100w panels

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.