100w panels

The 100 W panel rating is more of a theoretical solar panel wattage measurement based on Standard Test Conditions (STC). Normal Operating Cell Temperature (NOCT) is based on 80% solar radiation. Very unlikely you will get 100 W of power from your panels which would require a crystal clear sky with the panel pointed directly at the sun which constantly moves.

foxxxnick wrote:
I bought a Renogy kit with the hard panels (I.e. not the thin flexible panels) and mounted 3 100w panels on my van, for 300w.

Anyways, in really strong direct sunlight, I have noticed the app says I am getting over 300w of power … is it normal for panels to output over their rated output in direct sunlight with no obstructions? Of course the other possibility is one or a combination the app, bluetooth dongle device or charge controller are inaccurate.

I highly doubt the 300W of power. If the panels are laying flat in direct sun anywhere in the continental U.S. they will never give you the full 100W even with a MPPT controller since they will never be oriented perpendicular to the sun.

I have panels flat mounted on our trailer. We are near 45degrees latitude which hurts due to angle. Best I see with a MPPT controller is about 2/3 of rated power, in the spring or fall it's near 1/2.

Next the 100W is output using a MPPT controller, not your typical PWM controller, that alone means max ouput with a PWM controller will be aroun 75% of max rated. Reason is the 100W is based on an output voltage of 18-20V and XXX A. on a 100W panel thats around 5A (20Vx5A=100W) but a PWM controller will only deliver the 5A, 13Vx5A=65W. 14Vx5A=70A.

And finally the output rating is at a panel temperature of about 70F, touch your panel in the sun. It's well above 70F and panel output drops as temps go up. Drops with increased cell leakage current and 2.2mv/C in each cell output. I don'thave the exact data on hand but each cell is somewhere around 1.5-2V. so for each string at 18V you have 12-15 cells x2.2mv/C = a output drop of about 50mv/C. And a 20C rise is not unexpeced.

So even under absolute perfect clear sky on a typical summer day with the panel properly aimed, you will be very hard pressed to get the actual rated power from the panel after it has absorbed heat from the sun for more than a few minutes. And one seldom sees a perfectly clear day either.

So, long story short.... I don't believe your readout. 200W?? maybe 150W, likely on a clear nice day in the south at high noon

Now IF you could properly aim the panels AND use a MPPT controller what could you get from the panels? well, I have 160W portable panels that I connect to a good MPPT controller (Midnite solar Kid).

On a cool day 70F or so, in the summer on a clear day charging a really dead battery bank (30%SOC or s0) aimed "dead on" (trick use s TP tube on the panel and adjust for zero shadow) I've never seen a full 160W out of the panels. 120 yes, even 140 briefly till the (a) panels started to heat up and (b) while they stayed perfectly aimed for 15 minutes or so. Daytime average I figure 100W is a good average since I'm not going to aim the panels every 30 minutes or so.

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Well, I have to disagree with some of the opinions given here. I have two panels with a combined rating of 370 watts. Panels are 11 years old. On a recent trip to Wyoming this summer, I recorded 411 watts output. Of course I had some ideal conditions beyond the standards by which panels are rated. I was at about 9000' elevation and the wind speed was greater than 1 m/s. However, the temperatures were much higher than 20C and though the panels were tilted somewhat toward the sun, certainly weren't perpendicular to the radiation. I often see peak watts greater than rated panel output.

I have seen more than rated power once. End of May at 7500' elevation in Arizona.
So, it is definitely possible to see more than rated output.
I might add that partly cloudy days yield a higher "peak wattage" for the day. I assume it is because the panels have a chance to cool down a little during cloud cover.

Google "cloud edge effects"
However, I think measurement inaccuracies are a more likely answer in this instance.

I will agree that high altitude and/or a breeze is a benefit. First you may get solar radiation in w/sq meter above the standard reference due to the altitude. Next any breeze helps keep temperatures down. And usually high altitude= lower temperatures.

So, while I've never seen output> rated, I will change my opinion and say it is possible. not likely to occur very often, but is possible.

Also years ago, like when I bought my panels there were rated under ideal conditions. Solar engery 1000W/sq meter, cell temp 77F, 500ft altitude.

Since then the NOCT rating has been used as well which is more realistic. (Normal operating conditions and temperature) It assumes 800W/sq meter, 500ft altitude and 68F AIR temperature and a 2mph wind. Note the use of AIR temperature NOT cell temperature.

so using NOCT I can see panels oeak reading exceeding the rating on a nice sunny cool day with a nice breeze especially at high altitude as long as they are aimed within reason. I wouldn't expect that reading to last for very much of the day.

ya I quite often see 350 watts out pf my 325 watt panel on my rv also and I'm farther north. in September and October, I'll only see about 320 watts out out of it.

Now on my 5th wheel I have 480 watts of 12v panels, and I have only seen 350 max out of them. my one 24V 325-watt panel on a MPPT controller consistently puts out more power than my three 180-watt 12V panels on a PWM controller

Looking into putting solar on my home, every place I have received an estimate from told me they are rated for the voltage at the end of their lifespan, so it is quite possible they could put out more power when they are new. now whether this is true or not I don't know

My new CIGS panel “taped” to my TT’s rounded dome front has put out more than the 100watts it’s rated for. Using an EPEver MPPT 30 amp controller. At its storage location, the panel faces due south.