question

Zoltán Vaczulin avatar image
Zoltán Vaczulin asked

Can a PV tracker go for strike?

We had a sunny day forecast. After uncounted dark cloudy days I was waiting the big harvest of fat photons. It started as it should have started, we reached 2 kW income. Nice:kepernyokep-2023-12-12-104558.png

Then some clouds were disturbing the celebration for a short time, but they disappeared soon (~10 minutes), and until sunset we had bright clean sky. But the PV power didn't return:

kepernyokep-2023-12-12-114502.pngkepernyokep-2023-12-12-173630.png

Instead of a full battery I can close this day with an experience, what I don't understand.

Once I tried to switch off the solar source for a minute, and change the only setting of PV disable/enable - without any reasonable result.

The highest PV Vmax=427.12V ( < 450V specified)

SOC% = 30%....40%

Spec: Multi RS Solar II (PMR482602020), 7 x DAH solar 450w / 62V, 10 kWh LiFePO4

Is this behavior normal?

solarMulti RS
kepernyokep-2023-12-12-104558.png (55.9 KiB)
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kepernyokep-2023-12-12-173630.png (18.4 KiB)
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7 Answers
pwfarnell avatar image
pwfarnell answered ·

There have been several reports of this type of behaviour on RS MPPT models and new firmware is being trialled. I do not know if the test firmware can be loaded into a Multi RS. See

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

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Zoltán Vaczulin avatar image
Zoltán Vaczulin answered ·

I have a feeling, but I couldn't prove it that this misbehavior is from the time, when I first switch to "PASSTHRU" mode. In passthru mode this is significant, but not exclusive. In "ON" mode it appears sometimes, but I don't have enough evidence.

Now it is in passtru mode, there is 400V on PV, but no charging of the battery. This is usual. It is a rainy day now, but usually there is 30W...100W power, when it is working well.

kepernyokep-2023-12-13-102225.png

Should I make any test? Give me a protocol, I'm in home office now.


kepernyokep-2023-12-13-102225.png (67.2 KiB)
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Alex Pescaru avatar image
Alex Pescaru answered ·

If you have it on Passthrough, why on the second picture that consumption from battery?

I will be watching this with interest, because I also have some issues with my Multi RS ( link here )

and besides this community, where you get more answers and help from passionate users than Victron technical staff, the Victron seems to have almost no technical dialog with end-users, except maybe when they can draw some feedback for what they are doing...

Of course, this is my feeling and I can be far removed from the truth... But I'm still waiting to be corrected.

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Zoltán Vaczulin avatar image
Zoltán Vaczulin answered ·

Hi Alex! :) Sorry for being miss-understandable, but of course it was "ON" in case of the original article.

I switch bettween ON and PASSTRU by day/night manually, because the battery is low now. If I leave it in ON mode after sunset, then on low SOC% it goes to a stupid cycle:

- 1: starts to recharge the battery by 10A, and feed AC1OUT - both from the grid

- 2: when it is charged a bit (not full, but only +3%...5%), it disconnects AC1IN and feed AC1OUT from the freshly charged battery

- if SOC% is low then goto 1

About Victron staff:

1: There are hundreds of "stupid" users, including system integrators spending a lot of money, closed in their special problem box, where Victron product is one element of the system only.

2: The Victron products are perfect, so the reason of your problem is a bad design/installation etc. Well, mostly. :)

3: They don't have energy read all the comments, filter out the valuable ones, but they scan this community too. Also they have a huge database by VRM. You may not know if your information is reached them.

As I see from the community, Multi RS Solar is a new complex product, out on the market with software issues. ESS support is not finished, implemented functions have bugs, and documentation still needs to be improved. Like a new mobile or car - you get the "final" firmware one year later.

I pray and I trust them to overcome this period soon. I can plug my house directly to the grid, and test settings without risk. I can report test results, if they need it. But after a while, I should use my system without serious supervision as a stable background on which I can rely effortlessly.

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Alex Pescaru avatar image Alex Pescaru commented ·

Thank you for your response and lifting my spirit... :-))

Did you tried to use the AC input control?

Meaning set it to connect AC when SOC drops below, for example, 15% and disconnect the AC when the the Bulk is finished.

At least, in this way, you can end up with a charged battery, of course from grid, if this is acceptable.

sett1.jpg


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Zoltán Vaczulin avatar image
Zoltán Vaczulin answered ·

Yes of course, I'm playing with these settings, however without permanent good result.

The goal of my system is to utilize solar power and store to the battery the rest of the solar power. If there is not enough power in battery/solar, it should extend it from the grid. My plan to come over the summer times without grid usage, and reduce the winter time payments. By this logic grid >> battery is wasting money, resource. Here we have long blackouts very rarely.

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Alex Pescaru avatar image Alex Pescaru commented ·

Yes, but in the case of no solar and low SOC, it will be a "must" charging from grid, because you have no other choice and don't want to keep batteries there.

And in order to control how much you use from grid, maybe instead of "Disconnect AC on bulk finished" you can set it as "Disconnect AC on battery voltage xx.yy V" and you can "fine tune" there (xx.yy) the minimum SOC you want, even if it's from grid.

I hope that you don't mind me "barging in" with my ideas... I've told you, I have the same hardware and maybe a little bit of brainstorming will benefit both... Sorry if otherwise. :-)

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Zoltán Vaczulin avatar image
Zoltán Vaczulin answered ·

There is a small remark in the technical specification:

Maximum PV Voltage (4) 450 V

4) The maximum PV voltage should not exceed 8x battery float voltage. If for example the float voltage of the battery is 50 V, the maximum PV voltage should not exceed 8 x 50 = 400 V

In my case the floating voltage is 54V x 8 = 432 V

My solar panel can provide 62V unloaded, so 7 x 62V = 434V , but loaded voltage is below 400V!

In "Overall history" Max PV voltage is: 431.95V


Can anyone explain how serious is remark (4) and what can cause if I slightly run over the limits?

Does it matter if I increase the settings of float voltage upper? (The theoretical limit is 54.4V)

e.g. 8 x 54.3V = 434.4V ?


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Alex Pescaru avatar image Alex Pescaru commented ·

If the batteries have BMS and the BMS will accept that 54.4, then it's OK...

Kinda....

Because if you charge them too quickly and there is a bigger difference between cells and one reach maximum voltage quicker than the others, before balancing could kick in, the BMS could throw a "high voltage" alarm for that cell and stop charging altogether.

And I have the feeling that balancing will only function on slow and lower current charging, not when the battery is still on bulk...


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pwfarnell avatar image pwfarnell commented ·
If your system gets up to 434V at Voc, is that with panels at normal temperature (20 or 25degC). Have you considered the increase in Voc at low or as you are only a few % from 450V.
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Zoltán Vaczulin avatar image Zoltán Vaczulin pwfarnell commented ·
Actually the angle of the panels are not ideal, so in design phase it didn't seemed critical.

But seeing the behavior of the PV tracker, I will disclose one panel - not because of the 450V limit.

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Zoltán Vaczulin avatar image
Zoltán Vaczulin answered ·

I made a modification on solar panel arrangement:

string1: 7 pcs >> 4 pcs, 4 x 62V = 248V

string2: 0 pcs >> 3 pcs, 3 x 62V = 186V

Logically the same power can be harvested, but the tracker starts working later because its sensitivity is from 120V.

(The plan was 7 + 7 panels, but maybe 6 + 6 will be the final solution)


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Related Resources

Mutli RS Solar Datasheet

Mutli RS Manual


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