Parallel battery bank wiring diagram

drich5
drich5 Registered Users Posts: 7 ✭✭
in Off Grid Solar & Battery Systems #1
I would like to know how to connect 8 12v batteries in parallel to achieve a perfectly balanced charge and draw.
Tagged:
· Share on Twitter

Comments

  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2
    Perfect? Pretty much not going to happen.

    But assuming they are the same age, make and model, the idea to have the same resistance across each string. In this case a since you have so many strings, You should incorporate a busbar for each the positive and negative battery cables;


    Use the same length and gauge cables to connect each battery.

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
    · Share on Twitter
  • Mike 870
    Mike 870 Registered Users Posts: 42 ✭✭✭
    #3

    I've not personally tried this, but...   http://www.iotaengineering.com/pplib/balancedcharging.pdf


    · Share on Twitter
  • mvas
    mvas Registered Users Posts: 395 ✭✭✭
    #4
    Photowhit said:
    Perfect? Pretty much not going to happen.

    But assuming they are the same age, make and model, the idea to have the same resistance across each string. In this case a since you have so many strings, You should incorporate a busbar for each the positive and negative battery cables;


    Use the same length and gauge cables to connect each battery.

    And then use "opposite diagonal" method to connect the two main power cables to the Charger & Load ...
    The (+) main power cable connects to "top end" (near battery #1) of (+) copper bar
    The (-) main power cable connects to "bottom end" (near battery #8) of (-) copper bar.
    · Share on Twitter
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,102 ✭✭✭✭✭
    edited February 2017 #5
    There is no "opposite diagonal" connection with a buss bar. Every battery gets it's own cables.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

    · Share on Twitter
  • mvas
    mvas Registered Users Posts: 395 ✭✭✭
    #6
    Tthe how's and why's of connecting 4 batteries in Parallel ...

    http://www.smartgauge.co.uk/batt_con.html
    · Share on Twitter
  • mvas
    mvas Registered Users Posts: 395 ✭✭✭
    edited February 2017 #7
    littleharbor2 said:
    There is no "opposite diagonal" connection with a buss bar. Every battery gets it's own cables.
    As I stated ...  there is opposite diagonal connections of the Main Power Cables for the Charger and the Load.

    · Share on Twitter
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,102 ✭✭✭✭✭
    #8
    Last I checked everything connects to the buss bar. If anything the loads and charging connections would probably work best at the center of the bussbar.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

    · Share on Twitter
  • mvas
    mvas Registered Users Posts: 395 ✭✭✭
    #9
    littleharbor2 said:
    Last I checked everything connects to the buss bar. If anything the loads and charging connections would probably work best at the center of the bussbar.
    No, it is not best to connect Main Power Cables to the center of bus.
    It is best to connect the Main Power Cables at opposite diagonals.

    · Share on Twitter
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,102 ✭✭✭✭✭
    #10
    Can you explain why?

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

    · Share on Twitter
  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #11
    littleharbor2 said:
    Can you explain why?

    Took me a while to figure out what he was saying too! Connect the cables Main then battery 1, 2, 3, 4, 5,6,7,8 on one side, and batteries 1,2,3,4,5,6,7,8, then main on the other busbar to keep the resistance the same including the busbar.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
    · Share on Twitter
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,102 ✭✭✭✭✭
    #12
    I can see that making sense in a minute sort of way. A minute amount of resistance is all it takes to cause uneven charging. I see the buss bar as evenly energized but I'm admittedly no expert. Anybody else care to comment?

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

    · Share on Twitter
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #13
    My guess is that the connections (battery posts and buss) are likely to be more of a problem than the buss itself in terms of resistance.

    In theory, theory and practice are the same. In practice, they rarely are ;-)
    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
    · Share on Twitter
  • bill von novak
    bill von novak Solar Expert Posts: 891 ✭✭✭✭
    #14
    Estragon said:
    My guess is that the connections (battery posts and buss) are likely to be more of a problem than the buss itself in terms of resistance. 
    Agreed.  The reason people use busbars is because they can provide a common connection point with negligible differential resistance, and most busbars accomplish this.  Between differing torque on each nut, different surface conditions on each lug, different crimp quality on each cable etc. the resistance of the busbar itself will negligible.
    · Share on Twitter
  • drich5
    drich5 Registered Users Posts: 7 ✭✭
    #15
    Okay good people, thanks for all your replies. "smartgauge" and "iotaengineering" both show the same diagram for a 4-battery string, perfectly balanced. However, I am having trouble imagining how to add the next 4 batteries, to complete a string of 8 batteries. My 2/0 cable is here now, so if someone has a diagram for 8, I will be forever in your debt.
    · Share on Twitter

Categories