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I already have 4 GC batteries that are only about 2-3 years old have only been used sparingly so that should help my cost/benefit analysis. Although I also already have a PSW 12V volt inverter, it appears that I need to run this system at 24V as you and others have stated, so I'm guessing I can pick up a low priced MSW 24V inverter.
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While those panels were free they really aren't enough wattage to run a load like a refrigerator. That means you will have to add more panels along with batteries, charge controller and possibly an inverter. Ultimately you will end up spending a lot more to run the frig then just using the grid power.
IMO I would look into finding some other small load for the free panels. You will get some hands on solar experience but not break the bank while you learn.Comment
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now you need to get an AC 110 volt watt meter, and do a log of the power and cycle length of the appliance running from grid power. So you can have base line of whatt hours needed, you may also notice less proformance, especially refrigeration. If unit cycles for 12 min's an hour on grid, it could very well take a 20 min cycle running from inverter, this gets worse at 12 volts.Comment
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Sun Eagle, I may have an answer to your recommendation that I find a smaller load. My neighbor has a nice, but sorta old, glass greenhouse that she has offered to sell me. That might be the perfect solution for my "free" panels because all I would probably need to run is a light bulb, vent fan and a small pump to run my aquaponics tank setup. Still don't have my RV back, but it's getting closer. I'm feeling the Karma here guys. This seems to be falling into place. Stay tuned.Comment
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a light and or aquaponics would need a battery, no need for a light during the day and aquaponics needs 24X7 run time. However if you dedicate solar to irrigation and ventilation, you could possibly run w/o a battery, by only running these loads during daylight hours.Comment
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Indeed even a small buffer battery makes more things possible, If he plans to run any aquaponics or grow lamp, is going to require many hundreds times a small buffer battery. I would use a 100+ ah FLA battery and a good quality LVD low voltage disconnect set to 12.0 volts. the less of a load you run the longer the runtime. use a timer to run larger loads during daylight hours and smaller loads at night when running on battery. there must be a thousand plus variablesComment
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As I have previously written, I have four 6V GC batts already in my RV that I will be removing before I sell it. I don't plan on a glow light (like I had when I had the tank in my shop) because I will have sunlight. The only light I might put in it would be a small light to be used only if needed on dark days or maybe in the event I have to go in the greenhouse at night. The main thing I'll have to run is the110V pump which is rated at 20W (.3 amps) and maybe a vent fan that I would set up on a thermostat where it might kick in on extremely hot days. Anyway, my two "free" panels are rated at 280W each. With those new facts, would my two panels be enough to keep my batts charged adequately to run the pump with some left over for the fan if needed sporadically?Comment
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replace the pump with an equivalent DC pump and replace the fan with a native DC fan motor and yes it could be done, but not advisable with a 24X7 inverter. If all runs are short there is few good reasons to run an inverter on this type of set up.Comment
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Payback? What payback?
Anything you take off-grid and put on batteries will cost you 5 to 10 times more than buying he power from the POCO. A set of batteries that will deliver you 1 Kwh of usable energy in a day is going to cost you 800 to $1200 today. In 3 to 5 years you will replace those batteries at even a higher cost. Your POCO charges you roughly 10-cents per Kwh. So if you use 1 Kwh per day is 10-cents worth of electricity. A good 3-year battery will cost you $800. and at 3 years gives you 1100 Kwh of power in 3 years when they need replaced. That means you paid 1100 Kwh / $800 = $0.73 per Kwh or 730% more than you could have just bought the power for 10-cents per Kwh.
Don't be delusional, there is no such thing as a Payback with a battery system. It is a voluntary 500 to 1000% rate increase you impose on yourself. Will make your battery dealer really happy, and the POCO will never miss it. You are the only onme getting screwed and you did it all by yourself.
So much for free panels.MSEE, PEComment
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WOW! Sorry if I got your panties in a wad Sunking. Perhaps it might help if I try to re-explain what I'm trying to do: I have two free solar panels, 280W each. I also have four 6V GC batteries that are just sitting in my RV unused. I also have a Zantrex PSW 12V inverter in the camper that is also unused presently. The camper will soon be sold/traded/given away and there is no need to let these items go to waste. I originally purchased these items so that I could "dry camp" on a trip out West and on future camping trips, but things change, including my wife's health so that plan is no longer functional.
So, second bite at the apple: My original intent was to build a small system to see if it would be feasible to utilize these items to run my freezer and/or fridge that I have in my shop, but with the advice of many on this forum, I have about given up on that idea because it appears that I would need more panels and possibly more batts. Now, as far as "payback", which you so trivialized, at that point when I mentioned that, it appeared that I might have to buy an "expensive" MPPT controller rather than be able to utilize a cheapo PWM controller and that the inverter might have to be replaced with one that will operate at 48V. (I'm not convinced of that yet, but all of you on this forum certainly know more than me about solar so I'm assuming your advice is correct.) So as to "payback", I was talking about the cost of those additional items that I don't already have that I would consider having to shell out some $$$ for. Based on your calculations, even that concept seems to be wrong so I'll accept that and give up on any "payback".
So now, what am I left with? the opportunity to build and gain some knowledge about solar and possibly utilize some items I already own to go "off grid" in a small way to see if I can get a self-sustaining system working. Self sustaining has intrigued me since I built my small aquaponics system where I caught some small perch, put then in a tank and used their waste to nurture some plants, but because I couldn't get the plants to bear fruit due to the lack of sunlight (and the glow lamps apparently didn't compensate), the experiment ended up with some grown perch that provided a couple of fish fries and plants that Okay, now it's a hobby not a money saving idea, I accept that. So with that in mind, any advice you and others can continue to give me will be very much appreciated to make this work.Comment
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And to Sun Eagle, I think you understand better what I'm trying to do and thanks for patiently assisting me.Comment
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No problem. While I agree with Sunking that going with batteries is a waste of money, I can at least help people make good decisions if they have already made up their minds about going in that direction. Then at least I can maybe minimize the pain and the cost as well as let them have some fun and learn something about solar. Then you maybe help others think before they spend anything.Comment
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You will never get a return/payback on a battery solar set up. this gets worse if panels are not angled correctly, if Load exceeds ability of solar to recover batteries. with your 1 to every 3 years battery replacement, your system will be doomed to cost 4 to 10 times more per Kilo watt hour for as long as your run the cyclical battery set up. This is current fact of any common solar battery systems tested. Until a new battery chemistry proves to achieve More cycles, deeper cycles and longer life this is the truth you wish not to hear.
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