Solar The Solar Panel Thread

[mikerezny]

Hi @Boots in Action,
on second thoughts, I would not recommend using your fridge as a load or messing around with fuses to isolate the Setec. I would also recommend switching the battery off to isolate the Setec from the battery.
These are both expensive and necessary pieces of Penguin kit that could possibly be damaged just for the sake of using them as a dummy load. The worst that can happen if you can use a couple of spotlights is to blow some relatively inexpensive globes.

I am mainly interested in getting the most out of panels "B" and "C". - 180w and 200w respectively. Panel "A" is only 80w but very efficient.

I think the other two panels will be equally efficient once you can set up a dummy load that draws around the same current as the panel can deliver.

cheers
Mike

 

[Boots in Action]

Hi @Boots in Action,
on second thoughts, I would not recommend using your fridge as a load or messing around with fuses to isolate the Setec. I would also recommend switching the battery off to isolate the Setec from the battery.
These are both expensive and necessary pieces of penguin kit that could possibly be damaged just for the sake of using them as a dummy load. The worst that can happen if you can use a couple of spotlights is to blow some relatively inexpensive globes.


I think the other two panels will be equally efficient once you can set up a dummy load that draws around the same current as the panel can deliver.

cheers
Mike

Yes @mikerezny , I think that is good advice. I was thinking about the circuits and what fused what and that was going to be a bit tricky. So, have definitely decided to place load on battery by using spot lights, existing lights, fans for/in both fridges, radio, light charging etc. This will show as a load (and how much) on my MPPT controller and I can then regulate load to always be MORE than what MPPT controller puts in. I will also be able to note panel power (in watts) available to controller as well as panel input voltage - lots of readings available!!
But will have to leave power switch ON as otherwise no power to all outlets!! Should be okay as all other circuits for loads each carry a 10A fuse which will blow well before a 20A for the Setec.
Note that there is no panels on roof of my Penguin and all panels are portable.
Any more suggestions you can think of?? You still have NOT replied regarding my calculations if higher series voltage system is employed. Not doing it this time - have to get more info together!!

 

[mikerezny]

You still have NOT replied regarding my calculations if higher series voltage system is employed.

Hi @Boots in Action,
you slave driver, haven't you got enough out of me today?

I will try to go through those posts, hopefully over the weekend, but no promises.

I think I have a slow leak in one of the tyres on the Penguin. So I want to attend to that if the rain stops for long enough.

Have a good weekend in the "Beautiful one day, perfect the next" State.

cheers
Mike

 

[Boots in Action]

Hi @Boots in Action,
you slave driver, haven't you got enough out of me today?

I will try to go through those posts, hopefully over the weekend, but no promises.

I think I have a slow leak in one of the tyres on the Penguin. So I want to attend to that if the rain stops for long enough.

Have a good weekend in the "Beautiful one day, perfect the next" State.

cheers
Mike

Hi @mikerezny , nothing like flogging a willing horse for all its got!!! Thank you for your patience and help throughout this day!! Should have a new batch of stats for you to sift through when I get back. It is rather beautiful weather up here at the moment - sunny, cloudless skies and temp ranges for next week predicted as minimums of 10C and max of 27C. Hard to take - will think of you whilst resting in the shade with a coldie in one hand and a clip board full of figures in the other!!! Kindest regards.

 

[Boots in Action]

Hi @Boots in Action,
you slave driver, haven't you got enough out of me today?

I will try to go through those posts, hopefully over the weekend, but no promises.

I think I have a slow leak in one of the tyres on the Penguin. So I want to attend to that if the rain stops for long enough.

Have a good weekend in the "Beautiful one day, perfect the next" State.

cheers
Mike

Hi @mikerezny , no more flogging the horse today. In fact, the horse has had its load reduced and the rider has stopped using the whip too!!
Whilst packing up panels for departure tomorrow, I had a final look at electrical connections at rear of each panel. Eureka!!! A light bulb moment!! You and I were correct. ALL diodes are connected as BYPASS on ALL panels. There are none connected in series as Blocking diodes. Not needed AS ALL PANELS WERE SOLD WITH SOME TYPE OF CONTROLLER ATTACHED TO PANEL!! As you said, no blocking diodes required for single panels connected to a controller. Only needed for multiple panel hook ups. Why did it take me so long to see this ??
Whilst I can see the logic of ONE diode as bypass on each output, why are there TWO diodes in SERIES across the output terminals on panel "B" - photos 3 and 4. With a forward voltage drop of nearly 1 volt per diode, this would reduce bypass current by nearly 2 volts if panel shaded!! Why two?? Would not ONE be sufficient??? All those 10A10 diodes will be replaced with Schottky type when I get the chance. Choice of 10A or 20A ?? Will have both later this month.
Rest easy cobber. I only have the one query in this particular thread!! Cheers.

 

[mikerezny]

Hi @mikerezny , no more flogging the horse today. In fact, the horse has had its load reduced and the rider has stopped using the whip too!!
Whilst packing up panels for departure tomorrow, I had a final look at electrical connections at rear of each panel. Eureka!!! A light bulb moment!! You and I were correct. ALL diodes are connected as BYPASS on ALL panels. There are none connected in series as Blocking diodes. Not needed AS ALL PANELS WERE SOLD WITH SOME TYPE OF CONTROLLER ATTACHED TO PANEL!! As you said, no blocking diodes required for single panels connected to a controller. Only needed for multiple panel hook ups. Why did it take me so long to see this ??
Whilst I can see the logic of ONE diode as bypass on each output, why are there TWO diodes in SERIES across the output terminals on panel "B" - photos 3 and 4. With a forward voltage drop of nearly 1 volt per diode, this would reduce bypass current by nearly 2 volts if panel shaded!! Why two?? Would not ONE be sufficient??? All those 10A10 diodes will be replaced with Schottky type when I get the chance. Choice of 10A or 20A ?? Will have both later this month.
Rest easy cobber. I only have the one query in this particular thread!! Cheers.

Hi @Boots in Action,
we are slowly converging.

If you look carefully at the sub panels that have two diodes, you will see there are THREE wires coming from the cell array instead of TWO.
When you get the panels set up, grab you multimeter, you will find that the subarray is split into TWO cell assemblies, each delivering about 9.5V, which is in agreement with what you have measured.
Thus, in each of these sub panels, you have two cell assemblies wired in series, thus the three wires:

+ cell assembly - + cell assembly -

O <---- 9.5V ----> O <---- 9.5V ---- > O

|<-bypass diode->|<-bypass diode->|

O <----------------19V ------------------->O
+ output leads -

Sorry, it comes out a bit stupid, the formatting is getting screwed up.
If I get time I will make a better drawing and post it.

Does this make sense?

That is junction box for one subpanel. But each of your panels has two subpanels. The two subpanels are then wired in parallel.

cheers
Mike

 

[mikerezny]

Whilst I can see the logic of ONE diode as bypass on each output, why are there TWO diodes in SERIES across the output terminals on panel "B" - photos 3 and 4. With a forward voltage drop of nearly 1 volt per diode, this would reduce bypass current by nearly 2 volts if panel shaded!! Why two

Hi @Boots in Action,
if the entire panel is in the sun, the bypass diodes are reverse biassed (OFF) so they have no effect.
In those subpanels with ONE diode, they will never have any effect.
In those subpanels with TWO diodes, there is one diode across each of the two cell assemblies in that subpanel.
So, if one part of one cell assembly is in the sun, one bypass diode would be forward biassed and the panel output would be 9.5V - 0.7V = 8.8V. Absolutely useless for feeding into a PWM controller!!!!
There would never be any occasion where BOTH diodes would be forward biassed, since that would imply both cell assemblies are in the shade and thus the output would be 0V.

NOTE: I am only discussing the standard panels in isolation and NOT considering putting any panels, or sub panels in series.

NOW, if you then consider putting your panels or subpanels in series, then there are many possibilities where more than one cell assembly could be in the shade, and THEN, the bypass diode in each of the shaded cell assemblies would be in series.
But remember, that is only a secondary consideration. The main consideration is to get the panels set up as efficiently as possible when ALL panels are in the sun.
There are now four possibilities:
1: Standard panels, where the subpanels are wired together in parallel AND the two panels are also wired in parallel.
2: Standard panels, where the subpanels are wired together in parallel BUT the two panels are wired in SERIES.
3: Modified panels, where the subpanels are wired in SERIES, BUT the two panels are wired in parallel.
4: Modified panels, where the subpanels are wired in SERIES, AND the two panels are also wired in SERIES.

I hope this makes sense.

It has stopped raining so I am going to go outside and plant some lettuce.

Enjoy your weekend.

cheers
Mike

 

[Boots in Action]

Hi @Boots in Action,
we are slowly converging.

If you look carefully at the sub panels that have two diodes, you will see there are THREE wires coming from the cell array instead of TWO.
When you get the panels set up, grab you multimeter, you will find that the subarray is split into TWO cell assemblies, each delivering about 9.5V, which is in agreement with what you have measured.
Thus, in each of these sub panels, you have two cell assemblies wired in series, thus the three wires:

+ cell assembly - + cell assembly -

O <---- 9.5V ----> O <---- 9.5V ---- > O

|<-bypass diode->|<-bypass diode->|

O <----------------19V ------------------->O
+ output leads -

Sorry, it comes out a bit stupid, the formatting is getting screwed up.
If I get time I will make a better drawing and post it.

Does this make sense?

That is junction box for one subpanel. But each of your panels has two subpanels. The two subpanels are then wired in parallel.

cheers
Mike

Hi @mikerezny , absolutely clear and fully understood for those panels with THREE terminals and a diode across each terminal. Thanks

 

[Boots in Action]

Hi @Boots in Action,
if the entire panel is in the sun, the bypass diodes are reverse biassed (OFF) so they have no effect.
In those subpanels with ONE diode, they will never have any effect.
In those subpanels with TWO diodes, there is one diode across each of the two cell assemblies in that subpanel.
So, if one part of one cell assembly is in the sun, one bypass diode would be forward biassed and the panel output would be 9.5V - 0.7V = 8.8V. Absolutely useless for feeding into a PWM controller!!!!
There would never be any occasion where BOTH diodes would be forward biassed, since that would imply both cell assemblies are in the shade and thus the output would be 0V.

NOTE: I am only discussing the standard panels in isolation and NOT considering putting any panels, or sub panels in series.

NOW, if you then consider putting your panels or subpanels in series, then there are many possibilities where more than one cell assembly could be in the shade, and THEN, the bypass diode in each of the shaded cell assemblies would be in series.
But remember, that is only a secondary consideration. The main consideration is to get the panels set up as efficiently as possible when ALL panels are in the sun.
There are now four possibilities:
1: Standard panels, where the subpanels are wired together in parallel AND the two panels are also wired in parallel.
2: Standard panels, where the subpanels are wired together in parallel BUT the two panels are wired in SERIES.
3: Modified panels, where the subpanels are wired in SERIES, BUT the two panels are wired in parallel.
4: Modified panels, where the subpanels are wired in SERIES, AND the two panels are also wired in SERIES.

I hope this makes sense.

It has stopped raining so I am going to go outside and plant some lettuce.

Enjoy your weekend.

cheers
Mike

Hi @mikerezny , I like and fully understand the four possibilities you have set out above. I believe I will probably go for 3 or 4. But perhaps I am dumb or I have failed to explain which Panel I am referring to. The 180w panel (consisting of TWO sub panels connected in Parallel) has an Ocv of approx 22 volts at EACH panel. Isc is approx 4.3v per panel. As per my photos in previous thread (#3 and #4), there are only TWO
leads coming from back of panel to terminals in junction box. Although there are THREE connection points, the centre one is NOT connected to panel itself and appears to be a convenient connector point for TWO diodes in SERIES with each other across the TWO output terminals on either side. What has not got through to me yet is why TWO and why IN SERIES. Why wouldn't just ONE diode across the two output terminals do the job?? Unlike the other panels which have THREE terminals coming from panel and only have ONE diode across EACH output terminal. Something to think about how to explain this to "bottom of class" student when I get back.
At least your lettuce will have a chance to grow - no rain up here and very, very dry. Hope you fixed up the tyre on your Penguin too.
Slow learning follower!!

 

[mikerezny]

Hi @Boots in Action,
oops, my apologies. I completely forgot that the panels with only two wires connected to the solar cells also have two diodes.

You are absolutely correct, this is unnecessary. The only reason to have two diodes in wired series as bypass diodes would be to increase the reverse voltage handling. But one of those diodes would easily handle the maximum voltage output of the panel.

I am off to my tyre dealer on Monday to get a single LT tyre and use it as the spare.

Enjoy your time away.

cheers
Mike

 

[G Daddy]

Hi @Boots in Action & @mikerezny , My thoughts on your posts over the last couple of days, you are trying to simplify a very complex outcome, here are some links to some interesting and sometimes complex sites, and as @Boots in Action is sitting back enjoying a few cold ones he will have time to read?
http://www.pveducation.org/pvcdrom/modules/mismatch-effects-in-arrays , this is half way through.
https://www2.pvlighthouse.com.au/ca...rum calculator/solar spectrum calculator.aspx
enjoy

 

[Dobbie]

http://www.aussiebatteries.com.au/blog/common-solar-and-battery-myths-busted/


For those of us who are looking for very basic info on solar.....and I mean basic....I found this link. It could help some of us!

 

[Dobbie]

Here's another one...nice and simple.

(I'm not detracting from the in depth dialogue from @mikerezny and @Boots in Action but I think these simpler articles / explanations can answer most questions from new members)

I'm exhausted trying to keep up with those two...very passionate and knowledgeable about their subject.

 

[Dobbie]

Whoops...forgot the link!

http://saftenet.blogspot.com.au/2017/08/i-see-lot-of-very-basic-questions-in.html?m=0

 

[Bellbirdweb]

One thing all of the dialogue has done is convinced me to upgrade to a MPPT controller.

Seems a pretty simple way to maximise the capacity of your panels.

Let's see how much better it is than the standard Jayco $30 model

 

[Dobbie]

Definately better....we've got mppt on all panels, apart from the old one which has the original pms controller.

I was more than convinced about their efficiency a few years ago.

The discussion about Mppt is interesting ....but I'm concerned it's beyond the interest level of most ...but I can definately be wrong.

Keep the dialogue going and see if we get some definitive results.

 

[G Daddy]

An interesting article on PMW versus MPPT in relation to Temperature and Irradiance (sunlight), series and parallel connection.

 

[mikerezny]

An interesting article on PMW versus MPPT in relation to Temperature and Irradiance (sunlight), series and parallel connection.

Hi @G Daddy,
great informative and comprehensive article. Thanks for posting it.

I found the comprehensive treatment of the effect of temperature on panel performance really interesting.

Hi @Boots in Action,
This article gives compelling reasons for converting each of your panels so that each of the two sub panels are wired in series instead of parallel. Naturally this only applies as long as you use an MPPT controller.

cheers
Mike

 

[Boots in Action]

One thing all of the dialogue has done is convinced me to upgrade to a MPPT controller.

Seems a pretty simple way to maximise the capacity of your panels.

Let's see how much better it is than the standard Jayco $30 model

Hi @Bellbirdweb , just back from 6 days off grid and have more very interesting data for members of this forum to digest. What about a reading of 17.3A into battery , battery voltage at 13.8V, PV voltage at 30.2V with a battery load of 2.4A. More great results when I get the figures together too Best thing I ever did in buying a true MPPT controller. With 35.6ah used for the previous day including overnight, I can have that recovered in just a few hours in the morning, even in less than perfect conditions. More to come. Cheers

 

[Boots in Action]

Hi @Boots in Action & @mikerezny , My thoughts on your posts over the last couple of days, you are trying to simplify a very complex outcome, here are some links to some interesting and sometimes complex sites, and as @Boots in Action is sitting back enjoying a few cold ones he will have time to read?
http://www.pveducation.org/pvcdrom/modules/mismatch-effects-in-arrays , this is half way through.
https://www2.pvlighthouse.com.au/calculators/solar spectrum calculator/solar spectrum calculator.aspx
enjoy

Thanks @G Daddy, no internet where I go in the Connondales!! I have done lots of experiments and have lots of data for you to sift through and advise on. Just one issue is the angle of the panel to the sun. Took my protractor with me this time. One set of panels at normal full extension of supports has a set back angle of 33.8 degrees from vertical, whilst the other panel (200W) has a set back angle of 45.2 degrees. All this just adds to all the other variables. I can also confirm that temperature of panels has a fair bearing on output as they get warmer. I will be able to provide all this when I get my data together. More to come.