No need to get hot, bothered over battery



If business travelers didn't have enough to worry about, this week's headlines provided yet another unhappy prospect: exploding laptop computers.

No terrorists to blame for this one. The problem involves the chemical cocktail that the makers of lithium-ion batteries use to power laptop PCs, cell phones, digital cameras, music players and other gadgets.

After reports of a half-dozen batteries catching fire (including a well-photographed incident that became a candid-camera classic on the Web), Dell Inc. this week recalled 4.1 million laptop batteries shipped between April 1, 2004, and July 18, 2006.

It was the largest battery recall in history - front-page news in many newspapers, including this one. Does that mean you should be worried?

If you have one of the affected machines, Dell wants you to turn it off, remove the battery and return it for replacement. Until the new one arrives, you can use the computer on AC power. That's good advice.

But let's put it into perspective. It's highly unlikely that your laptop, or any other, is about to burst into flames. The Dell problem involved a mere handful of machines using a specific set of batteries manufactured by Sony. During the period they were shipped, Dell alone sold about 22 million laptop computers.

"I wouldn't be worried at all, with the millions of batteries out there and the way they're being used," said Isidor Buchmann, founder and chief executive of Cadex Electronics Inc., a Vancouver, British Columbia, firm that makes battery testing and charging equipment.

Buchmann is the author of Batteries in a Portable World, a primer on rechargeables for non-engineers. He also maintains, a Web-based compendium of lucid, non-technical articles that describe what goes into and comes out of the batteries we use in today's gadgets.

What goes into them is some pretty exotic stuff.

Most of our portable electronic gear - including laptop computers and hundreds of millions of cell phones - uses lithium-ion batteries. The basic technology behind these cells was developed before World War I, but it wasn't until 1991 that Sony successfully commercialized the process, making it the dominant battery technology in the consumer market.

Although Buchmann says they're not as rugged and might wear out sooner than older nickel-cadmium and nickel metal-hydride batteries, lithium-ion cells provide a much higher "energy density." In other words, more power in less space with less weight.

PC makers desperately need that combination. They're producing laptops with computing power that rivals desktop PCs. Consumers, meanwhile, are demanding enough battery life for coast-to-coast (and even trans-Atlantic) flights.

So, battery manufacturers have been pushing the envelope.

One thing they have going for them is the reactivity of lithium itself. It's the lightest metal in the periodic table, and theoretically an excellent material for batteries.

Unfortunately, pure lithium is too reactive for batteries that have to be recharged - so you'll find it mostly in throw-away cells. For rechargeables, engineers have developed more stable lithium-ion compounds.

Now recall that a battery's real job is to store energy. When everything works well, it releases that energy as a steady, controlled flow of electrons to your laptop, cell phone or MP3 player.

Generating heat

However, if there's a short circuit or some other problem, the same energy can be converted directly into heat. When it gets hot enough, a battery can fail, melt down, leak noxious chemicals or, in the worst case, burst into flames.

Lithium-ion batteries might be more prone to the extreme heat than earlier types because their components are more flammable.

According to Buchmann, batteries built for military equipment are frequently more powerful than their civilian counterparts - but also more prone to failure and fire. The energy density of batteries designed for consumers is a bit lower, and the chemistry is, in Buchmann's words, "more stable."

He said manufacturers design a variety of safeguards to prevent bad things from happening, including voltage regulators to protect the electronic equipment, and pressure gauges to prevent explosions.

But no system is perfect. In the Dell case, a Sony spokesman said the defect involved microscopic metal shards - particles left over from the manufacturing process that can penetrate a lithium ion cell wall and contact a battery anode, creating a short circuit.

Normally, that kind of failure will just make the battery stop working. In extreme instances, it can result in a fire.

None of this is particularly new. Even if they're not smoking, laptops have been running hotter and hotter over the past few years.

Too hot for comfort

I've tested a handful of machines that are far too hot to use on anyone's lap - unless you're willing to invest in a protective lap "desk." Some are too hot on top for comfortable typing.

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