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Old 24-08-2014, 19:54   #31
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Re: Solar Panel Combinations and Orientation Options

Good point. Whichever I do I will go for the highest voltage the mppt reg can handle.


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Old 25-08-2014, 17:47   #32
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Re: Solar Panel Combinations and Orientation Options

I believe the best install practice would be 4x70 with each panel to a small MPPT controller. When I was in the business we did a lot of these with Genasun controllers. Shading one panel had no impact on the others and each always put out the max

Series configurations are great with no shade but I've never seen a boat with no shade (but still looking!)


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Old 25-08-2014, 18:33   #33
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Re: Solar Panel Combinations and Orientation Options

Quote:
Originally Posted by Scott Berg View Post
I believe the best install practice would be 4x70 with each panel to a small MPPT controller. When I was in the business we did a lot of these with Genasun controllers. Shading one panel had no impact on the others and each always put out the max

Series configurations are great with no shade but I've never seen a boat with no shade (but still looking!)
Thanks Scott, this echos something I thought I had seen suggested. Is there a chance you have made this suggestion on CF before? I am not sure where I first read the idea but it made sense when I did.

Matt
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Old 25-08-2014, 18:36   #34
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Re: Solar Panel Combinations and Orientation Options

We studied and studied, thought and thought, and never felt comfortable with what we learned. Finally, we bought 2 Sunpower 345s and paralleled them to a Morningstar MPPT 60. We live aboard, have lots of 12v goodies (most significantly a fridge and a freezer) and wake up every morning with the battery monitor showing us down around -115ah. Most days our 900ah house bank is full by 1330hrs. The Morningstar quits putting amps in the batteries while there is still several hours of sunlight left but meets our normal 9-10a 12v load until the sun goes low when amps start coming out of the batteries again. So we know we have a surplus, we just haven't figured out how much. I've started experimenting with things like using the inverter to power the water heater, trying to find out how much I can use before I am not getting the batteries topped off every day.

We have shading every day for part of the day. If it's not the mizzen boom, its the mizzen mast or less noticeably the standing rigging. It definitely reduces the solar panel output. How much? I dunno. What I do know is that here in the FL keys, I have not turned on my battery chargers since the day the solar panels went online back in January. I have decided to quit over-analyzing and just be happy. Boy, am I happy!

My advice? Just do it!
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Old 25-08-2014, 18:46   #35
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Re: Solar Panel Combinations and Orientation Options

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My advice? Just do it!
Absolutely.
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Old 25-08-2014, 18:55   #36
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Re: Solar Panel Combinations and Orientation Options

when we added the solar, having them out of the way was as inportant as much as anything else. we chose good quality panels and followed it by a quality controler..
we found that trying to figure where the best place to install them was a waste of time as when the wind changes direction, all your figures go out the window so to speak.
our choice was to go as large as possible to fit within the space allowed and live within those limmits..
we have changed our use durring the last few years as run the reffer dirring peak hours, run the watermaker durring peak hours and so on.
I built a custom rack atop the bimini of 1 inch ss. the the bimini is made of 1 &1/4 SS. looks good, works well, and strong enough to take a rogue wave over the top.. yes it did happen off the lighthouse at Point Reys..
our panels are 140 each and even with the occassional shade, we still have more power than needed
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Old 25-08-2014, 19:34   #37
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Re: Solar Panel Combinations and Orientation Options

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Originally Posted by SailFastTri View Post
You're assuming he wires them in parallel. For the best output he should take advantage of the MPPT controllers' ability to do voltage conversion. This would dictate that the 2 X 140s would be wired in series, or the 4 X 70s be connected in series-parallel as two pairs. In that case he effectively has two logical panels, or one logical panel (from an electrical perspective).
If unshaded, this higher voltage would reduce wiring losses and give the MPPT controller a huge performance boost by allowing it to operate in more efficient ranges for more hours per day (and in lower light when it's a bit overcast).
I have 8x20w panels and have tested both ways (parallel vs. series/parallel) and while I can't put a precise number on it the difference in the real world is huge (perhaps 50% improvement).

Note: corrected above to "parallel vs. series/parallel"

That's assuming his MPPT controller can handle the higher voltage of series panels.
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Old 25-08-2014, 19:43   #38
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Re: Solar Panel Combinations and Orientation Options

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Originally Posted by Scott Berg View Post
I believe the best install practice would be 4x70 with each panel to a small MPPT controller. When I was in the business we did a lot of these with Genasun controllers. Shading one panel had no impact on the others and each always put out the max

Series configurations are great with no shade but I've never seen a boat with no shade (but still looking!)


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I would agree with you if he was talking about using 4 x 300w panels. He could then wire them to 4 x 20 A controllers and get roughly 18.5-19 A per controller under ideal conditions.

However, using such low power panels and then roughly quadrupling the power loss of the controllers might eat up any potential gains in efficiency under shaded conditions. This loss varies by brand and size, but add it in to the losses of 4 sets of cables and it might not be worth it, not to mention cost.
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Old 25-08-2014, 19:46   #39
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Re: Solar Panel Combinations and Orientation Options

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Originally Posted by GILow View Post
Thanks Scott, this echos something I thought I had seen suggested. Is there a chance you have made this suggestion on CF before? I am not sure where I first read the idea but it made sense when I did.

Matt
There was another thread where I posted that I was thinking about installing 14 x 300 w panels on a catamaran and using $100 20 A MPPT controllers, one for each panel. I also considered carrying 3 or 4 extra MPPT controllers, since they're so cheap.
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Old 25-08-2014, 19:50   #40
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Re: Solar Panel Combinations and Orientation Options

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Originally Posted by F51 View Post
We studied and studied, thought and thought, and never felt comfortable with what we learned. Finally, we bought 2 Sunpower 345s and paralleled them to a Morningstar MPPT 60. We live aboard, have lots of 12v goodies (most significantly a fridge and a freezer) and wake up every morning with the battery monitor showing us down around -115ah. Most days our 900ah house bank is full by 1330hrs. The Morningstar quits putting amps in the batteries while there is still several hours of sunlight left but meets our normal 9-10a 12v load until the sun goes low when amps start coming out of the batteries again. So we know we have a surplus, we just haven't figured out how much. I've started experimenting with things like using the inverter to power the water heater, trying to find out how much I can use before I am not getting the batteries topped off every day.

We have shading every day for part of the day. If it's not the mizzen boom, its the mizzen mast or less noticeably the standing rigging. It definitely reduces the solar panel output. How much? I dunno. What I do know is that here in the FL keys, I have not turned on my battery chargers since the day the solar panels went online back in January. I have decided to quit over-analyzing and just be happy. Boy, am I happy!

My advice? Just do it!

That's awesome!

I'll be interested to hear about further experiments in trying to use up some of that excess power with the water maker or whatever high current loads you may have.
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Old 25-08-2014, 20:48   #41
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Re: Solar Panel Combinations and Orientation Options

Bought the 450 Watt MPPT Votronic regulator and LCD display in the end. 50V max so I have some flexibility in wiring the panels.

Now I am trying to decide between two cheap 140W panels as a short term solution (5 years) or 4 better quality 70W panels as a longer term option (10 + years.). I could not find a cheap 4 panel option that made financial sense, so I know I am not comparing apples with apples.

The panel choices are very much dictated by the space available.

Matt
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Old 25-08-2014, 21:35   #42
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Re: Solar Panel Combinations and Orientation Options

Quote:
Originally Posted by Scott Berg View Post
I believe the best install practice would be 4x70 with each panel to a small MPPT controller. When I was in the business we did a lot of these with Genasun controllers. Shading one panel had no impact on the others and each always put out the max

Series configurations are great with no shade but I've never seen a boat with no shade (but still looking!)


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This is my understanding.

The advantage to series and MPPT is more in the fact that the panels are capable of producing more than the system voltage (say system voltage of 14.4v for charging) and the mppt converts the high "excess" voltage to amperage.

However because the current flows from panel to panel a shaded panel in the series can seriously degrade the whole chain of panels.

And yes there are "good" quality panels with more diodes etc. but if you are installing a "modest" array that may be subject to shading I would wire them as Scott suggests.

Each panel then becomes it's own entity.
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