Battery wires to MPPT controller

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GNSolar
GNSolar Registered Users Posts: 4 ✭
in General Solar Power Topics #1
I'm installing a solar controller to my system.  I currently have a 24 volt battery bank connected by enormous cables ( 2 each to positive and negative battery terminal)  to a large positive and negative DC buss'  .   This bus is in turn connected to the inverter by large cables.   When wiring the new charge controller, is it ok just to wire directly to the bus or must the wires go to the battery terminals.    Same question for the small battery voltage wire that comes from the controller.      Thanks for comments.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #2
    So as everyone can understand correctly before commenting, could you describe your battery, series, parallel etcetera.
    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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  • GNSolar
    GNSolar Registered Users Posts: 4 ✭
    #3
    My battery bank is 4 225 AH 12 v agm batteries.  Batteries are wired in series and parallel for 450 AH at 24 volts.


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  • Photowhit
    Photowhit Solar Expert Posts: 6,017 ✭✭✭✭✭
    #4
    I agree that this isn't very well explained. I suspect you are fine connecting to the bussbar for the larger cables.

    The 'voltage' cable (likely a thin phone cable type?) should be connected directly to the battery. It measures the actual voltage at the battery rather than the system voltage. This avoids reading the voltage dropped over the length of the cables. If you give the make and model of the charge controller we might be able to find a manual on line for you to read.
    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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  • Estragon
    Estragon Registered Users Posts: 4,498 ✭✭✭✭✭
    #5
    My guess is the two heavy cables for each of the +/- bussbars (4total) are making the parallel connection at the bussbar. In that case, it seems to me the voltage sense wire should be terminated on the buss, shouldn't it?
    Off-grid.  
    Main 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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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #6
    Are the positive and negative conductors at the battery side diagonally opposite, positive on one string negative on the other? This would be important for ballance of charge and discharge of both strings, if so connecting the controller to the bus bar would be fine, the battery sense wires are generally connected to the battery terminals, but if the conductors are large and short between the bus bar and terminals it probably wouldn't matter that much, but if possible connect to the battery terminals. I'm guessing Morningstar 
    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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  • GNSolar
    GNSolar Registered Users Posts: 4 ✭
    #7
    yes , Morningstar.  I'm not sure what you mean by diagonally opposite.  Is there a way to put a photo on my post?

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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #8
    Read the attached Pdf, simpler for me than looking for a diagram, it's from  Morningstar.
    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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  • Aguarancher
    Aguarancher Solar Expert Posts: 315 ✭✭✭
    #9
    to post a picture, click on the picture icon, it will say attach image
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,695 admin
    #10
    I do see a PDF attachment to click on. Do you Aguarancher?

    And, here is a web page that goes into a bit more detail:

    http://www.smartgauge.co.uk/batt_con.html

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • GNSolar
    GNSolar Registered Users Posts: 4 ✭
    #11
    Interesting stuff, as it turns out my bank is not connected diagonally opposite.  Another thing to do!  Thanks

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  • myocardia
    myocardia Solar Expert Posts: 118 ✭✭✭
    edited June 2017 #12
    GNSolar said:
    Interesting stuff, as it turns out my bank is not connected diagonally opposite.  Another thing to do!  Thanks

    That's by far the most important thing for you to do, out of all of the things that have been mentioned so far. Right now, you are running your entire system on 2 batteries, which are later being recharged by the other 2 batteries. You would have twice the instantaneously available ampere hours of battery, along with ~¼ the battery damage/wear and tear (on the two batteries that are currently powering your system). Change that before you even consider changing anything else. Good luck.

    DoD= depth of discharge= amount removed from that battery   SoC= state of charge= amount remaining in that battery
    So, 0% DoD= 100% SoC, 25% DoD= 75% SoC, 50% DoD= 50% SoC, 75% DoD= 25% SoC, 100% DoD= 0% SoC
    A/C= air conditioning AC= alternating current (what comes from the outlets in your home) DC= direct current (what batteries & solar panels use)
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