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  • LIOH function and charge efficiency

    I'm hoping with this thread to pin down actual function of lithium hydroxide in an NiFe cell, and expose some of the rationale for the amount added and it's cost effectiveness.
    I welcome comments with citation over uninformed (however assertive and determined) opinions based on heresay or unscientific assumptions that the value of this thread remain useful for others.

    I have more questions then answers myself, and mods permitting will link out to reference that *should* have weight of experience.

    It seems globally recognized that LiOH readily absorbs C02, my research so far has suggested that is the primary reason for adding it in solution to a NiFe battery.
    Lithium's higher electronegativity then Potassium results in a LiC03. (2LiOH + CO2 → Li2CO3 + H2O) rather then Potassium Carbonate. KOH + CO2 → KHCO3
    ref: http://en.wikipedia.org/wiki/Lithium_hydroxide
    Based on my limited experience with batch sheets and availability/cost/purity of KOH flake:
    http://www.solarpaneltalk.com/showth...ll=1#post36423
    I would suggest that the reasoning behind LiOH increasing the efficiency of ANY NiFe cell is primarily due to the purification of the "brand new" KOH flake which had impurities and KHCO3 to begin with. Given the batch I was provided, significant LiOH would be require simply to bring the KOH solution to a pure "no inherent carbonates" state.

    The chemistry of it however similar to that of a NiCad - suggests it is intended instead to preserve the Nickel (pos) electrode.
    ref: http://www.cadmium.org/pg_n.php?id_menu=14
    I see no reference to this reasoning elsewhere, but invite a reference if someone can offer one.

    The costs (referenced in batch sheet reference thread above) surely determine why even new NiFe batteries are shipped with LiOH as the purer forms of KOH and/or LiOH are excessively expensive. My KOH flake had (up to) .44% KHCO3 and sourced LIOH had (up to) 2% Li2CO3 in raw form.

    Given LiOH absorbs C02 and locks it up in a strong bond, why not simply schedule additional LiOH addition rather then replace electrolyte?
    Is there another reason to have LiOH in the electrolyte mix other then Carbonate absorption?
    Maybe:
    Improved heat transfer retarding HHO generation?
    LIOH acting in conjunction with KOH in Ni/Fe ion exchange?

    While some have suggested that graphing charge temperatures may be useful, they make no mention of source KOH batching purities and LiOH purities from the start.
    This could explain the wide variation in charging efficiencies touted by manufacturers and why many see NiFe as a lesser storage method.
    In a perfect world one might plan their electrolyte mix based on:
    1) KOH flake purity
    2) LiOH purity
    3) operating environment temperature (affecting KOH% required in solution ...- can find no reference to LIOH variation based on temp)
    ref: page 3 - http://ironedison.com/images/product...s%20Manual.pdf

    While I expect this to be a request for the holy grail, I invite anyone who can speak to these variables in a recorded referenced way.
    Again, opinions are great but data is easier to trust, please provide citation with your truths.

    Discuss...

  • #2
    While I'm not a chemist, I do appreciate the thread you have started, and will follow it with interest.
    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 ||
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    • #3
      Thanks for starting this

      I am awaiting shipment of 7.5Kg of LiOH right now, so that I can do an electrolyte replacement. I have pondered these same questions, and so I appreciate your having articulated them so clearly. I am a bit fed up with the uninformed anecdotes flying around.

      The postulate that LiHOH functions as a CO2 scavenger is very credible. I like the idea of simply adding aliquots of LiOH, instead of wholesale electrolyte replacement. Perhaps that could be an intermediate measure, to stave off a total change for a few years longer?

      The other big questions for me are related to this:

      1) Battery oil - yes/no? Type/Brand? The answer for me is "yes" at this time. I am using the oil shipped to me with my batteries from BUF

      2) How best to prevent CO2 infiltration? For me, the best information - if anecdotal - comes from reading EV boards. Specifically, with reference to Saft NiCd batteries. I found telling anecdotes about folks getting a large increment in total cycle life, by never opening their cells. This suggests to me that things like battery oil, and effective cap systems, might be very beneficial over the long haul, by preventing excessive CO2 entry.

      Again, thanks for starting this thread!

      Marcus
      (Changhong TN500 x 40)

      Comment


      • #4
        I've considered float oil as a possible source of both plate contaminants (excess water boil off causing plate coating by float oil) and a source for carbonate formation INSIDE the cell during charging whilst H, O, H2 and O2 are readily produced and bubble thru carbon bearing oil. I shant scold you for not providing links or basing your decision to use float oil on anecdotal reasons simply because I wish this discussed and there are few data based sources to justify such a decision. We're just now working on that...

        I have not found reference to the primary practice of a layer of float oil. It may well have been initiated by good intention only and is not referenced in the iron edison manual above, or the original manual by Edison: http://www.nickel-iron-battery.com/edison_brochure.pdf

        In the absence of data one must consider that there is risk of doing it wrong for a hundred years, because the experts who started doing it wrong got copied without question.
        Doctors stopped smoking in the examination room when the data told them it was prudent.

        Marcus278 - since you are planning an electrolyte swap, perhaps you may wish to take some records and put some data into the mix on this subject?
        Have you considered merely adding LIOH over replacing entire electrolyte? Again, cost of KOH is a fraction of LIOH in the reagent grade of things, but without records on the difference it makes it becomes expensive postulation (like 2.7k$ in your case?). Measuring charge efficiencies is not an easy thing with all the variables and effort required to do so accurately.

        Could you provide links to the reference you mention about extended life cycles for those who didn't open their cells? I would be interested in there maintenance stories, level of regular usage/discharge, or whatever else they could offer on history. I suspect the harder the batteries are cycled, the higher the risk of carbonates. I do think there is but one event that causes it in the absence of float oil though, and that's the cool down after a charge, when atmosphere has opportunity to balance negative cell pressure. I know my vintage cell valves have little chance of sealing positive pressure out. It just takes one crystal to break a seal.

        Does carbon bearing float oil provide more of an electrolyte seal then a working cell cap?
        Is it worth the risk of plate contamination, or HHO in-cell carbonate generation?
        Good questions and the answers are all speculation without proof.

        My decision to avoid float oil is based on the KISS method.

        Catalytic cells caps combined with clean functioning cell valves have my vote for carbonate protection. This allows for cell pressure balance by ingress of recombined HHO and adds the benefit of lowering water requirements. Catalytic caps however do not seem to be a manufacturer consideration although I was referred to changhongbatteries to source them when I queried Ian Soutar referenced on :
        http://www.nickel-iron-battery.com/
        I eventually located: http://www.hydrocapcorp.com/about.htm
        As a source for retrofit caps for my vintage NiFe cells. As I was just in KOH/LIOH source mode, I have not pursued it to cost qualification.

        This was prompted based on my limited experience with these caps:
        http://www.rolls-battery.com/content...specifications
        and how effective they are at retaining water in cells in comparison to those I have that don't have these caps.

        Comment


        • #5
          Apollo 13?

          Apollo 13 used lithium hydroxide canisters to purge carbon dioxide from the Lunar Module?

          http://www.ebay.co.uk/itm/4x6-Photo-...item1e5febb19c

          Comment


          • #6
            silicone oil/silicone fluid instead of float oil?
            http://en.wikipedia.org/wiki/Silicone_oil

            and or hydro caps?

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            • #7
              I have tryed 2 times to email www.hydrocapcorp.com about hydro caps for my nife cells but the email can not get through, unknown address error message.

              maby I will have to post a letter?

              Comment


              • #8
                I don't know whether the guy [Hydrocaps] does much or anything via the web. You need to call or write. He will respond very quickly.

                Comment


                • #9
                  NaOH instead of LiOH?

                  New to the tread folks,
                  I'm needing new electrolyte for my NiFE batteries. Wondering, if the use of LiOH is for the C02 scrubbing, then why wouldn't NaOH work?

                  Comment


                  • #10
                    Originally posted by sundowner View Post
                    New to the tread folks,
                    I'm needing new electrolyte for my NiFE batteries. Wondering, if the use of LiOH is for the C02 scrubbing, then why wouldn't NaOH work?
                    I have not seen any discussion of this, but if it worked and was cheaper I would expect somebody to have mentioned it already.
                    Possibly the other "benefits" of LiOH beyond CO2 scrubbing are not met by NaOH. Or possibly the electronegativity difference between Na and K is just not large enough for effective scrubbing?
                    SunnyBoy 3000 US, 18 BP Solar 175B panels.

                    Comment


                    • #11
                      Originally posted by inetdog View Post
                      I have not seen any discussion of this, but if it worked and was cheaper I would expect somebody to have mentioned it already.
                      Possibly the other "benefits" of LiOH beyond CO2 scrubbing are not met by NaOH. Or possibly the electronegativity difference between Na and K is just not large enough for effective scrubbing?
                      There was a link to an article (behind a subscription pay-wall, I haven't read it) posted in another thread last month about the role of LiOH. Apparently it is for reducing "iron poisoning", not for dealing with carbonate contamination.
                      http://www.solarpaneltalk.com/showth...-debate/page14


                      There was an interesting thread at this fieldlines site about using these cells for CO2 scrubbing (in a different sense) , presumably for ones private "submarine".
                      http://www.fieldlines.com/index.php/...146754.26.html

                      I was looking around the internet for sources of LiOH (My web search skills are not great though) and did see Lithium hydroxide monohydrate
                      ACS reagent, ≥98.0% , with Li2CO3 content <= 2% for $190 for 2 KG
                      As I don't have any contacts in the chemical industry, I don't know if this is a reasonable price or not.

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