Aviation experts said the energetic quality of lithium-ion can be a concern onboard aircraft. "One of the issues with lithium batteries is they get very hot," Freiwald said. "When they ignite, they can burn so hot that Halon 1301 won't extinguish a fire."
Automakers, many of whom use lithium-ion chemistries in hybrids and electric cars, typically operate their batteries with cooling systems. The Chevy Volt, for example, employs a fluid coolant that circulates through 1mm thick channels machined into 144 metal plates sitting between the battery's cells. Other automakers have employed air cooling on hybrids.
Even with cooling, however, lithium-ion automotive batteries have been known to have problems on rare occasions. In 2011, a fire started in a Chevy Volt weeks after government crash testing, causing a ripple of concern. "The chemistry is edgy," Donald Sadoway of MIT wrote in an email to Design News after the incident. "The electrolyte is an organic fluid that is flammable, highly volatile at even moderately elevated temperature and in the presence of metallic lithium, which can form on the negative electrode at high charging rates."
Although it's not known whether the Dreamliner employs battery cooling systems, its batteries are smaller than those of plug-in hybrid cars. A National Transportation Board (NTSB) examination of an auxiliary power battery unit from the JAL Boeing 787 that caught fire in Boston's Logan Airport on January 7 showed that it measures 19 inches x 13 inches x 10 inches and weighs just 63 pounds. In contrast, electric vehicle batteries can weigh more than 400 pounds.
Freiwald said he doubts the two reported fuel leaks are related to the overheating incidents. Those were more likely to have been caused by human error, he said.
Experts who spoke with Design News emphasized that the cause of the problems isn't fully understood yet, and that such incidents need to be put into perspective. "None of these were catastrophic failures," Dietz told us. "The engineering systems provided an alert to the failures and action was taken. There should be some solace in that."
They obviously overlooked the battery design slightly in the initial stages of development. At least no one was hurt, but I am sure Boeing will fire a few on the battery team. With all the battery exploding incidents from the past, I am surprised that wasn't a concern for the engineering team. However, it could have been a manufacturing error.. Time will tell.
Chuck, Very interesting report. It's amazing how with a system as complex as the Dreamliner, there are a very large number of unknown variables to resolve. Tough for the Boeing engineers who are moving a project of this scope into the marketplace, especially in a spotlight as bright as this situation.
I agree, Al. The spotlight is very bright in this case. I initially wondered if the bright spotlight might be part of the problem here. But the succession of battery overheating incidents in January alone is hard to ignore.
It's interesting that this is the same technology that Ford just standardized on. While the article mentions the cooling systems used in autos and some of the other design components, I can't help but wonder what can happen a few years down the road in vehicles that are not properly maintained...whatever the definition of "properly" may be with respect to battery safety.
Lithium-Ion chemistry is also used in the Chevy Volt, the Fisker and other electric vehicles (but notably not in the Toyota Prius). Li-ion is a very energetic chemistry, which is necessary to pack so much energy in a limited volume. Gasoline is even more efficient, so much so that it can explode in situations where Li-ion batteries would only burn.
The description of the meltdown seems that they might be using lithium cobalt, not a good design choice if that is the case. Lithium iron phosphate LiFeP04 would be the only safe choice. Anyone know what Boeing used?
Very good point, davemiga. I've heard -- unofficially -- that it was cobalt, but haven't been able to verify it. And, yes, a cobalt chemistry is slightly more susceptible to overheating, although all lithium-ion chemistries are on the edge (with the possible exception of the so-called "nanophophate" chemistries).
Liaison engineers have commented previously that Boeing may have done too much too soon with this aircraft.
We have had lithium systems problems in E scooters where thermal overload shut down the 48V system via the batteries management software. We concluded that heavy current draw during acceleration was causing the problem and tried conditioning that by tweaking the controller
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