A CT scan image of a battery cell shows breakdown of layers directly below an indentation. A recent report from Underwriters’ Laboratories Inc. suggests that such dents in the casing are a possible failure mechanism for lithium-ion batteries. “The resulting high stress/strain will lead to a mechanical failure of the separator (with failure of the casing), allowing for direct contact between electrodes at a distance only a few layers below the casing surface,” the report says. (Source: Underwriters Laboratories Inc.)
Chuck, Didn't Tesla get a top safety rating just recently for the S? This is a problem with EVs (and hybrids) that use Lithium Ion batteries. I am not sure that the testing agancies really know how to characterize the failure modes of these batteries. As I have mentioned before, there was an incident in China where an all electric cab of local manufacture caught fire and burned up the driver and passengers completely after a collision with a car that drove away. This is very worrisome.
You're right on the money, naperlou. Yes, Tesla has "fives" (best rating) across the board in NHTSA's safety ratings. And, yes, the methodology for the ratings is well established. I agree that the ratings agencies don't yet have a handle on how to characterize the relatively new phenomenon of lithium-ion failures.
So the Pinto, Chevy saddle tanks, and the recent Jeep recalls should all be put aside if we let the Tesla get a pass?
On the otherhand, debris is a part of the road. If consumers expect the cars to be 100% safe, then the only solution is to get rid of the car. At least in this instance, the driver was able to pull over and get out. In fact, I think this was explicitily discussed when many here at DN were critical of the Boeing batteries. Lithium ion chemistry in an airplane, not so good as the option is a plane crash (or crash landing). But in an automobile one could pull over and get out of the car.
I would imagine that all of the tests that Tesla got a high rating for were for crashes at various speeds and angles which are of course typical for a car and all front, rear or side.
If the failure mode has been correctly anticipated one should point out that this sort incident downed a Concorde in France a few years ago. There a fragment of a previous landing of a different plane was catapulted up by a tyre and hit the underside of the wing and a piece of that splintered off and ruptured a fueltank or line.
The problem here is that floor strikes have traditionally not been an issue for cars with the tank sitting high to the rear and if it did leak it had to be combined with sparks for a disaster. With a battery of course sparks are a given.
From memory when I saw the Tesla tear down the battery was almost integral to the frame.
BTW, one of the tests that they do when an airbag module is being calibrated here is to hit the floorpan with a hammer really hard to ensure there is no deployment. I wonder if Tesla does that.
Which reminds me, I was driving this past weekend and slammed my floorpan on the ground due to the road being a little uneven and nothing much happened. It seems to me that the vertical impact strength of the Tesla battery would have have meant that it did not come off so lightly.
Wow that is scary stuff! It's unfortunate this keeps happening, because it certainly isn't going to do anything to promote the use of hybrid vehicles and EVs. It's especially troubling because of Tesla's high rating, as Lou points out.
Since the Tesla Model S batteries can be swapped out in a few seconds at their roadside stations, there must be some sort of quick release that would make it possible in an emergency to drop the battery pack and roll the car away from it, thereby saving the vehicle in case of battery fire.
Perhaps there should be a small, separate battery just for the purpose of driving the vehicle a few feet to get off of and away from the dropped main battery.
Ken, my understanding of the battery swap out machine is that it simultaneously unscrews a large number of bolts, drops the battery down, then raises another battery up into place. Reportedly, it is the same piece of equipment they use in the factory. It is not a mobile piece of equipment. In videos of it working, the car is driven up over the device. This is not a quick relesae mechanism. The device reportedly will cost Tesla $500K to intsall.
If the battery is susceptible to being breached the way this one was, any auxiliary battery would be susceptible as well. If it was anywhere near the part tha caught fire, it would also catch fire. Also, the battery weighs over 900 lbs., so I am not sure your idea would work.
I think the idea of having the battery basically cover the bottom of the car is a very bad one. This could prove their undoing. Now they will probably have to put some sort of shielding there. That will increase the weight even more.
apparently the battery has an armor plate beneath it, 1/4" thick. However,
hit something hard enough, fast enough and it will rip through almost anything.
Lets not forget some minor ice sank the Titanic.
Now that said, Lou's idea of dropping the battery pack isn't neccessarily a bad idea.
if you have a fire, it would seem easiest to have some explosive bolts on the body side, that would cut the structural attachments and let the battery drop off. You would need a small internal battery to drive away, but, it could be done as a future upgrade.
Eject the Lithium! - just like the Enterprise (NCC-1701) can eject the warp core along with the di-lithium cystals in case everything goes to hell in a hand basket. Impulse power only to maneuver away from the core.
When I read your post, I found myself humming the 'Speed Racer' theme song (from the cartoon, not the abomination of a movie). I pictured the hydraulic jacks popping out at the press of a button on the steering console and the sound effects ''don-don-don-don-don" as the vehicle pole-vaulted away from the flaming battery.
The unfortunate drawback of your suggestion is that there would need to be a fire sensor in the battery compartment to jetison the flaming cells and then the car behind you would not only hit the metal piece but also run over the flaming battery. That is not a very safe thing either, considering the car behind you would likely be a gasoline powered model. A safer mechanism might be a fire suppression system with a battery cutoff so the car stops and you know to get your ass out of and away from the vehicle. Of course, the best bet would have been for the driver to NOT hit the metal object in the road, but if you can afford to buy a Tesla Model S, you have enough dollars not to need common sense (pun intended). Maybe Tesla needs to re-examine the road clearance and either raise it, or put a metal skid plate on the bottom to protect the battery compartment. Yes, that would increase the mass of the car and decrease the ability to get those super-fast highway speeds that Tesla loves to market, but hey, don't you want your customers to buy a second car from you? They can't do that if they die in the first one!
"Such occurrences are rare, however. A Tesla spokeswoman told Design News that the Model S has collectively been driven 83 million miles at this point, with dozens of known accidents, and no such battery problems, until now."
Seems to me that this is a misleading statement and is a poor defense for Tesla battery safety. 83 million miles refers to driving distance but does not take into account an impact with an object - and "dozens of known accidents" does not give any quantifiable data regarding this specific issue.
I've seen many a car fire in my lifetime, even experienced a minor one.
I saw a brand new Corvette burn down to the block, frame, and rims that had been been in a ticker tape parade for a world series win. (A pile of shredded paper it had plowed over started on fire underneath it.)
There was an accident in Chicago a few years back where a van full of kids was engulfed in flames because of road debris which punctured the fuel tank.
Car fires of varying degrees occur every day somewhere in America, without people clamoring for safety changes. Let's keep in perspective that the fuel load of any ICE powered car can be every bit as bad, and these thin fuel tanks are often less protected than the Tesla battery. The sky is not falling on Tesla because of one incident.
Ken E., that is not true. Car fires in many models of car were a great concern in the past, especially fire on impact. Remember the Ford Pinto in the 1970s. Just looking this up in on the web, there is recall on Ford trucks from 1997 t0 2003 becuase of concerns about a fuel tank straps that could be a problem in high corrosion areas. There certianly is concern about fires in cars, and they have become much more safe. It is a problem, but many car fires are like the first one you mention. This is a concern, but based on the number of vehicles and miles driven, it is not as big an issue as it might be with the Tesla. Also, the chemicals involved in the Tesla fire are a lot more dangerous. Based on your examples, one would conclude that the Tesla battery placement is badly flawed and it will be interesing to see how the NHSTA deals with it.
Napaerlou, what is 'not true'? That car fires still occur? That fuel is combustable? That we don't need perspective? Here's some perspective for you;
From the NFPA; In 2003-2007, U.S. fire departments responded to an average of 287,000 vehicle fires per year. These fires caused an average of 480 civilian deaths, 1,525 civilian injuries, and $1.3 billion in direct property damage annually. (Issued in June 2010)
I see no correlation between my examples and Tesla, except that they were car fires caused by unique situations. I base no strong conclusions based on any single incident.
Sure, cars are much safer than in the past, but how much safety must be demanded, particulary from a lone case? Although I'm sure NHSTA is having discussions about this, presumably they will have to have a larger data base than one to justify major changes to testing. Far as I know, the NHSTA does no testing of debris puncture of undercarriages or fuel tanks, on any car.
In this age, the most unsafe and deadly thing about any car out there is the driver, and we demand precious little testing of them.
Yes, let's maintain perspective. Let's not allow unsafe vehicles on the road just because they are relatively new. Steps need to be taken to minimize the damage to batteries in a accident or to limit the resulting fires!
Critic, your moniker suggests you are more prone to criticism than thoughtful evaluation. My neighborhood has a hot rod gathering nearly every weekend in the summer with hundreds of cars, many of which put fuel tanks in all sorts of potentially dangerous and completely untested places. And surely you've noticed those big fuel tanks completely exposed on both sides of virtually every high tonnage truck on the road? Not to mention the tankers being pulled by them!
Every new car from Detroit ends up on the road after passing the tests, and the new Tesla passed the same ones. Like those other new cars, additional data supplied by accident statistics is going point out the issues and extent of danger, not the assumptions on both sides of the issue I see here.
Statistically speaking, this single incident is a risk which at this point, only applies to the potential purchasers of Tesla's. Combined with the five star safety rating, it seems totally exceptable to me, if only I could afford a Tesla, and it's limitations.
It seems engineers are as apt to jump to conclusions and hold them as hard as the technically less endowed. Engineers with imagination are wonderful, but even the most innovative of those, without any analytics, will suffer.
"Yes, let's maintain perspective." Cars are too expensive as it is. Physics and economics cannot be ignored. In order of priority, where do you place safety, weight, fuel efficiency, cost, and usefulness?
If safety is your primary goal, above all else, we should all drive Mine Resistant Ambush Protected vehicles (MRAPs). 3 miles to the gallon at a cost of $500,000 each. If you can't afford that - Stay home! That's the safest place you can be.
This talk about adding weight and cost to a ALL vehicles because ONE car started on fire is ridiculous. I want to see a $10,000 two seater EV with a 40 mile range. That addresses the needs of about 80% of the population and I think they would sell like hotcakes.
...An no, I don't drive a $1500 EV scooter because I don't think they are safe and wouldn't stand a chance against an 8000 pound Escalade.
I want to see a $10,000 two seater EV with a 40 mile range. That addresses the needs of about 80% of the population and I think they would sell like hotcakes.
How do you get a 2 seater addressing 80% of the population. That excludes all families with a kid, grandparents who would like to take grandchildren anywere and any body who would like to go anywere with more than one other person. Their is a reason why their are very few 2 seater cars made almost no one wants one unless your going through a mid-life crisis.
This kind of vechile would only work as an optional vechile for most people so now we need a standard ICE and your 2 seater that will save a lot of money,
"How do you get a 2 seater addressing 80% of the population."
Most households have more than one car. I'm not advocating a two seater as the household's only car. Just the second one. Specifically for it's limited range and occupancy. Have you ever spent any time out on the road? Most cars have one person in them. Why haul around a 5000 pound, 5 passenger SUV when all you are doing is going to work or the store? Leave the tank at home for the few times you do need it. That's part of the reason that the two seater has to be low cost. Very few people are willing to pay MORE for a limited range EV when their full size ICE car will do everything and cost less to buy.
Of course, the other obvious reason for a two seater is to limit the size and weight of the vehicle, further improving the range with a small battery plant.
The Smart ForTwo EV is getting closer, but for $25,000, I can buy a fairly nice ICE sedan or crossover.
You're right that most cars have one person in them on today's roads, g-whiz. The accepted average number of people in a vehicle at any time is 1.4. I don't know how well that fact translates to sales, but it's absolutely true that a minority of cars have more than one person in them.
As I stated when people were crowing about the 5* rating of the Tesla. that the tests were based upon tests written and designed for common ICE failures. Many of the tests were added after failures on the road of vechiles. example (rollover -jeeps, reend collisions-Pinto). They have not updated their tests for the specific dangers presented by Battery vechiles. Many of which will not be know until tens of thousand of units are on the roads for years.
Kinda of scary but also sadly how it works. We know batteries can melt down from minor damages, that is what caused this fire. What other failures are out their that we do not know and may not know for 3-10 years
I wonder if Tesla will replace this guy's car under warranty?
I've been involved in designing machines using sizeable Lithium Ion batteries. We've had a couple "thermal events". It's not a pleasant thing.
I've also witnessed car fires in gasoline powered vehicles. In fact one burned in my driveway years ago. As a foolish teenager I got in the vehicle and put it in neutral and rolled it back from the house. I then put it out with an extinguisher.
We get all worried over a battery fire, but we don't think twice about carrying around 20 gallons of gasoline. Ever witnessed a car fire? If the fire spreads to the tank it's lights out. Typically however, the fires starts in the engine compartment and never reaches the tank in the back of the vehicle. There's usually enough fuel pressure in the lines to create a nice fire in the engine compartment anyway once things start melting. That's when tires explode.
Electric car manufacturers are going to have to find ways to protect the batteries. The massive size of the batteries tends to mean they are distributed throughout the vehicle. This complicates the safety aspect. But they'll figure it out, it'll end up being a compromise -- like every engineering decision -- between cost, risk, and performance.
I had an '88 Dodge Shadow that went up in flames in my driveway. The fuel system had a small leak on top of the engine, I wasn't yet sure which connection it was coming from and it didn't look serious enough to worry about so I drove the car to work one more day. After the fact, I remember the engine backfired right when I shut if off back home. That must have been when it lit the leaking gasoline on the intake manifold. A few minutes later I was inside checking my email when I hear what sounded like a couple car doors slamming shut, so I go outside expecting to find someone out there. My car had flames rolling up the windshield from underneath the hood and there was a pool of burning gasoline on the ground in between the front tires. I grabbed a garden hose and tried to put it out but it seemed to be getting worse and then I saw that the windshield was cracked and the car was likely totalled. So I paused to evauluate the situation, that's when I realized the fuel pump was on and pumping gasoline into the fire. I tried to get the hood open but the release cable had melted apart, there was no way to reach the battery from underneath and it would take too long to find something to cut through the hood. So I got in the car and let off the parking brake, put it in nuetral and rolled the car back down the driveway. Reset the parking brake and got back out fast as there was a lot of heat coming through the windshield. The door was wide open the whole time I rolled it back. Then I thought to go underneath the back of the car where the fuel tank is, and pull the wires coming off of the tank. I couldn't get the connector apart so I just pulled hard enough to break the cable apart. This disconnected the fuel pump, and stopped adding fuel to the fire. I later discovered that the relay that controls the fuel pump has it's wiring running right behind the engine along the top of the firewall, so that it can be run down the opposite side of the car from where they decided to put the relay. This wiring had melted together and shorted during the initial fire, this in turn kicked on the fuel pump and made a small fire into a very serious fire. I was able to get the fire out after cooling it down from all sides. That car was a total loss. The radiator was half melted, firewall looked like it had buckled, adhesive along the bottom of the windshield had started to disintegrate. Carpet inside the car was scorched. Nowdays, I find myself considering the routing of wiring like that on other cars.
The batteries are made from highly reactive material that are prone to thermal runaway issues. unlike a fuel tank which needs puctured and then an ignition source all you need to make the battery compartment flame is a good strong dent in the pack.
the scariest part about this, you can get a dent that causes a slow discharge that over the coarse of an hour or 2 goes thermal. So you could damage your battery compartment and then not have it go into runaway until after you park it in your garage.
First- It was speculated by the driver .. there MAY have been an impact with something on the road before the car became disabled and the fire started (it is NOT known an "impact caused a Tesla battery fire").
Second- It MAY be a battery fire (?) .... it isn't known yet.
Third - I am sure this car's remains will be reviewed by many teams of qualified people with much more information than presented here. Everyone will want to determine the cause of this fire.
Nothing ... other than the questionable action of the fire fighters is known at this time....(water with Lithium? reallly? water use for most oil/petroleum product fires is questionable). Watering down a burning car.. only useful in keeping surrounding area from catching fire or keeping the vapors in a gas tank from exploding- which doesn't appear be a risk in the video.
Saw the promo letter Elon sent out. Denting a thick piece of steel had to come from something in the road. Let's face it, looking at the big ppicture, if that road debris punctured a gas tank or gas line, the guy might have fried before he even got off the road.
I would like to comment that when I saw the video it certainly looked like a serious fire indded. I have seen a few fires and in all cases, before the flames got that high, the passenger compartment was on fire as well. And I understand that in this case the passenger compartment did not burn. That says a great deal for the integrity of the body and the safety of the passenger compartment.
As for hitting some object, an ordinary push-broom can have the handel go through the grill and radiator and bash into a number of things inside and start a serious fire, and not leave any visible damage, hardly. So we will need to wait for the report from all of those qualified investigators instead of listening to the conjecture of those not qualified to change a flat tire or even pump gas.
Just because somebody is a persuasive writer does not mean that they have any understanding or any knowledge at all about their subject, and this has been made very clear in the many press releases and postings on this unfortunate event.
As you probably saw, William K, Elon Musk offered his viewpoint on the fire on the Tesla website. Tomorrow, Design News will have an article in which four experts offer their opinions, based on the information in Musk's blog (which, right now is the only information available).
Charles, reports by experts is what I have been hoping for. When the news media people get going I think about that song from quite a few years back, "dirty laundry", and I consider that while they talk skillfully, it is very hard to pull substance out of a vacuum. But tomorrow we will see what has been found.
Unfortunately, William K, the experts will be providing their opinions based on Musk's statement. There's still no physical examination, and I don't believe NHTSA will examine it in greater detail as long as we have a government shutdown. So...we can't provide the kind of information you're hoping for right now. When the government is back up and running, maybe that will change.
That is unfortunate indeed. That shutdown is having the desired effect, which is to cause the rest of the people pain and suffering. It has no other purpose. The goal is for us to demand that congress do whatever they want just to stop our pain. It is a lot like torture, which is supposed to be illegal in the USA.
Sorry about the political comment, but I do feel the pain already.
You'll have to take it up with Tesla, Rigby5. If you noticed, their statement said, "...the fire in the battery pack was contained to a small section in the front of the vehicle." They also acknowledged this in a phone copnversation. Also, if you read Elon Musk's blog, he said, "A fire caused by the impact began in the front battery module..." Those statements are good enough for me. I do agree with you, however, about gasoline engine fires. A gasoline tank has far more energy than a lithium-ion battery.
In all the FMVSS (Federal Motor Vehicle Safety Standards) there is not a single test for any vehicle impacting anything on the roadway that is higher than the vehicle clearance.
There is not even any standard for minimal vehicle clearance on Federal Level and the only State that has one is California where no vehicle component can be lower to the ground than the "rim" distance from the roadway, so effectively with ultra low profile tires you can have one inch ground clearance !!!
Also there is no FMVSS for flammability of anything on the vehicle other than FMVSS #302 that is specific to any components on the interior, originally put in place to demonstrate that lghted cigarette can not start fire inside of the vehicle if accidentally dropped.
As images of burned FISKERS show the better part of the vehicle can burn just due to "short" in 12 V DC motor (cooling fan).
In TESLA the battery is the entire underside of the car but starts about 20 inches from the Front axle, all the fire images are of the FRONT of the car, and no real flames from the "battery pack".
The latest of course is that a strange object exherted 25 tons of force adn punched 3" hole into the battery pack front module.
I personally find that scenario very hard ot believe.
Unfortunately there are three sets of NHTSA standards (well 4 if you count school bus as a separate category).
Cars - the safest group with items mandated that suppose to make inept and incapable drivers "safe".
Trucks - (Durango is truck and so is Jeep) that do not need as much safety equipment, since they are "trucks"
Over 10,000 lbs - they have standards that are same as cars had in 1980's even today.
When the FMVSS were developed, only use for trucks was "business" and "Construction".
Good intentions of forcing people to buy and OEM to make high MPG vehicles, killed large sedans and ever popular family vehicle - the station wagon - and moved pople into trucks, for simple reason they still wanted POWER and A/C that worked and mostly the "room".
This made the Pick-UP (like F150 and Chevy) the World's Best selling vehicles and also gave the birth to SUV, not that Suburban did not exist, just that people did not notice them before FORD came up with the Explorer.
Trucks now by numbers are even with or outsell cars so it would make sense to make them confirm to the carlike standards.
OEM of course oppose to any such move, claiming that would make the Truck and SUV unable to be used "off-road" (like low bumpers).
NHTSA is in some instances is very slow; like to introduce roof crush requirements for CARS took over 20 years.
Yet to force OEM of cars to add ESC (Electronic Stability Control) was on the spot just quiting her job after 6 months absence ex-NHTSA administrator idea (probably not her own), she signed it into law and quit.
So at times public has not even a chance to comment or influence the decision that year later affect 7 million new cars and about 8 million new trucks.
NHTSA and DOT people on the top are not elected in any way they are political favorite appoinetees usually with not even a clue what a car is.
That is something that need be changed FIRST, or we all will be eventually required to drive self guiding vehicles while packed in big inflatable bubble, as we need to be "safe"!
Of course, if you want to kill yourself then you just buy "motorcycle" no real safety requirements there. Not now and none planed for the future.
Whenever you have a concentrated energy source, some crashes will cause a rapid release of energy resulting in fire. You simply cannot engineer for every eventuality. This has been proven true of gasoline, deisel, aviation fuel, hydrogen and of course batteries. All we can hope for is to make the apparent statistics acceptable to the public, which makes it rough for new technologies. Remember the Hindenburgh and the Concord. Even though pipelines are statistically the safest way to transport oil, that is not the general public perception.
How many cars have been engulfed by flames from fires started by their conventional 12V electrical systems? My local wrecking yards has plenty of examples. Of course it doesn't help that most car components are flamable (or inflamable if you prefer). If we haven't been able over the last 100 years to engineer the conventional gasoline powered cars' electrical systems to be failsafe, there is simply no hope for electrical cars to be failsafe.
The question of whether engineers could have foreseen the shortcut maintenance procedures that led to the crash of American Airlines Flight 191 in 1979 will probably linger for as long as there is an engineering profession.
More than 35 years later, the post-mortem on one of the country’s worst engineering disasters appears to be simple. A contractor asked for a change in an original design. The change was approved by engineers, later resulting in a mammoth structural collapse that killed 114 people and injured 216 more.
If you’re an embedded systems engineer whose analog capabilities are getting a little bit rusty, then you’ll want to take note of an upcoming Design News Continuing Education Center class, “Analog Design for the Digital World,” running Monday, Nov. 17 through Friday, Nov. 21.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.