Days After A Fiery Crash, a Tesla's Battery Keeps Reigniting (mercurynews.com)

An anonymous reader quotes the Mercury News Six days after a fiery crash on Highway 101 involving a Tesla Model X took the life of a 38-year-old San Mateo man, the car's high-voltage lithium-ion battery re-ignited while sitting in a tow yard, according to the Mountain View Fire Department... The battery reignited twice in the storage yard within a day of the accident and again six days later on March 29. Two weeks later, in an effort to avoid more fires, the NTSB and Tesla performed a battery draw down to fully de-energize it...

On the company website, Tesla wrote "the reason this crash was so severe is that the crash attenuator, a highway safety barrier which is designed to reduce the impact into a concrete lane divider, had either been removed or crushed in a prior accident without being replaced. We have never seen this level of damage to a Model X in any other crash"... Tesla also reported that the vehicle's autopilot function was active at the time of the crash...

The National Transportation Safety Board is investigating the Highway 101 crash and three other accidents also involving Teslas, including a fiery 2014 Model S crash Tuesday in Florida that killed two teenagers. Also under investigation: A Model S crashed into a fire truck near Culver City in January, and the driver reportedly said Autopilot was engaged at the time. And it is looking into a battery fire of a Model X that drove into a home's garage in Lake Forest in August.
Two hours after that story was published, a Tesla smashed into a Starbucks in Los Gatos, California.

Comments

The desperate schmucks...

[Type44Q]

The desperate schmucks who've shorted Tesla would love nothing more than another headline but the implication here (that Li-ON is even less stable than some of us may have realized) affects Tesla only indirectly... and effects their [viable, prospective] competition equally.

Eyebrow raising but otherwise changing nothing.

Re:The desperate schmucks...

[Rei]

That said, with the amount of energy that's stored in electric car batteries

Electrical energy stored != combustion potential energy, and combustion potential energy != energy that can be practically released in normal circumstances (there's five times more potential energy to be released from the combustion of 1000kg of alumium or graphite vs. 1000kg of nitroglycerine, but which one would you rather be next to in a crash?).

It is not the "energy" stored in the batteries in "lithium battery fires" as you put it. First off, they're lithium-ion batteries, not lithium batteries, and yes, there's a big difference. There's no metallic lithium in lithium-ion batteries unless they've been abused (plating out of lithium at the anode is a failure mode, due to attempting to overcharge a cell or charging at too low of temperatures - both of which are prevented in a proper EV battery pack). The power (not energy) of the cell may provide a (significant) short-circuit ignition source if crushed, but what happens thereout depends on the chemistry of the cell; the fire from a burning cell (in varieties that are capable of burning) is most often the electrolyte (of which there are many varieties). The rest of the cell just isn't that flammable; the anodes are predominantly carbon (graphite or amorphous, sometimes with silicon) and the cathodes are metal oxides. The lithium itself is present as ions (hence the name) intercalated (in small quantities) in the lattices of the graphite and metal oxides.

What happens in a battery pack, however, is a bit different from an isolated cell. In a ruptured, internally-short-circuiting cell in a battery pack, the heat and contents are released, but they're released into non-flammable temperature-regulated pack coolant. Aka, quenched. Packs also employ a variety of processes to physically isolate cells from each other. Normally, cell failures are self-extinguishing in a pack. The problem with this accident is that it was so energetic that it utterly mangled the battery pack. Which is hard to do, as the pack lies within the wheelbase, but "high speeds into a concrete barrier" is a huge amount of impact force. When storing this pack, there was almost certainly no coolant left, and a lot of damaged cells. Yes, the remaining charge was an ignition source, but it's not what you see physically burning; on its own, a short circuiting cell just makes itself very hot. Anything that happens after that is a result of the consequences of that heat - and more specifically, the results of that heat on the electrolyte.

Tesla will need to adjust the storage procedures for such heavily damaged wrecks. This appears to be the first case of reignition days after extinguishing in the company's history, but it'll need to be accounted for.

Either way, the rate of EV in general (and Tesla in specific) fires is much less than with ICEs.

Re:Tell me again how Lithium Ion batteries are saf

[bobby]

Any energy storage system will have inherent danger, and the more concentrated it is, the worse the possible result. But you knew that.

As bad as battery fires are, they don't spread like a chemical fuel fire can and often does.

Re:So where's the "Honda crashes into bus!" storie

[Gravis Zero]

So where's the "Honda crashes into bus!" stories?

Right here

Where are the headlines about some random kid who died in a pickup truck this weekend?

Oh please! He didn't die in the pickup truck.

Or the old lady in her Ford Fiesta who ran into a parked car?

Apparently, not a lot of old ladies drive a Ford Fiesta... but when they do, it's epic. ;)

Dodge: opening the door while stopped engages Park

[raymorris]

> For whatever reason people make this mistake all the time

In my Dodge, if I open the door while the car is stopped, it automatically goes into park.

Humans screw up all the time. Good systems are designed so that mistakes that happen "all the time" don't cause your car to drive through a Starbucks.

Re:Tesla smashed into starbucks

[sjames]

Well, let's see, I have had a car suffer complete electrical failure while driving it before. Because it had a mechanical linkage between the steering wheel and the front end, I just pulled over. Because the brakes were a simple hydraulic link, I was able to stop.

I also had a brake failure once. Because the emergency brake was a simple cable link between pedal and the brakes, I was able to stop safely.

Drive by wire would have been a problem in either event.

Re:Dodge: opening the door while stopped engages P

[drinkypoo]

In my Dodge, if I open the door while the car is stopped, it automatically goes into park.

If I were you, I wouldn't crow too loudly about FCA safety features.

Good systems are designed so that mistakes that happen "all the time" don't cause your car to drive through a Starbucks.

If only FCA cared about drivers of vehicles other than your Dodge.

Re:Duh: drain the batteries ...

[sphealey]

= = = Unlike gasoline or diesel, which can still ignite after being drained from the tank, electricity is pretty much harmless once you've discharged it into a ground, like say the ground. = = =

There's a pretty common belief, probably stemming from how we are taught about electricity in 2nd and 3rd grade, that Gaia maintains reservoirs of electrons and positrons at the Earth's core and that electricity will "seek a path to ground", presumably to be stored in this reservoir for future deployment by the various gods/goddesses of lightning, the ghosts of Edison, and Tesla, etc. This is to put a fine point on it not true; if you connect a Tesla battery 'to the ground' (presumably by sticking some sort of metal toothpicks in the nearest soil and connecting the battery leads to it) at best you will get some slightly warmer soil in the vicinity of those toothpicks while the battery pretty much holds its original charge. The emergency services would have to carry around 1 MW resistors to use as the energy sink, and those things are not small or cheap ( http://www.jovyatlas.com/ja/Te... )

Re:Tesla smashed into starbucks

[Rei]

Don't recall Elon telling us about that.

It's well known among Tesla owners.

More like 90 a day in the US. Maybe 500 a day worldwide?

Nearly 1.3 million people die in road crashes each year, on average 3,287 deaths a day.

Were you unaware that Tesla sells vehicles worldwide?