desperate - diagram 8 -12v bats in 24v bank

gwoods
gwoods Registered Users Posts: 1 ✭
in Off Grid Solar & Battery Systems #1
I’ve been trying to understand battery pack instructions and diagrams; I’m an Ironworker Contractor, I've erected structural steel buildings for 40 years but I'm not an electrician of any sort. As a home project, I’m building a solar generator with 8 Deep Cycle AGM Sealed Lead Acid 27 Batteries charged by 6 – 160 watt solar panels.
I would really appreciate some help with how best to wire the 8, 12 volt batteries into a workable 24 volt bank. I've read several different, best, methods but I'm barely familiar with terms like parallel and series and amp hours so what I really need is a diagram showing the 02 wire battery to battery leads.

The more I look for diagrams online the more confused I get; I've got it all built except connecting the batteries to the inverter - please help me with this? Thank-you, Gordon L. Woods Empire Steel LLC  gwoods.empiresteel@gmail.com 
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
    1) it's "possible" BUT you will end up with a massive 4 parallel bank of batteries, which seldom share the load or charging well

    If you have any chance to exchange the 12V batteries for 6V batteries - that would be the best thing

    If not, keep this in mind, the charger cables and the inverter cables, all connect to the same + & - posts
    This page explains how to best wire up parallel batteries.  Method 4 is likely the simplest.
      each "battery" they show in the sketch, would be 2 of your 12V  ( or 4, 6V ) batteries
    http://www.smartgauge.co.uk/batt_con.html

    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 ||
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,485 ✭✭✭✭
    #3
    Try to ensure the battery cable length from each of four strings is the same length.  Connect pos and neg at opposite corners.  Any small amount of resistance delta will increase current distribution mismatchng between the four battery groups.

    Don't expect better then 15-25% current matching from four parallel strings so restrict maximum discharge or charge currents accordingly.
    It is a good idea to get a DC clamp-on ampmeter so you can periodically do a quick check the current balance between battery groups.
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  • alexj
    alexj Registered Users Posts: 25 ✭✭
    edited January 2021 #4
    The Smartgauge link that Mike shared is really good. Here is some more info and diagrams:


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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,894 ✭✭✭✭✭✭
    edited January 2021 #5
    The second best thing is 2 strings of 6V AGM. The best thing is 1 string of 400 AH L16 AGM's. I am guessing 400ah is what you want?
     Probably will cost less or the same than the 2 strings 6V AGM. It will be simple to wire and zero chance of string imbalance.

    They are sold in the store here and below is a link.
    https://www.solar-electric.com/fullriver-dc400-6-agm-sealed-battery-6v-415ah.html
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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