Skip to content
  • Register

    • Battery bank vs. PV input

    Registered Users Posts: 28 ✭✭
    in Advanced Solar Electric Technical Forum #1
    Is there an easy way to determine the balance between the battery bank size and the PV production? As an example, I will shortly have 3720 watts of PV on my roof, and 900 AH of battery capacity. My main concern is being able to completely charge the batteries with a day or two of sun, and not have to use the generator. Any suggestions would be appreciated.
    · Share on Twitter

    Welcome!

    It looks like you're new here. Sign in or register to get started.
    Sign In
    Register

    Comments

    • Solar Expert Posts: 462 ✭✭
      #2
      Re: Battery bank vs. PV input

      Voltage of your system?
      · Share on Twitter
    • Solar Expert Posts: 9,583 ✭✭✭✭✭
      #3
      Re: Battery bank vs. PV input

      Fire ! Ready ! Aim!

      NZRR wrote: »
      Is there an easy way to determine the balance between the battery bank size and the PV production? As an example, I will shortly have 3720 watts of PV on my roof, and 900 AH of battery capacity. My main concern is being able to completely charge the batteries with a day or two of sun, and not have to use the generator. Any suggestions would be appreciated.


      Your charging amps, should be about 10% of your battery amps, so if you have 900A of battery, you need 90A of charging. That keeps current limit below plate warping heat, and still enough amps to stir / bubble electrolyte in the EQ cycle.

      What you haven't told us, is the battery voltage, and the array voltage, if all batteries are in series, or parallel, or series-parallel combo. What is your charge controller, and how cold in winter, and hot in summer . Those all affect the PV voltage and how to set it up with the charge controller.
      Powerfab top of pole PV mount | 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 ,

      · Share on Twitter
    • Banned Posts: 17,615 ✭✭✭
      #4
      Re: Battery bank vs. PV input

      Basic, "starting point" formula used for off-grid:

      Battery Amp/hrs ('20 hr rate') * 10% = Target Charging Current
      TCC * charge Voltage = effective array Watts needed
      Watts / system efficiency (typically 80%) = total array size

      Without the system Voltage, this is as close as anyone can come to an answer.
      · Share on Twitter
    • Registered Users Posts: 28 ✭✭
      #5
      Re: Battery bank vs. PV input

      My system voltage is 48. I have an Apollo T80HV and the batteries will be two banks of 8 Rolls S600s connected in parallel (450 Ah for each bank). I am using UniSolar PVL-124s, three in series for 90 volts, with 10 arrays, which should generate up to 40 amps. It gets to around 86 degrees on average in the summer, and to maximum -32 degrees (F) in the winter. Thanks for the input.
      · Share on Twitter
    • Solar Expert Posts: 68 ✭✭✭✭
      #6
      Re: Battery bank vs. PV input

      This thread had good discussion from the opposite imbalance. If you two were neighbors solar perfection would be within reach. :)
      · Share on Twitter

    Welcome!

    It looks like you're new here. Sign in or register to get started.
    Sign In
    Register

    Welcome!

    It looks like you're new here. Sign in or register to get started.
    Sign In
    Register

    Quick Links

    Categories