Solar charging with some shade

[2oldman]

I'm facing west today, so I'm getting a pretty good shadow on one of six series-connected panels. Panels are all around 135w @ 12v.

Shade is on the far-left panel - about half of it:




Not a bad charge for that big of shade- 51.9v x 10.6a



The shaded panel is the last in a series string. It's a Kyocera. Looks like the diodes are working well.

[BFL13]

I am not sure the OP has confirmed that front panel is Mono. I thought so from all the big white spots on it.

If the Mono is confirmed by the OP, I wish JiminDenver would comment, in case I didn't use his results right.

By now, the poor OP probably wishes he never posted the pictures. 🙂

[CA_Traveler]

smkettner wrote:

BFL13 wrote:

2oldman wrote:
74 x 7.5 = blanket on panel
74 x 7 = no blanket on panel

Did not expect Imp to be less with no blanket. Is the sky steady for same insolation while testing?

Needs more samples to verify unexpected results. Interesting!

Keep in mind the load is not fixed. The MPPT controller adjusts voltage and current to maximize wattage.

Plus testing in the wild like this involves many other variables unlike a lab test of just solar panel performance - not to mention mixed technology panels.

But his system works well and that is what counts most.

[time2roll]

BFL13 wrote:

2oldman wrote:
74 x 7.5 = blanket on panel
74 x 7 = no blanket on panel

Did not expect Imp to be less with no blanket. Is the sky steady for same insolation while testing?

Needs more samples to verify unexpected results. Interesting!

Keep in mind the load is not fixed. The MPPT controller adjusts voltage and current to maximize wattage.

[BFL13]

I wonder if that one Mono in low light/shoulder hours would be the same as having a shaded panel in the string during that time.

If I understood JiminDenver, the Mono would act the same as the Poly midday, but lose more output than the Poly in the shoulder hours. So having the Mono in a series string of Poly panels would not be ideal.

That would mean the OP has the one Poly shaded midday and then just as that clears up as the sun moves around, the Mono starts acting like it is shaded.

A possible test for that might be during when all panels are clear of shade in a shoulder time, to put the blanket over the Mono and take string readings, and then quickly put the blanket over a Poly and take string readings. Losing the Poly should hurt more if this theory is correct.

[BFL13]

Sun moves around at 15 degrees per hour, so you have ? two hours before and after noon (when sun is South directly on) with shaded panel?

You could do some math and see how that four hours reduced input wattage (and so output charging amps) mid-day affects the daily AH haul. Knowing your AH usage, you can then see if any action is "worth it"

It is possible that you are getting more from having 6 in the shoulder hours than you are losing from shading mid-day, so going to 5 all day would be a mistake. However, it needs the math to know.

As the sun gets higher each day from now on, the shading will change too. If it gets over half way to the top now, but later only gets almost half way, then that changes from two to one diode in play, so that would be a "marker" for taking a new set of readings and more AH use/haul calculations.

Or if you are getting bags of AH now, as is, relax and forget the whole business! 🙂

[2oldman]

yes, up from bottom. I was going up there again, but we're into Absorb now. Not sure if that matters.

We're at 91.0 x 6, with no shade, sun at about 30° off the perpendicular.

[BFL13]

2oldman wrote:
about 1/3

Was that shade 1/3 up from the bottom so that the upper two columns were completely un-shaded? ( if a cell or two on the end of a column is shaded, that kills the whole column AFAIK) So we can say if one diode only was by-passing or both were.

IMO more sampling would be a good idea before doing anything. I don't have any way to put panels in series and try it out to help verify the testing, so others who know how this is supposed to work will have to explain it all. Then maybe alter the set-up if indicated.

Very interesting!

[2oldman]

about 1/3

[BFL13]

How much of the panel was shaded for the no-blanket reading?

[2oldman]

Readings taken within a minute of each other.

[BFL13]

2oldman wrote:
74 x 7.5 = blanket on panel
74 x 7 = no blanket on panel

Did not expect Imp to be less with no blanket. Is the sky steady for same insolation while testing?

Needs more samples to verify unexpected results. Interesting!

Also, be a chance to shade/cover the lower two columns leaving upper 18 clear and see what happens to readings. The OP photo shows part of the upper 18 shaded too, so AFAIK that is like shading it all? Except it isn't when compared with covering it all with a blanket?

[2oldman]

74 x 7.5 = blanket on panel
74 x 7 = no blanket on panel

[2oldman]

BFL13 wrote:
Looking at smk's drawing, it says if the panel is all shaded, all the current goes through the three by-pass diodes. What current, when it is all shaded?

The current in the rest of the circuit.

[BFL13]

Looking at smk's drawing, it says if the panel is all shaded, all the current goes through the three by-pass diodes. What current, when it is all shaded?

A blanket cover "black-out" is not the same as the "shade" in the OP photo, where the shade is "lighter"

The vertical panel in front looks like a Mono among the 5 Poly ones. JiminDenver had trouble mixing Mono and Poly in low light ISTR. I bet he would sell the Mono on Craigslist and then have no shading plus have some extra $ to pay for the 48v upgrade 🙂