WASHINGTON Batteries like the one that burned on a Boeing Co 787 Dreamliner in January can be made safer, but doing so can cut performance and raise costs, experts told U.S. safety investigators on Thursday.
The use of lithium-ion batteries has greatly expanded in the past decade, powering everything from Tesla cars to iPads, and the risk of fire is well-understood, experts said at a forum organized by the U.S. National Transportation Safety Board.
But even as participants praised the batteries as the most powerful and lightest available, they also said there was still no fool-proof way to predict or prevent internal short circuits implicated in the Dreamliner fire.
The fire in the battery compartment of a 787 parked on the ground in Boston in January, followed that same month by an in-flight battery malfunction over Japan, led to the grounding of the Dreamliner.
While the final cause of those incidents is still under investigation, Boeing has been allowed by the U.S. Federal Aviation Administration to conduct tests of a redesigned battery unit, part of the plane's auxiliary power system.
The two-day NTSB meeting that began on Thursday is aimed at helping the safety agency gauge the risk of lithium-ion batteries as their use in planes and vehicles expands.
NTSB Chairman Deborah Hersman said after Thursday's session that the risks had to be addressed. "I think with lithium-ion batteries, the genie is out of the bottle," Hersman said.
The number of lithium-ion cells made worldwide ballooned to 4.4 billion in 2012, from 800 million in 2002, according to the Portable Rechargeable Battery Association, a trade group of battery makers.
Boeing's high-tech Dreamliner, that also makes extensive use of carbon fibre to cut weight, is the first commercial airplane to make extensive use of lithium-ion batteries.
"The growth in the mission of lithium-ion batteries is substantial," said Glen Bowling, vice president of sales at Saft Specialty Battery Group, a producer of lithium ion batteries.
"It's a stretching of the technology boundaries and we have to be professional when we do that."
The understanding of what causes short circuits in lithium-ion batteries and how to prevent them remains murky.
Laurie Florence, principal engineer for the independent safety testing organization UL, said some cells in a battery can withstand a short circuit caused by a nail puncture, but not an internal flaw, perhaps caused by an impurity or other manufacturing issue.
While consumer uses have soared, the high costs of lithium-ion of making battery technology safe have led to a slower-than-expected development of electric cars and other bigger applications.
Market predictions for those batteries made as recently as 2008 "were off by more than a factor of 10" when compared with actual market size in 2011, said Yet-Ming Chiang, a professor of materials science and engineering at the Massachusetts Institute of Technology.
"This created a great deal of stress among those who manufacture batteries," he told the NTSB forum. Some went out of business, mainly because the market for lithium-ion did not materialize.
Currently, there is enough idle lithium-ion battery capacity to power 400,000 Nissan Leaf electric cars, he said.
On Wednesday, President Barack Obama proposed a federal budget that would increase the tax credit for buying an electric vehicle to $10,000 from $7,500 to help support sales.
SAFETY VS COST
About 25 percent of a typical lithium-ion battery cell is flammable liquid, which increases the risk of fire, Chiang said. But making a cell safer through additives reduces performance, experts said.
The difficulties of lithium-ion batteries have prompted some experts to rework older technologies or leap ahead to more advanced batteries in hopes of finding a safer, less costly solution for modern uses.
Boeing rival Airbus has dropped lithium-ion batteries from its forthcoming A350 jet, saying it wants let the technology mature and avoid any risk of delaying the jet's development.
Better technology is needed to predict if a battery cell will experience an internal short due to a manufacturing defect, Daniel Doughty, president of Battery Safety Consulting, told the NTSB forum. He added new methods were also needed to prevent a cell fire from spreading to other cells in the battery pack.
The widespread use of lithium-ion batteries has also placed pressure on regulators to develop new ways to safely ship them.
"We all know lithium batteries are hazardous materials," said Janet McLaughlin, deputy director of the Federal Aviation Administration's hazardous materials safety programs.
In the past, the FAA has estimated the amount of hazardous materials on a given cargo plane to be about 5 percent. But now, that figure can be around 80 percent, with much of that related to batteries, McLaughlin said.
(Reporting by Deepa Seetharaman; Editing by Alwyn Scott, Jeffrey Benkoe and Tim Dobbyn)