Recent loss in charge input

[BlackwaterPark]

Hey there, so over the last week I've noticed a pretty drastic decrease in my daily charge... By what seems to be about a 2/3rds average loss. The panels are a pair of Canadian solar 250w panels wired in series, into a classic 150, into a 24v bank.  Today, with full sun, I came back to a total charge of 600 watts, whereas I would normally expect to see at least 1.5-1.8kwh.  I checked all the connections and they are good. The only thing I can see is that one particular cell appears to have "branched" for lack of a better word... It looks like the top of a tree as seen from a bird's eye view, though it is not cracked in the slightest, the glass itself is fine. The pattern is confined strictly to that one cell. Any ideas on how to trouble shoot this?

[Westbranch]

Not sure this will work, but you could try covering each panel separately and check to see if there is a difference in output, I am thinking that one will give you close to your measured out put and the other very little... if it is damaged.

How is your angle of incidence?  close to optimal?

[BlackwaterPark]

I have the panels set to 30° approximately.  They are fixed. 

[boB]

What is your PV's  Voc and what is the Max Power Point voltage that the input runs at ?

boB

[BlackwaterPark]

Hi Bob, the voc is 37.2, the ooc is 30.1v.  I'm uncertain on how to answer your second  question... Is that a property of the panels or a setting on the classic?

[dbcollen]

I suspect the cell that has "branched" has overheated and what you are seeing is burned EVA on top of the cell. If that is indeed the case it would likely cut all output from that panel and possibly consume some power from the other panel.

[Resthome]

Hi Bob, the voc is 37.2, the ooc is 30.1v.  I'm uncertain on how to answer your second  question... Is that a property of the panels or a setting on the classic?

What is the Vmp spec on the panel you are using?

[Westbranch]

John, it looks like these are the ones,  http://www.civicsolar.com/product/canadian-solar-cs6p-250p-250w-poly-blkwht-solar-panel

vmp = 30.1v

[boB]

I'm afraid that 37 volts, open circuit (Voc) is on the edge of being too low for a 24V battery bank.

37Voc would put your max power point voltage (Vmpp) around  0.80 X 37 = 29.6V
which is close to your 30 volts you mentioned.  It may be that the MPP voltage is
even lower than 80% of Voc which is even worse.

Check to be sure that Low Max is turned ON in the TWEAKS menu to enable the PV input
to be as close as possible to the battery voltage also.

What is the battery voltage and charge mode when you see low power ?

Maybe the stage is Absorb or Float, in which case the power can be very low
due to it not needing much power in those modes.

boB

[Resthome]

I suspect the cell that has "branched" has overheated and what you are seeing is burned EVA on top of the cell. If that is indeed the case it would likely cut all output from that panel and possibly consume some power from the other panel.

dbcollen may be correct if you can see a problem on the panel.

http://www.europe-solar.de/catalog/index.php?main_page=page&id=44

[BlackwaterPark]

Bob, under tweaks I don't see a "v max” setting. It just says vbatt on left, then " offset", then Vpv on right.   Under vbatt, it is 0.00, and under that 24.8.   Under Vpv, 0.0, and 8.4 under that.

[Westbranch]

it says your battery  V = 24.8 and the PV is 8.4 (maybe) and neither of those voltages are being adjusted or corrected (0.0)
The PV voltage, if the sun is gone , is a 'remnant' and will slowly drop after sundown but usually will be at about 50% of normal V during the evening, eventually it  zeros out...

ps 24.8 under no load is below 80% charge..

hth

[BlackwaterPark]

Ah, NM...I found the sub menu. Lmax is on.  I located some of the problem I believe.... There appears to be some shading from pines among the ridge that didn't seem to be a problem last year.  It's been hard to notice this year seeing as I'm spending every daylight hour working now. Today I was able to stay home and watch what was going on. Under full sun when there was no shading, I was seeing about 16 amps coming in, so I guess that's not too bad.  But with shading it dropped down to between 1 and 3 amps for most of the day... Which would explain my 600 watt harvests, heh. 

[BlackwaterPark]

Oh man, below 50% charge? That's not good... My Wb says 77%.  Wonder if it's been wrong this whole time..

[Westbranch]

Whoops, my bad, that should have read 80%.... your WBjr is probably pretty close...  sorry 

have you read this info from NAWS?

http://www.solar-electric.com/deep-cycle-battery-faq.html/#Battery%20Voltages