgermany Thank you for your quick response.

Why is it mathematically incorrect how I calculated the yesterday's total yield?
1694781059921.png

In this example, I have multiplied the published 0.54 Watt with the time until the next Watt value was published. The outcome in Wh is the Yield "pulled" by the SCC from 07:35:31 till 07:35:33.


With "the data is averaged before export" you mean by the SCC before it is sent out over the VE.Direct port?

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