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Old 11-15-2020, 05:03 PM   #1
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Solar Calculators

In another post that was the classified section, a user posted questions about solar sizing. I didn't want to bury the answer there, so I made this post.
I put together a couple of solar calculators that are based off of solar insolation tables for the States and Canada. This will basically provide you data on available light for your location and time of year. All the data is based on the panels being flat. The tables was created from data in the Solar Electricity Handbook , I encourage you to purchase the book or look at their calculators.

These calculators were developed in google sheets and should be available here https://docs.google.com/spreadsheets...it?usp=sharing
I created two calculators, one will take your panel size and location and provide available amp hours provided from that panel at various months of the year.

The second will take an expected daily amp hour usage and provide data for the size of your solar bank size, again based on location and time of year.

These don't take into account any loss because of shading, conversion, etc. This should be a good starting point. I will probably add more features as needed, certainly would be open to request.

I will probably also create a amp hour per day calculator in the near future.

please provide any feedback, especially errors, it should be public, so let me know if you have issues accessing.

-greg
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Old 11-19-2020, 11:47 AM   #2
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Hi Greg, thanks for posting. I accessed this on my IPad but am unable to manipulate any data. I assume I should be able to put in my state in place of Kansas, for example? From the lower chart, it does look like my 200W of solar panels will be most efficient from March to September here.
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Old 11-19-2020, 01:04 PM   #3
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i will look into it. I need to dig up one of my old bogus accounts. I did't think I left anything protected.

-greg
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Old 11-19-2020, 01:21 PM   #4
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Quote:
Originally Posted by Otter View Post
Hi Greg, thanks for posting. I accessed this on my IPad but am unable to manipulate any data. I assume I should be able to put in my state in place of Kansas, for example? From the lower chart, it does look like my 200W of solar panels will be most efficient from March to September here.
.
My bad, try this link instead, it should give you edit capabilities
https://docs.google.com/spreadsheets...it?usp=sharing

-greg
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Old 11-19-2020, 03:00 PM   #5
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My bad, try this link instead, it should give you edit capabilities
https://docs.google.com/spreadsheets...it?usp=sharing

-greg
Obviously I screwed the pooch, with the first link for the calculator. It should have editable choices.


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Old 11-28-2020, 05:37 PM   #6
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Hi Greg, this is terrific information, and answers an issue for me... and at the same time brings up a question.

I have a rooftop-mounted 200-watt Renogy system, which includes 2 6-volt 200 amp-hour AGM house batteries in series (resulting in 12-volt 200 amp-hours of battery), a Xantrex 2000 watt inverter/charger, and a Renogy MPPT CTRL-CMD20 (20 amp) solar charge controller.

I am discovering that in the winter this system cannot keep up with a Dometic DFX65 fridge/freezer when parked in full sun all day long. No worries in the summer, when I can use my microwave for maybe 10-15 minutes a day (and the lights, the fan, the computer, etc.), even if I need to run the van for a half-hour now and then.

So, I'm thinking that perhaps for the winter I need a supplementary source of energy, such as a "suitcase" set of solar panels, which would be "aim-able", and my question is, do I get one with its own controller and hook it directly to the house battery, or do I get one without a controller and hook it up (somehow) to the exiting controller?

I've searched the archives and can't seem to find any previously posted information about doing such a thing.
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Old 11-28-2020, 06:37 PM   #7
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These will offer you some insight to options which members have shared on their various methods of connecting suitcase panels to the current solar system:
https://www.sportsmobileforum.com/fo...lar-26453.html

https://www.sportsmobileforum.com/fo...tml#post275598

https://www.sportsmobileforum.com/fo...ler-25863.html

https://www.sportsmobileforum.com/fo...ing-25646.html

https://www.sportsmobileforum.com/fo...zon-16850.html
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Old 11-28-2020, 07:50 PM   #8
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So, I'm thinking that perhaps for the winter I need a supplementary source of energy, such as a "suitcase" set of solar panels, which would be "aim-able", and my question is, do I get one with its own controller and hook it directly to the house battery, or do I get one without a controller and hook it up (somehow) to the exiting controller?

I've searched the archives and can't seem to find any previously posted information about doing such a thing.
If it was me I would update the solar controller to minimal 30 amp and install an aux output in parallel with the existing 200 watts you have. I assume that those are in parallel with each other. You would want to make sure that voltage output of suitcase is as close as possible to the existing panels you have. That way you can leverage just one controller. You could get away with the 20 amp controller in many cases, but I couldn't actually recommend you to do that. A lot would depend on the specs of the controller.

This was my write up of adding an aux outlet https://www.sportsmobileforum.com/fo...els-23929.html


-greg
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Old 11-29-2020, 12:12 PM   #9
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Another idea is get a second controller that is identical to and programmed the same as your current one, since you might be buying one anyway.
Essentially you would have two separate systems that both feed your batteries.
The benefits would be if the roof panels were shaded they would not drag down the power of the portable panels.
If there were voltage differences between the 2 kinds of panels 2 controllers would keep the lower voltage panels from dragging down the other panels.
If you decide to sell the van but want to keep the portable panels, just remove the new controller and the van sysem is still intact.
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Old 11-29-2020, 10:59 PM   #10
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...You could get away with the 20 amp controller in many cases, but I couldn't actually recommend you to do that. A lot would depend on the specs of the controller.

-greg
Well, each of the (2) 100-watt Renogy panels on the top of the van have an Optimum Operating Current (Imp) of 5.70 amps, and the 100-watt Renogy suitcase array that I would buy has a Maximum Operating Current (Imp) of 5.56A, and together these add up to less than 20 amps, which is the rating of the Renogy CMD 20 controller.

Below are the specs of the controller itself...

Model CMD-20
Nominal system voltage 12V/24V Auto Recognition
Rated Battery Current 20A
Rated Load Current 20A
Max. PV Input Short Current 25A
Max. Battery Voltage 32V
Max Solar Input Voltage 150 VDC
Max. Solar Input Power 12V @ 260W
Self-Consumption ≤50mA @ 12V
Charge circuit voltage drop ≤ 0.26V
Discharge circuit voltage drop ≤ 0.15V
Temp. Compensation -5mV/°C/2V (default)


Would you still recommend an upgrade to a 30 amp controller, or would this one do?

On the other hand, what is the downside to just buying a 100-watt suitcase array with its own controller and hooking it up directly to the battery array independently of the rooftop system, as was suggested by another responder?

I'm looking at cost here, too, and the suitcase system with a controller is about the same price as the Renogy 30 amp controller alone

I really appreciate your input.

\Paul
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