Solar Panel Layout and Cabling for Coleman CTS192 - Dutchmen Owners

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Old 04-28-2017, 06:02 AM   #1
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Solar Panel Layout and Cabling for Coleman CTS192

Attached is a solar panel layout which might work for my TT. I designed it wanting to maximize winter solar with tilting South facing panels. A problem with this is the wire length between the panels and the MPPT controller on my <23 TT (bumper to hitch). I want the panels in parallel so partial shading of one panel does not dramatically impact the power output of the whole bank, as in series connections. A combination of parallel and the cable run leads to a voltage drop incompatible with the MPPT controller according to Renogy.



If anyone has gotten around this voltage drop problem, maybe a really wide diameter cable, I'd like to hear the solution. Another problem is getting the cables to the MPPT controller in the battery box without duct taping the solar output cable to the face of the TT. I'm thinking I could run the cable through the refrigerator vent, through the floor, and then under the TT to the battery box but that seems unsafe - kind of like that rubber propane hose running under the TT



Id also like to contact any recommended electricians or solar experts in the Frederick County VA area about this solar setup and some other TT 12Volt and AC wiring issues.


Thanks!
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Old 04-28-2017, 03:30 PM   #2
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Are they 12V nominal panels? What about putting the pairs of 100 W in series and have three parallel arrays? Is this what Renogy says won't work because I can't see why? Put a combiner box on the roof and run 4 gauge from the combiner to your controller.

I just bit the bullet and drilled a 1" diameter hole in my roof beneath the combiner box to get the wires inside. I was advised against trying to open up the walls to hide wires so I drilled my hole right at an interior corner and went with wire conduit along that wall corner and along the floor to get the wires to front of the TT to the pass through storage area where I mounted the controller. Then from the controller I went through the floor and along the underside of the frame to the batteries on the tongue which was about 5' of wire length. The underbelly of the TT is covered in coroplast so the wiring is not exposed on the underside.
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Old 04-30-2017, 02:07 AM   #3
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Hi ewarnerusa,

Yes they are 12V nominal panels - https://www.renogy.com/renogy-100-wa...e-solar-panel/. Just checked and these are pricier now. A while back Amazon had them for about $100 so I might look at other alternative panels.

Renogy said I could connect the panels in series to get around some of the problem (I could use a lighter gauge wire if in series vs parallel) but I really want to run them all in parallel to prevent power loss when only a single panel is shaded.

I'm not familiar with combiner boxes and did a search - https://www.altestore.com/store/encl...in-rail-p10397. Is the type of combiner box you placed on your roof?

Running the wiring through conduit in the trailer sounds like a much better idea instead of through the wall or worse yet along the front of the coach. I was looking around at conduit and found this for running under the trailer - https://www.walmart.com/ip/AFC-Cable...nduit/47502185. This looks like it could take some abuse

Thanks!
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Old 04-30-2017, 06:59 PM   #4
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Originally Posted by WannaBeFree View Post
Hi ewarnerusa,

Yes they are 12V nominal panels - https://www.renogy.com/renogy-100-wa...e-solar-panel/. Just checked and these are pricier now. A while back Amazon had them for about $100 so I might look at other alternative panels.

Renogy said I could connect the panels in series to get around some of the problem (I could use a lighter gauge wire if in series vs parallel) but I really want to run them all in parallel to prevent power loss when only a single panel is shaded.

I'm not familiar with combiner boxes and did a search - https://www.altestore.com/store/encl...in-rail-p10397. Is the type of combiner box you placed on your roof?

Running the wiring through conduit in the trailer sounds like a much better idea instead of through the wall or worse yet along the front of the coach. I was looking around at conduit and found this for running under the trailer - https://www.walmart.com/ip/AFC-Cable...nduit/47502185. This looks like it could take some abuse

Thanks!
Take a look at the Carlon electrical products page. The green field will work but the Carlon PVC conduit is much easier to work.
Carlon Sales | Purchase Carlon Conduit, Floor Boxes, Enclosures, Wireway, & More!
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Old 04-30-2017, 07:08 PM   #5
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By combiner box I meant any type of wire distribution method enclosed in a weather protected case. What you posted will work. I used a distribution block like at the following link that I put inside a wire conduit box that I bought from the hardware store.
XScorpion 4 / 8 Gauge Distribution Block - Darvex.com
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Old 05-01-2017, 03:59 AM   #6
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Thanks sundancer 87,

I'll check out the PVC conduit. Should it be about as rugged when running under a trailer? One big positive with the PVC is no rust as compared to the steel conduit
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Old 05-01-2017, 04:53 AM   #7
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Thanks ewarnerusa,

Looking at the distribution block page I see - "One 4 gauge input with four 8 gauge outputs". Not really for sure what this does. I'm guessing you plug up to four solar panel positive leads into the 8-gauge side and one 4 gauge positive lead comes out the other side. I'm not for sure what this would do to the volts and amps but I'm guessing it would be like a parallel connection as you are essentially connecting positive to positive for each of the 8 gauge inputs. And then for the negative wires from the panels I'm guessing you would use another distribution block?

Also, are you aware of a web site which shows the voltage drop over 4 and 8 gauge wires based upon wire length? If I can run the 8 gauge wires from the panels as far as ~ 20' (from the rear of the TT to the front) and then feed the panel wires into the distribution block, I would then need about 12' of 4 gauge wire to drop from the roof, through the floor, and out to the battery box with the charge controller.

Combining two panels in series would give me about 24V. I'm sure I would lose some voltage over the ~ 20' run from the rear of the TT to the front and ~ 12’ from the roof top to the battery compartment but with a 50% loss in voltage I'd still be at 12V. I'd be losing power in both panels when only one panel of a pair is shaded but it sounds like this would work.
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Old 05-01-2017, 12:53 PM   #8
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Thanks sundancer 87,

I'll check out the PVC conduit. Should it be about as rugged when running under a trailer? One big positive with the PVC is no rust as compared to the steel conduit
Just as rugged and lighter and easier to cut. The blue flexible conduit can be cut with a sharp knife and is great to work also. My local electrical supply house doesn't sell it anymore but maybe that's just them.
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Old 05-01-2017, 03:10 PM   #9
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Originally Posted by WannaBeFree View Post
Thanks ewarnerusa,

Looking at the distribution block page I see - "One 4 gauge input with four 8 gauge outputs". Not really for sure what this does. I'm guessing you plug up to four solar panel positive leads into the 8-gauge side and one 4 gauge positive lead comes out the other side. I'm not for sure what this would do to the volts and amps but I'm guessing it would be like a parallel connection as you are essentially connecting positive to positive for each of the 8 gauge inputs. And then for the negative wires from the panels I'm guessing you would use another distribution block?
Yes, you got it. It doesn't do anything to your volts and amps, that depends on how you tie the panels into your combiner bus. You have essentially provided an extension of the charge controller inputs to the TT roof, so tie them in however you see fit.

Quote:
Originally Posted by WannaBeFree View Post
Also, are you aware of a web site which shows the voltage drop over 4 and 8 gauge wires based upon wire length? If I can run the 8 gauge wires from the panels as far as ~ 20' (from the rear of the TT to the front) and then feed the panel wires into the distribution block, I would then need about 12' of 4 gauge wire to drop from the roof, through the floor, and out to the battery box with the charge controller.
Here's what google found for me.
Voltage Drop Calculator
Your 8 gauge to the combiner box and 4 gauge from there to the controller is exactly what I was describing. I would feel good about that setup on my camper.

Quote:
Originally Posted by WannaBeFree View Post
Combining two panels in series would give me about 24V. I'm sure I would lose some voltage over the ~ 20' run from the rear of the TT to the front and ~ 12 from the roof top to the battery compartment but with a 50% loss in voltage I'd still be at 12V. I'd be losing power in both panels when only one panel of a pair is shaded but it sounds like this would work.
I personally wouldn't worry about it, you've got the potential to exceed C/10 charge rate anyway so think of it as built in protection for your batteries from too high of a charge current. :-)
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Old 05-01-2017, 06:24 PM   #10
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Thanks sundancer 87,

That blue flexible conduit sounds like the way to go
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