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Series or parralell with an mppt CC

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  • Series or parralell with an mppt CC

    I was told on this forum that If I run the panels in parralel the mppt CC will not work The CC I have (600) watt will work with both 12 and 24 volt systemsit automaticly differentiates between 12 or 24 volt..I already bought a 12 volt 600 watt inverter people are telling me if panels are wired in series the 12 volt batterys have to be wired in series to make 24 volt Also I will need a new 24 volt inverter I don't want to go that route..I'm running 4 100 watt panels with a 40 amp mppt CC with 12 volt deep cycle marine batteries,I know not the best choice but had them brand new and going to use them until they wear out..

  • #2
    Your controller will determine the system voltage by the battery bank voltage. Always connect the battery first for this reason. Your friends are incorrect about series wiring your panels determining the system voltage. MPPT controllers want to see higher voltage than the battery voltage.

    What controller are you using? There are a lot of inexpensive controllers being sold as MPPT which aren't MPPT. Photo or link to controller will clear this question up real fast.
    2.2kw Suntech mono, Classic 200, NEW Trace SW4024


    • #3
      MPPT controllers need some "headroom" to function.. They are designed to take high voltage PV (which is easy to run long distances) and down-convert it to battery charging voltage.

      A 12V battery needs to be recharged at up to 15V. Assume there is a couple of volts lost in the charge controller (there is) and you need a solid 18V on a hot day, to recharge a 12V battery with a PWM controller.

      If you spend the $ on a MPPT controller, you generally need to supply it with a PV voltage of at least 1.4x the battery charging voltage. For 12v battery, that would need at least 21Vmp , 30Vmp would be even better. Running a charge controller at it's minimum input threshold may not work on a warm day with PV panel voltage drooping because of heat.
      To ensure proper start up and MPPT operation, the minimum initial PV input voltage should be at least 30% higher than the highest expected battery voltage.

      But if you are running so low in voltage, why spend the $ for a MPPT controller
      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



      • #4
        ok last question I have a renogy 40 amp mppt CC, I spent the extra $ on mppt because I was told it would be more efficiant. I have a renogy 600 watt pure sine wave inverter 12 volt only ,4/100 watt panels starting out with two new large marine deep cycle batteries.Now my question do I wire the panels in series or parallel?Can I run panels in series then batteries in parallel to keep the system at 12 volts so I can use the 12 inveryer?The run from from panels to charge controller is 45 ft im using 8/2 duplex tinned copper wire. Off grid cabin only running tv and a couple led lights and possibly a small fridge.
        Last edited by greghost; 06-16-2019, 10:31 PM.


        • #5
          Wire the panels 2 in series for each string then wire the two strings in parallel, run these to the controller and keep the batteries in parallel, use the inverter you have. The MPPT controller will transform the higher p.v. input voltage to the battery voltage it will work fine with a 36 volt input to charge a 12 volt battery


          • #6
            Once you series wire the two pairs of panels can be paralleled using one of these. Order a 100 foot MC-4 extension cable, (preferably 8 gauge), and cut it in half to go from the array to the controller.

            parallel connectors.jpg
            2.2kw Suntech mono, Classic 200, NEW Trace SW4024


            • #7
              Thanks Everyone for you answers new to this and don't want to have to spend more money .Great forum sorry for the repetitive questions.


              • #8

                Ordered branch connectors and 50ft of duplex 8/2 tinn ed copper Thank you for all your help you guys have been a big help.