Two 24v battery bank with 8 6v batteries

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gjlsan
gjlsan Registered Users Posts: 4 ✭
in Solar Beginners Corner #1
Hi,

I'm trying to configure two 24v battery bank with 8 6v batteries (S-550). Is the diagram attached correct?
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #2
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    It seems to me the string on the left may get a better charge from the controller, and the string on the right may carry more discharge load to the inverter.

    I would either:
    1. Run two short equal lengths of wire from each string + and - to a common attachment point for controller and inverter + and -
    OR
    2. Attach the both controller and inverter + on (eg) the left string, and both - on the right.

    My personal choice would be #1, as getting multiple good connections on a single battery post can be hard.

    The idea is to get equal resistance between the strings. More info at
    http://www.smartgauge.co.uk/batt_con.html

    Also, there should be a fuse/breaker (sized per manufacturers spec.) between the controller + and batteries. I'm assuming that's a fuse on the inverter +. My preference is breakers, as they make handy shut-offs, but fuses are ok.
    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
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  • gjlsan
    gjlsan Registered Users Posts: 4 ✭
    #3
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    Thanks,

    The configuration has the breakers on the combiner box before the controller. Is there still need for a breaker/fuse after the controllere?
    Estragon said:
    Also, there should be a fuse/breaker (sized per manufacturers spec.) between the controller + and batteries. I'm assuming that's a fuse on the inverter +. My preference is breakers, as they make handy shut-offs, but fuses are ok.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #4
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    Installing a circuit breaker on the output of the controller is required to protect the conductors between the battery/controller from becoming the fuse in the event of a short circuit within the controller itself or terminals etcetera, the battery is capable of supplying massive amounts of current. In addition it will provide a means of disconnect should the controller, which is powered by the battery, need to be rebooted for example. When installing the breaker it is important to remember the battery is the source, or the component with the highest energy potential, so if the breaker is polarized, the battery should be connected to the terminal marked +.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #5
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    Yes, a fuse/breaker is needed between the controller and bank, for the reasons McGivor notes.
    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
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