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Old 16-07-2012, 11:11   #1
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Solar Panel Question

hey folks,

I have two identical solar panels mounted on my boat, 140w each, with a max output of 19-point-something volts. I run them in parallel, into a Blue Sky Energy 3024iL MPPT controller.

I would like to add another panel, but as I am cruising in the Sea of Cortez currently, my easily-available choices are somewhat limited. I see a few large panels (240w) available, and we have the deck space for one - my question is whether or not that would be a good plan, and if so, how to properly hook it up?

For instance, I believe one of the panels for sale locally is 48v. Would I be best to run my two current panels in series, then parallel them with the 48v panel...?
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Old 16-07-2012, 12:02   #2
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Re: solar panel question

To use the same MPPT controler the solar panels need to be reasonably matched.
The Vmpp should be within 0.5v.

If you use a second controler you can attach what you like.
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Old 16-07-2012, 12:13   #3
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Re: solar panel question

There are two important specification for your charge controller that are important in this situation: maximum input voltage and maximum output current.

Wiring your existing 140 watt, 19 V panels in series and then paralleling them with a new 240 Watt, 48 V panel should work, but it will be very marginal.

The rated input voltage on your controller is 57 V but the recommended maximum is 45.6 V (who knows what that means!!!). When your batteries are full and your controller starts raising the input voltage to keep the current low, the maximum input voltage will go to 48 V, somewhere between maximum and recommended. You figure out what the risk is here?

The maximum output current for that controller is 40 amps at 12 V or 480 watts. In full sun you will be making 520 watts at the panels which will be maybe 10% less at the output due to bringing all three panels to the same input voltage as well as controller conversion losses. So it wll be real close to 40 amps in direct, perpendicular sun. Most controller manufacturers and design codes suggest reducing the current rating of controllers by 20% or so as a safety factor, so you could be in trouble there.

Like I said it will be marginal, but may work. I would be happier with a new 200 watt, 38 V panel.

David
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Old 16-07-2012, 12:39   #4
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Re: solar panel question

Quote:
Originally Posted by djmarchand View Post
The rated input voltage on your controller is 57 V but the recommended maximum is 45.6 V (who knows what that means!!!
It is very important not to exceed the maximum voltage of MPPT regulators, even briefly it will usually damage the controler.
The Blue sky controler has an absolute maximimum of 57v but Blue sky recommend having a maximium Voc ( note not Vmpp) of 45.6 because in some circumstantances panels can exceed their Voc. Panels with a Voc of 57v would therefore damage the controller. 45.6 v alows some leeway to make sure the absolute max is voltage of 57v is never exceeded.
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Old 10-08-2012, 03:34   #5
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Re: solar panel question

what is the diff between MONO and POLY type panels ?
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Old 10-08-2012, 04:02   #6
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Re: solar panel question

The differences are very small. Mono crystalline cells are slightly more effecient, but take up a little more space so when mounted in a panel the effeciencies tend to be similar, although carefully made mono panels are slightly more effecient generally. Lifespan temperature effects, shading etc are almost identical.
When buying look at the watts per square foot or metre to work out how the panels compare. Matching the panel size to the space you have available is often the most important thing in getting the most watts. Fit the maximum watts you can if it's mono or poly is not important.
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Old 10-08-2012, 05:19   #7
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Re: solar panel question

OK, and thanks. i am looking at the flexsi type Solara M series to go on my roof.
there are 2 types 42 cells and 36 cells 70Watt and 68 watts.
They are Poly type.

Solara SM225M Solar Panel
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Old 10-08-2012, 09:32   #8
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Re: solar panel question

Take a look at Aurinco panels.
I got a couple of 100 watt panels for less than the price of the 68 watt panels on the Solara link.
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Old 10-08-2012, 12:50   #9
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Re: solar panel question

Are they the same quality ?
and where are the pictures ?
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Old 10-08-2012, 15:19   #10
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Re: solar panel question

Quote:
Originally Posted by senormechanico View Post
Take a look at Aurinco panels.
I got a couple of 100 watt panels for less than the price of the 68 watt panels on the Solara link.
Aurinco solar panels
to me they look like more costly ?
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Old 10-08-2012, 17:04   #11
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Re: solar panel question

Aurinco's web site proudly announces that their 2011 models have arrived. Uh, the 2011 cars arrived just short of two years ago. When I see something like this it tells me no one is really taking care of business at the company, you're dealing with some kid in a basement whose uncle has a connection to a panel maker, or some equally reliable source and vendor.
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