best approach to string 12 2 volts agm batteries

DarkstormNHDarkstormNH Posts: 40Registered Users ✭✭
Good folks

i have 12 2 volts batteries, should i string one 24 volts or 2 parallel string at 6*2=12 volts than parallel for 24 volts
feedback suggestions will be appreciated

Comments

  • EstragonEstragon Posts: 2,226Registered Users ✭✭✭✭
    Parallel 2x12v strings will give you a higher capacity 12v bank. If you need 24v with 12x2v cells, it has to be a single series string.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • BB.BB. Posts: 27,353Super Moderators admin
    edited January 21 #3
    What are your needs? 12 volt or 24 volt. The 12 volt and 24 volt configurations store exactly the same amount of energy.

    12 volt, more off the self small stuff to run. 24 volt, less voltage drop, smaller cables, more efficient use of charge controller (2x more solar panels at 24 volt battery bank).

    12 volt bank needs heavier cables, has more issues with voltage drop in cables.

    -Bill

    PS, what is the AH of the cells?
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Posts: 7,612Solar Expert ✭✭✭✭
    are the batteries sealed or flooded ?   Series is the better configuration, if you require 12V, there can be imbalance issues between strings not sharing equally,  diagonal wiring can ameliorate some of that issue.
     Sealed batteries have more issues when in parallel, because of their low internal resistance



    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

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  • DarkstormNHDarkstormNH Posts: 40Registered Users ✭✭
    BB. said:
    What are your needs? 12 volt or 24 volt. The 12 volt and 24 volt configurations store exactly the same amount of energy.

    12 volt, more off the self small stuff to run. 24 volt, less voltage drop, smaller cables, more efficient use of charge controller (2x more solar panels at 24 volt battery bank).

    12 volt bank needs heavier cables, has more issues with voltage drop in cables.

    -Bill

    PS, what is the AH of the cells?
    each batterie is 700 amp hour, I will need 24 volts since the inverter is 24 volts
  • EstragonEstragon Posts: 2,226Registered Users ✭✭✭✭
    Then there is no choice. With 12x2v cells, you will have a single series string of ~700ah @ 24v. There is no parallel option.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • DarkstormNHDarkstormNH Posts: 40Registered Users ✭✭
    Estragon said:
    Then there is no choice. With 12x2v cells, you will have a single series string of ~700ah @ 24v. There is no parallel option.
    thank you very much

  • BB.BB. Posts: 27,353Super Moderators admin
    edited February 6 #8
    You can parallel for 12 volts @ 1,400 AH. And that is 140 amps for a 10% rate of charge.

    A lot of current, heavy cabling, and 2x solar charge controllers.

    Of course, it does depend on your needs.

    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Sol4rSol4r Posts: 7Registered Users, Users Awaiting Email Confirmation ✭✭
    Estragon said:
    Then there is no choice. With 12x2v cells, you will have a single series string of ~700ah @ 24v. There is no parallel option.
    good to know
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