Doubts about max solar array

Venezuela Solar · May 16, 2020

Hi, im currently thinking on buying some used solar panels, i have already bought them before, from an array of 12 x 245w = 2940w (in theory) i really get 1.650w at best, wich is like 0.55 of the rated power, and that got me thinking, if this modules never get to 100% rated power (and no module ever does) could i over power a new array without over charging or frying the controller?

Example: the lv2424 mpp solar has a maximum rated solar array of 2000w if i derate the array to 0.75 i would need like 2600w of solar to really get to the maximum capacity of the controller (if modules are new if not is even less power that needs to be handle by the controller right?) I woudnt use an array so big any way, i would use lets say 2200w or 2300w son even in best case scenario i would get like 1700w to 1800w

Or should i install only 2000w top and expect 1400w-1500w ??

kernel · May 16, 2020

Its hard to guestimate if conditions of insolation are the cause or if they are commercial polycrystaline of lower quality and are just sun zorched (solarized) and at say 55% which is uncommon.

A light meter could help estimate % output decently for a diy.

I assure you, if you get the right modules they will hit amd hold nameplate for long durations amd decades of use. Monocrystal for serious home power or at least a good quality world class poly gets it done and keeps on doing it.

Arco/siemens/shell/solarworld technology. DOE projects all over the southwest US are still producing at 90+%! Installed in 1968......

Again, for posterity.

Arco/siemens/shell/solarworld technology. DOE projects all over the southwest US are still producing at 90+%! Installed in 1968.........

gnubie · May 16, 2020

Venezuela Solar said:
could i over power a new array without over charging or frying the controller?

The key point to remember is to not exceed the voltage ratings of the controller. If your array keeps within the voltage requirements of the controller, but can produce more current than the controller is rated for, a good controller will handle it without any problems. Good controllers will simply limit the amount of current they will draw from the array so no damage will occur. AFAIK the MPPT range of MPP all-in-one inverter/chargers fall into this category.

Cheap nasty controllers can damage themselves as they have no current limiting on their input, nor load / battery output either, and will simply pull as much current as the load on their output can absorb, and fail as a result.

Supervstech · May 16, 2020

kernel said:
Its hard to guestimate if conditions of insolation are the cause or if they are commercial polycrystaline of lower quality and are just sun zorched (solarized) and at say 55% which is uncommon.

A light meter could help estimate % output decently for a diy.

I assure you, if you get the right modules they will hit amd hold nameplate for long durations amd decades of use. Monocrystal for serious home power or at least a good quality world class poly gets it done and keeps on doing it.

Arco/siemens/shell/solarworld technology. DOE projects all over the southwest US are still producing at 90+%! Installed in 1968......

Again, for posterity.

Arco/siemens/shell/solarworld technology. DOE projects all over the southwest US are still producing at 90+%! Installed in 1968.........

Are you saying that your experience is the majority of panels put out rated wattage for 50 years?
My experience is EVERY panel I have EVER worked with at best outputs 80% rated wattage... perhaps, with solar tracking, or perfect oriented sun angle panels MIGHT hit the 90% mark... but no WAY would it output this level for more than one hour at any fixed position per year...

Venezuela Solar · May 16, 2020

kernel said:
Its hard to guestimate if conditions of insolation are the cause or if they are commercial polycrystaline of lower quality and are just sun zorched (solarized) and at say 55% which is uncommon.

A light meter could help estimate % output decently for a diy.

I assure you, if you get the right modules they will hit amd hold nameplate for long durations amd decades of use. Monocrystal for serious home power or at least a good quality world class poly gets it done and keeps on doing it.

Arco/siemens/shell/solarworld technology. DOE projects all over the southwest US are still producing at 90+%! Installed in 1968......

Again, for posterity.

Arco/siemens/shell/solarworld technology. DOE projects all over the southwest US are still producing at 90+%! Installed in 1968.........

I think this are not good quality panels, this are from Santan Solar and have snail trails, some of them look a little damage by the sun, example, some of them have on the front "dry skin", other yellowish spots (maybe water?) They all work and output good voltaje (35 or 36 from 37.7 open circuit in the label) at mid day (12.30-1.30 pm) they output about 1600w, and the total rated power is 2940w, so from there is where i get that number, im using the Rover 60A PG mppt, could it be the configuration? Can an mppt divert power to protect the batteries? I told the controller that i have an small battery bank so i dont know if is that

sed6 · May 17, 2020

I've had days in a row where my 1040 watts of panels output only 30-50% of there rated capacity. Then a clear sunny day comes along and I get 950 watts, reminding me all is well with my panels ?

DENWA · May 17, 2020

Venezuela Solar said:
I think this are not good quality panels, this are from Santan Solar and have snail trails, some of them look a little damage by the sun, example, some of them have on the front "dry skin", other yellowish spots (maybe water?) They all work and output good voltaje (35 or 36 from 37.7 open circuit in the label) at mid day (12.30-1.30 pm) they output about 1600w, and the total rated power is 2940w, so from there is where i get that number, im using the Rover 60A PG mppt, could it be the configuration? Can an mppt divert power to protect the batteries? I told the controller that i have an small battery bank so i dont know if is that

I bought 20 those same panels and test every single one of the with a calibrated light meter from work.

All 20 of them tested to between 246-253W peak output. I wish I had bought more at $35 each!

MisterSandals · May 17, 2020

Venezuela Solar said:
They all work and output good voltaje (35 or 36 from 37.7 open circuit in the label)

Have you tested the amps that each panel produces? My guess is that a few of your panels may fail to produce under load rather than all performing at 55%.

Venezuela Solar · May 17, 2020

MisterSandals said:
Have you tested the amps that each panel produces? My guess is that a few of your panels may fail to produce under load rather than all performing at 55%.

Yes, there is one small array that produces only 1 amp, while the other 2 amps, it varies, i have 4 small arrays 3S by in 4P, i have been thinking to do the test while unplugging those 3

Venezuela Solar · May 17, 2020

DENWA said:
I bought 20 those same panels and test every single one of the with a calibrated light meter from work.

All 20 of them tested to between 246-253W peak output. I wish I had bought more at $35 each!

I may be wrong, this are 245w each, yours too? Maybe some of my modules are underperforming

PHoganDive · May 17, 2020

It also depends where on earth you are as well, the closer to the equator you are, the less losses will be from atmosphere, going nearly straight up closer to the equator will get significantly more power than a low angle at a high latitude, even if both are pointed straight at the sun at high noon.

kernel · May 17, 2020

You could get some back from the wear caused mis-match by matching outputs to similar strings or with optimizers. Optis cost min. 45$ each, if panels are cheaper id go with more panels in some situations.

The condition you describe is a classic solarized, sun zorched panel description.....
Still, unless the output observations are tightly controlled you will not know for sure unless its egregious.

Dont give up on them if so, just juggle the positions to get the best real world results.

kernel · May 17, 2020

Supervstech said:
Are you saying that your experience is the majority of panels put out rated wattage for 50 years?
My experience is EVERY panel I have EVER worked with at best outputs 80% rated wattage... perhaps, with solar tracking, or perfect oriented sun angle panels MIGHT hit the 90% mark... but no WAY would it output this level for more than one hour at any fixed position per year...

Are you working with solarworlds?

Not my statement. DOE and NREL data.....

Now, yes my 1200w arrays are doing 1200w-1300w.

How?
Simple
Each cell has sorted and matched to have 5 more watts than nameplate................................................................... so they actually meet nameplate. Great for designers like myself. Just saying

You will not get this performance at the hong kong fuey store. You may be lucky, hence my same panel as yours does such and such and the uncertainty.

.55 cents a watt for american solarworld. If we would have kept buying them they would still be around and you wouldnt have to spend 1$/w on hitachi, panasonic, rec, etc. For the same

Last time ill offer.
Hanwha q cells are the new low cost champ. I observe directly and report that from last seasons last couple installs. Its all i can do to help stop the insanity.
They are my go to as i dont like the missions and helienes. Have not had a taste of silfab as of yet but have installed most high quality panels of the last 15 years. Sanyo, rec, sunpower, sharp, panasonic, etc, etc, etc.

I have absolutely no reason to bias or confabulate and if you dont believe it you dont have to, jus stack 100w 1$/W questionable modules to the moon and dont look back.

kernel · May 17, 2020

Supervstech said:
Are you saying that your experience is the majority of panels put out rated wattage for 50 years?
My experience is EVERY panel I have EVER worked with at best outputs 80% rated wattage... perhaps, with solar tracking, or perfect oriented sun angle panels MIGHT hit the 90% mark... but no WAY would it output this level for more than one hour at any fixed position per year...

I am at 42.5° north. My arrays are on east and west facing roof planes but tilted to 30° and oriented south. Wattages from this month with 60°F ambient temps.
Even my azimuth is non-ideal.........

Highest single array output with 1200W nameplate is 1350W.

kernel · May 17, 2020

kernel said:
Are you working with solarworlds?

Not my statement. DOE and NREL data.....

Now, yes my 1200w arrays are doing 1200w-1300w.

How?
Simple
Each cell has sorted and matched to have 5 more watts than nameplate................................................................... so they actually meet nameplate. Great for designers like myself. Just saying

You will not get this performance at the hong kong fuey store. You may be lucky, hence my same panel as yours does such and such and the uncertainty.

.55 cents a watt for american solarworld. If we would have kept buying them they would still be around and you wouldnt have to spend 1$/w on hitachi, panasonic, rec, etc. For the same

Last time ill offer.
Hanwha q cells are the new low cost champ. I observe directly and report that from last seasons last couple installs. Its all i can do to help stop the insanity.
They are my go to as i dont like the missions and helienes. Have not had a taste of silfab as of yet but have installed most high quality panels of the last 15 years. Sanyo, rec, sunpower, sharp, panasonic, etc, etc, etc.

I have absolutely no reason to bias or confabulate and if you dont believe it you dont have to, jus stack 100w 1$/W questionable modules to the moon and dont look back.

Thousands of them........ terrawatts of output from my wrench.

And mostly residential, i did one season of utility scale, a 1.2 megawatt job as electrician/technician.

Edit. Terrawatt/hrs

Ampster · May 17, 2020

DENWA said:
I bought 20 those same panels and test every single one of the with a calibrated light meter from work.

All 20 of them tested to between 246-253W peak output. I wish I had bought more at $35 each!

I have had good luck with used solar panels as well. The OP has recieved good advice about how to manage controllers. FWIW I have a Grid Tied system that has 5.7 kW in panels running a 3.8 kW inverter. The installer matched the string so it would not go over voltage and the MPPT controller curtails or limits the solar to the capability of the inverter.

Ampster · May 17, 2020

The installer used 10 Awg for a 20 foot run at over 300 volts DC so I don't think I am losing much there. The inverter is over 95% efficient. I am regularly clipped and at the max capacity of the inverter for 3 to 4 hours per day. I am pretty happy with the efficiency of that GT system. My self installed system with used panels is facing west so lots of inefficiency there. Its secondary purpose is shade for a patio cover so it is very efficient in that regard.

Supervstech · May 17, 2020

Ampster said:
The installer used 10 Awg for a 20 foot run at over 300 volts DC so I don't think I am losing much there. The inverter is over 95% efficient. I am regularly clipped and at the max capacity of the inverter for 3 to 4 hours per day. I am pretty happy with the efficiency of that GT system. My self installed system with used panels is facing west so lots of inefficiency there. Its secondary purpose is shade for a patio cover so it is very efficient in that regard.

Remember, wire gauge doesn’t care what voltage is used, it cares what the amperage it is carrying is.

Ampster · May 17, 2020

My inverter has everything to do with it because I have no charge controller and no transformer. I understand what you are saying but you jumped to a conclusion that my system was inefficient without checking your assumption. Grid Tie inverters are typically much more efficient than Off grid inverters with separate charge controllers.
I don't know what you are talking about when you say your alarms go off when I say I am running 4kW through 10 AWG wire. Do the math. My strings run at more than 300 volts so that is less than 15 Amps.

Ampster · May 17, 2020

Supervstech said:
Remember, wire gauge doesn’t care what voltage is used, it cares what the amperage it is carrying is.

That is why I mentioned voltage. That high voltage reduces the Amps. I don't think @Affordable Solarguy is familiar with GT inverters with high string voltages so he made some assumptions that were incorrect.

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