Maximizing solar output - SailNet Community
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post #1 of 13 Old 07-07-2011 Thread Starter
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Maximizing solar output

I have 325 watts of solar installed in 25 panels spread throughout my boat. I have 60 watts in the form of 4 15 watt canvas foldable panels strapped to my dodger, I have 4 15 watt flexible walkable panels on my cabin top in seldom transgressed areas, I have 60 watts on my companion way hatch, 10 watts on my cabin hatch and 40 watts on my forward scoop hatch. I also have 50 watts strapped to the top of my life raft and two 5 watt panels on my head scoop vent box. I have a cluster of 6 5 watt panels on my foredeck. Some of these are permanent notably the hatches, the walkable and the dodger panels. The ones on the foredeck need to be tucked away somewhere while underway. I have quite the collection of wires. I find around 1pm or so my max output is 12 Amps as read by my charge controller - that was the record peak. Normally it reads more like 6 amps. I have decided that the output is less then expected taking shading into consideration. I wonder if the batteries are full and the morningstar charge controller is only allowing as much current as required into the system or if I should somehow consolidate my wiring. I wired all the panels in parallel as they all have a useful charging voltage for lead acid batteries. I was contemplating shortening up the wires but that would only yield a 5 percent or so gain no? I have a feeling there is a lot of efficiency to be gained by rethinking and rewiring. Is it better to say wire everything up to 8 AWG wire and run that straight to the charge controller in the shortest amount of copper possible or to run independent parallel wires? There may be more seaworthiness/ redundancy in more wires. I feel like I should have seen a lot more amps from 325 watts then I have but that may be the nature of the beast...


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post #2 of 13 Old 07-07-2011
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For what it's worth, I have 380 watts of horizontally-mounted panels and normally see something like 16A on a reasonably sunny day, though the record has been over 20A (there's a Bluesky MPPT booster in there, but I saw 21A once before I installed the Bluesky unit).

Maybe there's something seriously wrong with your wiring (like severe corrosion, or severely undersized wiring). You could certainly use an ammeter to test each panel to confirm that each one is performing to spec. Otherwise, I would look at shading and shadowing: a shadow that covers 60% of one cell will cut the output of that panel by 50%.

Larry Shick
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post #3 of 13 Old 07-07-2011
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Thatís a lot of panels.. Many different types of panels is not optimum for maximium output but your output should still be much greater than you are getting If you think the batteries may be regulating try turning on some loads (lights etc) and you will see the output from the solar panels rise.
Get yourself a clamp on multimeter and measure the output from each panel. My guess is you have some defective panels or wiring somewhere. With that many wires and connections outdoors the potential for such as problem is high
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post #4 of 13 Old 07-07-2011
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Oh...no...! That's a load of panels.

Did you every try a Solar Stik? (Ok.. I'll stop. Sorry mods...)

-C2
1987 Sabre 34 "Saoirse"
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post #5 of 13 Old 07-08-2011
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I've not had much luck with flexible panels--but do borrow an ammeter and check the output for each panel--a clamp-on makes it much easier.
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post #6 of 13 Old 07-08-2011
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#1 Are you sure your batts will take more than 12A of charge current?

#2 I have a single 80 watt panel and regularly see about 4.6-4.8A. For 25 panels, and all that wire, mess etc. and expense you really should have considered a dedicated mount for some mono or polycrystalline panels of decent size.. Even a single 130W panel like a Sharp or Kyocera will give you around 7A of charge current.

#3 You likely have some serious shading issue with all those panels which really hurts solar output.

#4 What Model Morningstar controller are you using?

#5 How is it wired gauge wise? Where are they all tied together?

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Last edited by Maine Sail; 07-08-2011 at 05:05 PM.
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post #7 of 13 Old 07-08-2011
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And to add to Maine Sail's questions:

#6: Are your batteries fully charged?

If so, their ACCEPTANCE, will be close to zero, which accounts for your low solar panel input.

Your questions and topics have been a source of great information to many of us on the message board. But, I say, but, there are some "basics" that you may need to want to reconsider, or to consider in the first place.

Like battery acceptance.

I'd just love to see a picture of your four million watt solar array. Really, how do you keep them attached. I am NOT kidding. Your description of your installation has me very puzzled.

All the best,

Stu

Stu Jackson, C34, 1986, M25 engine, Rocna 10 (22#)
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post #8 of 13 Old 07-08-2011
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You stated in your post these panels are all wired in parallel. You may want to consider establishing serially connected banks of "like" panels where possible. This will accomplish two things:

1. clean up and simplify much of the on-deck wiring
2. multiply each solar bank voltage output while reducing the collective voltage/amperage drop due to wire loss (as you already indicated)

Let your Morningstar MPPT (assumed as not stated in your post) controller handle the useable voltage/amperage conversion.

You may also want to consider not all solar panels are equal in terms of efficiency. For instance, poly is less efficient in converting solar to voltage when compared to mono panels. Flexible panels are even less efficient than poly panels. Most advertized panel voltages are measured under optimum conditions in a controlled environment. This is not likely to compare to a "real world" implementation. It is not realistic to expect to achieve advertised performance especially in an environment whereas most everything on deck is coverd by a shadow at some point.

As an interesting confirmation, compare the input voltage/amperage to the controller vs. the output to the batteries.

I do agree with the other opinions regarding battery charge. It is very important to appropriately size your battery bank to your usage. Too small a bank will require you to deplete it too deeply during normal usage. Its like digging a hole in the ground and filling it back up....it will take more dirt to fill it than was removed to begin with.

Like others, I am very interested to see your panel installation....thats a lot of deck real estate!

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post #9 of 13 Old 07-09-2011
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If you sold your boat and bought a trimaran you could easily install 40 or 50 panels.

Brian
Living aboard in Victoria Harbour
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post #10 of 13 Old 07-12-2011
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I'd love to see some pics of the solar layouts people are using, along with mounting suggestions.

This does beg the question: Where would one sit without blocking or breaking a panel?

Capt'n Tom Living Aboard 50/50

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