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Design News, March 2013

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News Trends \\\ Breakthroughs \\\ Developments Source: NTSB an NTSB engineer examines the casing from the battery involved in the JaL Boeing 787 flight in Boston. Were the Boeing 787 Batteries Cooled Properly? Experts have been weighing in on the question, and the consensus is a resounding "no." the boeing 787's high-profile battery fire may have been the result of an engineering double-whammy: an energetic battery chemistry combined with a possibly inadequate cooling system. Battery experts who spoke to Design News said that the 787's lithium-ion batteries employed a cobalt oxide cathode, which is known to be more prone to overheating than other lithium battery chemistries. If that chemistry was used without extra measures to draw heat away from the pack, it could be a problem, experts said. "It's a no-brainer," Elton Cairns, a professor of chemical engineering at the University of California and a nationally known battery expert, told us. "If they used a cobalt oxide chemistry, then the battery should use a cooling system." Although Boeing has not said whether the 787's lithium-ion battery packs use any kind of active cooling system, experts who saw photos of the packs said it looked unlikely. "The images I saw indicated that there was no active cooling system and this battery pack has many cells stacked close together," Donald Sadoway, the John F. Elliot Professor of Materials Chemistry at the Massachusetts Institute of Technology, wrote in an email to Design News. "So you need active thermal management." Boeing representatives told Design News that their lithium-ion battery pack used specific measures to prevent overcharging. "There are multiple back-ups to ensure the battery system is safe," a Boeing spokesman told us. "That includes protection against over-charging Design News | march 2013 | www.d esign n ews.com –30–

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