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  • How much is too much panels/battery

    I have 4x100w panels in series and 2 55AH batteries in series. My mppt limit is 100V or 560W. Right now my battery bank is at 28V as i run my usual stuff. There is 10.5A going out of cc to the 24v batts and only 64V going in to cc. Are bigger batteries needed? Can i put the forbidded 5th panel on?
    it is noon and full sun now
    Last edited by Gdwats; 08-26-2017, 03:47 PM.
    900W, 40A MPPT, 230AH FLA,24V Samlex 1500W

  • #2
    Never Too Much ! (till you are broke)

    Rules:
    You have to keep the PV Voc below the kill voltage of the controller. (5 panels in series is usually too much, just buy bigger controller that can handle 200V)
    Ratio of PV watts to Battery Watt Hours needs to remain below the PV boiling the batteries, and above Chronic Deficit Charging of batteries,
    Batteries need to be large enough to supply (3, w/ standby generator) or (5 no generator) 3 or 5 days of normal power
    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
      Ok thanks. Need bigger bank.

      Q...if hooking 2 strings together in parallel, are the amps now additive from the 2 arrays and the voltage that of the largest string? Do the arrays need to be identical(can one be 300W and another 200W)? If so, a 5th panel could be used since the voltages of the 2 strings are not additive, and it should be at just 60Vmax from the 300W panels, and about 11A (5.5 from 300W array and 5.5 from the 200W? the panels are all in series

      ready for the math error lashing
      Last edited by Gdwats; 08-26-2017, 07:38 PM.
      900W, 40A MPPT, 230AH FLA,24V Samlex 1500W

      Comment


      • #4
        Math is hard - so I'll leave you to your own devices. Watts = Volts * Amps

        Each charge controller needs it's own array, or they "fight each other" for exclusive control of the array. Batteries loose.
        [ i have 2 unequal arrays, on 2 separate CC, all works fine feeding 1 battery bank. ]

        Parallel battery banks - Not the best idea, but if you must, be sure they are wired on the "Diagonal"
        http://www.smartgauge.co.uk/batt_con.html

        Parallel PV arrays ( each of my arrays, have parallel PV strings, one has 3 strings, other has 2 strings.) More than 2 strings in parallel REQUIRES a overcurrent protection device (I use Midnight switch-rated breakers)
        Panels in a series string need to me closely matched (+- 5%) of AMPS (factory panels are fine, but tough to mix a 80w panel with 160W panels and expect it to work any better than all 80w panels)
        Parallel Strings need to be closely matched in VOLTAGE
        Why:
        Series: Amps are limited to the lowest amp panel.
        Parallel: Volts are limited to the lowest voltage string.
        you CAN have a 90V 5A string paralleled with a 92V 12A string
        You can have 34V and 76V panels series in a string, as long as they each are close to the same 8 amps
        The physical sizes will be all over the place, but i'm making electrical examples here.
        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
          Originally posted by Mike90250 View Post
          Math is hard - so I'll leave you to your own devices. Watts = Volts * Amps
          yes

          Each charge controller needs it's own array, or they "fight each other" for exclusive control of the array. Batteries loose.
          [ i have 2 unequal arrays, on 2 separate CC, all works fine feeding 1 battery bank. ]

          I have only one CC. Asking about using 2 strings to feed the single array input on it by joining 2 strings in parallel, NOT the batteries.

          Parallel battery banks - Not the best idea, but if you must, be sure they are wired on the "Diagonal"
          http://www.smartgauge.co.uk/batt_con.html

          oh no, batteries are in series for 24v

          Parallel PV arrays ( each of my arrays, have parallel PV strings, one has 3 strings, other has 2 strings.) More than 2 strings in parallel REQUIRES a overcurrent protection device (I use Midnight switch-rated breakers)
          Panels in a series string need to me closely matched (+- 5%) of AMPS (factory panels are fine, but tough to mix a 80w panel with 160W panels and expect it to work any better than all 80w panels)

          All panels are 100W mono in series.

          Parallel Strings need to be closely matched in VOLTAGE
          Why:
          Series: Amps are limited to the lowest amp panel.

          that's the piece I was missing, how amps add up at the 2-1 string connector. Both strings should be delivering the same amps as they are in series, and should differ only in voltage?

          the strings are to be from series panel arrays, but joined via parallel 2-1 connectors before CC's single input.

          so if one string delivers 5.5A at 60V, and another string 5.5A at 40V. What would be delivered to the CC if joining the 2 strings in parallel and attaching to cc? Would it be 11A at 40V?

          Parallel: Volts are limited to the lowest voltage string.
          you CAN have a 90V 5A string paralleled with a 92V 12A string
          You can have 34V and 76V panels series in a string, as long as they each are close to the same 8 amps
          The physical sizes will be all over the place, but i'm making electrical examples here.
          not sure if that is worth doing.
          Last edited by Gdwats; 08-26-2017, 10:07 PM.
          900W, 40A MPPT, 230AH FLA,24V Samlex 1500W

          Comment


          • #6
            If you only have 250 Watts going to the batteries at noon on a clear sunny day, and 64V off of four panels in series, you may have a panel/controller issue. Then again your battery might be entering Absorb charging.
            Last edited by AzRoute66; 08-27-2017, 12:06 AM.

            Comment


            • #7
              Originally posted by AzRoute66 View Post
              If you only have 250 Watts going to the batteries at noon on a clear sunny day, and 64V off of four panels in series, you may have a panel/controller issue. Then again your battery might be entering Absorb charging.
              Thanks, that's probably it as battery was at 28V an I use the renogy rover 20A mppt. I'll check again tomorrow after draining some juice.
              900W, 40A MPPT, 230AH FLA,24V Samlex 1500W

              Comment


              • #8
                About the voltage..
                I think 20V is panel max, and 18V is gen operating voltage of each panel. So 4 panels in series should operate at around 72V and a max of about 80V. They are leaning up against a fence and angle is not optimum, and there is 35 feet of mc4 wire from panels to cc. Is 64V worrisome under these conditions? Should I retest each panel?
                900W, 40A MPPT, 230AH FLA,24V Samlex 1500W

                Comment


                • #9
                  Sounds like your panels are working just fine. The Vmp. is a Standard Test Condition number. Real world numbers will almost always be less. As your panels warm up in the sun the voltage will decline.
                  MC-4 wire makes no sense as MC-4 refers to the connectors on the end. 35 feet of distance equates to 70 feet if wire through which the current must travel. If your wire gauge is too small you will have excess voltage drop.That being said, with the numbers you are seeing it looks like everything is fine with your panels.
                  2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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                  • #10
                    Thanks LH. At 71V this morning 930AM. The " mc4 connection extension cable" is 6AWG, I think, and there is 70 ft of it.
                    Last edited by Gdwats; 08-27-2017, 12:31 PM.
                    900W, 40A MPPT, 230AH FLA,24V Samlex 1500W

                    Comment


                    • #11
                      That will likely drop as the day warms up. All good.
                      2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                      Comment


                      • #12
                        Thanks again. I am thinking of getting 4 x Trojan 6v 235HR T105RE. Is the T105 just as good anyone know?
                        900W, 40A MPPT, 230AH FLA,24V Samlex 1500W

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                        • #13
                          T-105RE or Trojan Industrial Line
                          Last edited by NEOH; 08-27-2017, 02:44 PM.

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                          • #14
                            Thanks much. Just ordered a 40A mppt in preperation.
                            900W, 40A MPPT, 230AH FLA,24V Samlex 1500W

                            Comment


                            • #15
                              Oh boy...can I use 2 CC on one battery bank?
                              I have a 40A mppt and a 20A MPPTs. Both have 100V input limit.
                              Or should I rewire all my panels to parallel and feed amps at low volts? I don't see anything about minimum input voltages, and with 4 panels now, and a couple more in mind that'd be 4 x 5.7=22.8A and 6x5.7=34A to the one cc after the next 2 100W panels arrive...line loss be ##$^!ed.

                              battery bank is 225AH 24v fla.
                              Last edited by Gdwats; 08-28-2017, 12:23 AM.
                              900W, 40A MPPT, 230AH FLA,24V Samlex 1500W

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