MPP VOLTS and poor performance

cisumma

New Member
Joined
Apr 2, 2021
Messages
112
Question:
I have 3 strings and each and I have never seen the PV volts at the MPP ever go above 80 volts total.

First , the three strings are in a definite " temporary overpanling " setup; meaning, lots of trees and panels are perpendicular; but, the sun is low for winter and all the panels face south with almost direct sunlight.

Overall, I expect bad performance; yet, each string should be capable of 710 watts and I have never recorded anything over 90 watts total at the MPP.

Furthermore, connections seem consistent; and, a typical string by string test showed three individual strings producing ( at any given moment as the sun transgress ) readings like ex: 90 volts, 48 volts, and 50 volts from each string respectively.

But the MPP never shows an accumulative voltage; however, it does seem to be constant with the reading from the highest strings volts.
But the output volts of the 2024 kw system never even come close to 80 volts total.

Definitely, this seems way to low even for an over paneling PV setup.

Thanks for any constructive criticism.


Solar panel specs I was working with:
24 v system
2024LV-mk
Mpp

Specifications: for Hansol 355 watt panels : 6 panels total.

Mono crystalline

Rated Power: 355W

Open circuit voltage (VOC): 47.8 V

Max power voltage (VMP): 39.2 V

Short circuit current (ISC): 9.65 A

Max power current: 9.06

Maximum system voltage: 1000V UL

Fuse Rating: 15 A

IP68 Junction Box with bypass diodes and industry standard solar connectors

Weight: 49.6 lbs

Dimensions: 78.5×39.37×1.58 inch
-_-_-_-_-_-<--_-_-_--_-_-_-_-_--_-_-_-_-_-_-_-_

expand...

VMAXTANKS AGM high performance batteries. Wide selection of top of the line deep cycle maintenance free batteries.


Battery bank consist of deep cycle SEALED lead acid batteries.



Vmax ah
4s2p = 400ah
24v system




-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_--_-_-_



I have 2s3p for the 355watt panels.

3 strings
 

740GLE

Solar Addict
Joined
Apr 30, 2021
Messages
970
So two panels in series each with a VMP 39.5v will never hit above 80v, even if you have 20 strings.

Any shading and poor angle of the panels won’t do you any favors.

What’s the state of charge of the battery? The SCC can’t put watts into a 100% charged battery
 

sunshine_eggo

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Joined
Oct 26, 2021
Messages
3,529
Location
USA
Question:
I have 3 strings and each and I have never seen the PV volts at the MPP ever go above 80 volts total.

This seems about right for 39.2Vmp x2, 80V.

First , the three strings are in a definite " temporary overpanling " setup; meaning, lots of trees and panels are perpendicular; but, the sun is low for winter and all the panels face south with almost direct sunlight.

How much shading? Shading, even partial, can destroy panel performance.

Overall, I expect bad performance; yet, each string should be capable of 710 watts and I have never recorded anything over 90 watts total at the MPP.

Is your battery full? Does solar wattage change with loads?

Furthermore, connections seem consistent; and, a typical string by string test showed three individual strings producing ( at any given moment as the sun transgress ) readings like ex: 90 volts, 48 volts, and 50 volts from each string respectively.

That doesn't sound right. Please elaborate. The strings should have the same voltage when tested individually.

But the MPP never shows an accumulative voltage; however, it does seem to be constant with the reading from the highest strings volts.
But the output volts of the 2024 kw system never even come close to 80 volts total.

You seem to be contradicting yourself. Do you or don't you see 80V PV?

Definitely, this seems way to low even for an over paneling PV setup.

Thanks for any constructive criticism.


Solar panel specs I was working with:
24 v system
2024LV-mk
Mpp

PV limits:
145Voc
80A charge
2000W max output
89% max solar charge efficiency
MPPT range: 30-115V


Specifications: for Hansol 355 watt panels : 6 panels total.

Mono crystalline

Rated Power: 355W
Open circuit voltage (VOC): 47.8 V
Max power voltage (VMP): 39.2 V
Short circuit current (ISC): 9.65 A
Max power current: 9.06
Maximum system voltage: 1000V UL

Have you confirmed the above values on each and every panels?
 

cisumma

New Member
Joined
Apr 2, 2021
Messages
112
I will show pictures that will explain the poor paneling. The next move is to put them on the flat roof.
But , the outputs seem way low; but, the winter angle does help.

Now the MPP is utility charging throughout the night ; but even with the panels a averaging a out 60 v through out the day the MPP does not accumulate all the 3 different volts as the sun transgress the 3 strings. ( the highest output might govern the PV mpp input.

I regress, the panels run 25% load and charge the batteries all day. ; but, I think the utility charge kicks in and night to maintain a good c rate on the batteries.
I wont know until utility power is cut in order to predict if the PV can maintain a good c rate.
All on all my expectations are to run a little 1 amp ac fridge and periodic use of amp, piano, and radio; as, my low light and high lights are run on a separate 12 system.
Please find some pictures that may describe the system.
Thanks
 

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sunshine_eggo

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I will show pictures that will explain the poor paneling. The next move is to put them on the flat roof.
But , the outputs seem way low; but, the winter angle does help.

I'm impressed your panels are putting out even 90W. The way you have them oriented and the nature of the shading is completely destroying their production.

On your panels and their orientation, if you shade ONLY the cells in ANY single row, you will cut panel output dramatically.

For all intents and purposes, the nature of your partial shading IS JUST AS BAD AS THE ENTIRE PANEL BEING IN FULL SHADE.

Now the MPP is utility charging throughout the night ; but even with the panels a averaging a out 60 v through out the day the MPP does not accumulate all the 3 different volts as the sun transgress the 3 strings. ( the highest output might govern the PV mpp input.

I am not at all surprised that your panel voltage is very low and inconsistent.

I regress, the panels run 25% load and charge the batteries all day. ; but, I think the utility charge kicks in and night to maintain a good c rate on the batteries.
I wont know until utility power is cut in order to predict if the PV can maintain a good c rate.
All on all my expectations are to run a little 1 amp ac fridge and periodic use of amp, piano, and radio; as, my low light and high lights are run on a separate 12 system.
Please find some pictures that may describe the system.
Thanks

You literally have the most horribly partially shaded array I've ever seen in that picture.

Please watch the following video to better understand the impacts of partial shading (crap audio):


Your panels are the 3rd example with a couple of the bottom rows fully shaded.
 

cisumma

New Member
Joined
Apr 2, 2021
Messages
112
Lol, overpanelling is an understatement.
That's good news. I won't condemn the panels yet. Soon , ($$$ dependent) I will kick those panels out and soon the neighbors trees will be totally gone. Then I will repeat a second MPP and put a couple kw on the roof; but, for now , your right lol, perpendicular panels are not good.
My demand right now is just basically " survival with fireplaces places and lights; and surprisingly enough, maybe a little fridge.
Welcome to COMMUNISM.
Thanks for the evaluation though, I think that your assessments are correct and they confirm that the system " sucks " for obvious reasons.
I am hoping that an average of volts I a. Getting throughout the day can maintain the 24v battery pack without utility power.
Not to optometric; but, you might have a better prediction of battery health with 6 hrs a day of an average of 60 volts. Actually, To me, that just might at least maintain 24+- volts.
Thanks again
 

cisumma

New Member
Joined
Apr 2, 2021
Messages
112
I'm impressed your panels are putting out even 90W. The way you have them oriented and the nature of the shading is completely destroying their production.

On your panels and their orientation, if you shade ONLY the cells in ANY single row, you will cut panel output dramatically.

For all intents and purposes, the nature of your partial shading IS JUST AS BAD AS THE ENTIRE PANEL BEING IN FULL SHADE.



I am not at all surprised that your panel voltage is very low and inconsistent.



You literally have the most horribly partially shaded array I've ever seen in that picture.

Please watch the following video to better understand the impacts of partial shading (crap audio):


Your panels are the 3rd example with a couple of the bottom rows fully shaded.
Yep. I'm lucky to have any output. When the neighbors trees are gone I will set a footing and kick those panels out a little and the numbers should be 100 times better.
Thanks again.
 

sunshine_eggo

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Messages
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Lol, overpanelling is an understatement.
That's good news. I won't condemn the panels yet. Soon , ($$$ dependent) I will kick those panels out and soon the neighbors trees will be totally gone. Then I will repeat a second MPP and put a couple kw on the roof;

You are most likely subject to NEC2017 for roof mounted panels. You will need to comply with spacing requirements. Your array will need a master cut-off system that ALSO cuts off each individual panel. This will cost ~$60/panel. This is for firefighter safety if on your roof. Whether you need a solar permit or not, you MUST comply with codes.

but, for now , your right lol, perpendicular panels are not good.

Actually, vertical panels in the northern hemisphere in winter may perform fairly well compared to fixed year-round tilt depending on latitude.

My demand right now is just basically " survival with fireplaces places and lights; and surprisingly enough, maybe a little fridge.

90W of solar all day might satisfy that.

Welcome to COMMUNISM.

Why are you welcoming me to communism?

Thanks for the evaluation though, I think that your assessments are correct and they confirm that the system " sucks " for obvious reasons.
I am hoping that an average of volts I a. Getting throughout the day can maintain the 24v battery pack without utility power.
Not to optometric; but, you might have a better prediction of battery health with 6 hrs a day of an average of 60 volts.

I'm not at all sure what you're talking about here.

Actually, To me, that just might at least maintain 24+- volts.

If you're maintaining 24V±, you're killing your batteries. Your AGM batteries likely need to be charged at 28-28.8V and floated at 27.2-27.6V. If you're not able to maintain this, you're killing your batteries.

I wise man once said, "Batteries don't die. They are murdered." Please don't murder them.
 

cisumma

New Member
Joined
Apr 2, 2021
Messages
112
That's good to know. To coin a phrase " the future will be much brighter".
Right now I have the MPP utility charging throughout the night; so, I start each day with 27.8 +- . I appreciate you evaluation. It confirms that the system is working according to the terrible conditions. I think that with the tree shape gone and a 20°- 30° angle it will be a adequate over paneling scenario. 2kw on the roof would be an ideal system.
Thanks again.
 

iamrich

Photon Sorcerer
Joined
Dec 17, 2020
Messages
954
Location
Elgin, Texas
First , the three strings are in a definite " temporary overpanling " setup; meaning, lots of trees and panels are perpendicular; but, the sun is low for winter and all the panels face south with almost direct sunlight.
You are not over paneled. Even if you somehow got max output from your six panels, you would be fine. The MPP might clip a bit, but it will handle 2130w input without any issues as long as you keep the PV voltage under 115v.

I am running 2250w into mine :)
 

cisumma

New Member
Joined
Apr 2, 2021
Messages
112
You are not over paneled. Even if you somehow got max output from your six panels, you would be fine. The MPP might clip a bit, but it will handle 2130w input without any issues as long as you keep the PV voltage under 115v.

I am running 2250w into mine :)
Hello, all;
I am trying to understand watts and volts from a 2,2 kw, 2s3p PV array energizing MPP that maintains a 400 AH ,24 volt battery pack.
First, I have a emergency low light ( trailer taillights) system to illuminate 6 rooms.
Additionally, I have a dozen bright LED lights for these 6 rooms.
Now, I run a 1 amp ,120 volt refrigerator and this refrigerator would deplete the battery pack each night if the MPP did not maintain the system overnight.
So, my solar system is for emergency application only.
Basically, I have an 2 KW array of overpanallly in the yard.
My questions relate to trying to understand the real world meaning of the watts and volts that the 2.2 MPP is working with; because, 120 volts at 60 hz is clearly the goal of any system at any given time.
Specifically, the MPP must use some kind of induction into a coil ;because, when I monitor the system I see that as soon as sun rise begins and ( 10 watts ) all the way to sunset the MPP cuts the utility support and produces 120 V at 60 HZ and, runs a 25% load and charges the battery.
Furthermore, I have rarely seen the watts produced from 2 kw PV array produce more than 90 to 100 watts.
So, these numbers do not make sense to me and I think my understanding is skewed because this system operates at 120 volts all day and the efficiency is a despicable 5% of a 2 kw PV array.
What do these numbers mean; because, other than the fact that the system is not capable of running large electrical loads during sunny days because of shading , what purpose would having 2 kw of power when the only outcome is to produce 120 volts at 60 hz when this system system seems to induct 10-100 watts into an maximum output of 120 volts.
Clearly, I do not understand the readings that the MPP is telling me.
Finally, when I cut the trees down that shade my PV array what the hell do I do with 2KW of power when the system seems to be healthy with a mere 10 watts.
Basically, I hope to better understand how this MPP system does what it does ; because, the numbers don't seem to make sense.
Thanks
 

iamrich

Photon Sorcerer
Joined
Dec 17, 2020
Messages
954
Location
Elgin, Texas
Hello, all;
I am trying to understand watts and volts from a 2,2 kw, 2s3p PV array energizing MPP that maintains a 400 AH ,24 volt battery pack.

Your battery pack is 24v (likely 26.7ish) x 400ah = 9.6kwh. AGM batteries would give you about 5kwh of available power, and LiFePo4 would give you roughly 8kwh.

First, I have a emergency low light ( trailer taillights) system to illuminate 6 rooms.
Additionally, I have a dozen bright LED lights for these 6 rooms.
How much power do these lights use? 100w of light would cost you 2.4kwh per day
Now, I run a 1 amp ,120 volt refrigerator and this refrigerator would deplete the battery pack each night if the MPP did not maintain the system overnight.
So, my solar system is for emergency application only.
1a x 120v = 120w or 2880wh per day

Basically, I have an 2 KW array of overpanallly in the yard.
My questions relate to trying to understand the real world meaning of the watts and volts that the 2.2 MPP is working with; because, 120 volts at 60 hz is clearly the goal of any system at any given time.
Specifically, the MPP must use some kind of induction into a coil ;because, when I monitor the system I see that as soon as sun rise begins and ( 10 watts ) all the way to sunset the MPP cuts the utility support and produces 120 V at 60 HZ and, runs a 25% load and charges the battery.
Furthermore, I have rarely seen the watts produced from 2 kw PV array produce more than 90 to 100 watts.
So, these numbers do not make sense to me and I think my understanding is skewed because this system operates at 120 volts all day and the efficiency is a despicable 5% of a 2 kw PV array.
What do these numbers mean; because, other than the fact that the system is not capable of running large electrical loads during sunny days because of shading , what purpose would having 2 kw of power when the only outcome is to produce 120 volts at 60 hz when this system system seems to induct 10-100 watts into an maximum output of 120 volts.
Clearly, I do not understand the readings that the MPP is telling me.
Finally, when I cut the trees down that shade my PV array what the hell do I do with 2KW of power when the system seems to be healthy with a mere 10 watts.
Basically, I hope to better understand how this MPP system does what it does ; because, the numbers don't seem to make sense.
Thanks
Your MPP can only use power from the panels when it has somewhere to send it. So, if your batteries are charged to whatever setting you have loaded into the MPP and there is no load on the inverter, the only usage you will get is the power used by the invert itself (about 1.5kwh per day on mine).

If you hook up a laptop to the usb port and load the watch/solar power software, the unit will tell you how much power it is producing each day in a nice graph.
 

cisumma

New Member
Joined
Apr 2, 2021
Messages
112
How much power do these lights use? 100w of light would cost you 2.4kwh per day

Actually, all the lights are in a 12 volts 3p 400 ah battery bank powered by a 300 watt harbor freight system and a 24 step down regulator that has maintained a 14 volt charge for several years now.

I hope to get a laptop as you mentioned. A closer look at the daily readings would help me understand the system better.

Additionally, if these 3 strings on the 24 volt system produce 120 volts all day with only 10- 80 watts. What would be the result of dividing the strings and adding an additional 2KW MPP and ending up with another leg of power? Would this be a phase with two legs and one common ?
Then, would it be possible to run these two legs and share the common and energize a off grid panel to wire the system out of a panel?
Thanks
 
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