Series string shading summed up in 4 pictures

[timselectric]

Not sure if reversing diodes are in the previous 4-pages, but it's a key note I didn't learn until days before ordering the combiner box (Whew).

Several of us have tested blocking diodes. (Assuming that is what you are referring to) and have found them to be of no benefit. But they can create problems since they add connection points (possible failure points).

 

[EastTexCowboy]

I buy all of my bananas in a parallel bunch.

Do you think Will would go bananas and ban folks if about a week from now several people (not naming any names) posted asking him to make a video on shading?

 

[JWLV]

I've covered this before actually. People don't watch my older videos sadly. People keep requesting me make videos I've already made and it's driving me bananas lol

I wonder how many people here have watched your video of the robotic arm when you had longer hair

 

[farmhand]

Several of us have tested blocking diodes. (Assuming that is what you are referring to) and have found them to be of no benefit. But they can create problems since they add connection points (possible failure points).

Not to sure if Blocking & Reversing Diodes are the same... let me google here..... yes, they are the same but see video below why I needed these. I learned this in one of @Will Prowse Prowse videos on combiner boxes:
Basically my 6string array has minor string-shading issues due to a tree. These reversing (possibly blocking) diodes are to prevent a shaded string from pulling voltage down off my producing strings.
*We had to put the array on the coop due to zoning restrictions/taxes, wasn't my first choice.

Maybe Will will chime in here

Here's the video, which after I made damn sure to order a PV Combiner Box with these.

another video mentioning them.

Here is the unit I order for other newbies, and like the video above many of the connections were not torqued properly, always check*
6-String PV box with Diodes

 

[timselectric]

Not to sure if Blocking & Reversing Diodes are the same... let me google here..... yes, they are the same but see video below why I needed these. I learned this in one of @Will Prowse Prowse videos on combiner boxes:
Basically my 6string array has minor string-shading issues due to a tree. These reversing (possibly blocking) diodes are to prevent a shaded string from pulling voltage down off my producing strings.
*We had to put the array on the coop due to zoning restrictions/taxes, wasn't my first choice.

Maybe Will will chime in here

Here's the video, which after I made damn sure to order a PV Combiner Box with these.

another video mentioning them.

Here is the unit I order for other newbies, and like the video above many of the connections were not torqued properly, always check*
6-String PV box with Diodes

That video actually started the conversation.
So, we tested it.
We found that if any light exists, the VOC is always enough to serve as the "blocking".

 

[timselectric]

Current flows from the higher voltage source to the lower voltage source.
And a partially shaded string still produces a high enough voltage. To block Current from flowing in its direction.

 

[Zwy]

I mean I can just post the data from my Tigo App showing the crazy difference the optimizers see and save. I have 1 panel that gets shaded by an eve of my porch. The 1 panel shows under performing until about 1pm, but the other 10 in the string (11s2p setup) are not restricted at all.

If you have 2 parallel strings (String A and String B) and the bypass diodes activate on one of the panels in String A, will that reduce the output of String B?

 

[niktak11]

Hey @Will Prowse... I would have expected you, of all people, to find a better place to site your panels

It's time for Will to buy 100 acres of land in the desert to turn into a solar paradise

 

[Solar Guppy]

What I see is you have identified an issue, you haven't shown what the cause is, but are assuming it is the bypass diodes not working as expected. Based on the fact the voltage is so high, I would challenge that conclusion. if they the diodes were not present, you would have very low voltage.

To expand further, you have some device, it is job is to load the array to extract maximum power. In the case of shading, you get what is referred to multi-hump mppt and I suspect, your charge controller doesn't have the code to deal with this situation.

This is my professional area of experience when I was active in GT inverter and Charge controller designs. I wrote code specifically for this use case and ran for years testing all sort of environmental conditions to improve my work, which I have multi patents for.

One Idea would to get a MorningStar Tristar 600V as I know first hand the code that runs these uses a periodic sweep based method and should have no issue with the progressive shading and give it a try in your shown problematic condition.

What most likely don't know that mppt tracking is a speciality knowledge wise and every company is a separate effort code wise. Every company seems to claim there products do 99.9% effective mppt harvesting, yet there are no standards to validate such claims

Bypass diodes are intended for series strings, that are NOT paralleled, which with the panel sizes today and multi channel input channel AIO's shouldn't be an issue.

 

[timselectric]

Bypass diodes are intended for series strings, that are NOT paralleled, which with the panel sizes today and multi channel input channel AIO's shouldn't be an issue.

I tested this for two weeks each, with and without.
And not bypass diodes, Blocking diodes.
Blocking diodes are used for parallel strings.

Edit: maybe you weren't referring to the current conversation.

 

[cs1234]

@Will Prowse @Solar Guppy

Dang Will. Solar Guppy is saying your "Victron Energy SmartSolar MPPT RS 450/100 or 450/200" sucks and can't deal with the multi hump!

Now we gotta know. That's not a cheap charge controller. We need a charge controller showdown!

 

[Jennifer]

The only way around this is with optimizers,

... .or to live in the middle of 65 acres with not a speck of obstruction in the sky, run an MPPT RS450/200 with an array facing each direction and just listen to your PV cable hum.... ahhhhhhh the serenity...

 

[Will Prowse]

@Will Prowse @Solar Guppy

Dang Will. Solar Guppy is saying your "Victron Energy SmartSolar MPPT RS 450/100 or 450/200" sucks and can't deal with the multi hump!

Now we gotta know. That's not a cheap charge controller. We need a charge controller showdown!

Actually if you listen carefully, I say the fast and multi point tracking doesn't help much ? but I'm sure most glazed over that sentence.

 

[Solar Guppy]

Dang Will. Solar Guppy is saying your "Victron Energy SmartSolar MPPT RS 450/100 or 450/200" sucks and can't deal with the multi hump

I didn't use the word suck and have no knowledge of what was harvesting the energy, but I can claim that any device I tested, without exception I found issues with.

The images show when shaded a higher voltage ( 421V @ 201W ) and when not shaded ( 387V @ 2465W ), that is clear evidence the array is not being loaded to harvest energy and not the panels fault.

Since Will has a house full of devices, just throw an AIO or GT to grid sell energy on one of the arrays to see how it works vs the charge controller if he is interested in understanding the cause or to confirm.

I've dealt with this first hand over 21 years ago on my Xantrex Suntie work, in a very similar situation of progressive ( un ) shading of one of my beta team members arrays, so I had to add code to specifically trigger on increasing array voltages typically seen as Will has shown.

 

[Solar Guppy]

Actually if you listen carefully, I say the fast and multi point tracking doesn't help much ? but I'm sure most glazed over that sentence.

Just because a manufacture uses a word salad of nifty terms for their products, doesn't really mean much. This is a mppt tracking issue, and I know there are products that would not get hung up with this test case.

As will points out, most production is mid morning to mid afternoon, and most would never know there is some harvest not being captured. That doesn't mean bypass diodes don't work.

This is also a String Array issue, which with current optimizers or micro inverters per panel ( Enphase and the like ) don't have and due to code requirements for RSS, voltage limits outside of the panel area Strings are not as common as they use to be.

Even my current Solis 5G's has some really odd tracking in the early morning, late afternoon when one channel gets hung up at minimum start voltage, in the noise really harvest wise, and at time I wish I didn't know what I know!

 

[cs1234]

Actually if you listen carefully, I say the fast and multi point tracking doesn't help much ? but I'm sure most glazed over that sentence.

Yeah, but you didn't talk about a multi hump. That's the straw that breaks the camels back. ?

 

[niktak11]

I'm curious of examples of MPPTs that do handle this situation properly

 

[cs1234]

I'm curious of examples of MPPTs that do handle this situation properly

Only one we know of so far is ugly as sin. Looks like it came out of the 1980's. Or maybe an old internal computer cd-rom drive with a heatsink attached on the end of it.

 

[sunshine_eggo]

Actually if you listen carefully, I say the fast and multi point tracking doesn't help much ? but I'm sure most glazed over that sentence.

I heard it, but I'm honestly a little surprised the MPPT didn't pick up the peak power at the lower voltage. I've seen these things do sweeps every 10 minutes or so. I just don't know if the sweep progresses low enough to capture the higher output at the lower voltage.

Maybe trend it with VictronConnect tomorrow morning tracking PV voltage and PV current???? PLZ?

 

[Solar Guppy]

Only one we know of so far is ugly as sin. Looks like it came out of the 1980's. Or maybe an old internal computer cd-rom drive with a heatsink attached on the end of it.

View attachment 141065

MorningStar Tristar's are very reliable and when released 10 years ago was the only high voltage charge controller ( stand-a-lone ) available, though the XW High Voltage mppt was close.

Function ( reliability ) over beauty is a good thing for hardware that you want to last for decades! , they are all still in production and leading performers for what they do.