Different solar string voltages in parallel. Does that work? (no blocking diode)🌞🔧⚡🔋
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- เผยแพร่เมื่อ 30 เม.ย. 2021
- Before we continue to test the solar panels and try and find the fault, I've made a quick test with the three different panels/strings. I was always curious if I can connect them in parallel to one solar charge controller. We have three different strings with different voltages. Will one string feed current through the next string with lower voltage? See what happens.
Before you comment that I need to install a blocking diode in each string, well, you know the drill: watch until the very end ;)
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Now, this is very interesting and provides some potentially valuable information. Thank you, Andy. Well done.
Very welcome
Hi.
Yes you can combine your panels but your mppt charger will choose a lower MPP voltage so your higher voltage strings will run less efficient. The charger will pull the voltage further down, since power is voltage times current you'll get less wattage from the higher voltage strings.
I was told the same thing. I think in the case where you have these panels 2 controllers would get you the most out of the strings and you can connect them to the same battery
Yep, that's what I was thinking as well. I think it's kind of a complicated problem, as the IV curves are going to look different for each string. The results you get will be dependent on what those shapes look like, and what the MPPT controller thinks is happening. But I agree, in general the efficiency is going to be lower than running them as matched strings. I wonder how it compares to the idea of reconfiguring the strings to have Vendor A---Vendor B----Vendor C strings, so each string is matched (assuming max current ratings are the same).
@@TBL_stevennelson Adding a second charge controller will increase the total wattage only 5% - 10%, not worth the additional expense ...
@@MrSummitville I think he means have the 3rd row on it's own CC being the second one, that way you get the most out of all panels at once.
@@Prowlerook Yes, I know. I said, only a 5% - 10% increase is output. *NOT* worth the expense ...
Andy - What I've always understood is that if you put a panel (or string) of higher voltage in parallel with a panel (or string) of lower voltage, you will pull the combined two strings down to the lower voltage. The panels still produce the current they were doing before, but it is lower power, since it is at a lower voltage. So you generally don't want to put panels in parallel if they are different voltage Vmp (by more than about 5%). Similarly, if you put two panels with different currents in series, the combined panels will assume the lower current. So you want panels in series to have the same current Imp (within about 5%). That's been the rule I follow, and it seems to make sense. You were looking at the current, but to verify you would need to check the SCC power output and see if you lost some power on the two higher voltage strings due to being pulled down by the lower voltage string.
The drop in wattage in the Higher Voltage Solar Panels is much LESS THAN the additional wattage GAINED by adding String #3. You have totally missed the Moral of this Story ...
If there is a voltage drop, you have to look at the amps to see if they rise..... in the end it is all about watts, or better Wh's
If the open circuit voltage of the lower voltage panels is higher than the MPP of the higher voltage string the lower panels will provide some current, just well off their MPP.
Hi all, I think what Andy is doing is essentially correct, but this does need more testing. V=IR, everyone agrees! I believe what happens in such a situation is that, yes the overall voltage will come down a little which the mppt takes care of , ie : adjusting voltage to find mpp and therefore current output conversion to achieve greatest overall current output at the controlled voltage to battery. I believe that the controller is the throttle so to say, & that while the voltages can be all over the place with shading etc, the Controller IS the lowest path of resistance, UNTIL the battery is fully charged &/or there is no load for output of controller, AND, this is when there could be some issues of power being fed into the lowest performing string set or set’s & where diodes will help to prevent a lower performing set to take charge from the other string sets, & possibly heat up to some degree & therefore may reduce that strings life in this way, if it doesn’t burn out in a shorter time. When I use the term ‘Lower Perfoming’ set, I am referring to it’s Power/Watts because Watts are related to power at any voltage (x amperage = Watts), so I think the watts is what we need to look at, and as Andy has shown here, lower voltage strings dont reduce Amps as u hook in extra strings. Consider also, what happens when a bird walks over or sits on a panel, does this not reduce the output (volts and amps) of that string compared to the others, so I dont think it matters that greatly if ur strings aren’t perfectly matched, as the controller takes care of this to some degree, at least while it is the lowest path of resistance, the main thing is to have reasonable safety’s in place, (Fuses, cb’s, whatever). I have 4 x 250w panels on my bus roof, 2 front & 2 @ back, a series/parallel config, there is a tree shading the rear panel in the afternoons, so I see how this effects my systems ability to charge with great voltage changes from each string, but I have the same result Andy has shown us, ie: a shaded string doesn’t effect the unshaded output and still adds to the overall Watt output of the whole set going to the controller & to the batteries. If all batteries are full & controller stops charging, then there can be a power transfer to path of least resistance, ie: a lower resistance string set. Does anyone feel that this make sense? Or is incorrect?
Hi all, I think what Andy is doing is essentially correct, but this does need more testing. V=IR, everyone agrees! I believe what happens in such a situation is that, yes the overall voltage will come down a little which the mppt takes care of , ie : adjusting voltage to find mpp and therefore current output conversion to achieve greatest overall current output at the controlled voltage to battery. I believe that the controller is the throttle so to say, & that while the voltages can be all over the place with shading etc, the Controller IS the lowest path of resistance, UNTIL the battery is fully charged &/or there is no load for output of controller, AND, this is when there could be some issues of power being fed into the lowest performing string set or set’s & where diodes will help to prevent a lower performing set to take charge from the other string sets, & possibly heat up to some degree & therefore may reduce that strings life in this way, if it doesn’t burn out in a shorter time. When I use the term ‘Lower Perfoming’ set, I am referring to it’s Power/Watts because Watts are related to power at any voltage (x amperage = Watts), so I think the watts is what we need to look at, and as Andy has shown here, lower voltage strings dont reduce Amps as u hook in extra strings. Consider also, what happens when a bird walks over or sits on a panel, does this not reduce the output (volts and amps) of that string compared to the others, so I dont think it matters that greatly if ur strings aren’t perfectly matched, as the controller takes care of this to some degree, at least while it is the lowest path of resistance, the main thing is to have reasonable safety’s in place, (Fuses, cb’s, whatever). I have 4 x 250w panels on my bus roof, 2 front & 2 @ back, a series/parallel config, there is a tree shading the rear panel in the afternoons, so I see how this effects my systems ability to charge with great voltage changes from each string, but I have the same result Andy has shown us, ie: a shaded string doesn’t effect the unshaded output and still adds to the overall Watt output of the whole set going to the controller & to the batteries. If all batteries are full & controller stops charging, then there can be a power transfer to path of least resistance, ie: a lower resistance string set. Does anyone feel that this make sense? Or is incorrect?
Andy. This video needs a follow-up with the knowledge you have acquired the last 3 years. You could add that the efficiency of an installation also hugely depends on how (and when) you use the energy. Especially in second hand use of equipment this is important to keep in mind. Enjoy the "winter" down there in sunny hot Australia. Best wishes from Norway.
After watching current.
I think you missed it, but the current did go down 10% when you connected the other panel - not straight away, but as the MPPT adjusted the voltage it dropped but you said it was shading.
But that 250w panel string is losing efficiency - as its not "tapped" at the maximum power point. Yes still producing power, but you would get 10% or more more on a separate MPPT
Love the approach
New to your channel, but I like where your mind is! I have little real experience, but I think my approach would be to just keep the higher strings connected to SCC "A" and lower to SCC "B". Best of both and nice to have a backup.
Hi, I understood that there was a series diode in the positive lead to prevent the exact situation you were testing. Bob. UK
Solar panels are current devices like most solid state devices. The only problem is the lowest voltage will be the power limiting factor
before watching comment : No, well yes but losing efficiency. Depends how close the maximum power points are as it will take an point wheres its not ideal. However will you lose 5%, 15% or 50% would depend on how different the maximum power points are. but in some ways this is what happens when some are shaded anyway.
awesome test
Two things to note. It is NOT true that current follows the path of least resistance. I don't know how this (false) idea got to be so widespread. Current follows ALL paths. It is true that more current will flow in the lowest resistance path. But the current divides proportionally, and if several paths of nearly equal resistance exist, the current will be nearly equal in all paths. Second point: solar panels are not resistors, and don't behave like one. The current/voltage relationship in a panel does not even approximately follow ohms law. At any given level of illumination a panel acts like a constant current source in parallel with a series string of many diodes. When the panel is open circuited, the current generated by the photons flows right back through the panel itself, from the plus end to the minus end, through the cells (which are, as I noted, diodes.) The voltage across each diode is an exponential function of the current through the diode. If each cell has a forward drop of 0.5 volts at.0.005 amp, it will have a forward drop of 0.56 volts at 0.05 amp, and 0.62 volts at .05 amp, and 0.68 volts at 5 amps. This relationship holds for any silicon diode. When you put a low voltage panel in parallel with a higher voltage panel and don't connect a load, nearly all the current generated by the higher voltage panel will flow into the lower voltage panel. But when when you connected the MPPT controlled, it iteratively tried pulling more and more current, which lowered the voltage until it no longer flowed through the lower voltage panel, and then it continued in that direction until the voltage got low enough that the current flowed out of the lower panel as well.
Yes, I explained this wrong. Most current will go the easy way (lower resistance), some will go the harder way (higher resistance). Your absolutely right.
Just in case of the solar strings it's not the case. There is no back current into the steering with lower voltage because of the SCC connected. At the end of the video, I explained this.
@@OffGridGarageAustralia Because when your three (3) Solar Panel Strings are connected in parallel, they will ALL have the EXACT same voltage, as long as the sun is shining and there is a load. The Voc that you measured and that you talked about, as being a "problem", is irrelevant when the sun is shining and there is a load connected ...
Very cool experiment!
Thank you 🤗
If you want power out of the lower voltage string, the charge controller has to drop the voltage, so you waste some power from the higher voltage strings.
The drop in wattage in the Higher Voltage Solar Panels is much LESS THAN the additional wattage GAINED by adding String #3. You have totally missed the Moral of this Story ...
nice test thanks
Wouldn't MPPT charge controller get less power due to different maximum power points on each string?
I think all of the three strings of panels will operate at the same voltage, dictated by the MPPT charge controller, and each string will give the corresponding current for that particular voltage (according to the I V curve, for given light and temperature conditions). The only issue could be the superposition of different maximum power point curves, and the mppt algorithm could find a local maximum, instead of the global maximum, give the fact that only some of the panels will be operating at the optimum voltage, the rest being suboptimal...
Love the videos!
Also I don't think the current will be flowing backwards in one of the strings, at least not as long as the light shines on the panels.
There’s no problem in paralleling strings with different voltages ( when they aren’t that different) the only draw back is that the maximum power is limited by the voltage of the weaker string , as in parallel all voltages are the same, meaning some strings would only reach mpp with a different voltage .
Generally recommended to use the same make and type of panel in an array. Otherwise you only get the output levels of the weakest string
@@michaelbouckley4455 The drop in wattage in the Higher Voltage Solar Panels is much LESS THAN the additional wattage GAINED by adding String #3. You have totally missed the Moral of this Story ...
@@MrSummitville The moral of the story is to put as many panels as possible on your roof and if possible in a way that creates strings with voltages not too much different. But more panels is more important then them being more the same ;-)
i liked that one...!!!! i m used to smell burnt things so no worries!!!!! thanfully all stock pile of panels i bought from same solar park so they identical! BUt not for long
If the low voltage string had acted as a load to the higher voltage strings, a blocking diode in the low voltage string may have helped.
Yes, as I said at the end of the video.
Andy has conclusively proven that Clouds (shading) and night time are the most significant limitations for solar power :)
There will be no reverse current under load as long as the lowest-voltage string receives enough light to bring its open-circuit voltage up to the highest voltage strings' MPPT voltage. The only real problem here is that none of the panels will be able to operate at their MPPT since the charge controller will settle somewhere in-between at what appears to be the overall maximum power point instead of the maximum of either panel type.
Yes, that is correct. The SCC will find the overall power point of all the strings and run the panels in the best possible way.
At the end of the video I had some info about two exceptions where current could flow the other way though.
Don’t fight it.... go with the flow.....
i had a 255watt grid tie panel in parallel with 100watt panels that where in series into an mppt and seems to work ok
I believe if you use a MPPT controller there is a negative effect on the Voltage as the 2 higher power strings won't be able to produce there highest voltage to for the controller to use.
But the 3rd string adds way more wattage vs the small ( 5% ) wattage lost in Strings #1 & #2 = net GAIN !
I like the experiment but Id personally use that 32v to pick up some early or late rays vertically in the am or pm and give the system a nice trickle if solars the only means to charge that way you can bring or keep your cells at a nice healthy level when you start to turn on or off day use loads.
When we have same voltage strings connected in parallel and shade on one string. It has the same effect as attaching a lower voltage string.
Interesting parallel Solar panels .... please do other tests at different sun and shade.. i have the same questions from my East West roof panels...and just one string SSC ... greetings from Holland
An East string connected in parallel with a West string is not a problem. This was proven 10 YEARS, ago. So why test again?
@@MrSummitville do you know my situation ?? It does not work good...But i will try it now with extra blocking diodes...AND why should Andy stop doing tests ? We all learn from this..
I think your voltage dropped to the lowest string voltage in your test. It went to 99. That makes sense because if you parallel two panels with different voltages, the lower voltage is used, but you can add both strings amperage. That of course will make your total possible watts less than what you would get individually. Series would add all voltages, but only use the lease amperage of the strings which is usually also less than the individual panels would make.
The Max Power Point Voltage of the three (3) strings connected in parallel, will *NOT* always be the voltage of the lowest voltage string. In this case, the drop in wattage in the Higher Voltage Solar Panels is much LESS THAN the additional wattage GAINED by adding String #3. You have totally missed the Moral of this Story ...
3) If a full string is sufficently shaded that is equivalent resistance (impedance) is lower than the charge controler resistance (impedance).
Impedance only applies in an AC circuit
@@offgridwanabe or when current and voltage varies 😉
@@vaneay The thing is we are talking such a little bit of difference the loss is not worth chasing. You could save the same amount by a frayed wire. I just look for the fial usable product, kwh then I know what my gains or looses are.
@vaneay - You wrote - 3) If a full string is sufficiently shaded that is equivalent resistance is lower than the charge controller resistance
O.k. Andy the resistance off each panel in the lower voltage is 14 ohm each 42 ohms in parallel with the other two string of panels. The other strings are 17 ohms above each 51 ohms above at time of testing. So 16 ohms all strings in parallel resistance. Input resistance to the mppt see a resistance each moving of about 16 ohms at time of testing. Great vlog mate, really enjoyed this one. So let's say a input of much high resistance at the mppt input so maximum power transfer from the 16 ohms to the mppt. Wouldn't the doides help too?
Well I wouldn't expect to see that after all I've read. Is this Victron magic? I'm thinking maybe the app seems to have hypnotic powers as I get into watching the watt meter for hours a day lol. I would love to see this test on a good sunny solar day.. so interesting. cheers!!
What have you been reading? Solar Panels are *NOT* Constant Voltage sources like a battery. Solar Panels are more like Current Sources which can be connected in parallel, even if their Open Circuit Voltages are slightly different. Vmp is always LESS than Voc ...
@@MrSummitville awesome thanks.
Hi Andy,
You need a different MPPT on each string. That's why inverters have 2 MPPT's a lot of the time. Microconverters are the extreme example. Although i cannot see why bringing the voltage to a mean would make that much difference.
Yep, I discussed this in one of my early videos here:
th-cam.com/video/xntxzymjlxM/w-d-xo.html
Things work as expected. You tied the strings together so they will be running at the same voltage. The current will add on the way to the charge controller. Imagine the mppt curve of both string, now for every voltage add the current in these curves. That will create a new curve. The controller will find a point on that curve where it can extract the most power of the combined system. But it is not very efficient. None of the strings will run at THEIR optimal powerpoint. But both will contribute until the open cell voltage of one string is below the max power point of the other string.
It is still very efficient because ... the drop in wattage in the Higher Voltage Solar Panels is much LESS THAN the additional wattage GAINED by adding String #3. You totally missed the Moral of this Story ...
Yes
kannst du das nochmal im leerlauf ohne laderegler testen?
die module sind normalerweise rückstromfest in einem gewissen bereich
Just add the blocking diodes. Just in case. One problem less.
As long as the lowest voltage string has a voltage above your charging voltage, which I assume 48v, you are not losing much if any power. Would be a better approach to have a schottky diode at the end of each string to isolate them.
Most solar panels do already have this installed in the back of the panel.
Rewinding so I can write the numbers down.
First look, I would say you need 2 charge controllers, 1 for the 2 strings with the same VOC, the other Cc For the string with a lower VOC.
I am assuming the Imp is simular for all the panels in each stings. Can you show the lable for each panel type?
You said morning, on a west facing array, is that correct? You also said something different about shading for each string. Faint shading limits power production.
To many variables, so confusing.
There is just not enough difference 60 cell panels in parallel with 72 cell panels. But just remove one of the 60 cell panels leaving just two in that string and then you will see what you expect and that is current flowing from the 3x 72 cell panels in to the 2x 60 cell panels. I expect about 0.7V clamping voltage per cell (depending on panel temperature) so 120 cells x 07V = 84V thus in open circuit you will not see more than 84V when you parallel the 3x 72 cell panels with the 2x 60 cell panels and all (most) current from the 3x72 cell string will flow in to those two 60 cell panels in series.
Now if you were to connect that to a solar charge controller and battery is not full the solar charge controller will be able to find a max power point likely around 60 to 65V and then all current from the 72 cell panels and 60 cell panels will go in to charging the battery but when that stops the current will again flow in to the 2x 60 cell panels.
All you need to remember is that solar cells are nothing other than diodes that is also why you see an open circuit voltage as that represents the diode clamping the voltage and all current is shorted by the cell thus solar charger reduces the voltage so that current flows in to battery instead of being wasted in to solar cell.
Voltage on each string will be essentially be the same when they are tied in parallel. This might move the maximum power point mean point depending upon the wattage availability of the individual string, which changes constantly as the variables which influence power production from each panel. In other words, your results will be highly variable under natural lighting conditions, which might lead to erroneous assumptions rather than concrete results.
That doesn't really happen, voltage is averaged while current sums up. Putting in parallel doesn't have exactly the contrary effect of putting in series.
6:00 I'm interested to know if you have to clamp on the ammeter in the same orientation, meaning if you flipped it over, would it read a negative? I suppose you would manage that by having the readout face the output of each of the panels.
Interesting, I thought keeping same number of cell for each panels you can't go wrong. But that different, I was thinking the diode is protecting the reverse. Is those panels ok now (you know that last week)?
Andy has still not adequately tested the bypass diodes at working voltage and current. I doubt even a solar panel tester will find a fault like that, (if that turns out to be a problem) even under load, and or in sunshine. Also it’s not good mixing different panels. Andy should test another 6 of the Sunteck, and try those with the 3 on the roof. Maybe migrate odd panels to another roof with another controller, even a PWM, if that produces more power
@@michaelbouckley4455 If the budget is unlimited, then your suggestion is appropriate and reasonable. If the budget is tight, you do what you gotta do, to getter done.
The lower voltage string will bring down the voltage of other strings as in the "nodes law" all voltages are the same in a parallel circuit.
This will bring the maximum power point off to the left on the MPPT curve of the two other strings matched in voltage and they will not deliver their maximum power. But they will deliver more amps as the point on the MPPT curve get closer to Isc.
More amps with low voltages in the wires mean fire danger
@@zarbonida no because Amps can not go over Isc and wire are sized to accept more than Isc (else they would burn when testing short circuit current of the pannel ...)
@@vaneay dont't forget distance and hot temperatures in Australia
@@zarbonida STILL not not a problem ...
The problem is mostly in trying to find the MPP. Less of a problem using old tech PWM charge controllers, but MPPT isn't great because there exists no common max power point between different strings.
The drop in wattage in the Higher Voltage Solar Panels is much LESS THAN the additional wattage GAINED by adding String #3. MPPT has no problems with these parallel-connected strings. You totally missed the Moral of this Story ...
2 panel series 340+380 to 40A mppt at 12v battery. My mppt pick one panel and when I disconnect and reconnect the connectors or solar wire in mppt it’s start working with both panels. What to do now? Volts and amps are little different
Can we combine (serial and parallel connections) two strings 45 VOC (9 Amps) with another string 48.5 VOC (10 Amps)?
I have two strings of 500w solar panels going to two different charge controllers. I want to add another string on the roof I can add 600w going to a third charge controller but charging the same battery bank. Is 600w ok when the other two are 500w or do the third string need to be 500w as well? Thanks!
Andy, a quick question. Given your experience, garnered since making this video, when discussing solar panel strings on each side of the roof.
My question- using a combiner, why can’t I feed both strings to the combiner?
I know that the roof side, facing east, will generate a greater voltage, than the string on the west-side of the roof. East-side will come up first, but the west-side does come up, on,y later. The adverse is true for the afternoon.
Your insight please?
1. panels in series will be limited by the worst performing panel.
2. Worry about watts, amps and volts just need to be at a level your equipment can work with. Remember Watts is just amps x volts
3. run in series to get to the minimum voltage required, then in parallel to achieve your desired highest amperage, your MPPT will do the rest
You can think of your strings (3S) of panels as basically 3 individual panels in parallel, your voltage with panels in parallel won't be affected by each other, you'll read the highest voltage supplied by any of the panels and a SUM of the AMPS, the oposite is true of panels in series although in series your output will be limited by the worst performing panel in the string unlike in parallel.
Sorry resurrection of an old video, but how about putting pannels in series of different volts?
So basically you could combine 1 of each type in 3 separate parrel circuts?
I know the off grid garage is beyond this setup nowadays
In theory, different voltage is OK as long as the current is the same (or very close). I doubt you will find that though. Higher voltage usually means larger panels with more power output and therefore higher amps.
It's not recommended doing that, so, always use same panels in series.
I'm pretty sure all solar panels have diodes installed so the batteries can't backflow at night thru the panels.
The mppt controller pulls the voltage down enough to allow the maximum current & voltage combination necessary to get the max power out of the array.
For example, if the lowest string voltage was 100 volts and the rest of the strings were 120 volts... The charge controller would keep pulling more current until the entire array voltage was lower than 100 volts.
It would keep pulling more current until the power point reached the maximum.
You are mixing up bypass diodes and blocking diodes here.
I made a video a while back and explained the important difference: th-cam.com/video/J9jqUwOdnEI/w-d-xo.html
I've been doing it for 2 years now and all is well. I had 8 250w panels and then added 4 330w panels, and then added 3 445w units and all is well so far.
As long as they have the same voltage, there is no problem.
Thanks for sharing...
@@OffGridGarageAustralia Andy, not even close....The 250w have 35v, 330W 40v and the 445W 49.7v. Remember that the higher panels have to come down to the lower ones. Someone told me one day it's a fire risk, but after 2 years, not even a spark
@@Domingorparedes Oh, that's not good. The higher voltage panels could feed power though the lower voltage panels. If you use blocking diodes for your strings, what happens if they fail? This person was right, it could be a fire hazard...
Well, just to test your theory, I connected the 445W 49.7v Jingli panel to a 12.6v car battery directly with no C.C. and voltaje never exceeded 14.3 at the terminals.
@@OffGridGarageAustralia Fire risk is increased, but fire risk is always present, if the diodes fail internally, even under balanced conditions of equal voltages across parallel arrays = fire.
I think having all 3 strings connected will drop the overall load voltage, making the maximum power you can get from the panels lower over all during peak output.
The drop in wattage in the Higher Voltage Solar Panels is much LESS THAN the additional wattage GAINED by adding String #3. You have totally missed the Moral of this Story ...
hellou! I comment as a beginner but i was wondering that in your test there was a s.c.c. probably requiring amperes and watts to fill the battery... but what if the batteries are full and the s.c.c. decreases the incoming current?
Sir Andy I have 6 545watts in series and I have also 5 320 watts .I'm using a hybrid inverter 5.5,kw..since my panel has different specs...it's alright to separate the 5 320watts with another mppt charging the same battery with the hybrid inverter?
but what happens when the battery is fully charged and the charge controller no longer draws energy?
I asked him several times same question.
He always said there is no problems
@@zarbonida because of this problem and different alignment, I use 2 charge controllers
Just watch until the end of the video...😉
@@OffGridGarageAustralia yes, OK. 👍🏻
@@zarbonida When the Charge Controller no longer needs any amps, then what do you think happens?
Wouldn't the by pass diode prevent the current from entering the pannels with the lower current?
Defiinitely, if the panel has it. Most modern panels have it to protect against back current.
Can I have two separate strings of 5 solar panels one in series and one in parallel, going to different charge controllers but charging the same battery bank?
Yes, absolutely. As long as these different solar setups are connected to different charge controller, that will work just fine.
Your mppt controller is finding the maximum power point for all strings. So with 2 strings it picks 100v and with three it picks 95V. You lose power from the 2 higher voltage strings when connecting the third. It is safe to parallel strings like this, but you don't get the maximum power.
How much do you lose though? 1%? 2%?
@@OffGridGarageAustralia So easy to calculate. 95V/100V is 95% so you lose 5% on each of the higher voltage strings.
Apparently there was a load on the panels when you did your test as they were sending current somewhere. If you consider the load as a resistance in parallel with the panels, the current would flow from each panel as long as the voltage drop across the load was greater than the voltage of the "weakest panel". If there was no load, wouldn't the panels act just as batteries of differing voltages would when connected in parallel. The higher voltage panels should pass their higher voltage to any other panels connected in parallel so the lower voltage panel would be subjected to the voltage of the highest panel. I have no idea how much over voltage a panel can tolerate. Considering that shading produces voltage and current fluctuations in connected panels all the time, perhaps it isn't an issue unless the voltages greatly exceed the rating of a particular panel? The by-pass diodes incorporated in modern panels may help reduce significant current from back-feeding thru the panel as well. I am a retired school bus driver, not an electrical engineer so don't claim any expertise except for what I have learned from Andy.
You are correct, that the diodes internally in the panels will stop the back-flow of current. If they burn up, under ANY CONDITION (balanced or imbalanced) the result is still catastrophic failure. Clouds and sun angle will always vary the imbalance, so less risk than CONSTANT imbalance.
What is the App you are measuring
Volage Amp watts
am New
I have 2 arrays
150v producing-A
60V profducing -B
I want to get 210V combined to give
to my Growatt 5kw
Very interesting and thorough analysis. Well done.
If you measure the voltage input to charge controller, I think the number should be the lower voltage string voltage. So it's the work of charge controller.
The Voltage at the Max Power Point with all three strings connected in parallel, will *always* be somewhere between the highest Vmpp and the lowest Vmpp of each of the 3 strings connected individually ...
If you had 8 300 watt panels wired in parallel facing east and 7 300 watt panels in parallel facing west and the two banks wired in parallel to the charge controller would the bank opposite the sun bring down the bank in the sun
10:33 And 3. If SCC is disconected from solar panel network!
Question about a JP21-19/900 - 72VDC, 900w 1.2HP, 62ft, 92GPM, Solar Water Pump with MPPT Controller - I have 4 x 270watt @ 35.5v Solar Panels. Will the controller handle 142 volts coming in and deliver the required 92v if connected in series?
Or will I have to connect 3 panels in series and 1 panel in parallel to them?
Or possibly 2 pairs of panels in series and then connected in parallel?
I would like to use all 4 panels if possible???
Thank You for your expertise.
OK - I just mounted 2 of the 270w panels. I just tested with a voltmeter. On a cloudy drizzly day like today each is putting out 40vdc. I think this is VOC, right? So, with these panels and my controller, how do I get 900w to1000w and the less than 150v needed for the controller. Only 3 panels in series would give me the voltage, but NOT the amps.
That's my ignorant dilemma. ????
With all four (4) of your Solar Panels connected in SERIES, I believe that you have a Voc problem! So, use two (2) SETS ... Set #1 = 3 Panels in Series + Set #2 = 3 Panels in series. Then connect Set #1 and Set #2 in parallel into the controller. Four (4) of your Solar Panels all connected in SERIES is "bad match" for your MPPT controller.
37,1V & 36,1V can be combined in series?
Your observations overlook a catastrophic problem. When the battery is full or the SCC is otherwise offline, the lower voltage string will have to dissipate an enormous amount of power from the higher voltage strings. At best, the lower voltage string will rapidly degrade and produce mere microamps of current after 1-3 years. Alternatively, a solder joint in the low voltage panels will melt and go open circuit after 30 minutes or so with the battery full and strong sunshine. At worst, the panel backing film or wire insulation will catch on fire, melt onto your roof and burn your garage down (unlikely given your metal roofing, but a potential concern for wooden homes).
I speak from experience. I had a couple small 18V 100W panels wired in series then short circuited for 3 years. This melted the MC4 connectors and killed both panels. You can physically see melted and migrated metal droplets on the individual cells where the tiny current collector finger wires are supposed to be.
Producing photovoltaic electricity is endothermic, but forcing current into a panel is exothermic.
But a "... couple of 18 Volt 100 Watt Solar Panel wired in series ..." can only generate 5 to 6 Amps. You had 100% JUNK MC4 connectors, if they cannot handle 5 amps ...
Thanks Howard. Did you watch the video until the end? 😉
hello friends, if i connect a 30 volt panels parallel to 37 volt will it work efficiently? thanks
Wouldn't the higher voltage strings voltage drop even if the amps stay the same?
In that way it would produce less power than if it was standalone.
The drop in wattage in the Higher Voltage Solar Panels is much LESS THAN the additional wattage GAINED by adding String #3. You totally missed the Moral of this Story ...
So the MPPT charge controller operates the load, in this case the solar array, at the maximum power point. If you connect panels of different VOC, it will still operate the entire array at MPP for the system as a whole. This will probably be sub optimal for panels which show different voltages but there will never be any current flow between panels.
If you had 3 charge controllers, and you connected one to each of the 3 strings, each string would then be operated at MPP and you would get the maximum current from the array.
There certainly can be current flowing between parallel-connected solar panels ...
@@MrSummitville Can you please explain how that's possible ?
Hallo
What ist besser, 13 Paneeles ost and parallel 13 north oder 13 east and 11 nord in line?
There is alot to learn from this experiment. There must be balance in the force.
Adding a 36 cell, current 8 amps? ( the BDL current) 160 watt panel to string 1, would go a long way to balance your over all system.
Even a standard 100W, 18V 36 cell, 6 amp addition panel to string 1would improve you system balance alot. Assuming bypass diodes are working. String 1 becomes 4 panels in series.
String 1 (BLD) is pulling strings 2 and 3 far far away from their max power point. String 2 pulled string 3 away from it's max power point.(Shading?). String 2 and 3 pulled string 1 from it's max power point.
It a tug of war.
No wonder the charge controller is confused. And your not getting the power expectations.
I would like to see this experiment repeated with full sun. To eliminate the Independent variable of shading.
But, measure each string separately for max power Imp and Vmp, just like you did in this video. You missed measuring string 2 all by itself in this video. I want to see if string 2 and 3 are simular enough to put in parallel, they shoud be, hard to tell when shading is a factor.
An extra panel may be cheaper than 2 charge controllers. Dedicating 1 cc to string 1, and another to strings 2 and 3. Is the best method. If the current rating between string 2 & 3 is different you may need 3 charge controllers. An ISC measurement for all strings would help to understand the issue.
I don't know this for sure, but other people say parrelled panels sometimes work better than stringed panels when shading is a large problem.
Well done experiment my young padawan!
Of course you can connect different voltage panels. No 2 panels are exact anyway. Just keep them close in voltage.
Each voltage seeks the path of least resistance going out and then. each seeks its own source on the return path
What app do you use to record you phone status? Liebe Grüße aus Braunschweig
what is name of app you Use?
Blocking diods prevent current from flowing into the panels.
Yeah, but not necessary
Try putting some diodes. ☺️
That MPPT must be going karaazy there, man, throwing watts out left and right like crazy; poor fellow lives in Heat, constantly having to convert 120 VDC into 53 VDC, why? am i missing something? bet its fan never stops when the Sun is out?
👍👍
And ... what if the SCC is not connected, but the parallels are still connected to each other? May be the current flows from the high voltage string to the lower? hummm... I'm just thinking...
I think I'd use a separate charge controller per string!
And keep the voltage below 100!
@@michaelbouckley4455 depends on the charge controller
The additional expense of One-Charge-Controller-Per-String can *NOT* ever be cost-justified by the very small 5% - 10% increase in total wattage that you would see ...
@@MrSummitville well that would depend on the different sizes voltages and amperage is of solar panels that you have if you have a string of 100 watt a string of 200 watt the string of 250 and a string of 310 it would be highly cost-effective to use separate charge controllers for each otherwise you would only receive the maximum amount of power that your smallest string of panels could put out
@@recoblade1465 But Andy does NOT have 4 strings conisting of: 100W + 200W + 300W + 400W. Andy would see only a 5% - 10% increase with 3 Charge Controllers vs Andy's single Charge Controller. Andy cannot cost-justify buying more two more Charge Controllers for such a small amount of wattage, not ever ...
Sir.. I have 60W 2 panels (voc-22v, vmp 17.2v) and 195w one panel (voc-45v vmp-36.6) .. Can I use 60w panels series and parallel with 190w panel for 24v system ?
*with inline 10A blocking diode
If you use a blocking diode, yes you can.
@@OffGridGarageAustralia what is the best SCC for this system ? mppt or pwm
Blocking diodes. Should have measured voltage with all strings connected.
put diode 5amp each string to prevent reverse current flow
There is no reverse current though...
Predictable results. The strings are not very different. The MPP-s were just a little bit moved from their absolute maximums, check IV-curve for solar panels. About reverse current - can not be for such low voltages, the solar cells are diodes, reverse can only occur if they are damaged.
Never forget 3 panels in series will go down if 1 panel is shaded.
3 panels in parallel will become 2 panels in parallel if one panel is shaded.
There are mppt cc that can handle paralleled arrays, and you will need bigger wires, a boost dc to dc converter can up the voltage to your high voltage battery.
Another option is to add an ac inverter to the paralleled array then an ac to dc charger.
I don't know if your cc can handle the current from a paralleled array.
Can you cut down that tree, or top it to lower its height. "Top it" means to cut off the top. A technique to lower the height and make most trees to spread out. Not all trees can be topped.
Move the array to somewhere there is less shading.
The trees are over 100 years old and will not be touched!
@@OffGridGarageAustralia I fully agree, I live in a wooded area, where I am so shaded with trees I can not top or cut down. The site survey I have been doing is showing the direct sun I will get is from solar noon to 3 pm at best in the summer. My property is not very compatible.
What charge controller are you using? Your voltage is alarming and you need a huge charge controller! 270V
Only if all three strings were wired in series with each other not in parallel
@@mikebarry229
Not sure I understand. If you’re running them in Series your way over the voltage! If you run them in series parallel, less voltage but you’re still way too high. I have 250/100 Victrons.
He was wiring the 120v strings and the 110v string in parallel . Why do you find it alarming ?
The Mpp voltage of the different strings would be more important than the OCV . ? I like your curiosity Andy .
Any Voc that is below the Vmpp would be VERY important ...
@@MrSummitville Yes but we know that's not the case here. I meant the mppv of the different brands may be so close is why it doesn't back feed. He showed us the voc .
@@onthelake9554 My statement is applicable to *ALL* cases. Your original statement is ONLY applicable to Andy's design - which you did not make clear. Other people read these forums and they need to know how this issue may affect their design ...
@@MrSummitville Agreed.
@@MrSummitville And to those of you seeking design advice , this is not the place . This IS the solar experimental garage for adults only , don't try this at home , batteries not included.
Is there a problem if the volt or ampere is different on the panels or everything is fine. Sory no english cant understand video 😟
Voltage of the strings should roughly be the same if you parallel them. Amps don't matter in this case as they will just add up.
@@OffGridGarageAustralia thx u soo much
Why don't you put one of each type of the panels in one string starting at GND with the lowest panel voltage to prevent the bypass diodes from kicking in? This would create three strings with the same output voltage. According to your schematics connect them in a horziontal row with 0V on the right hand side instead of the vertical structure.
In series, you should match the Imp ( amps ) of each type of solar panel ...
In theory, that's a good idea, if you place the lower voltage panel in the opposite part of the day as opposed to the other 2 higher voltage panel arrays, but most charge controllers will limit voltage at 240V. Three arrays connected in series (his 3 arrays) would produce up to 310V approxiamtely - too much for the CC.
WIth MPPT charge controller the voltage is up and down with any string depending on sun conditions if you were to connect directly to battery with a different panel configuration then maybe you would have a feedback condition IMHO but what do I know that is why I watch Andy to see his test results. I always use matched panels to feed each charge controller.
Good experiment. I have a string of 10, 250w panels (37 volt and 9 ampere each maximum). The entire string reach 350 volt. Can I add another string in parallel with different panels (say 6, 300 watt, 60 volt, 5 ampere maximum)
Watch this video. He already answered the question - whole purpose of this video...
use Diode every string before connecting it in parallel, see the result
can some1 tell me if u can wire 3 panel in a mode when 2 panel is in paralel for increased curent,and 1 whit them in series,same kind of panels,to add more voltage? i have only 3 panel,but whit 3 its more than 100V,but whit all in paralel is too low
NOOOO, that will cause a fire! Put them all in series and use a MPPT solar charge controller. It will maximise your charging.
@@OffGridGarageAustralia the charge controler is mppt built in my inverter,but at 102-105 volts it gives red fault led,and wont charge...if i put them all in paralel,than its around 34-35 volts,but despite the increased teoretic current it wont convert more than like 5-7 amps,out of the 25-30 amps the 3 panel has.Since yesterday i am using only 2 out of 3 in series whit 64 volts,that fluctuates under load/conversion from 45-55volts,and it can do 15-18 amps.I ordered a 4th panel,so my budget increased unfortunately,and i hope i can vire that 2 in series as well,than in paralel whit the other 2 series string,will it work tho to create the rated 30-40 amps?
@@OffGridGarageAustralia also thanks for answering!
I have 16 panels of 435 watt
And 16 panels of 555 watt
Now for 15 HP motor (12 kw)
How string is formed of panels (inverter 15-18)
I depends on your solar controller. Build panel strings (serial) where panels with Icc for each panel is as close as possible. Connect strings with equal Voc in parallel.
It is known that if a group of different panels is connected in parallel and with different of voltage values, then there are two cases we get:
1. If the solar charger charges the battery and supplies the loads with high power, in this case there is no problem because all the solar panels will have lower voltage values for them and equal, as you explained in the video.
2. The second case, if the solar charger stops charging the battery or the power it takes from the solar panels is very little, then the problem will arise and the high-voltage panels discharging the current to the low-voltage panels.
You can try this case and make sure that my words are correct.
If you had a bigger difference in shading you might see different results. If you used a string in the back yard to catch morning sun and a string in the front yard for afternoon sun, you would probably want a solar combiner / diode. Nicht wahr?
I did such a test already in another video and heavily shaded on string. No current backflow though.
th-cam.com/video/NaCOdOdhdTY/w-d-xo.html
@@OffGridGarageAustralia thank you, I'll give it a watch!
@@DavidBTB With similar pv panels and/or similar strings, there is a small change in Voc, due variations in insolation. Under-load and in normal operating conditions, typically both panels or both strings ( East + West ) will contribute amps into the load. This has been known for 15 - 20 years now ...