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PNJunction. Some Food 4 Thought

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  • PNJunction. Some Food 4 Thought

    That test was just released two days ago from Power Stream charge and discharge test on 26650 LFP cells from 4 manufactures, and a LiPo thrown in for good measure. In a nutshell there is no reason to charge higher than 3.4 vpc as there is nothing to be gained and going above only results in shorter cycle life. If you look at the Discharge Curves there is almost no difference in capacity if charging from 3.4 to 4.2 vpc. It goes on to say charging to less than 3.4 vpc greatly extends battery cycle life. Sorry to have to print out the link, but as you know the form software is trashed. __________________________________________________ __________________________________________________ ____________________________ http://www.powerstream.com/lithium-p...ge-voltage.htm
    MSEE, PE

  • #2
    FWIW, you can still manually embed hyperlinks in other text, using the URL tag

    <left bracket>URL="http://www.yourlinkhere.com"]clickable text[/URL]

    just replace <left bracket> with a [
    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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    • #3
      Originally posted by sensij View Post
      FWIW, you can still manually embed hyperlinks in other text, using the URL tagURL="http://www.yourlinkhere.com"]clickable text[/URL]just replace with a [
      Yep, but I am lazy
      MSEE, PE

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      • #4
        Yes - it really is as simple as just staying out of the knees. This is made much easier by not undersizing your bank to begin with, and not thinking in terms of 100 - XX% DOD as your operational cycle as one does with lead.

        I am not too fond of the information on that site and the way it is presented. We'll start with lead acid that has bugged me for YEARS and move forward ...

        This is the same source that also promotes "fast charging" agm's without taking into account the manufacturing process and composition of the agm, usually a lead-calcium. What works ON PAPER mathematically, does not always translate into the real world. They leave out VERY important information about how the the chemical composition of a typical lead-calcium agm's electrolyte and paste cannot handle such abuse for long periods of time without creating hot-spots to come back and haunt you later with thermal runaway. Yet seen only from a mathematical standpoint it makes sense.

        You know, I did just this to join their conspiracy bandwagon. I hammered batteries not designed to take that, and what do you know - after repeated cycling, the IR handheld thermometer told all when scanned across various parts of the cells when they were being fast-charged beyond their design limits. INFO FAIL

        There is a reason that conventional agm's usually have a 0.25C to 0.3C max charge rate, and that is to promote the *controlled* process of recharge desulfation. Do it too fast, and you clump and create levels starved of material to handle that charge effectively. In fact, like all batteries, you can even do this to LiFePo4 when you exceed their max rated amperage.

        You know what, I was going to tear into their sloppy lifepo4 presentation too, but I'm not going to waste my time with it.

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        • #5
          I guess I'm back on a generic standpoint

          When we buy batteries, we generall get them with some sort of pedigree behind them. Deka / Crown / Rolls / Enersys / Concorde / GBS / Winston / CALB / A123

          But experimenters buying cells, usually small, need to know WHO and what is the pedigree behind them? What exactly IS inside that black box with a label slapped on it? Is it A123, Kokam, or something generic? This applies not only to the small cylindricals, but also to any "large prismatics" that are offered.

          What I deal with are batteries with a known history behind them, typically large prismatics in the lifepo4 arena, which can handle our application well with a touch of conservatism.

          However, with unknown cells, you may be FORCED to use a full-time balancer as a life-support system on lesser quality stuff, despite your best efforts to be conservative. This can be exacerbated by throwing a bunch of 18650's or 26650's into a plastic box. You don't know WHAT is inside, unless you get it from a quality manufacturer like A123.

          Even the powersports lifepo4 industry is subject to this, who usually use multiples of 26650's. They may start out with A123, but for one reason or another may switch to a different manufacturer, which may or may not be up to snuff. You just don't know unless they specifically tell you - and even if they did, can you as an average consumer know what using a "Fireball 3000" inside means from a quality standpoint?

          I'm tellin' ya guys - if you lowball your solar system, whether it is lead or lifepo4, don't blame the technology right off the bat, or expect reasonable support for such.

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