Bypass diode can cause panel to blow???

[lobsters]

At the recommendation of my installer, Brian Boone, I went with a completely parallel solar installation, not series-parallel. Brian has a very good reputation, so I figured he knows better than I do.

He was helping me with a problem a few weeks ago (a panel was only outputting about 1/3 current), and we talked about that. I asked whether the panels had bypass diodes to eliminate the shadow problem in series installations. He said no, that they had been removed by his supplier because they had found a failure mechanism where the presence of the diode could cause the panel to fail--I think he said when / if the leads got shorted.

I have a fair amount of electronics background, and this makes no sense to me, but I could see that the diodes had definitely been removed--I could see where they had been clipped out.

Have any of you heard about this type of failure? Or can you speculate on a mechanism that might cause it?

By the way, the amount of decrease in output of a panel when shadowed is startling. Simply the shadow of a single hand can cut the output current by 75% or more.

-Al

[TucsonJim]

Hey Al - Hope you're doing well.

I have never had an issue with my panels (which include bypass diodes). I believe the information you have been given is either incomplete or inaccurate. Bypass diodes actually can prevent damage to a series of PV cells by preventing "hot-spotting". The attached article is pretty educational on the benefits of BP diodes in a circuit. I would never "clip" them out of the circuit because of the advantages they provide.

http://www.alternative-energy-tutori...ass-diode.html

Jim

[howson]

At the recommendation of my installer, Brian Boone, I went with a completely parallel solar installation, not series-parallel. Brian has a very good reputation, so I figured he knows better than I do.

He was helping me with a problem a few weeks ago (a panel was only outputting about 1/3 current), and we talked about that. I asked whether the panels had bypass diodes to eliminate the shadow problem in series installations. He said no, that they had been removed by his supplier because they had found a failure mechanism where the presence of the diode could cause the panel to fail--I think he said when / if the leads got shorted.

I have a fair amount of electronics background, and this makes no sense to me, but I could see that the diodes had definitely been removed--I could see where they had been clipped out.

Have any of you heard about this type of failure? Or can you speculate on a mechanism that might cause it?

By the way, the amount of decrease in output of a panel when shadowed is startling. Simply the shadow of a single hand can cut the output current by 75% or more.

-Al

Al,
Assuming I understood what I just read and based on the fact that your installation is 100% parallel, the diodes aren't needed. Your setup won't encounter a situation where (in series) a shaded panel acts like a "semiconductive resistance" (quoting the article). The only result is less amperage from the shaded panel. The rest of your parallel panels will continue to produce power.

TucsonJim -- did I get that right?

For the failure mode...my guess is if there is a group of panels in series their voltage level is (obviously) higher than a single panel. The diode(s) are designed to handle bypassing the current for a single panel--not a group of panels. If a group of panels in series (in full sunlight) had it's leads shorted, this could overwhelm and burn out a diode.

But that's just an educated guess.

-Howard

[TucsonJim]

Al,
Assuming I understood what I just read and based on the fact that your installation is 100% parallel, the diodes aren't needed. Your setup won't encounter a situation where (in series) a shaded panel acts like a "semiconductive resistance" (quoting the article). The only result is less amperage from the shaded panel. The rest of your parallel panels will continue to produce power.

TucsonJim -- did I get that right?

For the failure mode...my guess is if there is a group of panels in series their voltage level is (obviously) higher than a single panel. The diode(s) are designed to handle bypassing the current for a single panel--not a group of panels. If a group of panels in series (in full sunlight) had it's leads shorted, this could overwhelm and burn out a diode.

But that's just an educated guess.

-Howard

Actually, the failure mode can be internal to one panel also Howard. If a portion of a panel gets shaded, the bypass diode goes into reverse polarity which allows it to conduct around the shaded area. This can prevent hotspots and the resultant damage that can occur.

Jim

[howson]

Actually, the failure mode can be internal to one panel also Howard. If a portion of a panel gets shaded, the bypass diode goes into reverse polarity which allows it to conduct around the shaded area. This can prevent hotspots and the resultant damage that can occur.

Jim

That's a quality issue then, right? A diode is about as basic as it gets--if the diode(s) a manufacturer inserts into a circuit can't handle the load it is designed to carry that would make me suspect the other components that make up the panel.

[TucsonJim]

That's a quality issue then, right? A diode is about as basic as it gets--if the diode(s) a manufacturer inserts into a circuit can't handle the load it is designed to carry that would make me suspect the other components that make up the panel.

I may never need a capacitor on a circuit board either. But I don't snip them out like the OP is reporting. The panel manufacturers insert these components for a reason. I don't know of any panel manufacturers that don't install bypass diodes anymore.

[lobsters]

Thanks guys. I'll do some more digging. I won't be able to participate in the discussion if there is more except in the dead of night, because Verizon is completely swamped during the peak of Quartzsite season.

[KamFlyer]

He was helping me with a problem a few weeks ago (a panel was only outputting about 1/3 current), and we talked about that. I asked whether the panels had bypass diodes to eliminate the shadow problem in series installations. He said no, that they had been removed by his supplier because they had found a failure mechanism where the presence of the diode could cause the panel to fail--I think he said when / if the leads got shorted.

I have a fair amount of electronics background, and this makes no sense to me, but I could see that the diodes had definitely been removed--I could see where they had been clipped out.

-Al

Hi Al. I am curious as to what panels you have? I have the same panels Brian typically uses but did not get them through Brian but direct from the distributor.
-Rob-

[Ed & Cathy K]

I may never need a capacitor on a circuit board either. But I don't snip them out like the OP is reporting. The panel manufacturers insert these components for a reason. I don't know of any panel manufacturers that don't install bypass diodes anymore.

Jim,
What about these panels? I spoke with FredMcNeeley before I bought my panels, and ask if they had bypass diodes. He said his panels were like everyone else's. I heard recently they don't have diodes.

[TucsonJim]

Jim,
What about these panels? I spoke with FredMcNeeley before I bought my panels, and ask if they had bypass diodes. He said his panels were like everyone else's. I heard recently they don't have diodes.

Ed - I looked at their specifications page and it doesn't say. If you pop the cover off and take a photo of the area I identified in the picture, I can probably let you know.

Jim

[lobsters]

Here are my label and picture inside the junction box. The panel was manufactured with three diodesb the middle one was snipped out.
-Al

[lobsters]

I just talked with Brian. He said this is done by HighTec on all their panels. I'd really appreciate it if others with HighTec panels would open the box and check / take a pic. Thanks!

-Al

[TucsonJim]

I just talked with Brian. He said this is done by HighTec on all their panels. I'd really appreciate it if others with HighTec panels would open the box and check / take a pic. Thanks!

-Al

That is so odd that they would design and manufacture a panel with the diodes in place only to snip them out?

Jim

[Ed & Cathy K]

Ed - I looked at their specifications page and it doesn't say. If you pop the cover off and take a photo of the area I identified in the picture, I can probably let you know.

Jim

Here's a pic looks like the diode is snipped off in the center. I think HiTech owes us some answers.

[Ed & Cathy K]

Ok guys I got some answers. I had a long discussion with Jesse McNeeley today, he started the company with his dad Fred. They do recommend running their panels in parallel. Because they have no control over the number of panels someone can run in series. The specs on the diode in my panel is "THY2550 2cz20r45 25A 50V 20A 45V MBR2550 Schottky diode”. Apparently, the increase in voltage can overheat the diode and can cause a fire because the IP68 box isn’t rated for the higher temps. The diodes originally in my box would handle my 2 panels in series, 3 panels would exceed the 50volt of the diode’s specs. Jesse is willing to change out my boxes in April when I stop at his shop.