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Solar wiring from roof to charge controller questions

solar ATC Bobcat

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#1 ootnaboot

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Posted 31 August 2021 - 11:22 PM

Hey everyone. I'm trying to build the solar system for our 2014 Bobcat and I've run into a big issue regarding wiring from the panels to the charge controller that I'm hoping someone might help with some guidance.

 

Here's the situation: Marty and the ATC gang pre-installed the camper for solar with 14awg wiring. Now originally, the plan has been to use two 153w polycrystalline panels we have. However, given that each panel puts out Vmp 18.8V and Imp 8.14 A, from what I can tell from my research, 14awg wire is too small to handle those loads, both in terms of loss and safety, if we were to run them in parallel. If I run them in series, I think we'd be okay. Maybe still on the edge of too small, but maybe not. Of course, with the panels in series, you get the shading problem. So, preferably, they're run in parallel. And that only makes sense if we go with a larger gauge. But...and this is the big but: from what I've gathered talking to Marty and others, 12awg is the largest we can run between the panels and the charge controller. Otherwise, the forward panel will not collapse well and the camper won't close right. To be sure, I totally trust Marty and the gang. But I'm wondering from anyone else's experience how y'all got around this issue if you installed that much solar power.

 

Thanks! And keep on wandering.

 

P.s., I've attached a pdf of the info label on the back of the panel if that helps you solar gurus understand my situation better.

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Edited by ootnaboot, 01 September 2021 - 12:56 AM.

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#2 rando

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Posted 01 September 2021 - 01:25 AM

You could certainly run larger wire behind the lift panels if it is fine stranded wire (which is more flexible) and has thinner jacket.   Both FWC and ATC don't use the best wiring in their builds.   

 

But I am not sure you need to change the wire.    From a safety perspective, 14AWG wire is rated for at least 17A, and likely 35A if it has high temperature rating jacket.    You could put the panels in parallel, but you would loose some power to voltage drop and maybe closer to the max rating than you want.   In series (and assuming an MPPT charge controller) the current would be totally fine, and the losses would be lower.   Assuming the panels have bypass diodes (which they almost certainly do) then there is not much difference between series and parallel panels in terms of the impact of shading.   Rewiring the roof seems like a pain, so I would use your existing wire with the panels in series. 


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#3 Vic Harder

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Posted 01 September 2021 - 02:40 AM

+1 on what rando said. FYI I have 330W on my roof, single panel.  I plan to get an even bigger panel once the 600+W panels hit the market.  Still with the stock ATC wiring.


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#4 ntsqd

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Posted 01 September 2021 - 01:16 PM

If re-wiring is determined to be the path forward you may be able to use the existing wire to pull the new, bigger wire thru whatever contortionist path was used.

 

However, I also think that upping the voltage with the panels in series is the better idea. Just generally a more efficient way to do it. This is why the long distance power lines run at 500,000 volts or more. Less overall line loss.

 

A single 600W panel sounds ginormous! What would be it's Vout?


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#5 Vic Harder

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Posted 01 September 2021 - 03:11 PM

45.8V open circuit according to the data sheet.  Physically larger too at 94" long.

 

Canadian_Solar-Datasheet- HiKu7_CS7N-MS_(1000V & 1500V)_EN (csisolar.com)


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#6 ootnaboot

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Posted 02 September 2021 - 04:38 PM

Thanks a ton for the replies! I’d rather start with the least invasive (install in series with the 14awg already installed) and adjust from there if necessary. And thanks for pointing out about the better quality (and more flexible) wire.

Will update if anything comes up. Cheers!
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