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Old 02-02-2015, 18:00   #61
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Re: Mixed AWG Solar Install

BTW, good job glossing over the Voc/Vmpp mixup and jumping over to the voltage losses due to NOCT temps. to explain the almost 2v discrepancy between Vmpp and actual panel V.



I'm surprised that the ocean breeze doesn't cool the panels down more.
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Old 02-02-2015, 18:17   #62
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Re: Mixed AWG Solar Install

Interesting technical discussion, but by late afternoon today the controller was in absorption mode with battery volts at 14.2 (gels). Functionally, working great...two days with normal house loads on nothing but solar. Loaded voltage now at 2000 COT, with fridge compressor cycled on, is 12.9.

Maybe this off season I'll tweak it some more. I can get the 8 AWG run down to just a few feet (its only actually about 10' or less now that I've pulled the wiring in the boat). With a bit more effort I can get this down to just a few feet and even beef it up with a bit more work. But for now its time to take a little boat work break and then get into get the hell off the dock mode!
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Old 03-02-2015, 07:40   #63
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Re: Mixed AWG Solar Install

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Originally Posted by belizesailor View Post
Interesting technical discussion, but by late afternoon today the controller was in absorption mode with battery volts at 14.2 (gels). Functionally, working great...two days with normal house loads on nothing but solar. Loaded voltage now at 2000 COT, with fridge compressor cycled on, is 12.9.

Maybe this off season I'll tweak it some more. I can get the 8 AWG run down to just a few feet (its only actually about 10' or less now that I've pulled the wiring in the boat). With a bit more effort I can get this down to just a few feet and even beef it up with a bit more work. But for now its time to take a little boat work break and then get into get the hell off the dock mode!
There are likely easier or cheaper ways to compensate for some of that 8W, like LED lighting. 6 awg will still dissipate 5W and 4 awg about 3W. You are chasing diminishing returns at that point.
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Old 03-02-2015, 08:32   #64
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Re: Mixed AWG Solar Install

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Originally Posted by socaldmax View Post
I'm surprised that the ocean breeze doesn't cool the panels down more.
You would be surprised. Our panels are mounted 2" above the hardtop so that breeze goes under them as well as over them. It is blowing 20-23kts right now in the morning angled sun and I just measured the surface temperature of the panels at 99.3F. By afternoon, I will be frying eggs on them…

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Old 03-02-2015, 12:06   #65
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Re: Mixed AWG Solar Install

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There are likely easier or cheaper ways to compensate for some of that 8W, like LED lighting. 6 awg will still dissipate 5W and 4 awg about 3W. You are chasing diminishing returns at that point.
Energy usage is already low aboard, including mostly LED lighting. Draw is usually well under 10 A.
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Old 03-02-2015, 12:09   #66
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Re: Mixed AWG Solar Install

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Kirchhoff's voltage law (KVL)[edit]

Voltage drop is additive, that is embedded in the definition of voltage/potential.. "Kirchhoff's second law", "Kirchhoff's loop rule" or "Kirchhoff's second rule".
BTW, thanks for posting a response actually relevant to the original question. :thumbup:
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Old 03-02-2015, 12:21   #67
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Re: Mixed AWG Solar Install

Sounds like you have a system functioning well and I wouldn't worry about what little line losses you have until/if there is ever another reason to replace that 8 awg(chafe, corroding wire, etc.).
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Old 03-02-2015, 12:30   #68
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Re: Mixed AWG Solar Install

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By afternoon, I will be frying eggs on them…
Or not…

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