battery diagrams

blue
blue Registered Users Posts: 35 ✭✭
in Advanced Solar Electric Technical Forum #1
I have 8 -12  volt batteries. I believe I made the mistake of hooking them up wrong or not the best way. I have 4 sets of 2 batteries equaling 24 volts. I believe I should have done 2 sets of 4 batteries in parallel for best results. Is that correct. Can you point to a wiring diagram for that set up. I believe that it is positive to positive for the 4 then negative to negative for the same 4. Then Positive to negative from the 2 sets. I have a busbar to connect to. I don't feel very comfortable without a diagram. Please help. 
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #2
    http://www.smartgauge.co.uk/batt_con.html

    Lots of info on battery wiring... may be helpful.
    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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  • BB.
    BB. Super Moderators, Administrators Posts: 33,622 admin
    #3
    Personally, I prefer to connect the batteries in a series string, then connect the multiple series strings in parallel (with 3 or more parallel battery strings, I highly recommend that each string be fused to protect against short circuits).

    Yes, you can connect the batteries in parallel sets--But I believe that these are a bit more difficult to maintain/debug... With series connected strings, you can use your volt meter to measure the voltage across each battery and quickly get an idea of the batteries health.

    If you connect the batteries in parallel, then series--Several good parallel batteries can "hide" failing cells/batteries.

    Poster 2ManyToyz has a nice set of pictures for his Do It Yourself solar power evolution (lower right side of website):

    http://2manytoyz.com/

    My other suggestion is to get an AC/DC Current Clamp DMM (digital multimeter). Here are a couple that range from very inexpensive to mid-range (or you can invest more money in a Fluke or similar high end meter):

    https://www.amazon.com/gp/product/B07546L9RT
    https://www.amazon.com/gp/product/B019CY4FB4

    Note that there are many AC current clamp meters (and they are very goo)--But they only work with AC current. For your battery system, you need a DC current clamp meter (most of whom can do AC current too)--Very nice for debugging and understanding your system. These meters can measure small to large amounts of current, and are very safe to use (you have a "plastic" clamp that clips over an insulated cable--No exposed wiring connections needed. And very good for monitoring series/parallel strings of batteries (look for roughly equal charging and discharging current on all strings).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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