Battery Wiring Help

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MarleyWrigg
MarleyWrigg Registered Users Posts: 2 ✭
in General Solar Power Topics #1
I just got four 12 v batteries and I have a 12 v charge controller. Can someone explain to me how to wire my batteries together? Thanks!
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #2
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    The simple explanation is for a 12 volt battery bank with more capacity (4x batteries then 4x AH rating of a single battery) is to connect all the positive leads together (the positive bus). And all the negative lead together (negative bus). This is connecting your batteries in "parallel".

    The detailed answer includes several different ways to connect the batteries in parallel in a "optimum" manner (so all batteries see the same charging and discharging current):

    http://smartgauge.co.uk/batt_con.html

    For larger batteries and battery banks--For safety each battery (or series string of batteries for higher voltages) should have a fuse or circuit breaker per string (for safety). Wiring to the batteries, loads, charge controller needs to be sized for the amount of current being carried (and the wiring needs to be heavy enough to carry that current without overheating).

    Then there is the question of what size wiring (gauge), what type of terminals, etc...

    And the battery charger--Many chargers come with "alligator clips"... While these are "OK" for a quick and dirty connection to charge a battery (temporary charger or DC load connection). Long term connections should be bolted with ring lugs or similar. Alligator Clips are unreliable and unable to carry heavy current for long term connections.

    Member 2manytoyz has a nice website with lots of photos of his solar power and related systems. And it goes from simple connections to as he grows the systems. Lots of DIY hardware.

    http://2manytoyz.com/

    With all things solar (and electrical), details matter. We want your installation to be safe and not risk harm to you and your family/home/etc.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited September 2019 #3
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    Above are three methods, the top image shows how the current is evenly distributed to each battery, the middle image shows a common method which works well with 2 batteries but not so well with > 2 ,as the middle 2 suffer under charging and the outer ones suffer under load.

    The bottom image is shows how not to configure them, this is a very common mistake.

    These are generic images, over current protection will be needed and both loads and charging go to the same terminals.
    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.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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