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  • New Off-grid solar setup advice required.

    Guys n Gals I need help with a small PV setup. I am planning to setup a small PV for my house. The list is as follows.
    1. Solar Panels 24V -- 2 x 250 Watt Monocrystalline (500 Watts). Voc = 37.5, Isc = 8 A,
    2. Charge Controller -- 30 A MPPT epsolar Tracer3210A.
    3. Local car float lead acid 200 Ah, 24 volts (2 x 12 Volt).
    4. 1500 VA inverter AC (980 Watts AC).


    The panels will be 24 Volts and will be in series. The Batteries will be in 24 Volt (in series) and the Inverter also is 24 Volts. The weather is very hot in my region, summer easily getting above 35 - 40 degree C and winter is about 20 - 30 degree C.

    My first question is, can I possibly add another panel to the system. Making it 3 panels (Voc= 37.5 * 3 = 113 Volts) which is higher than the rating of the CC. My argument is that the panels will never produce the said output due to a lot of factors aka losses. Would it be wise to use 3 panels? if the PV is of lower wattage (200 Watts) can 3 panels be used (Max. PV input power 780W)?
    Secondly, the system will be utilized throughout the day 8AM-4PM. My Max. usage is 10.8KWh per/day but it will be near 5 KWh per/day (not everything is running all the time). During the night time the power will be from the mains but not charging the battery. The battery might be used for 1-2hrs at night when main electric fails.
    Will the charging to the batteries be enough for the night usage and then charging in the day time?

    Thanks
    Last edited by Zcode; 04-09-2017, 09:21 AM. Reason: Complete post is not going online.

  • #2
    Originally posted by Zcode View Post
    My first question is, can I possibly add another panel to the system. Making it 3 panels (Voc= 37.5 * 3 = 113 Volts) which is higher than the rating of the CC. My argument is that the panels will never produce the said output due to a lot of factors aka losses. Would it be wise to use 3 panels? if the PV is of lower wattage (200 Watts) can 3 panels be used (Max. PV input power 780W)?
    No you cannot. Your argument does not hold water. As soon as first light hits the panels in the morning, panel voltage is Voc before the controller turns on. As soon as your batteries are charged, panel voltage goes to Voc. If you have an open circuit condition, a flashlight will make panels go to Voc. That is why they call it Voltage Open Circuit.

    Originally posted by Zcode View Post
    Secondly, the system will be utilized throughout the day 8AM-4PM. My Max. usage is 10.8KWh per/day but it will be near 5 KWh per/day (not everything is running all the time). During the night time the power will be from the mains but not charging the battery. The battery might be used for 1-2hrs at night when main electric fails.
    Will the charging to the batteries be enough for the night usage and then charging in the day time?
    All I can say is



    Look I seriously doubt those 12 volt car batteries are 200 AH. If they were would weigh 250 pounds each or 112 Kg. More than likely they are 200 CCA or maybe at best 100 AH each. Doe snot really matter because even if they were 200 AH only contain less than 4.8 Kwh. Being car batteries if you discharge them more than 5 or 10%, you will destroy them in a month or less. Soo please stop and thing how in the hell do you expect to use almost 11 Kwh per day with a gas tank that only hold less than 4.8 Kwh.

    If you intend to use 11 Kwh/ day would require a 24 volt 2000 AH deep cycle battery or 3000 pound battery along with a 4000 watt panel system with two very expensive 80 amp charge controllers. Time to wake up and admit failure to launch.
    MSEE, PE

    Comment


    • #3
      Haha haha nice emoji. Well then 2 x 250 panel or higher can be used not exceeding 90Voc.
      I have no access to new golf cart batteries but might get some used sealed lead acid ones. I was planning to use the FLA for just one year to test and trial.
      If say it's 4-5 kWh (4000/24 = 167, 167/0.8(@80%) = 210). Is this calculation right?

      Comment


      • #4
        Originally posted by Zcode View Post
        Haha haha nice emoji. Well then 2 x 250 panel or higher can be used not exceeding 90Voc.
        I have no access to new golf cart batteries but might get some used sealed lead acid ones. I was planning to use the FLA for just one year to test and trial.
        If say it's 4-5 kWh (4000/24 = 167, 167/0.8(@80%) = 210). Is this calculation right?
        Your math is ok. You might be better off getting 4 x 6v 232Ah batteries which are pretty common although they are not sealed they will be less expensive then say the AGM type.

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