Donald Sadoway, professor of materials chemistry at the Massachusetts Institute of Technology, said in an email: "If they get hot, they'll bloat, and the case could rupture. Explosion as a result of autogeneous heating perhaps could happen if one cell in an array caught fire and the fire spread. But I'd be surprised if a single cell would explode."
Experts also said that prospective EV buyers and owners should not worry that their electric car batteries could explode during a collision.
"If a battery is operating normally and there's a collision that causes the cell case to rupture, the contents would still be at normal temperatures, and you wouldn't have an explosion, or even a fire," Cairns said.
Battery experts emphasized that lithium-ion batteries contain a flammable electrolyte, which has a well-understood fire risk. But they said today's conventional vehicles burn gasoline, which also carries a fire risk.
"You have to put it perspective," Cairns said. "The fire danger from the battery is still far less than the fire danger from a tank of gasoline.
For a close-up look at GM's Chevy Volt, go to the Drive for Innovation site and follow the cross-country journey of EE Life editorial director, Brian Fuller.
"@Stuart21 - Your proposal is exactly what is wrong with so much of the world today."
1. You do not make your case with relevant facts. Something like "27% of all cars on the road today will end up submerged" could be a good start if it were true. The actual number is likely so small that everyone would see its true relevance.
2. Just like a politician you bring up an issue in isolation with one or two specific examples. A true crusader would 'rack and stack' all of the fixable automotive issues and illustrate that you issue was at the top of the list.
3.One thing that I know after bringing products into the marketplace - When I am doing the work, it is very easy for me to underestimate the cost and effort - when someone else is doing the work outside of my workplace, it is almost guaranteed that I will miss any scope and cost estimates that I might make. This is especially true in the automotive industry where what would be a 1-2 week change at a computer company could be a 6 month or more effort at a automobile manufacturer. Afterall, you do want the manufacturers to thoroughly test for unintended consequences.
4. I thought that an insurance company's job was to assess risk and set a price to cover that risk.
RE:"Are you saying that this vehicle must be scrapped?"
Quite the dramatic statement. The vehicle is still worth several thousand $USD.The insurance company probably totaled it - assuming the owner had a valid claim and didn't just drive on thin ice.
Why was it parked at the bottom of a lake??
Was it your car??
Do you propose salt water and fresh water be covered??
Would there be a depth limit??
Oh, did I mention that your problem analysis is flawed?? It is true that the 'tall pole issues' are expensive electronics, but that is not the whole story. Having repaired a few vehicles that were only half submerged due to flooding, a few other issues that come to mind are: mold [a delayed effect], connector failure [often delayed] due to corrosion, failure of any light bulb socket [delayed] due to corrosion, gas gauge sensor failure due to corrosion, relay failure, CV or U joint failure [delayed] due to water trapped inside, failure of any swiches due to water trapped inside, catalytic converter[s] failure, radio speakers failure, CD-ROM failure, radio failure, possible leather upholstery failure, failure of some of the 1-2 dozen motors and solenoids, extensive labor to remove water from places that it should not be [motor, transmission, differential, dash instruments, doors, various inaccessable interior nooks and crannies, etc.] - Oh, I forgot, we will also waterproof these areas. It might be easier to adapt wheels to a submarine and only sell 'dunk insurance' to folks that purchase such a vehicle.
It is absolutley ridiculous that a very expensive vehicle should be scrapped because of a few hundred dollars worth of electrical components - most of which can be waterproofed anyway. It is an SUV fergorsake - they are designed for the rough stuff. Or should be.
And those that merely 'appear to be' designed for rough stuff, it should be at manufaturers expense for repairs that would not be required with proper design.
While I worked for Panasonic Factory Automation, I spent a lot of time at Celestica, then a subsidiary of IBM. To reduce pension obligations, most employees were employed for 12 months, with a possible 3 months extension. Some of the Celestica employees thought that I was also a Celestica employee. I was often called to look at a machine problem. Several times it was a problem that I had seen before and I knew what adjustment was needed. The frequent rotation of Celestica employees meant that they did not have that continuity of experience. Their plan was to replace experienced employees regularly, an intentional brain drain.
Something doesn't quite add-up with GM's claimed theory cum 'explanation' that an accumulation of hydrogen sulfide gas (H2S) vented from deliberately overcharged prototype (presumably Lithium-Sulfur chemistry) A123 batteries caused the large explosion that damaged their battery R&D facility. This purported explanation for the recent blast seems implausible because venting of flammable gases from failing, overheating batteries is a long-well-known phenomenon. That being the case, the new purpose-built lab (built in 2009) would have been deliberately designed with best practices air-handling/ventilation systems that can rapidly turn-over and exhaust air from test areas in the facility to prevent just such a build-up of flammable vapors from ever accumulating to the point where large explosion could potentially occur. Why would that important, built-in safety support system have magically failed during this particular incident? It doesn't make sense. Second, GM publicly claims that the catastrophically failing battery pack was supposedly fully intact after the explosion --- frankly, I don't believe that 'fact' either.
Readers may be interested to know about the existence of another little-known type of Lithium battery failure mode that albeit rarer, may even be more serious than 'simple' overheating.According to a Japanese Li-ion battery manufacturer, it happens randomly in roughly 1 out of every 4 to 5 million battery cells, regardless of their chemistry.
This somewhat obscure type of failure mode is cryptically called a "field failure" by some battery manufacturers and involves catastrophic thermal failure of a single cell. While it is often thought to be associated with internal shorts and electrical arcing within a somehow defective cell, battery manufacturers admit privately that this peculiar failure mode is not well-characterized and very poorly understood --- they are presently at a loss for ideas about exactly how to mitigate such a problem. Scarily, they are well-aware that if just a single cell in a large, multi-cell EV battery pack fails in this particular manner, it can potentially trigger an even more catastrophic large-scale thermal runaway event that rapidly propagates through an entire battery pack, destroying adjacent cells via thermal fratricide as well as possibly the interior of an EV.
In May 2010, academic researchers at Oxford University published a new and perhaps important paper that many believe implicates the involvement of Lithium metal dendrites in a significant number of Li-ion battery failures (please see R. Bhattacharyya et al., "In situ NMR observation of the formation of metallic Lithium microstructures in Lithium batteries," Nature Materials9 pp. 504 - 510). What is of great concern from a safety standpoint is that nanoscale internal metal dendrites that are prone to shorting-out grow spontaneously over time as a battery ages and goes through many charge-discharge cycles.A battery pack may be perfectly safe during the first months of ordinary use; however, dendrites grow inside over time, increasing the probability of dangerous internal electrical shorts as time goes on. The problem is that nobody in the world has any working experience with extremely large multi-cell Lithium-chemsitry battery backs used for periods of many years. Lastly, nanoscale internal metallic dendrites can potentially form and grow in almost any type of Lithium battery chemistry.
I agree completely.I retired from Roper (GE owned company) and it seemed as though we had to keep learning the same lessons over and over again. Each year, GE demanded a 10% headcount reduction and that included people from the engineering staff.With retirements and reductions, we ended up with a fairly young staff.We lost the history and experience that, in my opinion, makes a company viable and provides transparency between the "generations".I think this is an ongoing problem with manufacturing and when you add movement of companies to off-shore locations you lose entire generations.For some industries, we are becoming a nation that doesn't really know how to design or produce.Please note, this is my opinion and I certainly welcome rebuttal.
There may be more to the story that I can share. I am in Detroit and I did work for GM for 25 years including 5 years on EV1, almost 20 years ago. I quit over lack of intelligence in management.
SAE has some very destructive standard battery tests and this was probably a test to heat the batteries to 200 degrees C above ambient (about 375F). Very severe but necessary test to see what happens and what gases are released.
It was mentioned in Detroit that Hydrogen Sulfide was present (commonly known as sewer gas) which will explode. (in auto industry we refer to this as a thermal incident). I do not know what created the H2SO4.
My belief is that when GM retired out all of their old dogs and then hired a bunch of new college kids, they loss an incredible amount of knowledge, skills and experience. I truly believe, the test people were playing video games and then a bell rang and they said OMG! and then the thermal incident happend.
I think it is fortunate that only one person was hurt, but it does say something about keeping your old dogs around. Experience tells you why it is important to follow test protocols and procedures very carefully. They probably didn't. No excuse for this.
I think the same issue occurred in the design of the Volt battery pack. I'm an old dog and one look at the pack, I knew they were not going to be able to retain the cooling fluid consistantly in production, let alone in a crash shake-up. When 50% ethylen glycol is allowed to evaporate, pure ethylene glycol does burn. Thus the several months between crash and thermal incident.
Quite frankly, I applaud the efforts of General Motors for making an effort to know more about their product than anyone else—in this case the EV battery.I retired from General Electric Appliances and we always applied ETPs (Engineering Test Procedures) to products just to see what would happen if and when they were misused.These ETPs were "over and above" all third party standards existing to qualify an assembly and deem that assembly safe and functional.I am sure GM has laboratory test procedures governing the test itself and defining pass / fail criteria.I definitely agree with "mellowfellow" in that hyperventilation rules the day and certainly the media relative to technical issues.Mark Twain was correct when he stated: "It ain't what we don't know that hurts us; it's what we know that ain't so".Let's let GM do their thing!
One three letter word jumped out at me - LAB. IMO, anything that happens in a lab - good or bad - potentially has no relation to 'real life'.
I am tired of media sensationalism. If there is a bit of a storm somewhere, the 'news' becomes consumed by the 'news about weather'. The formula seems to be that if the subject has FUD [Fear, Uncertainty, and Doubt] potential, take it to the extreme. Boring subjects, like a fabric fire in a clothing plant, do not include the FUD factor so we do not get stories about the dangers of wearing clothing.
Every lab 'incident' that I can recall with my questionable memory has had it root cause traced to human error [and then sometimes covered up by some 'mumbo jumbo' to confuse management].
How did part of this discussion wander off into how vehicles survived submersion? Most auto companies don't intend for their products to be used under water. Although the old JEEP could be run under water if that option was installed. At least that is what I read. Immersion of any vehicle not intended fr immersion would call for getting water out of a whole lot of places that it was never intended to have water in. But that is a whole different thing.
Good points, William K. Based on my discussion with experts, I think there's a possibility that the blast doors did exactly what they should have -- open automatically in the presence of a gas release. I'm waiting for additional information...
A half century ago, cars were still built by people, not robots. Even on some of the countryís longest assembly lines, human workers installed windows, doors, hoods, engines, windshields, and batteries, with no robotic aid.
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