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Seeking advise re Panel to Battery Balance

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  • Seeking advise re Panel to Battery Balance

    Hello, I am new here and to Solar wondering if anyone can guide me in the right direction to set up a 12V solar system my problem is
    I have 4 x 250W solar panels that are rated at
    Maximum peak voltage (VMP) 18.7V
    Open circuit voltage (VOC) 23.37V
    Max peak current (IMP) 13.37A
    Short circuit current (ISC) 14.85A
    I have a 60A PWM regulator/controller That is rated for PV input of 730W at 12V / 80V max input
    I am thinking of getting another same 60A PWM regulator/controller and run 2 panels parallel on each regulator/controller?
    Is this setup likely to over/undercharge my Batteries?
    would having 2 controllers provide too many amps?
    Battery specs
    Bulk Charge Initial Charging Current less than 30A
    Voltage 14.5V @ 25C/77F
    Temp. Coefficient -30mV/C
    Float Charge No limit on Initial Charging Current
    Voltage 13.5V @ 25C/77F
    Temp. Coefficient -20mV/C
    I would be connecting the regulators /controllers to a battery bank consisting of 3 x 140AH AGM batteries connected parallel giving 420AH that will run a 1000W 12V/240AC inverter that will have usually have 300W or less like 150W max load.
    Also, the Batteries have already been charged to full capacity with an AC charger.
    Thank you

  • #2
    Welcome.

    With your 4, 13A panels, you can expect to get a maximum of 53.48 amps out of them. In normal conditions, well aimed, you could expect about 43A.

    Your panels are the right voltage to use all in parallel with 12v batteries and a PWM controller.

    However, your 3 batteries will never see their max charge current, and if your inverter has a high standby power consumption, you may have trouble with daily recharging all that you have taken out of the batteries.
    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


    • #3
      Thank you for your answer I had been confusing myself by mixing up series and parallel wiring etc
      this has cleared up most of my issues ie should be ok to use one controller but what will do I need to do to keep my batteries fully charged?
      This is a pic of the estimator I have been using if anyone would like to critique
      The Fridge is I think rated at 80A per 24 hours so I just put 75W@ 13 hours to come up with 80A value
      Thanks
      Spec Estimates.png
      Attached Files
      Last edited by Dand; 12-16-2019, 06:28 AM. Reason: I was unsure of my proposed power usage

      Comment


      • #4
        The more accurate your load calculations , the more accurate the rest of your system design will be. You need to plan the whole system out, using watt hours. Don't get fouled up comparing 60A @ 12V with 60A @ 200V, vastly different amounts of power between them.

        A good rule of thumb is to be able to harvest 2x as much as you consume. That simple guideline takes into account all the normal conversion & efficiency losses.
        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


        • #5
          Hi and thanks once again, So I checked and rechecked and I think my daily usage would be between 1200WH to 1400WH and those figures are fairly inflated
          I just have one concern about my panels and controller I understand that my amps and volts are under the limit of my controller but it says on controller PV max 750w @ 12V and I would be connecting 4 x 250W @12V is this going to be ok?
          Can not thank you and these forums enough

          Comment


          • #6
            Originally posted by Dand View Post
            ..... controller PV max 750w @ 12V and I would be connecting 4 x 250W @12V is this going to be ok?.....
            Nope, that would be 1,000 w of PV connected to a 750w controller. That wattage would translate to 76A of charging current, and even a good controller with 3% loss, could cause enough self-heating to exceed the design limit of the 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

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

            Comment


            • #7
              Originally posted by Mike90250 View Post

              Nope, that would be 1,000 w of PV connected to a 750w controller. That wattage would translate to 76A of charging current, and even a good controller with 3% loss, could cause enough self-heating to exceed the design limit of the controller.
              If the person points the panels at different directions (E, W & S) they may get away with wiring more panel wattage then the controller is rated for. I beleive the max input watt rating is determined by all of the panels pointed at the same compass point.

              Comment


              • #8
                Hi and thank everyone again, I will be having 4 panels on one frame in one direction as limited roof space and I see that that the issue of 2 PWM controllers has been addressed on these forums in 2009 and probably numerous times since so thanks for your patience and I feel that is the way to go to fit my budget at the moment,

                Comment


                • #9
                  Hi, So got up and running today only 2 of my panels as I am awaiting another controller so 2 x 250W panels specs as above in my original post connected to 60A PWM controller linked to 3 x 140AH batteries wired parallel Connected to1000W inverter running a 70W AC and a145L Fridge or Freezer the fridge specs are
                  Compressor ALPICOOL
                  Refrigerant R134a 45g
                  Rated Power 75W
                  240V consumption 0.17kWh/24hrs
                  12V consumption 80A/24H approx
                  Max. ambient temp 38°Cthat is on 240V stepdown to 12V plug
                  When first connected controller blinked a few times and had a reading of 14.2V soon stopped blinking and went to 13.5V this was at midday and was 30C/86F at 2 PM 35C/95F at 5 PM
                  by 6 the controller was showing 12.6V and so I shut down the inverter not sure if I should be getting better figures will it perform better with my other 2 panels connected and or will I need another 140AH Battery?
                  Thanks and Happy Holidays
                  Last edited by Dand; 12-21-2019, 04:33 PM. Reason: edited as found and added accurate fridge specs

                  Comment

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