Adding 2 more panel, 400 watts total, 100 amp hr battery

circus

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When the temperature drops below 5°C, the BMS diverts incoming power to the heaters rather, than the battery cells,
That's better, I imagined a 4 amp drain on the battery which at 0°F would be 24-7. If I build a battery I'll need to find a bms with that feature.
 

chrisski

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I'm having a hard time finding a 40 amp class T-Type fuse. They seem to be for much larger amp. rates systems, like 200 and above.
I need to look at this myself. I’m finishing a 25 ah battery build. I need to do some research. Perhaps low amperage batteries don’t need as high of an AIC fuse. I’ll have to see what my battery recommends in the documentation.

Edit: I’ve not had a day myself where my 4p 100 watt panels did not deliver enough in cloudy conditions to power my MPPT controller. I’ve been out on completely overcast days, not dark raining days so never knew it could be an issue.
 

Hedges

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For the wiring of the solar panels, right now it is rated for the specs above, 6 amps etc. (I believe its 16 or 18 AWG or whatever the minimum requirement would be out of the box). if I go partial series, 2P2S, would any of the wiring exceed their ratings? If so, it might require me some effort for me to replace the wires in panels, which is not easy, but not impossible.

The wiring which comes with the panels is fine.

If you parallel two or more panels (or series strings of panels), the wire used after the junction should be rated for ampacity at least 1.56x Isc x n, where "n" is the number in parallel. In the case of two parallel strings of 6A Isc each, that is 1.56 x 6 x 2 = 19A, so 12 awg rated for 19A is good. (Ampacity rating of 12 awg is higher, but at least for house wiring NEC imposes a 20A limit.)

With just two strings of panels in parallel, no matter where a short occurs, no wire will carry excessive current.
With three or more in parallel, if a short develops in one, the other two or more will dump current back into it. In that case, each series string of panels should have a fuse at least 1.56x Isc and no more than the "maximum fuse" rating given on panel label.

You can find MC4 "Y" cables with some pretty heavy gauge wire, but likely can't trust the connectors for more than 30A. Mix & match of connectors is even more likely to have trouble. Either cutting of the MC connector on output or using a combiner box would be a better way to go at higher current. Two, 2-"Y" connectors with MC extensions spliced together in a box would work for four strings. Four MC-4 fuse holders before the "Y" would protect PV string wiring.
 

SolarShed

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So I wanted to give an update today on this project, I was hoping to post pictures of the panels mounted and wired up as we discussed.

But unfortunately that's not the case. I received my two extra panels, which was a gift from my dad, however both panels came smashed. Thankfully we had the hindsight to buy insurance for the value of the two panels, so now I will be experiencing how well FedEx's coverage department works. Regardless if FedEx pays the full amount that I got insurance for on these panels, it's still a loss to me.

I don't think I can find the exact same panels that I already have.

So my next question is if I can get two panels from another manufacturer with slightly different specs, are there some rules against mixing and matching panels that are both in series and parallel connected? Or will this not really forced me to be fully parallel with 2 pairs of different panels?
 

MisterSandals

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So my next question is if I can get two panels from another manufacturer with slightly different specs, are there some rules against mixing and matching panels that are both in series and parallel connected? Or will this not really forced me to be fully parallel with 2 pairs of different panels?
I cannot discern what your final panel configuration was going to be. 2S2P?

Regardless, I think the little 100W panels are all quite similar in their specs will likely work just fine.
If you want to have the numbers run with 2 different sets of panels and how you intend to wire them, its pretty quick.
 

SolarShed

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I cannot discern what your final panel configuration was going to be. 2S2P?

Regardless, I think the little 100W panels are all quite similar in their specs will likely work just fine.
If you want to have the numbers run with 2 different sets of panels and how you intend to wire them, its pretty quick.
Both 2S2P and 4P.

2S2P I was going to do first and see how it goes, but 4P would have been my second try for shading concerns. Here's a picture of my shed and you'll see one panel and then the other panels on the other side of the roof, I was going to put the two extra panels in the same locations one in the front one in the back. In the morning I get my house blocking early sun, and dusk I get my neighbors trees. Panels face east west.
 

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chrisski

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In my signature block there’s some math to take into account. Called ‘Mixing and Matching Panels.”

Probably will be fine, maybe a 5% to 10% loss versus having all the same panels, but that is still better than 50% of the power. I did some calculations for a closely matched set and came out to between 2% to 4%.
 

Hedges

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Panels in series should be same (or very close) Imp. Expect to get the lowest Imp of all panels in series.

In parallel, panels (or strings of panels in the case of 2s2p) should be similar Vmp. Not quite as important as current for panels in parallel, because the watts/volts curve is pretty flat on top.

Looks like your West facing roof will start to block that East facing panel around 1:00 PM or so. If you populate the East face with panels, closer to the eave would delay that shadowing.

On the West roof along South edge and tilted South would be good. Or on the fence.
 

SolarShed

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Hi, I'm currently working with FedEx on getting paid out for my loss, hopefully they pull through. Looking at the box (the original, unopened manufactures box), it was dropped on one corner and that's what ultimately destroyed the panels.

I've been searching as for replacement panels

This is what I have now, two NOMA 100 W panels:
Vmp = 18V
Imp = 5.5A
Voc = 21.85V
Short Circuit = 6.03A


The new NOMA 100W panels are now:

Vmp = 18V
Imp = 5.5A
Voc = 23.0V
Short Circuit = 5.8A


I could look for other panels (not NOMA) to better match the values, but I'd be curious to know what losses I might see if I have the 2 old panels mixed with these 2 new panels, for both 2S2P and 4P wiring scenarios. For the 2S2P, would it make sense to wire the new panels as 2S or 2P?

Thanks again!
 
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SolarShed

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Hi again, help me make a decisiion. Things with FedEx are taking forever, so I just might by the panels before I get things settled with FedEx and hope they pay me out for the insurance I bought.

I'm on the fence about these panels now.

I could buy those NOMA panels that I list above, but right now they are at a premium of $549 CAD, each would be be $1100 CAD, which is insane and I think they are polycrystalline. They go on special from time to time, and the price drops to $199 each. Here are the specs of the new NOMA 100W panels again:

Panel A
Vmp = 18V
Imp = 5.5A
Voc = 23.0V
Short Circuit = 5.8A


This is what I have now, two NOMA 100 W panels:

Panel B
Vmp = 18V
Imp = 5.5A
Voc = 21.85V
Short Circuit = 6.03A


However, I'm also eyeing these Renogy Monocrystalline Solar Panel panels:

Panel C
Vmp = 18.6 V
Imp = 5.38A
Voc = 22.3 V
Short Circuit = 5.86A


Not exactly the same, but much cheaper at $220 for both panels.

So, whether I do 2S2P or 4p, first I want to ask if it will be safe to mix he 2 pairs of solar panels (panels B and C), and it seems I'll be getting hit with a bit on efficiency, but less than 5% from my calculations (for either 2S2P or 4P)? But wanted to confirm

Cheers
 

MisterSandals

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Current setup 2S:
36V 5.5A

Renogy 2S:
37.2V 5.38A

Combined 2S2P:
36V 10.88A
36V x 10.88A = 391W

I am guessing you would never know the difference between that and 4 the same. It might be difficult even with a meter, except under controlled conditions.
 

SolarShed

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Ok, I'm all over the place here, but one thing is for certain, you guys are pretty awesome with all your knowledge and experience. I want to ask about 1 more scenario here before I make a decision. FedEd really put me in a pickle by destroying the panels...or perhaps I'm over thinking this. Of course, I can always rip out my current panels, and just replace them, but that would be more waste and only if I have to. All I want is more watts on my system, to be at least 400w instead of the 200 watts now.

As you know, I've be mulling over getting 2x 100 watt panels to put on my shed that has an existing 2x100watt panels in parallel (2P). Here is my shed again below:

_20210823_164427.JPG


The 100w panel facing you, is facing east, and gets the morning sun (that's the important sun, as you know). The other panel faces west and is on the other side (not shown in picture).

Now, what if I get, rather than 2 x 100 watt panels, what if I get 1 x 200 watt panel and install on the roof facing east. That way, this will maximize my morning sun intake. Here are the specs of the 200 W panel that I'm thinking of getting:

Renogy 200 W
Vmp = 22.6V
Imp = 8.85A
Voc = 27 V
Short Circuit = 9.66 A


This is what I have now, two of these below (for easy comparison):

Noma 100W panels (x2)
Vmp = 18V
Imp = 5.5A
Voc = 21.85V
Short Circuit = 6.03A


Would getting the one, 200W panel make sense to add to my existing system?

Which scenario now is best, all parallel, all series or mixture of series-parallel?

Thanks again for your input.
 

Hedges

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As a rough estimate, when paralleling panels (or strings), assume Vmp of the lowest panel (string) multiplied by Imp of each panel (string).

When connecting panels in series, assume lowest Imp of any panel, and voltage the sum of Vmp of all the panels.

Your parallel 200W || 100W || 100W should deliver at least 18V x (8.85A + 5.5A + 5.5A)
Output of the 200W panel will be reduced to 18/22.6 or 80%, so 160W (STC)

If panels are of different orientation, they shouldn't be connected in series, only parallel.
Their peak currents (and wattage) won't appear at the same time, but total Wh during the day will be similar so go by the math above to estimate yield.
 

SolarShed

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this makes sense. My losses are greater with the 200 watt panel, based on your math and the math by MisterSandals from a previous post.

It seems the best scenario would be to get the 2x100 panels and put them on the east side, so I'll have 3 on one roof for morning sun, and the other one the west side will be "top-up sun".

Having said that, I don't think I can series connect 3 panels? I mean if I do 3S1P, is there some issues with mixing odd number of panels?
 

Hedges

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No issue with odd number in series.
9 panels could be 9s, or 3s3p or 9p
7 panels could only be 7s or 7p

The issue with series is max Voc, adjusted for coldest weather. Does that exceed maximum input of your SCC?
 

SolarShed

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Hi all, wanted to provide an update on this. Long-story short, FedEx is cutting me a cheque for the my declared value plus the cost of shipping. Success in that regard, good on FedEx to pulling through without any issues.

I've been looking for the same panels at stores, but they can't be found anymore, however, I did search the used-markek and have had success. Found a 1 year old, lightly used panel of the exact same mode and specs. So far, I've been able to purchase this one panel and install it on my shed as shown here:

DSC_0399.JPG

Right now, I have 3, 100W NOMA panels of exact same specs, with 2 orientations: two panels are facing east (shown in photo) and one facing west (not shown, on the other roof), all have these specs:

Vmp = 18V
Imp = 5.5A
Voc = 21.85V
Short Circuit = 6.03A


I found a 4th one, and I will be picking it up on Oct 1. It is the exact same panel with the same specs!

My original plan was to install the 4th panel on the west facing roof, but, my neighbors trees are an issue. So now, I plan on installing the 4th panel beside the two I already have, on the east roof, as shown here:

DSC_0399.JPG

I think it makes sense to install the 4th panel on this roof because the important morning suns comes here first, so I'll install here.

This is how my current set up of 3 x 100 watt panels works; at the the moment, its 3P because its just easier for me to do that (I don't have connectors for series, yet).

But, with the 3P set up, in the morning when the sun comes up, my home is blocking the sun until about 9:30 am, before the sun hits any of the panels, the amps going into the battery slowly increase from 0 to about 0.9 amps (basically, this is "shade sun"). The sun slowly approaches from the LEFT and moves to the RIGHT. Once the sun starts to hit Panel 1, the amps going into battery increase to about 1.5, then, as soon as the first panel is completely in the sun, the amps increase to about 4.5 amps! Even the slightest shade on the panel, and it doesn't produce all the power, but the moment the shade is gone, its just jumps to 4.5 amps. As the sun approaches panel 2, the amps increase accordingly, and as the sun completely hits the panel #2, the amps increase to 9.5 amps! I suspect with a 3rd panel on that same roof, it will do the same, and increase to about 14 amps in when the sun is fully on the 3 panels.

With this September sun, it takes maybe about 30 minutes for the sun to completely clear my home, and hit panels. In the really poor sunny months (winter), December and January, I suspect that will be a lot worse.

There is clearly a shading issue with my home blocking the sun even on my best roof.

So, a second option could be is to series these three panels, 3S and parallel the other panel in the back to make the 3S1P. But, with the shading issues of my home, will it have to clear my home first, before I get all the power (1/3 the amps)?

All the amps reported above, are battery amps (according the BMS), not PV amps.
 
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chrisski

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I have a 4P system and have a circuit breaker for each panel. I’m able to get some data on each panel that helps me plan. For example, most could days, I still get 1 amp off a panel on an overcast day. Data like that helped me size up my PV array based pff cloudy days.

If you have bad luck charging in the winter, that fence looks like it could have some good additional output, but before hanging panels up, you can get some data about a shaded panel to see if its worth it. Of course putting the panel high up is a better option, but if that space is not available, not other choice.

I’m not so convinced about panels having to be the exact same manufacturer and model as I used to be. Fairly close is good. Your panel specs seem to be pretty close for a lot of 100 watt panels. So if you get more in the future, they could come from second hand 100 watt panels of a fairly close output. There’s a link in my signature block that has some math for figuring parallel panel output.
 

SolarShed

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Finally, the project is complete. I was able to find an new, unused 4th panel to complete the operation. All my panels are now exactly the same:

Vmp = 18V
Imp = 5.5A
Voc = 21.85V
Short Circuit = 6.03A


I made a short video about this project for some community competition with Renogy.....i'll share it here


@chrisski You're right about that. I could have got any other 100W panel and it would be ok. That would have been my Option B had I not got easy access to some of my original panels. I'm experiencing the same as you, I can pull just over 1 amp on cloudy days between the 4 panels when connected in 4P.

@MisterSandals Yesterday, I changed my battery-CC fuse to an ANL type fuse, thanks for your suggestion about getting rid of the speaker-wire fuse. I don't know if ANL fuses are better, but its seem to be the one recommend by most, for a 12V system. Its ignition proof.

DSC_0371.jpg

Back to back to the original question as how to connect my panel, series/parallel etc.

Right now, its all parallel 4P....and the reason why i'd like to keep it like is two fold. I do have a shading issue. My house blocks the morning sun hitting the east roof, that has the 3 panels. The sun moves from panel 1 (leftmost) and then eventually sweeps across to panel 3. By that time, its almost 11 am and im not even in the dead of winter yet. Having them in series, I suspect I won't get any charging untill it clears all the panel.

Having them in parallel, as is, this is what I experience

no sun - 1 amp
sun on first panel - 5 amps
sun on second panel -9 amps
sun on third panel - 13 amps

The above happens over the course of 45 minute or so, and will likely become longer in dec/jan.

I'm ignoring the amps that the west facing panel does, I'm sure it contributes to something, but I can't calculate it just yet (getting a clamp meter today)

Today, in fact, was great test for my self-heating battery. It got cold enough the self-heating future activated. The BMS prioritized the available solar power to the self-heater rather the battery cells to warm it up. Having that first panel lit up in the sun, it greatly increased the time I have for sun because it is mostly used for heating the battery up while the sun moves across the sky/panels.

I spoke of the self-heating battery experience in detail here, on this post:


I must say, I'm very impressed with how the self-heating function of my battery works.

If I change my panels to series parallel-mixture, would I not loose some amps until they are all in the sun?
 
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