Tesla Stock Plummets After Model S Catches On Fire — So Are Lithium-Ion Batteries Safe?

In a word, yes.

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It’s been a rough week for electric-car luminary Elon Musk. One of his company’s vaunted Tesla Model S luxury sedans — Consumer Reportstop-scoring auto ever — burst into flames on Tuesday, October 1, sending Tesla’s stock price down over six points and conjuring a slew of media stories about lithium-ion battery-related fires. You may recall, for instance, that Boeing‘s 787 “Dreamliner” was voluntarily grounded for several months earlier this year after multiple reports of battery-related fires (it seems overcharging the batteries was the likely culprit).

The video at the top of this post shows the Model S fire captured by a spectator (no one was injured, thank goodness). “Wow, I can feel the heat in here,” he says as he drives past.

So let’s get down to it: Are lithium-ion batteries safe?

In a word, yes, and we know this in part because of how pervasive they are. They’re found in nearly everything we use nowadays, from laptops, tablets and smartphones to cameras, gaming handhelds, power tools — even NASA‘s Mars Curiosity rover. You could say lithium-ion battery tech is ubiquitous in tech-dom — we couldn’t do most of what we do today without it. And while the notion that something with any kind of battery in it might spontaneously combust isn’t inconceivable, the probabilities are statistically insignificant. Battery tech isn’t flawless, but that’s not the question — the question’s whether it’s safe enough.

In the Tesla Model S’s case, recall that the National Highway Traffic Safety Administration awarded it its topmost 5-star safety ranking — the highest of any car tested. It’s also important to note that in the case of this particular Tesla Model S, a Tesla spokesperson said the fire resulted because the car “collided with a large metallic object in the middle of the road, causing significant damage to the vehicle,” adding that “Because each module within the battery pack is, by design, isolated by fire barriers to limit any potential damage, the fire in the battery pack was contained to a small section in the front of the vehicle.”

In other words, assuming Tesla’s statement is accurate, the car didn’t spontaneously ignite. It hit something first, and after it hit, there were safety mechanisms in place to contain it. How and where the vehicle impacted, whether the impact damaged the battery, what ultimately caused the battery to ignite — those questions and others remain and deserve answers. But there’s probably a correlation between the crash and battery fire, and as Autoblog Green notes, “there were 187,500 ‘highway vehicle fires’ in the US in 2011 (the last year for which data is available) according to the National Fire Prevention Association.”

How do lithium-ion batteries work? You take lithium — a soft, silvery metal employed in industrial components, from heat-resistant glasses and ceramics to both standard lithium and rechargeable lithium-ion batteries — and create a compound whereby the lithium ions swap electrode positions to “charge” or “discharge.” As rechargeable battery tech goes, lithium-ion is pretty much king of the hill when it comes to factors like energy density and charge retention over time.

If you rupture, overheat, short-circuit or overcharge a lithium-ion battery, you can cause problems that in some cases might lead to the battery combusting. But then gasoline isn’t the safest compound to be around if you’re crashing vehicles (or for that matter, planes) with fuel-laden, rupturable tanks into other objects at high velocities. I once accidentally clipped a median and knocked the oil pan off the bottom of a 1995 Dodge Neon; afterward, not realizing the pan had come off, and revving the accelerator because the engine was sputtering, I caused enormous flames to shoot from beneath the hood of the car (the car was fine, but not my best moment).

The point being that accidents happen. We deserve to know why this one happened and to what extent the battery behaved as expected. But in the meantime, we also need to be smarter than Wall Street’s fair-weather gamblers, and keep our reactions in perspective.