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Old 05-25-2023, 08:21 PM   #1
Mini-Skoolie
 
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Long distance power loss question.

So which would be preferable?

The guy I bought all my solar stuff supplied a 50' cable to go from the panel array to the 3in1 controller at the bus. The problem is the tall trees blocking the sun at various times of the day. I doubt I will get more than 3-4 hours of strong sunlight in a day without cutting down a few trees. However, up higher on our land is a clearing that would be a perfect place for a "solar farm" but it's 300-400' feet from the bus. As a side note, we found a spring up there today so maybe that will pan out as a better gravity fed option than we currently have. I digress.

If you had a $500-$1000 budget would it be better spent cutting down trees or buying wire to cross the distance? I'm assuming having it already converted to AC would be better for that distance.

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Old 05-25-2023, 08:50 PM   #2
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Even if I had to dig the stumps out by hand, I know what I'd do. I chose to remove the trees. That's my advise.
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Old 05-25-2023, 11:09 PM   #3
Mini-Skoolie
 
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Voltage drop might be reasonable

Quote:
Originally Posted by KenandDeb View Post
So which would be preferable?
If you had a $500-$1000 budget would it be better spent cutting down trees or buying wire to cross the distance? I'm assuming having it already converted to AC would be better for that distance.
Last week I literally, jokingly asked my wife: "is it OK to cut down trees to get better sun on your solar panels?" I guess I can see both sides, but cool to keep trees around if you can.

Voltage drop is based on current (lower the better) wire gauge (bigger the better but also more expensive) and distance (shorter is better). So for example, lets assume 400' is the fixed distance and all panels are in series so made up current is 15A and voltage is 150V for the string (curious what your actual panel set is like).
10 AWG wire causes a 11.7 volt drop which is ~8% drop from the 150V.
8 AWG wire = 7.3V (5%)
Doubling the amps would double the voltage drop.

Bulk TEMco 10AWG Solar wire is ~$0.45/ft so ~$360 for 800 ft round trip
8 AWG = ~$0.75/ft = ~$600
Not sure what your panels and SCC specifics are but this looks possible on a first approximation.

I don't think converting to AC helps the power loss specifically, and I have seen some arguments that DC is more efficient at the same voltages - others here will know more about this.
But higher voltage and (more importantly but related) lower amps, keep voltage drop lower. This may be limited by your panels and what your SCC can accept for max voltage.
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Old 05-27-2023, 06:51 AM   #4
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I have 8 JA Solar 380 panels.


https://www.solarreviews.com/manufac...rjam72s09380pr
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Old 05-29-2023, 06:12 PM   #5
Mini-Skoolie
 
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What is the input voltage limit and the max output current of your SCC?
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Old 05-29-2023, 07:11 PM   #6
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EG4

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Max MPPT Operating Voltage:500V
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Old 05-29-2023, 07:16 PM   #7
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Btw, we measured today and the distance is only 260'
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Old 05-29-2023, 10:36 PM   #8
Mini-Skoolie
 
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Quote:
Originally Posted by KenandDeb View Post
Btw, we measured today and the distance is only 260'
Well to the best of my calculations, If all panels are in series Voc goes to 390V (8 x 48.75) and Imp is 9.6 so you could expect just a ~5V (1.25%) drop using 10 AWG wire (520 ft seems doable for <$300 in wire).

Not sure how cold it might get where you are (colder panels increase the voltage) and adding a typical headroom of 25% gets 390V to 488V which is getting close to 500V max which can damage the SCC if crossed. So, another option would be 2 parallel strings of 4 series panels each, which puts volts to 195 and amps to 19.2 resulting in a voltage drop of ~9.7V = 5% which also seems totally fine. (6V and 3% drop using 8 AWG wire).

Disclaimer: I am working from theory and have not actually built such a system. Lots of smart folks here, but maybe not as much experience with long runs. The DIY Solar Power forum has a bunch of people powering cabins in the woods and may be able to confirm these ideas.

You can play with your own voltage drop estimates on this wire calculator - their numbers are quite close to mine but not exactly the same.

Good luck, let us know what you end up doing!
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Old 05-30-2023, 06:09 AM   #9
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Thanks for the info.
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