I've personally witnessed a few that were the result of wrecks, and just the other weekend I drove by a couple guys trying to put out a flaming engine on a beat up old truck.
How exactly do these compare to gasoline/diesel powered vehicles?
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 two or more 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?
As a longer term fix, move the battery pack rearward and design in a little more protection.
Sure, debris can damage the underside and cause the car to catch fire, but putting the packs in the front or rear of the car can cause it to explode on impact as well. Having it on the underside will probably cause fewer fires than having it in the front for example.
That said, consider gasoline cars: The fuel needs to travel from the tank to the engine. Effectively, an impact anywhere on the fuel line can cause a fire.
Uh, yeah. Are you sure Li-ion batteries really explode, or do they just burn really fast? (In much the same way it's very, very difficult to get a gas tank to explode, but not so hard to get it to burn very fast.) I'm pretty sure it's hard to get them to explode.
You would be amazed the places people have put gasoline tanks on cars. Just behind the rear axle has been one of the stupidest, so it goes boom when someone drives into the back of you. http://www.autosafetyexpert.com/defect_fueltank.php
Just the one: 'if crush or penetration occurs perpendicular to electrode edges, that deformation is likely to result in high impedance shorting between electrode layers and initiate cell thermal runaway.'[1]
This is an incredibly thorough piece of research:
[1] Celina Mikolajczak et all, (2011), Lithium-Ion Batteries Hazard and Use Assessment (p. 57, paragraph 5)
Retreived from: http://www.nfpa.org/~/media/Files/Research/Research%20Founda...
So when you read statistics on car fires you should try to exclude those if you can.
Fire from road debris would be very very unlikely. How would that even happen? I suppose it could cut a water pipe, and then cause overheating.
Fires from a violent crash do happen of course, and no one would criticize Tesla for those types, but from road debris? That shouldn't happen.
How on earth would that make a better comparison?!
Then to be fair, one should also take into account the increased reliability of the electric drivetrain.
There have been a lot of problems with fuel tank placement, with some designs being responsible for spraying passengers with flammable fuel, which subsequently catches fire.
The design criteria for internal combustion cars seems to be to place the energy storage such that it minimizes the chance of damage, and to take steps to ensure that the contents do not endanger the passengers. Gas tanks are not designed to withstand highway speed collisions with pointed steel objects and never burn. To apply such standards to electic cars is a double standard.
By the general standards of passenger cars, I'd say that the Tesla model S is a bit fragile, but still quite safe.
What's fragile about 6mm armour plate? And what's safe about 100% of the fires having a single source? It sounds like TSLA needs to put the battery somewhere more protected. They have it exposed right now (presumably for lower CoG and better handling). That might just be a design flaw. I think we can still keep an open mind on LiIon untill the designs are iterated upon more.
Urgh. Nice context switch. To be fair, the system as a whole seems to be a bit fragile, which is what I was actually saying. But in this specific strawman context: Lots of things are "fragile" when a piece of steel has a significant fraction of the momentum of a car behind it.
To me, still very dependable and robust for something with sportscar performance.
It just feels like somebody's looking for an excuse to go after Tesla. I read these articles about people leaping over concrete barriers and wrapping their car around a tree and just wonder "what the hell did you expect would happen?"
Yes, quite improbable. It might break the engine, but there is nothing in the front of a car that would catch fire from such an impact.
So 194,000 vehicle fires per year, or 18,602 within any given five week period.
Toyota's market share is 14.2%, so if the fires are evenly distributed, there would've been 2,641 vehicles of that brand catching fire. That's pretty close to 3,000.
Tesla isn't the victim of a smear campaign, this is fairly minor news that gets amplified in the HN/tech bubble.
The key is that in both cases, the entire mass and momentum of the vehicle were contributing to the intrusion of a piece of steel into an aluminum vessel. No engineering in the world is going to stop that steel from penetrating in that case. A different material and/or different placement will be needed to improve the situation.