Wiring 4 batteries on two levels

Tradiscantia
Tradiscantia Solar Expert Posts: 35 ✭✭
in Solar Beginners Corner #1
Hey Guys,
We built a battery rack to stack our four 6v flooded batteries on the tongue of the trailer between two storage doors and now we have to figure out how to wire them. Here's a picture of the set up. Sorry the picture ended up rotated. Wish i could figure out how to turn it.
Attachment not found.

We have read that there should be cables of equal lengths attached the batteries in series and in parallel. We have looked at various online wiring diagrams, but can't figure out how to get the equal length with two levels, unless we have longer than needed cables.

How important is it to equalize the length of all the cables?

Could we have equal cables to the two in series, and equal cables to the parallel groups and still charge and draw from the batteries equally?
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Comments

  • Puppel
    Puppel Registered Users Posts: 4
    #2
    Re: Wiring 4 batteries on two levels

    Here's the correctly oriented picture
    Attachment not found.
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  • Tradiscantia
    Tradiscantia Solar Expert Posts: 35 ✭✭
    #3
    Re: Wiring 4 batteries on two levels

    still sideways. The forum program keeps turning the picture.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,642 admin
    #4
    Re: Wiring 4 batteries on two levels

    Keeping cables short is always a good idea--But as long as they are heavy enough to carry the expected current without too much voltage drop, you should be fine.

    And, the individual cable lengths do not have to match--(i.e., cable #1 on bank A does not have to be the same length as cable #1 on bank B). The total length of bank A cables (from +bus through battery back to -bus) needs to be roughly the same for both banks (same resistance for each wire run helps prevent current imbalance between the two banks).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: Wiring 4 batteries on two levels

    Software seems to have a problem with the original picture dimensions.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #6
    Re: Wiring 4 batteries on two levels

    OK, I know it's done, but how on earth are you going to check the water levels in the bottom batteries?

    As to wires, so you connect he top 2 as a set and the bottom 2 as a set, with the same length wires and you connect the top set to the bottom set and attach the wires to your system one off the bottom and one off the top.

    When you connect the top set to the bottom set, use cables that are at least a foot longer than needed so you can slide the bottom batteries out to check the electrolyte levels. If you want to check them 1 at a time you might use 16" cables between the batteries on both levels. I'm sure you could do the math, but if you wanted a shorter cable connecting the top 2 batteries, I would suggest a gauge thicker wire for each doubling of the wire length for the longer wire. So if your using a 4 gauge 8" wire connecting the batteries on the top, use a 2 gauge 16" wire on the bottom. That should get you close on the resistance.
    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.
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  • Tradiscantia
    Tradiscantia Solar Expert Posts: 35 ✭✭
    #7
    Re: Wiring 4 batteries on two levels

    We thought of adding the water problem and made the bottom tray slide. We had no choice due to the position of the access doors to the storage compartment.
    However, you raise a good point, Photowhit, as he was thinking of disconnecting the cables to add water. We like your idea of doubling the top to bottom cable length with thicker wire. Thanks! this board rocks!
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  • Tradiscantia
    Tradiscantia Solar Expert Posts: 35 ✭✭
    #8
    Re: Wiring 4 batteries on two levels

    Next step:
    Find cables the right length?
    Or is it cost effective and time effective to buy the wire and attach our own ends (we don't have a crimping tool so that would add to the cost if we do it ourselves.)
    If we follow Photowhit's advice, we'll use #2 from top level to bottom and #4 AWG between levels and #2 to the inverter (longest run -- 3-4 ft) and ??? to the 12v distribution panel? Same as to the inverter? Or can we use the #4 AWG since we don't have a lot of stuff on that panel (no slides, no AC, just lights, propane furnace, CO2 monitor, 12v cigarette lighter plug)
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