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Final report on 787 dreamliner battery fire

Discussion in 'Cars and Transportation' started by kennybobby, Dec 2, 2014.

  1. kennybobby

    kennybobby Member

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    The NTSB has released its report from this investigation:

    The NTSB determines that the probable cause of this incident was an internal short circuit within a cell of the APU lithium-ion battery, which led to thermal runaway that cascaded to adjacent cells, resulting in the release of smoke and fire. The incident resulted from Boeing’s failure to incorporate design requirements to mitigate the most severe effects of an internal short circuit within an APU battery cell and the FAA’s failure to identify this design deficiency during the type design certification process.

    As a result of this investigation, the NTSB makes safety recommendations to the FAA, Boeing, and GS Yuasa. The NTSB previously issued safety recommendations to the FAA regarding (1) insufficient testing methods and guidance for addressing the safety risks of internal short circuits and thermal runaway and (2) the need for outside technical knowledge and expertise to help the FAA ensure the safe introduction of new technology into aircraft designs.
     

    Attached Files:

  2. ggr

    ggr Roadster R80 537, SigS P85 29

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    So the bottom line is that the battery self-destructed under normal operating conditions. GS Yuasa seem to be the source of the problems. Guess who makes the 12v battery that's been the source of so much trouble in the Model S, although that is not a Li-ion battery so there's no corresponding worry for the Model S, at least I hope not.
     
  3. stopcrazypp

    stopcrazypp Well-Known Member

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    I remember GS Yuasa also had a bad batch of batteries that affected the iMIEV and Outlander PHEVs (as in they actually caught fire under normal operation), so they definitely have some QC problems.

    However, Boeing also has to take some blame, because as Elon said, they didn't leave sufficient enough room between cells such that a failure of one wouldn't propagate to the others. This is doubly important since they were using lithium cobalt cells (same type as in Roadster), the most volatile type of lithium ion battery.
     
  4. JRP3

    JRP3 Hyperactive Member

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    I believe the faulty iMiev/Outlander cells had been damaged at the factory and not taken out of service. I don't think cell packaging was the issue that Elon claims since in thermal runaway events Tesla packs have also seen propagation to other cells, and the entire pack. In any reasonably compact battery pack I don't think it's possible to leave enough room between cells to avoid this.
     
  5. techmaven

    techmaven Active Member

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    Apparently they also had the wrong high temperature setting... above the initial start of thermal runaway. Further, they didn't have sufficient cell temperature monitoring for the BMS. The manufacturing and conductor assemblies were also shoddy. And they really couldn't handle a single cell thermal runaway.

    All in all, a real mess.
     
  6. JRP3

    JRP3 Hyperactive Member

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    I wonder what the current demand was when starting the APU. It was a 75ah battery so a cranking load of 500 amps or more would be over 6C.
     
  7. stopcrazypp

    stopcrazypp Well-Known Member

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    I don't believe we have seen any single/small unit cell thermal runaway events thus far for Tesla (link please to an example if that is not the case). Although we have seen plenty of multi-cell punctures from external damage.

    I believe Tesla's pack can tolerate having a handful of cells have thermal runway without cascading, but obviously even the best designed system can't work if there's external damage and a huge chunk of cells are punctured. In such a case of external damage, cells may be physically crushed together, any thermal insulation may have been damaged, fire can be caused by external short circuits, etc. Although I should note even in those cases, the per module separation stopped the fires from spreading to all modules of the battery.

    Here's Elon talking about cascading thermal runaway.
    http://blogs.wsj.com/corporate-intelligence/2013/02/26/elon-musks-solution-to-boeings-battery-problem/

    From the NTSB report, it seems neither Boeing nor FAA's engineer even considered the possibility of a cascading failure happening.
     
  8. Cosmacelf

    Cosmacelf Active Member

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    Bottom line - Boeing, that makes planes where a battery fire can easily kill an entire planefull of people, didn't have anywhere near the battery safety of Tesla. Good to know...
     
  9. JRP3

    JRP3 Hyperactive Member

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    All valid points.
     

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