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 this week 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."
An NTSB engineer examines the casing from the battery involved in the JAL Boeing 787 flight in Boston. (Source: NTSB)
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 and over-discharging."
Boeing representatives did not know whether the battery packs included cooling, however. And cooling was not mentioned in a five-page transcription of a Boeing media call explaining the incidents.
The 787's use of lithium-ion batteries for the auxiliary power unit is said to be a first, which is one of the reasons why the batteries are being scrutinized so heavily. The National Transportation Safety Board (NTSB) X-rayed batteries from a January 7 fire aboard a Japan Airlines Boeing 787 at Logan International Airport in Boston. The NTSB team also did CT scans, disassembled the battery, and examined flight data recorders to determine if it exceeded its design voltage of 32V.
On January 20, investigators said that the battery did not exceed its prescribed voltage. Since then, the agency has continued to look for the root cause of the problems, which have occurred on two Japan Airlines flights and one United flight.
I don't know if there was any official mention of it, lcs1956. However, in one of our subsequent articles, Elton Cairns of Lawrence-Berkeley labs said this: "When the plane is at altitude, the air is less dense," he told us. "So even if it's cooler, the less dense air may not have adequate heating capacity to provide enough cooling for the battery. If they don't have active cooling, then I question the adequacy of the cooling arrangement."
Has anyone considered the lack of adequate convective cooling at cruising altitude? I used to work at Los Alamos in the 80s and several devices designed at sea level would fail due to overheating at the 7700 feet altitude arising from the lower air density, especially CRT computer terminals.
Technology has become too complex and there are a lot of pitfalls in almost everything but especially so when new technology is introduced. Analysis and deliberation takes so much time that management becomes impatient. Most companies have replaced team managers with semi-technical or pseudo technical schedule pushers with the philosophy that ignorance is bliss when schedules have to be met. After all the world is very competetive and risk taking has become the name of the game. But not having a back up plan such as an alternative battery pack design which may be more reliable though somewhat less efficient is a serious incompetency issue. Boeing would be lucky if the cause can be determined with certainty and even if it is determined, the increased scrutinity will not allow immediate release of the fix. The finacial damage cused by the delay is far out of proportion to the benefit of the new battery.
Virtually everyone agrees with you at this point, Jenn -- NTSB, most newspapers and experts. Even USA Today even did an editorial calling for the 787 to be grounded until the problems are fully understood.
I think you're right on the money when you say that good engineers solve these problems, given enough time, Gorksi PE. Occasionally, there are mistakes, but engineers know how to handle high-energy situations. Gasoline holds far more energy than lithium-ion batteries, and it seems like engineers have mastered the safety of the internal combustion engine.
It seems to me that the battery problem on the 787 is the result of engineering being pushed too far too fast. Now that the problem is out in the open many "experts" are saying it's the cooling system. It sounds like this common knowledge about the characteristics of the 787 batteries. If so, why did the engineers go ahead and not put a cooling system in? No time? There was a schedule to meet? It's a monir problem? Good engineers solve these problems,given enough time.
It seems to me that the battery problem on the 787 is the result of engineering being pushed too far too fast. Now that the problem is out in the open many "experts" are saying it's the cooling system. It sounds like this common knowledge about the characteristics of the 787 batteries. If so, why did the engineers go ahead and not put a cooling system in? No time? There was a schedule to meet? It's a monir problem? Good engineers solve these problems,given enough time.
The answer's complex. Boeing wasn't exactly forthcoming about details and there were many, many news items, much of it speculation. This article, and its comments board, might give you some idea. http://www.designnews.com/author.asp?section_id=1392&doc_id=238056
I agree, don't jump to conclusions. It would be difficult to find a generic design flaw that was so carefully balanced that only two batteries have destructed out of the one hundred batteries in the fifty delivered airplanes. I would expect dozens of battery fires if the heat dissipation was ignored as in "you have to use active cooling". To me it seems that the apparent rarity of problems seems to fit some less obvious design flaw or a quality assurance problem.
Just a word about the composite construction. Take a look at the carbon composite B-2, in service since 1997. I don't think carbon composites are a new thing to Boeing.
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