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23Jan 2013

Sorting out the Dreamliner's lithium-ion nightmare.

Lithium-ion battery.

If Boeing is having trouble with the batteries in its 787 Dreamliners, it is not alone. "As 21st century technology strains to become ever faster, cleaner and cheaper, an invention from more than 200 years ago keeps holding it back," writes the AP's Seth Borenstein. That invention would be the battery. "It's why electric cars aren't clogging the roads and why Boeing's new ultra-efficient 787 Dreamliners aren't flying high," he continues.

He reminds us that in 2006 and 2007, "more than 46 million cell-phone batteries and 10 million laptop batteries--all lithium-ion--were recalled because of the risk of overheating, short-circuiting, and exploding." It almost makes you want to scrap your lithium-powered laptop for one of the old steam-powered models of yesteryear.

Borenstein explains why we tolerate lithium-ion batteries, and why Boeing demands them: they "store more energy at a higher voltage and a lighter weight than earlier types." But these things have been around (and exploding?) for 25 years. What is the next big battery thing? "None of the 10 experts who talked to the Associated Press said they know what that big thing will be yet, or when it will come," Borenstein writes.

Gautam Naik of The Wall Street Journal explains, in a story headlined "The Science Behind Dreamliner's Batteries," that the chemistry that makes lithium-ion batteries so light and powerful is precisely what "may increase their risk of overheating and catching fire." The batteries on the Dreamliner are continually charged by the plane's generators, but when the batteries become overcharged, the electrolyte--the chemical mix that resides between the batteries' two electrodes--can break down and generate heat, Naik reports. So far, there is no evidence that the plane's batteries were overcharged.

Chemists call it "thermal runaway," a process that can generate more and more heat until the battery ignites. Naik tells us temperatures can reach between 570 and 750 degrees Fahrenheit. Not a comforting thought when you're cruising at 36,000 feet. Engineers don't yet know whether that's what happened to the Dreamliner's batteries, Naik reports.

Craig Timberg at The Washington Post says even model-plane enthusiasts know the risks of lithium-ion batteries. He describes a scale model crashing to earth in a puff of smoke seconds after takeoff with an incinerated battery. "I've had buddies blow the ends of their fingers off with them," one hobbyist tells Timberg.

But Kevin Bullis at Technology Review is reassuring. Lithium-ion battery fires "are extremely rare," he writes, "and usually result from damage to the battery--such as piercing or overcharging--or problems with the manufacturing process." 

Extremely rare? I guess I'll keep my laptop.

-Paul Raeburn

 

Comments

On the 787, the batteries aren't used during normal cruising flight, but they are continually charged by the plane's onboard generators.

A potential problem can arise when a lithium-ion battery is plugged into an external power source for recharging.

Read more: http://online.wsj.com/news/articles/SB1000142412788732462440457825803166...

We (at least the public) really does not know what actually happened to cause the batteries to catch on fire, and the NTSB may not know what happened either as yet.

If this is a case of a poorly designed battery, or charging or cooling systems, then that can probably be corrected. This is relatively new technology and problems can be expected, although proper testing was obviously not done before the planes were delivered to the airlines.

On the other hand, if this is a fundamental engineering problem(s), then perhaps things won't be so easily corrected. A good example of this is the assertion that the batteries are located to close to other vital systems. If this is true, it will be much more difficult to fix.

Still, like them or not, Boeing has a history of building good, reliable airplanes, so I suggest we all calm down and wait until the engineers find out what happened and why, and hopefully find a way to correct the problems. Making assumptions about causes at this point is a waste of time.

Read more here: http://www.popsci.com/technology/article/2013-01/why-boeings-787-dreamli...

One point that reports of the lithium-ion battery problem may have missed is that electric cars, such as the Chevy Volt do not use the same type of lithium-ion battery that is susceptible to fires. So it would be a good thing to inform the public that electric cars should not be subject to the same sort of risks as the 787 (and laptop computers).

Boeing 787 Batteries Same As Those In Electric Cars? Umm, NO

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