Solar The Solar Panel Thread

[Bellbirdweb]

Hi @mikerezny and @G Daddy , here is a scenario from one of your enthusiastic pupils. What do do think??
There are two panels rated at 150W (7.5A @ 20v) with NO BLOCKING diodes and only BYPASS diodes on each panel. A MPPT controller is in use. If these two panels are connected in SERIES and one is badly shaded, the panel in full sun continues to produce at full power and current from this panel is able to bypass the shaded panel without major losses.

However, although shaded , the other panel is NOT a resistance in the full sense of the word. If Irradiance on this panel is still close to 200W /M squared, (as per link para 7.3) it will still have VOLTAGE potential of nearly the same Vm as the panel in the full sun. Although current produced will be low, say 1A or less, that means that the total output of the string would be 7.5A plus 1A at the combined voltage of both panels , say 40V in theory. So the WATTAGE from the two panels is NOT halved just because one is shaded and the MPPT controller can make use of the still available higher voltage. If this is correct, then the panels would still be producing considerably more watts than if the shaded panel was just being bypassed. A very interested student is now asking the "teachers"!!

@Boots in Action I think you are correct here. I was going from one of the video's a while back in this thread that showed the effect of shading a single cell in a panel that was connected in series vs the same scenario on a panel connected in series.

Unless each CELL has a bypass diode, then partial shading has a greater impact on panels in series than those in parallel.

Climbing up and pulling the factory fitted panels and wiring apart also gives me a headache just thinking about it.

 

[mikerezny]

Hi @Boots in Action,
it is not like that.

Basically, putting panels in series has the 'potential' to increase the voltage going to the regulator. The maximum current will be determined by the panel with the least capacity to produce current.

Putting panels in parallel has the capacity to increase current going to the regulator, The maximum voltage will be determined by the panel with the lowest voltage.

The concept is that in sunlight, the panel can be a source of energy (like a battery) but in the shade it acts more like a load (a lamp).
In shade a panel is somewhere in between. It becomes complicated. But here is my attempt to provide a simple explanation.

Consider the case when there is no sunlight on the panel. The panel is a load, BUT the bypass diode is switched hard on and the panle + bypass diode has less than 1V, the rest of the voltage is across he regulator.

In your example, most of the 7.5A flows through the diode and it will stay conducting UNTIL the panel across the diode can deliver 7.5A and switch the diode OFF. The simplest case is that the panel has to get enough sunlight on it to deliver 7.5A into a short circuit. That will switch the bypass diode OFF. Any further sunlight will start to increase the voltage delivered in series with the other panel.

I hope this helps.

cheers
Mike

 

[mikerezny]

Well Hi there @G Daddy , @mikerezny , @Bellbirdweb and @Dobbie and any others who have been following the Solar thread. The attached results of a real field test with a proper MPPT controller should answer most questions that you may be looking for. It is certainly something to sift through, dissect and review as you wish. I have tried to cover a lot of variables in this data and so make it better to compare. Thanks to @G Daddy for the different referrals to links to help me really understand the intricacies of solar panel charging in depth so they could be included in the results. Thanks are also due to @mikerezny for continuing to provide answers and recommendations on diodes and connections in SERIES.

These results confirm that Series connection to gain higher voltage for your MPPT controller to work on is the way to go . After all the interested parties have had a good look and provided View attachment 56780 their input, I should be able to list ALL the advantages of a MPPT controller with panels connected in SERIES in a more simplified form. And no, I did not get a fried brain whilst taking all these readings, but it helped when I was able to sit down and have a coldie (or two ....??) and sift through all the figures. Happy reading over the weekend.

Hi @Boots in Action,
would you be able to edit this post to clearly show before your results exactly the solar panels setup you were using?

I am still of the opinion that something is still not right.

Here is my challenge to you:
Take one of your solar panels, say the 200W one.
Given enough sunlight, that panel SHOULD produce 200W at the rated Vmp and Imp stated on the panel.
It should also deliver Voc and Isc as per the panel specification.

Now, if your MPPT controller is functioning correctly it should be able to deliver 190W (95% of 200W) into your battery.
Assume charging voltage of 14.4V, that would be 13.19A. In that case, your solar panel voltage should be close to Vmp and the solar panel current should be close to Imp.

What I am interpreting is that you have 380W of solar, an MPPT controller capable of 95% efficiency. You should be getting 361W into your batteries. But the system is delivering much much less than that.

So the challenge is to show that, for each panel, you can deliver 95% of the panel performance through your MPPT controller to your batteries.

In my, admittedly small solar panel, with Pmax = 40W panel, Vmp = 18.88V, and Imp = 2.16A, in bright sunlight, and with the controller in equalising (14.4V), I regularly see 2A or over going into the battery. Naturally, with my PWM controller, the best I can ever get will be somewhere between Isc = 2.22A and Imp = 2.16A. It seems that my controller will stay in equalising mode for about 20-30 minutes. I haven't actually timed it.
The current drops off once the battery gets close to charge, and also when the controller goes to float (13.8V).

Now winter is over there will be stronger sunlight, so I will be able to look more carefully at my panel and controller performance.

By the way, have you now got your new fancy clamp meter?

cheers
Mike

 

[mikerezny]

@Boots in Action I think you are correct here. I was going from one of the video's a while back in this thread that showed the effect of shading a single cell in a panel that was connected in series vs the same scenario on a panel connected in series.

Unless each CELL has a bypass diode, then partial shading has a greater impact on panels in series than those in parallel.

Climbing up and pulling the factory fitted panels and wiring apart also gives me a headache just thinking about it.

Hi @Bellbirdweb,
go on, don't be a chicken. You know you want to do it!

But, before you get too carried away. Is it easier to disconnect them and bring them down to do some experiments at ground level, before you install your new MPPT controller? Then when you have decided which way to go and that it is all working, you can sort out all the installation issues separately.

cheers
Mike

 

[Bellbirdweb]

Hi @Bellbirdweb,
go on, don't be a chicken. You know you want to do it!

Perhaps I do, but I have a list of other stuff that I want to fix first.

I just got hold of a 3500w inverter that I'm going to set up to supply all of the power points in the van via an auto changeover relay, set up another relay to stop the setec charging when running on the inverter, and get rid of the Jayco rats nest wiring at the batteries.

If I've got the energy after that, I might climb up there, although I get a bleeding nose when i'm on top of my 21

 

[Boots in Action]

Hi @Bellbirdweb,
go on, don't be a chicken. You know you want to do it!

But, before you get to carried away. Is it easier to disconnect them and bring them down to do some experiments at ground level, before you install your new MPPT controller. Then when you have decided which way to go and that it is all working, you can sort out all the installation issues separately.

cheers
Mike

Hi @Bellbirdweb , that @mikerezny is a good urger isn't he?? But you have to do all the work!!! And you have to have the motivation too. With all your other things to do, you are already under the pump. The hardest part is getting started, and then you do not want to stop until it is ALL finished. Good luck which ever way you go. Cheers

 

[Boots in Action]

Perhaps I do, but I have a list of other stuff that I want to fix first.

I just got hold of a 3500w inverter that I'm going to set up to supply all of the power points in the van via an auto changeover relay, set up another relay to stop the setec charging when running on the inverter, and get rid of the Jayco rats nest wiring at the batteries.

If I've got the energy after that, I might climb up there, although I get a bleeding nose when i'm on top of my 21

Hi @Bellbirdweb , just think of all the good electric things you will be able to do with all that extra power!!!

 

[Boots in Action]

Hi @Boots in Action,
would you be able to edit this post to clearly show before your results exactly the solar panels setup you were using?

I am still of the opinion that something is still not right.

Here is my challenge to you:
Take one of your solar panels, say the 200W one.
Given enough sunlight, that panel SHOULD produce 200W at the rated Vmp and Imp stated on the panel.
It should also deliver Voc and Isc as per the panel specification.

Now, if your MPPT controller is functioning correctly it should be able to deliver 190W (95% of 200W) into your battery.
Assume charging voltage of 14.4V, that would be 13.19A. In that case, your solar panel voltage should be close to Vmp and the solar panel current should be close to Imp.

What I am interpreting is that you have 380W of solar, an MPPT controller capable of 95% efficiency. You should be getting 361W into your batteries. But the system is delivering much much less than that.

So the challenge is to show that, for each panel, you can deliver 95% of the panel performance through your MPPT controller to your batteries.

In my, admittedly small solar panel, with Pmax = 40W panel, Vmp = 18.88V, and Imp = 2.16A, in bright sunlight, and with the controller in equalising (14.4V), I regularly see 2A or over going into the battery. Naturally, with my PWM controller, the best I can ever get will be somewhere between Isc = 2.22A and Imp = 2.16A. It seems that my controller will stay in equalising mode for about 20-30 minutes. I haven't actually timed it.
The current drops off once the battery gets close to charge, and also when the controller goes to float (13.8V).

Now winter is over there will be stronger sunlight, so I will be able to look more carefully at my panel and controller performance.

By the way, have you now got your new fancy clamp meter?

cheers
Mike

Hi @mikerezny , firstly I have received my fancy clamp meter and it appears great, much better than the old one I was using. Got to get used to it though. It arrived whilst I was away so was not able to use it during testing the panels. Just by chance, because I KNEW that someone would ask about data of individual panels, I have the figures. I only tested the 180W and 200W panels individually once and did not put too much importance on those figures. Why would I when I could easily get over 17A without a full 15A load on system with the panels in series??? All I could do was place a continuous load of approx 5.8A on battery for 3 hours before testing to reduce battery voltage down to 12.3V under load and see what current my MPPT controller could put back in and how fast. I am going to delve into your ideas and see what I can come up with. I will set out figures for individual panels as soon as I can. Regards

 

[Boots in Action]

Hi @Boots in Action,
that is the way I understand it.

I think I attached a circuit diagram of panels in both series and parallel in a previous post.

cheers
Mike

Yes @mikerezny , it was YOUR thread that had the diagrams of Blocking and Bypass diodes in a circuit. Sorry about reference to other member. I have taken a picture of that circuit diagram to make sure I get it right when upgrading to 20A Schottky diodes, although it should be straight forward as we agreed that my panels do not have any Blocking diodes. Just have to make sure I have the polarity correct when I solder in new ones. Will send pictures when doing this shortly.

 

[Crusty181]

Well @Bellbirdweb , now you have the data. Please refer to data sheet. A full summation will follow in the next few days in SIMPLE TERMS. I hope the data will be helpful to you, and more info on panel temp, placement, shading and wire size to come.
My MPPT controller does not have communication capability with a commuter, but all settings can be made on controller itself. There are also heaps of readings available on display. Not as dear as Epever, but around $140.00 on Ebay with a 2 year Australian warranty I thought was value to me. Cheers

Im reading between the lines there @Boots in Action that the Epever is a reasonable unit. I found a local supplier of systems that recommended them also, but unfortunately for them they didnt think it important to respond to my emails. Seems to have worked out well for me, I just took delivery of the 40amp Epever Tracer A from an eBay supplier for $162. Transaction went very smoothly and freight was pretty quick.

@Bellbirdweb This is where I got mine http://stores.ebay.com.au/trustinchina/

 

[Crusty181]

Quick (and simple) answer if you tech heads can indulge me. I have a factory glass 150w panel on the roof, and and Im about to add 2 x 150 flexi panels to join with the existing, running through a Epever Tracer A controller. All three panels will be identical in voltage and output so either parallel or series will both be an option. The controller is 40amp, max watt input of 520w for 12v, and 100v total input. I have weight issues, hence the flexi's and I have a cunning light weight plan to mount the flexi off the roof for air flow.

Im leaning toward wiring the panels in series. Series or parallel, is my question.

 

[Boots in Action]

Im reading between the lines there @Boots in Action that the Epever is a reasonable unit. I found a local supplier of systems that recommended them also, but unfortunately for them they didnt think it important to respond to my emails. Seems to have worked out well for me, I just took delivery of the 40amp Epever Tracer A from an eBay supplier for $162. Transaction went very smoothly and freight was pretty quick.

@Bellbirdweb This is where I got mine http://stores.ebay.com.au/trustinchina/

Hi there @Crusty181 , welcome to the club of MPPT solar controllers. You won't be sorry especially if you connect up your panels in SERIES. A bit of work but well worth it I can assure you. I think that urger @mikerezny has convinced @Bellbirdweb to take the plunge and connect in Series.
As you know, I did not buy an EPEVER as I did not have a need to connect it to a computer to get further details or do other settings. I bought mine - an LDSolar Dreamtime 30A from CTrade at Foster in NSW for $140 and can do all the various settings on the unit itself without resorting to a remote unit. Also, it would have been too high for the position I needed to put it.

However, I too have watched a lot of videos and done a lot of research and testing and the only other one that seemed to have TRUE MPPT performance was the Epever. There was only the one problem with the display on the Epever and that was only minor - something about the display on the unit for battery level showing too low a reading whilst battery voltage was still high. Did you see this in a follow up video of the test on video? I am sure you will be happy and get great results and it will be well worth the expenditure too. You will have to send in some test results when set up.

What sort of solar panel set up do you currently have - 2 X 150W on roof??? All my panels are portable and none mounted on roof of my Penguin.

After looking at EBAY and where you bought it, I think you did pretty well as all the prices seem to have increased markedly, especially if you want to add on the temp sensor , communication cable and remote controller unit. Please keep us informed of your progress.

 

[Boots in Action]

Quick (and simple) answer if you tech heads can indulge me. I have a factory glass 150w panel on the roof, and and Im about to add 2 x 150 flexi panels to join with the existing, running through a Epever Tracer A controller. All three panels will be identical in voltage and output so either parallel or series will both be an option. The controller is 40amp, max watt input of 520w for 12v, and 100v total input. I have weight issues, hence the flexi's and I have a cunning light weight plan to mount the flexi off the roof for air flow.

Im leaning toward wiring the panels in series. Series or parallel, is my question.

Go for it @Crusty181 , Series if you want the max out of panels. Higher voltage of 50V or so, no need to worry so much about cable losses heaps of voltage for your MPPT controller to convert to extra amps for a lot of current. I hope you have an AGM battery or two connected in parallel as you will be producing a lot of current - a virtual power house!! Just watch the connections and how the diodes are connected as there will be more than 20amps (more like 30plus!!) coming down the line with that type of connection. No blocking diodes needed if connected in series as a string, only diodes connected as bypass to help when a panel shaded or partially so. The best info I have read about the advantages of MPPT controllers was the link provided by that guru in Toowoomba @G Daddy. If you haven't read it, I strongly suggest you do before setting everything up. He has most answers, not me. I am only the "tester" of unknown outcomes!! The guinea pig you might say!!!'

 

[mikerezny]

Quick (and simple) answer if you tech heads can indulge me. I have a factory glass 150w panel on the roof, and and Im about to add 2 x 150 flexi panels to join with the existing, running through a Epever Tracer A controller. All three panels will be identical in voltage and output so either parallel or series will both be an option. The controller is 40amp, max watt input of 520w for 12v, and 100v total input. I have weight issues, hence the flexi's and I have a cunning light weight plan to mount the flexi off the roof for air flow.

Im leaning toward wiring the panels in series. Series or parallel, is my question.

Hi @Crusty181,
one great advantage of the Epever is that the regulator itself can be placed close to the batteries and this allows efficient wiring from the solar panel to the regulator and from the regulator via very short cables to the batteries.

If the correct installation spot is difficult to get to, then the remote meter can be put in a convenient location to control it, or you can hook it up to a laptop.

If you put them in parallel (450W is about 25A) you should keep the voltage drop between the panels and the controller to less than 1V total.
Otherwise you run the risk of not being able to supply enough voltage in hot conditions to get maximum efficiency.
To work correctly when one or two panels is not fully in the sun, you would be advised to put blocking diodes in series with each panel.

If you put them in series, it seems like you will be under the 100V input limit to the regulator. You need to check the Voc specification for each panel. You also need to put bypass diodes across each panel.

You will need to look at the connection block on the back of each panel to see if there are already diodes installed, and, if so, whether they are wired as blocking or bypass.

Some panels consist of strings of cells wired in series or parallel within the panel. That has an impact on the purpose of the diodes that may be already installed. Best to have a look at home many little silver threads are coming from the cell array. Any more than two and you may need to understand how this may impact on how to wire in the bypass or blocking diodes.

@Boots in Action can advise you on the best diodes to get regardless of whether you wire in series or in parallel.

cheers
Mike

 

[Boots in Action]

Hi @Crusty181,
one great advantage of the Epever is that the regulator itself can be placed close to the batteries and this allows efficient wiring from the solar panel to the regulator and from the regulator via very short cables to the batteries.

If the correct installation spot is difficult to get to, then the remote meter can be put in a convenient location to control it, or you can hook it up to a laptop.

If you put them in parallel (450W is about 25A) you should keep the voltage drop between the panels and the controller to less than 1V total.
Otherwise you run the risk of not being able to supply enough voltage in hot conditions to get maximum efficiency.
To work correctly when one or two panels is not fully in the sun, you would be advised to put blocking diodes in series with each panel.

If you put them in series, it seems like you will be under the 100V input limit to the regulator. You need to check the Voc specification for each panel. You also need to put bypass diodes across each panel.

You will need to look at the connection block on the back of each panel to see if there are already diodes installed, and, if so, whether they are wired as blocking or bypass.

Some panels consist of strings of cells wired in series or parallel within the panel. That has an impact on the purpose of the diodes that may be already installed. Best to have a look at home many little silver threads are coming from the cell array. Any more than two and you may need to understand how this may impact on how to wire in the bypass or blocking diodes.

@Boots in Action can advise you on the best diodes to get regardless of whether you wire in series or in parallel.

cheers
Mike

Hi @mikerezny and @Crusty181 , one thing I forgot to clarify: If connected in SERIES, you will still only have approx 7.5A coming down the line from the panels, but it will be at 50V or so (18 or 20V X 3 equals about 50 to 60 volts. This is well within the carrying capacity of any decent wire. However, once the MPPT controller gets involved and converts that excess voltage into extra amps (say battery/ies are only 12.5 volts - that's a difference of over 40 volts - the OUTPUT wires to the load AND the battery from the controller will need to be able to handle this extra current. @mikerezny or @G Daddy will be able to confirm whether the current from the controller feeds the load first or the battery first or both together. You need to consider this when wiring from controller to battery/load. Hope you are keeping up with all this info!!

 

[Crusty181]

Did you see this in a follow up video of the test on video?

Ive watched quite a few videos, and read a bit but I have to stop because I was frightened this info may well occupy so much of my limited brain space, and other important info may fall out the other side. I recall a video where the dude was say the Epever screen bar graph would only show half full right up to the point where the battery was fully charged. I suppose the Drifter will fill that void there, and hopefully once the system is all connected I wont need to monitor it as such, just test it every so often to make sure its all still doing whats its supposed to.

What sort of solar panel set up do you currently have - 2 X 150W on roof???

I have the one factory 150w glass panel on the roof via a PWM controller; the panel will stay put and the controller will swap out for the Epever. Im going to add 2 x additional flexi 150w panels to the roof, which are of identical specs to the existing glass panel; flexi panels are because the weight saving is significant. The potential issue with flexi panels is the inability to disperse the heat buildup from surface mounting, particularly in really hot areas. I read on here someone roof mounted flexi panels to core-flute roof sheeting but that type of roofing is only around 8mm. Ill reduce that heat issue by mounting my flexi panels on square corrugated polycarbonate pergola roofing. The polycarbonate sheet will give me an inch of airflow under the panel and ample adhesive surface area to both the van roof and the panel itself. The polycarbonate is very light weight and should bond quite well with a UV stable polymer based adhesive to both the fibreglass roof and alum solar panel.

Also, it would have been too high for the position I needed to put it.

My vans in at its biological parents getting some work done and I didnt check the available height in the cabinet before I purchased the Epever, so there's a very real possibility it may well be sideways mounted.

The best info I have read about the advantages of MPPT controllers was the link provided by that guru in Toowoomba @G Daddy

The reading and videos I seen first up stopped me dead in my tracks from launching into simply buying and adding additional panels. I would have ended up with panels of differing inputs and outputs all connected together in a confused Serial Parallel Universe and all running into a $25 PWM controller that had "MPPT" boldly and clearly emblazoned across the front, and I would have blindly thought I was kicking serious solar ar$e

I hope you have an AGM battery or two connected in parallel

I have 2 x AGM batteries connected in parallel.

 

[Crusty181]

one great advantage of the Epever is that the regulator itself can be placed close to the batteries and this allows efficient wiring from the solar panel to the regulator and from the regulator via very short cables to the batteries.

If the correct installation spot is difficult to get to, then the remote meter can be put in a convenient location to control it, or you can hook it up to a laptop.

The position of the PWM controller is about 5ft directly from the batteries. The controller is in an overhead cabinet directly over the batteries which are under the couch. With the van at the dealers, I cant check to see if I can mount the controller elsewhere, or what gauge the wire is.

If you put them in series, it seems like you will be under the 100V input limit to the regulator. You need to check the Voc specification for each panel. You also need to put bypass diodes across each panel.

22v Voc on each of the panels. I went with the largest sized controller to avoid any restrictions ... this was paramount when I made the conscious decision to get the controller before I asked all these questions

@Boots in Action can advise you on the best diodes to get regardless of whether you wire in series or in parallel.

So ...... Im assuming from that, that the configuration of blocking/bypass diodes can be modified ??

The existing 150w panel provided us with most of our power requirements on our 14 month trip, but it was borderline but we were lucky to basically have 14mth of constant sunshine. Less than perfect conditions and we'd be in trouble. On the odd times we had rain, overcast or unavoidable shade we had to get the generator out after a couple of days. Targeting full sun, solar friendly free camping positions, over shaded positions worked well for us. I find it fine to camp in the full sun, so long as I can have the awning toward the east, and therefor arvo shade which generaly works out fine. These new mods with the replacment MPPT controller and 2 x additional panels is more of a southern, inclement weather, overcast, lucked out fail safe, than a necessity. The 450w is probably over kill because we function "ok" on 150w, albiet in mostly perfect conditions. But the cost of this overkill is no much really and we dont need a lot more than what we have. If I get double the power what I got from a PWM controller and one 150w, Ill be comfortably well in front.

 

[mikerezny]

So ...... Im assuming from that, that the configuration of blocking/bypass diodes can be modified ??

Hi @Crusty181,
that shouldn't be a problem. The connection box on the panels usually have terminals, sometimes with diodes already in place. It is only probably a matter of first deciding how you want to wire your panels and then determining where to mount the diodes in the connection box.

The position of the PWM controller is about 5ft directly from the batteries. The controller is in an overhead cabinet directly over the batteries which are under the couch. With the van at the dealers, I cant check to see if I can mount the controller elsewhere, or what gauge the wire is.

5ft should be ok. Regardless of how you wire the panels, it would be best to assume you will be able to achieve 450W from the panels, which is say 430W allowing for 95% MPPT conversion efficiency. For a depleted battery, at say 12V , the charging / load current could be as high as 36A.
You want as little voltage drop as possible over that run (and good terminations at each end to handle this current). Your 40A EpSolar can terminate 6AWG (6B@S). If it was me I wouldn't mess around and I would wire in 6AWG.

A 5ft return run of 6AWG at 36A will drop 0.14V according to:http://www.calculator.net/voltage-drop-calculator.html
http://www.calculator.net/voltage-drop-calculator.html
http://www.calculator.net/voltage-drop-calculator.html
That will be good. Using 8AWG will drop 0.45V and I would want less than that.

cheers
Mike

 

[Crusty181]

A 5ft return run of 6AWG at 36A will drop 0.14V according to

Id be pretty happy with 36amps ... I have a 2.5kW inverter so Ill be able to run the microwave, iron my suit and mount the clothes dryer over the washing machine.

I should get the van back next week and ill be able to look at the wiring options. Im presuming the 6b&s is only on the battery side? The current wire is certainly not 6b&s. Cant recall how the wire is routed to the batteries, but both the controller location and batteries are next to the fridge which has a void I can route new wiring via

 

[mikerezny]

Im presuming the 6b&s is only on the battery side?

Hi @Crusty181,
Yes, I was only discussing the 5ft run from the controller to the battery.

If you want, I can make an estimate of what cable you need to go from the solar panels to the regulator after you decide whether you want to wire the three panels in series or parallel. AND an estimate of the length of the cable run.

Actually, using the website cable size estimator, you won't need me. But I am still happy to help.

cheers
Mike