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  • Small Off Grid DC System with Storage Batteries

    Looking for your experienced input for a system for my storage garage.
    (Max $ 3000 budget for solar equipment)

    System will support:

    (qty 3) 16 ft long 75 watt 12VDC LED (UL IP68) light tapes (max one hour use per day)

    (qty 1) garage door opener - Genie 750 chain drive with 12VDC battery back up - to be used in 12V mode at all times (no inverter) - (max usage will be 6 times per day)
    Motor is rated at 3/4 hp, and will be operating approximately half minute on each event (the factory battery that supports this function is 12VDC 8Ah)


    Location is near Pittsburgh PA, estimating 3.5 hrs full sun per day


    Tentative hardware list:

    (qty 1) Morningstar SS-MPPT-15L SunSaver Charge Controller
    (qty 3) Solarland SLP160S-12 Silver Mono Panel, 160 watts. 8.8A 12VDC
    (qty 2) CR430 flooded batteries, #2/0 AWG battery interconnects, 430 amp hours at 12Vdc

    Does this seem balanced ? Thanks.

  • #2
    Originally posted by Lars1361 View Post

    Tentative hardware list:

    (qty 1) Morningstar SS-MPPT-15L SunSaver Charge Controller
    (qty 3) Solarland SLP160S-12 Silver Mono Panel, 160 watts. 8.8A 12VDC
    (qty 2) CR430 flooded batteries, #2/0 AWG battery interconnects, 430 amp hours at 12Vdc

    Does this seem balanced ? Thanks.
    No. Next question.

    MSEE, PE

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    • #3
      I wanted to stay simple without an inverter.

      Would a fourth panel be required or does two panels make more sense?

      I do not understand the relationship of the panel to the process.

      Comment


      • #4
        Where do I start with what is wrong.

        Let's start with the Charger Controller. You obviously did not read one word of the specs or do any homework. If you had read the Controller specs then you would know with a 12 volt battery the maximum input is 200 watts, and 400 watts @ 24 volt battery. So how in the hell did you come up with 480 watts? At 480 watts would take a 40 amp controller. You are off by 240%.

        Why on earth would you use expensive 12 volt battery solar panels with a MPPT Controller? Battery panels cost 2 to 6 times more per watt than higher voltage Grid Tied Panels. All you need is a 200 watt panel.

        Lastly the largest 12 volt battery you can use with a 200 watt panel and 15 amp controller is 180 AH and that is pushing it.

        You can certainly use 2/0 if you do not mind throwing money away.

        Ge ahead and get mad, I DO NOT CARE. I just saved you from yourself and saved you over $2000. You can do what you want for less than $1000.

        1 x 200 watt panel, $200 to $300
        Morningstar SS-MPPT-15L SunSaver Charge Controller, $200
        1 x Trojan T-1275 Plus 12 volt 150 AH battery, $220

        Total $700 to $800
        Last edited by Sunking; 12-18-2017, 02:14 PM.
        MSEE, PE

        Comment


        • #5
          No anger here, only ignorance.

          Thanks for the guidance.

          When will you be over for the install ?

          Comment


          • #6
            where again is the install ?
            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
              Near Pittsburgh PA

              Comment


              • #8
                Lars a couple of things that might help. Batteries have minimum and maximum charge currents they can accept. Essentially the max is C/8 and some like a Trojan T-105 can handle up to C/4. The minimum is C/12. Where C = the battery rated amp hour capacity, and the number is Hours like 8 or 12 hours.

                With a MPPT Controller, Charge Current = Panel Wattage / Battery Voltage. Use 13.5 volts for a 12 volt battery. Example 200 watts / 13.5 amps = 14.8 amps. Thus the MS 15 amp Controller is maxed out with a 200 watt panel, and 400 watts with a 24 volt battery. Try reading this thread, it should help.

                FWIW you have overestimated Sun Hours. In Pittsburg 2.2 Sun Hours. There are a lot of Stickies in the Off-Grid Solar section particularly in the Off-Grid Soar Panel Systems and Batteries subforums. They should answer every question you can think of and answer questions you do not know to aks.
                Last edited by Sunking; 12-18-2017, 05:55 PM.
                MSEE, PE

                Comment


                • #9
                  Great information. I have some math to do.

                  If I am understanding correctly, my power consumption outside of bulk charge could take the battery to a depleted state that it would never recover from. (especially in the winter months)
                  Last edited by Lars1361; 12-19-2017, 12:01 PM.

                  Comment


                  • #10
                    Originally posted by Lars1361 View Post
                    Great information. I have some math to do.

                    If I am understanding correctly, my power consumption outside of bulk charge could take the battery to a depleted state that it would never recover from. (especially in the winter months)
                    Not sure I understand your question. If you daily power usage exceeds what the panels can generate to fully recharge the batteries, you are in deficit charging. Unlike money you cannot borrow or receive credit, you would destroy the batteries and go dark.
                    MSEE, PE

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