Ugh. Another Model S fire - 2013-11-06

[dm33]

The thing is have there been any incidents where either car hit road debris? You need to know that before saying the shield is not strong enough. AFAIK the Volt uses plastic for its battery casing and the Leaf also has a flat pack that uses thin sheet metal and a plastic shield on the bottom (for sound proofing and aerodynamics).

The Volt's pack surface area is smaller, but it's still exposed:

Hard to imagine in 500 million miles that someone hasn't drive over debris. Point taken though. The Volt and LEAF battery packs do not seem to be particularly well protected. The LEAFs pack in particular is relatively large and across the bottom of the car. Still we're talking about 24kwh vs. up to 85kwh, so the Model S has a much bigger pack and bigger area.
Still something seems amiss.

 

[MilosK]

Doesn't seem to be an edit button to replace the end right bracket I accidentally chopped off above

 

[RoverS]

everybody be like "i hope my Model S doesn't catch on fire..."


maaan, i wish my Model S WOOOULD catch on fire!

 

[jthompson]

Vehicle fire trends and patterns

 

[Discoducky]

I think for any collision of steel (transmission part, tow hitch, etc.) vs aluminum underside, steel always wins.
Perhaps we'll need to add some more protection to the underside as the cars are pretty low to the ground.

Agreed and it might be less of an issue for Model X, but more for GenIII as it might sit lower and will travel many more miles. But at this point I'd be inclined to investigate afforded extra protection to the front and middle portion of the undercarriage due to recent field exposure or possibly offering a future option of raising the car to avoid road debris if detected by a sensor/system.

 

[logical_thinker]

So, I know you're joking about the cow catcher. But look at this pic of the underside--a V-shaped deflector that protruded a couple of inches down might actually help sweep crap to the side before it could hit the battery.

View attachment 34960

THAT is a great idea.

Elon Musk seems fairly open to constructive criticism (he's said so himself) and I think he might consider that idea.

 

[GDH]

everybody be like "i hope my Model S doesn't catch on fire..."


maaan, i wish my Model S WOOOULD catch on fire!

lmao

I call dibs on the burned and non burned rims, they'll buff out.

 

[MilosK]

I've been doing the math and Tesla has a problem on its hands. If you consider average age of the car, then Tesla is far more likely to catch fire than any ICE vehicle. Let me explain.

The average ICE vehicle is 11.4 years old (we'll just use 11). During those 11 years, the rate of fire is ~138,600/230,000,000 (controlling for intentional fire, etc.). That means risk of fire over the life of an ICE car is 0.0006. To get the risk per year, we have to divide by 11. We get 0.00005.

Now, do the same calculation for Tesla. The average care is 1 year old (actually younger, but this will favor Tesla to use 1 year). There have been 3 fires and there are about 12,500 Model S sedans out there. That means we have 3/12,500 = 0.00024. We divide by 1 to get the same answer back.

That means risk of fire is 0.0024/vehicle yr for Tesla and 0.00005/vehicle hr for an ICE. That means risk of fire is 4.8 fold higher for the Tesla. It gets worse though.

According to the NHTSA, risk of fire in an accident is about 2.9/1,000 accidents in an ICE. The rate of accident overall is about 2% of all vehicles on the road. If we do that calculation for Tesla, then there would have been 12,500 * 0.02 = 344 accidents so far. If we have 3 fires, then rate of fire per accident is 3/344 = 0.0087, which is 8.7/1,000. That is a three fold higher risk of fire per accident. For Tesla to be at the same rate of fires/accident, there would need to be ~1,000 accidents or roughly 8% of all Model S would need to be wrecked.

None of this bodes well for what was, until now, the "safest car in the world." Telsa needs to figure out what is going on and fix it IMMEDIATELY because this will not just kill the company, it will set EVs back decades.

I'm reposting this as my post got screwed up and theres no edit button on my safari webpage to correct it and its an important point:


Your logic is flawed (never mind your math: 12,500 x 0.02 =/ 344)- you're looking at a skewed population - a subset of all car owners who are Tesla owners. The NHTSB figures apply to the full class of all owners. It is highly likely that Tesla owners drive much more than average - or possibly less too. What you need to look at and compare is the accident and fire rates per mile driven of Teslas vs ICE cars - still not a perfect comparison as Tesla owners may drive faster or harder. (It could get really complicated as to could just compare fire rates for cars with a certain ground clearance etc. It all depends on what question you're asking.)


I don't have the exact figures in front of me but I seem to recall that based on number of miles driven after the first fire Elon said that ICE cars would have had FIVE fires by now. So with 3 fires we're still only about half the rate of ICE fires.

 

[stopcrazypp]

How can you say that neither of those cars have ever hit road debris before? Both the LEAF and Volt have probably ht plenty of road debris given the number of fleet miles each have put on, but that since the results were less than spectacular they simply have not made the news.

I'll add "reported" to that (either media or forums) and "metal" debris (enough to puncture or dent metal). There's been a couple of reported incidents of Model S hitting metal debris (I know of two not including these two).

 

[JeffChm]

Beginning to think this battery location could be a big problem for Tesla... 50k Volts sold, and 70k Leafs sold with no known fires, but 20k Tesla's on the road and 3 fires?

Road debris is hit all the time and I think it usually goes unreported. I hit some a few years back on the Long Island Express way and ripped a hole in the bottom my Porsche. Tow truck driver said it happens all the time.

That being said, the real issue could be the speed at which the Tesla driver is going when he hits the debris. My guess is Tesla drivers are moving a lot faster than a guy in a Leaf or a Volt. Makes it both harder to avoid the debris and causes more damage when you hit it. But either way, it is still a problem. While the car may be safer over-all, having a combustion issue that you don't have in an ICE is a big deal.

 

[Newscutter]

Here is a reference I used... Vehicle fire trends and patterns
.

Interesting tidbit from that same article: "Some form of mechanical failure or malfunction, such as leaks or breaks, backfires, or worn-out parts, contributed to 49% of the highway vehicle fires and 11% of the associated deaths. Electrical failures or malfunctions contributed to 23% of the highway vehicle fires but less than 1% of the associated deaths. Although collisions or overturns were factors in only 3% of the fires, 58% of the deaths resulted from these incidents. Older vehicles were more likely to have a fire caused by mechanical or electrical failures."

So basically incidents like we're seeing with the MS, do NOT cause rampant tiki torches on the highway nor do such incidents directly cause death to ICE drivers. OTOH, most ICE fires are caused by components that the MS simply doesn't have. These statistics are mixed bag in that regard. They suggest that MS fire incidences are unusually high even though accident-related but also that if the battery were better protected the MS would have dramatically lower fire risk overall.

Now I love the MS as much as anyone but coloring all ICE cars with the same crayon as a Ford Pinto is no more ridiculous than if the MS were to get the same characterization. That said, there clearly is a big difference between an ICE and the MS that I haven't seen anyone else mention: When an ICE suffers an underbody impact there are flammable liquids down there but at highway speeds they are quickly drained and separated from the vehicle. Disregarding the possibilities of cabin intrusion (or the gas tank itself, which is unlikely), the driver of an ICE in similar circumstances would realistically expect an immediate loss of engine power and a big mess all over the roadway, but not a fire. The MS, however, has all its energy -- though brilliantly stored and managed-- firmly attached to the vehicle itself. It can not be separated from that energy.

I think the remedy is probably 3-pronged:

1--Rethink of the air suspension lowering at speed-- or forward scanning radar of some kind to "pop" it back up to avoid such impacts (other manufacturers have this technology already and use it to enhance their own air suspension ride comfort).
2--Increase the impact deflection and containment properties of the battery shield.
3--Fire suppression foam/gel packets of some kind, perhaps embedding in the battery pack itself (there is already gel in there but it clearly could be improved upon).

As an alternative, these incidents have suddenly given the Model X and unexpected selling point. Ground clearance! Throw in a couple good rear seat cupholders and I think the Model X may be the perfect vehicle after all. 2015 is looking to be a good year!

 

[Todd Burch]

THAT is a great idea.

Elon Musk seems fairly open to constructive criticism (he's said so himself) and I think he might consider that idea.

Anything protruding down will reduce curb clearance. Fact of the matter is you really can't build downward at all below the current bottom surface of the car. Your options are:

-Increase reinforcement
-Relocate battery pack
-Raise suspension

 

[Gizmotoy]

Your logic is flawed (never mind your math: 12,500 x 0.02 =/ 344)- you're looking at a skewed population. I don't have the exact figures in front of me but I seem to recall that based on number of miles driven after the first fire Elon said that ICE cars would have had FIVE fires by now. So with 3 fires we're still only about half the rate of ICE fires.

We could say the same thing regarding your response. Note that Elon was comparing across all ICE cars. Were you to limit the comparison to ICE cars a year older or newer, I think you'd get a much different picture. That is to say, fires are more likely in older cars than new ones.

 

[stopcrazypp]

We could say the same thing regarding your response. Note that Elon was comparing across all ICE cars. Were you to limit the comparison to ICE cars a year older or newer, I think you'd get a much different picture. That is to say, fires are more likely in older cars than new ones.

Not necessarily. If you look at miles driven by new cars (much lower) vs fire incidents with new cars (also lower) and compared to miles driven by all cars (much higher) vs fire incidents with all cars (higher), it's not a given than the new cars will perform better.

And dividing by years old is flawed for the same reason, because you are assuming the probability of a fire scales linearly with age (which likely is not true).

 

[liuping]

I'll add "reported" to that (either media or forums) and "metal" debris (enough to puncture or dent metal). There's been a couple of reported incidents of Model S hitting metal debris (I know of two not including these two).

There is so much debris on the highways, cars are hitting in constantly. Why would you report it on the news (or even in a forum) unless it caused massive damage?

 

[BillHamp]

Objectively, in terms of crash ratings, I would agree that it is the safest car. However, it won't stay that way if it catches fire frequently. More to the point, however, is public perception. The car, and perhaps the industry, are going to get a bad reputation if Tesla doesn't do something. So far, most Model S buyers have been savvy people who understand stats, risk, etc. To really make a go of things, Tesla has to sell to a broader, less informed market.

 

[dm33]

Anything protruding down will reduce curb clearance. Fact of the matter is you really can't build downward at all below the current bottom surface of the car. Your options are:

-Increase reinforcement
-Relocate battery pack
-Raise suspension

Add
- reduce likelihood of a fire in the battery pack. Maybe additional fire retardant foam, more separation between cells. Different chemistry (scary).

Why do LEAFs and Volts survive similar collisions? Is there something inherent in the cell design? The LEAF doesn't have any thermal management system. There's no fire retardant foam at all. The cells are large format but stacked right next to each other with minimal spacing. Is it the chemistry?

 

[Dutchie]

I remember when the Concorde was brought down by debris on the runway, and the debris penetrated the fuel tank while the Concorde was taking off, the solution figured out was to protect the fuel tank with Kelvlar.
Kevlar is bulletproof and such a solution would add to the cost. Looking at the price of about $17 per meter (ihttp://www.alibaba.com/showroom/kevlar-price.html) it would cost less than $100 per car. I think that looking at the overall cost of a MS that is a doable solution.

 

[stopcrazypp]

There is so much debris on the highways, cars are hitting in constantly. Why would you report it on the news (or even in a forum) unless it caused massive damage?

If it were enough to dent or damage your undercarriage you would report it. And so far I know of two that happened to the Model S. Haven't heard of any for Leaf or Volt, but it's possible it had happened and just went unreported. But anyways, my point was it's not clear that the Model S shielding would fare any worse than shielding in other plugins under the same circumstances. The probability of a hit may be higher for other reasons (car is lower, speeds may tend to be higher, etc).

 

[Gizmotoy]

Not necessarily. If you look at miles driven by new cars (much lower) vs fire incidents with new cars (also lower) and compared to miles driven by all cars (much higher) vs fire incidents with new cars (higher), it's not a given than the new cars will perform better.

And dividing by years old is flawed for the same reason, because you are assuming the probability of a fire scales linearly with age (which likely is not true).

It's invalid because you're comparing a car with at most 1 year of data to an entire history of cars of all ages. The only valid comparison is going to be one that's limited to the same time period. I don't know what the results would show, but it's certainly disingenuous to broadly compare 20k brand new Model Ss to the auto population at large.

The only honest comparison I can think of would be to compare the rate of fires in cars produced within the last year. I strongly suspect that will not be in our favor.