Mono and poly solar panels
- Thread starter KXsmith
- Start date
Welcome to the forum.
Brands, mono/poly, etc., don't matter as much as specifications.
Panels in parallel must have very similar Voc/Vmp values. A good match shouldn't suffer more than about 5% penalty.
Panels in series must have very similar Isc/Imp values. ALL panels in a series string will operate at the current of the LOWEST panel. A good match shouldn't suffer more than about 10% penalty.
Brands, mono/poly, etc., don't matter as much as specifications.
Panels in parallel must have very similar Voc/Vmp values. A good match shouldn't suffer more than about 5% penalty.
Panels in series must have very similar Isc/Imp values. ALL panels in a series string will operate at the current of the LOWEST panel. A good match shouldn't suffer more than about 10% penalty.
When you want to connect them in parallel, then this should be no problem. However, if you need to put them in series, this is not recommended as the solar efficiency as well as the spectral sensitivity of mono vs. poly crystalline modules is different. If you put them in series, the weaker always pulls down the stronger one.
In parallel, this is not an issue as both add their current independently.
In parallel, this is not an issue as both add their current independently.
For the OP, this is a marketing answer, and it's incorrect. Same power panels can have different nominal operating voltages. One MUST confirm they are very similar.
ANY panels of different type, brand and power will work if you follow the guidance in my technical answer.
@snoobler - you are correct! Thanks for the clarification! I was expecting we are talking about similar panels with the only difference being poly vs. mono crystalline cells.
To be as clear as possible: IMHO one can connect different types of panels as long as both VoC and Umpp are within 3% or closer to each other. That way, I would dare to even mix crystalline with other technologies BUT I DO NOT RECOMMEND THAT!!! Watch for different thermal coefficients as VoC and Umpp change with temperature differently for different PV technologies.
However, as soon as anybody puts any panels in series, I strongly recommend to use exactly the same panels down to the same panel type and manufacturer.
If anybody wants to parallel strings of series of different panel types, I would not recommend that unless they know exactly what they are doing!
What is Umpp?
Where did you get the 3% number?
What is the basis for your recommendations for and against? Are you a solar professional in some capacity?
Simply following the guidance I provided, which was adapted from actual solar professionals, gives even a novice the foundation upon which to make an informed decision. This question is almost always asked because they are trying to optimize economy to utilize existing resources vs. purchasing all new and tossing out old or buying additional charge controllers. They can make the decision for themselves - "is it worth it to me to lose 5-15% of my total array by using this resource I already have, or does that 5-15% justify me purchasing additional hardware - likely at significant cost."
Manufacturer's recommendations are rooted in their motivation to generate revenue by limiting informed choice. I don't blame them one bit, but I won't help them do it.
Your spirit of helping is appreciated. Please do not provide advice derived from marketing-based fear mongering.
Hm, not sure what guidance your "actual solar professionals" have given you, but for myself, I was director of solar panel development at Bosch Solar Energy, a company you might have heard of ...
And in that position, I had my share of discussions with good and not so good solar professionals. Moreover, I set up a test installation on which my engineers tested long-term stability of solar panels besides the required tests as well as some interesting yield tests.
But to your points:
Umpp is the German version for voltage at maximum power point. I'll take the blame for this, but on the other hand wasn't that obvious?
And the three percent: If you look at a voltage-power-diagram of a solar panel, you'll see that there is a pretty wide maximum at which Vmpp is defined. So 3% up or down won't make such a big difference. If you then consider that a slightly different mounting angle, e.g. because of a different panel frame makes for slightly different absorption rates ... The main point IMHO is that there won't be any damage because of Vmpp of the strongest panel is above VoC of the weakest.
In short, I wanted to give some quantifiable guidelines and not loose myself in clouds as others do in such instances.
And trust me, I do not have to sell anything, I landed a pretty nice job after Bosch Solar Energy closed down. This is just for fun and because I have the money to play around.
Last but not least, you could have brought up your concerns via PM instead of questioning my expertise in such a way. Being new to the forum does not necessarily mean I am a novice!
FANTASTIC!
Given that there are different levels of user on the forum "Umpp" might have thrown them for a loop.
Simply prefacing your recommendations with your expertise or background, e.g., "I worked in solar panel development for a major company," would have made sense when said you "recommend" something.
Based on your statement, it seems that 3% isn't even that important. What if it's 5%? What are the implications besides power loss?
Should someone invest in another $1000 of panels or another charge controller rather than use some 72 cell panels they already have because there's a 2V mismatch in their Vmp from their existing array? Let's say they could double their array, but take a 5-10% hit on total array performance, is that worth it?
Are there significant long term implications of running mono/poly combined arrays with 5% variation in Vmp?
In a DIY scenario, systems are often iterative. Things are added, changed, etc. It's not always as easy as "one and done" for 25 years. Understanding the implications of a decision is often more valuable than doing things exactly the best way.
More importantly, please share with us the "interesting yield tests."
I personally look forward to your contributions.
Given that there are different levels of user on the forum "Umpp" might have thrown them for a loop.
Simply prefacing your recommendations with your expertise or background, e.g., "I worked in solar panel development for a major company," would have made sense when said you "recommend" something.
Based on your statement, it seems that 3% isn't even that important. What if it's 5%? What are the implications besides power loss?
Should someone invest in another $1000 of panels or another charge controller rather than use some 72 cell panels they already have because there's a 2V mismatch in their Vmp from their existing array? Let's say they could double their array, but take a 5-10% hit on total array performance, is that worth it?
Are there significant long term implications of running mono/poly combined arrays with 5% variation in Vmp?
In a DIY scenario, systems are often iterative. Things are added, changed, etc. It's not always as easy as "one and done" for 25 years. Understanding the implications of a decision is often more valuable than doing things exactly the best way.
More importantly, please share with us the "interesting yield tests."
I personally look forward to your contributions.
Interesting way to motivate valuable contributions!FANTASTIC!
Given that there are different levels of user on the forum "Umpp" might have thrown them for a loop.
Simply prefacing your recommendations with your expertise or background, e.g., "I worked in solar panel development for a major company," would have made sense when said you "recommend" something.
Based on your statement, it seems that 3% isn't even that important. What if it's 5%? What are the implications besides power loss?
Should someone invest in another $1000 of panels or another charge controller rather than use some 72 cell panels they already have because there's a 2V mismatch in their Vmp from their existing array? Let's say they could double their array, but take a 5-10% hit on total array performance, is that worth it?
Are there significant long term implications of running mono/poly combined arrays with 5% variation in Vmp?
In a DIY scenario, systems are often iterative. Things are added, changed, etc. It's not always as easy as "one and done" for 25 years. Understanding the implications of a decision is often more valuable than doing things exactly the best way.
More importantly, please share with us the "interesting yield tests."
I personally look forward to your contributions.
So if I have a mono 305W with VOC: 39.9 and VMP: 32.3 and a poly with 300W with VOC: 39.85 and VMP: 32.26 and I hook them up in parallel will that work?
Yes. There will be essentially no penalty with only a 0.05V difference.
As @KaFun pointed out, the temperature coefficients may make that deviation greater at temperature extremes (I estimate about 1% difference in the panels for every ±10°C from 25°C).
I personally wouldn't hesitate to connect them in either series or parallel.
Thank you so much for the info.
I'd like to follow up on this answer. I have 1 250W mono in use, and will likely be adding 3 more 240W polys. The single is:
Voc 37.8/Vmpp 31.1/Isc 8.28/Impp 8.05
The 3 additionals are:
Voc 37.2/Vmpp 30.4/Isc 8.37/Impp 7.89 (these 3 are same brand)
They seem pretty close. Mixing poly and mono in this case shouldn't be an issue? Also, in general, other than the loss of efficiency in mixing dissimilar panels, is there an inherited issue of damaging the panels themselves over the long term? Would the panel(s) suffer any reduced longevity being wired together with others of different ratings?
I don't think there is any way the panels can be damaged by mixing them. Some types seem to do better in lower light and those type in series with types that don't do as well in low light would cause the poorer performance ones to dictate overall performance but that is a small amount of difference.
