Why the low power?

[Zardiw]

With homebrew panels, you have a lot of failure points that don't exist in factory panels, and
if your battery has completed bulk, there may not be anyplace for the power to go, so it's simply not harvested

1. These are 50-100 year panels. Glass on Glass, using high efficiency mono cells.
........I don't think commercial panels can even compare.....

2. I don't see how the batteries have completed bulk......given the low voltage of the bank.

3. The charger SAYS it's in Bulk............

Now, if I put a heavy load on the system, THEN there would be somewhere for the power to go, correct?

z

[Zardiw]

Here's some individual readings:

Voltage at array: 33.8v

         Voc
PV---Volts---Amps

1---36.2---5.93
3---36.2---7.32
7---35.1---6.44
9---34.8---6.51

Total of just 4 Panels individually: 26.2 Amps

Currently the Classic is showing 17.9 Total Amps at 32V

Pretty pathetic.............

z

I don’t understand your measurement. Here you indicate 4 panels putting out 26.2A. Yet in your photo you show each panel at approx 2.5A. Something does not add up. Hard to make any suggestions when the data provided is unclear.

The readings were taken at different times of day..........

Bottom Line: Before I was getting about 25% of the array capability......now I'm getting 50%, using Legacy P+O mode.

z

[Zardiw]

I'd REALLY like an explanation of why this happened:

I started with Panel 2 and added 1 panel at a time and noted the readings on the Solar Status Panel software.

When I added panel 8 there was NO change.

Disconnected 8 and added 9.......again no change.

Disconnected 9 and added 1........no change.

Added 8,9,1 and watts went up a little.

Also took Voc/Amp readings on each panel.

Also took a FLuke DC Amps reading.....it was late in the afternoon........but only 16.9 Amps......shoulda been at least twice that.

And each panel has 67 cells..not 66.......fwtfw.

z

[Zardiw]

I read somewhere that if the solar output voltage is below the battery volts, then the Classic would operate like a PFM .......is that correct?

Cause I could change the Battery voltage to 36 .....

z

[KyleM]

I read somewhere that if the solar output voltage is below the battery volts, then the Classic would operate like a PFM .......is that correct?

Cause I could change the Battery voltage to 36 .....

z

The Classic will sit in Resting Mode until the input voltage reached approximately 130% of the battery voltage set point   48 x 133% = 64 volts  This is the point that the Classic will try to start BULK. If there is enough power coming into the Classic, it will stay in BULK and drive to ABSORB voltage. If for any reason there is not enough power to stay in BULK the Classic will go back into RESTING mode  and try again as the voltage rises.

[Zardiw]

I read somewhere that if the solar output voltage is below the battery volts, then the Classic would operate like a PFM .......is that correct?

Cause I could change the Battery voltage to 36 .....

z

The Classic will sit in Resting Mode until the input voltage reached approximately 130% of the battery voltage set point   48 x 133% = 64 volts  This is the point that the Classic will try to start BULK. If there is enough power coming into the Classic, it will stay in BULK and drive to ABSORB voltage. If for any reason there is not enough power to stay in BULK the Classic will go back into RESTING mode  and try again as the voltage rises.

Thank You!

Now, if the Classic is in 'resting' mode........will the readings in the Midnite Solar Status Panel software read as 0 on the Watts and Battery Amps?

Cause that has never happened.....

z

[boB]

Z's system is 24V not 48V...

It's 1.33 X battery voltage -1.0 volt as I remember...

So, 1.33 X say, 27V  would be 35.9V  and -1.0V would be  34.9V

So, 35V or 36V should be on the edge but OK.

So, this chart, which adding up all of the Isc values gives you about 26 amps...


         Voc
PV---Volts---Amps

1---36.2---5.93
3---36.2---7.32
7---35.1---6.44
9---34.8---6.51

Total of just 4 Panels individually: 26.2 Amps

Currently the Classic is showing 17.9 Total Amps at 32V


....Doesn't necessarily mean you are going to get Isc at the Vmp voltage.  Imp should be kind of close to the Isc but not exactly.  Some panels will be more different than others

You could try this and use the real amp-probe that you used for measuring short circuit current so that doesn't vary...

Measure Isc of  ONE panel and the Voc of that panel.

Then, measure the current of that one panel at the Vmp that the Classsic finds and also note that voltage and current.

The Vmp that the Classic finds should be somewhere between 76% and 82%  of the panels' Voc measurement.

The power will be the Vmp times the Imp of course.  But this will at least show you what you SHOULD get out of the panel.

You can tweak the Vmp when in MPPT mode (Bulk, Float MPPT), up and down by pressing the soft-left or soft-right keys.

i.e. The upper left and upper right keys while in the main status screen to make sure that you are really at the Max Power point.

Interested to hear what you find.

boB

[Vic]

Hi z,

Well,  you DO understand that PV modules are specified with cell temperatures of 25 C  --  77 F,   with 1000 watts/ sq meter of illumination,   using a flash tube.

In full midday sun,  we can have,   at best about 1 kW/sq M,   but the sun heats the cells.   So   at solar peak in full sun  most PVs produce about 75 - 77% of this maximum specified amount of power.   Less power  at lower sun angles and with the sun not directly at 90 degrees to the sun.

Do not know about the cells that were used to make your PVs,   but it is not uncommon for the cells that one can buy on the market (on e-bay,  etc)  to be cells that do not quite pass final power tests,   or have other defects.   Of course it is not possible to know the specs of each cell that are in your PVs.

So  taking measurements can be a bit difficult,  due the variables that come into play with the exact setup of each PV that one is measuring,   individually.

Most PVs are manufactured by robots,   this can help make PV modules more consistent   than PVs that are made by hand,   etc.

FWIW,   IMO,   etc,    Vic

[tecnodave]

Zardi,

With home built panels there are many factors that are not considered.  Take the glass.....there is many varieties from iron containing window glass to water white to specialty solar hi transmissible glass etc. same with the bond between the glass and the glass. How many bypass diodes....etc. every detail needs to be considered.
I have never heard of any manufacturer offer a 50-100 year panel. I have a few that have survived the sun in the Arizona desert for over 30 years and the are very dog eared ,burnt, cracked cells, etc. These were built by a major forerunner to the present industry.  There is an government agency here in California that approves panels to be used in code approved installations. They publish lists of acceptable panels and other lists of panels that have been decertified....including BP SOLAR! Hundreds of manufacturers that did not make the grade. Some of these companies poured millions into R&D.

I have 26 Sharp panels and they do not vary .1 volt or .1 amp from each other.  Same for my 60 Sanyo HIT panels....very little variation between panel to panel...same for my Suntech panels....ditto for the antique Seimens SM-55's that are now owner 30 years old. And dog eared with burnt brown cells and cracks.

I do not think that any home builder can match the production process of a major manufacturer. They computer match cell by cell and separate them into groups. That is exactly why Sharp offers NE-165, NE-170, NE-180, NE-190,  no they don't deliberately make 165 watt panels when the same production process can crank out the 190 watt ones. They weed out cells and make matching sets using computerized automated testing to sort the cells to be matched. The worst cells are sold by the lot to middle men and they land up on eBay.  There is a lot of engineering going on there. I've been there, I've seen the process, it's way beyond my abilities and I have done many years in electricity and high end electronics.

That said it is understandable that each of your panels do not produce the same power. There are way too many variables to get a consistent result.

I have done several 2-4 kW  24 volt systems using the most commonly available panels...the 60 cell grid-tie type. I use them in strings of 2 for a MPP of about 60 volts. Never had an issue doing this even though the standard for 24 volt use is the 72 cell panel in strings of two.

Two of my main banks are all parallel 96 cell Sanyo HIT panels on my 24 volt systems, pretty rare to have a 2kw array all parallel. Sometimes when in very fowl weather I need to switch from solar mode to Legacy P&O to get maximum power. I'm right on the coast looking at the Pacific Ocean with the Santa Cruz mountains to my back so my weather is very variable here...very dynamic!  I harvest more than enough power even on days where I don't see the sun all day.  I'm very hands on with my systems.

I didn't get to here in a day or so....I haven't had a utility connection for over 20 years. There is a learning process. BTW...I was born in backwoods Alaska way off grid.....born off-gridder! Upper Matanauska-Susitna Borough...looking out at Denali Mount.....and yeah I miss it. If I could get decent medical care there I would retire there. Except in winter.....

Try some patience and understanding. This is not plug and play!

david

[Zardiw]

Hi z,

Well,  you DO understand that PV modules are specified with cell temperatures of 25 C  --  77 F,   with 1000 watts/ sq meter of illumination,   using a flash tube.

In full midday sun,  we can have,   at best about 1 kW/sq M,   but the sun heats the cells.   So   at solar peak in full sun  most PVs produce about 75 - 77% of this maximum specified amount of power.   Less power  at lower sun angles and with the sun not directly at 90 degrees to the sun.

Do not know about the cells that were used to make your PVs,   but it is not uncommon for the cells that one can buy on the market (on e-bay,  etc)  to be cells that do not quite pass final power tests,   or have other defects.   Of course it is not possible to know the specs of each cell that are in your PVs.

So  taking measurements can be a bit difficult,  due the variables that come into play with the exact setup of each PV that one is measuring,   individually.

Most PVs are manufactured by robots,   this can help make PV modules more consistent   than PVs that are made by hand,   etc.

FWIW,   IMO,   etc,    Vic

Thank you Vic.......

But you're missing the point........getting into the thicket of temperature, sun angle, PV efficiency, etc.

The POINT is that I'm getting not even CLOSE to what these panels are putting out.

And fwiw, these are 19-21% MONO 6x6 cells.....that came Boxed from the manufacturer........

Explain how a panel that has a Voc of 37v and a short circuit Amp reading of 6 something is only putting out 92 watts from the controller........THAT is the POINT.

z

[Vic]

Here's some individual readings:

Voltage at array: 33.8v

         Voc
PV---Volts---Amps

1---36.2---5.93
3---36.2---7.32
7---35.1---6.44
9---34.8---6.51

Total of just 4 Panels individually: 26.2 Amps

Currently the Classic is showing 17.9 Total Amps at 32V

Pretty pathetic.............

z

I don’t understand your measurement. Here you indicate 4 panels putting out 26.2A. Yet in your photo you show each panel at approx 2.5A. Something does not add up. Hard to make any suggestions when the data provided is unclear.

The readings were taken at different times of day..........

Bottom Line: Before I was getting about 25% of the array capability......now I'm getting 50%, using Legacy P+O mode.

z

Hi z,

It seems that some of the "data" was taken at different times of day.

We all are trying to help.   We wind up trying to do a bit of guessing,   just what is going on,  you are our reporter   ...   I was just attempting to remind you about some of the obvious variables,   and possible effects of on measurements you were mentioning.

Sorry about not doing my "job"  of explaining exactly what is going on  ...

You seemed disappointed in the performance of the Morningstar MPPT CC  --  low output power.

You seem disappointed in the Classic for the same reason.   One consistent part of this equation might be something related to the PVs.   Or perhaps expectations for PV power production  at times of day when the Irradiance is low for varying reasons.

Was just trying to toss out some of those possible factors,   in case you were not considering them.

Voc is not a very useful number to gauge potential PV power production.   It is easy to measure,  though.   Vmp is not quite so easily measured,  of course.

Anyway,   good luck,   Vic

[Zardiw]

Zardi,

With home built panels there are many factors that are not considered.  Take the glass.....there is many varieties from iron containing window glass to water white to specialty solar hi transmissible glass etc. same with the bond between the glass and the glass. How many bypass diodes....etc. every detail needs to be considered.
I have never heard of any manufacturer offer a 50-100 year panel. I have a few that have survived the sun in the Arizona desert for over 30 years and the are very dog eared ,burnt, cracked cells, etc. These were built by a major forerunner to the present industry.  There is an government agency here in California that approves panels to be used in code approved installations. They publish lists of acceptable panels and other lists of panels that have been decertified....including BP SOLAR! Hundreds of manufacturers that did not make the grade. Some of these companies poured millions into R&D.

I have 26 Sharp panels and they do not vary .1 volt or .1 amp from each other.  Same for my 60 Sanyo HIT panels....very little variation between panel to panel...same for my Suntech panels....ditto for the antique Seimens SM-55's that are now owner 30 years old. And dog eared with burnt brown cells and cracks.

I do not think that any home builder can match the production process of a major manufacturer. They computer match cell by cell and separate them into groups. That is exactly why Sharp offers NE-165, NE-170, NE-180, NE-190,  no they don't deliberately make 165 watt panels when the same production process can crank out the 190 watt ones. They weed out cells and make matching sets using computerized automated testing to sort the cells to be matched. The worst cells are sold by the lot to middle men and they land up on eBay.  There is a lot of engineering going on there. I've been there, I've seen the process, it's way beyond my abilities and I have done many years in electricity and high end electronics.

That said it is understandable that each of your panels do not produce the same power. There are way too many variables to get a consistent result.

I have done several 2-4 kW  24 volt systems using the most commonly available panels...the 60 cell grid-tie type. I use them in strings of 2 for a MPP of about 60 volts. Never had an issue doing this even though the standard for 24 volt use is the 72 cell panel in strings of two.

Two of my main banks are all parallel 96 cell Sanyo HIT panels on my 24 volt systems, pretty rare to have a 2kw array all parallel. Sometimes when in very fowl weather I need to switch from solar mode to Legacy P&O to get maximum power. I'm right on the coast looking at the Pacific Ocean with the Santa Cruz mountains to my back so my weather is very variable here...very dynamic!  I harvest more than enough power even on days where I don't see the sun all day.  I'm very hands on with my systems.

I didn't get to here in a day or so....I haven't had a utility connection for over 20 years. There is a learning process. BTW...I was born in backwoods Alaska way off grid.....born off-gridder! Upper Matanauska-Susitna Borough...looking out at Denali Mount.....and yeah I miss it. If I could get decent medical care there I would retire there. Except in winter.....

Try some patience and understanding. This is not plug and play!

david

Thank you Dave!

That all makes sense......I realize that a panel is only as good as it's weakest cell...

So commercial panels can be 'better' from that standpoint.

What I don't understand is why the power reported by the controller is so much LESS than what I'm measuring when I test each panel separately, and add it up.

It's partially overcast here, so I can't run my tests........the highest watt output today was at 1500 watts for a short time.....which is getting close to what I would expect....but still over 500 watts shy.....

I'll run extensive tests both with my Fluke DC Amp meter, and various configurations, both series and parallel and report back.......Will have to wait for a nice sunny day here in Palm Springs....which usually wouldn't be a problem.....lol.......except this year has been very strange weather wise.

The purpose of this system is also to go as much off grid as possible.....I like watching my electric bill decrease.

This is also not grid tied in any way.....and I don't want it to be.....I have a 50 amp relay that completely separates the grid from solar.....it's either one or the other.

But I'm slowly moving stuff over to the solar side .....to the inverter.....so far I've got some refrigerators and freezers totally running off solar......fwiw.

Anyway, thanks again for the input.......I'll report back with more info soon......

z

[Zardiw]

Here's some individual readings:

Voltage at array: 33.8v

         Voc
PV---Volts---Amps

1---36.2---5.93
3---36.2---7.32
7---35.1---6.44
9---34.8---6.51

Total of just 4 Panels individually: 26.2 Amps

Currently the Classic is showing 17.9 Total Amps at 32V

Pretty pathetic.............

z

I don’t understand your measurement. Here you indicate 4 panels putting out 26.2A. Yet in your photo you show each panel at approx 2.5A. Something does not add up. Hard to make any suggestions when the data provided is unclear.

The readings were taken at different times of day..........

Bottom Line: Before I was getting about 25% of the array capability......now I'm getting 50%, using Legacy P+O mode.

z

Hi z,

It seems that some of the "data" was taken at different times of day.

We all are trying to help.   We wind up trying to do a bit of guessing,   just what is going on,  you are our reporter   ...   I was just attempting to remind you about some of the obvious variables,   and possible effects of on measurements you were mentioning.

Sorry about not doing my "job"  of explaining exactly what is going on  ...

You seemed disappointed in the performance of the Morningstar MPPT CC  --  low output power.

You seem disappointed in the Classic for the same reason.   One consistent part of this equation might be something related to the PVs.   Or perhaps expectations for PV power production  at times of day when the Irradiance is low for varying reasons.

Was just trying to toss out some of those possible factors,   in case you were not considering them.

Voc is not a very useful number to gauge potential PV power production.   It is easy to measure,  though.   Vmp is not quite so easily measured,  of course.

Anyway,   good luck,   Vic

Sorry Vic.......this is pretty frustrating and I really appreciate all the help..........didn't mean to come off the way I apparently did.

You're right....both the Morningstar MPPT and the Classic seem to be putting out much less power than I expected.

However, the Tristar 45 PFM was putting out a Lot more power........I had no readings from that, but went by the rise in battery voltage during the day.......it easily got to 29 and even 30 volts....

When I use MPPT, I'm lucky to get to 27 volts.

I know it's getting warmer, and I'm using more power......and I have no hard data to back that up as in readings, etc........but by now I have a 'feel' for my system, and I can tell the difference between MPPT and PFM .......which is leading me to believe that MPPT is a myth.......lolol.

Again, sorry if I was abrupt .....I really DO appreciate the help.....

z

PS. If anybody is curious as to how I'm building these panels......I have a YT series. First one:

https://www.youtube.com/watch?v=CuL-3msNpZ0&t=114s

[boB]

What I don't understand is why the power reported by the controller is so much LESS than what I'm measuring when I test each panel separately, and add it up.

z

What is the maximum power point voltage for each module and how much power was that at each of those voltages ?

One issue besides your Vmp being low is that each module's Vmp is different.  If they are much different then you will only get an average Vmp.

For your system you will definitely want to use Solar O&P mode for tracking until you know that solar tracking mode is correct for this low voltage system.

Adding panels in series, and especially two or 3 panels that are similar power and current output but different Vmp's will be tracked better in series.

boB

[ClassicCrazy]

[

I looked at your first post where you said what your battery is
"And Battery bank is at 26.8V (24V System w/ 4 6V Trojan L16's) "

What is your Absorb, Absorb time , and Float setpoints ?
When you are expecting the most power to come in do you have  your system fully loaded with devices that will draw more power than  your panels are capable of ?
My thought is that you can only force so much power into that small set of batteries and if you don't have loads on your system you won't be able to see the potential amount of power available. 
I didn't reread all the comments before this one to see if this has already been discussed.

Larry