Whether or not the battery exceeded its design voltage, however, experts believe a cooling system was critical. Lithium-ion battery chemistries in general are "energetic," they said, and the cobalt oxide varieties of lithium-ion are particularly so.
"Not all lithium-ion batteries are created equal," Cosmin Laslau, a research analyst for Lux Research, told us. "None of them should fail. They are all essentially safe. But in the event of a failure, lithium cobalt oxide would fail earlier than the other types. Chemical bonds in lithium cobalt oxide will release oxygen earlier." Experts say the release of that oxygen can, in rare cases, lead to fire.
Many engineering teams around the world choose cobalt oxide chemistries, however, because it offers energy densities that can be up to 25 percent higher than other types of lithium-ion, such as manganese spinel (used in the Chevy Volt) and phosphate-based systems.
To counteract the higher energies, big, lithium-ion batteries in general are often used in conjunction with cooling systems, no matter whether they are cobalt-, manganese-, or phosphate-based. The Chevy Volt, for example, employs liquid coolant that circulates through 1-mm thick channels machined into 144 metal plates sitting between its lithium-ion manganese spinel cells. Similarly, the Prius PHV plug-in hybrid uses specialized fans, intake ducts, and 42 temperature sensors to actively monitor and cool its lithium-ion battery.
To be sure, the 787's 63-lb battery pack is smaller than those of today's typical electric cars, which can often exceed 400 lb. But experts said that lithium-ion batteries of all types need ways for heat to get out. "Size does make a difference," Cairns told us. "But the size of that (Boeing) battery is still substantial. If the cell casings are touching one another or have inadequate space to allow for natural convection cooling by air, then you're in for trouble."
Cairns said that he hadn’t personally seen the Boeing battery pack, however, and didn't know if Boeing engineers had provided any means for the heat to escape.
Battery experts who spoke to Design News repeatedly stressed the fact that all types of lithium-ion batteries can be safe and successful, if engineered properly. The question still being answered is whether Boeing engineers did that. “They should have stress-tested the battery with charging system as it it is installed in the 787,” Sadoway said. “I myself wouldn't fly in a 787 at this point."
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.
By experimenting with the photovoltaic reaction in solar cells, researchers at MIT have made a breakthrough in energy efficiency that significantly pushes the boundaries of current commercial cells on the market.
In a world that's going green, industrial operations have a problem: Their processes involve materials that are potentially toxic, flammable, corrosive, or reactive. If improperly managed, this can precipitate dangerous health and environmental consequences.
With LEDs dropping in price virtually every year, automakers have begun employing them, not only on luxury vehicles, but on entry-level models, as well.
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