How much am I getting ripped off for my solar panels?

[Adelie]

Originally Posted by GILow

Just read this again... 15 volts peak seems pretty high to me, if that is on the battery side. Off the top of my head I can't think of a battery chemistry that likes that kind of charging voltage.



What sort of batteries do you have?

With PWM or MPPT controllers it doesn’t matter to the battery what voltage the panels produce.

With PWM you want a panel with a voltage a little higher than the 14.5v (15-17v) so that the controller isn’t wasting much power.

With MPPT significantly higher voltage (16-21v) works just fine, the system trades excess voltage for more amps.

[zstine]

My data... I have two Kyrocera hard panels for a 530 watt array. I regularly make that peak, measured by my Victron Blue MPPT controller which gives daily summary and real time data via an app. In fact, a few days ago I peaked at 634 watts! Typically 2kwh daily production, give or take

[Stu Jackson]

Originally Posted by lawrence_craig

Ok, that’s very helpful. My batteries are normally at 12V by midday. How much would it need to be at before I was to see 240W?

Thing is, if I am close the equinox, should I not at least be expecting to see around 200W? The highest I’ve seen is 150.........................
>>>>>>>>>>>>>>>>>>>>>>>>>>>
...this is pretty new to me.

Which is why I asked about your energy budget and other sources of charging right at the beginning.


And why folks have been trying to explain battery acceptance for you. As the batteries get full, they can accept less current, even if that current IS available. With your batteries at 12V, they are somewhat less than 50% based on voltage only, but that's resting voltage, which is not happening in your case because your panels are still connected, thus contributing to that voltage. This is why someone suggested running a load and checking then.


We need to know how low your batteries get overnight. So, how big is your bank and how much do you use overnight and daily in ahs?


One way to do this is to disconnect your solar one morning and run loads, get your battery voltage down just below 12V, wait til noon and reconnect and measure.




Understood that this is new to you, but none of us was born an electrician. This is a good learner kit for solar: https://handybobsolar.wordpress.com/
The Ample Power Primer http://www.amplepower.com/primer/primer.pdf
Battery Acceptance by Stu Battery Acceptance

[noelex 77]

As others have indicated, if everything is working correctly with a solar installation the maximum solar output should be producing close to the panel’s rated power. These periods of maximum power will only be brief. They will not occur frequently and will not have much influence on average power produced, but they are important because they indicate the system is healthy. Note the solar panels can only deliver this power if the controller is not in regulation. A simple test is to turn on a load higher than the rated solar panel output (in this case 300w).

A peak of 150/160w (or 178w as the app reports) from 300w (or 320w as the specifications indicate) of panels is poor and suggests a problem if you are not significantly exceeding these numbers occasionally in excellent conditions.

The Victron app reports quite a low maximum charging battery voltage of 14.03v over the last 5 days. This indicates that battery regulation has not influenced the result, so turning on a load would not have increased the output. This low maximum charging voltage also indicates that the batteries are likely to be at a low state of charge and that your charging input is not keeping up with your consumption.

[noelex 77]

Originally Posted by skipgundlach

From their site: "SunPower produces the highest efficiency monocrystalline solar panels available. Our X22 has a record-breaking efficiency of up to 22.8 percent, making it the best performing panel on the market today."

Note "Up to 22.8", not "23-25", % efficiency.

So, if real, some other company has stolen a march on SunPower. Who makes your flexible 23-25% efficient panels?

The panel’s efficiency can be calculated from the size and rated power.

In this case the panel efficiency is 16.3%. Not the 23-25% claimed (the claim may be for the cell efficiency, not the total panel efficiency, which is little misleading unless this is made clear).

[StuM]

Originally Posted by lawrence_craig

Ok, that’s very helpful. My batteries are normally at 12V by midday. How much would it need to be at before I was to see 240W?

Thing is, if I am close the equinox, should I not at least be expecting to see around 200W? The highest I’ve seen is 150.

With regards to temperature, they are slightly raised off deck to allow for cooling.

Sorry if some of the questions/statements are of, this is pretty new to me.

Your screenshot shows a high of 178. But yes, that's still low for 300W of panels where you are.

[Dsanduril]

Raised or not raised, your cell temperatures will be well above ambient temperature regardless of air flow. If your cells are 25% efficient then that means that 75% percent of the sunlight is not being converted to electricity. Depending on coatings some of the unusable wavelengths may be reflected, but otherwise all of that 75% is turned into heat. In essence, if you have sunlight at 1000 W/m2 you have a 750W/m2 heater working on your panel full time. Air flow cools that, but will never get the cells to ambient temperature. The best you can expect, with good airflow is about 30C above ambient.

Your panels (and pretty much all panels) are rated at a cell temperature of 25C. But the real-world NOCT (normal operating cell temperature) is closer to 55C. And your cells have a 0.5%/C temperature degradation rating, so you'll normally not see much more than 85% of their rating in the tropics. You might occasionally get sunlight at more than 1000W/m2 (the rating value) but it is unusual for any extended time at sea level in moist sea air.

Which gets us back to 240-250W would be what I would expect for a peak power output for your location. The '2 days ago' output is pretty telling, don't know what type of batteries you have, but for pretty much any chemistry a low of 11.16V and a high of 13.45V means the batteries were never really close to charged. In which case, if the sun was out and there was no shade I would expect ~250W.

I'd suggest disconnecting one panel from the controller and letting it all run for one day (a sunny day). Then do the same with the other panel. If there's a huge difference in output from one panel to the other then you probably have a bad panel (or a bad connection to that panel). If they both top out at 80-90W then I'd say maybe you got a bum deal.

[Jim Cate]

Well, another thing you can do is simply measure the open circuit voltage and short circuit current of each panel with good sunlight and see if they approximate the quoted values for the panels.

This test removes questions about the batteries condition and SOC from the evaluation of the panels. It is a definitive test for the panels...

Jim

[Dsanduril]

Jim is spot on, but it will require a decent meter than can handle measuring 10A. I made the assumption that wasn't in the toolkit.

[GILow]

Originally Posted by Adelie

With PWM or MPPT controllers it doesn’t matter to the battery what voltage the panels produce.

With PWM you want a panel with a voltage a little higher than the 14.5v (15-17v) so that the controller isn’t wasting much power.

With MPPT significantly higher voltage (16-21v) works just fine, the system trades excess voltage for more amps.

I did say "on the battery side".

[a64pilot]

Originally Posted by Dsanduril

Jim is spot on, but it will require a decent meter than can handle measuring 10A. I made the assumption that wasn't in the toolkit.

Test of course, but then test off the boat, no shading and correctly angled for 90 degrees to the sun.
Shading is my nemisis, I have a Radar pole, dual backstays and mounted on top of davits as opposed to on top of a tall arch, so I have almost always got shading.
Thing is even the mast can shade and it’s so far away that the shadow isn’t well defined so you don’t see it on the panels, but it’s there, robbing power.

[Jim Cate]

Originally Posted by a64pilot

Test of course, but then test off the boat, no shading and correctly angled for 90 degrees to the sun.
Shading is my nemisis, I have a Radar pole, dual backstays and mounted on top of davits as opposed to on top of a tall arch, so I have almost always got shading.
Thing is even the mast can shade and it’s so far away that the shadow isn’t well defined so you don’t see it on the panels, but it’s there, robbing power.

I think on boat testing is useful. One needs to pay attention to shading, of course, but each panel should get a period of unshaded sun each day ( clear skies, of course), long enough to make the very quick measurement. It need not be exactly at noon, either, just somewhere near mid day, for the angle does not change rapidly at that time. And it doesn't have to come up to max specs to show that the panel is not faulty. If you get say 90% of max, then his poor figures are not due to dud panels, and he can concentrate on other issues.

According to our Victron app, we've gotten over 400 watts from our two 200 watt panels several times so far, in the Sydney area in December. Takes a clear sunny day and low battery soc, and up the numbers pop. His performance is, in comparison, dismal, and something is wrong. Checking for a dud panel seems a good start to me. You could waste a lot of time searching for subtle problems that just ain't there!

Jim

[GILow]

Yes, the VOC and ISC tests are good and quick.

All of my panels were bought secondhand from a builder who’d stripped them from a house being demolished. I went to his place with the multimeter. He had set them all up in the sun as I had asked before I came out and I was able to run the multimeter over 20 panels in a matter of minutes. There was bugger all variation between the panels, maybe .1 or .2 volts and about the same in amps, as you’d expect from panels that were only a year and a bit old.

[a64pilot]

Originally Posted by Jim Cate

I think on boat testing is useful.



Jim

Of course. But if you don’t also test off the boat, your not sure if the issue is the panel or shading.
I don’t think all shading is obvious, for instance I seem to get very little power in a marina, I think from all the masts, but you don’t see the obvious shade line, cause of the distance, but it’s there.

[carlwk3c]

I routinely get 6-700W peak out of 2x350W LG monocrystaline panels mounted horizontally (no pointing for optimal sun angle on clear days. Days with some cloud cover 5-600W peak. Even on somewhat overcast days, I get 15-20 A of charge current. We’re currently in Puerto Rico