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Electronics & Test

Road Debris Causes Another Tesla Model S Battery Fire

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naperlou
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a trend developing
naperlou   11/11/2013 8:44:43 AM
Chuck, I see a trend developing.  Three of the same type of accident in a month is a big number.  This is especially true if you consider the relatively small number of cars on the road.  I know that the Tesla S has sold well for a car in that price range, but it is still a small number compared to more mass market vehicles.  While the NHSTA claims that they found no violations of Federal safety standards or defect, this is probably because they do not really have enough information on these types of vehicles.  Frankly, Federal regulation in these areas tends to follow rather than lead. 

NadineJ
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Re: a trend developing
NadineJ   11/11/2013 4:31:03 PM
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The word trend isn't quite right but I agree that the laws and standards lag behind the technology.

It's more of a wake-up call.  I read that Tesla's investors filed a lawsuit last week stating that they had been "mislead".  I doubt that the company lied.  I think they got ahead of themselves on some things.

ck_02
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Re: a trend developing
ck_02   11/12/2013 9:06:30 AM
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@naperlou, I wish to point out that there were only two incidents of this type, rather than three. The incident in Mexico involved a tree and a concrete wall. In my experience, that spells disaster for any vehicle. Cars just aren't meant to go through them. :) I'd have to say that I do agree with your point regarding the standards following rather than leading though.

Watashi
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Re: a trend developing
Watashi   11/12/2013 3:18:55 PM
Obviously there is an issue with the battery protection scheme on the Tesla.  It is not that big a deal, just different than the populous is used to.  Unconventional cars will have unconventional issues.

I don't think that Tesla misled anyone.  Designs are evolutionary.  Almost every new car model, regardless of model history will have bugs to work out.  We purchased a new Dodge dart for my wife just after it came out.  No novel technology there; but all I can say is thank heaven for the warrantee.

Tesla engineers aren't dumb (I am assuming).  They will analyze the spate of incidents and Mr. Musk will have to figure out the best way to roll in the design modifications.  Otherwise, the market will take action and we will only see Tesla in museums.

I do take issue with your statement regarding federal regs.  The intelligent engineers in industry will solve their own problems.  The last thing any of us need are a bunch of back-benchers playing Monday morning quarterback.   The NHSTA gets things wrong as much as they get things right.  They are also heavily influenced by politics.  I vow to eliminate them in my first month as President :)

GTOlover
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Re: a trend developing
GTOlover   11/12/2013 3:55:27 PM
If the burning of Tesla continues, I am not sure that museums will want the car in their collection (or least the batteries will be long gone).

Could you also get rid of the IRS in your first month as President?

Watashi
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Re: a trend developing
Watashi   11/12/2013 4:00:10 PM
I'll try, but they would probably audit me for my whole term!

jhankwitz
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Uncommon Trend?
jhankwitz   11/11/2013 12:13:28 PM
This may appear to be a trend, at least from a media perspective. These three incidents have been widely published by the media. Funny thing is that our local Fire Department responds to automobile fires on a regular basis, but I never hear about it in the news. This makes it difficult to determine if these 3 incidents are common or significant. 

It would be best if the Model S was recalled and fitted with armor in response to the media hype if nothing else.

Allen Koco
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Re: Uncommon Trend?
Allen Koco   11/11/2013 1:54:59 PM
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Each accident involved a different kind of obstacle. Reinforcing the armor plate will impact the cars weight and possibly make the front end heavier. In addition, the center of gravity may change. Impacting the performance. As noted in Elon's post nothing can prevent a 25ton force from punchering the the armor plating. They should consider retofitting the cars with an impact grill. A device that is mounted onto the front of the car, and lowered by the driver when needed to push debri out of the way. A ball hitch and curved metal piece would not impact the car thereby protecting the car's battery.

jhankwitz
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Re: Uncommon Trend?
jhankwitz   11/11/2013 2:57:45 PM
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The front bumpers on my cars are already too low, causing severe scrapings whenever I park in a lot with curbs.  I can't imaging trying to drive in snow with a low grate plowing the roads and highways wherever I go.  They protect gas tanks, they should be able to protect batteries.  

Toaster
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Re: Uncommon Trend?
Toaster   11/12/2013 8:42:20 AM
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I agree that a simple mechanical fix would reduce the risk, However, since this is a new technology, people are afraid. (People were afraid of the automobile at first too) There wil be calls for automatic fire supression systems in the batteries.... Just wait....

GTOlover
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Re: Uncommon Trend?
GTOlover   11/12/2013 9:45:25 AM
Allen, do you mean something like the cow catcher on old steam locomotives? Not sure if that fits with the Tesla design, but it would be cool to see people move when you come up behind them!

Watashi
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Re: Uncommon Trend?
Watashi   11/12/2013 3:50:28 PM
"...nothing can prevent a 25ton force from punching the armor plating."

Actually, a redesigned armor scheme would prevent it. Raising the CG a bit isn't going to hurt the handling that much. However going to real armor could impact the battery range. There is always some trade space for redesign:
- armor/battery geometry
- armor material
- battery layout
- other solutions (i.e. the afore-mentioned cow catcher)

The problem generally comes down to cost and as a startup whose products are already priced in the super car range; Tesla probably can't cover it if the redesign is major.  They just don't have deep pockets like the big three.

BTW – is it better for the cow catcher to throw the object and get it moving where it could conceivably go through someone's windshield?  Maybe skewering the battery can be a design feature?  Call it "Spontaneous marshmallow roast mode"

Watashi
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Re: Uncommon Trend?
Watashi   11/12/2013 3:57:59 PM
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That sounds like what the big car makers would do.  Maybe an extra skidplate would help or maybe not.  But either way it appears that you are doing something. ...and the issue gets kicked down the road so you can see if it is a trend.

On the other side, doing something also signals that the issue is real.  It will be interesting to see which path they take.

TJ McDermott
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Statistics
TJ McDermott   11/11/2013 4:40:07 PM
Publishing equal statistics about Tesla vehicles vs. ICE vehicles in general, fires per 10,000 vehicles would put this in good perspective.

NadineJ
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Re: Statistics
NadineJ   11/11/2013 4:45:22 PM
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Are there comparable situations from the past?  My understanding is that this may be unique to Tesla.  And, specifically unique to the Model S.

TJ McDermott
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Re: Statistics
TJ McDermott   11/11/2013 4:48:20 PM
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Another reader noted there are many car fires each year.

RogueMoon
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trend starting, but careful with conclusions
RogueMoon   11/12/2013 9:34:04 AM
TJ, its an interesting data point about annual automobile fires in the US, but you have to be careful with comparing small population datasets (Tesla S vehicles on the road) to large population datasets (all ICE vehicles in the US).  Trends in small sets tend to look larger than they actually are.  Two events in a month is the start of a trend but hardly worth sounding the alarm that a defective design exists.

The issue is not so much that the occurrence of road debris leading to punctures, but the consequence of this event being so extreme.  Given the low position of the batteries and the nature of high-energy density storage, the consequence is very hard to mitigate.  Best approach is to increase the puncture resistance which is likely what Tesla is doing right now.  Fewer trailer hitch balls in the road is another good plan for mitigating automobile damage.  My truck doesn't appreciate them much either?

LetoAtreidesII
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Re: trend starting, but careful with conclusions
LetoAtreidesII   11/12/2013 9:57:20 AM
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Yes but also lets not forget that statics say that younger drivers and older cars are far more likely to be in an accident the older drivers or higher price vechicles.  Common sense tells us this as well.


The 2 of these often go hand in hand.  I see very few teens or 24 and below driving a tesla, they just do not have the money yet.

As for age of a car.  as a cars ages their chances of a failure increase as well.  I had a truck a couple of years ago that the brake line rusted and I lost most of my braking power.  when you compare ICE vechile accidents and fire including old vechiles you greatly inflate the fire #'s

Charles Murray
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Re: trend starting, but careful with conclusions
Charles Murray   11/12/2013 1:31:59 PM
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Excellent points, LetAtreidesll. The best way to make the comparison is probably to compare to new cars to one another. Or possibly new luxury cars, which tend to be driven by people who take good care of their cars.

GTOlover
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Re: trend starting, but careful with conclusions
GTOlover   11/12/2013 4:04:00 PM
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Charles, seems this is turning into a hot topic!

I could not resist the pun:-)

Charles Murray
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Re: trend starting, but careful with conclusions
Charles Murray   11/13/2013 9:53:20 AM
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Hot, indeed, GTOlover. When Boeing had its battery incidents last winter, NTSB investigators estimated temperatures of over 500 degrees F inside the battery pack.

http://www.designnews.com/document.asp?doc_id=258717

naperlou
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Re: Statistics
naperlou   11/12/2013 10:56:51 AM
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Just publishing the numbers is not sufficient.  Many car fires are the result of poor maintenance or other non-design related issues.  They are also not nearly as intense.  Like with many statistical studies you need to control for other factors.  Comparing a new Tesla S with a 10 year old car is not valid, for example. 

The following is an illustration of what I am talking about. Many years ago my sister had a car burn.  It was a minor thing, a fuel hose leaking onto the manifold.  The placement of the components was standard for the industry at the time.  The problem was that the secondary latch on the hood had broken and my father had rigged something up.  My sister forgot about it and could not tell the fire fighters how to open the hood.  Thus a minor fire that should have been put out by the driver ended up causing major damage.  Two things are important to note here.  One is that even if she could have opened the hood, this would have been counted as a fire and compared to the Tesla S fires (just looking at fires per x miles).  Second, the whole situation took a while to unfold.  The aftermath did not result in pavement melting. 

Also, if you are going to talk miles driven, I submit that any mass market vehicle in the US has many times the miles driven in a Tesla.  Musk uses the number to make the whole thing seem miniscule.  Compare that to the number of unintended acceleration with the Toyota cars, or the earlier Audi situation.  This is a large number (3) for such a catastrphic situation in a motor vehicle. 

bdcst
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Re: Statistics - Just sweep it under the rug.
bdcst   11/12/2013 1:18:31 PM
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Just sweep it under the rug.  Or in this case under the chassis.

In some ways an extremely active lithium battery pack is more dangerous than a gas tank.   Deforming a gas tank will not normally result in a fire or exposion.  You have to breech its containment permitting a fuel leak and a spark to ignite the vapor.

Either the battery packs have to be re-designed to make them runaway proof even though that reduces the storage energy density (wider electrode spacing with more electrical and thermal insulation between cells and fusable links to electrically isolate cells), or they have to be protected within battery boxes built to withstand worst case impacts.

Unfortunately, the engineering compromises required to provide meaningful driving range for an all electric automobile result in sub-optimal safety.

Charles Murray
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Perspective
Charles Murray   11/11/2013 6:25:06 PM
The numbers given last month by Elon Musk, which are very believable, are as follows: There is approximately one vehicle fire for every 20 million miles driven in the U.S., according to the Department of Transportation, compared to one fire in every hundred million miles driven by a Tesla (that figure may have changed slightly over the past month). So, as of a month ago, Tesla was five times better in this area. So it's good to maintain perspective on this. This incident is NOT an indictment of Tesla or of electric cars. As we've said many times previously, it's also good to remember that gasoline-powered vehicles carry far more energy on board than EVs, and actually have more potential to wreak havoc. Having said that, though, previous incidents (especially the Boeing incidents) have raised public concerns about lithium-ion batteries. And if these incidents could be reduced by adding an extra eighth-of-an-inch (a 50% increase) to the armor plate on the bottom of the vehicle, would that be so bad?

NadineJ
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Re: Perspective
NadineJ   11/12/2013 12:57:21 AM
I just got an email from Tesla today.  It was customer testimonial about the safety of the Model S in a recent incident.  Another email from Musk is scheduled for tomorrow. 

They are quick to reply!  Other car companies can learn from that.

Critic
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Re: Perspective
Critic   11/12/2013 2:20:44 PM
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A gallon of gasoline has about 33 kWh of energy, so an average 15-gallon gas tank would contain about 500 kWh when full.  Comparing this to an 85 kWh battery in a Tesla, yes, a full gas tank contains much more energy.  However, this sort of analysis ignores the fact that the battery electrolyte is flammable.  The heat energy in the electrolyte is not included in the 85 kWh figure.  Even if the battery were completely discharged, there would still be heat energy stored in the flammable electrolyte.  How much energy is there in the battery if we include the flammability of the electrolyte?  I don't know, but the amount of energy doesn't really matter, anyway.  You don't need 15 gallons of gas to start a fire; a fraction of a gallon is enough.

I suspect that as Tesla cars age, there will be more fires, caused by poor maintenance or deterioration of the cars. 

It is important to consider the causes of car fires.  Some are caused by design flaws, some by accidental impacts, but many others are caused by arson or poor maintenance.  Poor maintenance could include a leaking fuel line or tank, oil leaks, accumulation of oil/grease, electrical shorts, or accumulations of leaves or other detritus.

It's too early to draw any conclusions from the data at hand, but so far, electric vehicles don't have quite the same capabilities as gas-powered cars.

Toaster
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Simple fix?
Toaster   11/12/2013 8:32:43 AM
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Sounds to me like a simple skidplate is in order. Could be made from Aluminum as in my Suburban. I have been driving for around 40 years, and the only (damaging) thing I ever hit was a piece of metal that punctured a plastic fuel tank in a Dodge. Skidplate solved that issue too.

fdiaconu
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Iron
Re: Simple fix
fdiaconu   11/12/2013 9:36:38 AM
Tesla designers may also consider a light plastic/fiber shield underneath the metal battery cage to absorb the impact ... something like a Kevlar bullet proof vest for the car.

dmorgan
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Tesla to blame?
dmorgan   11/12/2013 9:02:15 AM
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How many gazillion Ford Pinto's were still on the road after it was determined that in a rear crash, it would explode?Maybe the driver's need to watch where they're going. I travel quite a bit and see junk on the road. Amazingly, my crew cab Silverado 4x4 has been able to avoid almost all of it. Tesla can"t/shouldn"t be held accountable for every incident. Reminds me of Edison electrocuting elephants to "prove" the danger of AC voltage.

Battar
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Platinum
Road scrap
Battar   11/12/2013 9:04:28 AM
Seems to be the problem is not so much with the car as with all those bits of scrap metal the good citizens of the US leave scattered on the roadway. I wouldn't rate the chances of my Nissan Note coming through unscathed if I hit a lump of iron on the asphalt, either.

GTOlover
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Re: Road scrap
GTOlover   11/12/2013 9:42:19 AM
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Yes Battar, have you ever followed a dump truck or trailer full of scrap metal or construction trash? How about the yokles driving down the road with a matress strapped to the top of the minivan or worse compact car? I have even seen vehicles driving down the turnpike with the muffler dragging!

So to highlight the Tesla as an issue is missing the question of why is there a hitch in the road? And as others have mentioned, isn't the Tesla a great handling car? Could the driver not brake or maneuver around this (perhaps not)?

Tool_maker
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Re: Road scrap
Tool_maker   11/13/2013 12:47:57 PM
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@Battar: Trash on the road, while an example of carelessness on someone's part is nonetheless a part of road hazards all vehicles confront on a frequent basis. To design a vehicle incapable of handling them is irresponsible. Of course no engineer can foresee and protect against all hazards, but to have a high priced vehicle destroyed by a scrap of seems a bit ridiculous. How would this same vehicle handle buckeled pavement or a large pothole? Both of which I have encountered with a thud and shudder accompanied by a trip to a garage to have the front end realigned. I even hit a pothole, disguised as a puddle, big enough to flatten a tire and bottm out the frame, but there was no resulting fire.

Charles Murray
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Re: Road scrap
Charles Murray   11/15/2013 6:15:34 PM
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That's a good point, Tool_Maker. I have a feeling that Tesla is now considering the possibility of a stronger plate on the bottom of the car.

LetoAtreidesII
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Stats area funny thing
LetoAtreidesII   11/12/2013 9:50:32 AM
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First with any new design the safety standards and requirements always are lacking and often are driven by were failures occur when the rubber meets the road.

Ex. Jeep rollovers, Engines in the rear and front crash hazards, many many others.


This said the question is is :

1.with the existing Tesla design is the damage caused by road debris like this equivelent

2. Is their a way to mitigate the risk

on count #1 yes a stard ICE vechile going over the same pieces of metal would be far less damaged on average.  It would not be pretty and the car would be damaged but it would not meltdown.

on Count #2 yes, a stronger better protected battery would help reduce not eliminate these type of failures.

NiteOwl_OvO
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Gold
Model S = DC-10?
NiteOwl_OvO   11/12/2013 9:56:45 AM
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Didn't the DC-10 have a tendency to suck up anything not securely bolted down on the tarmac? Maybe in addition to a beefed up battery box and/or skid plate they could increase the ground clearance a bit. It doesn't really need to be able to drive over a sleeping policeman, but I would hope it would clear a trailer hitch laying on the road. I'm sure Tesla will come up with an effective solution. They have too much to lose if they don't.

listener
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HISTORY
listener   11/12/2013 10:40:07 AM
Tesla's response is really very similar to the way Detroit used to respond to problems, refuse to believe there is a problem and get positive publicity out.

May not be enough vehicles out there yet to create DOT type statistics but there have been enough failures to show that something different is going on and it needs to be fixed. By all acounts Tesla has some excellent characteristics but how they respond will determine whether they remain a viable force.

jordaj
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Iron
Tesla fires
jordaj   11/12/2013 11:09:05 AM
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Sounds a bit like the ill fated Concord when a piece of junk on the runway brought down the plane.

bobjengr
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TESLA BATTERY FIRE
bobjengr   11/12/2013 2:43:42 PM
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I drove the I-24 Interstate this past Sunday from Chattanooga to Nashville.  It's always amazing to me at the debris along this Interstate highway.  Most of the "garbage" is from recaps thrown by semi trailers.  These "road gators" can cause significant damage.  I was a passenger in a rental car, driving these same roads at night, and hit a recap.  The impact was great enough to wipe out the wiring harness supporting both headlights.  We were out of commission until Hertz could bring us a replacement.   I'm not to the point of saying this is a trend for Tesla but it obviously has created awareness on their part.  I suspect great thought is being given as to what actions should be taken by the company.  Neglecting the issues, which does not seem to be their reaction, will not suffice.   Excellent post Charles.

William K.
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Damaged by road-rubble
William K.   11/12/2013 7:55:08 PM
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It is unfortunate that these cars have been the ones to hit the junk on the roadway. I wonder if the drivers could have avoided the objects, or if they had time to avoid them. I once damaged a car to the point of having to replace it when the frame hit an object that I never even saw since it was covered with snow. It damaged both frame and the oil pan, and a bit of one connecting rod. So the Tesla is not alone in being damaged. The difference is that my car didn't catch fire, it just died.

Possibly some smart designer can start selling an armor plate to protect the battery from road-rubble wreckage. No need for Tesla to do it, let somebody else who is good at armor design create the solution. An armor plate air-dam to prevent objects from getting under the car where they can do damage. Bounce them sideways, not up. 

any1
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road debris
any1   11/13/2013 8:57:42 AM
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As I have driven in various parts of the country over the last few years it has become obvious to me that there is a lot more road debris than there used to be in general, but certain areas look like distaster zones.  I believe that due to budget cuts at the state and local level there is no longer anyone charged with cleaning up these roadways anymore. So the debris just collects.  I can vividly remember an interstate near Detroit where for miles at a time the side of the roadway was so cluttered with debris (mostly shredded truck tires) it would not have been safe to pull off into the shoulder in case of emergency.

AnandY
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Re : more research needed
AnandY   11/24/2013 12:18:48 PM
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Speaking for myself, I would definitely not get into a car that catches fire every month through no fault of my own, let alone drive the damn thing myself. A good designer foresees future obstacles and sets in place measures meant to counter the same. The accidents simply mean that the manufacturers of the Tesla Model S electric car have simply not done their homework well enough.

Charles Murray
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Re: Re : more research needed
Charles Murray   12/2/2013 6:23:29 PM
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I'll be curious to see NHTSA's take on this issue, AnandY.

Cabe Atwell
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Re: Re : more research needed
Cabe Atwell   1/20/2014 5:48:42 PM
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Apparently, Tesla has a new battery design in the works that has less of a chance of bursting into flames on impact. Until then drive slowly and on desolate roads with no oncoming traffic and you should be fine.

Cabe Atwell
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Re: Re : more research needed
Cabe Atwell   5/6/2014 9:59:22 PM
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It's interesting to note that the crash Concorde flight 4590 was also caused by road debris. When will they harden components that can withstand high-velocity impacts?

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