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Old 02-07-2013, 12:45   #1
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1x300w vs 3x100w

I've decided to put on as much solar as I can fit across my davits. Is there a difference or preference to using either 1x300w panel vs 3x100w panels? My controller will be a ProStar PS30m PWM 30a.

Love these forums...just spent an hour reading about solar! (but couldn't find this answer)
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Old 02-07-2013, 12:53   #2
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Re: 1x300w vs 3x100w

3x100w will give slightly more AHrs in a shadow prone installation, as all boats are. However, the difference is small and is usually overshadowed () by issues such as which is easier to fit, cost etc.

Most 300w panels are high voltage and need a MPPT controller, so make sure this is not the case if you want to use a PWM controller with the single panel.

Finally don't forget delivery costs it can be high (courier companies add a surcharge for glass objects above a certain size) for the larger panel so make sure you check the delivered price when comparing costs as often this is not made clear till you hit the checkout on he website.

If everything else is equal (which it rarely is) everything favours 3x100w especially redundancy.
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Old 02-07-2013, 13:09   #3
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Re: 1x300w vs 3x100w

when I installed my 290W panel a few months ago the big difference was that the 290W panel was about the same price as ONE 100W panel

and it was a lot less trouble to mount 1 big panel instead of 3 smaller ones

My advise is to stop worrying and thinking about things like shade etc., instead decide how many watts you want and then decide based on price and ease of installation.

The subject has come up numerous times (once even by me asking the same question)
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Old 02-07-2013, 13:21   #4
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Re: 1x300w vs 3x100w

Quote:
Originally Posted by Don L View Post
My advise is to stop worrying and thinking about things like shade etc., instead decide how many watts you want and then decide based on price and ease of installation.
I agree this is usually the dominant factor.

Generally 1 large panel is easier to install and smaller than the equivalent multiple panels, but on curved surfaces, or those with obstructions, sometimes multiple panels are easier.
Cost is difficult, solar panel prices are very variable. Larger panels are more commonly used in domestic systems, and economies of scale can bring prices down, but large panels are costly to ship and domestic companies are not interested in sales of one panel. The cost of suitable controller and wiring can also significantly effect the installed price.
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Old 02-07-2013, 13:23   #5
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Re: 1x300w vs 3x100w

If it were me, I would go for the 1x300watt (but many will have different views). Part of my reasoning is that 1 panel will be easier to fit, will take up less space on davits, probably cheaper to deliver, solar panels are pretty reliable and not "prone" to fail, so having "redundancy" in theory is not much of an issue at all. Shade is only a problem with aft davit mounting, when the sails obscure the sun under sail (hence the prudence in having a wind generator as an addition). Your boat (its size and sail config, ie ketch, sloop, could have an effect too).
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Old 02-07-2013, 13:39   #6
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Re: 1x300w vs 3x100w

Quote:
Originally Posted by Don L View Post
when I installed my 290W panel a few months ago the big difference was that the 290W panel was about the same price as ONE 100W panel

and it was a lot less trouble to mount 1 big panel instead of 3 smaller ones

My advise is to stop worrying and thinking about things like shade etc., instead decide how many watts you want and then decide based on price and ease of installation.

The subject has come up numerous times (once even by me asking the same question)
Don, I read the whole thread you started last year asking what everyone's solar setup was. In it you mentioned that you got your 290w panel for $286. Could you tell me where you got it from? I'm set on the amount of watts I need, now is the cost/ease of installation I'm working out. Is your controller a MPPT?

Noelex...I haven't read anywhere about requiring MPPT for larger panels...just that I should make sure I have a controller that can handle the amps. In this case, a ProStar 30a should handle 300w just fine. Could you explains what you mean?

Thanks!
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Old 02-07-2013, 14:02   #7
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Re: 1x300w vs 3x100w

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Originally Posted by mistersmith2017 View Post
Noelex...I haven't read anywhere about requiring MPPT for larger panels...just that I should make sure I have a controller that can handle the amps. In this case, a ProStar 30a should handle 300w just fine. Could you explains what you mean?

Thanks!
PWM controllers will only work (with a 12v battery) with panels that have 36 cells. These panels have a Vmp of around 18v.
There are lots of panels like this. Most (not all) panels below about 130w conform to these specs and have 36cells.

However larger panels are more commonly (not always) higher voltage panels, with more than 36 cells and Vmp in the 30v+ range.
(For the technically minded this is because large solar cells are difficult to make, therefore to increase the wattage in large panels, more, smaller cells are added to the panel. This increases the voltage not the current)
For these panels to work in a 12v system the voltage needs to be converted to lower voltage.

Only MPPT controllers do this.

With 36 cell panels you can use a PWM controller, or a MPPT controller. Higher voltage panels can only use a MPPT controller otherwise the output is very poor(and sometimes the controller is damaged).
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Old 02-07-2013, 14:16   #8
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Re: 1x300w vs 3x100w

Quote:
Originally Posted by mistersmith2017 View Post
Don, I read the whole thread you started last year asking what everyone's solar setup was. In it you mentioned that you got your 290w panel for $286. Could you tell me where you got it from? I'm set on the amount of watts I need, now is the cost/ease of installation I'm working out. Is your controller a MPPT?
I got my panel from Alt-E that are fairly local so that I could go pick the panel at the warehouse (still barely fit in a friends truck). Because I used a 24V (36V for Vmp) yes I used a MPPT controller (Outback Flex 60).

I could have used smaller wires, but used larger ones that could handle a second panel if I later decided to add.

When I was figuring out the costs it worked out that 3 small panel with a PWM controller was about $100 less than the 1 large panel with the MPPT controller. But I'm sure that $100 would have been more than made up by the mounting costs of 3 panels.

So a large panel with a better controller (that has a lot more features of use) is pretty close price wise. But to made it work you need to be able to not have to ship the large panel.
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