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From a Model S owner in Tennessee (teslamotors.com)
355 points by bcn on Nov 9, 2013 | hide | past | web | favorite | 264 comments

I'm glad the driver is safe. However, I'm not sure what posting this letter is supposed to accomplish other than show that the driver is still a Tesla supporter. The remainder of the letter seems to be (potentially) counterproductive in that it describes that the car being on fire wasn't as dangerous as it sounds. Tesla isn't going to be able to tackle a perception problem by promoting safety features of the car when in flames.

It's supposed to show that the Tesla car is structurally sound and prevented the object on the road from ripping further into the car than it otherwise would have. It's also supposed to show that the car got the driver out of a dangerous situation by displaying warnings early. Finally, it is supposed to show that the car is resilient when bad things happen because it is still drivable.

I'm just explaining the viewpoint of the letter since you were unsure. I'm not opining that it is effective/ineffective or productive/counterproductive.

And what would happen if the person was rendered unconscious during an accident ?

I think the point is still valid that the safety features are nice but the core issue is that the car burst into flames during a seemingly minor accident.

Running over a trailer hitch at 70mph is a major accident. A smaller, lighter car could have been thrown off the road or rolled over, in addition to having the object puncture and invade the passenger compartment possibly causing injury, and loss of control. You're right in that it would be unlikely to cause a fire, though I wouldn't really worry about that if I was dead already.

"A smaller, lighter car could have been thrown off the road or rolled over, in addition to having the object puncture and invade the passenger compartment possibly causing injury, and loss of control."

...or maybe not. You're just speculating.

I've run over stuff at high speeds in other cars, and I"m here to tell you that they didn't flip over, puncture, or burst into flames. The most common outcome, in my experience, is that the oil pan or transmission pan gets dented, and starts to leak.

I ran over a metal object on the freeway that punctured the transmission which started pouring transmission fluid onto the exhaust pipe and ignited. The truck was on fire for a few minutes before I was alerted by another driver and pulled over.

Low probability events happen all the time, and I don't think we can draw any solid conclusions from these anecdotes (other than driving any vehicle is potentially dangerous).

> Low probability events happen all the time

Hah! I love how extremely counter-intuitive and completely true this sentence is at the same time.

Cars do burst into flames though. There are around 194,000 vehicle fires on US roads each year from around 250,000,000 registered vehicles, which gives around 1 fire for every 1,300 vehicles. There are so far 3 Tesla fires from around 16,000 Tesla cars on US roads, which gives around 1 fire for every 5,300 of them, so they are doing better than the average. 3 fires though is still far too few to consider this a particularly useful statistic.

In order to determine how well the Tesla S handled these collisions, the stats you cited are useless. We should not count fires caused by types of accidents Telsas have never been involved in. Also, no one is accusing Tesla cars of bursting into flame for no reason, so the cars that are not in accidents aren't important either.

To really understand where the Tesla ranks in safety, we would need a detailed analysis of: the accident, how non-Tesla cars handled similar accidents, how the Tesla is designed to handle such an accident.

I do agree that we have no where near enough data to draw general conclusions about the safety of the Teslas, so I think it's inappropriate to say, "they are doing better[or worse] than the average."

A detailed analysis of "the accident" is precisely how we don't find out how Tesla "ranks in safety".

Once the numbers of cars become large enough we can simply look at the outcome numbers, to determine how likely that outcome is. It doesn't matter if a car is "designed to handle such an accident". What matters is if it does handle a given kind of accident.

A Tesla car is unlikely to ever be involved in a fire at a gasoline station. We probably shouldn't give combustion vehicles a free pass there.

As more and more Tesla cars hit the road, confidence level increases in the stats that are derived. Early data is not meaningless; it can be indicative of later results.

I agree with the rest of the post, and this part might be true of this thread: "Also, no one is accusing Tesla cars of bursting into flame for no reason, so the cars that are not in accidents aren't important either." but not necessarily among the general public.

I think this is precisely the idea they are combating. The initial news reports didn't have any details and just said there was Tesla on fire on the side of the highway.

Correct this a bit and you find 3 per ~100 million miles driven on public highways. that is about ~3x worse than a regular car. 100 million miles is enough data points to be meaningful, but not exhaustive. Also, given these cars are new, the state-space of defects is likely less populated tha for the average car. Historical data show age as a factor in fires, and new cars are less likely than average-age cars to catch fire.

I was surprised that the letter did not go into these types of details. Cars (electric or not) catch on fire. There are statistics on this. The truth about the Model S's safety has not changed. Tesla seems like a more 'sticking to their guns' kind of company rather than a adjusting tactics to handle this situation.

The underside of a Tesla is quite a bit more sturdy than your oil or transmission pans. A piece of debris able to do this would do something far more serious than cause a dent or leak.

The principle difference is that the entire underside of a Tesla is vulnerable (to a first approximation), while a conventional vehicle has a few zones of particular sensitivity (fuel tank, oil pan, gas line, possibly drivetrain).

I'm fairly impressed with Tesla's record so far, but mounting a half ton (literally) of energy storage to the entire underside does raise some interesting questions.

Your anecdotes are not data.

Once I had a rock the size of a golf ball smack into my windshield on the highway. It hit with such force that it made a noise that almost sounded like a gunshot, it was quite startling. It didn't leave even the smallest mark on the windshield though. Another time a tiny pebble the size of a pea hit my windshield and made a very sizeable chip in it.

Anecodtes involve luck (good and bad), the purpose of statistical analysis is to gather enough data so that the luck, which should be random, is filtered out from the "signal".

"I've run over stuff at high speeds in other cars, and I"m here to tell you that they didn't flip over, puncture, or burst into flames...."

It really depends on what kind stuff the car runs over and how fast the car is moving, and also how well the driver is handling the situation when it happens. I've almost run over ladders and mattresses, but never trailer hitch. Maybe I'm lucky.

No it isn't. I've driven over a large rock cast off from an RV going 80mph in a little (2000lbs) sportscar made in the 1960's. There was a large bump, grinding sound and damage to the underfloor (you could poke your finger through).

But in no way was it a major accident.

Please read my separate post about a very similar accident a decade ago that killed 6 children. I don't think anyone can make blanket statements about what is and isn't a serious accident.

A minor accident? Are you sure about that? Running over a trailer hitch at 70 miles an hour is no minor accident. It could be so munch uglier. The car could flips over, tires pop and loss control. In fact, the car continued to operate normally for another minute and stopped safely is quite amazing in that situation in my opinion.

In this case the driver stated that the cabin was undamaged. He was able to remove his papers from the glove box. Smoke inhalation may have been dangerous, but in this case the fire didn't seem to a safety issue to the driver if he had been able to leave the vehicle.

I guess, it would happen the same thing that happened to the papers and pen at the gloves compartment.

This isn't a good argument seeing as how papers and pens can't die from asphyxiation.

I don't see how that is a minor accident. He said he felt the car fly up into the air.

A major accident for me is one in which cars drive oncoming to a semi trailer, hit a power pole at very high speed or multi car pileups. Something where no matter what type of car it is there is likely to be mass casualties and media coverage.

Driving over something at highway cruising speed doesn't seem all that major to me.

Driving over something at highway cruising speed doesn't seem all that major to me.

It's major enough that, as other commenters have noted, it would rip apart the undercarriage of any smaller car, and possibly enter the cabin through the floor.

This is wholly speculative. Floor pans are typically flexible steel. They are not puncture prone. As they are capable of deformatin (absorbs energy). The TSLA has 6mm armor plate, which is stiff and while strong is not tough. It is thus probably not good at disapating energy, so it takes the full brunt. You don't build a bumper out of 6mm armour plate. That being said, maybe TSLA just needs a V-hull to dissipate the force (by deflection, rather than absorbtion). That's how they made the military humvee more impact (blast) resistant, while keeping its armour in tact.

>maybe TSLA just needs a V-hull to dissipate the force (by deflection, rather than absorbtion).

Vhulls are only useful for upwards blasts...short of IEDs showing up in California the concept is useless for a sportcar. Also...humvee doesn't have a vhull - prototypes aside. You're likely thinking of either the MRAP or some buffalo derivative.

Obviously not a "deep v" shape nor something blast resistant, perhaps but some form of deflective geometry might be helpful under the car. It does seem the force ultimately is going ^up^ as opposed to >in< . . .

It might help in a couple of fringe cases like debris hits. You'd murder the aerodynamics though.

Pretty much every other area will suffer too - handling, aesthetics, fuel efficiency, manufacturing complexity, battery replacement etc.

Its just a horrible trade-off.

It would absolutely rip the undercarriage of a small or large car.

But so what ? It would never start a fire.

Never say never. Those things are random. It 100% depends where the object hits. Being the Tesla or any other car. There IS a fuel line. There ARE electronic wires. in any car. And all going underneath the car.

I've personally seen more than 1 regular gasoline car catch fire for various reasons.


Similar kind of accident happened in India, only difference is the passengers there did not get enough time as escape from fires. Here is the link http://www.thehindu.com/news/cities/Hyderabad/45-killed-as-b...

Not real that similar....that bus took out a guardrail.

My point is fire spreads fast and time to escape or no warning signs in other vehicles, where as Tesla has it designed well.

Yes, my petrol engine wakes me up with coffee whenever I'm unconscious.

They should make a C.O.R.A. plugin for the Tesla S onboard electronics. Heck, they should make a K.I.T.T.!

There was a more detailed account floating around. Essentially, each battery cell is in its own fire-resistant compartment. The fire crew that responded to the call used procedures that are standard for other electric cars, but are not proper for a Tesla. Essentially, they "punched through" these compartments in an attempt to extinguish the fire, which actually exacerbated the problem by allowing the fire to spread to other battery cells.

When the fire department arrived, they observed standard procedure, which was to gain access to the source of the fire by puncturing holes in the top of the battery's protective metal plate and applying water. For the Model S lithium-ion battery, it was correct to apply water (vs. dry chemical extinguisher), but not to puncture the metal firewall, as the newly created holes allowed the flames to then vent upwards into the front trunk section of the Model S. Nonetheless, a combination of water followed by dry chemical extinguisher quickly brought the fire to an end.


I saw a Nissan in fire a month or so ago outside of Philly. Car fires happen regardless of engine technology.

It seems putting the onus on every fire department to learn new tesla procedures may be the wrong approach.

Why do you say that? The fire department is a service hired by us to extinguish our stuff. Didn't they learn how to put out gasoline engine car fires 100 years ago? They should have refused because they only knew how to put out horse fires?

In those 100 years, we've learned a thing or two. Which is why we have fire codes and whatnot. We reduce the variation in the number of expected scenarios.

I'll also note that in general, it is easier to learn something different when it's not similar to what you already know. Horse fire vs car fire is easy. Car type A vs car type B vs car type C is more difficult.

Don't joke, horse fires are a very real problem.

Tesla is actually _really_ good at distributing training materials to emergency responders. All vehicle manufacturers do it some some extent, but Tesla sets a very high bar.

As an example, check out this training video they put together: http://www.youtube.com/watch?v=ntK3rvVl2Qw (skip to 26:45 for the fun part ;)

This video in particular is about extrication, not firefighting, but you get the idea...

We train frequently to deal with the new challenges presented by electric vehicles.

Holy hell, that thing cuts through the car's pillar as if it were made of paper!

apparently 2 of 3 fire departments did it wrong, so...

And the 3rd one was in Mexico . . . hmmm

Fire departments had to get special training for the Prius (and other hybrid cars) because of the power cabling going from the rear battery to the front. It's not that unusual.

I think you have it wrong way round - all other electric cars should have batteries split into fireproof compartments

I've never seen a car fire until last week, when I passed by this: http://i.imgur.com/k0xylRe.png. I was really surprised at how large the fire was (it looked worse in person)

Same problem in the WA fire. You cannot extinguish a LiIon fire without (it seems) cutting the car open. In Wa, they put out the fire and it restarted. They had to flip it over and cut holes in it (presumably, through the floor)

see > https://news.ycombinator.com/item?id=6498232

The thing to remember with a battery fire is that it's not enough to just put out the flaming electrolyte, when the battery is shorted out you don't just lose all that energy, it gets converted into heat which is what ignites the electrolyte. The battery in a Model S is made up of 11 modules so when one of these modules is shorted you don't have the entire capacity of the battery being turned into heat but depending on if an entire module was shorted out or maybe two adjoining modules that's still a lot of energy and once the whole thing starts burning you might compromise the other batteries in the system.

Tesla engineered firewalls in between the battery modules but it's not like it's fireproof forever, it just means the heat has to transfer through conduction and gives the driver additional time before the vehicle goes up or before the fire department gets there. What might be a good improvement is a 2.5 inch fire hydrant fitting under the back of the car that the fire department could connect to to flood the battery compartment with water and just hook the car up to a hydrant for 30 minutes to make sure the fire stays out.

> Car fires happen regardless of engine technology.

Of course. But nobody has statistics about the rate of fires per accident type.

And remember that this isn't necessarily a reflection on the engine technology but more so the design of the car. Given that accidents often result in debris and also that people drive over stupid things maybe batteries shouldn't be under the cabin floor.


Its pretty rare for car fires to happen on public highways. Most car fires are incidents with a vehicle at rest, or deliberately set. Something like 2% of accidents involve petrol based fuels systems. Many more are cuased by other issues.

Telsla (as an example) previously recalled ~40% of its Roadster models in 2010 for fire-hazard related faulty wiring. That kind of thing would be attributable to any type of car.

The high incidence of Model S LiIon fires in the field, is much more problematic and worrisome, IMHO. Like you say, it may just be a design flaw on the location of the battery pack. Aft of the front axle is a debri-zone, wheras aft of the rear axle would be more protected from debris (but subject to crumple zone impacts compromizing the integrity of the pack directly or through shrapnel)

The problem with tesla is the active suspension dropping you to a couple inches off the road on the highway. Debris that you would normally pass over shoots into the under carraige..

This is a really helpful and pertinent insight IMO.

A few solutions:

Turn off dynamic highway suspension feature

Use RADAR to detect debris and cause suspension to lift to avoid as much damage (could cause vehicle instability)

>To avoid instability, slowly lift suspension, slow down lift towards apex, lift front suspension first and then rear suspension, and/or slow the vehicle slightly before raising suspension. (Could use rear-facing RADAR to inform decision process about slowing down.)

Of course, with more automation and sensors, the car could possibly change lanes autonomously to avoid road debris all together. (and message the highway patrol and other automated or semi-automated vehicles of the location of the debris as warning)

One last solution I can think of is to somehow either strengthen the undercarriage or add deflectors or crumple zones of some kind.

Personally, I'm thinking that better accident avoidance automation will be the most reliable...including raising the clearance. And making the batteries more puncture-resistant would be great.

On a tangent, would it reduce the likelihood of combustion of the batteries if each compartment could recognize a puncture event and quit drawing power from the batteries in that compartment?

I'm waiting for the day that fully autonomous vehicles are legal and affordable. In the meantime, semi-automous vehicles that "... message the highway patrol and other automated or semi-automated vehicles of the location of the debris as warning ..." is an awesome use of a sub-set of the autonomous technology, and a great way to demonstrate such vehicles' capabilities!

Perhaps they could use a radar scanner at the front to look for oversized objects, and react by pumping the suspension up to maximum height?

Would probably cause instability and loss of traction (at apex) right before a defensive swerve.

By apex I presume you're saying that as the suspension finishes lifting the car, the act of effectively "throwing" the car up into the air will momentarily lower the apparent sprung weight. Makes sense.

If the suspension can act very suddenly, it could execute only when collision is unavoidably imminent.

Does anyone know what the size of this hitch was? What I'm picturing isn't all that large.

mercedes has something sorta similar... it adjust the suspension to adjust for pot holes.

But nobody has statistics about the rate of fires per accident type.

What planet are you on?



Tesla has no engine. Oh, don't follow a truck. http://www.teslamotors.com/models/features#/safety

The reason this was posted by Tesla is so that they control the message. The mainstream media would love to take an incident like this and completely turn in it around to make a news story out of it. But because Tesla has already written about the incident, it makes trying to spin it in a negative light much harder, as Tesla will not need to take a defensive position.

if you crash a regular car and it catches fire do you feel its unsafe? in this case whatever the driver hit must have been pretty big and went through the aluminum (the bottom of the tesla is without any doubt much stronger than a regular car due to the battery compartment). It's likely to have caused a fuel leak and electric fire in any other car as well, except the car wouldn't tell you that and everything would have burnt (if you have never seen a car fire, firemen can't stop the fire from consuming the car once the fire reaches the fuel tank)

the point is that the car knew it was damaged and self diagnosed properly, and that electric circuits are all properly isolated and monitored. Pretty cool if you ask me.

It's not unusual. Many car ads show a crash test.

Trying to get in on some of that TSLA action, eh?

Amusing how positive stories about tesla take the top spot on HN while news of the fire was quickly flagged off the front page.

Not to question what was said here, but:

> Had I not been in a Tesla, that object could have punched through the floor and caused me serious harm.

How is that the case? There are cars that are higher off the ground than a Tesla (where it wouldn't have a chance to punch through the floor) and most cars have material in the undercarriage to protect against small blows like this ...

I've been in an old Subaru Justy whose floor pan had been rusting for years, and it wouldn't have stopped squat coming through and hitting the driver. Once, the car's owner was driving us to a music contest, and we started to hear some scraping. He pulled over and pulled a piece of metal off the bottom of the car, and we kept driving.

That's never going to happen with a Tesla S. (Read that both in a good and bad way.)

How old is the Justy though ... compared to a newer model Subaru? I love my Subaru Impreza ... and it is built solid...

In 1992, that Justy was already old. Incidentally, that friend bought that car for $250 his sophomore year. When he graduated, he sold it for $250.

> old Subaru Justy whose floor pan had been rusting for years

Now, if Tesla S floor pans never rust, then I'd agree with your conclusion.

It's not just that. There's very little metal besides aluminum, and it's quite a bit thicker than the steel floorpan. I would expect the battery cases to be much less vulnerable to corrosion than sheet steel.

Aluminium corrodes quite nicely in salty environs.

Pretty much everything does. The question is how fast. When steel rusts, it manages to increase the surface area available to more chemical reactions, which is why rust spreads like a cancer. I don't think aluminum does this.

Under normal conditions, aluminum oxide forms a protective layer for the rest of the aluminum. This goes out the window for unusual sorts of corrosion (say, mercury).

Really? Someone should really tell the manufacturers of boats then.

They know this; that's why zinc sacrificial anodes are used. See: http://en.wikipedia.org/wiki/Cathodic_protection

If your boat is only aluminium you don't really need the anode. it is only when in contact with other metals that aluminium has serious problems in sea water, as it becomes the sacrificial anode to your steel or brass, so you need zinc then as it has an even lower potential.

I think we need to try to define small blows if that's what you're going to call this. They hit a trailer hitch, fast, and it pierced 1/4 inch of steel armor. In a car with similar clearance and without such armor it seems there's a very real chance it could have penetrated the driver or passenger compartments. I don't think that's a small blow.

Are .02% of all car drivers injured every year by road debris which punctures the cabin from the underside of the car? Because that's the percentage of Tesla drivers who claim the design of the car saved them from this very thing.

According to the well-referenced http://en.wikipedia.org/wiki/Road_debris :

> In 2004, a AAA Foundation for Traffic Safety study revealed that vehicle-related road debris caused 25,000 accidents—and nearly 100 deaths—each year.[1][7] At highway speeds, even small debris can be deadly.

With the small sample size so far, we could chalk it up to a statistical anomaly (repeated "unlucky" events do happen, and are expected with natural random sampling), or an actual engineering problem.

My bet is low clearance. It would be interesting to compare these accidents against all cars with similar bottom clearance.

In that case, it's just a physical dimension problem combined with a bit of a poor consequence of battery damage...

Flagged off the front page? The day news of the 3rd fire broke there were two stories that made it to the front page and between them both covered pretty much the entire working day.

This was noted two days ago: https://news.ycombinator.com/item?id=6692051

This is a general trend though: Tesla's overreach regarding the NHTSA rating was on the front page for more than a day, whereas NHTSA's statement regarding Tesla's misinterpretation was not even on the front page for a few hours.

Also>Yesterday (21 points, flagged < 1 hr)


And before that... (26 points, flagged < 1hr)


Last press release: (567 points, #1 front page)


That seems to be more the result of the overzealous flame-war detector rather than the effect of flagging. Only PG can truly tell, though.

The flamewar detector brings the story down if it has a lot of comments, and if not paired with lot of upvotes, takes it quickly off the front page. So, while you're right about the HN bias(lack of upvotes), you're wrong about the reason(flamewar detector rather than flagging).

It also tends to happen to Gruber articles, articles positive or neutral about Microsoft, and anti-Samsung or anti-Google articles.

Here's a couple of examples.


HEADLINE: Tesla Fire Sets off Flamewar.

MOUNTAIN VIEW, CA. HN headquarters was forced to shut down earlier today when a Tesla Model S (discussion) spontaneously caught fire. Responding the the event, the mountain view polic chief was on the scene within minutes. According to source, PG tried to put out the fire using water (in line with TSLA protocol), but the stubborn flames kept re-igniting. Finally, he had to revert to "flipping the server over" and drilling a hole in the bottom to finally douse the flames. No injuries were reported in the incident, and PG will be writing an essay later this week on the subejct. Extolling the cirtues of the Flamewar detector, as well as the excellent design of the electronically powered server at the heart of the matter.

We're reading this on Tesla's site, and they obviously wouldn't have posted it if it weren't at least somewhat flattering, so we have that lens to view it through.

But, the letter does raise the important idea that before we decry how awful the failure mode is ("the car caught on fire!"), it's worth considering what the alternative would be---what happens in similar situations in combustion engines?

> We're reading this on Tesla's site, and they obviously wouldn't have posted it if it weren't at least somewhat flattering, so we have that lens to view it through.

In this case, we've seen reports from the driver in 2 of the 3 accidents, so it's hard to make a case for selection bias. Though feel free to argue it further if you know details of the crash in Mexico that I'm not aware of.

Driving a car is one of the least safe things we do regularly, FWIW. With the population large enough, we are virtually guaranteed to see more of these.

Unfortunately, the media does terrible things to our risk perception by giving us incomplete evidence and leaving us to extrapolate. For example, to compare whether the Tesla is unsafe--and for all we know, maybe there is some flaw that helps road debris catch on the plate and puncture it--it would be more informative to see fires/#miles driven for a large cross-section of common cars, as well as fatalities/#miles driven and the like. Of course, even that is somewhat biased, because there might be effects where, hypothetically, risky drivers are drawn certain cars or something like that.

Nothing. Conventional cars are designed not to catch fire when they run over road debris, especially not cars built within the last two decades. At worst, debris may cause a flat if it punctures one of the tires.

>At worst, debris may cause a flat if it punctures one of the tires.

That's dismissive hyperbole. Debris regularly causes serious damages to all vehicle types. If the object in question, as in this case, is hard enough and hit with enough force to penetrate the battery, it's hard enough and hit with enough force to seriously damage any system it hits. It may not crack the engine block, but it can destroy radiators/suspension/brakes/fuel tanks/etc. The worst case scenario is most certainly not "a flat".

>At worst, debris may cause a flat if it punctures one of the tires.

That's just not true. I had about $2k in damage on a Mini Cooper (2006, stock) that hit the remnants of a blown out semi truck tire in the road. Similar situation to the blog post -- a pickup truck cleared it but I did not. I was not in a safe position to swerve.

The tire chewed up the lower front bumper and punctured the radiator. I had to immediately pull over and have the car towed. It happened to hit below the foam & all the fancy crash reinforcement on the bumper. Good times.

That was just 70lbs of steel-wrapped rubber. I can easily imagine a trailer hitch as described taking out a radiator or oil pan on a modern car. Unlikely to cause a fire for sure, but it'll certainly disable a vehicle.


"In 2004, a AAA Foundation for Traffic Safety study revealed that vehicle-related road debris caused 25,000 accidents—and nearly 100 deaths—each year."

The term "road debris" can mean anything from dust to entire engine blocks[1]. The debris in question here is a metal tow hitch.


See my other comment upthread for an example of a gasoline car catching fire because of cardboard boxes.

Normal vehicles don't have their fuel tank along the whole bottom of the car, let alone that far to the front. All that is for a reason.

Tesla made a choice to arrange packs like this for swap purposes. It certainly wasn't going all out for safety. Throw in the fact battery tech really isn't all there yet and you get a very large battery that compromises have to be made.

Tesla chose a compromise based on their swap tech. They could have put more batteries in the rear or made the stack shorter. Used a central tunnel for more, etc.

>Tesla made a choice to arrange packs like this for swap purposes.

That might have contributed, but I think lowering the center of gravity was the main consideration.

A normal car would not tell you there was a problem and suggest corrective action, then demand you pull over when safety parameters were exceeded, keeping you safe and healthy with minutes to spare.

The first you would know there was a problem in a normal car, would be when you felt or saw the fire.

ummh... you really think Tesla's PR team didn't write that and ask the guy to sign it? implying how nicely they were going to treat him if he did? Sure, it's quite possible as a fanboy he did it totally on his own. But I wouldn't bet that way, and I have to think most people who know how the tech industry works would feel the same.

I'm guessing most Tesla owners at this point are rich, well-educated and level-headed people who are also early adopters and a fan of the car and company. It seems reasonably likely that it's genuine.

I find it unlikely that Tesla PR would attribute their cars' safety to a supernatural being.

ha, good point.

not sure if it adds to the overall credibility.

bottom line, the guy likes the car enough to write/cooperate, even after it hit a bump and burned up, how much of that is the car's greatness, rose-colored fanboi glasses, good old-fashioned working the media...unclear.

When was the last time you saw a car accident on the news where the car burst into flames ?

Maybe it's just a case that combustion engine based cars have had more time to resolve this issue properly.

>>When was the last time you saw a car accident on the news where the car burst into flames ?

Last month, right here in Seattle: http://www.king5.com/traffic/news/Collision-causes-car-fire-...

Local traffic reporters (in Atlanta at least) have been known to call cars catching on fire 'Car-B-Qs'. It's a distasteful name but indicates that cars catching on fire isn't that uncommon.

it's worth considering what the alternative would be---what happens in similar situations in combustion engines?

What happens then? There are several innuendos throughout this thread that allude to some sort of catastrophic scenario if it were a normal vehicle, however this seems unsupported.

Yes, normal combustion engines catch on fire, but they don't explode in a fireball when they hit debris on the highway (there is absolutely nothing rare about hitting debris on the highway).

Further there are millions of combustion engine vehicles on the roadway -- there are currently some 250 million traditional vehicles in the United States. Last I read Tesla is delivering something in the range of 30,000 vehicles per year.

> Yes, normal combustion engines catch on fire, but they don't explode in a fireball when they hit debris on the highway

To be fair, none of the debris I've ever seen or hit on the highway would have made holes in a quarter inch steel plate, and I have driven the better part of 25k miles/year commute over some very busy highways for approximately the past decade, so I've seen such random debris as chairs & couches in the middle of the road in addition to the usual assorted vehicle parts.

There is also a car fire roughly every 3 minutes, just to keep things in perspective.

I say that as we are guaranteed to see more fires given enough time. With them averaging out to one every 3.x minutes, it's only a matter of time before we go through this again.

> There is also a car fire roughly every 3 minutes, just to keep things in perspective.

Are you joking ? How does that keep anything in perspective ?

There are over 1b cars in the world and 50k Teslas. That's 0.005% of the total car population.

> How does that keep anything in perspective ?

The Tesla has been available for 140 days, as of the time I'm posting this and using the June 22nd release date[1]. So my back-of-the-napkin estimates say there have been about 63,000 car fires in that time so that 0.005% of the car population is responsible for 0.000048% of the car fires in the past 140 days, which does not seem disproportionate. There are other, even better ways to compare the risk for which I do not have data available. Feel free to research your own numbers and compare.

[1] http://www.teslamotors.com/model-s-has-arrived

But remember we are talking about an expensive, new car with a lot of modern safety features. Which is the complete opposite of most of the cars you see around the world. My point was that comparing Tesla's record with existing cars will never make sense since we simply don't have all of the facts.

It seems obvious though that Tesla being a very different design will have different incident characteristics.

June 22, 2012.

Oops. That makes things even more ridiculous, if there have been 3 battery incidents in all this time. Put 505 days into my calculation instead of 140...

As to the point about them all being new cars, well, new cars are safer. If safety is what we're after then yes, a modern car is a good thing. If you're saying that the safety will decay as they age, well, that's reasonable but only time will allow us to correct our calculations there.

That might mean that we need more time to make a full determinations, but that's not a bad thing. This tells us about their current safety which is what's relevant now.

That leaves approximately 227,250 fires since the Tesla has been introduced, of which Teslas are known to be responsible for three. Or 0.000013% of all car fires in the relevant time.

That said, the other test might be more relevant, as there were more actual Teslas on the road in the past 140 days, rather than at day zero of launch. I don't have the figures to calculate, say, fires/#miles driven.

I'd point out that those innuendos are based on manipulative statistics: the standard is comparing the rate of car fires, but most of those 250 million cars are far older than Tesla Model S (decades as opposed to months old). A proper apples-to-apples comparison would look at new cars (within a year, lets say) and compare those rates.

Simple calculations show that the Teslas are roughly 25x more likely to catch fire in a collision, but I suspect they are much less likely to catch fire for other reasons. So just don't hit anything.

What's the error rate on that? I don't think we've seen enough Teslas involved in major accidents to even begin to determine how likely they are to catch fire compared to other cars.

You don't need to know the accident rate--you just need to know the rates of fire from an accident per car-year driven. Tesla doesn't have a long history here, but they do have 10K cars on the road.

I know nothing about the physics of it but would that not depend on the causes of fires? I may be misunderstanding but it sounds like you're implying that fires are more likely in older cars - maybe that is actually the case (I'd be willing to believe it).

A huge number of vehicle fires are electrical in nature.

I've been a firefighter for ~10 years. Nearly every vehicle fire I've seen falls into one of three categories:

1) Deliberately set 2) Faulty/old/corroded wiring (by far the most common) 3) Some flammable material coming into contact with something really hot (commonly after an accident where a car has gone off the road into tall dry grass)

Fires due to the fuel tank failing are _extremely_ rare (I've never seen one, or even heard of one in neighboring areas).

It may be related to the fact that I'm in an area that uses lots of nasty stuff to deice roads, but corrosion is a major issue with vehicle electric system, and the older a vehicle is, the more likely it is to experience a 'spontaneous' fire.

Another important effect is that some cars have known defects putting them at increased risk of fire, and some of those cars are still on the road, which inflates the statistics for the average automobile.

The Tesla didn't explode in a fireball, it vented the heat to the front, away from the battery pack and the cabin, and then the front caught fire.

I am not implying that it did explode in a fireball. We see the evidence several times now that it was a controlled, escapable loss of property, which is an ideal worst-case. I was replying to the "what could have happened if" innuendo about combustion engines.

Exactly. The tesla cars are just too delicate. You definitely can't have one without warranty. And I say this as an Elon Musk admirer.

The same is true for other cars in its class, such as a Mercedes S-class, or a BMW 7-series.

> Yes, normal combustion engines catch on fire, but they don't explode in a fireball when they hit debris on the highway

And neither did this one, so I'm not sure what your point is.

there are currently some 250 million traditional vehicles in the United States

And 194,000 vehicle fires.

>Yes, normal combustion engines catch on fire, but they don't explode in a fireball when they hit debris on the highway (there is absolutely nothing rare about hitting debris on the highway).

That is not true. Here's a case of a car catching fire after being hit by cardboard boxes.


The Tesla in the story was hit by a tow hitch looks like this. http://1.bp.blogspot.com/-A22JVrgZjqY/TzKFRNPUN1I/AAAAAAAADh...

I find it very surprising that you think it's common for cars to run over things like that on the road and keep going. I or the people I know have never driven over something like that.

From Wikipedia:

>Road debris is a hazard[5] that can cause fishtailing and damage like a flat tire or even a traffic accident with injury[6] or death. Road debris can cause loss of control crashes, rollover crashes, or penetration of the passenger compartment by the debris.[1][7]

>Released in early 2013, NHTSA data for 2011 showed over 800 Americans were killed that year in vehicle collisions with road debris. Mississippi, Wyoming, Arkansas, Kentucky and Louisiana were the top five states for these crash deaths to most likely occur. Also in 2011, New York and Massachusetts saw significant increases in road debris-vehicular crash deaths, unlike other big, populated states.[8] In 2004, a AAA Foundation for Traffic Safety study revealed that vehicle-related road debris caused 25,000 accidents—and nearly 100 deaths—each year


That news story of the conventional car catching fire after an encounter with road debris is the perfect comparison. It happens, and the same outcome often happens as well.

This is not surprising. It's a little surprising that we've seen so many stories of Teslas hitting road debris, but my hunch is that the problem is caused not by being electric, but by a low bottom clearance designed for drag efficiency, battery space, and low center of gravity.

A gasoline car with such low clearance would encounter similar problems, as they surely do every single day. This is completely normal. The way it affects an electric battery is kinda crappy, but it's not necessarily worse than debris hitting a tank of flammable fuel, just different. A tesla would have gone right over cardboard, for example, and been unharmed, while it might get stuck in the underbody of an ICE car and catch on fire.

Different technology, different problems, but the sample size is still too low to make real conclusions. One thing we do know is that there have been no deaths in a Tesla vehicle yet; that can hardly be said for traditional cars.

A gasoline car with low clearance would NOT have the same problems.

The fuel tank is located higher up near the rear axle. Not alongside the bottom of the car as in a Tesla.

Yes this has been standard design for a good while now. The fuel tank is typically above the rear axle and between the rear seat and the trunk. I don't think there's been a car with the fuel tank right over the road and right behind the rear bumper since the 1970's. The Pinto in particular taught us that was a bad design.

The rear fuel tank low down behind the rear axle is still in some currently produced cars, I'm afraid. http://www.autosafetyexpert.com/defect_fueltank.php

Note: either the battery didn't catch fire in the said tesla (see picture), either the battery is extremely well isolated and the fire exhaust point was in the front of the car.

Note2: how do you think the fuel goes from the fuel tank <REAR> to the <FRONT> motor.

Thats how: http://i.stack.imgur.com/87oFf.png

Oh, theres a tube in there between the REAR fuel tank and the FRONT engine. Damn, didn't break laws of physics.

> That is not true. Here's a case of a car catching fire after being hit by cardboard boxes. > http://www.ksl.com/?sid=25850334

To be fair, that was more of case of a cardboard box catching on fire after being hit by a car...

Probably more likely the cardboard box is dragged under the car a few seconds, heat up and catch on fire.

That is not true. Here's a case of a car catching fire after being hit by cardboard boxes.

Are you seriously saying that the car exploded into a fireball? Because of course it didn't, and in fact the combustion was primarily the incendiary material of the cardboard box, just as it would ignite near high power electric motors. That has zero relevance to this story.

I find it very surprising that you think it's common for cars to run over things like that on the road and keep going.

You entirely misinterpreted my post. I stated, nor implied, absolutely no such thing.

I love Teslas. If I had the disposable money (and the need of a fulltime car) I'd buy a Model S without hesitation. I think Elon Musk is a brilliant entrepreneur.

But this is tripe. I can smell PR and sanitized wordsmithing when I see it--and this post reeks. If that wasn't obvious by the medium of this post--The Official Tesla Blog.

Gee, how did it get up there? Do you think that maybe, just maybe, at some point in time the author was in contact with Tesla's PR department? And do you think Tesla PR decided to let someone post something with no oversight whatsoever? And this post just happened to be perfectly on message with the talking points Tesla PR had drafted up?

For all we know, every word of this is true, but in this format (a very defensive post on the Tesla Blog giving a 100% pro-Tesla version of the events), Tesla has no credibility. Why not have this person write about this in the user forums and then link to it from the official blog with a foreword from Elon?

Do you really think it would be wise for Tesla to not control the message here?

That's not evil, it's just smart.

No, not at all evil, if they don't control the message who else will? (HN commenters not withstanding)

I'm just saying the way they are going about it insults my intelligence.

I'm a big Tesla fan. I'd like to buy one. I like that they're changing our dependency upon gasoline vehicles. I like that they're taking big chances. Having said that, I find their communication style at times to be very disappointing. I hate the weird inference of "Thank God I was in my Tesla and only caught on fire. It would have been much worse in another car" Why do they have to do that? What proof do they have? They've had 3 car fires in the last 5 weeks out of 19,000 units on the road. Stop trying to turn a negative into some sort of positive. We get it's new technology. There probably will be things that need straightened out. The way they positioned their lease was cheesy. This is now cheesy II. Just say

"We take this VERY seriously. We don't think there is any structural issues here but we will continue to investigate. Rest assured if the data points to any possible issues we'll be fully transparent and make any adjustments necessary to ensure the safety of our customers." Not some hack rah rah piece on their blog.

That would suggest some kind of long term, expensive development and testing slog with investors footing the bill. This letter suggests Telsa is nothing but success and investors get a piece of the pie.

I wonder, if Tesla were to harden the protective shield of the battery pack and issue a recall for the existing vehicles, they could just deploy the new battery packs through the automatic battery swapping facilities in the supercharging stations.

The costs would probably be much lower than normal car recalls, and it would also be an interesting value proposition for the owners: "zero downtime, you get for free a safer car and a fresh battery".

Anyway, the more I hear about Model S the more it looks like an exceptional engineering feat.

He hit something at freeway speeds that lifted his car into the air yet continued driving, even after he was alerted the collision had caused significant damage to his car?

So I currently live in Tennessee near where the incident took place (the vehicle owner is a relatively well-known spinal surgeon in Nashville) and I can tell you that the interstates in this part of the country are relatively desolate and do not present an attractive option for pulling over. Outside of the cities, there are miles between exits and the area is heavily wooded with little amenities nearby. After having driven on I-24 for a time, I can relate with the author when he states "I just wanted to make it home". If his car seemed "driveable" at the time, I too would've chalked it up to bad luck and tried to survey the damage at home rather than getting stranded on a interstate shoulder. Just a hypothesis offering some context for the basis of his decisions.

"Car needs service" does not mean "pull over immediately". Pulling over on the side of a freeway isn't the safest thing to do, especially if you're told your car may not restart. Once the car told him to pull over, he did, safely.

If your car says that when you're starting it at your home then it may not be something to be concerned about but if that message pops up immediately after you hit something at highway speeds, you should take that as an indication something is definitely wrong and pull over.

I had a similar innocuous sounding message popup in my car (not Tesla) right after there was significant damage to the tires/rims and suspension due to some large debris on the road. I pulled over immediately but the car's "Car needs service"/"Tire pressure low" messages were ironically amusing when I got out and saw the extent of the damage (completely flat tires, broken rims, etc).

TLDR: Cars don't have "This car will explode/catch fire" messages. "Needs service" message can mean something really bad.

There is a middle ground between stopping immediately on the freeway and continuing home at your previous speed.

There is lots of damage that may not immediately be obvious. For example if the debris struck his tyres he could suffer a blowout that could cause him to lose control.

Running over a piece of debris so large that it feels like it lifted the car absolutely means "pull over immediately". He had no idea what structural damage occurred to the car, and continuing as is put not only himself but other drivers on the roadway in danger.

There is negligible danger pulling over on the freeway. I can only imagine that he didn't want the inconvenience, which is remarkably selfish.

That aspect of the story read very poorly.

> There is negligible danger pulling over on the freeway.

Is this really true? I don't know of any evidence either way, but it's not hard to find articles warning against it. Here's one randomly selected from a google search: http://www.allenandallen.com/blog/the-shoulder-of-the-highwa...

Since I have no hard evidence either way, I have to go with my gut, which says that pulling over on a freeway shoulder is dangerous and should only be done as a last resort. But I would welcome evidence to the contrary.

Pull over and do what, exactly? Be a road hazard? Call a mechanic to come look at the car?? Stop blaming the victim, that's not what we're here for.

I find your reply simply incredible given that in this case the driver not only didn't pull over on a significant impact event, they stayed in the left lane, then causing a huge road hazard as their car burst into flames, forcing them to pull off the left shoulder of the highway (again, the most dangerous place to be). To bizarrely question my advice seems rather foolhardy given the situation that we know.

Condescending blather about what we're "here for" is not what we're here for given that we're discussing the details of this event.


There is negligible danger pulling over on the freeway

Unless you've driven the section of freeway in question, I don't see how you can so confidently say that.

Yeah that's the curious part of the article.

Why did he not pull over immediately? Especially if you own an expensive car, I'd want to know immediately if it was damaged... if it was raised off the ground by an object.

Did his continued driving contribute to causing the fire to start? Rather than stopping immediately.

Quote from the article... "Car needs service. Car may not restart." I continued to drive, hoping to get home.

He also stated that after he had hit the object, he still had full control of the car so he didn't feel like he was in any dangerous or had the need to pull over. Quote below.

"While driving after I hit the object until I pulled over, the car performed perfectly, and it was a totally controlled situation."

I'm wondering what insurance will say. I wonder if the fire would have occurred if he had immediately pulled over.

Would you rather get home and deal with your fucked up car there, or deal with it on the side of the high way? It makes perfect sense why you would try to keep driving it if you were close to your destination.

I mentioned this in another thread about this incident. I was driving a mid 80's Volvo 850 in the early 2000's, and while turning around, I managed to run over a wheel stop and impale my car's oil pan on a piece of rebar sticking out from the top of the wheel stop. From what I remember, the oil pan on that particular year of Volvo station wagon was made out of aluminum of about the same thickness as the battery casing.

If an aluminum wall vessel like that is going to encounter a pointy piece of steel with all of the car's momentum behind it, the steel is going through! No getting around it. No designing around it. It's just physics.

There was no fire, but this resulted in all of the oil leaving my car's engine. All of the oil. No fire, but it created a situation where I could have wrecked the car and needed to pull over and stop the engine immediately, which I did only because I spotted the trail of oil in the rear view mirror. I never got a warning. In contrast, the Tesla told the driver something was up. IMO, the Tesla system was in better control of its incident and provided clearer and better information.

The Tesla Model S may have provided clearer information, but presumably all that would've happened if you hadn't stopped would be that your car would've been a total write-off. In the case of the Tesla Model S this was actually the best case scenario, and they're portraying the fact that this was only a spectacularly fiery total write-off and no-one was injured as a victory.

fiery total write-off and no-one was injured as a victory.

Works for me!

This does make me wonder if the shape of the Tesla's underbody (very flat [1]) is such that debris is more likely to make a direct rather than glancing impact. Perhaps Tesla should take a leaf out medieval armor design and add more contour to the bottom of their car so that it can shed impacts more successfully.

[1] http://media.ed.edmunds-media.com/non-make/fe/fe_9171228_600...

It was designed flat for aerodynamics, just like how the door handls retract into the body.

This reminds me of an accident in Illinois a decade ago, in which a couple lost all six of their children after running over a mud flap bracket that had fallen off of a semi.

The circumstances sound very much like the case described in the link -- the large piece of debris pierced the gas tank and generated sparks, igniting the vehicle in a matter of seconds.

(link at http://articles.chicagotribune.com/1994-11-10/news/941110023...)

Who knows exactly how an ICE vehicle would have performed in the current circumstance, or how a Tesla would have performed in the Illinois accident, but it's fair to say that a collision at speed with a large piece of road debris can easily destroy a car and prove fatal to the occupants.

> Had I not been in a Tesla, that object could have punched through the floor and caused me serious harm.

Clever misdirection.

Are you sure? The Model S has a quarter-inch thick armor baseplate, which is way more than a similar combustion engine vechicle undercarriage.

> Are you sure?

Of the clever misdirection? After reading the rest of your comment, you should be too. The issue under discussion isn't the safety of the passenger versus road debris, it's the vehicle catching fire after colliding with road debris.

This is a clever mechanism to turn discussion to the armor plating under the vehicle; as both replies to me evidence, it worked.

This is a fair point, and, to be honest, I don't have any idea of whether a standard car may catch fire in a similar circumstance.

Had you been clear from the get go, you might not have been downvoted like you are now.

That being said, even if standard cars wouldn't catch fire, it is not necessarily aggravating for Tesla. The technology is different, and the kind of risk being run differs. This doesn't mean that Tesla cars are inherently safer or more dangerous (we'll need more data to determine this).

>The issue under discussion isn't the safety of the passenger versus road debris, it's the vehicle catching fire after colliding with road debris.

Says who? You? The issue under discussion is the safety of a Tesla versus other cars in similar circumstances. If I was evaluating the relative safety of cars while purchasing a car, a fire after a few minutes of striking a big piece of debris seems to be safer than major damage or loss of control(if that's the case).

Whether an equivalent non-Tesla car would actually be more dangerous is certainly up for debate, but I don't see anything insightful in your post. We can already see the domain name even before clicking on the article and we know this is Tesla publishing the letter so it's likely to be one sided. In fact, the current top comment on HN points it out.

Your comments shouting "PR! misdirection!" add nothing to the discussion. Are you arguing that a non-Tesla car would not catch fire in similar circumstances? Can you share your reasoning?

Is that truly armor?

I can't find what the base plate is made of, but I would be very surprised if it was "armor" as used in military vehicles.

I would guess shielding or impact protection are better, more objective terms to describe it. And yes, it will probably be stronger than in a gasoline car because of the fire risk.

Just because it's not military grade doesn't mean its not "truly armor"; How would you explain armor worn by humans? Is that not armor just because it's not used in military vehicles?

I don't think that is a strong argument. You wouldn't call a car fast/strong/large/etc if it was fast/strong/large/etc relative to a soldier or a ship fast/strong/large/etc if it was fast/strong/large/etc relative to an armored vehicle.

I agree you wouldn't call a car fast/strong/large/etc.. if it was fast/strong/large/etc to soldier and etc... But, you're comparing apples with oranges now.

"Is that truly armor? I can't find what the base plate is made of, but I would be very surprised if it was "armor" as used in military vehicles."

What is "truly armor"? It sounded as if you were saying something could only be called armor if it is X,Y, or Z. But, armor can be pretty much anything given its definition is a protective covering, but there are different strengths of armor. I'm saying a diamond is still a diamond regardless of its grade. Similarly, armor is still armor regardless of its strength.

The batteries are located under the car, and their base plate is more armored than your usual car undercarriage.

edit: floor, floor -> base plate, undercarriage. Thanks grinich for improving my vocabulary.

And you telling me that reminds me that the misdirection works.

If you need a throw away account, maybe that's a sign you just shouldn't say anything?

Right. I shouldn't disagree with the status quo. That's a sign of a healthy community.

I made the throwaway to make a point to a friend of mine regarding HN voting in Tesla threads. It's working, right down to the prediction that I'd be called a troll within 30 minutes.

I'd argue HN is no longer a healthy community. At least, not as healthy as it used to be. Silly stunts like throwaway accounts and being overly concerned with reputation are one reason why.

For what it's worth I have my doubts about the article as well. If the driver didn't have enough time to avoid the object but the truck in front of him did, then it's probably because he was tailgating.

Regardless, please stand behind your words with a real account. It's the right thing to do. It will also help maintain the integrity of the community here. Which sounds like something you're concerned about.

I would be surprised if a truck had so little ground clearance that it would get caught up on a trailer hitch. The lowest part of a truck should generally be the rear differential, which gives a worst-case-scenario ground clearance of just under half the tire size. If the hitch wasn't centered in the middle of the truck, the ground clearance would be almost exactly half the size of the tires. Depending on the truck this could reasonably be a ground clearance of between 18" to 24", more than enough to clear a hitch without needing to swerve. Compare that to what, 5" clearance in the Tesla?

Swerving in a truck would also generally be much more dangerous than just hitting something.

For what it's worth I have my doubts about the article as well. If the driver didn't have enough time to avoid the object but the truck in front of him did, then it's probably because he was tailgating.

At highway speeds, all you need is a second of hesitation to erase a four car-length buffer. It probably takes over a half second to identify the object and determine it's too large to safely drive over.

>>It's working, right down to the prediction that I'd be called a troll within 30 minutes

Making the same argument multiple times in a thread turns this into a bit of a self-fulfilling prophecy.

People will probably keep downvoting you until you explain your comment a little more.

I don't understand your point. What is misleading?

Misdirection is distracting from the issue at hand by pointing to something else. It's a magician's trick. If you can't see the driver mentioning that he felt the vehicle saved his life by not letting the tow hitch penetrate the cabin, and the very deliberate placement of that observation written in a blog post published by Tesla in response to the vehicle catching fire after a common collision scenario, then I don't know what else to say.

We crossed ways. See my reply in the other thread.


The other discussions about comparing and contrasting the energy densities and relative safeties of fuel versus high-density batteries are interesting and relevant to safety considerations.

The car, at this early stage of its evolution, handling the situation as elegantly as it did is just amazing.

However the various safety-related tradeoffs play out, it's obvious that the Model S is seriously and well engineered at every level.

I imagine the good folks in Palo Alto are already folding updates into the system. "Shit's on fire, yo! Pull over."

I don't understand how this is supposed to bolster Tesla's image.

The fact that the car alerted him to the fact that it was going to combust does not mean that it is OK that the car combusted.

This seems to me to be a preemptive announcement.

Two fires are a PR problem, not an actual problem. But Tesla has a failure mode with their car that they need to address. It would appear that their "quarter inch armor plate" isn't thick enough to withstand a trailer hitch.

That's like saying the fire alarm waking you up at the middle of the night allowing you to safely escape does not mean it is OK that there is a fire burning your house down.

It is a true statement, but the situation is definitely preferable to having no notification.

Your analogy only holds if the fire alarm somehow started the fire.

Which is highly possible if it is collided with a same object same speed.

Is this the sort of thing that the guy ran over?


Yes, that was my impression. If he hit one like the one I have for pulling a large travel trailer, it is a bit larger than the one in your picture, and probably weighs about 25 lb. I wouldn't expect many cars to hit that thing without taking some potentially serious damage. example: http://imgur.com/8Fa0CVf

Seriously. A car being damaged by hitting that should surprise no one and there should be no controversy or debate.

Debris sometimes hits cars. It's not good for them. End of story.

The vast majority of cars on the road would still be drive-able after striking something like that (though many of them would miss it entirely dues to increased ground clearance). Even the vehicle in the blog post was drive-able, until it burst into flames...

Striking road debris is _incredibly_ unlikely to cause a fire in a 'normal' vehicle. The placement and design of the fuel tank makes a puncture incredibly unlikely in the first place, and even in the event of a puncture, the most common outcome (by a wide margin) is that you run out of gas... There are obviously exceptions to this, but it's rare enough than it's a big deal (recall worthy) when a vehicle design lends itself to this sort of event.

I am thankful to God that I was totally uninjured in any way from this impact. Had I not been in a Tesla, that object could have punched through the floor and caused me serious harm.

Oh really now, isn't this laying it on just a tad thick? How often does this happen? There's junk like this on the road all the time - how often are drivers and passengers actually shish-kabobed by any of it?

Tesla's damage-control, image-wise, is surely the envy of industry everywhere, though.

Just wondering, how does the ground clearance in a Tesla S compare to other cars?

Ground clearance on the Model S is 6 inches according to Tesla[0] which puts it at par with a Honda Civic Sedan.

[0] http://www.teslamotors.com/sites/default/files/images/models...

5 inches, because you need to account for the air suspension option that lowers the car at highway speeds.


I've always thought they look really low on the road, but apparently the data suggests otherwise:


I'm not sure, but I suspect the ground clearance isn't the major factor at play. I believe there are legal limits, such that cars must have at least a certain amount of clearance. So I'd be surprised if the Tesla S had a significantly lower clearance than other vehicles.

Just an anecdote, I've known one guy who had a chunk of old exhaust pipe come up through the floor of his vehicle, almost injuring him. It was a pickup truck with high clearance.

Why isn't the ground clearance the major factor ?

The batteries were damaged because an item went through the bottom of the car.

I meant it's not a major factor in assessing damage rates relative to other vehicle models, because the clearance is very similar, model-to-model.

Water? On an electrical fire? Caused by Lithium-based chemistry? Not smart?

Tesla's make up less than 0.008% of the US passenger car fleet. Perhaps emergency workers are simply not aware of how to properly deal with electric vehicle accidents? Formula 1 had to deal with this as KERS starter to be introduced. I would be nowhere near a 375 Volt DC battery pack playing with water.

Elon previously indicated that it was ok to use water:

"For the Model S lithium-ion battery, it was correct to apply water (vs. dry chemical extinguisher)..."


Well, good for him. I'd like to see him stand in a pool of dirty water in contact with a 400V DC power system trying to remove someone who might be hurt from the car. If you've ever seen what things look like around a serious car crash you know what I am talking about.

Here, pick one and let's "use large amounts of water" as the emergency response manual recommends.


If the water is flooding the battery compartment and basically shorting between every positive and negative terminal of every cell simultaneously inside the armored battery compartment, I very much doubt this puts someone walking near the car at risk of themselves becoming a short circuit.

Please think a little about the geometry of the situation.

EDIT: Okay, physics challenged people out there: electricity tries to take the shortest route of least resistance. Please use reasoning more sophisticated than: "Water! Electricity! Oh Noes!"

Please think a little bit about (a) not being condescending and (b) that the scenario you painted is ONE in a range of scenarios for a 400 VDC system with enough energy to propel a 4,000 pound vehicle a few hundred miles. I am not going to get into hypotheticals. All I am saying is that elecric cars have inherent dangers not found in gasoline cars. You can stand in a puddle of gasoline and you'll be OK.

Please think a little bit about (a) not being condescending

Please think about physics and use specifics in your reasoning. If you have better logic in your head, please relate it. What you have posted is indistinguishable from spin doctoring and therefore receives appropriate treatment.

I am not going to get into hypotheticals.

Because they'd sound pretty stupid if you came out with specifics. Remember, the context here is dealing with batteries encased in 1/4" thick aluminum armor. Scenarios that can expose dangers in the wreckage for one type of vehicle would also be dangerous for the other type.

All I am saying is that elecric cars have inherent dangers not found in gasoline cars.

Gasoline cars have inherent dangers not found in electric vehicles. See how hazy statements like that are?

You can stand in a puddle of gasoline and you'll be OK.

And you'd be much more foolish for doing that than standing in a puddle of water near a Tesla S whose battery compartments have been breached, but are mostly intact and are being inundated by fire fighters.

EDIT: "Water, electricity! Oh noes!" was directed at my downvoters, not you.

> Please think about physics and use specifics in your reasoning.

What do you imagine I was thinking about? Underwater basket-weaving? Please look at my profile on HN. I think I get it, and not just from a college course on physics theory.

Specifics? You are asking for hypothetical scenarios. Severe crash damage is random. It cannot be predicted. Not to a deterministic degree at least. We recently had a horrific crash in our neighborhood. An 18 year old decided it would be OK to drive his car at 100 miles per hour down an avenue.

He lost control at a turn and plowed into a bunch of cars on the side of the road. We heard the impact from over two blocks away and went to investigate. He destroyed FIVE cars. His car and an SUV were mangled into a ball of twisted metal to such an extent that it was hard to tell the two cars apart. He was severely injured. Nearly died. It took them OVER TWO HOURS to get him out. They had to cut the two cars apart from each other and used a crane to separate them. They they had to cut his car to pieces just to get him out. When his car crashed into the SUV the resulting ball of metal demolished another four cars. They were all mangled to an unbelievable degree, a couple of them on top of each other.

There was lots of gasoline everywhere. His tank and the SUV's ruptured. No fire. The firemen sprayed a foam and water over areas and just kept everyone away. There were probably a dozen rescue workers and two ambulances working on this ball of metal to get this kid out.

Now. Stop for a moment. Don't be defensive about Tesla. Think about that wreck. Try to picture what I described in your mind. Picture at least two cars mangled into a ball to such an extent that you have trouble telling them apart. Picture one or more people in there who are in desperate need for help. Now replace the gas-powered cars with electrics with fully charged 85 kW battery packs. Think about powerful super-hot fires. Think about a variety of conduction paths. Think about more than the battery packs but also about the high voltage cables going from the battery packs under the car to the motor controller and motor. Think about any number of potential random arrangements and damage scenarios for these components. Think about a hefty high voltage and high current cable from the battery pack to the motor controller becoming severed and making contact with the body metal. I ask you to think in terms of a severely damaged system, not a battery pack full of water. Now think about the people in there and the rescue workers trying to get to them.

Surely somewhere in there there has to be something that might cause you to take pause and realize there are issues with electrics that we have not yet experienced because electrics are truly rare in a population of over 250 million gasoline vehicles.

This idea that gasoline powered cars are more dangerous is a huge fallacy that is being used to try and protect the reputation of electrics. I get it. I get what they are trying to --and have to- do. That's far from the truth though. If you really want to compare electrics to gasoline vehicles look at the entire history of gas powered vehicles from the 1800's until today. You have over 200 years of history on various designs. The number of gasoline powered cars in the world today easily exceeds a BILLION units. Sorry partner, I have to say that gasoline, as much as you and I hate it --and I do-- is pretty damn safe stuff. The data on Tesla's causing fires due to collisions isn't statistically significant yet. If you were to do the math with this imperfect data today you'd find that Tesla's are six times more likely to catch fire in a collision when compared to gasoline cars. Again, this is based on insufficient data, so it's nonsense. Don't waste any time on it at this point.

I am rooting for Tesla. I truly am. My comments about electric car safety are more about the general issues with electrics rather than Tesla specifically. For all I know Tesla's designs are the safest around. Without detailed engineering data this is pretty difficult to evaluate. I'll take their word. I think it is a cool company.

My concern is that the entire electric "dream" could easily be damaged if we have one or two horrific electrocution or high energy fire incidents. I've purposely blown up LiPo batteries in order to learn more about their failure modes (we use them for our RC planes and helicopters). They produce explosive high energy fires. I don't even want to imagine what a large pack could do.

This, to me, is THE area that requires the most intense work in electrics. Forget range. Forget increased capacity. Safety is the number one consideration. Imagine, if you will, if we had the technology to make electric cars with packs that could take you a thousand miles. Maybe that's a couple of hundred thousand kW. How do you deal with these things in serious accidents? You can't discharge them quickly enough. The fires could be unimaginably hot and violent with electrical systems capable of delivering hundreds of volts and probably thousands of amps in an instant. This is dangerous stuff. Combine such a vehicle colliding with a gasoline powered vehicle and, well, now things are even scarier.

All that is needed for the electric car industry to suffer a serious setback is for an event to occur that would plant fear in the minds of buyers. I don't care how much of a proponent of electrics anyone might be. If a mother is in fear of her kids being electrocuted or burned to death in a horrible way you lost that buyer forever. No amount of reason or statistics is going to fix that problem. That's the scenario I am concerned about. Tesla and the entire electrics industry could be destroyed overnight if something horrible happened. Panic is a powerful force. That's the plain truth.

No disrespect. I am not trying to diminish you. I am simply not sure you've thought this through. If you are coming to this conversation from a perspective of having taken a usual dose of physics courses in high-school and college and without a reasonably amount of experience with high-power/high-voltage systems I will respectfully suggest you might not be equipped to fully grasp the gravity of the situation. Again, this is not a personal attack. I am just stating facts. I am not a doctor and would not be equipped to fully grasp a range of medical issues. That's just a fact.

Yes, understanding the theory is important. However, as the saying goes, in theory, theory and practice are the same, in practice, they are not. I've dealt with a wide range of high voltage and high power systems throughout my engineering career. High voltage is dangerous. Very dangerous. Period. I could not imagine any reasonably experienced electrical engineer not agreeing with me on this one. You don't want to be anywhere near an uncontrolled system with several hundred volts and lots of available energy, much less be in it, wet and injured. Not fear-mongering. This is as real as it gets.

Try to picture what I described in your mind. Picture at least two cars mangled into a ball to such an extent that you have trouble telling them apart. Picture one or more people in there who are in desperate need for help.

This situation is going to suck, no matter what. It's also a sure bet that this sort of situation sucked worse while it was still relatively new and experience was being gained by emergency responders and procedures were being worked out.

This, to me, is THE area that requires the most intense work in electrics. Forget range. Forget increased capacity. Safety is the number one consideration.

You make a lot of good points, and you do seem to have the background to know what you are talking about. It would seem that what's needed is a way to reliably disconnect every cell from every other cell, lowering the voltage to around 4 volts. If one can do this in response to the high g from a collision, this would go a long way towards making these things safer.

> It would seem that what's needed is a way to reliably disconnect every cell from every other cell, lowering the voltage to around 4 volts.

Yes, absolutely. Something along those lines will probably be essential as we move forward. Maybe not to 4 Volts. That's probably not necessary. Somewhere in the range of 20 to 50 V there's a good safe spot. I am not up to speed on where safety levels lie for different circumstances. I's more about current through your body than absolute voltages. Of course, a higher voltage makes producing high currents that much easier.

High voltage and current circuits are not the easiest to interrupt mechanically. They tend to make such things as mechanical contacts explode with molten metal flying all over the place. The arcs produced when trying to mechanically interrupt high current circuits can be massively destructive. That's why most high power mechanical contactors are very large, loud and fast. More here:


Not an easy problem to solve. Yet, it probably is solvable. Which is excellent.

See my other response. Great, until you have a crash that looks like these [0] and you have a bunch of people trying to help victims while walking around in a wet 400 Volt DC environment.

Now add more electric cars into the mix for a fun multi-electric car accident. Would YOU walk into that on Elon's recommendation? I'll tell you, I've been around high DC voltages, from a few hundred volts to tens of thousands. Water while handling components? No fucking way.

Don't get me wrong. I love electric cars and would have been in line to buy a Tesla SUV had they not pulled that bone-headed design stunt with the falcon wings. At the same time I am a realist in that I understand that there's much to be learned about having thousands of cars with fully charged multi-hundred-volt power systems sharing the road at the same time. The emergency manual says that the pack can easily re-ignite and that it should be under observation for at least 24 hours. That's one of the issues with electrics. You can secure a gasoline powered car by simply draining all of the gasoline and dealing with it chemically. Imagine an electric car catching fire again as it is being towed away on top of a flatbed truck. We are going to have to develop new approaches to all of this. Tesla, I would think, will be at the forefront.

So, not diminishing them, just stating reality.

[0] http://www.google.com/search?q=serious+car+crash&safe=off&cl...

What do you expect to happen? To the extent that the battery is compromised, the water is mostly going to make it short to itself, and it isn't as if a raging battery fire is going to be a better situation for the apparently trapped occupant (the only time the immediate car environment is particularly troublesome).

(The linked manual specifies using water to cool the battery and discusses observation procedures to limit the risk of re-ignition...)

> What do you expect to happen?

At one extreme, nothing. At the other, a potentially horrible electrocution. Run a google image search for something like "serious car accident" and insert an equally mangled battery pack in there. I very much doubt Tesla or any other electric car manufacturer would even remotely consider issuing a blanket guarantee stating that their design is electrocution-proof under all conditions.

Not trying to be a troll. Simply saying that high voltage systems are extremely dangerous. That's it. No need to agree with me. Just remember I said it.

It would be nuts if the interconnects have higher survivability than the firewalls. Mangling the battery will almost certainly significantly reduce the voltage (I didn't quickly find anything on the Model S, but for the Roadster, the output voltage is achieved with a final series arrangement of sub-assemblies, breaking that should directly reduce voltage).

Of course it will still create dangerous situations and experience will be valuable in judging just how dangerous.

How about some emergency equipment electric power dischargers? You could discharge huge amounts of energy in the form of steam. Just include a collapsible nozzle to direct the steam into the sky. Maybe this could be built into fire trucks?

When a battery might have been damaged, it's dangerous to discharge it, so I never see this becoming a standard procedure for handling EV crashes.

A solution that might be more practical: individual Li-Ion cells are only 3.7-4.2V, so it might be possible to split the battery in smaller low-tens-of-volts sections which disconnect from each other in case of a crash.

But now I'm wondering if it's feasible to quickly discharge such a large battery pack so let's assume for a moment that the battery pack is undamaged.

Batteries have a limited discharge rate, imposed mostly by their internal resistance and thermal limits. There seems to be some tradeoff between energy density and power density, so I expect the batteries in electric vehicles to only be designed and rated for discharging at peak motor power. Looking at the Model S, motor power seems to be 310 kW and the smallest battery pack stores 60 kWh, so it might be possible to discharge this pack in around 12 minutes. In fact, I suspect this battery is only rated for discharging at the peak rate for a limited amount of time (maybe just for a few seconds), but let's ignore this for a moment.

Add the time required to set up, and even with this naive estimation it seems impractical.

If this energy is used to boil water, a back of the envelope calculation shows that you'd need to completely boil off at least around 80 litres in order to discharge a fully charged 60 kWh battery. Now, I have no idea how a device capable of boiling off 80 litres of water in 12 minutes would look like, but it might be a bit challenging to fit on a fire truck.

80 liters is only around 20 gallons. A fire truck would certainly have that amount on hand. If you heat an element enough, water that hits it will flash to steam. I think you could make a heating element robust enough to accomplish this but still light enough to fit on a truck. Now, the wisdom of suddenly producing 2700 cubic feet of superheated steam in a residential area -- maybe it's a bit too cumbersome and potentially dangerous to be worth it.

A number of years ago I had to fix a fairly sophisticated 5 VDC 200 W switch mode power supply. Due to the design the only way to work on it was to have the supply fully loaded. We had to make a rig with a bunch of large wound power resistors in parallel submerged in a bucket of ice water. It was really surprising to see how quickly the ice melted and the water warmed up.

Large quantities of water are the recommended way to mitigate battery fires in EVs. The primary reasoning that you want to cool the cells to stop the thermal runaway process.

The worst case scenario is that the flood of water directly shorts the battery (which has likely already happened, if it's on fire).

My first car was an early 80's Jeep Grand Cherokee that had been 'modified' by a previous owner. Whoever it was had ripped off anything that might have been EPA mandated, and had then pounded bolts into the vacant holes left in the exhaust manifold. It took months for my father, grandfather, and I to figure out where all the vacuum hoses should go, in order to get it to pass inspection. Even after extensive repairs, well beyond I've described here, the thing would bleed quart after quart of oil as it went down the road.

It still did alright for a while, but eventually caught on fire. It happened spontaneously and without warning, while driving home in the snow. No impacts or anything, the thing just overheated and went up in flames.

The reporting on these Tesla events make the vehicle sound like my $1 anti-EPA Jeep, but I think it is pretty clear there are a few differences.

You are holding it wrong, don't drive it over large metal objects at high speed.

I love the boldness of the Tesla, I'm truly impressed by the PR skill of Mr Musk and his team. Let's hope they have enough data now to diagnose.

> I'm truly impressed by the PR skill of Mr Musk and his team

It's certainly a bold strategy, but perhaps a little risky. They must be confident it's not really a problem though, because if there was a real risk of fire in the car putting a release out like this could be problematic if, in the future, another car went up in flames and the driver did not escape uninjured.

Slightly unrelated - their PR team does alright, but they've had their fair share of mis-fires (if you'll excuse the pun). This is the same company that put together a libel suit against its critics that was so "gravely deficient" (the judge's words) it was thrown out of court (and a libel-friendly English court at that).


I was not aware of this libel suit; but it fits well with how I perceive the PR handling; what remains in the zeitgeist is a company fighting the right(?) battle using all means. The fact that said suit was gravely deficient most likely went largely unnoticed, and in the immediate it creates a us vs the rest mentality with the owners/enthusiasts; something that shows in this driver's account. Unless the driver is also a stockholder.

When Tesla does it, it's lauded as bold; but when the same thing is done by Steve Jobs (antennagate), it's derided

The jealous derided, but all in all it was pretty solid handling; they shipped a few bumpers for free, and discovered they could sell them for 29$ a piece at an even higher markup than the hw. Somehow I don't think this will go away with a free bumper, but with this type of strong will, it will be interesting to watch.

This is less like "you are holding it wrong" and more like a hypothetical response of "don't drop it" prompted by complaints of screen fragility.

Holding it wrong isn't an accident in the same way that hitting debris or dropping something is.

Does anyone know what actually cought fire? Can batteries catch fire due to being struck like that? If so, why did it take 5 minutes and how did the car electronics know about it beforehand?

If you strike the cells, they can be short circuited, leading to heating. Lithium cells can experience thermal runaway [http://en.wikipedia.org/wiki/Thermal_runaway#Batteries] when they're failing, heating adjacent cells causing them to fail. This is why cells are compartmentalized. Think of them like properly engineering bulkheads on a ship. If certain compartments fail, others are safely isolated.

The problem is, as long as drivers demand range with electric vehicles, and energy storage is much less than liquid petroleum, the bottom of the vehicle is the only place that large, heavy pack arrangement can go. You make the tradeoff: How much armoring needs to take place to avoid the most common damage/failure scenarios.

I have no doubt Tesla is learning quickly from these events, and is plaining alternate or improved methods to armor the pack from road debris and damage.

A gas tank is on the bottom as well, though I guess it doesn't run the entire length of the car either.

A gas tank presents a smaller profile under the vehicle than the Model S battery back, which covers a substantial portion of the undercarriage.

It's also usually located behind the rear axle. Something which is shaped in a way as to lodge itself against the road and the bottom of the vehicle to it is driven upwards is likely going to have done this before it gets to the rear axle.

Most of the vehicles on the road are front wheel drive and thus don't have a rear axle. However, the gas tank is usually mounted slightly higher than the floorboard in front of it, so that offers some protection as well.

The other thing to keep in mind is that the fuel tank is usually located in the rear of the vehicle while potential ignition sources (engine) is located in the front. This can reduce the risk of a fire as well. However, the exhaust system runs to the back of the car.

I am pretty sure the cells are compartmentalized so I would assume what happened was a slow process of each compartment heating up to a threshold eventually causing a chain reaction.

Aren't batteries under the cabin floor though? That hot-swap demo from few months ago seemed to imply that they were.

Yes, they are but I am saying the cells are in their own mini compartments. Think of like a ship has compartments to keep the entire thing from flooding if it is breached. At least that is how I have understood it to be. Obviously this doesn't prevent heat from spreading and could still have a runaway chain reaction like in this case but it does maybe give more time to warn you.

They are, but they have heat vents that spew off into the front, to protect the cabin itself. That is why the front of the car caught fire.

The battery itself is also segmented such that thermal runaway doesn't cause a cascade to the whole battery (which is why the driver here had ample time to continue driving and pull over).

I ask the engineers here, how can the fires be prevented/mitigated?

- A different armor plate (titanium? kevlar?) - An automatic fire extinguishing system, perhaps piping grid inside the battery compartment that can feed a cooling agent to the damaged cell?

Is price the only constrain? Cost benefit?

Is there literally any reason to believe that Tesla's are more predisposed to catching on fire? Surely hundreds of cars burn and some explode in the U.S. every day. Where are the apologies from their manufacturers?

I suspect the number of cars less than a year old that catch fire after striking road debris is vanishly small.

I have nothing other than anecdotes to support my claim, but those anecdotes are based on a little shy of a decade as a firefighter.

The argument is going to be that Tesla batteries cover the entire bottom of the car where other cars have the gas tank under the trunk. Probably, Teslas will get more armor underneath and that will satisfy everyone.

Yeah. Notice that these fires have mostly been from damage to the front of the battery pack, well away from where the fuel tank is in other cards.

More armor near the front of the pack, and a redesign of the front of the pack to deflect debris to the sides, so the pack doesn't take the brunt of the force.

These cars can raise and lower the suspension, right?

Might be useful to have it use scanning LiDAR and detect debris in the road, raise the vehicle when appropriate. They're working on a self-driving model, why not build that in.

I wonder if the Teslas should have explosive bolts to drop the battery pack if they detect a fire, then move the car away from it.

Good idea. Explosively eject a massive burning battery pack into the path of the unsuspecting traditional combustible car behind you and watch it burn in your rear-view mirror as you coast away on the backup emergency battery...

Which would increase the safety statistics of the model s over dinosaur burning vehicles, too!

Not sure how the car would know it was safe to drop the battery pack; you wouldn't want to drop it in the middle of an Interstate. Even moving the car away (can that happen w/o a battery pack?) how would it know which way to move safely without getting into traffic, hitting guard rails, emergency vehicles, etc.?

It looks like he had minutes in this case, so driving to the side of the road, then confirming dumping core, driving forward 10 meters, and shutting down, seems viable. You could presumably keep enough energy for this in ultra caps or a separate unaffected part of the pack, or do it with inertia.

Halon flooding battery packs?

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