Wiring more then 4 batteries in parallel?

ollyomm
ollyomm Registered Users Posts: 10 ✭✭
in Solar Beginners Corner #1
Hi guys, I've been staring at this picture for an hour now and I cant figure out how this could be applied to 6, 8 or 12 batteries, I know the ideal is a splitter bar but am looking for alternatives.
Thanks in advance
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2
    Are you getting the batteries free? Higher system voltage or larger capacity batteries may save you money in the long run.

    It's just a pain to get equal resistance across so many batteries in parallel. 

    If you must a bus bar can be had pretty cheap. from Lowes/ Home depot;

    Something like this from Home Depot, if you are using some small batteries. I think the small are 4 gauge and the large 2/0
    Perhaps you could devise your own insulator for this;
    Eaton 14-Terminal Ground Bar Kit

    https://www.homedepot.com/p/Eaton-14-Terminal-Ground-Bar-Kit-GBK1420CS/100199885?MERCH=REC-_-PIPHorizontal1_rr-_-302610360-_-100199885-_-N
    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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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #3
    It looks like it's a pair of pairs (2^2=4). With 8, it would be a pair of pair of pairs (2^3=8). Each balanced group is iterated as a single battery in the next parallel connection, which is itself cross-connected to maintain balance. 2^4 would be 16 batteries, and so on.

    If I'm understanding the idea properly, it needs to be even powers of two, so 6 or 12 wouldn't work. I may well be misunderstanding the idea though.

    Although this might theoretically give equal resistance, in real world field wiring I suspect it would be difficult to avoid differences. With more batteries in parallel, the odds of differences would increase, as would the likely range between high and low resistance wire/connections.

    IMHO, the ideal would be a single series string, or at most two series strings in parallel.
    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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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #4
    Method 3 from the Smartgauge website where the image was taken from, could be used for any number of batteries even odd using a bus bar, as suggested by Photowhit, much simpler. The method 4 you refer to seems over complicated for no gain, which ever method is chosen it would be advisable that each battery is fused to prevent a failure of one being fed by all the others, as well as constant monitoring of current of each battery during charging and dischargeing to ensure ballance.
    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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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #5
    Even using identical lengths of cables, well crimped, does not always work, as there is variation and even bolting lugs onto terminals is another variable.   At some point, even busbar won't solve the problem, because of internal variations in the batteries themselves.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • ollyomm
    ollyomm Registered Users Posts: 10 ✭✭
    #6
    Thanks for your help guys, batteries are close to free, 6$ for 39ah gel batteries that appear healthy, most with resting voltage of 12.9 after a few months. So just seeing what can be done and how long they might last as a bank. Also have access to heavy duty scrap wire from a friend. Almost tempted to solder to the battery terminals but will try soldered ring terminals first. Will go a splitter bar. I just liked the theory of the image
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #7
    Please don't solder to battery terminals, you will ruin the seals and then have junk
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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