how to wire up solar panels

[matty40s]

Puzzled I don't see how you get to a panel output of 125V with a VOC of 38V and three panels. I make it 114V and that should not worry the controll panel.

 

@emlclcy When and if you get the fourth panel I would suggest twos in parralell and then put the two pair in series.

This shows why you should really stop posting your advice on solar threads.

[WotEver]

This shows why you should really stop posting your advice on solar threads.

Secondec.

 

Puzzled I don't see how you get to a panel output of 125V with a VOC of 38V and three panels.

Then this demonstrates two points:

1. You either didn't read or didn't understand my post.

2. You don't know much about solar panels.

[nicknorman]

Puzzled I don't see how you get to a panel output of 125V with a VOC of 38V and three panels. I make it 114V and that should not worry the controll panel.

What Matty says.

 

But in the interests of educating you a bit, check out the temperature at which Voc is quoted, and the temperature co-efficient.

[Graham.m]

Then this demonstrates two points:

1. You either didn't read or didn't understand my post.

2. You don't know much about solar panels.

 

Please do explain because VOC in a solar panel spec is the maximum open circuit voltage a panel can produce,

Perhaps you might like see here http://pveducation.org/pvcdrom/solar-cell-operation/open-circuit-voltage

 

Perhaps some definitions might help you

 

Voc = Voltage open circuit - nothing attached to the panel.

Vmp = Voltage maximum power - what the Voltage would be under ideal conditions with the maximum output current

Imp = Amps maximum power. The 'I' comes from an old term "Intensity" - before Monsieur André-Marie Ampère got his name on it. In theory, Imp * Vmp = panel Watts.

Edited December 14, 2015 by Graham.m

[nicknorman]

Please do explain because VOC in a solar panel spec is the maximum open circuit voltage a panel can produce,

Perhaps you might like see here http://pveducation.org/pvcdrom/solar-cell-operation/open-circuit-voltage

But as everyone except you knows, the Voc figure has a significant temperature co-efficient.

[Graham.m]

This shows why you should really stop posting your advice on solar threads.

 

Please do explain exactly why?

[nicknorman]

Please do explain because VOC in a solar panel spec is the maximum open circuit voltage a panel can produce,

Perhaps you might like see here http://pveducation.org/pvcdrom/solar-cell-operation/open-circuit-voltage

 

Perhaps some definitions might help you

 

Voc = Voltage open circuit - nothing attached to the panel.Vmp = Voltage maximum power - what the Voltage would be under ideal conditions with the maximum output current Imp = Amps maximum power. The 'I' comes from an old term "Intensity" - before Monsieur André-Marie Ampère got his name on it. In theory, Imp * Vmp = panel Watts.

Wow, we never knew that. Anyway, perhaps your time would be better spent checking the thermal coefficient of solar cell Voc.

[Graham.m]

But as everyone except you knows, the Voc figure has a significant temperature co-efficient.

 

So please explain how that will effect the controller?

 

What co-efficient have you used for this panel

 

Using a relitavely normal constant of -0.114V/C at -10C the VOC for 3 panels in series 101.91V

Edited December 14, 2015 by Graham.m

[Chewbacka]

 

Please do explain because VOC in a solar panel spec is the maximum open circuit voltage a panel can produce,

Perhaps you might like see here http://pveducation.org/pvcdrom/solar-cell-operation/open-circuit-voltage

 

Perhaps some definitions might help you

 

Voc = Voltage open circuit - nothing attached to the panel.

Vmp = Voltage maximum power - what the Voltage would be under ideal conditions with the maximum output current

Imp = Amps maximum power. The 'I' comes from an old term "Intensity" - before Monsieur André-Marie Ampère got his name on it. In theory, Imp * Vmp = panel Watts.

Graham - You may find this of interest - http://www.homepower.com/accounting-photovoltaic-cell-temperature

On a very cold (-10c) day with bright sunlight you could see (depending upon the panels) a 4v per panel increase in VOC. So with 4 panels in series that would be over 15V.

 

Added - That might be enough to apply too many volts and destroy your controller if your design had a small safety margin.

Edited December 14, 2015 by Chewbacka

[matty40s]

 

So please explain how that will effect the controller?

 

What co-efficient have you used for this panel

Answers your own question above.

Stop advising on solar if you don't know the answers to questions like these.

[nicknorman]

So please explain how that will effect the controller?

 

What co-efficient have you used for this panel

 

Using a relitavely normal constant of -0.114V/C at -10C the VOC for 3 panels in series 101.91V

If the Voc at low temperature exceeds the controller's max input voltage it can be damaged (depending on the make). I think 1% per 3 degC is appropriate for most panels.

 

You can of course make an argument that "probably" the controller will be trying to hoover up as much current as possible from cold panels thus pulling the voltage down and that is likely to be true for most of the time. However when designing solar installations one should take a "worst case" analysis and consider that, for example, at some point the boat might be on a shore charger and so first thing in the morning the batteries are already full, then the sun comes up on a frosty morning and that's the expensive controller blown. So now you know.

 

By the way, I am not a solar expert but Matty is. But even I know that ignoring temperature co-efficients when designing stuff is usually very foolish.

[Graham.m]

Graham - You may find this of interest - http://www.homepower.com/accounting-photovoltaic-cell-temperature

On a very cold (-10c) day with bright sunlight you could see (depending upon the panels) a 4v per panel increase in VOC. So with 4 panels in series that would be over 15V.

 

Added - That might be enough to apply too many volts and destroy your controller if your design had a small safety margin.

 

Thanks I have the formules

Oh dear For some reason I had a VOC of 30 grovel apologies However I would suggest that a combine VOC for 3 panels of 125. But I would need to know more about the panel specs

 

BTW recommended 2 x 2 parrallel and the the 2 banks in series

Edited December 14, 2015 by Graham.m

[WotEver]

Oh dear For some reason I had a VOC of 30...

No you didn't:

 

Puzzled I don't see how you get to a panel output of 125V with a VOC of 38V and three panels.

[Graham.m]

No you didn't:

 

 

In the calculator

Edited December 14, 2015 by Graham.m

[Chewbacka]

 

Puzzled I don't see how you get to a panel output of 125V with a VOC of 38V and three panels. I make it 114V and that should not worry the controll panel.

 

@emlclcy When and if you get the fourth panel I would suggest twos in parralell and then put the two pair in series.

Using a coefficient of 0.114V per degree per panel.

 

Temperature of -10c

 

VOC rated at +25c which at -10c is a difference of 35C

35 multiplied by the coefficient of 0.114 = 3.99V per panel. So a 4 volt increase to give a panel VOC of 38+4 = 42V

With 3 panels in series that gives 126V which for a 125V controller is pushing your luck, and is NOT an acceptable design safety margin for me.

[WotEver]

I give up

[Graham.m]

Using a coefficient of 0.114V per degree per panel.

 

Temperature of -10c

 

VOC rated at +25c which at -10c is a difference of 35C

35 multiplied by the coefficient of 0.114 = 3.99V per panel. So a 4 volt increase to give a panel VOC of 38+4 = 42V

With 3 panels in series that gives 126V which for a 125V controller is pushing your luck, and is NOT an acceptable design safety margin for me.

 

Hence I said I would need to know more about the panel spec.

[nicknorman]

Hence I said I would need to know more about the panel spec.

Perhaps you should have said that before giving advice on how to wire the panels up.

Edited December 14, 2015 by nicknorman

[Graham.m]

I give up

 

Ah perfect one never make a mistake

[nicknorman]

Ah perfect one never make a mistake

 

One does make mistakes, however what one does not do is to offer technical advice in matters where one lacks basic knowledge and understanding.

[matty40s]

[Graham.m]

Perhaps you should have said that before giving advice on how to wire the panels up.

 

Perhaps you should have asked for panel specs controller specs oh and battery voltages. Oh think it was me that asked

 

As for advising the OP on series wiring his panels where in this thread have I advised that?

 

They were already wired in series

Edited December 14, 2015 by Graham.m

[WotEver]

 

Perhaps...

Oh for Heaven's sake, give it a rest!

 

I offered a nice gentle piece of advice that the 3 panels in series could potentially get very close to the controller's maximum voltage. You then contradicted that advice.

 

Every post since then has you either arguing your point, attempting to educate us about something which we appear to know more than you, or justifying your own poor advice.

 

I do not consider myself to be an expert in anything that's particularly relevant to this site and I am aware of the limit of my knowledge. I therefore try NEVER to offer advice that exceeds that knowledge. I suggest you try very hard to utilise a similar restraint.

 

I do hope that you no longer give advice professionally because if you do I pity the poor recipient.

 

Tony

[nicknorman]

Perhaps you should have asked for panel specs controller specs oh and battery voltages. Oh think it was me that asked

 

As for advising the OP on series wiring his panels where in this thread have I advised that?

 

They were already wired in series

 

You quite clearly had no idea about panel temperature co-efficient. Why not just admit you didn't know about it, rather than making a pathetic attempt to cover it up? You fool no-one, not even yourself I suspect.

[Graham.m]

Oh for Heaven's sake, give it a rest!

 

I offered a nice gentle piece of advice that the 3 panels in series could potentially get very close to the controller's maximum voltage. You then contradicted that advice.

 

Every post since then has you either arguing your point, attempting to educate us about something which we appear to know more than you, or justifying your own poor advice.

 

I do not consider myself to be an expert in anything that's particularly relevant to this site and I am aware of the limit of my knowledge. I therefore try NEVER to offer advice that exceeds that knowledge. I suggest you try very hard to utilise a similar restraint.

 

I do hope that you no longer give advice professionally because if you do I pity the poor recipient.

 

Tony

 

TUT tut

 

My professional indemnity is still current interestingly it has never been claimed on