Panels not producing the same voltage

Can't see the diodes

10:15-11:30 Tested 36 panels in my South array, voltages where all relatively the same from yesterday.
22 panels in the 27v-28v, 8-9a
1 panel around 32.5v, 8-9a
13 panels in the 40-42v, 8-9a

Amperage when i started measuring this morning was around 7.6a, and increased up to 9a by 11:30, i went back and measured the amperage of some of the panels that were originally around 7.6a, and now they are around 9a.

Measured amperage of a single panel at 10.3a at 27v around 1:00pm

And the installer is long gone. A $50 panel tester is a smart investment when buying something from the back of a truck. Using a voltmeter and current clamp are a poor way of testing. I'd build a tester with two 100W incandescent lamps in parallel to put some load on them. Bypass diodes are usually about every 8-9 volts. With a diode or two shorted, those numbers would make sense.

efficientPV said:

And the installer is long gone. A $50 panel tester is a smart investment when buying something from the back of a truck. Using a voltmeter and current clamp are a poor way of testing. I'd build a tester with two 100W incandescent lamps in parallel to put some load on them. Bypass diodes are usually about every 8-9 volts. With a diode or two shorted, those numbers would make sense.

Click to expand...

Do you have a recommendation for a tester?

I have the guys facebook page, his phone# and address, I'll get ahold of him!

I just want to know everything that i need to know, have my ducks in a row so to speak, before I contact him.

I'd just grab a tester off of Amazon. Easy enough to replace if you have an issue. Cheap enough that one bad panel could pay for it.

Ordered an elejoy

Wheres a good place to get bypass diodes?
I sent a message to Q cells asking for diode specs, but haven't gotten a response yet.

Your first port to call is definitely going to be the seller, he may not know or understand how to test the panels so it could be a genuine..... how could we put it mistake LOL

I bought the panels from him 2+ years ago, so I'm not expecting much

15SQ045 is a excellent general replacement regardless of the package type used. I bought 25 for under $10 on ebay. That might just be the number you need if you get thru the potting. Give up on the manufacturer, this is not a consumer replaceable item.

Received my Elejoy solar panel multimeter, so I'm back at it.

Testing conducted between 1115-1135am and 1200-1215pm, 245pm sunny with some clouds.

Readings from some of the panels that were giving me low voltage (27v)

Pmax 175.5w 188.5w 208.6w
Vmp 22.86V 20.91V 23.05V
Imp 7.68A 9.05A 9.05A
Voc 28V 27.96V 28.73V

Pmax 177w 184w
Vmp 23.05V 20.24A
Imp 7.68A 9.05A
Voc 27.85V 27.55V

Pmax 173.3w 184.5w
Vmp 22.57V 20.39V
Imp 7.68A 9.05A
Voc 27.77V 27.7V

Pmax 175.8w 176.7w
Vmp 22.9V 22V
Imp 7.68A 8.04A
Voc 27.9V 27.7V

Readings from some of thep anels that were giving me (41v)

Pmax 265.5w 287.9w
Vmp 34.65V 31.96V
Imp 7.68A 9.01A
Voc 41.8V 41.6V

Pmax 271w 289.5w
Vmp 35.31V 31.99V
Imp 7.68A 9.05A
Voc 41.93V 41.6V

Pmax 274w 299.9w 313.5w
Vmp 35.68V 32.84V 34.65V
Imp 7.68A 9.05A 9.05A
Voc 42.9V 42.63V 42.63v

Pmax 272.6w 292.2w
Vmp 35.46V 32.29V
Imp 7.68A 9.05A
Voc 42.93V 41.67V

Its looking like these are the best numbers from the panels with low voltage

208.6w
23.05V
9.05A
28.73V

And with what i assume is the correct voltage

313.5w
34.65V
9.05A
42.63V

Temperature was in the Low 80's

Dupe

Looks like you have all of the proof you need to ask for help from the seller. Hope it goes well for you.

So is this most likely a diode issue, I don't know what else it could be.

Yeah, I'm gonna contact the seller. I'm not expecting much though.

Yep. This video will give you a good idea on how they work.

So reviving my thread, i've decided to replace the diodes in my bad panels. I scraped away the goo inside the junction boxes, my panels have the square shape diodes. The part#'s are
PEC 9416
SB3045DY

When i search the full part# i get links to Chinese companies, as far as I can tell these are oem specific.

So if i just search 3045 diode i get results, but I'm not sure what I'm looking for. Is the SB prefix and DY suffix important for matching the diodes?

Any help would be appreciated

After lightning I just used diodes out of old PC power supplies. There was one difference between them. The screw wouldn't fit thru the hole and had to be drilled out slightly. So just look for a 30A 45V TO-220 diode. Hold the body in some channellocks as it will try to get away from you and tear out the leads.

Never seen that before. That diode is a D-pack which is soldered into the base of that brass frame. The heat to remove that could damage the panel. I would consider looking at the space above it to see if more could be dug out and a 15SQ045 fit in there or two smaller diodes in parallel. If you don't encounter shading a small diode would do.

In parallel? I think existing diodes are shorted.

Try clipping or cut with dremel tool at package body. Then solder new diode to leads.

The fact these have body pad could mean they're well heatsinked. Failure of diodes during shade when others have full sun is common; not engineered or full current.

It is good to test at Vmp/Imp. I discovered only some bad panels are found by Voc/Isc. I loaded them to approximate maximum power point with a couple electric space heaters in parallel.