Jet puts spotlight on battery risks
January 19, 2013
Chances are the same kind of battery that twice caught fire in Boeing 787 Dreamliners in recent weeks is in your pocket at this very moment.
Lithium ion batteries, small and powerful, have become the electricity storage device of choice. They are everywhere -- in cellular phones, laptops, power tools, even cars. They allow us to talk, email and drill longer than ever possible in the past.
But the incidents that led to the grounding of the 787 fleet worldwide, and the decision by Boeing on Friday to temporarily halt all deliveries of the plane, have highlighted a troubling downside of these energy-dense dynamos: their tendency to occasionally burst into flames.
With investigators now working to determine the cause of the incidents, one on a Dreamliner on a Boston runway, the other forcing an emergency landing of a 787 in western Japan, the larger question of lithium ion safety has snapped into focus.
"Every battery can burn and every battery can be flammable," said Mike Eskra, a Milwaukee-based battery development scientist who also works as a battery fire investigator for insurers. "But lithium ion batteries are more dangerous because they store more energy. It's like a firecracker instead of a stick of dynamite."
The casualty list is long. In recent years, tens of thousands of laptop batteries have been recalled due to the risk of fire or explosion. The 400-pound lithium ion battery on General Motors' cutting-edge electric car, the Chevrolet Volt, burst into flames seemingly spontaneously while parked in 2011. And investigators blamed a cargo hold full of lithium ion batteries for a fire that caused a UPS-operated 747 to crash shortly after takeoff from Dubai in late 2010.
That crash, which killed both pilots, is one of more than 100 incidents recorded by the Federal Aviation Administration linking lithium ion batteries to onboard fires over the last two decades. This month, new rules took effect limiting the transport of lithium ion batteries in aircraft. And the FAA had long prohibited use of the technology in commercial airplanes.
That changed in 2007, when it granted Boeing permission to use the batteries in the 787 under a number of conditions to ensure safety. For Boeing the lithium ion advantage was clear.
Thanks to their chemistry, the rechargeable batteries can store as much energy as a nickel metal hydride pack that's 50% heavier, while charging and discharging faster than other battery types. That's made them attractive for military applications such as the B-2 bomber and also for use on the International Space Station and the Mars Rover.
Lithium ion batteries enabled Boeing to swap out heavy hydraulic systems in the airframe for lightweight electronics and electric motors to operate systems like wing de-icers. That's a key reason the Dreamliner burns 20% less fuel than other wide-body aircraft.
The weight and power savings are exactly what made lithium ion batteries popular in other applications. In excess of 95% of mobile phone batteries worldwide are lithium ion, and without lithium ion, laptops couldn't run anywhere near as long as they do without a recharge.
"They completely dominate the consumer market," said Vishal Sapru, energy and power systems research manager at consulting firm Frost & Sullivan in Mountain View, Calif.. He estimates that global sales of lithium ion batteries reached $14.7 billion last year, up from $9.6 billion in 2009, a 53% increase. Sapru expects the market to soar to $50.7 billion by 2018. "No other battery chemistries are growing at that rate."
But lithium ion also has downsides. The batteries tend to have shorter life spans than older, more proven battery technologies. And although the price is falling, lithium ion is still more expensive than other batteries. Although some carmakers have embraced the technology, others, such as Toyota, have decided against it. Several makers of lithium ion auto batteries for electric vehicles have filed for bankruptcy last year because of weak demand.
Safety experts also have concerns. Because lithium ion batteries can store more energy, and discharge it more quickly, than other batteries, lithium ion cells can get much hotter than other technologies in the event of an overcharge or the external application of a heat source. Larger applications, such as the 63-pound batteries on the 787, incorporate multiple cells and the heat can spread rapidly from cell to cell, a chain reaction called "thermal runaway."
And while other types of batteries use a water-based electrolyte in each cell, lithium ion relies on a highly flammable solvent. When heated up, that solvent tends to vaporize, spraying the burnable gas into the surrounding air. As a result, lithium ion battery fires burn extremely hot, as high as 2,000 degrees Fahrenheit.
Those conditions were blamed for an explosion at a General Motors battery testing lab last April that caused $5 million in damage and sent one person to the hospital. GM said flammable gas had vented from an experimental lithium ion battery that heated up during extreme testing.
"Lithium ion is very controversial in the safety engineering space," said Brian Barnett, vice president for battery technology at Tiax, a technology firm in Lexington, Mass. He spoke last month at a conference on battery safety in Las Vegas, where more than three-quarters of the presentations focused on lithium ion batteries.
The cause of the fires in the two Dreamliners has still not been determined and neither Boeing nor the Japanese company that made the batteries, GS Yuasa, have publicly commented on likely factors. Boeing subjected the batteries on the plane to thousands of hours of testing and installed numerous safety systems specific to the batteries.
"We have high confidence in the safety of the 787 and stand squarely behind its integrity as the newest addition to our product family," Boeing Chief Executive Jim McNerny said Friday.
Barnett and others emphasize that it's not uncommon to see problems in relatively new technologies. But they add that most lithium ion fires are caused by an external problem, such as a bad circuit or a software glitch that leads to overcharging. Another common problem in consumer electronics is the use of low-cost wiring and other components that can overheat and spark or catch fire next to the battery itself.
Eskra, the battery fire investigator, said he's seen fires started by Chinese-made toys that use lithium ion batteries hooked up to chargers designed for nickel cadmium or nickel metal hydride batteries. Manufacturing errors, including allowing tiny metal particles to contaminate cells, can cause dangerous shorts, although they are exceedingly rare.
"Somebody tried to cut corners somewhere," he said, noting that most lithium ion fires are caused by a tiny part that malfunctioned somewhere along the line and are easily resolved. "It's a $2 fix, but it takes half a million dollars in research to figure out what it is."
Sometimes the problem is more persistent. In 2006, Sony announced a global recall of more than 10 million lithium ion laptop batteries used in a variety of laptop computers after more than a dozen fires, and two years later issued a second recall.
Still, considering the vast proliferation of lithium ion batteries and the relative paucity of serious problems, there seems to be safety in numbers.
"All batteries are energy storage devices and if they're not manufactured or managed correctly, there is a risk," said George Kerchner, executive director of trade group the Rechargeable Battery Assn. "But lithium ion is a ubiquitous technology and it wouldn't be out there if it weren't safe."