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Battery Bank Type and Size

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  • Battery Bank Type and Size

    So Batteries, 1000 year old technology and still essential.
    The right size will be found with practical experience living on the seastead for some extended time.
    A 80AH car battery is more or less the lower range emergency use the max size is determent by the controller/array and somewhere in the range of 800AH.
    The type is a much harder choice. Size, if not enough another one is added, simple.
    Wrong type, if replacement is called for the entire bank needs replace and possible controller as well because Gel, AGM, conventional lead-acid, Li-ion, LiFePO4, NiCd, NiZn, NiMH, Home made Salt water battery......... are not interchangeable.
    Huge differences in price, weight, energy density.....
    Also the border line between Batteries and Capacitors has become very blurry in recent times. Commercially available supercapaciors are still outrages expensive, home made carbon based capacitors on the other had are cheap as. Not real a choice right now as untested and a lot of work to make. Charge time is very fast and retain energy for days.
    Storage is another issue as some need venting others dont. Lead-acid possible by far the cheapest choice but to many negative for the seastead, maybe.
    I am not really up to date on the battery issue as i consider it a road to nowhere.

  • #2
    Agree about the "road to nowhere." Even so, they are attractive for temporary use in small installations. The best type that has existed so far is the alkaline Edison cell, or nickel-iron battery. They used to be available on the surplus market because the telephone company used them for station batteries. As far as I know this practice has ceased and the batteries are available commercially only from Chinese suppliers. I don't know if their durability is similar to that of the old Edison cells, which used to last for generations.

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    • #3
      Seawater battery technology is also something to consider: https://phys.org/news/2017-02-eco-battery-seawater.html

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      • #4
        Game changers are super capacitors. Fully charged in minutes unlike batteries hanging on the chargers for hours.

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        • #5
          Tesla batteries (or significant fractions of a Tesla battery pack) seem like a good idea to me for the same reason they're good in the cars. Sealed, deep cycle, long life, no need for ventilation, no having to top them off with water, high density (relative low mass and volume for the amount of storage) and so on. They're apparently pretty cost-effective, too, though I don't know how much it would cost to ship. They're being used by people with off grid houses and RVs now.
          Last edited by destinal; 03-04-2019, 11:48 PM.

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          • skipperzzyzx
            skipperzzyzx commented
            Editing a comment
            I like Tesla.

        • #6
          Originally posted by destinal View Post
          Tesla batteries (or significant fractions of a Tesla battery pack) seem like a good idea to me for the same reason they're good in the cars. Sealed, deep cycle, long life, no need for ventilation, no having to top them off with water, high density (relative low mass and volume for the amount of storage) and so on. They're apparently pretty cost-effective, too, though I don't know how much it would cost to ship. They're being used by people with off grid houses and RVs now.
          Bang for the buck with lithium-ion cells as used in Tesla or a lot of mobile phones is bad. $400 per kWh.

          Pressure may be worth looking into of storing lots of cheap energy on a seastead. For every meter a floater is pushed down = 1 bar

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          • #7
            I suspect it will be less work to just buy lithium ion batteries designed for homes and boats, but seasteads are a pretty good use-case for near-isothermal Compressed Air Energy Storage (CAES). https://en.wikipedia.org/wiki/Compre...energy_storage

            To store energy, run an air compressor. Store the air in bladders anchored to the ocean floor with heavy weights. Unlike tanks at sealevel, these bladders can have the same pressure as the ocean at depth (say, 100m => 1 MPa), so they can be made far less expensively to store more energy for the cost. To recover energy, use the compressed air to drive a turbine and generate electricity. There are off-the-shelf systems you can buy that already do this.

            Heating during compression and cooling during expansion both eat into the round-trip efficiency. That's where "near isothermal" comes in. You have a massive heat sink in the form of the ocean, so cooling air with seawater during compression and warming it during expansion improves efficiency in both directions.

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