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Small Cabin Forum / Off-Grid Living / how many solar panels do I need ?
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montanamark
Member
# Posted: 23 May 2011 00:34
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Hello, I am trying to figure out how many solar panels I need to maintain (4) 12v 192 ah batteries for an extended period of time. (over winter) They should recieve atleast 5 hours of good light a day. Any info. would be greatly appreciated.

mrmiji
Member
# Posted: 23 May 2011 09:31 - Edited by: mrmiji
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I think I found this from someone on this site:

http://www.freesunpower.com/solar_simulator.php

This Solar Energy Electric Power System Simulation is representative of a small 4 KiloWatt solar energy system. The solar panel array is eight 100 watt panels or 800 watts total. With a average solar day of 5 hours, 800 watts times 5 hours equals 4000 watts or 4 KiloWatts (4KW). The battery bank capacity is 1000 AmpHours at 12 volts.

cman47c
Member
# Posted: 23 May 2011 13:30
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If you just need to maintain the batteries and there is no load, batteries will normally no load discharge in cold weather at about 20% per month. You would not need alot of solar panel wattage to just maintain the batteries.

montanamark
Member
# Posted: 24 May 2011 02:29
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Hello, and thanks for the info. So all that being said would a 100 watt panel be enough? There would be no load what so ever. The batteries will only be connected to the charge controller and panel.
Thanks Again,

cman47c
Member
# Posted: 24 May 2011 08:15
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100W should be fine. Should give you about 6 A of charging in good sun and at 5 hours of sun per day, approx. 30 A-HR of charge per day. Four batteries at 192 A-Hr equals 768 A-Hr total capacity and with no load discharge at about 20% per month would mean your batteries will lose about 150 A-HR per month. At a 30 A-HR/day charge rate your recharge rate is about 900 A-Hr per month. So 100W panel is more than enough.

Just
Member
# Posted: 24 May 2011 11:20
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In my opinon a 15 watt would be lots

montanamark
Member
# Posted: 24 May 2011 18:48
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Just
Hello, again and thanks for all the great info. I really do appericate it. Anybody have a particular brand they would recommend? I have been looking at SunForce but there are so many.

cman47c
Member
# Posted: 25 May 2011 08:16
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I use 3 of the Sunforce 15W panels at my cabin to keep two 100 A-Hr batteries going. They seem fine with a decent charge controller.

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