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Is lithium ion battery technology still not there?

Discussion in 'Electronic Design' started by cameo, Feb 22, 2013.

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  1. cameo

    cameo Guest

    Boeing has a hell of a time with fixing its battery problem on the 787
    Dreamliner. I wonder if any of you had a deeper knowledge as to the
    cause and whether those batteries are just not yet a proven technology.
  2. Sylvia Else

    Sylvia Else Guest

    I think it's more just that they're an inherently unstable technology.
    Design them right, and they'll be OK, but it's easy to make mistakes,
    overlook things, etc., such that their inherent instability will lead to

    I wouldn't be building them into aircraft.

  3. hamilton

    hamilton Guest

  4. Guest

    "The [Japan] Transport Safety Board said in a report that the battery for the aircraft's auxiliary power unit was incorrectly connected to the main battery that overheated, although a protective valve would have prevented power from the auxiliary unit from causing damage."

    Boeing and NTSB found no such miswiring on the JAL 787 where APU battery caught fire. ANA fire Japan is investigating was the EE-bay main battery, notthe APU battery.
  5. T

    T Guest

    It's turned out not to be the battery but instead a wiring fault.
    Imagine that.
  6. Sylvia Else

    Sylvia Else Guest

    There was a wiring fault. That doesn't mean it caused the battery to
    catch fire. Indeed, were a wiring fault capable of doing that, one would
    have to feel that the design had no business being in the air.

  7. Guest

    "T" stands for troll.
    No such wiring fault has been found or confirmed. JTSB is under extreme pressure to find an answer, the best they have come up so far is an "appearance" of miswiring through a protective "valve"- yeah, rght.
  8. TTman

    TTman Guest

    I subscribe to that too.... Having seen far too many 'incidents' with RC
    LiPos catching fire/bulging etc.
  9. Yzordderrex

    Yzordderrex Guest

    The Lithium-Ion battery is a logical choice for the application. I would be cautious as to diagnosing the problem just yet. Certain lithium battery chemistries are more prone than others to fail with a fire. The battery inthe Dreamliner (if my intel is good) is of a chemistry that would be better suited to remain on the surface of the earth. Failures could be a resultof a few different scenarios, including a faulty cell to begin with, overcharging, and certainly mis-wiring the battery or a faulty BMU or charger board.

    I'm sure we will have an answer soon, although an answer grounded in reality may never arrive. Just the way these things work out.

  10. Guest

    "T" is for troll, eternal-september troll.
    Those are required by international regulation, they're not a nice-to-have the manufacturer decided to add.

    That guy can't utter three buzzwords without looking down at his cue card. All he's doing is trying to figure out how he can issue a decision based onsome other authority he can eventually scapegoat if it turns out to be wrong.
    Nah- it runs much deeper than that. You would be seeing a helluva lot more than just two fires in 100,000 hours with that kind of defect. The batteries are cycled through simulated altitude testing, again by international regulation. Do you think anyone in their right mind would use a battery in a high altitude aviation application without designing in that kind of ruggedness?

    In other news, JTSB did announce a few days ago that the second battery in the subject ANA 787 was found to be "swollen" too.
  11. Guest

    But those failures are supposed to result in a dead battery (open ckt) and not fire, venting, or smoking. The safeguards against catastrophic failure, at least four internal to the cells, failed.

    Don't count on it. Boeing is already working on designing it out of the system. United has removed the 787 from their flight plans <hint hint>. Now wait for the "out of an abundance of caution" bs from Boeing public relations.
  12. Yzordderrex

    Yzordderrex Guest

    Not sure where you are getting your info, but open circuit failure of a Li-ion battery probably isn't going to happen. The particular recipe that the787 is using is notorious for catching fire. Newer designs used to spin up the turbines to light them off use a much more air-worthy chemistry

    The batteries are not stuffed into the package like a can of sardines waiting to expand and catch fire. if you take a look at one of these assembliesyou will see there is room to drive a small truck between rows of cells.

    And yes, I agree, the batteries in the 787 will most likely be replaced by the end of the year with more forgiving units.

  13. Yzordderrex

    Yzordderrex Guest

  14. Robert Baer

    Robert Baer Guest

    Those batteries are a "proven" technology.
    However, use has shown that they are not only temperature sensitive,
    but that they are prone to thermal runaway; energy density so high as to
    cause fires - just like gasoline which has even higher energy density.
    Now there is a newer Li formulation that is NOT as temperature
    sensitive, and seems to NOT beprone to thermal runaway.
    Was not available back in the dinosaur age when the battery choice
    was made.
  15. Robert Baer

    Robert Baer Guest

    Methinks they put themselves between a rock and a hard place..the
    Dreamliner MANDATE was to make _everything_ as light as possible,and
    that stubborn attitude ruled out Lead-Acid and Nickel-Silver formulations.
  16. Guest

    Things like shut-down separator, tear-away tab, and thermal circuit interrupters are intended to make the battery an open circuit, some permanently. The first line of defense is the separator, a layer of which melts near thermal runaway, and blocks all ion flow between electrodes. The others are backups. You're right, but not the way you think, "open circuit failure" /is/ "probably not going to happen."
  17. Guest

    Okay, but the pressure relief valve is supposed to vent well before the internal pressure gets to the point of puncturing the separator. If they have fire, they have separator failure, it's that simple. The separator is supposed to fuse its pores shut permanently /before/ thermal runaway temperatureis reached, and it does this on the dimension scale of microns. You can't have thermal runaway with a working separator. There are a few things that can happen to defeat the separator, like dendrite growth and pore blocking contamination, or it can be overvoltaged when fused, to the point of havingenough leakage to sustain thermal runaway, and who knows what else. Supposedly the Yuasa prismatic package which uses a 10 meter length of separator is unprecedented.
  18. Guest

    Right, but the separator protection kicks in at 130oC which is well before the temps shown on the curve. The separator is an inner ply of 10u thick polypropylene porous film sandwiched between two 10u porous polyethylene film sheets.
    Apparently there are quite a few variations on lithium ion, but of them all LiCoO2 offers the highest energy density.
  19. Guest

    Huh? There's no such thing as a Lithium battery without a separator. One of the news reports showed it unwrapped on a long bench at the NTSB materials lab.
    The internal short is what you get when the separator fails.
    I think that upgrade went by the wayside, all the battery consultants who know about the Boeing design say they're LiCoO2.
    That's exactly what they're doing.

    This individual is the one who doubts Yuasa, or any manufacturer, can bring enough quality control to bear to make a /safe/ prismatic cell on this scale:
  20. josephkk

    josephkk Guest

    I do not exactly agree with inherently dangerous. I say inherently
    difficult (to damn difficult) to do safely. See sodium-sulphur batteries.
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