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Greetings and new system design Qs

100ranch

100ranch

New Member
Joined
Feb 18, 2024
Messages
17
Location
Georgia and Indonesia
Hello, Im in the Appalachian mountains and also Indonesia. I just bought a pickup load of Suntech 280S-24/VD. (some specs attached; full data sheet link in attachment). These were sold as 280 watt panels, approximately 45v and 8 amps. I am designing 24v system with 6 panels, Victron 150/70 and 4 deep cycle 12 v 100ah. Victron calculator indicates 130/72 in 2p3s.

Ive lost three drafts in this compiler, already, so Ill keep it short and sweet. Are my batteries underpowered. Energy audit secondary because I have a large farm and can likely use all). Will this work reasonably efficiently?

Anything else strike you? Im outta here before I delete another draft.

Cheers

Screenshot_2024-02-19-15-38-07-428.jpg
 
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100ranch said:
Hello, Im in the Appalachian mountains and also Indonesia. I just bought a pickup load of Suntech 280S-24/VD. (some specs attached). These were sold as 280 watt panels, approximately 45v and 8 amps. I am designing 24v system with 6 panels, Victron 150/70 and 4 deep cycle 12 v 100ah. Victron calculator indicates 130/72 in 2p3s.

Ive lost three drafts in this compiler already, so Ill keep it short and sweet. Are my batteries underpowered. Energy audit secondary because I have a large farm and can likely use all). Will this work reasonably efficiently?

Anything else strike you? Distributor, shunt, junction box? Im outta here before I delete another draft.

Cheers

View attachment 196814
Click to expand...
ps. Shunt, distributor, and/or junction box? Victron calc says 72a, and Im buying 70a model. However, Im assuming I will never reach max output with these older panels and suboptimal location, laying flat on container car. Maybe costly assumption?
 
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MisterSandals said:
With a Voc of 44.8V there is not a lot of room for temp compensated voltage if planning on 3S2P.

280W x 6 panels / 28V charging = 60A

it really suggests 2P3S? (Seems odd, shading?)

What temp did you use for coldest?
Click to expand...
I was confused. There is a temp range in the data sheet. I used that. If those numbers refer to my location then once in ten years it may drop below zero F, summer can exceed 100, not often. There's a link in my attachment. When i realized the calculator readings were changing on input (duh), I fiddled with serial-parallel settings until i was below 150 and at 70 in calc results. So 3s2p was what I input to fall within 150/70. Missed later by 2. However, some call these 30 or 35 volt panels. I do not completely understand data sheet but this is noted there. Also 204 watts on one criterion not 280. However they are old and likely wont get optimal sun, although at first it is likely I'll try to achieve that. Later likely to lay flat on top of container in a bright area.
 
Using 0F (-18C) which is 48 dec C below rated.
Guessing your panel temp coefficient is .0035

3 x 44.8Voc x (48 x .0035) = 22.6 deg C rise at 0F.

Your 3S array will be 157Voc which will likely damage your SCC.
 
Thanks. Would you recommend a proper configuration? Just back from buying 12 panels. Beasts, 6 1/2 ft tall. Im a raw noob but trying to learn. Im a 70s Heathkit and Dynaco builder. Good times. Great time for pop music. Before computers took over. But I digress...
 
MisterSandals said:
Using 0F (-18C) which is 48 dec C below rated.
Guessing your panel temp coefficient is .0035

3 x 44.8Voc x (48 x .0035) = 22.6 deg C rise at 0F.

Your 3S array will be 157Voc which will likely damage your SCC.
Click to expand...
ps. Thanks for the formula. Observing repeatedly in comments on forum emphasizing that temp is fundamental to achieving one of what seem to be numerous design solutions in each person's build. I will go back and review parallel and serial wiring, and basic electricity. I blew it off over the weekend. I probably will get a more robust controller.

I want to use six of the panels initially. We have serious power requirements in developing 66 acres totally off grid. Progress though: multiple acre foodplot plantings 2x annually, new deep well and solar pump, and serious power coming compared relatibe to living off AA and D batteries, propane and hardwood. Thankfully the bulldozers quell the frustration
 
MisterSandals said:
Did you buy this already?


What is the coldest temp that you want your SCC to survive (or need to be disconnected)?
Click to expand...
Yes purchased but easily exchanged.

Lacking, I believe, an understanding of your question, I will answer by saying I normally dont sleep there below 20f. Bag only. 100 miles away, too. I'll also say that the coldest it gets is single digits, and that's very infrequent.

Question please? What do you mean by shading?
 
Brucey said:
Is it going in Appalachia or Indonesia?
Click to expand...
ps. I normally go to Indonesia after spring and fall plantings. 3 months each time. Live there 1/10th the cost of here and as a benefit it's 25k tropical islands of incredible paradise. Orangutans coming inside and using toiletries properly, stealing your cameras and quickly figuring out how to see through view finder. Sumatran tigers, rhinos, elephants, packs of begging monkeys, and other primates, a multitude of different types of birds, giant insects, and on and on. The best of tropical fruit and seafood. Sumatra smells of the sweet aroma of durian. Smells like hell, tastes like heaven.
 
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100ranch said:
I'll also say that the coldest it gets is single digits, and that's very infrequent.
Click to expand...
You get to design your system to survive or need to be unplugged for whatever temp you want. You've mentioned quite a few temps that would significantly change which SCCs will work for different panel configs.

100ranch said:
What do you mean by shading?
Click to expand...
100ranch said:
Victron calculator indicates 130/72 in 2p3s.
Click to expand...
2P3S is odd because connecting in parallel first will cause even a single panel to affect the entire array whereas 3S2P creates 2 distinct areas.
 
MisterSandals said:
You get to design your system to survive or need to be unplugged for whatever temp you want. You've mentioned quite a few temps that would significantly change which SCCs will work for different panel configs.



2P3S is odd because connecting in parallel first will cause even a single panel to affect the entire array whereas 3S2P creates 2 distinct areas.
Click to expand...
I remember reading that here but I forgot when I was trying to find settings that made the controller calculator spit out almost acceptable voltage and amp readings. As your formula shows, I had, and continue to have, little understanding of the variables meanings.

I am beginning to binge Prowse's videos. It's very helpful. Im looking at the Victron 250v 100a unit. He produced a beginner's 10 most common mistakes. Expandability is an important one for me because I only plan to use 6 of 12 panels initially. I will test them and rewire cables and MC4 Connectors. He emphasizes one should buy initially the necessary wiring, fusebox, etc for a system expansion in future in order to avoid repeatedly having to upgrade components. Sounds good this is already getting pricey, likely compared to having electric service. But not for me. They want thousands to run my lines. When I purchased the property 25 years sgo it was free.
 
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100ranch said:
Im looking at the Victron 250v 100a unit.
Click to expand...
That is a bit bigger than you need. That will accept 250V and charge at 100A.

Your proposed system:
6 panels x 280W / 28V charging = 60A

Voc = 44.6V
You can arrange your panels pretty easily to use your 150/70.
2S3P does this nicely. The easiest is probably with 3x MC4 inline fuses and a 3:1 Y cable. Or a combiner box that does the same but also adds a breaker that is a mighty nice cutoff switch. Either is a solid solution.

Pack of 5 cheaper than 3 individually:

Available in different forms:

Or combiner box (there is a lot of nice stuff in here so consider the cost of a solar cutoff switch). There are several options, i think you need 15A model as 10A model a little close to 8A panels:

 
100ranch said:
Yes purchased but easily exchanged.

Lacking, I believe, an understanding of your question, I will answer by saying I normally dont sleep there below 20f. Bag only. 100 miles away, too. I'll also say that the coldest it gets is single digits, and that's very infrequent.

Question please? What do you mean by shading?
Click to expand...
As I read more, it seems shading really does mean shading from the sun
 
MisterSandals said:
That is a bit bigger than you need. That will accept 250V and charge at 100A.

Your proposed system:
6 panels x 280W / 28V charging = 60A

Voc = 44.6V
You can arrange your panels pretty easily to use your 150/70.
2S3P does this nicely. The easiest is probably with 3x MC4 inline fuses and a 3:1 Y cable. Or a combiner box that does the same but also adds a breaker that is a mighty nice cutoff switch. Either is a solid solution.

Pack of 5 cheaper than 3 individually:

Available in different forms:

Or combiner box (there is a lot of nice stuff in here so consider the cost of a solar cutoff switch). There are several options, i think you need 15A model as 10A model a little close to 8A panels:

Click to expand...
Thank you very much!
 
MisterSandals said:
That is a bit bigger than you need. That will accept 250V and charge at 100A.

Your proposed system:
6 panels x 280W / 28V charging = 60A

Voc = 44.6V
You can arrange your panels pretty easily to use your 150/70.
2S3P does this nicely. The easiest is probably with 3x MC4 inline fuses and a 3:1 Y cable. Or a combiner box that does the same but also adds a breaker that is a mighty nice cutoff switch. Either is a solid solution.

Pack of 5 cheaper than 3 individually:

Available in different forms:

Or combiner box (there is a lot of nice stuff in here so consider the cost of a solar cutoff switch). There are several options, i think you need 15A model as 10A model a little close to 8A panels:

Click to expand...
One last question please Mister Sandals? I have 4 sealed lead acid 12v 100ah batteries. Which wiring configuration do you suggest for these assuming 2s3p 150 70 Victron, and connector box that you suggested? Thanks a million for sharing.
 
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