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

gwoodsgwoods 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  [email protected] 
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  • mike95490mike95490 Solar Expert Posts: 9,582 ✭✭✭✭✭
    #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

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  • RCinFLARCinFLA Solar Expert Posts: 1,460 ✭✭✭✭
    #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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  • alexjalexj 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 AngeliniDave Angelini Solar Expert Posts: 6,147 ✭✭✭✭✭
    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 Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

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