Questions about the cooling of the Boeing 787's batteries came up again this week, as Tesla Motors CEO Elon Musk publicly stated that the plane's large pack design is a risky one.
"Unfortunately, the pack architecture supplied to Boeing is inherently unsafe," he wrote in an email to Flightglobal.com. "Large cells without enough space between them to isolate against the cell-to-cell thermal domino effect means it is simply a matter of time before there are more incidents of this nature."
Tesla uses lithium-ion battery packs in its Tesla Roadster and Tesla Model S vehicles. Its design involves 6,000-7,000 small lithium-ion cells. Musk told Flightglobal that the cells are separated in a way that makes them less likely than large cells to suffer from thermal runaway events.
Elon Musk of Tesla and SpaceX: "Unfortunately, the pack architecture supplied to Boeing is inherently unsafe." (Source: revengeoftheelectriccar.com)
Musk has tweeted his desire to help Boeing with its battery problems, which included incidents in two Japan Airlines flights and a United flight this month. On Jan. 18, he wrote, "Maybe already under control, but Tesla and SpaceX are happy to help with the 787 lithium ion batteries." A few days ago, he followed up: "Desire to help Boeing is real & am corresponding w 787 chief engineer." Shanna Hendriks, a spokeswoman for Tesla Motors, confirmed to us that Musk made the comments on his Twitter account and by email to Flightglobal.
Marc Birtel, a Boeing spokesman, would not verify whether his company's chief engineer has been in contact with Musk. "We're engaged with a number of experts both inside and outside the company," he told us, but Boeing is "not identifying them by name publicly."
The issue of battery cooling has been at the forefront of the Boeing story for a week. Donald Sadoway, the John F. Elliott professor of materials chemistry at MIT who is involved in a battery startup with Bill Gates, told us last week that a forced air cooling system and sensors may be needed to monitor and cool the battery in the event of overheating. Elton Cairns, a professor of chemical and biomolecular engineering at the University of California, Berkeley, and a fuel cell designer for NASA's Gemini spaceflights, also suggested that an air- or liquid-cooled system would be necessary.
Even at low temperatures, the Boeing system could still have been at risk, according to Cairns. "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."
Boeing uses eight lithium cobalt oxide cells in its battery packs. According to experts, the cobalt oxide chemistry is known to have higher energy densities than other forms of lithium-ion, so it needs an active cooling system.
Boeing representatives told us that they are not aware of an active cooling system for the 787 batteries. "Obviously, there were multiple backups associated with the battery to ensure the system was safe against overcharging and overdischarging," Birtel said. "But there was not a specific cooling system associated with the battery."
Cairns called battery management ICs (to monitor voltage and current) an important part of a safe pack, but he also said energetic batteries often need more than that.
"The electrical system that manages the battery is not a complete battery management system," he said. "In my view, a complete battery management system includes the dispersion of any heat that is generated by the operation of the battery. Just having protective circuits is fine, but it is absolutely insufficient."
Wow. Thanks for this, Chuck. Definitely a developing story. I'm delighted to hear that there is collaboration (or at least a coalition) of lithium-ion battery users that are willing to swap experience with these systems. I'm sure this type of information sharing between CEOs has happened since the dawn of time, but I'm encouraged that it can be facilitated by social networking such as twitter and not left to chance meetings on the putting green at the club. I'm sure networking at the Engineer level is still best found at the Dearborn Heights Applebee's, but online story swapping is another emerging development that helps to accelerate the exponential technology development curve...
You raise a really good point about the reasons for Musk's collaboration, Nadine. Obviously, no one but Musk knows the full reason, but I imagine there is an element of self-preservation in this. Lithium-ion batteries are getting a going-over in the popular press right now, and some news stories have wondered aloud if lithium-ion is appropriate for electric vehicles. Whether those questions are fair or not, I would imagine that Musk wants people to know that Tesla's battery configuration works safely because the design allegedly makes better allowances for heat dissipation. It's hard to blame him for that.
Encourage the Liaison Engineers to come forward since they are the fixers who return nonconformances to the design intent during the manufacture of aircraft. Most times the fixes are viable, other times they may be over ruled by circumstances but nevertheless there is a paper trail which defines what's going on.
Encourage the Liaison Engineers to come forward since they are the fixers who return nonconformances to the design intent during the manufacture of aircraft. Most times the fixes are viable, other times they may be over ruled by circumstances but nevertheless there is a paper trail which defines what's going on.
Chuck, Outstanding coverage. It's amazing how all of this is playing out in the online media. But it's also obvious there is engineering and science behind the comments. Keep up the good work.
It is pretty amazing how much media is giving time to the Boeing battery issues. You do not often hear scientific discussion in mainstream media, but the Boeing story has brought out a lot of experts.
Here is a low brainier- GET ALL THE HELP YOU CAN, BOEING!
Tesla has experience with these batteries. Boeing's future rides on a solution to this problem. We all need counselors. Boeing would do well to bring others to the engineering table and utilize their experience.
I hope they already are. Pride has brought down companies and countries. I hope Boeing doesn't let pride get in the way of their future!
Spot-on, Warren! They sound like the typical arrogant EE refusing to admit they overlooked something. On the flip side of that, Musk is trying his best to kill the potential fear-induced legislation that will surely follow the frenzy of unfounded "lithium is evil" headlines.
Since the batteries were probably not online and sourcing current (let's hope their design doesn't require cells all the time), I would look into their BMS/charging system. That's most likely the root cause here.
Give Boeing some credit for all their latest generation satellites using lithium ion batteries, no active cooling, in service for years, nasty environment. They successfully use lithium ion batteries in environments much tougher than the street. Were the batteries tested? Throwing a half billion dollar satellite up with untested batteries would be unthinkable.
The GS-Yuasa battery is just a part of a system. If a part fails is allways not a part trouble is a system trouble. Airbus uses two battery from Saft for the same function.
I am just amazed at all of the irresponsible comments flying around. Tesla in particular is not one to talk. They actually used standard laptop batteries rather than the much more costly space rated batteries in the 787. The Tesla design struck me as total seat of the pants engineering. Me thinks Musk's comments are more CYA than anything.
Obviously something is going on and the folks invloved need to figure it out. Nothing flys on a commercial airliner without a significant amount of history. Lithium batteries have been a subject of conversation in the airline business since the 70's. I'm sure they fully understood what needed to be done.
The NY times article mentions that the batteries have a long history in space applications. I would not be surprised if they did not have a long history in military applications also. The main reason for the use of older technology is precisly that it has a longer history than the next latest thing. The question now seems to be what went wrong.
We need to wait for the results of the investigation.
Here's a short article from EE Times on the history of the lithium-ion battery chemistry, and its original devloper, John Goodenough of the University of Texas:
To say Tesla has no right to talk about battery because they use commercial grade while Boeing used aviation grade battery is absurd. A battery is a battery no matter what grade it is. Fundamental principles are the same. In many case, avaition grade just means there are paper work and trace to go with the product. In many case, there are no difference in quality. That is why you see the trend in military and aviation going to COTS (commercial off the shelf) whenever possible to save money.
Tesla crammed 6,800 laptop cells into a box with minimal monitoring. They blatantly ignored the manufacturers general recommendations.
They may well have gotten someone to agree to this but the point is that the Tesla design was very seat of the pants and not generally condoned. It was then hailed as a breakthrough.
Some breakthrough. Break all the rules and build a big bomb then hail this as some fantastic feat. I call it irresponsible grandstanding. Maybe its OK for a one off sports car but certainly not an airliner.
Lighten up on Tesla. My money is on ANYONE ( I don't care if it's Black and Decker) with several years of experience with tens of thousands of cells in the market place vs. all the computer modeling in the world. I doubt that the computer models on any of the newer technologies are much good at this point.
The manufacturer of the cells is only responsible for the cells if they didn't build the entire battery.
Cramming into a box is the exact opposite of what Tesla did. They gave up a lot of space for cooling and monitoring of the batteries as well as making sure that an individual cell failure (thermal runaway) would be contained. They didn't engineer with an eye toward totally preventing this scenario, but rather containing the inevitable.
Great that you're keeping on top of this story, Charles. I guess now what we're waiting for is Boeing to admit what it has done wrong and then come up with a plan to fix the problem. I was sort of defending them at first but it actually seems like a fairly major oversight to not proivide a proper cooling system...but maybe they thought they did and it was just an honest mistake. I will continue reading your coverage to see how this unfolds! Let's hope it's a good ending for everyone and Boeing sorts this out.
As an alternative to overcharging and heat dissipation how about over discharging? Over discharge damage is the reason many RC enthuiasists charge their lithium ion batteries outside.
Boeing has recieved 100 batteries back from the airlines as defective. It appears the majority have been inadvertently discharged until the battery low voltage cutoff tripped, disabling the battery. In ANA's case 5 of 10 returns were disabled by the low voltage cutoff. Once a lithuim ion battery has gone below the low voltage limit it is very hazardous to charge. It seems risky procedure for the user to bang up against only battery safety stop during routine ground maintenance. Maybe some batteries have very nearly tripped but were unknowingly flown.
Anticipating the question of why don't the battery electronics cut off discharge at a higher voltage, I don't know. It might have something to do with the fact the batteries are also a last ditch power source to keep flying. I can imagine a situation where you would want every joule you could get out of the battery and willingly scrap it later.
I would discount poor high altitude cooling. The batteries are in the pressurized part of the plane, an equivalent to an altitude of 6000 feet so you still have good heat transfer.
Regarding the issue of whether a battery management IC, by itself, was sufficient protection for the Boeing batteries: We asked Donald Sadoway of MIT that question by e-mail, and his response came in after the story deadline. So here's his response, which arrived late yesterday: "We have evidence that whatever the electrical demands are in the 787, the IC alone doesn't prevent fire. So perhaps the IC isn't right, perhaps the IC is right but the execution is flawed, or perhaps there is some other factor like decompression/compression, which is the result of ascent and descent."
The heat developed by these batteries was ignored during design and project management. How can be ignored that 4 batteries have half of surface cooled and by the other 4 (in the middle) less than 1/4 of the lateral surface is cooled.
The case has no openings, the air cooling was not present. The only cooling available was trough the contact between the bottom of the batteries and the case.
Tesla can teach Boeing! They have several years of experience with LI-ION and this should not be ignored by very proud engineers.
It kinda sounds like Boeing engineers were not aware that their Li-ion batteries needed active cooling. You would think the battery supplier would have provided that information or that the issue would have been discovered in testing... Maybe not. Either way, I'm sure Boeing will have the issue resolved very soon.
If I'm not mistaken, these units are intended as a backup power source. If so, they would not be expected to be used significantly during a routine flight. It makes me wonder why these batteries are being completely drained and failing. It seems like this may be a symptom of another problem. Not enough main power?
The point is that Lithium batteries don't require active cooling. They require not getting too hot.
The main reason that active cooling is used is not to cool them while in a failure mode it is to keep them from failing in the first place. In a low load application this can easily be done with no cooling at all.
Adding cooling could be an additional safety risk in itself since it would greatly increase the complexity.
Actually if you recall it was the cooling system that caused the fire in the Volt battery pack!
Having seen dozens of pictures of the battery box, I cannot find any evidence of a physical containment system beyond the sheetmetal case. As lithium batteries are charged, they will physically swell slightly as they approach 90%+ SOC. Uncontained, each charge-discharge cycle slightly degrades internal structures through mechanical action. A prudent design will incorporate structural plates on either end of the battery stack connected with tensioned fasteners, preventing the physical distortion of the battery case by the internal components. '
The failure mode matches this model. Repeated charging slowly degreades the internal structures until an internal short is developed. The short would only be manifested upon charging as the battery once again flexes as it aproaches 100% SOC. The same situation likely occured during the development of the charger when an "event" burned down the development facility.
Ah it's the sheet metal case that apparently kept all the burning pieces inside. According to Boeing there is also a ventalation system to remove any smoke or fumes.
To me this is some level of evidence that Boeing forsaw this sort of failure. It looks to me like the thing got too hot and the safety systems did thier job.
Seems like Boeings only fault lies with trusting the battery maker GS-Yuasa. GS Yuasa was responsible for ensuring that the enclosure had proper cooling. Are we to believe that GS-Yuasa's engineers did not know that these cells packed together would get hot? How can GSYuasa possibly claim to be "experienced" when they let this inadaquate cooling slip by? Everyone else using Li-ion batteries seems to know this. Tesla knows this. Chevy knows this. How come GS Yuasa didn't know this?
There could be a number of folks included in the list. You might add in Thales, the aerospace company that actually made the battery. Then too are the airlines themselves that installed the replacement batteries. It sounds like some airlines had issues and some did not. Maybe there is a maintenance issue?
However, this 787 battery does not seem to be anything very new. It's very typical that smaller batteries like this do not have complex cooling systems. The companies involved have all sorts of experience with similar batteries.
Yes the Tesla and Volt batteries do have complex cooling systems but they are 10 to 20 times larger and are designed for much heavier duty cycles.
These 787 batteries would seem to be failing at times when they are not even in use! This would make cooling a non issue. Something screwy is going on here.
It has been said here many times already, no one knows what happened at this point. It is totally premature and irresponsible to be making all these rash comments. This is especially true of supposed "Industry Experts".
I think it pretty absurd to believe that the manufacturers did not understand what needed to be done. The question at hand is what happened. I'm sure we will all find out in due time.
I thought it might be useful to point out that this all might be much ado about nothing.
In terms of electrical safety, it makes a great deal of difference whether there was fire or just smoke. This may be a fine point that is lost on most folks that are not familiar with electrical safety.
For example, a typical UL safety test will include a test where all safety devices are defeated and the product is evaluated to make sure no FIRE escapes the enclosure during an extreme electrical fault.
Basically the device is destroyed by an electrical surge but it's not allowed to catch anything near it on fire.
A possible key point in the 787 case is the fact that the fire department in Boston mentioned fire. In Japan the report was only smoke. To the layman this might seem like a minor point but to a safety expert it is a big deal.
During the NTSB news conference on 1/24 it was mentioned that the scene was disturbed by the way the fire department removed the battery. Further, apparently the battery enclosure was opened. It made me wonder if there was no fire until the fire department opened the housing. Pure conjecture on my part here.
This also highlights the fact that any sort of cooling system would not normally count in a safety evaluation. It would be shut off just like any other protective measure.
All this talk about the "safety" of various battery technologies is beside the point if the end solution will not cause a fire.
As one with some expecience with safety approvals I thought I would pass this along.
I appreciate the need to take care in using the term "fire" and believe you're making an important distinction here. However, NTSB used the word "fire" in its own press release after the teardown of the Logan Airport parts.
I just had not realized until I watched the NTSB news briefing that there was a question of how the data may have been corrupted by the fire department actions.
It sounded like there may not have been fire present until the fire department opened the battery box.
Apparently in the case of the event in Japan, it was all over by the time the plane landed. The pictures provided by the JTSB show a similar condition of the internals of the battery box but the external conditions seems somewhat more benign.
They do show some nice shots of how the plane was stained by the external venting. I suppose that since the battery lost something on the order of 5Kg of mass there was a lot of Goo being ejected.
This all seemed to be in line with Boeings assertion of how it was all supposed to work. The big departure is that the failure rate in this mode was expected to be much much lower.
One photograph shows what looks like a prismatic cell at the end of the burnt out casing. Was this the type used in Boeing's battery? If so these are difficult to cool because of the geometry BUT if a heavy current is drawn the cell temperature rises rapidly but unevenly across the cell. The risk of internal shorts is high in this scenario. Boeing's spokeperson says that the battery management system(BMS) protects against overcharging and discharging, but does not indicate that there is a thermal cut off system to guard against over heating. Is this what is missing? If so modifications to the BMS to protect against overheating would appear to be the answer.
Apparently, you're right about the high risks of internal shorts, ScotCan. On Thursday, the NTSB announced that the Boeing battery that caught fire in Boston had an internal short in cell number six (of the eight cells). They're still trying to figure out what caused the internal short, though. We've got a story coming up on this in a couple of days.
Interesting. Previous experience of internal soft shorts at the Mallory Battery Co. Of Canada (now Duracell) was to do with a separator change.X rays showed clusters of soft shorts at the base of the cylindrical separator. Certain percentages of HgO (Mercuric Oxide) were allowed in the recovered cathode dust and used in the MnO2 (alkaline) cells. What was happening was that the new separator was drawing oxygen out of the HgO resulting in microscopic globules of mercury which bridged between the anode and cathode, Although that experience was with a primary cell perhaps something similar is happening in the Boeing episode...just thoughts.
going down mainly wrong tracks. There a number of potential problem sources, which could account for the failures. There are no guarantees that there are simple fixes. Prior comment about inbred, NIH. Based on my many decades of engineering involvement, I would like to presnet my list. I do not think Boeing should get a free ride, but a modest recompense, public thanks (technical acknowledgement) should suffice. Sannerwind@gmail.com JR/ CEO
I appreciate Tesla's reasoning. The Batteries require space and channel cooling which will makes them to heavy for airborne equipment. Fact is the battery sensors did not respond is an issue. Since they proved to function then I assume the rapid heating cause the batteries to burst before the sensors detected the problem. Again these batteries need to be enviromentally screen in airborne mil-STDs to see if they can survive high altitude conditions with jet engine vibration. Since they failed too soon in life expectancy this indicates a problem.
Litium batteries are not properly built for space enviroment at this time. They have inherit mechanical design flaws that cause premature failures. in laptops, phones, cameras, now planes.
I find it very difficult to believe Boeing did not test to discover all of the failure modes possible with this battery system. I feel they must have and I would love to see a chronology of those tests and the pass/fail results. I don't suspect they will be published but it would be very enlightening. I think it would be prudent to explore all resources, including TESLA, when trying to find solutions to this problem.
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