“The ignition of primary lithium batteries releases a pressure pulse that can raise the air pressure within the cargo compartment. The ignition of only a few batteries was sufficient to increase the air pressure by more than 1 psi in an airtight 10-meter-cubed pressure vessel. Cargo compartments are only designed to withstand approximately a 1-psi pressure differential. The ignition of a bulk-packed lithium battery shipment may compromise the integrity of the compartment by activating the pressure relief panels. This has the same effect as perforations in the cargo liner, allowing the Halon 1301 fire suppressant to leak out, reducing its effectiveness.”
Extrapolating from CR2s to laptop batteries suggests that a laptop fire is not a trivial event.
Li-Ion ICs: Don’t Leave Home Without ‘Em For those who don’t follow the world of ICs for battery-specific applications, here’s an overview. These chips fall into three general categories: charging controllers, “gas gauges,” and security. In practice, all three work together. For instance, the charger IC may tailor the current it delivers based on many functions, including the battery’s current state of charge, which it gets from the gas gauge. In addition, the gas gauge may store a record of events, such as overvoltage lockouts, which the battery manufacturer may use to deny warranty coverage. (A history of lockouts may indicate attempts to perform fast recharges outside the laptop, which may be prohibited by the warranty.) Security chips are necessary to assure that the battery being charged isn’t a bootlegged item that has the wrong kind of charging controller chip or no chip at all. Authentication is a non-trivial process. The chip in the consumer product and the chip on the battery use the SHA-1 one-way hash function defined by Federal Information Processing Standards (FIPS) Publication 180-2, but including specific data based on the use of the chip in the battery. The consumer product and the battery use a public message/secret key protocol to produce a secure fingerprint that authenticates the device in the battery.
Sixteen years have elapsed since Sony introduced the first lithium batteries. Roughly a gazillion devices that use them have been produced and there have been no major catastrophes. It’s no time to panic. But I still wish there were some way to put the fire out.
[1] “Dell to recall 4 million batteries,” Tom Krazit and Michael Kanellos http://news.com.com/Dell+to+recall+4+million+batteries/2100-1044_3-6105486.html# (That story also says, “Several companies, including Valence Technology and PowerGenix, are working on safer lithium ion batteries or batteries which rely on different chemicals.”)
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