Solar Cable Size Confusion

Neon

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Jul 1, 2021
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I am getting mixed messages on what size solar cable I need to get for my project. Not sure if I need 10 AWG or 8 AWG. Here is what I am going to be using:
  • (2) 425 Watt panels
  • Each panel is 48.1v VOC and Imp = 10.31A
  • Going to feed a Victron MPPT 150 | 70 Tr charge controller
  • Somewhere around 20 feet of cabling
Also using a Victron Multiplus 12v 3000kVA | 120 A charger/inverter with (4) SOK 206 AH batteries.

NOTE: Not to confuse the original question, but I am going to have 2 MPPT's with the same panels, etc. listed above. I do not believe this will change the wire size for each run.
 

timselectric

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It depends on how you wire the arrays. Series adds voltage. Parallel adds amperage. Wire size, is determined by amperage and distance.
 

timselectric

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It depends on how you wire the arrays. Series adds voltage. Parallel adds amperage. Wire size, is determined by amperage and distance.
Just re read.
Didn't catch the "only 2 panels", the first time.
10.31 amps at 20 ft, could get away with 12 gauge wire easily.
 

timselectric

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That's a very small amount of solar. Not sure what you want to accomplish. No need for 2 MPPT's.
Just wire the panels in series and connect to the mult-plus. Although, I'm not sure what the minimum voltage is, for the mult-plus.
 

Neon

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Perhaps I should have placed this in the Vehicle Mounted Systems category. This will be on an RV, and the 1700W (2X 850w) will physically max out my roof. Probably should have mentioned this, but I was trying not to cloud the original question on wire size. :)
 

timselectric

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Perhaps I should have placed this in the Vehicle Mounted Systems category. This will be on an RV, and the 1700W (2X 850w) will physically max out my roof. Probably should have mentioned this, but I was trying not to cloud the original question on wire size. :)
So, it's 4 panels?
 

timselectric

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Probably should have mentioned this, but I was trying not to cloud the original question on wire size.
Mobile or stationary, makes no difference to wire size. Just need clarification on the number of panels.
 

CamoGreg

5 yr RV Fulltimer
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Jun 18, 2020
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Stay under 25A to the SCC and 10awg is fine for a wire run at RV mounting distance.
 

timselectric

If I can do it, you can do it.
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Yes, 4 panels in total, but there will be two different systems. 2 Panels with its own wire run and MPPT. Hope this is clear.
Yes, 10 gauge as CG said, for paralleling two panels.
12 gauge, if putting two panels in series.
 

rmaddy

Full-time Solar-powered Trailer Life
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Save a few dollars and get the 150/60. 2 425W panels on a 12V system is about 60A of charge current at best. The 70A charge controller will go underutilized.
 
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