Posted 25 August 2006 - 08:25 AM
BATTERY FIRES AND VLNC
The recall of nearly six million Dell (Dell) and Apple (AAPL) laptop batteries brought to light what has long been the tech industry's dirty little secret: The batteries that power our laptops, wireless phones, iPods, and cameras are potential incendiaries. The risk of your laptop bursting into flames is low, and it is much lower for other devices. But it is real, and it's not going away.
The lithium-ion batteries that came into widespread use in the late 1990s enabled a revolution in portable electronics by allowing a lot of power to be packed into a very small space. But if you overcharge them, or there is an electrical fault such as a short circuit, the chemicals sealed inside the battery cells can become an explosive fire waiting to ignite.
SCIENCE LESSON. You may recall from chemistry class that lithium is a metal that burns spontaneously when exposed to air and explodes in the presence of water. Surprisingly, though, the lithium has little to do with the risks posed by batteries, since lithium is not normally present in its volatile metallic form. The danger is that the chemical reaction that generates electricity frees up oxygen. If the cell overheats, the oxygen combines with organic solvents in a nasty chemical fire that can be contained but not extinguished until the oxygen and fuel are spent.
Lithium-ion batteries and their cousins, the lithium polymer batteries used mainly in phones and other handhelds (as well as the new MacBook and MacBook Pro laptops, which are not involved in the recall), rely on protective electronics to prevent chemical mayhem. In a handful of the millions of batteries Sony (SNE) made for Dell (DELL) and Apple, these circuits appear to have failed, leading to fires. Physical damage to the battery can cause the same results. There have been a handful of reports of battery fires in phones and other handhelds, but these are much rarer. Laptops are far more flame-prone because their batteries are much larger and operate in a much hotter environment.
Despite the inherent risks, lithium-ion batteries aren't going away anytime soon, because there are no good alternatives. But the dangers are having consequences beyond the financial damage to the companies involved in recalls. One is that we have hit the wall in increasing the efficiency of batteries—at least as measured in watts per kilogram or watts per liter—because without some major chemical breakthrough, higher power densities would cause unacceptable hazards.
SIZE MATTERS. Making batteries larger is also not an option. International Air Transport Assn. regulations prohibit batteries containing more than eight grams of lithium aboard passenger aircraft. The largest laptop batteries used today have hit that limit. (A little-known IATA rule also limits passengers to one primary and two spare laptop batteries of any size, but I have never heard of this being enforced.)
An Austin company called Valence Technology (VLNC) does make a lithium battery with different chemistry that is safer because its reactions don't produce fire-sustaining oxygen. The downside is that these batteries provide significantly less power for a given size and weight. They are being used as battery backups for cell towers and could well appear in the next generation of hybrid cars, which are currently powered by safe but less efficient nickel-metal hydride batteries.
With no breakthroughs in battery technology on the horizon, researchers, led by companies such as Toshiba and Matsush*ta, are pursuing fuel cells as an alternative. Because of the difficulty of transporting and storing hydrogen, the cells would be powered by liquid methanol, not the gas planned for automotive fuel cells. So far, nobody has been able to develop cells that can meet the power requirements of laptops, fit in the space now occupied by a battery, and be cheap enough to be competitive.
SAFETY TIPS. Even if such cells existed, we would need a distribution system to make cartridges of the liquid fuel available everywhere. And while the International Civil Aviation Organization has approved their use aboard commercial aircraft, the methanol cartridges might have a tough time passing muster with the Transportation Security Administration, which prohibited flammable liquids on planes even before the recent crackdown on all liquids and gels.
So we are stuck with lithium-ion batteries for the foreseeable future, but there are a few things you can do to make them safer. One is to treat the batteries gently and protect them from overheating. Fires are much more likely while the battery is charging, so if you run a laptop on in-seat power on an airplane, do everyone a favor, and remove the battery during the flight.
Fires have been rare enough that batteries, other than the defective ones being recalled, do not pose an unreasonable risk. But they are dangerous enough that the industry should step up its efforts to find a safer alternative.