Will these panels and batteries do the job?

Kendu
Kendu Registered Users Posts: 2 ✭
in Solar Beginners Corner #1
Hello all. I have the opportunity to buy 20 140w panels at a decent price. I can afford roughly  10 6v 230ah batteries. Will this be enough to run a 5000btu window unit 10 hours a day, and a small refrigerator full time? I'd appreciate any advice before I take the plunge. Thanks. 
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #2
    Welcome to the forum 

    Your questions are open ended because of missing details such as, what nominal voltage is proposed, 10 × 6 volt batteries would indicate 12V nominal with 5 parrallel strings of 2 which in not recommended for a system that large and 10 × 6 volts doesn't work with 24V or 48V.
     
    Location will determine the solar potential so that is important, having accurate consumption figures, particularly for the AC would lessen the chances of dissapointment, the actual figures will depend on room insulation values and ambient outdoor temperatures. Use a power logging device to establish a baseline because this will be extremely useful, use a generator if nessersary, if you have grid power you will never save money using solar, if the grid is very unreliable then it would be comfort at an expense.

    Don't take any plunge until the loads are accurately calculated, you have done the right thing by asking questions, rather than buying equipment first then asking questions, so many fall into this trap, but I will say that air conditioning is very challenging in off-grid applications if that is the goal.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • Kendu
    Kendu Registered Users Posts: 2 ✭
    #3
    Thank you for your reply. Lots of research to do.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #4
    Kendu,

    Don't worry about asking questions here... Give us the information you do have, and what your needs may be, etc.

    One thing I try to avoid here on the forum is telling people that they have to do more research.

    When you are new to this (and we were all newbies at one time or another in our lives), you don't even know what you don't know.

    What works well here is to work through the whole data collection, paper design and reviews, then picking equipment (and another review), before buying anything.

    Solar power is not cheap--And so understanding your power needs (measuring with a Kill-a-Watt or similar meter, and/or getting recommendations from folks here, etc.) is the first step. Conserving power is almost always cheaper vs generating power (i.e., lots of insulation for building/RV, finding a smaller/"solar friendly" A/C system--Typically one that is "inverter based", etc. either a window unit or mini-split) is all part of the process.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • MichaelK
    MichaelK Registered Users Posts: 234 ✭✭✭
    #5
    Let's make some assumptions here, do the math, then make corrections when you have real numbers to plug in.

    You can wire 8 of your batteries in series to make a 48V battery bank.  Lots of companies make very, very good 48V inverters (not 60V).
    230AH X 48V = 11040AV or 11.04kwh
    Assume that you don't want to ever use more than 50% of the battery.
    11.04kwh X .5 =5.52kwh (available)
    Assume that this aircon uses about 600watts and it has a 50% duty cycle (300watts per hour)
    300W X 10hours =1800wh or 1.8kwh
    Assume that the refrigerator uses 1.0kwh/day (see the refrigerator's spec sheet)
    Assume that the inverter needed to power both of these units at the same time will itself consume about 800W of power per day (0.8kwh)
    So, your total load is 1.8kwh+1.0kwh+0.8kwh=3.6kwh
    You'd drain about 3.6kwh/11/04kwh =32.6% of your battery bank per day.

    Now, charging.  If you want to charge your batteries at 1/10 of capacity, or 23amps, you will need...
    23A X 48V X 1.25 efficiency factor= 1380watts of panels.  So, you are OK panel wise.

    In my opinion, the battery bank would be too small.  I would not want to drain my batteries more than about 15% per day, which would give me two cloudy days before reaching the 50% limit.  If you doubled the size of your bank, say using 560AH X 48V, then the numbers look much better.  Rolls makes a nice battery of that capacity.

    Remember though, some of these numbers are guesstimates, and this should only be used as a rough guide.  But, you can fill in the real number once you have better data.  I won't be surprised if the real numbers are higher.
    System 1) 15 Renogy 300w + 4 250W Astronergy panels,  Midnight 200 CC, 8 Trojan L16 bat., Schneider XW6848 NA inverter, AC-Delco 6000w gen.
    System 2) 8 YingLi 250W panels, Midnight 200CC, three 8V Rolls batteries, Schneider Conext 4024 inverter (workshop)
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