Tesla Fire in Lithium Battery Destroys Vehicle

(Last Updated On: August 26, 2017)

abstract fire on blackScience Fact:  Tesla fire: on Tuesday last week near Seattle, a Tesla Model S electric vehicle driving on a state highway ran over some metal debris and damaged its lithium-ion battery pack. The driver stopped and evacuated safely before the car burst into flame.

Car batteries have caught fire before during testing, but the Tesla fire is only the second report of a fire following a crash. I’m not an expert in lithium-ion batteries, which are a complicated subject. However, as a scientist and an enthusiastic owner of a GM Volt, I felt that this event called for a comment. After all, people want to know, am I risking my life to ride a car with one of these batteries? For that matter, how about an aircraft?

The following table compares the battery packs of three electric vehicles – a Tesla of the type that caught fire, the LEAF full electric and the Volt hybrid.

Table - EV table

Several things pop out in this table:
– The Tesla is carrying around a lot more electrical energy – 3.5 to 5 times – than these other vehicles
– The Tesla is packing more energy per pound into its battery, which probably means their battery technology is pushing closer to its limits
– The Tesla is configured to allow 8 times faster charging of a much larger battery; this may mean thinner components, or more experimental materials, which again suggests technology being pushed close to the limits

The Tesla is a $70,000-plus car with an advertised top speed over 120 mph. That type of car is likely to be pushed harder, and driven faster, than a car advertised primarily for its low operating costs (“never buy gas”). When you add that to the comparisons above, it’s not surprising that if an electric vehicle is ever going to burst into flame, a Tesla fire might be more likely than some others.

Science Speculation:  But let’s examine the “if” in that last sentence. Just how much energy are we talking about, anyway?

Consider the Ford Escape, the all-gasoline version, which according to Edmunds.com is one of the four most popular SUVs. Its gas tank holds 15.1 gallons, which is a typical size for many cars.

Gasoline has chemical energy of about 36 megajoules per liter. When you convert the units (a megajoule equals 0.28 kilowatt-hour, a liter is 0.264 US gallons), the Escape is carrying around 576 kilowatt-hours of chemical energy. In other words, 7 times as much as that fiery-hot Tesla!

What’s the difference? An expert could list many fundamental differences in the technologies. But I say, we’ve had more than 100 years to improve the design and manufacturing of cars to the extent that we consider them safe to drive, even at high speeds. Today’s electric vehicles have been so carefully engineered that overall, I believe they are just as safe as gasoline vehicles. And 100 years from now, people will wonder what the fuss was about.

The Tesla fire is scary news, but so far a unique event. Does the appeal of never buying gas overcome your concern about the risk of new technology?

Sources:

http://www.teslamotors.com/models/features#/battery
http://gm-volt.com/full-specifications/
http://www.mynissanleaf.com/viewtopic.php?f=8&t=12866
http://www.teslamotors.com/models/features#/batteryhttp://gm-volt.com/forum/showthread.php?4471-Tesla-S-weight-Battery-size
http://www.nissanusa.com/electric-cars/leaf/charging-range/charging/

Comments

Tesla Fire in Lithium Battery Destroys Vehicle — 4 Comments

  1. The Tesla fire is worrisome but as Art says fires of gasoline powered vehicles after a crash happen sometimes too. Lithium ion batteries however are not only new technology but they have some unique properties that make careful design essential.
    1. Batteries contain not only combustible items, lithium and organic electrolyte, but the oxygen to support combustion. This is unlike gasoline that requires the presence of oxygen and spark to start a fire. A lighted matched dropped into a gas tank will not cause a fire because the vapor in the tank does not contain oxygen. PLEASE DO NOT TRY THIS.
    2. The voltage of every single cell and there are between 100 and 150 in every vehicles that Art mentions needs to be controlled during charging very precisely. A few millivolts in 4.2V make a difference. This clearly is not the cause of the Tesla fire
    3. Exposing the battery to high temperature can lead to a fire. The ignition temperature depends on the battery chemistry. Generally the battery with the highest energy density is the most susceptible to fire and Tesla has one of the highest density chemistries
    4. We need to know more to determine what caused the fire last week, but if the car hit a piece of metal that punctured the battery case, friction and the impact could have caused the fire two ways
    a. Raise the battery temperature to ignition or
    b. Provided a short circuit between the anode and cathode and the discharged electrical energy could certainly cause ignition
    The Tesla fire is not unique. In addition to the Volt fire that was primarily caused by NHTSA’s careless handling of the vehicle after a test charge there have been several instances of batteries’ causing fires. There was a massive recall of Sony laptops in the 90’s and a crash in a UPS airplane in Dubai in 2011 was attributed to a load of batteries. This is why the US Postal service asks if a package has batteries before accepting it for shipment.

  2. Art, when Boeing had the problem of using I think the same batteries, on a plane that had a lot of plastic,( which has an off-gassing problem) I felt they had created their problem of the fires.
    Does the Tessla have any plastic near the battery?
    June

    • June, so far as I know electric vehicle batteries are sealed systems, so nearby plastics should not be an issue. I think the main risks are physical damage or a thermal runaway due to poor electrical design. Hopefully they have learned enough to avoid thermal runaway, so it at this point it should mainly be a question of protecting the integrity of the package. I expect that a stronger barrier beneath the battery will be added to the Tesla. However, it will be interesting to read the NTSB report on the incident.