Do I Have Enough Solar For My Battery?

I acquired 4, 100W 12V solar panels, parallel, producing 5A each, 21 volts each with a 40A MPPT controller. Is this enough to fully charge a 200AH, or a 250AH, or a 300AH 12 volt AGM battery without sulfation concerns, given the usual 5 hours of average good sun light each day? I need to know before I buy a new battery so I don't waste money on more than I can properly charge yet get as much storage as I can.
Thanks
Comments
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.
Please note that use is at the battery, so you need to take into account energy used in your inverter and it's idle use.
- 60 AH * 12 volts = 720 WH per day of 12 VDC energy
- 720 WH per day * 1/12 volt battery * 2 days of storage * 1/0.50 max discharge planned (longer battery life) = 240 AH @ 12 volts suggested minimum battery size
Standard "golf cart" batteries are around 6 volts @ 220 or so AH--So 2x GC batteries in series would be a 12 volt @ 220 AH battery bank... Probably close enough to 240 AH for now.Two calculations for solar panels... One based on size of battery bank and 5% to 13% rate of charge. 5% can work for weekend/sunny weather usage. 10%+ suggested for full time daily off grid usage:
- 220 AH * 14.5 voltage charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 207 Watt array minimum
- 220 AH * 14.5 voltage charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 414 Watt array nominal
- 220 AH * 14.5 voltage charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 539 Watt array "typical" cost effective maximum
And there is sizing the array based on hours of sun per day (your location/mounting details) and your loads. Say you are around Chesterfield Missouri, fixed array facing south:http://www.solarelectricityhandbook.com/solar-irradiance.html
Chesterfield
Measured in kWh/m2/day onto a solar panel set at a 51° angle from vertical:Average Solar Insolation figures
(For best year-round performance)
- 720 WH per day * 1/0.61 DC system efficiency * 1/3.73 hours of sun per day (average February) = 316 Watt array "break even" February
Your 4x 100 Watt panels is not a bad fit (assuming I guessed your nearest city)... You can estimate the average harvest by month from teh above data... For February:- 400 Watt array * 0.61 end to end DC system eff * 3.73 hours of sun per day (Feb) = 910 WH per day
That is not bad give your 60 AH @ 12 volts or 720 WH per day. And 2x 6 volt @ 220 AH golf cart batteries will be a good start (relatively cheap and rugged batteries. If you get Flooded Cell Lead Acid batteries, you can use a hydrometer to measure the State of Charge, and add distilled water when needed.AGM batteries will be fine too... Just monitor the charging/loaded battery bus voltage to ensure all is going OK (batteries get fully charge several times a week, and don't get discharged below ~12.0 or 11.5 volts under heavy loads).
The above calculations are relatively conservative and intended for an off grid cabin or other usage that needs relatively reliable power. It is a "balanced" system design (battery banked sized to loads, solar array sized to battery bank and hours of sun per day).
One thing you did not mention is what the peak current/power will be... More or less, ideally a C/20 Discharge rate is optimal. C/8 max continuous. C/5 max for an hour or two, and C/2.5 maximum surge current (numbers are for Flooded Cell, AGM batteries can discharge faster/surge more current--But the C/X numbers given should keep the AGM or FLA Batteries happy:
- 220 AH * C/20 = 11 Amp discharge (say 11 amps for 5 hours a night, for 2 nights to 50% discharge)
- 220 AH * C/8 = 27.5 Amps for 8 hours (really a bit less) until battery bank is dead (taking bank "dead" is not good--Batteries will not last long)
- 220 AH * C/5 = 44 Am;s for an hour or few hours (5 hours to "dead").. Heavy draw for shorter time frames
- 220 AH * C/2.5 = 88 Amps for a few seconds to a few minutes (starting surge for well pump, refrigerator compressor, etc.).
-BillSecond 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.
Remember there can't be any shading 9am to 3pm for what you are doing. NEVER
Also keep in mind there are 2 kinds of people, those who want solar, and those who want more!
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I.e., ~220 AH +/- 22 AH -- Not really different from 220 AH itself.
And as the folks above said--Almost any shade on a panel/array will cut harvest by 50% to 100%.
If you have shading, look at what it takes to get rid of the shade (move panels, move roof vent pipes, cut trees, etc.). If you have things you cannot move (nearby house, AC power lines overhead, etc.)--Solar electric may not a good fit...
-Bill