question

mr-no avatar image
mr-no asked

Smart Solar MPPT RS 450/100 one tracker with less performance

Hello,


I have a MPPT RS 450/100 which has the problem, that one tracker does perform less well than the other. Both are connected to two identical PV arrays (each 3300W, 380V).


-screenshot-20231126-100244.png


As you can see in the screenshot, tracker 1 has 20% (60W) less performance. I already swapped the two inputs, it is always tracker 1 that works worse. Therefore, it cannot be caused by the PV arrays. In this example, the battery was not fully charged, so the device does not limit the battery current. Partial shading detection is disabled.


It is a new MPPT RS 450/100 (Batch HQ2320), which was exchanged some days ago against the same device, due to the recall because of the high failure rate problem. The replaced device did not have the problem described above and had the same output for both solar arrays. The only difference in the installation is, that the new one runs on the newest firmware V1.15.


Does anybody know, if it might be a firmware issue? Or does my device have a hardware problem and is therefore not working properly?


Thanks

Norbert

MPPT Controllers
-screenshot-20231126-100244.png (169.5 KiB)
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gloitom avatar image gloitom commented ·

I'm curious about the solution, I had the same behavior. Two identical strings and different yields.

strings.png

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mr-no avatar image mr-no gloitom commented ·

Interestingly, it is also Tracker 1 with less performance. Same as in my case. I might have found out the reason, please see my answer some minutes ago

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4 Answers
nesswill avatar image
nesswill answered ·

Hi have you seen this

https://community.victronenergy.com/questions/241677/mppt-rs-shade-performance-testing-v116-beta.html

Might help.

Dave.

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mr-no avatar image
mr-no answered ·

Thanks for the hint. Maybe it is related to the shading issues, but my panels are not shaded and I don't have enabled the shading optimization in the device.


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nesswill avatar image nesswill commented ·

Do both arrays point in the same direction at the same angle?

EDIT

and height.

PS i too have had one of my 450/100 replaced because of the recall but it's working fine.

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mr-no avatar image mr-no nesswill commented ·
Yes, both arrays are the same direction, height, angle and type. They can't be the cause. As I wrote I changed the cabling so each tracker sees now the other array and still tracker 1 performs lower than tracker 2
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nesswill avatar image nesswill mr-no commented ·
Ok well let's check all the easy stuff first.

Have you inspected the panels for leaves or dirt ect on them?

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

Hi @Mr. No,

Each tracker is connected to a 3300W array, but is only showing 300W of yield?

Do you know the reason why the MPPT is constrained?

If it is already at target absorption battery voltage, then it's normal that the strings aren't perfectly balanced, and no issue. In this case the difference is only 0.2A / 2% variation.

250/3300 = 7.5%

310/3300 = 9.4%

It would be better to see the comparison when there is no constraint and at full production.

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mr-no avatar image mr-no commented ·

Hi and thanx for asking,

It was constrained because the sky at my location is permanently cloudy at the moment. But it's precisely on these days that I'm interested in making the most out of solar energy. 60W less production may sum up to 400-500Wh each day.

The device was still in bulk mode and there was no current limit on the battery side. I have checked this. Without sun I can't test full production atm.

The device I had previously replaced due to the exchange had both trackers working equally well, compared to the new one I have now. After extensive fault analysis (I am an electrical engineer), I can rule out the rest of the system as the cause. Even when changing the arrays, it is always tracker 1 that works worse.

Could it possibly be firmware V1.15? Was there a change in the MPPT behavior? The RS450/100 I replaced with the new one was running on V1.14.

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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ mr-no commented ·

Hi @Mr. No,

We currently have a public beta v1.16b1 to improve performance if you'd like to try it.

Please enable the 'partial shading' feature when using it, and the MPPT will be more active in searching for the maximum power point. That may be enough to resolve what you're seeing here.

https://community.victronenergy.com/questions/241677/mppt-rs-shade-performance-testing-v116-beta.html

The beta itself also currently contains a bug that incorrectly reports overcurrent, but this is a spurious report and there is no issue or anything to be worried about and will be corrected in another upcoming beta.

v1.15 did include changes to tracker behaviour, but also other critical changes, so a roll back to v1.14 is not possible.

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mr-no avatar image mr-no Guy Stewart (Victron Community Manager) ♦♦ commented ·

Hey Guy Stewart,

great to get such a competent answer. Thank you.

I will try the public beta and let you know asap.

Norbert


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mr-no avatar image mr-no mr-no commented ·

Hello,

I have some new findings:

Installing the beta version V1.16 has not brought any improvement.

However, I have now measured the voltage and current at the PV1 and PV2 inputs with external measuring devices and compared them with the values displayed in the APP. For tracker 2, these values match, but for the worse tracker 1, only the voltage matches. The current is approx. 0.13A too low in the display.

I have checked this several times under today's cloudy sky with approx. 400W power from PV arrays.

I now assume that the device is not finding the optimum MPPT operating point due to the inaccurate current measurement, as more PV current is flowing than it assumes.

On the other hand, the difference in power between the two trackers may not be as great as I originally assumed, as more current is flowing and the display value is therefore likely to be too low. After a few analyses, I assume that instead of the 60W difference displayed, it is actually only approx. 20W due to the non-optimal MPPT tuning. At least with the cloudy sky at the moment.


Question @Guy Stewart (Victron Community Manager) : Does the precision of the current measurement depend on the firmware, e.g. due to calibration parameters? If yes, could it be healed by a firmware update? Or do I now have a device where the hardware current measurement is not as precise as the previous device? Is this within the expected tolerance or should it be repaired?

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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ mr-no commented ·
Hi @Mr. No,

The calibration of the CT is a good thought and a plausible theory, I'll pass it on internally and see what I can find out.

In my opinion it's well within acceptable range and I wouldn't go through the hassle of a repair, but it's also neither my decision to pursue it, or decide :)


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honu avatar image honu Guy Stewart (Victron Community Manager) ♦♦ commented ·
Hello,

Would be good to have calibration posibilities for each current/voltage sensors in settings.
My Multiplus II for example report overevaluated AC output at low loads (it seems to include its own power) and underevaluated at higher load.
I can think of some method to programaticaly correct those values, maybe have linear and curved correction, then a min / max value and a factor for curved correction.

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gloitom avatar image gloitom mr-no commented ·

In my case, battery watts is higher than PV Power!

Assuming the measurement of Tracker 1 is wrong and tracker 2 is right: Twice, tracker 2 is equal to battery watts. That would correspond to your theory of wrong calibration of tracker 1.

mppt.png

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mppt.png (104.9 KiB)
honu avatar image honu gloitom commented ·
Hello,

This graph is yours ? You got the same behavior as Mr-no ? (cause i can't see Mr-no having posted this screenshot).
Are those 20% error (160/200) constant with higher PV power ? Or are they linearly increasing ?

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mr-no avatar image
mr-no answered ·

same here, battery watts in display was 7% higher than Sum of displayed Tracker1 + Tracker2 power during my measurments today.

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honu avatar image honu commented ·

Hi,

What is the discrepancy at higher power ?

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