I highly recommend “Lithium-Ion Batteries Hazard and Use Assessment”+:
http://www.nfpa.org/assets/files/pdf...rieshazard.pdf
for those of you who really want to understand the chemical, electrical, and mechanical aspects of these batteries. This report was mentioned in one of the first dozen or so posts about this problem but, based on the many questions and comments here, I suspect many participants have lost track of the report.
It was published in July 2011 at the request of “The Fire Protection Research Foundation” and was produced by two professional engineers and two PhD engineers. The research group reports they have been studying Li-ion battery failures and conducting destructive testing for over a decade.
The report was not focused only on aviation use of the battery but rather the general fire hazard, fire containment, and fire fighting issues associated with Li-ion batteries. The report does contain a great deal of FAA and UN regulatory data and information. The report is clear, concise, easy to read, and contains a lot of good photographs and detailed test data.
The report tested many Li-ion batteries to total destruction and carefully documents the many aspects of Li-ion battery fire initiation and spread.
Key characteristics of the batteries that I noted in the report that might be important are shown below:
1) The susceptibility to minor point impact on the battery case and the resultant internal damage that leads to individual and then battery wide conflagration. (page 71)
2) Mechanical damage to a cell case “perpendicular to the electrode edge is likely to result in high impedance shorting between electrode layers and initiate thermal runaway.” (page 57)
3) “Mild” mechanical damage can lead to thermal runaway over multiple cell discharge/charge cycles; caused by lithium plating (dendrites?) or mechanical creation of a small internal hole in the electrode. Failure is most likely to occur during charging or just after charging. (page 72)
4) “The vast majority of thermal runaway reactions that occur in the field occur during or shortly after cell charging.” (Page 84)
5) Cells that are below 50% of their full charge will seldom experience thermal runaway (page 84)
6) A single cell that is in thermal runaway mode will vent gas at over 650°C which is far above the Auto-ignition flash temperature of the electrolyte. (page 85)
7) FAA burn tests in an contained space show temperatures of 1000° F to 1400° F at 12” above the burning cells. (page 107)
8) No significant amount of oxygen is found in the gases vented by an overheated cell (page 63) and there must be a sufficient oxygen present from an external (not vented gas) source to sustain combustion (page 66)
9) Multi-cell batteries can be designed to minimize cell-to-cell heat transfer during a single cell thermal runaway by adjusting cell spacing and the orientation of the cell ejection path. (page 67)
10) “Thermal runaway can occur significantly after flame suppression” – a coolant must be applied to prevent subsequent ignition. (page 110)
11) Extensive tests by the US Navy show plain water to be an effective flame suppressant and coolant. (page 112)
12) There are several significant unknowns (“Gap Analysis”) regarding Li-ion fire hazards: Limited understanding of vented gas composition and flammability and Limited data on the effectiveness of suppressants. (page 116)