Solar Wiring : Series vs Parallel

[2TheStreet]

I just added 400 watts of the bendable solar panels to my 04 chevy express 3500. I first wired my solar panels in parallel but didn't like all of the excessive wiring from having to get wire extenders and branch connectors. I contacted Renogy and they said I can wire the panels in series since I have their 40 amp MPPT solar controller. So I removed all of the extra cabling and connectors and shipped them back to amazon, re-wired the solar panels in a series (array). I check my meter and it says the batteries are at 13.2 volts with 0 amps coming in. However, my battery was fully charged before making the switch. Before the switch, when the solar panels were wired in parallel, the meter showed 13.7 volts with about 1-2 amps coming in at the time, very cloudy out. Should I go back to a parallel wiring set-up? What wiring system are you all using? Which is best?i

What happens when the battery is full? Does the solar controller cease charging the battery or does it go into float mode? Excuse me I'm a new at this solar stuff.

 

[MikeRuth]

Your going to get better answers than mine but first thing I would do is verify the voltage at the MPPT controller.

So with good light coming down, I would first cover the panels then disconnect at least one lead from the controller,hook up a DVM and set it to at least 100 volt scale and connect to the end of the array. Uncover the panels and see what the reading is.
If you have 4 100 watt panels that are say-rated to 21 volts open circuit then again in bright light you should see about 80 to 86 volts DC at the end of this series.

 

[highdesertranger]

when running parallel if you get partial shading on one panel it will only effect the one panel. when running in a series partial shading on one panel will effect all the panels in the series. highdesertranger

 

[2TheStreet]

Thanks for the responses. I'm going to go back to a parallel connection but will do custom wiring to get the exact size wiring. I ordered the mc4 connectors and branch connectors, will get THHN 8 AWG wire by the foot at Lowes for $0.59/ ft. Btw, here are the links to get the mc4 connectors alone for cheap and I found cheaper branch connectors than Renogy's price $12.99 branch connector pairs.

Get MC4 connectors here cheap: http://amzn.to/1LeTY6H
Get branch connectors pairs $4 cheaper here:http://amzn.to/1SkWJUi

 

[highdesertranger]

that wire THHN is for residential use. that type of wire is very stiff and usually doesn't work well in automotive applications. a much better choice would be SGT or SGT-M(marine) or SGX(high temp). these are fine stranded wires and are very flexible much better for automotive applications. highdesertranger

 

[2TheStreet]

that wire THHN is for residential use.  that type of wire is very stiff and usually doesn't work well in automotive applications.  a much better choice would be SGT or SGT-M(marine) or SGX(high temp).  these are fine stranded wires and are very flexible much better for automotive applications.  highdesertranger

THHN works fine, I know a guy that uses it on his van. I picked some 8 AWG THHN wire at THD for $0.49/ft.  I really don't want the wire to be flexible, the stiffer the better, because it will stay in place better on the roof, also THHN exterior is thinner making the 8 AWG THHN Wire even thinner the 10 AWG cable that I bought from Renogy and fits better through openings. If it doesn't work right I can always switch back. I'll keep you all updated though my YT channel.

 

[highdesertranger]

make sure you give it a relief circle where it terminates. I have seen that wire snap at the termination point because of vibration. highdesertranger

 

[2TheStreet]

make sure you give it a relief circle where it terminates.  I have seen that wire snap at the termination point because of vibration.  highdesertranger

I have a difficult time believing this THHN home depot wire snapping due to vibration, this wire is a SOB to cut. It's strong stuff. I installed the THHN wire yesterday and it installed much better than the Renogy wire. It stays in place just as I predicted. I will do an update video on my install. The 8 AWG wire went into the MC4 connectors with no issues, very easy install. I'm glad I'm back to a parallel connection now.

 

[Optimistic Paranoid]

I have a difficult time believing this THHN home depot wire snapping due to vibration, this wire is a SOB to cut. It's strong stuff. I installed the THHN wire yesterday and it installed much better than the Renogy wire. It stays in place just as I predicted. I will do an update video on my install. The 8 AWG wire went into the MC4 connectors with no issues, very easy install. I'm glad I'm back to a parallel connection now.

It’s hard to cut because it’s hard wire.  Hard wire is BRITTLE wire, and it’s the brittleness that causes problems.

Coast Guard regulations and ABYC code FORBIDS the use of solid wire on boats for that reason.

THE BOATOWNERS ILLUSTRATED HANDBOOK OF WIRING says:
“Because copper wire becomes brittle under repeated flexing, solid wire is not allowed at all.  Type II stranding is the minimum allowed for general boat wiring, and Type III stranding should be used wherever frequent flexing is expected, such as on an engine.”

Unfortunately, there are no similar regulations or codes controlling RV manufacturers, and they will frequently cut costs by using the same solid romex wire that is used in houses.
 
But the book RV ELECTRICAL SYSTEMS says:

“These specifications are suitable for buildings but, in our opinion, they are not suitable for RVs. When the RV is moving, the unsupported lengths of wire vibrate and work against any tightly supported wire.  The fatigue in these places eventually causes the wire to harden and fracture, creating open circuits and possible shorts.” 

Oh, and the wire designed for use on solar panels has insulation designed to resist UV.  The insulation on house wiring doesn't need that, so the manufacturers keep their costs low by not worrying about UV.  And THHN is considered suitable only for use in DRY locations, not wet ones,

 

[highdesertranger]

thanks OP I didn't want to keep on him because of that other thread. I hope he is at least using stranded wire. the same applies to the household stranded wire as to the solid core it just takes longer with the stranded, but it will still snap. for RV's using marine wire is an excellent choice. I however gave him a few options that were a little cheaper and would still serve the purpose well. one thing I have learned from ranching is the old saying "you can lead a horse to water, but you can't make him drink" is very true. highdesertranger

 

[Spaceman Spiff]

 one thing I have learned from ranching is the old saying "you can lead a horse to water,  but you can't make him drink"  is very true.  highdesertranger

To which my father would say: ' Ya, but you can put salt in his hay and make him thursty.'

 -- Spiff

 

[highdesertranger]

ha ha good one spaceman. highdesertranger

 

[2TheStreet]

New van build update youtube video. I removed all of the expensive renogy cables and returned them for a refund because they were too bulky for my needs and they do not have 8 awg extension cables or solar cables. Instead I made custom solar cables saved $100+ and don't excessive cabling and will have less power loss due to less cable length and thicker gauge copper wire.

Check out my video on how to make your own custom cables and save money!



Links to get items in video (Since people always ask!):


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Get Cheap THHN Wire by the foot at Lowes or Home Depot![/font]

 

[2TheStreet]

It’s hard to cut because it’s hard wire.  Hard wire is BRITTLE wire, and it’s the brittleness that causes problems.

Coast Guard regulations and ABYC code FORBIDS the use of solid wire on boats for that reason.

THE BOATOWNERS ILLUSTRATED HANDBOOK OF WIRING says:
“Because copper wire becomes brittle under repeated flexing, solid wire is not allowed at all.  Type II stranding is the minimum allowed for general boat wiring, and Type III stranding should be used wherever frequent flexing is expected, such as on an engine.”

Unfortunately, there are no similar regulations or codes controlling RV manufacturers, and they will frequently cut costs by using the same solid romex wire that is used in houses.
 
But the book RV ELECTRICAL SYSTEMS says:

“These specifications are suitable for buildings but, in our opinion, they are not suitable for RVs. When the RV is moving, the unsupported lengths of wire vibrate and work against any tightly supported wire.  The fatigue in these places eventually causes the wire to harden and fracture, creating open circuits and possible shorts.” 

Oh, and the wire designed for use on solar panels has insulation designed to resist UV.  The insulation on house wiring doesn't need that, so the manufacturers keep their costs low by not worrying about UV.  And THHN is considered suitable only for use in DRY locations, not wet ones,

First off, explain to me how THHN wire is going to flex on the roof of my van? You are comparing boats to a van, like comparing apples to oranges. Second, THHN wire IS approved for outdoor use! Have you ever even worked with THHn wire? If you did, you would find out that there is an additional plastic coating that covers the exterior of the sheathing.

You might want to actually take the time out to read the description of the THHN wire at the Home Depot link before you give misinformation:
http://www.homedepot.com/p/Southwir...PIPHorizontal1_rr-_-202316480-_-204632883-_-N

 

[2TheStreet]

I'll let the Home Depot description of their THHN wire do the talking (Wire I purchased by the foot). Btw, If I have any problems I'll be the first one to let you all know!

 

[Optimistic Paranoid]

http://www.ul.com/global/documents/...ctrical/newsletters/W&CMG_April2007_Final.pdf

Lets summarize:  THHN

T stands for Thermoplastic Insulation
H stands for Heat Resistant to 75 degrees Celsius
HH stands for Heat Resistant to 90 degrees Celsius
N stands for a Nylon coating on the insulation
W stands for suitable for use in Wet or Damp conditions.
SR and similar markings as an add on indicate it has been evaluated as Sun Resistant and approved for long term exposure to UV rays.

UL says that any wire used outdoors MUST have a W.  No W means it's only suitable for indoor use.

FWIW, the wire Northern Arizona Wind and Sun sold me was 10 gauge stranded wire marked THWN, with further markings indicating it was Sun Resistant.  Price was around a dollar a foot.

Look, you made a simple, honest mistake.  Some of us were just trying to point that out to you so you could correct it. 

But you've made it pretty clear you don't WANT to be told when you've made a mistake.  So be it.  Carry on.

 

[2TheStreet]

PRODUCT OVERVIEW Model # 20488399 Internet # 204632883
Southwire’s THHN and THWN-2 is a multi-purpose building wire used in conduit and cable trays for service, feeders and branch circuits in commercial and industrial applications. It is also used as a conductor in NM-B, UF-B, SER, SEU and MC. Southwire’s THHN is rated for 600 Volts and has a heat capacity of up to 90* C.
Can be used in wet or dry locations
Made with annealed (soft) copper, compressed
Insulation is high heat and moisture resistant polyvinyl chloride (PVC)
Jacket is abrasion, moisture, gasoline and oil resistant nylon
UL listed, CSA certified and RoHS compliant

 

[2TheStreet]

Just called Renogy and spoke with tech support and asked them was it ok to use THHN wire for solar panels on my vehicle's roof. The technician said it was fine to use but double-checked with his supervisor, whom he said had extensive experience, supervisor said THHN was fine to use for my application.

Like I said if I have any problems I will certainly let you all know.

 

[Optimistic Paranoid]

Just called Renogy and spoke with tech support and asked them was it ok to use THHN wire for solar panels on my vehicle's roof. The technician said it was fine to use but double-checked with his supervisor, whom he said had extensive experience, supervisor said THHN was fine to use for my application.

Like I said if I have any problems I will certainly let you all know.

I doubt that you are going to see any problems anytime soon.  The problems we are talking about - metal fatigue and insulation deterioration due to UV exposure - are the kinds of problems that only show up years later.

Anyway, good luck with your project.

Regards
John

 

[akrvbob]

I'm not an expert on any of this! But, what I do know is that any wire you use on your roof MUST be listed as UV resistant and the listing you posted did not include the words "UV resistant". That would concern me.

I also disagree that boats and RVs are apples and oranges. They share numerous similarities and when it comes to wiring they share vibration which makes them very similiar. Houses, and house wiring have virtually zero vibration so wiring that works in them may not work in a boat or a van.

Bottom line is I might use it inside the van, but I would not use it on the roof. I'd spend the extra money and get the words UV resistant.
Bob