Faulty bypass diode on solar panel?

[s/v Jedi]

Originally Posted by Nor

I have now tried some days with only using the 4 panels, before adding the 5th panel back to the mix. I have not seen the low 160W output anymore. I'm not sure why I only got 160 W that day. I've seen a couple of other times the output go down to 250W for a few seconds before going back up to 1000W+. Maybe this is the Victron searching for optimal output voltage. Not sure.

Anyway, the clear conclusion is that I get more kwh when having all 5 panels connected. So even thought it's not ideal it works pretty good.

I normally get between 8 to 12kWh daily.

I understand I could get an ever better output than I'm getting if I had more controllers. But it was easy and cheap to put the 5th panel next to the mast. Do you mean that I should rather have not put this panel there? Is there any other downside, will this panel take damaged from the more frequent shading and potential use of the diodes?
If no other downside and I'm getting more output than with 4 panels then I don't see why I shouldn't.

If you are so happy with the result then why start this thread? I simply show you what is wrong with the design and how to fix it. If you don’t like that and want to stick with how it is then why ask?

Edit: I am not trying to change your mind or anything; I know fully well it’s set on keeping what you got, but I post these comments so that other readers can avoid the mistakes you made and save themselves the troubles. I think my comments have made internal workings of solar panels and their bypass diodes clear to many who read this and also how the addition of a small extra controller for an extra panel fit in somewhere is the way to build it initially. Of course you want maximum panels but you need to connect them properly as well to get a good experience.

[Pete7]

Originally Posted by s/v Jedi

I know fully well it’s set on keeping what you got, but I post these comments so that other readers can avoid the mistakes you made and save themselves the troubles. I think my comments have made internal workings of solar panels and their bypass diodes clear to many who read this and also how the addition of a small extra controller for an extra panel fit in somewhere is the way to build it initially. Of course you want maximum panels but you need to connect them properly as well to get a good experience.

Jedi, thanks for the explanations on diodes, all useful stuff.

If i remember rightly he needs a high voltage for the Victron stuff, hence the panels in series. I suppose the 5th panel at the mast whilst not idea and will see different sun/shade patterns to the other panels, at least its a spare if one of the four fails.

[Nor]

Originally Posted by s/v Jedi

If you are so happy with the result then why start this thread? I simply show you what is wrong with the design and how to fix it. If you don’t like that and want to stick with how it is then why ask?

Edit: I am not trying to change your mind or anything; I know fully well it’s set on keeping what you got, but I post these comments so that other readers can avoid the mistakes you made and save themselves the troubles. I think my comments have made internal workings of solar panels and their bypass diodes clear to many who read this and also how the addition of a small extra controller for an extra panel fit in somewhere is the way to build it initially. Of course you want maximum panels but you need to connect them properly as well to get a good experience.

I started this thread as I wondered if the bypass diodes worked correctly. I now got a better understanding on how bypass diodes work, however I still doesn't quite understand it 100%, and according to your explanation (as I understood it) the output from the 4 panels shouldn't have been reduced much when the 5th panel is shaded? And I still don't know if it causes stress on the diodes on the 5th panel to potentially be active more often?

After more experimenting I see that it's not often I get such a low output of 140W so it's not really a big problem in terms of the output I'm getting.

I still don't quite see how it's a mistake of adding the 5th panel when I consider the small cost for an extra panel, vs the big cost of extra cabling, and additional controllers.

I'm very open to improving the setup if this could be done at an affordable price! But as I have a 48V battery bank I don't think there are controllers that connects a single 43V panel to a 48V bank, or are there??

Thanks for your input! When presenting my view and understanding, I'm looking to get any feedback and corrections that I can learn from.

[team karst]

“ I'm very open to improving the setup if this could be done at an affordable price! But as I have a 48V battery bank I don't think there are controllers that connects a single 43V panel to a 48V bank, or are there?? “

It would be possible to design a SMPS to be able to step down or step up on the fly. But its much simpler, easier and cheaper to only do a step down topography.

[s/v Jedi]

Originally Posted by Nor

I started this thread as I wondered if the bypass diodes worked correctly. I now got a better understanding on how bypass diodes work, however I still doesn't quite understand it 100%, and according to your explanation (as I understood it) the output from the 4 panels shouldn't have been reduced much when the 5th panel is shaded? And I still don't know if it causes stress on the diodes on the 5th panel to potentially be active more often?

After more experimenting I see that it's not often I get such a low output of 140W so it's not really a big problem in terms of the output I'm getting.

I still don't quite see how it's a mistake of adding the 5th panel when I consider the small cost for an extra panel, vs the big cost of extra cabling, and additional controllers.

I'm very open to improving the setup if this could be done at an affordable price! But as I have a 48V battery bank I don't think there are controllers that connects a single 43V panel to a 48V bank, or are there??

Thanks for your input! When presenting my view and understanding, I'm looking to get any feedback and corrections that I can learn from.

The reason for the impact is that the mppt doesn’t find a clear V-A graph for maximum power transfer as you get multiple peaks and valleys with arrays that are not homogeneous.

Also, as cells get a little shading, their output is reduced but probably not enough to bias a diode. This too confuses the MPPT algorithms.

But yes, a 40V panel isn’t enough voltage. You need 60V at minimum. There are boost controllers and while I once helped a member with a couple, it was many years ago and I think they have since gone out of fashion.

You can try to install another panel though for ideas, here is my new array in the picture… it’s four large panels but the outer two can slide in

[Nor]

Originally Posted by s/v Jedi

The reason for the impact is that the mppt doesn’t find a clear V-A graph for maximum power transfer as you get multiple peaks and valleys with arrays that are not homogeneous.

Also, as cells get a little shading, their output is reduced but probably not enough to bias a diode. This too confuses the MPPT algorithms.

But yes, a 40V panel isn’t enough voltage. You need 60V at minimum. There are boost controllers and while I once helped a member with a couple, it was many years ago and I think they have since gone out of fashion.

You can try to install another panel though for ideas, here is my new array in the picture… it’s four large panels but the outer two can slide in

Thanks, that makes sense about the the unclear V-A graph. I assume this will always be a bit of an issue on a boat that's moving back and forth, but more when the panels are further apart as in my case.

There is a setting on the Victron mppt for "partial shading detection". I've tried it both activiated and deactivated and I have not found a clear conclusion to if it improves it or not. Not sure exactly how it works.

[s/v Jedi]

Originally Posted by Nor

Thanks, that makes sense about the the unclear V-A graph. I assume this will always be a bit of an issue on a boat that's moving back and forth, but more when the panels are further apart as in my case.

There is a setting on the Victron mppt for "partial shading detection". I've tried it both activiated and deactivated and I have not found a clear conclusion to if it improves it or not. Not sure exactly how it works.

The MPPT algorithm will recalculate often because the optimal setting changes as the sun moves along the sky too, so any boat movement is also taken care of.

I have not discovered that partial shading detection yet. The best place to look for answers is the Victron community forum

[Nor]

Originally Posted by s/v Jedi

The MPPT algorithm will recalculate often because the optimal setting changes as the sun moves along the sky too, so any boat movement is also taken care of.

I have not discovered that partial shading detection yet. The best place to look for answers is the Victron community forum

Thanks for mentioning the Victron forum, I had a search there and found a massive thread about shadow issues for the RS MPPT controllers. Turns out several had reported similar issues as I experienced and they've been beta testing a new shadow detection feature that was just release a week ago or so! So I'm going to upgrade the FM and give that a go!

https://community.victronenergy.com/...anagement.html