Third Tesla Fire in 6 Weeks Could Spark Federal Inquiry

"Could Spark Federal Inquiry"

Where is this claim coming from? Wired? I can't find any source. To me it seems like some writer for Wired figured they could get some clicks by speculating.

Face it, battery technology is not sufficiently advanced to deliver good range without some serious trade offs. The trade off of the Tesla may prove to be the wrong choice long term.

No one would ever suggest lining the bottom of a car with a gasoline tank, fortunately we don't have too because the power density is so high. Hence they can put tanks where a collision or road debris damage are least likely to damage them.

However Tesla needs a stupendous amount of battery to get its range. Hence we get large cars where they have chosen to isolate the entire pack at the floor of the car. They made the choice to dispense with a central tunnel which could hold more batteries, not use the front engine area or any trunk space.

There were to reasons for their design choice, first because of the sheer amount of batteries needed and second because of pack swapping. I don't think the trade off is worth it.

They can use some of the front "frunk" area to have a raised stack of batteries where the traditional firewall is and do similar in the rear. The could have a raised tunnel down the center line and reduce the need of having batteries so far forward. There were many choices available but they wanted swappable packs.

What statistic I want to see is, how many penetration events have their been versus how many fires. How many cells have to be penetrated to create a fire? Is there some flaw that another component is failing during these minor accidents that is causing the fires?

This story is unfortunate spin for two reasons. The minor reason is Wired appears to be completely speculating when they state, "Could Spark Federal Inquiry".

The second and really much larger reason this article is spin is that they are painting this as a major issue without giving enough information to quantify it. I try to quantify it in this comment and the results are the opposite of how Wired is spinning this issue. Here's what they said:

While there are an average of 150,000 car fires in the U.S. each year, with only 19,000 Model S sedans on the road, having three vehicles catch fire in six weeks has garnered plenty of attention.

So this is comparing two data sets:

A: % of Tesla Vehicles that catch fire. Dividing 3 by 19,000 leads to a fire incidence rate of 0.0158%.

B: % of all vehicles that catch fire. For this data set, Wired helpfully tells you the numerator of 150,000 vehicles catch fire in the U.S. but completely leaves out the denominator.

Without giving the complete information for data set B, it's difficult to determine if Tesla's fire incidence rate is out of the ordinary and warrants the speculation of, "Could Spark Federal Inquiry". So in an attempt to find the denominator, I discovered:

http://en.wikipedia.org/wiki/Passenger_vehicles_in_the_Unite...

Overall, there were an estimated 254.4 million registered passenger vehicles in the United States according to a 2007 DOT study

Seems reasonable to use this as the denominator. If anything, since not every registered car is regularly driven, it is likely a high estimate and therefore understates the percentage.

But calculating it, 150,000 divided by 254,400,000 equals a fire incidence rate of 0.059% for data set B. So the average passenger vehicle catches fire 3.73 times as often as a Tesla Model S. Now, caveats:

This is comparing an annual number (0.059%) for some other time period. Without thinking much about it, you might believe there is weight to Wired's assertion that this is "3 vehicle fires in 6 weeks". The Model S has been driving on the road for much longer than 6 weeks. In fact, retail deliveries started about a year and a half ago. While technically accurate, to frame the data as "3 fires in 6 weeks" is misleading due to cherry picking data.

This could be for any number of reasons, and also a big coincidence, and I don't have time or the interest to read more on it, but the thing that I kept thinking while I read the story was "why did you have to do that thing with Boeing... you don't look too good now".

Now that they did catch on fire, and the fire was suppressed every time, and everything was just ok... Well, now I'm beginning to trust electrical cars.

But they still are too expensive for me.

The comparisons to the Leaf and Volt are meaningless if none of those vehicles have been in similar accidents. You can't just point to numbers and imply that a lack of reported fires means they're safer.

There may be a problem. We can consider the Tesla as a car body bolted on top of a huge battery. Collisions with road debris seem to be sufficient to pierce the battery's armour and start a fire.

This isn't disastrous. Problems like this routinely emerge with new designs. And at least the flammable materials stay in one place (unlike a gasoline engine). But still, a fire's a fire, and I'm sure Tesla's engineers are working overtime trying to figure out a solution.

Alright, let's do the math.

150,000 car fires per year / 52 weeks is 2880 fires per week. There are 135900000[1] vehicles in the US, which gives 21.2 fires per million-vehicles week. With 19000 Teslas on the road and three fires in six weeks we have 0.5 (fires / week) / 0.019 (million vehicles) = 26.3 fires per million-vehicles week. So even if this is typical for the Model S (and it doesn't seem to be), the cars aren't much more likely to catch fire than ordinary cars. Also, I haven't accounted for the fact that the Model S's probably get driven more than your average passenger car, both due to low per-mile costs and the fact that they're more likely to be new and thus valued by their owners. Taking this into account would probably bring the Model S's fire-rate below gas cars again.

[1]: http://www.wolframalpha.com/input/?i=number+of+cars+in+us

They are having more accidents than other electric cars (3 vs 0), and it certainly seems that having four times as much battery power, and lining the base with them, is the problem.

There's nice spin you could put on this, which is likely true: people who have Teslas drive them more, because they are fun, cool, excellent - and have 4 times the range and power. Secondly, with more power, you will drive faster, hence greater likelihood of accident, and of greater severity.

But Tesla's gotta fix this. For PR reasons, and to be making a great car. There's always going to be unforeseen problems with new tech, the only issue is how you handle it.

It's a bit of a shame though: low slung batteries give low center of gravity and great handling and stability. Thicker armour adds unnecessary weight. Perhaps armour that deflects rather than stops? Perhaps a different failure mode for the batteries; built-in extinguishers? (i.e. the issue is fire, not car damage. Ideally, solve both).

Apparently the battery pack in a Tesla has liquid cooling so it probably gets fairly hot. In a gas car, the liquid cooling is for the engine and if it fails, the engine overheats and stops. But imagine if the gas tank itself got hot when running and needed to be actively cooled. That's basically where the Tesla is at. A failed cooling system means the energy source overheats (and not the motor/engine).

I'm not a car expert but I imagine it's hard to protect all the pipes that are carrying the liquid. And that may be why these fires are starting... some puncture causes the liquid to release. Just a theory.

A quick back of the envelope calculation shows that, at this rate, the Tesla Model S is roughly 25x more likely to suffer a fire after a collision than a non-Tesla.

While gas powered cars must, out of necessity, carry a tank of flammable liquid around, which is fairly unsafe, the gas tank is not in the front of the car. No other electric car manufacturer puts their batteries so far forward under the hood, either. The Tesla also has very low road clearance.

I mean, tbh I really don't care - I still want one. I feel like this is the same as saying people get struck by lightening.

In other news cars tend to burn when their fuel tanks are punctured after colliding with large objects at high speed.

It occurs to me that these fires do not pose a direct risk to the occupants, but do carry indirect costs:

- Firefighters will take longer to rescue injured from the passenger compartment

- The fire can possibly ignite spilled gas from other cars in a multi-car accident

- Insurance rates will be higher, as a collision is much more likely to total the car

You can't make an omelette without burning a few cars.

I was surprised with how many Leafs have sold. I rarely see one, but I see a Tesla at least twice a week these days.