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darrylgood
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# Posted: 1 Jan 2013 20:30
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Hello Everyone.
I am setting up an off grid system for our cottage. I have sized it out and have determined that we can live comfortably with 800 watts (3 - 265 watt panels) I have purchased only the panels so far and have a couple questions as I'm just a solar amateur at this point in time 
Does anyone know of a website/link/forum that has directions in setting up a system such as mine?
I believe I should be doing a 24 volt system, is this correct? What is the advantage, what is different from a 12 volt system?
Is a 1600 watt inverter large enough or should I go for the 2500?
How do I determine the charge controller size?
How should my battery's be wired?
Any info would help
Thanks so much everyone!
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Borrego
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# Posted: 1 Jan 2013 21:41
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Stand by, the experts will be here momentarily  they've been a big help to me... Say, what kind of panels did you get and why. I'm just about to start my system and have been having the same questions....
You can also do a search, there will be lots of threads out there to get you started..
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darrylgood
Member
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# Posted: 1 Jan 2013 22:06
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Thanks borrego,
I have been looking for info online, there is almost to much info and I think that's what my issue is, I don't know enough about the subject to deceifer through it all. I am hoping one of the pros here can lead me on a straighter path
The panels I have are multi crystalline
Thanks
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Rob_O
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# Posted: 1 Jan 2013 22:26
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Quoting: darrylgood I believe I should be doing a 24 volt system, is this correct?
Do you have 24V panels? What is the Vmp for the panels? There should be a sticker on the panels that has the info.
Quoting: darrylgood Is a 1600 watt inverter large enough or should I go for the 2500?
What is the maximum load are you running? You won't need (or want) a huge inverter idling to run one light bulb
Quoting: darrylgood How do I determine the charge controller size? How should my battery's be wired?
Depends on what voltage you go with
Quoting: darrylgood I have sized it out and have determined that we can live comfortably with 800 watts
Can you give us a little info on how you calculated this number?
I hate to answer all your questions with more questions but there's no such thing as a "800 watt" system that fits everyones needs. Fill in a few blanks for us and we'll be happy to help
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darz5150
Member
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# Posted: 1 Jan 2013 22:38
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you should check out freesunpower.com, they have a lot of info you might need, like wiring sizes and different diagrams etc. Also look in this forum in the off grid section. There are links posted for calculating your power consumption needs (appliances etc.)
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darrylgood
Member
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# Posted: 2 Jan 2013 14:39
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Hi guys thanks for the response, here is some info
The max vmp says 35v
The only large thing that will be run in the cottage is a small 10 cubic feet fridge, a couple lights, no tv/microwave, just small stuff - radio, maybe laptop ect...
I have used an online calculator to determine that i need around 1500 - 2000 watt hours per day.
Hope this helps
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Dillio187
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# Posted: 2 Jan 2013 16:11 - Edited by: Dillio187
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*edit*
nevermind, I see you are already on the case. Happy reading
http://www.wind-sun.com/ForumVB/forum.php
awesome forum with all the information you could ever need.
FWIW, you need to measure the draw of everything you want to run. Refrigerators can vary greatly model to model. You will also want a generator backup if running a 'fridge. Refrigerators require a large surge on compressor start, so you will need a much larger inverter just for that than anything else. Good luck.
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Moving Pictures
Member
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# Posted: 2 Jan 2013 18:01
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Quoting: darrylgood I have used an online calculator to determine that i need around 1500 - 2000 watt hours per day.
You may want to re-evaluate. Most of what I've learned says you need to plan for five days without solar power, so you're looking at a 10,000 watt/hour reserve capacity. Breaking that down to a 24-volt system, you're looking at 416 amp-hours, but that's for running the battery right down to nothing (not good). To be at 50 per cent after draining that much, you're looking at more than 800 amp-hours at 24 volts - and are likely looking at a set of 2v 1000-a/hr rolls-surrettes - at $400 per pop.
Now to charge those, you need to be able to generate as close to 1/10 the total capacity as you can - 100 amps. The closest you can get is a Midnite 150, which will push 96 amps into the system. To pull 96 amps into the system, you're looking at about 12 solar modules.
At least, that's my read of it.
Seems to me you may want to get a better handle on your power consumption?
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darrylgood
Member
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# Posted: 2 Jan 2013 20:20
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Thanks Moving Pictures, we might even decide to keep our old propane fridge, so I do believe that the 800 watt system will be enough for our uses.
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darrylgood
Member
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# Posted: 2 Jan 2013 20:20
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Can some one please give me a beginners rundown on amps watts and volts and how they all work into the equation. I am starting to get confused
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Moving Pictures
Member
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# Posted: 2 Jan 2013 20:45
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Quoting: darrylgood Thanks Moving Pictures, we might even decide to keep our old propane fridge, so I do believe that the 800 watt system will be enough for our uses.
Either you're wrong on your energy consumption, or you're mistaken on how much power an 800-watt grid will produce.
I have a 480 watt grid, right now, and with it - in winter - I'm generating maybe 600-800 watt-hours of power, per day. Now, it's a temporary system, not in a prime location. However, even if it were in a better location (or, moreover, when February comes and the sun arcs above the pines on the south of our land) the system would generate maybe a kilowatt/hour per day. Based on the principles of insolation, and moreover, the fact there will be no sun for five-day periods, the most I can discharge my 380-amp-hour, 12volt battery bank to is halfway, or 2.280 kilowatts over a five day period. That means that if this were an isolated system, I'd only be able to safely power about 450 watt/hours per day.
You have 800 watts of panels. If you live in the same climate as I do, you're looking at a maximum of 900 watt/hours used per day before you risk your battery pack, which would have to be twice as robust as mine.
Even if I had your panels - twice the input - I'd still only be able to run 450 watts/day, as the limitation is the battery.
Unless you live in an uber-sunny location, you're either over-estimating the power output of your panels for your needs, or you've over-estimated the energy consumption. Grab a kill-o-watt, and take a careful reading of your energy consumption first.
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creeky
Member
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# Posted: 13 Jan 2013 22:30
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I'm going to chime in here
Darryl
start with "wav". watts=amps x voltage.
You want a 24v battery bank. Partly so you can add more panels at some point. 800 amp hours at 24 volts (19,200 watts) should run a small fridge and some lights etc. At least in the mostly sunny months. So that's 8 400 amp hr 6 volt batteries. There are some excellent battery sites. They'll have good diagrams for how to wire your battery set. Go big on the batteries. You can't add more later if you decide you need a bigger system. It's an all at once purchase. There are lots of good heavy duty battery manufacturers. Crown, Surette, Rolls ...
but most of the people with smaller solar systems that are happy with their systems that I've seen have 1 watt solar for 1 amp storage (at 12v). You'll have 1 watt to 2 amps, but room to expand your solar input ...
During the summer my kilowatt of panels averages 4 kw production per day. More than I need. Remember. You only need to replace the power in your batteries that you use at night. Once you're recharged you can run whatever. I generated 6 kws solar production one summer day. After my batteries were charged I ran an air conditioner ... just to see if I could.
However, where I live it's winter now and a rather cloudy one. I'm averaging less than a kilowatt a day. Last week was less than 500 watts per day and one day I had 0 watts generated. I was away and a snowstorm covered my panels. Plan on a generator if you expect long periods of cloudy weather. It seems Diesel is cheapest over the long run. (or pull the plug on the fridge ...)
You need an mppt solar controller: with your current 800 watts get a minimum 45 amp charger - 45x24=1000 watts input or roughly equivalent to your 800. If you get a larger controller (say 60 amps) you will be able to add more panels at a later date. Basically 3 more panels...
I'm going to 1.5 kws of panels even though I have a 60 amp controller with a 12 volt battery bank @ 1200 amp hrs (so 60x12=a theoretical 720 watt solar panel system.). However, the sun don't shine super bright or long during the winter, there is cloud, snow, fog, tree shadowing, ice on the panels etc. I'd rather get 300 watts in the early a.m./late p.m. from my 1.5 kw of panel than 200 from my 1 kw system. With 5.5 hrs of sun these days I need every watt I can manage.
A larger inverter draws more idle power. But with a fridge on your list. Get a bigger inverter. The fridge manual should say what your "surge" requirement is.
So that's the basics. Now you just need wire, combiners, fuses, grounding, rack mounts, auxiliary charger ... it's a great trip. enjoy!
PS-for more technical info on solar systems I also like the wind-sun site recommended earlier.
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