The Boeing 787 battery fire in Boston last month was caused by a battery short circuit that led to a thermal runaway condition, the National Transportation Safety Board (NTSB) has concluded.
NTSB investigators who did forensic analysis of the Boeing battery said the charred components indicated the temperature inside the 63-pound pack had exceeded 500 degrees Fahrenheit during the January 7 incident at Logan Airport. Evidence showed that one of the pack's eight cells short circuited, causing the temperature to soar.
"Our review of the flight data recorder data shows that the voltage of the battery dropped from a full charge of approximately 32 volts to approximately 28 volts," said NTSB chairman Deborah Hersman in a press conference on Thursday. "This drop is consistent with the charge voltage of a single cell."
NTSB chairman Deborah Hersman said last week that investigators have concluded that a short circuit occurred in cell number six of the pack's eight cells. (Source: NTSB)
NTSB investigators ruled out mechanical impact damage and external short circuits as the reason for problems inside the battery, Hersman said. They did not know, however, whether the short circuit was caused by battery charging or by defects in the design and construction of the unit, or some other problem.
Experts contacted by Design News said a temperature of 500 degrees can create serious problems for a lithium-ion battery pack. "It's high enough to cause the cells to bloat and possibly to burst into flame," Donald Sadoway, John F. Elliott professor of materials chemistry at MIT, told us in an email. "Remember, the electrolyte is volatile and flammable."
Boeing said it still has not announced any specific ways to fix the 787 batteries, despite reports in various news media that it has already settled on a fix. The Wall Street Journal reported on Friday that the company "is looking at increasing the separation between cells in the lithium-ion batteries to reduce the potential hazards from heat or fire spreading within the batteries and adding enhanced heat sensors."
"There has been no public decision by the company on what these answers might look like or, specifically, what our teams have been working on," Boeing spokesman Marc Birtel told Design News. "We're not going to talk about a fix until we have something to share that's at the point of approval by the FAA."
Improvements like the ones mentioned by The Wall Street Journal have been the subject of much speculation over the past month. Two weeks ago, Tesla Motors CEO Elon Musk publicly stated that the 787 battery pack design was unsafe, and experts such as Sadoway and Elton Cairns of the University of California have suggested that an active cooling system would provide an additional layer of safety for a cost that would be miniscule compared to other 787 sub-system costs.
Sadoway again said last week that the Boeing batteries would be safer with active cooling. "That's what GM does in the Chevy Volt," he told us.
We all know that lithium batteries are not the state of the art.Funny is that I have an old Samsung 225 with ORIGINAL battery for 10 years. Lithium batteries are bit strange.They should not be discharged completely like SOME others can.I found out that NiMH are also praclically trash if you discharge them fully.So, some kind of trickle charge is a good idea.I am onot a chemist, but I suspect that once the chemistry of a battery goes to extreme ,be it under , or over limits , that battery is unuseable.As far as temperature goes lithium batteries have been used on ships for many years with a great success.Cooling(or in case of airplane ,sometimes heating) and stable pressure is a key here.Unfortunately planes have no natural constant cooling and experience huge changes in an air pressure.
The best thing is this - We will create a battery technolgical leap with this issue. If the analysis is correct the solution has already solved itself -fix the initial or isolate the components of the battery so a small section at 500 degress will not ignite more of the battery or surrounding componets and the issue cannot migrate to the rest of the battery. I commend Boeing for using this technology. If every issue they ran into was solved by adding a cooling system (weight) and revering to the tried and true the plane would be a 707 with lipstick on it - just like a typical marketing department requested. Engineering is not for the faint of heart. In ten years we'll look back at the 787 as a relic that pushed us forward. It will create battery powered cars that actually make sense and cents.
When I wore a military uniform (never mind which color) I remember we had some communicaion equipment which had lithium batteries installed. The equipment was labeled "Do not airlift" because no one trusted the batteries to behave themselves in the air. Nevertheless, I don't remember ever seeing one of these boxes damaged by battery failure. Maybe the correct fix is to switch to a safer battery technology (LiFePO, fof example). Less energy density, but the airlines can make up for it by charging obese passengers a surcharge (they are a prime example of low energy density). Sorry for not being politically correct.
It's been previously reported that the battery was not factory-original, that the battery that burned was replaced by the airline as part of maintenance.
The first 787 is barely one year old, and airlines are replacing batteries? Can you draw a parallel between 787 and a smart phone?
Experts Sadoway and Elton Cairns "suggested that an active cooling system would provide an additional layer of safety for a cost that would be miniscule compared to other 787 sub-system costs. Sadoway again said last week that the Boeing batteries would be safer with active cooling. "That's what GM does in the Chevy Volt," he told us."
My first thought was weight. The Chevy Volt is a grounded vehicle that must generate enough electrical power to propel itself over pavement at a reasonable rate of speed...relatively slow compared to the 500+mph (ground speed) of a large commercial airline.
Like most other mechanical contraptions we've invented, turning electricity into power and power into motion is a big issue. The heavier the machine, the more power it takes to make it move. And thus more electricity. More batteries. More weight.
Wouldn't adding an active cooling system add considerable weight? And take up precious space?
Yes, did it short due to poor construction, being deep cycled too often or being baked too long in that sealed box with no active cooling?
It's almost like having a murder case where the victim was poisoned, shot and stabbed by three different people and the coroner's report states that the victim died due to cardiac arrest.
If it's a manufacturing flaw, then Boeing is off the hook and they look good due to the limited damage caused. If it's an external problem, where the batteries are being utilized more than intended, then it indicates insufficient testing and/or new model growing pains and doesn't really indicate a significant problem at Boeing. If it's an overheat problem due to ignorance or post-testing/pre-production design changes, then it tends to reflect poorly on Boeing.
I guess we will only find out if Boeing volunteers the information.
Yes, it does raise more questions. Because they've isolated the short circuit to cell number six, they should now be in a better position to track down the reason for the short. Hopefully, we'll be getting more news soon.
Using almost 200 light-emitting diodes in the front and back of the new 2014 CTS, Cadillac designers are showing how LEDs can change the character of a vehicle.
We looked at a number of sources to determine this year's greenest cars, from KBB to automotive trade magazines to environmental organizations. These 14 cars emerged as being great at either stretching fuel or reducing carbon footprint.
From Dell / Intel® New Paradigms in Design Work Scott Hamilton, vertical market strategist for Dell Precision workstations, 5/2/2013 3
Early in my career, I worked as a draftsman and remember the days of drawing on vellum with numbered pencils and Mylar with plastic lead. This was a fun experience in the sense that I ...
I've been using workstations for more than 10 years and love finding ways to get more performance from my system. With demanding professional applications that require more power each ...
A lasting memory from my first job as an engineer in an auto assembly plant is standing on hard concrete at six in the morning, vending-machine coffee clutched in hand, listening to ...
A quick look into the merger of two powerhouse 3D printing OEMs and the new leader in rapid prototyping solutions, Stratasys. The industrial revolution is now led by 3D printing and engineers are given the opportunity to fully maximize their design capabilities, reduce their time-to-market and functionally test prototypes cheaper, faster and easier. Bruce Bradshaw, Director of Marketing in North America, will explore the large product offering and variety of materials that will help CAD designers articulate their product design with actual, physical prototypes. This broadcast will dive deep into technical information including application specific stories from real world customers and their experiences with 3D printing. 3D Printing is
To save this item to your list of favorite Design News content so you can find it later in your Profile page, click the "Save It" button next to the item.
If you found this interesting or useful, please use the links to the services below to share it with other readers. You will need a free account with each service to share an item via that service.
Tweet This
1 
