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florent avatar image
florent asked

Regulator victron 75/15 good input but low output ?!

Hello,

despite several topics discussing a similar problem, I have not found an answer to mine.

I have a Victron 75/15 BT regulator, a flexible 150W solar panel that I use remotely/mobile basis and a 100Ah BT LifePo4 battery. I am attaching to you in PJ the characteristics of the panel, but it delivers approximately 27V (Voc) and 5A (Isc), with the current sun at 11 a.m. in the North of France, when I measure in open circuit, therefore normal data compared to the theoretical data in laboratory.

On the other hand, I encounter a serious problem when I plug it into the regulator because the voltage drops to around 20V but the current does not exceed 3A in the best case, around 45/60W max, even with a battery at 50% discharge therefore in bulk !?

I checked the fuse, the connections and the tension and current at the regulator terminal PV screws, it is identical to that of the open circuit panel output, so no problems on the cable side either.

I suspect the regulator algorithm of doing anything and restricting the current between what it receives and the measurement I have via bluetooth.

Why does it come in at 27V and 5A at the PV regulator screws on my multimeter and it does not exceed 3A while lowering the voltage to 20V when it should be the opposite ?!?

When in doubt, I bought another new 75/15 regulator, and I have exactly the same results, so no "mechanical" failure, hence my conclusion on the algorithm.


What do you think ?


My entire installation is in Victron, I have another 100/30 regulator and a 370W panel which I of course disconnected during the tests so as not to interfere with the measurements, and I wonder if I will not be obliged to come to the conceived...


Thank you in advance.




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9 Answers
Mike Dorsett avatar image
Mike Dorsett answered ·

I would check the short circuit current from the solar module to ensure that it does produce the 6.3A in good sunlight. If this test fails, then the module is faulty.

If the module is good, then check the battery you are charging - if it is sulphated, the voltage will rise quickly when charged, and the current will also be small.

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florent avatar image florent commented ·

Thanks for your answer.


Like I have said, even if the solar panel can’t deliver maximum power because is too old for example, this isn't normal that when I plug it to regulator, the tension decrease AND the current also...

The electric rule said that when the tension decrease the current increase, it's mechanical.

So, why when I mesure the tension and current in open circuit the both decrease when I plug them to regulator ?

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klim8skeptic avatar image klim8skeptic ♦ florent commented ·
@Florent Panel Voc is not a useful indicator to panel health, as there is no load (current) being produced.

Test the panels Isc to determine the current.


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florent avatar image florent klim8skeptic ♦ commented ·
I don't understand your message... have you read my first one ?

I have already test the solar panel, 27V and around 5A without plug it to the regulator, so not the manimum but close to the max.

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klim8skeptic avatar image klim8skeptic ♦ florent commented ·

@Florent have you read my first one ?

Yes. It seems unlikely you could measure 135w, and 60w at the same moment.

"Why does it come in at 27V and 5A at the regulator on my multimeter and it does not exceed 3A while lowering the voltage to 20V when it should be the opposite ?!?"

Measure the panels Isc and report back.

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florent avatar image florent klim8skeptic ♦ commented ·

Oh, is misunderstood. When I said that I mesure 27V/5A is the same mesure when unplug the regulator, so solar panel only, and at the arrival at the regulator when I plug it. I take this mesure on the regulator PV screws to check if there are problems of connections or cable.

So the Voc is 27V and Isc 5A...

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klim8skeptic avatar image klim8skeptic ♦ florent commented ·

@Florent I keep seeing this,

When I said that I mesure 27V/5A is the same mesure when unplug the regulator

You cant measure Voc and Isc at the same moment. They have to be 2 separate measurements.

Look at this Video and report the panels measured Isc.

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florent avatar image florent klim8skeptic ♦ commented ·
Yes, I did it !


I mesure directly at the + and - plug, 27V and 5A.

I plug the solar panel to the regulator and I mesure on the PV + and - screws of regulator, same mesure, so no connections and câbles problems.

But the regulator at the output decrease 27V to 20V but also current 5A to 3A... but normally it's the opposite. When regulator decrease tension, current up !

What do you think ?

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klim8skeptic avatar image klim8skeptic ♦ florent commented ·

@Florent I mesure directly at the + and - plug, 27V and 5A.

So panel Voc of 27v @ 0a?

And panel Isc of 5a @ 0v?

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florent avatar image florent klim8skeptic ♦ commented ·

My 2 seperate mesures is 27V in full sun, and 5A in same full sun... so it's was I said 27V/5A because is impossible to mesure this 2 mesures in same time... need to change the multimeter setting and plug (to 10A for current).

It's probably because Im not english, but I try to explain that since the beginning.

Right now ?

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klim8skeptic avatar image klim8skeptic ♦ florent commented ·

@Florent Right now ?

Yes. Panel Isc at the panel looks good.

Repeat the Isc test at the mppt pv input terminals to test the cabling/fusing between the panel to mppt.


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florent avatar image florent klim8skeptic ♦ commented ·
It's exactly the same yes. So no problems cabling/fusing.
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florent avatar image florent klim8skeptic ♦ commented ·
So, have you another idea or your surprise like me ?
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klim8skeptic avatar image klim8skeptic ♦ florent commented ·
@Florent None other than check the mppt's detailed history to see the panel's Pmax for the day.
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Fideri avatar image
Fideri answered ·

@Florent

How are you doing the measurements? With my panels, you can see voltage but no current with a multimeter unless you attach a load to the panels.

F.

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florent avatar image florent commented ·

If you have a multimeter, and not just a voltmeter, you can do it if you change setting to A (DC not AC my bad) and switch red cable to 10A on the multimeter.

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Fideri avatar image Fideri florent commented ·
How can AC be for panels, not DC? I have multimeters but with clamps for current.
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florent avatar image florent Fideri commented ·

Oh sorry, DC not AC, your right.


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kevgermany avatar image
kevgermany answered ·

Going back to your original post.

The MPPT screen shot shows input of 56W, calculating the output power as voltage x current also comes to 56W.

It's normal for the panel voltage to drop when the MPPT operates. The important thing is that panel voltage stays 1V or more above battery voltage.

I don't see any evidence of 27V and 5A in your screen shot.

Looks simply as if the panel output is below spec, could be heat, could be resistance in the cables.

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florent avatar image florent commented ·

So, you need "evidence" of 27V and 5A ? If I mesure it with multimeter in Voc ans Isc and write here, isn't enough for you , you don't believe me ? You trust me more if I import pictures of my 2 mesures here ?!

It's normal that Voc decrease when you plug PV with regulator and battery, isn't a PWM, is a MPPT so it's looking for the better tension close to battery to increase current, I know it.

But if I start 27 Voc and 5 Isc, why when I plug to regulator I have 20V BUT 3A ? Normally, it's the opposite for the current, it's the goal of MPPT... This is the only question here !?


The solar panel deliver good Voc/Isc, when I plug with regulator and I mesure tension/current at the "PV regulator screws" I have exactly the same mesures, so not problem with cables and fuses BUT the current output is less than input, it's normally impossible in bulk situation...


So, do you have answer or juste need "evidences" with a picture to believe me ?

Moreover, in the same time you tell me that the specs of my panels isn't enough for my battery lifepo4 at 50% discharge but this time you have the panel picture specs in the original post...? You see that the tension of my panel is more than enough even the MPPT regulator decrease tension.


Sorry, but I really don't understand the goal to your answer...?

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kevgermany avatar image kevgermany ♦♦ florent commented ·
Sorry.


I was trying to clear up the difference between what you showed in the screen shots and what you were saying. We're here to help, but if we're not sure what you're saying it can make things worse.
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florent avatar image florent kevgermany ♦♦ commented ·
Oh sure, sorry for my previous message, this problem turn me crazy and with translation there is misunderstood.
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vicens avatar image
vicens answered ·

Tienes demasiada caida de tension en la entrada del regulador. Deberia haber unos 25v (Vmp) con condiciones ambientales buenas. El regulador no demanda tantos amperios porque la tension baja demasiado.

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florent avatar image florent commented ·

¿Tiene alguna explicación de por qué hay una caída de voltaje tan significativa? ¿Es un problema con el algoritmo del regulador o viene de otra parte?

E incluso si hay una caída demasiado significativa, ¿eso no explica por qué los amperios no aumentan en consecuencia?

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vicens avatar image
vicens answered ·

Con el mppt funcionando, tienes ocasion de medir tension en la entada del mppt y en la salida del panel solar (lo mas cerca posible)?. Que seccion de cable usas y longitud?

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florent avatar image florent commented ·
Eso sí, como indica en el post principal, los 27 de Voc y 5A de Isc, y exactamente iguales que los tornillos del panel solar en el regulador, así que no hay problemas de cables.
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vicens answered ·

Si. Ok. Pero cargando cuanto?. Tension de entrada del mppt unos 20V, y justo en la salida del panel, cuanto?

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prein avatar image
prein answered ·

Ok

Your first measurement: 27v, 0A = 0W

Your second measurement: 0V, 5 A= 0W


Mppt looks for the optimum. Apparently it's 56W at the moment. Quite normal behavior. A solar panel is not behaving as normal linear components, since it's a semiconductor..

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vicens avatar image
vicens answered ·

En los cables hay una caida de tension cuando hay paso de amperios. En el mppt llegan 20v cuando esta cargando, pero en la salida del panel sera superior, por ejemplo 25v. Esa caida de tension son perdidas. Cuantos metros de cable desde el panel hasta el mppt hay? Y que seccion de cable usas?

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vicens avatar image
vicens answered ·

otra prueba que puedes hacer es conectar el panel solar directamente a la bateria y medir la intensidad. Si te da 3 A puedes tirar el panel, si te da 5A tira el regulador.

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