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Old 09-04-2014, 05:32 PM
LastO LastO is offline
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Default Solar wiring question

I'm new here and have searched for this info but haven't found it if it is here already.
I recently purchased a small cabin in an off grid area of SE Oklahoma. We have been working on it trying to get it livable so at some point in the near future we can move in there to live full time.
A/C is a gotta have in our area due to the summer heat getting to the 100 degree F. area for a number of months.
Right now I have a 6 battery bank of 110 AmpHour rated 12volt batteries and a cheap 200 watt inverter.
it seems to run the single window mount a/c unit fine and recharges in a few hours from a Generator.
I am ready to work into some panels. I'm looking at three 300w - 24 volt panels.
My area that gets good sunlight for a number of hours is about 50 ft from my cabin front door and another 50 ft from there to the back of the cabin where the battery bank might be located.

So, 100 ft from Battery bank to panels.

Im guessing that i would need to run AWG 4 or larger wire to transport 24 volt power from panels to battery bank and inverter.

Would I be better off to build an enclosure near the panels and run a short awg 4 wire from the panels to the inverter and bank, convert to 110 volts and then use regular house wiring to transport the power the 50 to 100 ft to the cabin? Or Use awg 4 to transport the 24 volt power the 50 to 100 ft to the battery bank inside the back of the cabin?

Would the voltage drop be less using house wiring to transport 110 volt power or the less using the awg 4 wire from the panels into the cabin then convert to 110 volts?
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  #2  
Old 09-04-2014, 09:33 PM
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Bearfootfarm Male Bearfootfarm is offline
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Welcome to the asylum!

I'm just guessing, but I think it's better to convert to AC closer to the panels, but for a definative answer, search here:

http://www.builditsolar.com/

http://www.builditsolar.com/Referenc...sisrs.htm#wire
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Old 09-04-2014, 11:26 PM
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12vman Male 12vman is offline
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First off.. Welcome to the mix!

To save a lot in wiring, you could connect your panels in series and use a MPPT type controller. The voltage from the panels could be near 100 volts, which would require smaller wire with less losses. This explains it pretty well. Thanks Wind-Sun..

http://www.solar-electric.com/mppt-s...ntrollers.html

Your battery should be in a climate controlled area. They don't work so well if you allow them to get cold..

Check out the line loss chart for 120 volts. Your panels connected in series may produce somewhere around 12 amps. I don't know your exact panels to judge the series voltage. Again, Thanks Wind-Sun..

http://www.solar-electric.com/wire-loss-tables.html

10 Ga. wire @ 15 amps would be good for 131 feet if the combined voltage of your panels is near 120 volts..
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Last edited by 12vman; 09-04-2014 at 11:37 PM. Reason: To Add..
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Old 12-19-2014, 10:11 AM
Mitch Male Mitch is offline
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Inverters are very lossy. But then so are long DC cable runs. You really get to choose where you want the loss That inverter might loose 20% or more of you power just to convert it to AC. A 200 foot cable run on DC might eat up more than that.

There is a 3rd option if there are no children around and you got a handle on electricity. You can build an oscillator to convert that smoothe DC to high frequency pulsed DC and up convert through a transformer such as a microwave transformer. This allows long runs with little loss on much smaller cable. Then you have to reverse the process at the house end. I have used this up in the mountains on 400 foot runs using cheap 14 guage 450 ohm ladder line. In one case we just used 2 Ford coils out of old pickups, but all he wanted was lights and a radio and a small 6 inch TV at his hunting cabin. Everything else was done with propane.

Works like a charm but very dangerous if you get into it! 10,000 volts is no joke even at low amperage! For an electrical engineer or an old ham it ain't no step for a stepper, but the average homeowner, the bad outweighs the good.

Your electric company uses a similar system all the time. Those "pole pig" transformers downconvert 4160 volts to house current 24/7s.
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