Need help with system

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System
System Posts: 2,511 admin
in Solar Beginners Corner #1
I want to make my sugar house solar and I don't know what I need. This is my plan, 2 125 watt panels, charge controller, inverter, 4 deep cycle batteries. My panels will be about 30' from the battery bank, what size wire do I need for that? The place is wired for elec. for generater. Is that 12 good enough for the system? I will be useing about 300 watts(lights) for about 8 hours a day. The battries are cheap golf cart batteries I don't know the amp hour of them I am in zip 13687 in NY. Any help would be great thanks
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,448 admin
    #2
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    Re: Need help with system

    Right up front--I will say that, the system you asked about, is very poor candidate for solar PV power...

    First, the amount of power. 300 watts of lighting x 8 hours a day would be:
    • 300 watts * 8 hours = 2,400 Watt*Hours = 2.4 kWHrs per day
    Using the PV Watts Website for Massena NY, and assuming that your cooking around February through April--that is about 4-5 hours of full sun per day...

    Assuming 0.52 overall system derating (solar panels, charge controller, battery efficiency, inverter efficiency) and 4 hours of sun minimum, for 2,400 WH of lighting, you would need:
    • 2,400 WH * 1/4 hours of sun * 1/0.52 = 1,154 Watts Minimum of Solar Panels
    If you do not need to use solar power for at least 9 months of the year--It is very difficult to justify a few months of use per year for the panels, charge controller, and battery bank.

    If you can reduce you power usage (switch to florescent/CFL lighting), etc.--you may be able to install a much smaller system.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
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    Re: Need help with system

    welcome and first let me say that your batteries if in a 12v configuration (2x2) will probably be at least 440ah. generally you'd want the charge rate to be between 5% and 13%. with at least 5%. that means at least 22a for bulk charging. the pvs will give about 14.25a and is good for up to about 3.2%. this might be ok to lengthen the time before needing to charge via a generator or better yet to top off the batteries so solar will not play a major roll here as you've laid it out. to reach the minimum bulk charge area at least one more pv should be used for 3 pvs minimally.
    the loads you list are also far more than those pvs could handle so this means the generator would still be the primary source of charge. of course it would need a quality multistage battery charger to go from the generator's 120vac to the 12v needed by the batteries. at least the batteries will make it possible to not hear the generator in the middle of the night.
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  • stevend
    stevend Solar Expert Posts: 34 ✭
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    Re: Need help with system

    Your charge controller will be close to the batteries, so the 30' run will be from your solar panels to the charge controller. The long 30' run from the solar panels to charge controller will be a thinner wire than the short run from charge controller to batteries.

    We'd need to know exactly which solar panel to know exactly which wire size for the 30' run. Using a Kyocera KC125G selected at random, short circuit current is 8 amps. Connecting two in series is 10 amps (8 + 25%) and 24 volts. So a 14 AWG wire will handle the current but the voltage drop would be too much. A 8 AWG will give you 1.6% voltage drop. You'd need a charge controller that takes 24 volts input and since your battery bank will probably be 12 volts, it'd need to do 12 volt output.
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  • System2
    System2 Posts: 6,290 admin
    #5
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    Re: Need help with system

    Thanks to all for the help. Well from what I see so far, it will be cheaper to buy 2 good honda generaters. I would only use the system about 2 weeks a year. So thanks again.
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