I want to charge 3 separate battery banks from one solar array

lewalewa Registered Users Posts: 1 ✭
in Advanced Solar Electric Technical Forum #1
Hi guys
I’d appreciate some advice on the following:
I have 3no 10kw inverters powering my office. Each inverter is connected to a single phase and has a battery bank made up of 4 batteries(total is 3no inverters and 12 batteries). I want to expand my system and I’m thinking of adding batteries and solar panels. I want to install 2 dozen solar panels and not sure how to connect the system is such a way that my solar array will charge ALL three sets of batteries. So in short, I want to have 24 panels of 300w each, that will power all the batteries. I could split the panels into 3x8 to power each set of batteries but I’d rather not. How feasible is that? Thanks
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Comments

  • Belmont SolarBelmont Solar Registered Users Posts: 26 ✭✭
    #2
    Why not have one big Battery Bank for everything ?
  • BB.BB. Super Moderators, Administrators Posts: 28,443 admin
    #3
    What does the term "3no" mean?

    What brand/model of inverters do you have? Link to manual? What solar charge controllers do you have? Backup AC genset? Is this a backup system for unreliable utility power?

    I agree with Belmont Solar. Why can you not connect all three inverters to one large battery bank+solar array(s)+solar charge controller(s).

    This is a large system? 3 phase system with 30 kWatts of AC inverters total?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jonrjonr Solar Expert Posts: 1,199 ✭✭✭✭
    edited April 2018 #4
    Can the battery banks have a common ground?  Two ACRs should work.   But combining all into a single bank makes more sense.

    https://www.bluesea.com/resources/1366


  • EstragonEstragon Registered Users Posts: 3,262 ✭✭✭✭✭
    #5
    Assuming the batteries are 4x12v in series = 48v nominal banks... 24 x 300w panels =7.2kw ÷ 48v = 150a charging, so likely into multiple charge controllers anyway. Why is having the array split into 3 an issue? If staying with three separate banks, having the array split with a controller and array for each bank seems best IMHO. Having multiple MPPT controllers on a single array is problematic. I think you'd need to find a big enough single controller capable of charging 3 banks independently. There may be such a thing, but splitting the array on 3 smaller controllers would give much wider choice of controllers and likely less costly.

    As I understand it, an ACR parallels the banks to charge, so you're sort of half way to a single bank anyway. It works well to isolate a starting battery so as not to discharge it with house bank and get stuck with no way to start the engine, but still charge the starting battery from source(s) used to charge house bank. I'm not sure what advantage separating discharge for each phase helps though. Maybe if one phase is dedicated to critical loads? If not, a single bank seems a better long-term design to me.
    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
  • Belmont SolarBelmont Solar Registered Users Posts: 26 ✭✭
    edited April 2018 #6
    Multiple charge controllers are not necessarily problematic, unless simply not set up correctly. It is best if the largest one can handle a majority of the absorption and float cycle. Or use MidNite Classics with the “Follow Me” mode
  • EstragonEstragon Registered Users Posts: 3,262 ✭✭✭✭✭
    #7
    I have multiple classics set up with "follow me", which works well charging a single bank BUT each controller has its own array. My understanding is having them share a single pv array messes up mppt.

    Follow-me just makes all connected classics operate in the same charge mode (eg. all in absorb at the same time). It doesn't share mppt info AFAIK.
    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
  • Belmont SolarBelmont Solar Registered Users Posts: 26 ✭✭
    #8
    That is correct
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