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7 years offgrid - possibly has an opinion or three

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  • 7 years offgrid - possibly has an opinion or three

    Hi Solar Panel Enthusiasts
    I joined solarpaneltalk forums for the VIGOROUS debate about NiFe batteries.

    Warning: the following may seem a bit of a techno word salad....

    My offgrid system: 2000W (16x120W Sharp) PV, Exide EnergyStore FLA 24V 1500Ah@100hr, Honda Eu20i @1.5kW
    Outback Power components: FLEXmax 80 MPPT CC, VFX 3024E 240V Inverter, FLEXnet DC monitor, MATE controller.
    Installed with 1500W PV / MX60 in Nov 2006. Upgraded to current config (+FM80, +FNDC) at end 2010
    to run 2.55Kw reverse-cycle air-conditioning (very high efficiency EER 5.2 / COP 5.2) for 25m^2.
    Location: 37°S in Victoria Australia.

    Daily production logging software written by self[*]. See this website [**] for daily production logs:
    http://summerswood.site90.net/solargallery/ --- Apologies if the website doesn't load properly.
    I think the free web hosting conflicts with hefty server cpu usage for create image thumbnails...
    Keep refreshing your browser window, it might load, eventually.

    In the next 5 years I will be upgrading our offgrid system again to 5kW PV for:
    whole house air conditioning (7Kw RC-AC) and charging some type of PHEV[***]

    Thus my interest in the option of replacing my current FLA battery string with NiFe.

    I have a lot to say and more importantly I have all the data logs to back up why I dislike FLA batteries.
    I travel to Germany to attend RE conferences, to inject some interesting information into these discussions.
    [*] What else would a retired software engineer do but write extensive solar monitoring software as a hobby?
    [**] When my logging website goes away, I will update the link as a comment to this thread.
    [***] Plugin Hybrid Electric Vehicle

    -- A day without NUCLEAR FUSION is a day without SUNSHINE !

  • #2
    Welcome aboard. Don't think you'll find too much energy around for a continuance of the NiFe debate, but for what it's worth here's my $0.02 conclusion I came to....

    You have to hammer the NiFe batts with charge voltage to pack a decent amount of current in them. Other than the initial investment $$, this (or rather what is causes) is the single biggest issue you will face. In my experiments it caused both excessive water consumption due to electrolysis, and also peaked my kW-hr efficiency at a bit below 75% due to the charge / discharge voltage differences (which can easily get worse at high discharge rates due to voltage sag). Couple that with ~80% amp-hr efficiency since you will most likely only operate at the top end capacity of the cells due to warranty, and your effective kW-hr efficiency can easily fall into the low-to-mid 60's. The technology is however very solid, and depending on your age they may well last you the rest of your life. Just don't let the battery sales guys blow too much smoke up your stack.

    I suggest you try talking with Mike90250 as he is the only person I know that is fully off-grid with the current NiFe batts that are available (~38 kW-hr worth if I remember right). I'm sure he'll give you an honest opinion about them. I only have a set of old C6's that are about 1/10th that capacity. They are now currently in use for UPS service, and I only experimented with them off-grid for about a year or so while forming my own opinion about the technology.

    Good luck and welcome once again

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    • #3
      Originally posted by Robert1234 View Post

      I suggest you try talking with Mike90250 as he is the only person I know that is fully off-grid with the current NiFe batts that are available (~38 kW-hr worth if I remember right). I'm sure he'll give you an honest opinion about them. I only have a set of old C6's that are about 1/10th that capacity. They are now currently in use for UPS service, and I only experimented with them off-grid for about a year or so while forming my own opinion about the technology.

      Good luck and welcome once again
      '
      Last time I looked, Mike was not accepting Private Messages, so you will have to start the dialog in the open Forum. But the first thing you should do is search (using Google with "site:solarpaneltalk.com" in the search string) for NiFe and Mike90250. (The search function built into the Forum is not very capable, but it will let you look at all of Mike's posts.)
      SunnyBoy 3000 US, 18 BP Solar 175B panels.

      Comment


      • #4
        Re: Welcome

        Originally posted by Robert1234 View Post
        Welcome aboard. Don't think you'll find too much energy around for a continuance of the NiFe debate, but for what it's worth here's my $0.02 conclusion I came to....
        Maybe I can recharge the debate...

        You have to hammer the NiFe batts with charge voltage to pack a decent amount of current in them. Other than the initial investment $$, this (or rather what is causes) is the single biggest issue you will face. In my experiments it caused both excessive water consumption due to electrolysis, and also peaked my kW-hr efficiency at a bit below 75% due to the charge / discharge voltage differences (which can easily get worse at high discharge rates due to voltage sag). Couple that with ~80% amp-hr efficiency since you will most likely only operate at the top end capacity of the cells due to warranty, and your effective kW-hr efficiency can easily fall into the low-to-mid 60's.
        Sounds a lot like my over-fizzy FLA string with these characteristics:
        Average DoD is 7.5% - original daily budget of 5kWh from battery slashed to 2 Kwh/d. Because efficiency.
        Average charge/discharge efficiency is poor: 45% summer, 60% winter. Because low DoD.
        Water consumption is high, fill up average 6 weeks and trending up 15% per year. Because top of charge curve.
        (Afternoon float voltage is time to run water distillation = zero cost for battery water)
        (Everything is logged and my arcane scripts wring surprising trends out of the data logs)

        Thus probably not much operational difference with NiFe, except not having to get them to 100% every cycle.

        Thanks for the warning about NiFe sales tactics. I wont' "drink the kool aid" (a really poor joke, I know).
        However I look forward to rebutting some of the more egregious statements of the "lead heads".
        As a graduate chemist, the KOH changes aren't scary.
        The challenge of mitigation of CO2 absorption by KOH is an most interesting problem to solve.

        I'll close this discussion here as I am sure to find some threads that are better for detailed discussions.

        JS

        Comment


        • #5
          Pick it back up here if you dare

          http://www.solarpaneltalk.com/showth...3478#post93478

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