Solar The Solar Panel Thread

[Boots in Action]

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.

Hang in there @Dobbie !!! @mikerezny and I are just going through the technical background of this solar thread. When @mikerezny and I, with help from others like @G Daddy and @Bellbirdweb have finished, you will have a great record of what detailed real field testing of MPPT controllers and panel connections are capable of. Thanks for your putting up with all this and also for your encouragement too.

 

[Boots in Action]

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

Hi @G Daddy , thank you for the link provided in your thread. Some great reading and comparisons there. The good thing about all that information is that it is exactly what I have recorded in field testing regarding heat losses, the advantage of SERIES connections with my panels and most importantly, the ability of a MPPT controller to really perform in duller or less than perfect conditions, particularly when able to connect up in SERIES and have up to 36 volts still available. Indeed, some of my readings have battery voltage at 13.9V, PV voltage at 34.8V, current into battery at 8.2A, load of 1.4A, PV controller temp at 21C, PV power available at 114 watts, battery temp at 31C. These details were taken at 11.00am in bright (but hazy from bushfire smoke) sunlight and a shade temp of 30C.
I was resting in the shade with a coldie in one hand and a clip board of data in the other at this moment. Hard to take!! Full data to follow.

 

[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

Hi @G Daddy , once again, your link to spectrum calculation is timely. As advised in other response, no internet where I go, but just happen to bring it up when I got back about tilt angle variation. Now, whist having time to go through all the threads by different members including yourself, I come across basically confirmation of what is said in the link!! Wonders will never cease. Also the fact that I have just received my first batch of Schottky diodes rated at 15A and 45V, I can now see that the other lot I ordered will be necessary. The next lot are rated at 20A and 60V and because I can regularly achieve more than 17A, I do not think I will be connecting any more in series as a lot of other things will need to be upgraded as well.

 

[G Daddy]

Hi @Boots in Action ,Great to here you had a good away time hope you didn't fry your brain with all the testing? waiting for your results

 

[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

Hi @G Daddy and @mikerezny , here is shot of me enjoying a coldie after taking a lot of readings of panel outputs and voltages. The other shot is of the "solar farm" generating the power for me to stay off grid for 6 days or more. Need power to run fans in fridges and out side to keep the back cool. The " little lady boss" is always happy when the lettuce and tomatoes are not frozen and I am happy when the beer is cold!!
Shots taken at approx 11.30am with shade temp of 30C, the reason I am resting in the shade. Data from my clip board is being collated and will be sent shortly. Life is great in the Sunshine State - for camping anyway!!!

 

[Boots in Action]

Hi @Boots in Action ,Great to here you had a good away time hope you didn't fry your brain with all the testing? waiting for your results

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

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.

 

[G Daddy]

Hi @Boots in Action , great set of results, am I right in assuming the connections are your 180W and 200W panels sets connected in series while each set was connected in parallel?
I noticed the float Voltage is set at 13.8V,
what is the boost Voltage setting
what is the absorption Voltage setting and the number of hours on absorption

 

[Boots in Action]

Hi @Boots in Action , great set of results, am I right in assuming the connections are your 180W and 200W panels sets connected in series while each set was connected in parallel?
I noticed the float Voltage is set at 13.8V,
what is the boost Voltage setting
what is the absorption Voltage setting and the number of hours on absorption

Hi @G Daddy , in answer to your questions:
1. Both sets of panels are still as originally manufactured ie. two separate panels hinged together mechanically and connected in PARALLEL electrically. These are then connected in SERIES with each other to give me up to 40 volts available. Could still use them separately if necessary.
2. Float voltage currently set at 13.8 volts and adjustable.
3. The charge voltage is set by battery type only and choice of three. "Sealed" was too low at 14.4 volts, so had to use "Flooded" at 14.6 volts to get closer to the optimum of 14.7 volts for AGM batteries. From my understanding of "chinglish" booklet, "A" Bulk charging is fast charging stage until full charge voltage setting is reached @ 14.6 volts. This is done at MPPT mode utilizing maximum power from solar panels. "B" boost charging occurs each time battery voltage is less than 12.6 volts and controller will boost charge one time. When the boost voltage reaches the set point (14.6 volts?), the controller will join into constant voltage charging mode (absorption ?) instead of MPPT mode and gradually reduce current. This continues for 2 hours before going to Float mode. As load and charging rates vary, the controller will not keep constant voltage charging and the constant voltage charging (Absorption?) time is accumulated until 2 hours reached, then goes to float. Unless the battery voltage drops below 12.6 volts, the controller will not start Boost charging , just keep at Float charging mode.
By the graph provided, MPPT charge is until 14.6 volts reached and Boost charge voltage is the same at 14.6 volts for max of 2 hours, then into Float mode at 13.8 volts, but can return to Boost again if battery voltage drops below 12.6 volts. Very sophisticated microprocessor in controller.

Hope this answers your questions. I think one of my charts shows this reduction in charging rate over a period of two hours. The controller does show in small display window when charging if it is in MPPT mode, Boost mode and Float mode,but have not taken too much notice. Controller also shows amp hours consumed in previous 24 hour and amp hours replaced into battery which I reset every morning. That way I am always aware of how I am going.
No need for extra panels or even extra battery with this set up. Even less than good conditions is overcome by the MPPT controller harvesting the excess panel VOLTAGE (above battery voltage) and converting it in to usable amps. Talk to you more about maybe going to all Series connections for ALL panels which would give me up to 70 odd volts in future threads.

 

[Boots in Action]

Whoops...forgot the link!

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

Hi @Dobbie , I agree with you about this link. Not too technical and straight to the point basic information for those who need it. Any person who is going to be involved with 12 volt electrics should read and understand this article BEFORE using their van and trying to go off grid. Recommended!!

 

[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

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

 

[G Daddy]

I paid $ 130.00 for a 30Amp Epever Tracer A and $14.00 for battery temp & com cable of Ebay, you need the computor program (free download) or remote module to program the controller for a wide range of settings.

 

[Bellbirdweb]

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

Thanks @Boots in Action im expecting the new MPPT controller this week.

Looking at some of the videos posted earlier in this thread, I'm looking at staying with the panels in parallel because of the shade issue.

Having fixed panels on the roof, it's quite common to have partial shade.

Not sure if the diode arrangements on the factory supplied panels, but I'm doubting the isolation would be per cell.

 

[Bellbirdweb]

I paid $ 130.00 for a 30Amp Epever Tracer A and $14.00 for battery temp & com cable of Ebay, you need the computor program (free download) or remote module to program the controller for a wide range of settings.

I ordered one of these https://www.ebay.com.au/itm/272774628898 as I needed to find one that would fit into a similar footprint as the factory fitted controller.

 

[Dobbie]

I bought a Powertech 30amp about six years ago....far more expensive then but it's still going extremely well.

Just another alternative for those moving to MPPT.

I used it initially as a fixed controller in the Swan we had at the time but then needed a smaller sized one so removed it and hooked it to the old 120 panel. I've posted before about how efficient I find the external panel but it's just occurred to me that maybe it's the Powertech controller helping things along.

and I just checked those others in eBay and am amazed that the real cheapies are labelled mppt. I know one of them, at least, is certainly not mppt as we were supplied with it with a panel....since ditched it. (It's the one with the two USBs)

(Can't seem to copy illustrations from eBay today.....apologies)

 

[Boots in Action]

Thanks @Boots in Action im expecting the new MPPT controller this week.

Looking at some of the videos posted earlier in this thread, I'm looking at staying with the panels in parallel because of the shade issue.

Having fixed panels on the roof, it's quite common to have partial shade.

Not sure if the diode arrangements on the factory supplied panels, but I'm doubting the isolation would be per cell.

Hi @Bellbirdweb , congrats on stepping up to a MPPT controller especially if it is a true MPPT. I note that you are still considering leaving panels in PARALLEL. IMO maybe you should reconsider this in the light of a link that @G Daddy referred to about which controller "PWM or MPPT". To save you going through the whole link, have a read of what it says in paras 6 (cable loss and power by series connection), paras 7.3 (overcast sky), paras 7.5 (PARTIAL SHADING), para 7.6 (cell temperature for panels on roof with limited air gap and voltage drop - see also my data on this and I have portable panels with open air flow at back!!), para 8 (MPPT controller paragraph 3), and the very last summation for MPPT controller advantages - "A" cell temps, "B" Cabling, "C" output in low light, and finally "D" if partial shading is a concern. @mikerezny also thinks this is the best way and encouraged me to go that way after reading the complete link - see his earlier thread.

You may wish to think again on set up to really make the most of your panels. The higher voltage by having panels in SERIES is superior in harvesting the solar panel power. Your concern about the diodes is noted, as you have two panels?? already installed on roof, they must be connected in PARALLEL for your PWM controller and would therefore have "blocking diodes to prevent losses if one panel is shaded. When panels are connected in SERIES there is no need for a blocking diode as the controller does this. There is however a need for BYPASS diodes in case one panel is shaded. @mikerezny and @G Daddy have provided good data and pictures on these connections.

I don't know how junction boxes for your roof panels are set up, but, if connecting in SERIES, it is an easy job to remove blocking diodes and replace them with BYPASS ( could be same ones if specs are sufficient to cover current and voltage). In any case you can buy Schottky (packet of 10) 15A at 45V or 20A at 45v for under $4.00 delivered. Because all my panels came individually with a controller, there were NO blocking diodes, only bypass diodes, albeit cheap multi purpose type rated at 10 A only. I will be replacing these very shortly because it is easy for me to achieve more than 17A at 30 volts with the panels in SERIES as per my data sheet. Best I could do when panels were in PARALLEL was 12.8A at 13v. Something to consider to really get the best out of your panels especially when shading and heat is a problem. The higher the voltage, the less problems there are, EXCEPT you have to do the modification and only use a MPPT controller!!!. Cheers

 

[Boots in Action]

I bought a Powertech 30amp about six years ago....far more expensive then but it's still going extremely well.

Just another alternative for those moving to MPPT.

I used it initially as a fixed controller in the Swan we had at the time but then needed a smaller sized one so removed it and hooked it to the old 120 panel. I've posted before about how efficient I find the external panel but it's just occurred to me that maybe it's the Powertech controller helping things along.

and I just checked those others in eBay and am amazed that the real cheapies are labelled mppt. I know one of them, at least, is certainly not mppt as we were supplied with it with a panel....since ditched it. (It's the one with the two USBs)

(Can't seem to copy illustrations from eBay today.....apologies)

Hi @Dobbie , I too had a 20A Powertech solar controller fitted a couple of years ago, BEFORE I knew a whole lot about solar power. It is a good sophisticated controller with good readouts but is still only a PWM type. I only had it fitted into the Penguin ( and the controllers on the back of the panels removed or bypassed) because I wanted to know what was happening regarding charging , current, voltage etc and it was a three stage controller too. I did not want to go out and lay on ground to try to see what was happening with the flashing lights etc on the back of the panels.

I see them on EBAY at nearly $200.00 and even more for a 30A type. For value for money, they are expensive and nowhere near as good or efficient as a good ( and true) MPPT controller. I think it is because technology has made manufacturing more sophisticated controllers so much cheaper than when Powertech produced their PWM type that their cost has remained so high. If yours is still going after this time and there is no reason to think it will not continue, you have to weigh up the value you might get by upgrading to MPPT. @Drover once said "if it ain't broke, don't fix it!!!" It all depends on your own requirements!!

Did you read through the link that @G Daddy referred me to on "Which controller - PWM or MPPT" . The info on page 7.6 talks about cell temps and how much can be lost when panels do not have a lot of air gap behind them as in panels on roofs. I would suggest that your portable solar panel gets nowhere near as hot (as it is open at the back), and also panel orientation to the sun can be optimized by moving panel to get maximum sunlight, not really possible with fixed panels on roof, not to mention the angle of panels towards the sun. Just another variable I am finding out about as I gather more info on solar charging!! Regards

 

[mikerezny]

Thanks @Boots in Action im expecting the new MPPT controller this week.

Looking at some of the videos posted earlier in this thread, I'm looking at staying with the panels in parallel because of the shade issue.

Having fixed panels on the roof, it's quite common to have partial shade.

Not sure if the diode arrangements on the factory supplied panels, but I'm doubting the isolation would be per cell.

Hi @Bellbirdweb,
regardless of whether you leave your two roof panels connected in parallel or rewire them to be in series, I would strong suggest you actually test your setup to ensure your system delivers close to the maximum single panel output when you cover each of the panels with a blanket.
However you connect your panels you will need to come to grips with the messy details of blocking or bypass diodes in order to have your setup perform optimally. Otherwise you may end up following a lot of the heard and keep buying and adding more solar and adding more batteries to keep your van supplied.

If you leave them in parallel, you will have some power loss through the blocking diodes AND you need to ensure you have minimal voltage drop across the cables from the solar panels to the regulator AND from the regulator to the battery at maximum output.

If you wire them in series, you have to add blocking diodes to ensure one panel will still work when the other is in the shade. BUT, there is no loss of power across the bypass diodes in normal operation AND the current to the controller is halved, so you can get away with thinner cable.

Solar panel voltage output is rated at 25C and reduces markedly with increases in temperature. Panels can easily reach 100C and the reduced voltage at that temperature means that even quite small voltage drops in the cabling can result in quite a deterioration in performance.

It is not impossible to have a setup where on a really hot day, no wind, and voltage drops across the cable would mean that you will not get anywhere near maximum output. In those conditions, the serial setup will still perform as long as BOTH panels are in the sun.

There is no doubt about it, (as @G Daddy stated in a previous post) this is a complex subject. But no more so than van and vehicle weights, vehicle selection, suspension, heating, cooling, refrigeration, hot/cold water, showers, plumbing, tyre loadings, hitches, WDH, electric brakes, 12V fridge wiring, AFK, awnings, dust-proofing, waterproofing, underslinging, etc, etc, etc. Only one or two more additions to the mix!

cheers
Mike

 

[Boots in Action]

Hi @Bellbirdweb,
regardless of whether you leave your two roof panels in connected in parallel or rewire them to be in series, I would strong suggest you actually test your setup to ensure your system delivers close to the maximum single panel output when you cover each of the panels with a blanket.
However you connect your panels you will need to come to grips with the messy details of blocking or bypass diodes in order to have your setup perform optimally. Otherwise you may end up following a lot of the heard and keep buying and adding more solar and adding more batteries to keep your van supplied.

If you leave them in parallel, you will have some power loss through the blocking diodes AND you need to ensure you have minimal voltage drop across the cables from the solar panels to the regulator AND from the regulator to the battery at maximum output.

If you wire them in series, you have to add blocking diodes to ensure one panel will still work when the other is in the shade. BUT, there is no loss of power across the bypass diodes in normal operation AND the current to the controller is halved, so you can get away with thinner cable.

Solar panel voltage output is rated at 25C and reduces markedly with increases in temperature. Panels can easily reach 100C and the reduced voltage at that temperature means that even quite small voltage drops in the cabling can result in quite a deterioration in performance.

It is not impossible to have a setup where on a really hot day, no wind, and voltage drops across the cable would mean that you will not get anywhere near maximum output. In those conditions, the serial setup will still perform as long as BOTH panels are in the sun.

There is no doubt about it, (as @G Daddy stated in a previous post) this is a complex subject. But no more so than van and vehicle weights, vehicle selection, suspension, heating, cooling, refrigeration, hot/cold water, showers, plumbing, tyre loadings, hitches, WDH, electric brakes, 12V fridge wiring, AFK, awnings, dust-proofing, waterproofing, underslinging, etc, etc, etc. Only one or two more additions to the mix!

cheers
Mike

Hi @mikerezny , you still up?? Good info for @Bellbirdwebb, should he go to Series connection to get maximum out of panels. When panels are connected in series, we agreed that there is no need for a blocking diode - the controller does that job for BOTH panels. The only diode needed is a bypass type connected across the outputs of EACH panel as I understand it. Should one panel of the pair connected in series be shaded, the current generated by the panel still in the sun is able to BYPASS the higher resistance of the shaded panel. After all that is exactly the way mine is set up at the moment and we had a lot of exchanges about this. I also kept copies of circuits sent by @ G Daddy which show the arrangement of a bypass diode in PARALLEL with outputs. Am I misreading this???

 

[mikerezny]

Hi @mikerezny , you still up?? Good info for @Bellbirdwebb, should he go to Series connection to get maximum out of panels. When panels are connected in series, we agreed that there is no need for a blocking diode - the controller does that job for BOTH panels. The only diode needed is a bypass type connected across the outputs of EACH panel as I understand it. Should one panel of the pair connected in series be shaded, the current generated by the panel still in the sun is able to BYPASS the higher resistance of the shaded panel. After all that is exactly the way mine is set up at the moment and we had a lot of exchanges about this. I also kept copies of circuits sent by @ G Daddy which show the arrangement of a bypass diode in PARALLEL with outputs. Am I misreading this???

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

 

[Boots in Action]

Hi @mikerezny , you still up?? Good info for @Bellbirdwebb, should he go to Series connection to get maximum out of panels. When panels are connected in series, we agreed that there is no need for a blocking diode - the controller does that job for BOTH panels. The only diode needed is a bypass type connected across the outputs of EACH panel as I understand it. Should one panel of the pair connected in series be shaded, the current generated by the panel still in the sun is able to BYPASS the higher resistance of the shaded panel. After all that is exactly the way mine is set up at the moment and we had a lot of exchanges about this. I also kept copies of circuits sent by @ G Daddy which show the arrangement of a bypass diode in PARALLEL with outputs. Am I misreading this???

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"!!