Midnight Classic / wiring different panels questions

JimNAZ
JimNAZ Registered Users Posts: 26 ✭✭
in Solar Beginners Corner #1
hello,
I have a midnight Classic solar controller with 1000 watts of high voltage panels. To the best of my knowledge this controller can handle up to 2000 watts via two separate connections. My system is 24v. I have some old solar tile type panels that are 35 watt / 6v each and would like to use for the other 1000 watt side of the controller.
How should I wire them before I connect to controller? For 24v? These are old panels and based on meter readings are only about 5.5v-5.8v.

Thanks
Jim
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #2
    Hi Jim,
    The Classic only has 1 PV input, and combining strings of panels is best done in a combiner box. The voltage of like panels in a string add up. The amperage stays the same. The strings being combined need to be very close to the same voltage. With a 24 volt system, a good range of "PV in" voltage would be 40 to 80 volts. You can go somewhat higher but I wouldn't go much lower than that.

    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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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #3
    Like Raj says, there aren't two sides -just one input. Combining willdly different panels can be problematic for mppt controllers.

    What I would do with the old panels is put them in a separate array, 6 to a series string, with a separate inexpensive PWM controller, and orient the array to get charging going earlier (pointed southeast, northern hemisphere) or to keep floating later (southwest).
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • JimNAZ
    JimNAZ Registered Users Posts: 26 ✭✭
    #4
    Ok. After reviewing your feedback and scratching my head, I went back out and took a look. Although I have two external input connections running through a shut off box with two separate shut off switches, only one line goes from box to controller. So, since I currently have 4 high voltage panels for a total of 1000 watts, can I add those other panels if I can get the voltage the same as current panels? It looks like the current panels are coming in at 110v.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #5
    Ok, back to basics.

    What are the Vmp/Imp ratings of your 1,000 Watts of panels?

    How many panels in series/parallel connections do you have (Vmp-array)?

    What is the Vmp/Imp rating of the 6 volt panels?

    What is the maximum voltage of the panels (i.e., 600 Volts, or what)?

    How many 6 volt panels do you have?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • JimNAZ
    JimNAZ Registered Users Posts: 26 ✭✭
    #6
    Here are the specs
    Current panels 4@250watts each all wired together in parellel
    Pmax 250 watts
    voc 37.47 volts
    Isc 8.7A
    vmpp 30.34V
    Impp 8.24A

    Extra panels I'd like to use (total of 30)
    Pmax 34W
    Vmp 4.80 Vdc
    Imp 7.09A
    Voc 6.07 Vdc
    Isc 7.76A
    Max system voltage 600 Vdc
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #7
    Looking at your specs,  4@250W panels in parallel? only gives  you 30.34Vmp, this is too low, 2 strings of 2 in series would be needed for the MPPT controller on a 24V system.
    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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  • JimNAZ
    JimNAZ Registered Users Posts: 26 ✭✭
    #8
    Really? The owner of the store that I purchased these stated to connect them all together.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #9
    JimNAZ said:
    Really? The owner of the store that I purchased these stated to connect them all together.
    Series;

    If you mean they are all in one string, + to -, + to -, + to -, + to - Which would be in series (not parallel) Then that might be fine, But likely NOT a good configuration unless you live in a warm climate or have a Classic 200 (or 250). This is because the VOC is already 150 Volts in series and could exceed the max VOC of 150 + 24 volt safety feature of the Classic 150 on very cold mornings.

    Parallel;

    If you are talking connecting all the + to one and all the - ; Then he's just wrong and doesn't understand solar and should not be selling until he learns a bit...

    Either way he should have discussed these things with you.

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #10
    Likely if the small panels are known good and you have enough patience to reconfigure your array. I'd do 2 each of your larger panels in series in parallel to the other 2. I would do 2 series strings of 13 of the small panel in parallel. To do this you should add a combiner box if you don't already have one.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • JimNAZ
    JimNAZ Registered Users Posts: 26 ✭✭
    #11
    I'm sorry, I meant in series not parallel. I will have to check what classic I have. I live in northern Arizona outside of Seligman. I was just trying to save a buck and use ones I have collecting dust. If I need to buy another set of new ones I'll do that.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited June 2017 #12
    My suggestion, for what it's worth, is forget the small panels and sell them off to a hobbyist on Craigslist  experimenting with solar and invest in some more panels to match the ones you have, consider using 2 in series with parallel 3 or 4 strings, rather than 4 in series  for your 24V nominal system. Doing so would simplify the entire system with fewer connections whilst taking advantage of the current low cost of PV..... FWIW YMMV and all relevant disclaimers  o:)
    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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  • JimNAZ
    JimNAZ Registered Users Posts: 26 ✭✭
    #13
    Thank you for your suggestion. I'll scrap the idea of using all those smaller ones. I'm still not understanding why it's better to have 2 panels in series instead of 4. It has been that way for almost 3 years. Is there someplace I can go read and learn more about this?
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #14
    you can use the MidNite Solar array calculator here http://www.midnitesolar.com/sizingTool/displaySizing.php

    and it may help you understand as it tells you the max number of a given panel you can use in series, just fill in all the blanks you have data for.

     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • JimNAZ
    JimNAZ Registered Users Posts: 26 ✭✭
    #15
     Ok. Again to everyone. Thank you for your patience and help. Sorry I'm so dense with this!
     Here are the 2 different setups. The bottom one is where I am currently at.
    To clarify, I need to separate my 4 panel series into (2) 2 panel series?
    I have a connection box that came with it that will allow me to do this now. 
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  • JimNAZ
    JimNAZ Registered Users Posts: 26 ✭✭
    #16
    I rewired the panels for 2 sets of 2. Now there is 50v coming in instead of 111v. Is this good?
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,113 ✭✭✭✭✭
    #17
    If you have a long distance between your array and batteries the 4 in series high voltage configuration would be recommended , with a classic 200. If not needing to travel a long distance you don't need such high voltage and 2s2p is the better way to go. It would be a bit more efficient also.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • JimNAZ
    JimNAZ Registered Users Posts: 26 ✭✭
    #18
    How can I determine what Classic I have?
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #19
    I think it says in the menu system on the classic display. Failing that, if you're using either the MN localapp or Graham's android app to monitor, the classic model should show.

    Failing all that, maybe the bill of sale?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,113 ✭✭✭✭✭
    #20


    Wouldn't this label be on the side of the controller?  I'm not near mine now or I could verify.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • JimNAZ
    JimNAZ Registered Users Posts: 26 ✭✭
    #21
    Lol! That sticker is on the side of the controller I couldn't easily get to. I had to use a mirror.
    I have the Classic 200
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