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Electronics & Test

Road Debris Causes Another Tesla Model S Battery Fire

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Watashi
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Platinum
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.

GTOlover
User Rank
Platinum
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
User Rank
Platinum
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
User Rank
Platinum
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 :)

bobjengr
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Platinum
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.

Critic
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Platinum
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.

Charles Murray
User Rank
Blogger
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.

bdcst
User Rank
Platinum
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.

jordaj
User Rank
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.

naperlou
User Rank
Blogger
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. 

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