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Why would one choose to have 6 batteries of 2 V 200 Ah connected together in a series connection instead of a single 12 V 200 Ah battery or the other way round?

From my calculations they all give you a total of 2400 Wh of energy and so it made me wonder what the differences are. I have used both in my house with solar panels and have not noticed any differences.

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    \$\begingroup\$ The both give 2400 watt hours. That's very different from 2400 watts. \$\endgroup\$
    – JRE
    Sep 6 at 10:59
  • \$\begingroup\$ thank you, couldn't find answers there. \$\endgroup\$
    – Nura
    Sep 6 at 11:00
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    \$\begingroup\$ You are aware that a 12V lead acid battery is simply six lead acid cells in one box right? \$\endgroup\$
    – JRE
    Sep 6 at 11:00
  • \$\begingroup\$ that's why I'm asking, it just seemed kinda unnecessary to have 6 batteries connected together when you can just have one battery do the same thing. btw I'm kinda new to al this so my knowledge of electricity isn't that much. I'm learning as I go. \$\endgroup\$
    – Nura
    Sep 6 at 11:03
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    \$\begingroup\$ From my calculations they all give you a total of 2400W of power That's not how that works. The 200 Ah is the capacity which tells us the amount of stored energy. It does not tell us how much power (energy per time unit) the battery can deliver. Often batteries with higher voltages (more than 4 V) are build using several cells in series. The voltage of one cell is determined by the battery's chemistry. If your chemistry (like Lead-Acid) gives you 2 V per cell but you want a 12 V battery, you have to connect 6 cells in series. \$\endgroup\$ Sep 6 at 11:07
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If the 2C cells are as well matched (unlikely) as the 12V cell , the it is the same, otherwise without an active Charge balancer, the weakest cell will age the fastest with runaway over/under charge with much lower MTBF.

If they are matched same or better, then it is the same energy storage.

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  • \$\begingroup\$ I'm sorry I don't understand what you're saying. \$\endgroup\$
    – Nura
    Sep 6 at 11:06
  • \$\begingroup\$ If you charge up 2Vx6 to 14V They will not be equal over time and the aging accelerates when over or undercharged from smaller capacitance. \$\endgroup\$ Sep 6 at 11:17
  • \$\begingroup\$ read on Peukert's Law \$\endgroup\$ Sep 6 at 11:27
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Note Amperehours (Ah) is a unit of capacity and not current ; when multiplied with Volts the result is Watthours which is a unit of energy and not power.

12V lead acid battery is built with 6x 2V cells in series.

You'd use individual cells if...

  • you need a different voltage than 12V, that requires a number of cells in series that is not a multiple of 6

  • long term maintenance is more important than low number of parts, for example you can use extra hardware to balance the cells to make sure the cell with lowest capacity does not overcharge/overdischarge and die, you can also monitor each cell and replace the ones that go bad instead of replacing a complete battery, etc.

  • reliability: say you have 12 cells.

You can make 2x 12V batteries of 6 cells each, and wire the batteries in parallel.

You can also wire the cells in parallel (making 2V cells with twice the capacity) then wire these combined cells in series.

In both cases you get 12V and capacity is twice the Ah rating of the cells.

In the first case, the weakest cell of each battery will die first. When one cell dies in a battery, the whole battery becomes unusable, so this means when the two weakest cells die, both batteries are unusable, and the whole system dies.

In the second case, the weakest cells will also die first, but they will probably not be wired in parallel. So, two of your parallel 2V cell bunches will only run on one cell, which means the capacity of the whole system will be halved, but it will still be usable until you replace the dead cells.

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  • \$\begingroup\$ very detailed. thanks \$\endgroup\$
    – Nura
    Sep 6 at 11:15
  • \$\begingroup\$ I understand it now, 1. but let's say you have the hardware to balance the charge, long term is it going to be easier and cheaper to maintain? say you have 2v x6 instead of a single 12v? 2. which of the two will last longer? \$\endgroup\$
    – Nura
    Sep 6 at 11:23
  • \$\begingroup\$ Well a 12V battery only has two terminals so you can't touch the cells inside to balance them and monitor them. \$\endgroup\$
    – bobflux
    Sep 6 at 12:09
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Those 2V 200Ah are different technology, they have thicker plates. They also have more cycles, they are made for professional use. You will hardly get them on free market, the company will give the guarantee only if proper mounted (by them). They are not filled with acid, it is poured in-situ, they are expensive.

On the other hand you have a consumer battery 12V 200Ah, but it can't compare in quality, duty, clcles...

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  • \$\begingroup\$ thank you very much. So basically as a consumer I should only get the 12v 200ah batteries. Also no wonder the other one's were more expensive. \$\endgroup\$
    – Nura
    Sep 6 at 11:12
  • \$\begingroup\$ 2V Ceramic plate batteries used in computer rooms and Telco's weigh 200 kg and are expensive but 200Ah gel-cell 2V batteries are cheap $40. The difference is in tolerances of Ah capacity ESR and C value and quality \$\endgroup\$ Sep 6 at 11:22
  • \$\begingroup\$ Which one are higher quality? @TonyStewartEE75 \$\endgroup\$
    – Nura
    Sep 6 at 12:24

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