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diy solar

How do I connect 5 solar panels?

Santa said:
RE; Suitcase panel: I would LOVE to directly answer your question of "does it" (suitcase panel) have an SCC built-in, or is it just the panels" Originally, about 2012, I bought an "all-in-one" along with this suitcase panel. The battery/all-in-one was since stolen. I still have the suitcase panel. This was my introduction into solar/backup power. I don't know or understand what they used as a charge controller. I tried to ask them (Lion) abouty it, but never got an answer. Is there something on the back of the panel that can answer this? I hope that made sense.
Click to expand...
Hmmmmm interesting... well I will make a logical guess that the SCC was in the "battery/all in one" unit, because since the cabling between the SCC and the battery needs to be heavier-gauge to handle the higher amps at lower voltage, it always makes sense to mount the SCC as close to the battery as possible. So you're probably fine.
An easy(ish) way to test this would be to pull out the suitcase in the sun and use a voltmeter at the cable leads... if you read between 12 and 14vDC, the SCC is in the suitcase. If you read 16-22 or so, the suitcase is just panels and the SCC was in the all-in-one unit that's now gone.
 
Santa said:
Yes. There is a limit of 30 amps on this SCC.
Click to expand...
Wow, with the panels in parallel as we've been discussing, 29amps is right up there! It would run hot if your 5 panels produced that much power.

What are the maximum input volts of this SCC?

I ask this because if you were to hook up your panels in series, or even a combination of series and parallel, then your amps become very manageable (and wire sizes very reasonable).

Santa don't be discouraged, you are in excellent hands, especially with the minds that have joined in today! I know I've learned a LOT!
 
JeepHammer said:
With all due respect,
That's not correct.
Click to expand...
With likewise due respect @JeepHammer , given that solar panel manufacturers themselves state that, indeed, you must individually fuse more than 2 parallel-connected panels, I suggest that your understanding of how a failed panel acts is incorrect. A failed panel (depending on how it failed, obviously) can indeed act as a load, thus the importance of individual fusing of parallel panels... which is further backed up by the layout of every reputable commercially-available combiner box in existence.

Windy Nation, for instance, says here:

"Commercially made solar panels over 50 watts have 10 gauge wires capable of handling up to 30 amps of current flow. If you connect these panels in series, there will be no increase in current flow so fusing is not required for this string. This is not the case when you have panels connected in parallel, as when connected in parallel the system current is additive. For instance if you have 4 panels each capable of up to 15 amps, then a short in one panel can draw all 60 amps towards that short-circuited panel. This will cause the wires leading to that panel to far exceed 30 amps causing that wire-pair to potentially catch fire. In the case of panels in parallel, a 30-amp fuse is required for each panel. If your panels are smaller than 50 watts, and use only 12 gauge wires, and 20 amp fuses are required."

Eaton (as in, Eaton Cooper Bussman) says here:

"Depending on the desired PV system capacity, there may be several PV strings connected in parallel to achieve higher amperage and subsequently more power. Systems that have less than three PV strings will not generate enough fault current (short-circuit) to damage the PV modules, conductors or downstream equipment, and do not present a safety hazard, provided the conductor is correctly sized based on local codes and installation requirements. When three or more PV strings are connected in parallel, a PV fuse on each PV string will protect the PV modules and conductors from overcurrent faults and help minimize any safety hazards.The PV fuse will also isolate the faulted PV string so the balance of the PV system can continue to generate electricity. "

BRE says here:

"In a PV array formed from a number of strings, fault conditions can give rise to fault currents flowing though the d.c. system. Two key problems need addressing – overloaded string cables and significant module reverse currents, both of which can present a considerable fire risk. Fault analysis shows that the maximum fault current flowing in a string cable to be (N -1) x Isc. A system of three or fewer strings cannot generate sufficient fault currents to present hazardous module reverse currents. Hence with three or fewer strings, fuses can be omitted providing that string cables are suitably rated. Such a method does not clear the fault, but simply prevents a fire risk from overloaded cables. The installation of string fuses can provide protection against fault currents in all other cases. While some fault combinations are less likely than others, in order to provide full protection of all cables and modules – string fuses are required in both the positive and negative legs of the string cabling. (See section 2.1.5)."

I can provide more references if necessary, or you can search for yourself, but I think the point is clear - a complete understanding of how these systems work leads one to the inescapable conclusion that a faulted panel can indeed cause a fire, and it's well worth the small investment of an inline fuse to protect against that. I've personally seen a failed panel burn a hole in itself (and can provide a photo of that if it would be helpful), so I cannot possibly overstate how very important it is to follow safety protocol when working with PV arrays.
 
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So, jumping from back feeding and diodes to fusing?
Which is why I started with component FUNCTION in the first place...

As described, and shown in the image, and laid out in text...
A properly functioning panel, simply shaded, will NOT become a 'Load'.
A seriously DAMAGED panel *Could* become a Load in PARALLEL where it has access to full, combined AMPERAGE.

I have seen damaged panels scorch, carbon up, cook,
Never, not once seen one catch fire and burn, not even when struck by lightening...
I'm not aware of anything flammable in better quality (I think you called them "Reputable Manufacturers".

Diode losses at the panel,
A diode stops ANY back feeding, period...
Any panel damage CAN NOT be 'BACK FED' no matter how much amperage is in the combined line.
The circuit is one way, period.

And again, I'll point out when the diode is properly sized for the panel (Max Amp Rating) ANY over amp attempt at 'Back Feeding' from combined main lines, and the diode pops, opening the circuit just like a fuse.
While I have no objections at all to adding fuses to panels at all, a fuse isn't a one way blocking in diode...
And that brings us back around to CHECK/TEST/VERIFY EVERYTHING...

3, 5, 6, 8, 10, etc amp diodes are common, it's just too easy to size the diode to the panel,
A good time to fuse the panel also if you feel it's needed.
And I'll point out the diode,
First bocks ANY back feeding,
Second, sized correctly blows out BEFORE the wiring can melt/catch fire,
The blow out works just like fuse, opening the circuit.

In my opinion, since you are there anyway, adding a 5¢ fuse is pretty cheap insurance,
But I'm not driven to demand anyone to do this any specific way...

In Parallel, a diode at each panel drops line voltage a total of 1/2 to 1 volt TOTAL,
Acceptable losses...

-------

Series wiring, ONE diode per SERIES.
Where the SERIES hits the combiner, a diode, each diode drops total voltage 1/2 to 1 volt, acceptable losses.

One diode per panel will drop voltage AT EACH PANEL about 1/2 to 1 volt PER PANEL.
That's 1/2 to 1 volt PER PANEL,unacceptable losses for me, but folks can do what they want.

The same with One Fuse per Series string, since either the diode or fuse will open the circuit ENTIRELY,
Making any 'Potential' energy the string can produce to ZERO,
Open circuit means no danger.

There is MUCH LESS Amperage in a Series string, and amperage is what heats cables and starts fires.

-----------

Now, I've been doing this a LONG TIME, and I understand it fully...
I separate Series & Parallel and build for each, there is no 'Universal' way to do the wiring, just like components need to be sized specifically for the string/panel being used...

While common diodes, and fuses come in all different sizes, and are cheap,
The panel manufacturers have no idea in the world what *YOU* are going to do...

A common phenolic diode looks like this, and it's quite small.
As you can see they come in a number of Amperage limits so they can be sized specifically to the application.
At 6¢ to 35¢ each, no one has an excuse NOT to size diodes to the panels/application being used.


Hot-sale-100Pcs-Set-8-Values-Diode-Bag-Assortment-Kit-Set-1N4148-FR107-1N5408-For-Arduino.jpg


Now, when I'm wiring panels, I do something a little different,
I use a diode that fits in a fuse block.
When you do this about 25 years you learn that a fuse block makes a good combiner box,
With easy find, quick change components...
It also allows you to change configuration, expand in minutes WITHOUT being proprietary, not a slave to changing everything every time you want to make a change, add panels.
Lower cost than proprietary, and you aren't a slave to some company that charges 6 times the price for half the capability...

A quick change diode, runs about $1.50 each in bulk...

1Amp-Mini-Fuse-Diode-46880_f.png


A quick change fuse,

JFBL-Hot-sale-35-Piece-MIXED-Mini-Blade-Fuse-AUTO-Car-Motorbike-5-7-5-10.jpg


A quick change fuse block, from small and indoor, even single string/single panel...

Free-shipping-10PCS-LOT-new-small-waterproof-fuse-box-high-quality-automotive-fuse-socket.jpg


hla-h84960091_w_ml.jpg


To big enough for any strings I know about, and waterproof...
With or without LED indicator that tell you what fuse/diode failed.

6db6328d2b6a76204339567559709f02.jpg


From under $5 topping out about $35, pretty affordable for your panel string combiners/panel protection.

-----------

Do things how ever you want to,
Dismiss ideas and take them off the table,
It doesn't make those ideas any less valid or workable.
 
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JeepHammer said:
So, jumping from back feeding and diodes to fusing?
Which is why I started with component FUNCTION in the first place...
Click to expand...
...um... wasn't jumping from anything... your long response above started with a comment from another user about fusing.
And all the above is great. My point is, you said "The panels in a COMBINED parallel string CAN NOT back feed each other, it's impossible. " which is not true at all and in fact very dangerous to believe, so I hope you'll reconsider your wording and stances without feeling the need to write another book.
If not, eh. More power to you, I suppose.
 
Justin Laureltec said:
...um... wasn't jumping from anything... your long response above started with a comment from another user about fusing.
And all the above is great. My point is, you said "The panels in a COMBINED parallel string CAN NOT back feed each other, it's impossible. " which is not true at all and in fact very dangerous to believe, so I hope you'll reconsider your wording and stances without feeling the need to write another book.
If not, eh. More power to you, I suppose.
Click to expand...

Again, no disrespect, but 'Writing A Book' is how you convey the complete picture.
An 'Idea' can come through in a short video,
An education comes from text books, detailed writing and defining the issues, which isn't a 'Short' subject...

The OP asked a question about Series/Parallel,
Not a 'What If, Worst Case, 15 things go wrong at once scenario" to confuse her basic question, and asked me to have a look...

Now that the issue is further confused I'll now make a diagram explaining the difference in diode, fuse use.
That shouldn't take up more than about 3 MORE hours...
 
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Oh come on. Please allow others to give their opinions and info without criticism. How are we going to learn otherwise?
 
Santa said:
Oh come on. Please allow others to give their opinions and info without criticism. How are we going to learn otherwise?
Click to expand...
I concur, really, I just feel that matters of safety should not be taken lightly, and all safety mandates state that three or more parallel panels or strings of panels must be individually fused.
There are ways around this, that's a fact... My opinion is that it's simpler and safer to just do it rather than engineering a way around it.
 
Justin Laureltec said:
I concur, really, I just feel that matters of safety should not be taken lightly, and all safety mandates state that three or more parallel panels or strings of panels must be individually fused.
There are ways around this, that's a fact... My opinion is that it's simpler and safer to just do it rather than engineering a way around it.
Click to expand...
Safety is #1 priority for me. But if this is true, why is @Will Prowse not doing it? (I would like him to please address this when he gets time...) Do you know if Will did a video on this?
 
Santa said:
Safety is #1 priority for me. But if this is true, why is @Will Prowse not doing it? (I would like him to please address this when he gets time...) Do you know if Will did a video on this?
Click to expand...
Can someone summarize this thread? I have no idea what's going on here, and I am busy filming all night. What's the confusion?
 
Will Prowse said:
Can someone summarize this thread? I have no idea what's going on here, and I am busy filming all night. What's the confusion?
Click to expand...
It can wait Will. I was going to add a 5th panel to your blueprint. Someone here thinks we need to individually fuse 3 panels to be safe I believe?
 
Justin Laureltec said:
With likewise due respect @JeepHammer , given that solar panel manufacturers themselves state that, indeed, you must individually fuse more than 2 parallel-connected panels, I suggest that your understanding of how a failed panel acts is incorrect. A failed panel (depending on how it failed, obviously) can indeed act as a load, thus the importance of individual fusing of parallel panels... which is further backed up by the layout of every reputable commercially-available combiner box in existence.

Windy Nation, for instance, says here:

"Commercially made solar panels over 50 watts have 10 gauge wires capable of handling up to 30 amps of current flow. If you connect these panels in series, there will be no increase in current flow so fusing is not required for this string. This is not the case when you have panels connected in parallel, as when connected in parallel the system current is additive. For instance if you have 4 panels each capable of up to 15 amps, then a short in one panel can draw all 60 amps towards that short-circuited panel. This will cause the wires leading to that panel to far exceed 30 amps causing that wire-pair to potentially catch fire. In the case of panels in parallel, a 30-amp fuse is required for each panel. If your panels are smaller than 50 watts, and use only 12 gauge wires, and 20 amp fuses are required."

Eaton (as in, Eaton Cooper Bussman) says here:

"Depending on the desired PV system capacity, there may be several PV strings connected in parallel to achieve higher amperage and subsequently more power. Systems that have less than three PV strings will not generate enough fault current (short-circuit) to damage the PV modules, conductors or downstream equipment, and do not present a safety hazard, provided the conductor is correctly sized based on local codes and installation requirements. When three or more PV strings are connected in parallel, a PV fuse on each PV string will protect the PV modules and conductors from overcurrent faults and help minimize any safety hazards.The PV fuse will also isolate the faulted PV string so the balance of the PV system can continue to generate electricity. "

BRE says here:

"In a PV array formed from a number of strings, fault conditions can give rise to fault currents flowing though the d.c. system. Two key problems need addressing – overloaded string cables and significant module reverse currents, both of which can present a considerable fire risk. Fault analysis shows that the maximum fault current flowing in a string cable to be (N -1) x Isc. A system of three or fewer strings cannot generate sufficient fault currents to present hazardous module reverse currents. Hence with three or fewer strings, fuses can be omitted providing that string cables are suitably rated. Such a method does not clear the fault, but simply prevents a fire risk from overloaded cables. The installation of string fuses can provide protection against fault currents in all other cases. While some fault combinations are less likely than others, in order to provide full protection of all cables and modules – string fuses are required in both the positive and negative legs of the string cabling. (See section 2.1.5)."

I can provide more references if necessary, or you can search for yourself, but I think the point is clear - a complete understanding of how these systems work leads one to the inescapable conclusion that a faulted panel can indeed cause a fire, and it's well worth the small investment of an inline fuse to protect against that. I've personally seen a failed panel burn a hole in itself (and can provide a photo of that if it would be helpful), so I cannot possibly overstate how very important it is to follow safety protocol when working with PV arrays.
Click to expand...

This is an awesome post. Great information here. Yeah, you can fuse each one if you want. I hate putting anything into parallel without fuses. Just put some inline fuses on your panels. I will add it to the website:
cescdce.jpg
 
I hate to rain on this technology discussion, its all worthy of at least a new thread and maybe even a sticky.

But, please see post #52. I think 5 panels parallel produces too many amps to safely run Santa's SCC.
 
MisterSandals said:
I hate to rain on this technology discussion, its all worthy of at least a new thread and maybe even a sticky.

But, please see post #52. I think 5 panels parallel produces too many amps to safely run Santa's SCC.
Click to expand...
Yeah good point! Why wasnt that mentioned before. That doesnt seem smart at all.

And I am totally behind here. I did not read the entire conversation. Please excuse my ignorance. I am just trying to jump in here because I was tagged. Sorry
 
So two string systems do not need OCPD. Which is nice, because my other package systems have 1 or 2 string systems only. I remember designing it for this reason about two years ago. I wanted the voltage to be low, but I did not want to parallel a ton of panels. (I do not trust beginners with 80+ volt open circuit. That scares me to no end). But fusing not necessary. Most are running single series string arrays for all in one/ tiny systems, so that's fine.

But having 3+ strings in parallel, needs fusing. Great point about the new 400w system blueprint. So I added inline fuses to that package. None of the other packages need it, so should be good to go.

But great idea for a future video idea. Very straight forward lesson. If someone is designing a giant system with higher voltages/current ratings, I imagine they would size their pv ocpd accordingly. I am building a grid tie system right now and I have single strings on each input, so no ocpd required. Anywho, I personally hate the idea of parallel connecting multiple panels in general. Horrible idea. One time I found a bad connection on a parallel pv array and it created a ton of heat! Very scary. Also, flex panels love to catch on fire. There are a few in the reviews. Could be for this very reason, but I am unsure.
 
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Santa said:
Is it not just one string in parallel here? https://www.mobile-solarpower.com/simplified-400-watt-fewer-wires-and-alternator-charging.html I am still learning and didn't see what the definition of a string is. I don't need to add the 5th panel.
Click to expand...
Ohh in that blueprint you have 4 solar panels in parallel, so that is 4x parallel strings. Does that make more sense? If you had 4 panels in series, it would be a series string. You want to fuse each individual panel if you have more than 3 parallel strings.

And this blueprint implies that branch adapter/wire can safely carry the current. I checked current of branch adapter, and it can handle it. The problem is when a cell shorts on a panel, the other panels will see it as a resistive load, and cause heat development on a panel.

I think I am going to make a picture guide to make this easier. I am working today and tomorrow on videos, but maybe in the next few days. I will be working during Christmas as well.
 
Wouldn't 2 panels in series (twice) and joined in parallel be easier? Takes a pair of 1 to 2 adapters.
Drops combined amps to 11 and (raises) volts to 36.

I think an SCC running at 35% is better than one running at 70% too.
 
MisterSandals said:
Wouldn't 2 panels in series (twice) and joined in parallel be easier? Takes a single 1 to 2 adapter.
Drops combined amps to 11 and (raises) volts to 36.

I think an SCC running at 35% is better than one running at 70% too.
Click to expand...
Will said I HAVE TO DO PARALLEL for this controller.
 
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