Solar Panel Output verse rating

[sailorboy1]

Originally Posted by noelex 77

I think one useful data point is the absolute maximium you have recorded from the panels.

What is the best you have seen?

I just looked though the controller history and over the past 30 days the max power was 240W. The average is 180-200W. I never really monitored the power the past 5 years so maybe that is all it even has done.

[StuM]

Originally Posted by noelex 77

This output is a little low.

No it's not. See post #12.

You should record resonably close to the rated output in ideal solar conditions especially if you angle the panels to the perfect orientation. Even a little over the rated output is possible.

What is the best you have seen?

A maximum solar azimuth of 48° is far from ideal solar conditions.
Does the OP has tiltable panels?

[StuM]

Originally Posted by sailorboy1

I just looked though the controller history and over the past 30 days the max power was 240W. The average is 180-200W. I never really monitored the power the past 5 years so maybe that is all it even has done.

240W is 83% of rated output. That's very good for this time of year at your latitude.

[noelex 77]

Originally Posted by sailorboy1

I just looked though the controller history and over the past 30 days the max power was 240W.

That is not dreadful, but it is lower than I would expect if everything was functioning well.

The first step is to measure the voltage drop. This will show up any bad connections and defective components like circuit breakers and switches that can sometimes develop high resistance in the salty atmosphere.

[noelex 77]

Originally Posted by StuM

No it's not. See post #12.

Yes, I agree Stu. The output is more reasonable, if the panels cannot be tilted, for a location at 26°N. I thought Sailorboy's position was closer to the equator.

[CaptRory]

Originally Posted by sailorboy1

I'm been watching my solar panel output the last few days. I'm currently in Palm Beach getting lots of sun. But in the middle of the day with my 5 year old 290W panel with a MPPT controller in full sun is only putting out 170-180W and I know the batteries aren't limiting it to that amount.

What are others experience in real output verse rating?

The batteries are always limiting the charge current depending on their voltage. You will get a lot more output at 12.2 than you will at 12.5. Check out this calculator. Amps to watts (W) conversion calculator

[noelex 77]

Originally Posted by CaptRory

The batteries are always limiting the charge current depending on their voltage. You will get a lot more output at 12.2 than you will at 12.5. Check out this calculator. Amps to watts (W) conversion calculator

With an MPPT regulator you will get more current (amps) if the battery voltage is 12.2v rather than 12.5v but not more watts. Sailorboy is talking about the output in watts.

It is important to ensure, when checking the solar panel output, that the controller is not in regulation. This will only happen at much higher battery voltages than 12.5v and Sailorboy has stated this was not a factor in his measurments.

[foufou]

Even at close to optimized angle my panels only produce about half of rating. What kind of load is used I the rating process? Might it be into a dead short?
.....................................don't believe everything you think...................................

[Wayfarer1008]

Being a person that helps maintain remote solar powered scientific instrumentation there are several factors that limit the output from the panels as time goes on.
First you have to understand is in my experience solar panels pretty much reach the end of their useful life after about 10 to 15 years. The reasons for this come down to;
#1 corrosion within the panel and wiring and
#2 UV damage to the surface of the panel elements in the form of oxidation.
#3 Temperature plays a big factor in how the panels perform. In the desert when the temperature get over 100 degrees F surface temperatures on the surface of solar panels can be as high as 400 degrees dropping the output from the panels to near zero. The cycling of temperature from hot to cold causes the panel elements to expand and shrink. this action tear's apart the elements adding to the breakdown of the panel.
As these three factors start acting on your panels slowly the output of the panels will diminish to the point that they are pretty useless and will have to be replaced.
Solar panel companies love to say that the panels will last for 20 years which they will but for all practical purposes 10 to 15 years is about it.

in a marine environment, if you are trying to get the most life possible out of your panels every so often go through and clean the corrosion off the wiring connections on a regular schedule and inspect the panels for damage since corrosion will be you biggest threat.
I hope this was useful

[donradcliffe]

Originally Posted by barnakiel

Testing single panels without a controller I always get to within 95% of the rated output.

The main limiters: the batteries (if not discharged), the controller (if too primitive or faulty), the wires (if too small or corroded), the panels (if faulty, non-angled, shaded or otherwise compromised), the Sun (if overcast, low or otherwise compromised).

Cheers,
b.

Testing single panels is best done by shorting the output and measuring Isc. That way you eliminate all of the battery/wiring/controller issues. You still should align the panel perpendicular to the sun, or account for the angle by using the cosine of it.

[epiic]

I use the most efficient solar panels on the market (Solara).

I have 700w total and often see 500+ watts in Florida with no clouds and no shading from my mast.

The most I've ever seen was 13 days ago @ 691w. That was on a colder sunny day.

[sailorboy1]

I don't have any corrosion and the 8 awg wiring to the panel and 6 awg from the panel iis way oversized as I sized it for 2 panels

[StuM]

Originally Posted by CaptRory

The batteries are always limiting the charge current depending on their voltage. You will get a lot more output at 12.2 than you will at 12.5. Check out this calculator. Amps to watts (W) conversion calculator

He's talking about how many Watts he is seeing out of his solar panels, not how many Amps are going into his batteries! He will get the same regardless of terminal voltage.

And who needs an online calculator to divide one number by another?

[StuM]

Originally Posted by foufou

Even at close to optimized angle my panels only produce about half of rating. What kind of load is used I the rating process? Might it be into a dead short?
.....................................don't believe everything you think...................................

You need to look at your siting, wiring and other components of your system.
Something is wrong.
At "optimized angle" any panel should be capable of producing close to their rating.

[buzzstar]

If I recall correctly, I saw a recent "non-marine" related "scientific" article that suggested panels lose ~2 - 4% of their rated capacity yearly, at least in part due to corrosion (of the panel electrical connections between or in the cells themselves, or even the plastic or glass(clarity?), I have no idea. Also I have long had the belief (no idea why) that panels were rated on theoretical, not actual, output.