Wiring Solar panels

[Bradley]

Would there be anything improper about trimming off enough wire strands so that a yellow (#10) connector could be crimped on to the # 6 wire and be sure to use heat shrink the crimp to seal the joint. Seems like this would be less work and one less failure and corrision point.

[hellosailor]

It would work, but unless you are going to do a seamanlike "splice" that picks out individual wire strands and reduces the bundle over a longer span, say, over a foot long piece, you're still going to have #6 cable "wagging" the #12 tail, work hardening it at the change point. And I'd suspect that no matter how neatly you did it--there would still be some ABYC code issues, or something similar that an insurance survey might object to. AFAIK real electricians always use pigtails or connectors to change guages as needed. That doesn't mean it is the only way to do the job well--just that there's usually some reason why they do it that way.

[schoonerdog]

Hmm, I guess advantage to the MX 60 the, into which you can put huge wire leads. I would think that lead in wires could be brought to a bus bar and then stepped down the short distance to the blue sky. For my particular system as it's going from 36 volts or so to 12 and the 12 volt run is around 7 ft. Thus I really do need huge output terminals going to the battery bank.

Originally Posted by Fishspearit

The size of the wire is one of the things that has surprised me. I hadn't been expecting to run a pair of #6 wire through my deck, your chart showed me needing something between #4 and #6 (a 3% voltage drop would allow me to use #6).

Apparently Blue Sky didn't think about this either(or didn't care), because the terminals on the mppt are sized to handle the little miniature ring terminals that aren't as wide as the #6 wire. So after running 20 feet of nice heavy wire through my deck and boat I have to add another weak link and splice in a foot of #12 wire going in and out of the MPPT. Any better wiring solutions than this?

[GordMay]

Originally Posted by Bradley

Would there be anything improper about trimming off enough wire strands so that a yellow (#10) connector could be crimped on to the # 6 wire and be sure to use heat shrink the crimp to seal the joint. Seems like this would be less work and one less failure and corrosion point.

Since #6 AWG wire is roughly twice the diameter (but about 4 times the cross-sectional area) of #12 AWG wire*, connecting the two sizes together is problematic.

The “proper” way to change wire gauges would be to use ring terminals on a terminal or stud block, or a step-down crimping sleeve (butt splice). Unfortunately, the terminal block is large & unsightly, and step down but splices are only available in smaller sizes (maximum I’ve seen are #8 to #10-12).

I don't recommend trimming strands off the larger wire, as this further decreases the ampacity of the installation.

This leaves two practical “work-around” alternatives, neither of which is entirely satisfactory:

- Utilizing a #6AWG butt splice, install the stripped #12 AWG conductor bent back on itself 3 or 4 times, making it roughly the same size as the #6 open barrel end.

- Utilize a #4 AWG butt splice, inserting the stripped and bent double #12 & single #6 conductors into the same barrel end, and sealing the unused end. This method allows both conductors to be tied together, preventing flexure on the smaller wire.

*In American Wire Gage every 6 gauge decrease gives a doubling of the wire diameter, and every 3 gauge decrease doubles the wire cross sectional area.
#6 = 0.1620" diameter, 24,358 CM2 area
#12 = 0.0808" diameter, 5,833 CM2 area
CM2 = Circular Mills

Pictured is a Blue #14-16 to Red #18-20 Step-Down Butt Splice

[Wotname]

In my book, every way is messy, some more so than others (you pays your money and you take your chances).
The following method is also messy but "looks nice".
Use #6 AWG butt splice. Put the #6 AWG wire in one end.
Turn up a soft copper ferrule on a lathe with ~ OD of 0.1600" and an ~ ID of 0.0800". Tin the ferrule carefully, put it in the other end of the butt splice and then put the #12 AWG wire inside the ferrule. Crimp both sides of the splice and if vibration isn't an issue, lightly solder the crimp.

[GordMay]

Another alternative are Buchanan Splice Cap Crimp Connectors
Ideal / Buchanan Splice Cap Crimp Connectors #2011S (#14 thru #4 AWG Min. 2 #10 / Max. 2 #6)
c/w Insulated Caps #2014
Which requires a “special” Buchanan #C24 Crimp Tool (4-way)

IDEAL INDUSTRIES, INC. - Splice Cap Crimp Connector (Box of 500)

[GordMay]

"All About Marine Wire Termination" is an excellent general illustrated tutorial on the subject:
All About Marine Wire Termination Photo Gallery by Maine Sailing at pbase.com

It's one among many excellent illustrated tutorials by our very own Acoustic, at "How To" - The Boat Projects & Upgrade Blogs presented by Maine Sailing:
"How To" - The Boat Projects & Upgrade Blogs Photo Gallery by Maine Sailing at pbase.com

And more photos & stuff at:
Maine Sailing's Photo Galleries at pbase.com

[Therapy]

Originally Posted by GordMay

"All About Marine Wire Termination" is an excellent general illustrated tutorial on the subject:
All About Marine Wire Termination Photo Gallery by Maine Sailing at pbase.com

It's one among many excellent illustrated tutorials by our very own Acoustic, at "How To" - The Boat Projects & Upgrade Blogs presented by Maine Sailing:
"How To" - The Boat Projects & Upgrade Blogs Photo Gallery by Maine Sailing at pbase.com

And more photos & stuff at:
Maine Sailing's Photo Galleries at pbase.com

That guy is simply amazing.
I thought I had seen all his stuff. I missed that one.
Thanks Gord.

[GordMay]

Indeed - Acoustic's Maine Sail's Sailing Photo Galleries < http://www.pbase.com/mainecruising > are an excellent resource. The photo essays are clear, informative (accurate), and professionally presented.

[marno]

Rather than using the splice crimp connectors above, you could use these (bottom of page) http://www.wurth.co.uk/catalogue/pdfs/UK-CD_02_0606.pdf and avoid having to use a special tool (a heat gun or lighter will shrink the external heat shrink and melt the low temp solder). If you wanted to ensure mechanical connection as well you could always use heatshrink.

[richardhula]

Never heard of wiring essentially 12 volt solar panels in series unless you want to charge a 24 volt system. They should always be wired in parallel and to a suitable controller. I guess if the raw output is less than 13.5 volt on a sunny day you may have to revise that but generally a "12 volt" solar panel will put out 17 volts or more raw off load.

I have two Kyocera KC130TM's wired with 10-2 round cable to one Blue Sky Solar Boost 2512i controller. This runs the panels at higher than normal voltage to acheive max efficiency then converts it back down to charge batteries with normal three stage boost/equalise/float.

I have seen 15 amps going into my 12 volt battery bank whilst running two fridges. This exceeds their claimed output.

Regards - Richard

[Badsanta]

I would also install a breaker on the solar line. If you need to work on other electric and turn your batteries off to de energize the system, the solar will be pumping in energy unless you work at night.

[Paul Elliott]

Originally Posted by richardhula

Never heard of wiring essentially 12 volt solar panels in series unless you want to charge a 24 volt system. They should always be wired in parallel and to a suitable controller.

MPPT controllers will typically take a 24V or 48V input and step it down to the proper charging voltage for a 12V battery.

Advantage: Smaller gauge wire needed from panels to the charge-controller.

Disadvantage: Shading of even one of the series-connected panels will probably reduce the output of the entire string. You can add bypass diodes to help.

[OceanPlanet]

Uh...unless I missed it, no one here has pointed out that to get the max amps from separate panels he should have an MPPT controller on each panel. Four small ones will do better than one big MPPT for all four panels.