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Is wiring 6v batteries to make a 48v system practical?

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  • Is wiring 6v batteries to make a 48v system practical?

    Just like title says. Is it practical? (Besides 48v being practical in terms of using smaller gauge wiring)
    I understand in this case one would need 8 6v batteries wired in series.

    And...

    Are there advantages/disadvantages over 4 12v batteries wired in series(also 48v total)?

  • #2
    The advantage over using four 12V batteries, is you still have the same size battery cases, but more amp hour storage (8 golf cart batteries)
    Powerfab top of pole PV mount (2) | 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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    • #3
      You could also consider 24 X 2 volt cells for even more battery storage. depending on the size of the system you demand, 6 and 2 volts batteries in series may be a necessity.

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      • #4
        Not only practical, but common proper practice. Here is the deal, never ever parallel batteries unless it is absolutely necessary, and unless you need more than 6000 AH, it is not necessary. Does not matter if we are talking 2 or 600 volt batteries. Now you may not understand, but your back and a$$ will understand perfectly. Lets say you need a 48 volt 250 AH battery. What do you use? Well if you are stuck inside a 12 volt box like most you go looking for 12 volt batteries. Quickly you discover there are no 12 volt 250 AH batteries, all you can find is 80 AH to 100 AH 12 volt batteries. Now you may not know why there are no 12 volt 250 AH batteries, but you backside does.

        There is a direct correlation of weight to energy ratio of any material or substance. Example a pound of uranium can power a large city for weeks, or a pound of batteries to power your laptop for a day. Lead acid batteries are no exceptions and there is a scientific name given for it called Specific Energy Density expressed as [U]Watt-Hours / Kilogram[/U]. Lead acid batteries in US Citizens terms is roughly [U]25 watt-hours / pound[/U], or the rest of the world is [U][I]55 wh/Kg[/I][/U].

        To find a battery [B]Watt Hour Capacity = Nominal Battery Voltage x Amp Hours[/B]. By now I bet your backside has figured it out, if you have not figured it out yet, keep reading. A 12-Volt 250 AH battery, if you can find one, would weigh how much? Well to find out first determine how many watt hours there are. 12 volts x 250 AH = [B]3000 watt hours[/B]. We know a battery weighs 1 pound for every 25 watt hours of capacity, so your backside already figured out it weighs 3000 / 25 = [U]125 pounds[/U].

        Care to guess what a 6-volt 250 AH golf cart battery weighs and how many it takes to make 48 volts? Ask your backside, it learned from an A$$hole called SK. Those 6000 AH batteries I speak of are 2-Volts and require a lift to handle.
        Last edited by Sunking; 08-12-2018, 11:45 AM.
        MSEE, PE

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        • #5
          Weight is a very good point! Something to consider on off-grid situations where walking to get to the spot is part of getting to the structures.(Personally my case. When the time comes I'll use a cart/dolly... probably do a few trips without it, train grip, shoulders and traps).

          Now, on the 48v system using eight 6v vs 48v system using four 12v, when it comes to wiring, you'll need more wires when using 6v batteries, resulting in more connections. Negligible? I believe it is so, at least for smaller systems that use less batteries.

          And about having a single line in series VS having two rows, the latter allows you to run the same voltage by disabling one row until you find a replacement for that one faulty battery causing trouble in the whole system. With the former you're shut down until replacement arrives.(This is what I read somewhere. Makes sense)

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          • #6
            A query to post #4 above, why should one "[LEFT][COLOR=#252C2F][FONT=Helvetica][SIZE=13px]never ever parallel batteries unless it is absolutely necessary..."? Is the reason the weight of the battery alone or are there other reasons? [/SIZE][/FONT][/COLOR][/LEFT]

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