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Old 02-26-2016, 03:13 PM   #1
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Wire size for 90 watt portable solar

I have a 90 watt portable solar kit. The charge controller is mounted near the RV batteries (not on the portable panel). The portable solar kit came with a 30' extension cable made of 10 ga copper clad aluminum (cca) speaker wire. I know that cca is not as good as stranded copper, and am trying to determine:

1. Is it worth making a new 30' cable, or is 10 ga cca acceptable for this application (with a 90 watt panel)?

2. If I need to make a new cable, should I use 10 ga or 8 ga wire (probably marine duplex) for the 30' extension?

Thanks in advance- Bob

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Old 02-26-2016, 03:39 PM   #2
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I have found nice, black and red dual joined fine strand copper wire at Pep Boys, and other auto parts stores. It is disguised as a set of Jumper Cables. They would be useless to get your tow vehicle started if the battery was dead, but if you cut off the cheap, useless little clamps on the ends, they make great wire for solar use. Far less money than buying just wire. I have used this nice wire for several years in the solar systems on both of our Airstreams. I do not use it for a permanent run across the roof. There I used good UV resistant (I hope) wire from a solar supplier.
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Old 02-26-2016, 04:31 PM   #3
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I would use pure copper wire, 10 gage is fine for your panel capacity. Hard to believe that they would supply copper clad aluminum wire in the kit.
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Old 02-26-2016, 06:16 PM   #4
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The handy online calculator, shows 10 gauge Cu wire at 30' long will have .5VDC drop at 90 watts. Going to 6 gauge Cu will have .2 VDC drop. I guess you need to decide how much voltage drop your system is setup for. I would imagine that the design has headroom for voltage drop.
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Old 02-26-2016, 06:20 PM   #5
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I ran 6 gauge for my 100 watt rooftop panel. Approximately 25 foot run.

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Old 02-27-2016, 09:10 AM   #6
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Thanks for you input

Thanks all for your input and ideas. I had done some previous research with voltage drop calculators, but could not find anything specific for cca wire. It may use the same calculations as pure aluminum wire, but I'm not sure. Either way, it does not look like 10 ga cca is the best for a 30' extension (and yes, I too am surprised they would use cca speaker wire).

Here is a link I found this morning that some may find useful to help determine cable size:

Using this tool, 10 ga cu would be adequate for 30'. But when the camper or trailer wire length (to the controller) is added, then it jumps up to 8 ga in my application if I want to keep the voltage drop to 2% or less.

At this point I plan to make an 8 ga 30' extension with Anderson connectors on either end.

Thanks again for all your input- Bob

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