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RWinSC
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# Posted: 17 Jan 2011 15:27
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I recently completed my cabin, the bottom foot print is 16x20 with pull down stairs to a 6x20 sleeping loft. I installed all electrical to regular home codes using 12/2 copper with a 100amp panel powered with a line off another house I own near by. I am in the process of converting to solar mainly for lights and maybe a small TV. I have purchased 2 deep cycle Trojan RE Batteries, a 750 watt inverter, and the proper charge controller. Would anyone have any advise on what size wattage solar panels I will need to keep these batteries properly charged. I heat with gas so my main usage will be 3 or 4 lights at night. I am in South Carolina.
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bugs
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# Posted: 17 Jan 2011 15:44
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Hi Robert
If you can use led lights (ie 25 incandescent replacement types) your energy requirements will be reduced dramatically therefore your battery charging requirements and in turn your solar panel size can be reduced. We have a single 130 watt panel and it keeps our two batteries at max charge almost all the time. Charge recovering in the mornings are really fast even under cloudy conditions. Methinks we could probably get by with half the size of solar panel but this set up will allow for expansion in the future if we increase our electrical requirements.
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RWinSC
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# Posted: 17 Jan 2011 16:03
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Tks bugs I have a battery dealer friend that is giving me a good deal on 2 more Trojan RE Batteries so I am thinking 130 watt panel would be just right for all 4. What sort of money should I expect to pay, there seems to be a lot cost variances out there. I had friend refer me to Phono Solar Panels, pretty pricey units but 20 year warranty.
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bugs
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# Posted: 17 Jan 2011 20:47
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Robert, our panel was close to $700 cdn. I suspect they have dropped since we purchased them. We too tried to get the best quality we could reasonably afford (Sharp). I think there is quite a variation in quality available.
It is always a neat experience to try and size everything for your present plus future needs. We were advised to over size the components so upgrades, if required, would be cheaper.
It all comes down to how fast you want/need to charge your batteries versus how much sun exposure your microclimate has and how much battery storage you need. If you stay out at the cabin for 5 days of clouds will you still be able to have lights at night? Or, if you are out for the weekend will the batteries be charged and ready for you on the following weekend. It is a multivariate problem.
We have a couple of ordinary 60 watt light bulbs we use just briefly as spot lights outside. (We don't want to step on the resident skunks on a night time trek to the toilet!!!) It is amazing how much energy they use compared to the led lights.
For entertainment we use a netbook with external disc drive and speakers rather than a tv/dvd setup. Adequate for our needs.
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toofewweekends
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# Posted: 18 Jan 2011 01:14
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RW,
We have a similar size weekend cabin in Alaska. In summer, a pair of 6v golf cart batteries a 90 watt panel, and 300w inverter give us lights(flourescent), dvd player for a little tv, music, and charged cell phones. Microwave, toaster, power tools, etc. require a Honda 2kw. We get enough sun from April to October to keep it pretty well charged, with an occasional boost by the generator. With your bigger batteries (assume more amp hours; at least better quality) and panel, you'll probably do fine. Winter here doesn't have enough sun for the panel to charge much. Tough on batteries, too. SC should be way easier!
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MtnDon
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# Posted: 18 Jan 2011 10:22 - Edited by: MtnDon
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Unless you total up you use you are guessing. You might guess right, you could guess wrong. Find an online solar sizing calculator. There are many. Plug in the use; hours of use, power drawn, etc. One is located HERE. It's a downloadable spreadsheet. I wrote it. It's free.
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bugs
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# Posted: 18 Jan 2011 11:37
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I found the calculators helpful but still they are based on "typical/average". Typical monthly/daily sunlight for region, typical cloud cover, typical usage, and so on. Sizing a setup is still a lot of "guess-ta-mating".
As I see "50" retreating further and further in the rear view mirror I have come to realize typical and average are fleeting terms especially when it comes to weather. And in our cases cabin plans!!! And electrical usage!! In many ways electrical usage is like space. If you are not careful you will use it all and then want more.
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MtnDon
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# Posted: 18 Jan 2011 12:29
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The calculator I wrote requires thinking on the part of the user. Thinking about what their power use will be. Nothing typical or average. The user enters what they honestly believe they will use after thinking through the number of lights, what size, minutes of microwave use, toaster, all that.
As far as sunshine, yes, typical or average; but that does work out over the months/years.
I used it when designing our PV system; that's what prompted me to write it. It worked for me. The only reason I ever run the generator is because it hasn't been run and needs a run for it's health, or if I decide to equalize the batteries and it is a cloudy day. We never run out of power in between.
And in closing, the number one "problem area" with people having issues with their off grid system is lack of sufficient battery storage.
59 is a distant memory for me.
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Robert
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# Posted: 18 Jan 2011 16:10
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Look at the 45 watt panels with mount and regulator,connectors,and a few bulbs. On sale for $149 at harborfreight, if you get a coupon out of hunting magazines.Be sure to get a charge controller.
Also size it to use no more than 50% of the battery AHR or the total of the ganged up battery bank. @ 3 sets for under 5 bills and 135 watts all in all a fair deal.
Costco has 6v deep cycle for about $75 220Ah rated when paired at 12v
Lights and a small TV no problem for a few days of typical use in SC.
even with just 2 45watt panels
robert@thetinybungalow.com
great site you have here
Will join shortly
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Rob_O
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# Posted: 18 Jan 2011 22:43
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Quoting: Robert Walden I installed all electrical to regular home codes using 12/2 copper with a 100amp panel powered with a line off another house I own near by.
If you have grid power on site, why are you going to solar?
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