String Sizing Help

djohnyvonne
djohnyvonne Registered Users Posts: 17 ✭✭
in Solar Beginners Corner #1
New to solar and need help. I am implementing 2-Outback Radian GS8048A inverter/chargers with Outback Load Centers, 4-Outback FM-80 Charge Controllers, 48-Trojan LRE-2V Flooded Deep Cycle Batteries & a generator. I used Outback string sizing tool but I'm confused on the results. I would like to use 40-ReneSola 300W panels($0.14/watt) but the max power current of the array is 32. My question is, if 32 is the amps, will this be sufficient to keep battery bank charged? Another option I looked into was 48- Silfab 280W panels($0.22/watt) which has max power current of 60. 44-Canadian Solar CS6X-285P panels($0.28/watt) with max power current of 55 is also an option. The Dropbox links below show the results of each panel using the Outback String Sizing Tool.
Any help or suggestions would be greatly appreciated!
Thank You!

https://www.dropbox.com/s/8ypw8i28i5ajq0y/File Jun 17, 8 03 34 PM.jpeg?dl=0

https://www.dropbox.com/s/ngbksi5xc20rrns/File Jun 17, 8 08 26 PM.jpeg?dl=0

https://www.dropbox.com/s/t52z79pxy9ggqeg/File Jun 17, 8 04 26 PM.jpeg?dl=0


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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #2
    Hi djonyvonne,
    The panels listed all appear to be 24 volt 72 cell panels configured 2 in series. These will not produce a PV input voltage high enough to reliably do an equalization charge on flooded lead acid batteries. It would be better to go with a 60 cell panel, also called a grid tie panel. Three of these in series would give you a PV input voltage of about 90 volts.
    This is an example,  
    https://www.solar-electric.com/kyocera-ku265-6mca-265-watt-multicrystal-solar-panel.html

    Recommend you find the brand and price that meets your needs and budget.

    I also have a Radian, they are awesome inverters.

    Rick

    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • djohnyvonne
    djohnyvonne Registered Users Posts: 17 ✭✭
    #3
    Raj174:
    Thanks for the response. Those 72 cell #'s didn't look right to me either, that's why I asked. I think the 275 watt model in the link provided is a good choice at $0.24/watt.

    http://sunelec.com/Silfab 60 Cells.pdf
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    edited June 2017 #4
    I agree, nice choice. Three strings of three panels each should produce about 94 volts 36 amps per controller times 4 controllers. So that is about 315 amps, a little high for the Trojans, however with power losses due to panel heating, that number should be closer to 250 amps which is an 11% to 12% charge rate, which I would consider just about right.  
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • djohnyvonne
    djohnyvonne Registered Users Posts: 17 ✭✭
    #5
    Raj:
    sizing tool came up with this. These calculations don't look right.

    https://www.dropbox.com/s/jvhe137htdv6hts/File Jun 18, 12 17 44 PM.jpeg?dl=0

    https://www.dropbox.com/s/q54n2wyl9tspa24/File Jun 18, 12 17 58 PM.jpeg?dl=0

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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #6
    Sorry, I calculated for four strings of three but stated three strings, my bad. Try the string calculator with  3 x 4 strings.

    Rick
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • djohnyvonne
    djohnyvonne Registered Users Posts: 17 ✭✭
    #7
    Raj:
    what does max power current of array mean?(34)

    https://www.dropbox.com/s/3zl9k0aqz7pfxsm/File Jun 18, 1 14 35 PM.jpeg?dl=0
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    edited June 2017 #8
    This is the current the array is feeding into the charge controller that will be converted to the charge amperage, which in this case would be about 66 amps to the battery. With 4 arrays, one for each controller, that's 266 amps.
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • djohnyvonne
    djohnyvonne Registered Users Posts: 17 ✭✭
    #9
    So...then 3x4 of these panels is the correct configuration? 13,200w approximately?
    thank you so much for your help, I really appreciate it.
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #10
    Yes, it's correct. This is a very large system and could even be a challenge for an experienced solar enthusiast. I hope you have some good local technical help. Good luck and keep us updated on your project. 

    Rick
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • Tmp4000
    Tmp4000 Registered Users Posts: 34 ✭✭
    #11
    Hey @djohnyvonne, maybe we can report on our individual progress ? I too am working on a large solar electrical system...currently in the planning stage. Maybe we can share our trials and tribulations with such large systems ? Best of luck to you!
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  • djohnyvonne
    djohnyvonne Registered Users Posts: 17 ✭✭
    #12
    Again Rick, thank you for your advice. Tmp4000- yes I would enjoy that. SCE cost to bring service to my parcel was quoted at $100,000. Along with that, I had to trench 1000', supply wire & conduit and an underground vault. So the sum of $30,000 for an off-grid system is the logical choice.(plus no monthly bill)
    My email is djohnyvonne@aol.com, or yvonnedeland@gmail.com, or Johndeland@icloud.com. Feel free to write or send pics as you progress.
    Thank you again Rick!
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