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  • Needing advice to configure solar panels

    Hi, I'm new at this and would appreciate some feedback. I have 12 - 320 watt, 37.8 volt, 8.52 amp solar panels. 1 - 24 volt 1379 amp @20 hr. battery. 2 - midnite classic 150 mppt charge controllers. The distance from the solar panels to the charge controllers will be approximately 15'-20'. My question is, what will be the best way to wire the solar panels- 6 in parallel going to one controller, then having 2 strings running to separate charge controllers, or 2 in series with 6 pairs in parallel = 12 panels going to 1 controller. I plan to water 280 cattle with this system by running 2 - 24volt piston pumps on two shallow wells, the wells are 20' deep. the pumps will run approx. 5 hrs. a day each. the motors are 13.5 amps, 24 volts. Will I have enough battery to run an inverter (in addition to the pumps) to power led lights in two calving barns. There is 11 lights at 9 watts of power each. If the battery will run an inverter what size and type is recommended. Looking forward to some advice. Thanks, Dave

  • #2
    ok
    a 24V system and 3840 nameplate watts (3072w actual - 80% of nameplate) watts of panel.
    So, rounding to 6 panels, 1500w per controller @ 24V = 62.5 amps, reasonable.
    The best efficiency for the controllers is going to be 2 panels in series (76V), and then 3 of those strings in parallel to each controller.
    That will require 6, ~10A ** circuit breakers (3 per controller) for the PV side, and you would ideally add another ~70A breaker at the battery side of each controller.
    I'd wire the output of each combiner to it's controller with #8 or preferably #6 wire, and #2 wire from controller to battery. Size the wire to reduce loss, but be sure the breaker would pop before the wire melts. The Classics do not have remote voltage sense, so voltage drop from controller to battery becomes critical.

    Now the battery, I sure hope you don't have 12 batteries clamped in parallel with jumper cables !!
    1300Ah would like to see 130A of available charge current, which your arrays can manage (if the weather allows)

    Inverter - Any 300W-500w 24V sinewave inverter would power the lights and any rechargeable gadget you have.

    Big Problem will be load control. Large, professional controllers do not have "load control" so in a couple cloudy days, the pumps could bleed the batteries down completely and ruin the batteries. So you need to get a Low Voltage Disconnect configured to not burn up from the pumps, and shut them down when the batteries get low.
    I'd also rig a timer up so they only pump daylight hours

    I'd also like to see a 3Kw generator and battery charger (50A @ 24V) for the cloudy days to keep the batteries up when the sun can't.

    ** Back of the panel, will be a spec for Series Fuse, likely 10 - 12 amp rating,
    Midnight Solar distributes genuine DC rated breakers and some nice utility boxes to mount them in, for the combiners and controllers breakers.
    Blue Seas makes a great battery terminal, dual fuse (MRBF)
    https://www.bluesea.com/products/215...k_-_30_to_300A

    MRBF blue sea fuse block.png
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

    Comment


    • Dave Geib
      Dave Geib commented
      Editing a comment
      Thanks Mike for all the information. I've read it and reread it so I wouldn't miss some advice. The battery is a GB Industrial Battery made up of 12 - 2 volt cells, it weighs a little over 1700#s and is 1379amps @ 20 Hrs. One question, (probably will be more later) wiring 2 panels in series then 3 sets of those in parallel will produce 25.56 amps, is that correct? If that's correct then that means there will be on a sunny day approx. 50 amps charging the battery. Is that enough? Dave

  • #3
    Well, with only the 12 panels / 2 controllers, you will have up to 120A @ 24VDC to charge the 1400ah batteries with, (on the best perfect day)
    So, rounding to 6 panels, 1500w per controller @ 24V = 62.5 amps, reasonable.
    With the large 2v batteries, Electrolyte Stratification can be an issue and that is dealt with by sufficient charge amps to bubble (gas bubbles, not heat boiling) . You are a bit light on enough amps (you need 10% of battery rating to begin to accomplish this).
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

    Comment

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