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Model S Accident/Fire
- Thread starter joshuaeven
- Start date
From Jalopnik, very interesting:
Update: Earlier today I asked Dr. Stephen Granade, physicist and friend of Jalopnik, to help explain the difference between a lithium-ion battery fire and a gasoline engine fire. Here's what he told us.
[Mod Note: source link-> Jalopnik.com]
Update: Earlier today I asked Dr. Stephen Granade, physicist and friend of Jalopnik, to help explain the difference between a lithium-ion battery fire and a gasoline engine fire. Here's what he told us.
P
The thing about lithium ion batteries is that they can catch fire on their own in a way that you don't see with gasoline in a car's tank. It's actually really hard to make gasoline burn without introducing flames. You have to heat gasoline up to around 500 degrees F before it self-ignites and undergoes what chemists call "thermal runaway", where the gas is producing more heat than it's losing to the gas tank or the air around it. Lithium ion batteries, however, can experience thermal runaway at temperatures as low as 200 degrees F. Now, it can take days before the battery will catch fire, but it gives you an idea of how much easier it is to get a lithium ion battery to catch fire than it is with gas.
Thermal runaway happens because the poles of the battery, called the anode and the cathode, are highly reactive. They undergo reactions that give off lots of heat, and as they heat up the reaction happens faster and faster. Lithium ion batteries are popular because they can carry a lot of energy. Their energy density — how much energy you can store per pound of battery — is really high. But that means that they have a lot of energy that can be converted into a spectacular fire. Even worse, they're filled with a highly-flammable material that's under pressure. When you draw electricity out of one of these batteries, lithium ions carry electrons from the anode to the cathode to give you an electrical current. The lithium ions move through something called an electrolyte. The electrolyte separates the anode and the cathode but lets the ions move from one to the other. It just so happens that the best electrolytes for lithium ion batteries are also really flammable.
What probably happened to that poor Tesla S is that the debris in the road crunched one or more of its batteries in a way that made a direct electrical path between its electrodes. When that happens, it's like dropping a crowbar across a car battery. Electricity flows freely and the battery gets a lot hotter than it's designed to withstand. High-capacity batteries like the ones in the Tesla S have multiple cells in them so that they store more energy. Each cell is like its own mini battery, kind of like how you have to put multiple AA batteries in a flashlight. A fire in one cell can cause the surrounding cells to overheat and catch fire, and pretty soon you're off to the races.
This is a known issue, and is why lithium ion battery manufacturers do everything they can to make their batteries withstand damage and they firewall off individual cells to keep thermal runaway from happening in the whole battery. Tesla also puts firewalls between individual battery packs for the same reason, but if you get a hot enough fire, then all of the cells in all of the batteries will burn.
I've heard talk about how water didn't put out the fire because lithium ion batteries have lithium in them, and lithium catches fire when you expose it to water. It's true that lithium catches fire in water, as I accidentally proved in one of my chemistry labs. But there's very little free lithium in the batteries. Instead the lithium is either shoved inside the anode and cathode material or is bound up as a salt in the electolyte. Water won't make a lithium ion battery catch fire. What I'm guessing happened is that the firefighters put out the parts of the car that were burning, but didn't shoot enough water up under the car to cool down the batteries and stop the thermal runaway. That would let the batteries keep burning inside until the whole thing re-ignited again, possibly worse than before if more cells in the battery had also caught fire. I saw in the accident report that they were able to put out the fire by applying enough water directly to the battery pack's insides to bring down the temperature and put out the flames. Tesla's own directions to first responders states that, if the battery is on fire, it needs to be cooled down with plenty of water.
Thermal runaway happens because the poles of the battery, called the anode and the cathode, are highly reactive. They undergo reactions that give off lots of heat, and as they heat up the reaction happens faster and faster. Lithium ion batteries are popular because they can carry a lot of energy. Their energy density — how much energy you can store per pound of battery — is really high. But that means that they have a lot of energy that can be converted into a spectacular fire. Even worse, they're filled with a highly-flammable material that's under pressure. When you draw electricity out of one of these batteries, lithium ions carry electrons from the anode to the cathode to give you an electrical current. The lithium ions move through something called an electrolyte. The electrolyte separates the anode and the cathode but lets the ions move from one to the other. It just so happens that the best electrolytes for lithium ion batteries are also really flammable.
What probably happened to that poor Tesla S is that the debris in the road crunched one or more of its batteries in a way that made a direct electrical path between its electrodes. When that happens, it's like dropping a crowbar across a car battery. Electricity flows freely and the battery gets a lot hotter than it's designed to withstand. High-capacity batteries like the ones in the Tesla S have multiple cells in them so that they store more energy. Each cell is like its own mini battery, kind of like how you have to put multiple AA batteries in a flashlight. A fire in one cell can cause the surrounding cells to overheat and catch fire, and pretty soon you're off to the races.
This is a known issue, and is why lithium ion battery manufacturers do everything they can to make their batteries withstand damage and they firewall off individual cells to keep thermal runaway from happening in the whole battery. Tesla also puts firewalls between individual battery packs for the same reason, but if you get a hot enough fire, then all of the cells in all of the batteries will burn.
I've heard talk about how water didn't put out the fire because lithium ion batteries have lithium in them, and lithium catches fire when you expose it to water. It's true that lithium catches fire in water, as I accidentally proved in one of my chemistry labs. But there's very little free lithium in the batteries. Instead the lithium is either shoved inside the anode and cathode material or is bound up as a salt in the electolyte. Water won't make a lithium ion battery catch fire. What I'm guessing happened is that the firefighters put out the parts of the car that were burning, but didn't shoot enough water up under the car to cool down the batteries and stop the thermal runaway. That would let the batteries keep burning inside until the whole thing re-ignited again, possibly worse than before if more cells in the battery had also caught fire. I saw in the accident report that they were able to put out the fire by applying enough water directly to the battery pack's insides to bring down the temperature and put out the flames. Tesla's own directions to first responders states that, if the battery is on fire, it needs to be cooled down with plenty of water.
[Mod Note: source link-> Jalopnik.com]
Last edited by a moderator:
I added a post wiki near the top of the thread: Model S Accident/Fire - I'm VERY curious as to what caused the fire...
Please got there for useful info and please only add useful to that post.
Please got there for useful info and please only add useful to that post.
I absolutely could not agree more. Ask Ford how many Crown Vic's caught fire in rear end collisions (Hint: So many they added a fire suppression system as an option in later years). I personally think everyone should have at a MINIMUM an ABC Extinguisher in their vehicle, if not a HALON (or similar) system. Most vehicle fires become fully consuming events in under 2 minutes. Based on the photos, 95% of what is burning is material, paint and body panels. This would cause multiple shorts across all power systems. (There doesn't seem to be any attempt to have cut the main power in the Frunk before the fire advanced) I would suggest that this should be changed to a KILL SWITCH that can be easily thrown to disconnect the main battery easily instead of having to remove panels and cut a section of wire.
Also, based on the photos I am not convinced the battery pack itself actually caught fire. It could have easily been the controller in the wheel well, keeping in mind most Firefighters wouldn't know a Tesla Battery Pack from a Bag of Grapes. Either way, the fact that the car warned the driver, allowed him to exit safely, and kept the fire out of the passenger compartment speaks volumes. Remember, safety is judged on the safety of the occupants, not the death of the car.
I read a lot of posts here about statistics, that cars DO catch fire from time to time. Tesla is a car. It's therefore a non-event. All is fine.
But what if a Tesla car has 5 times more probability to catch fire than normal car? Still acceptable? Yet maybe not the kind of Tesla standards you are used to.
Would you still prefer driving an EV if this is statistically 5 times less fire proof and yet very safe in all other types of road accidents?
But what if a Tesla car has 5 times more probability to catch fire than normal car? Still acceptable? Yet maybe not the kind of Tesla standards you are used to.
Would you still prefer driving an EV if this is statistically 5 times less fire proof and yet very safe in all other types of road accidents?
Then we would have seen 20 Tesla's up in flames by now, instead of just 1.
This sort of wild and rampant sensationalist speculation is what sells newspapers, but it's not the case here. Please don't add unnecessary speculation to this thread which is about a statistically provable anomaly.
what if unicorns can fly or pigs exist .... its not relevant
Edit: and by the way welcome to the forum .... odd first post
Wrong. What stats are saying is 1 gas car out of 1000 catches fire.
Tesla has 20.000 cars so its 1 out of 20.000. So its 20 times safer.
This is wrong.
It's 1 car out of 1000 cars DURING THE CARS LIFETIME. So let's say 10 years (car lifetime) and its being reasonable.
Put the equation to 1 year: this is statistically equivalent to 1 gas car out of 10.000 cars do catch fire.
Now how old are the 20.000 Tesla cars in average? 6 months maybe.
So Tesla is "in the average" of 1 out of 1000.
Yet this is a brand new model top performing car. You would expect better figures don't you?
Tesla has 20.000 cars so its 1 out of 20.000. So its 20 times safer.
This is wrong.
It's 1 car out of 1000 cars DURING THE CARS LIFETIME. So let's say 10 years (car lifetime) and its being reasonable.
Put the equation to 1 year: this is statistically equivalent to 1 gas car out of 10.000 cars do catch fire.
Now how old are the 20.000 Tesla cars in average? 6 months maybe.
So Tesla is "in the average" of 1 out of 1000.
Yet this is a brand new model top performing car. You would expect better figures don't you?
@Mitia
There are 250,000,000 registered cars in the US. About 200,000 fires EVERY year. That means the chance of a gas car catching fire is 1:1,250. This is not over the lifetime of the car. This is the odds of the average car catching fire per year. So a Tesla is at least 10 times less likely to catch fire than a gas car at this point.
There are 250,000,000 registered cars in the US. About 200,000 fires EVERY year. That means the chance of a gas car catching fire is 1:1,250. This is not over the lifetime of the car. This is the odds of the average car catching fire per year. So a Tesla is at least 10 times less likely to catch fire than a gas car at this point.
These statistics would only be relevant if vehicle age is a factor in vehicle fires. In other words if cars with an age of over five years caught fire more frequently than cars under five years. I'd be more inclined to think that miles driven is more important. 83 million miles = 1 Tesla fire, 10 and a bit million miles = 1 ICE fire.
your first post said what if they are 5 times more likely to catch fire? ... now are you saying they are no more likely than any other car?
surfingslovak
Member
OK my reasoning is the following. Pretty simple in fact: the exposed surface of a Tesla is the entire battery pack (the whole lenght of the car in between the weels). The exposed surface of a gas car is its tank which I estimated taking 5 times less space.
So basically if you hit a perforating object on the road, on a Tesla there is great chance it will hit the battery because it occupies a big surface.
And if something perforate the battery pack... well you know the end of the story. I don't believe you can perforate this battery at 50 miles and don't expect one of the 16 compartment not to catch fire. Don't you think?
So basically if you hit a perforating object on the road, on a Tesla there is great chance it will hit the battery because it occupies a big surface.
And if something perforate the battery pack... well you know the end of the story. I don't believe you can perforate this battery at 50 miles and don't expect one of the 16 compartment not to catch fire. Don't you think?
Captain Ohsahi and his team (and other fire depts) should take it upon themselves to learn about Tesla:
Here's a nice page for them to start: http://www.teslamotors.com/firstresponders
Finally someone (else) broke the ice on this point. I got so much negative rep earlier in the thread when I pointed out how the stats shouldn't apply to Tesla, that it wasn't worth pushing the subject!
The right comparison is fire frequency for cars that are < 1 year old. US data sources don't break it out by age cohort, so we don't know. But intuitively it's very low. (unless you are a ferrari!) The 150k per year is for the entire US car fleet which averages 10-11 years old....
I give Tesla a free pass on the first one, statistically speaking
1 data point is only enough for chicken little.If folks want to be educators, maybe better to focus on Tesla's design quality vs. shrugging it off using a bad statistic.
JRP3
Hyperactive Member
They already did. http://www.teslamotors.com/firstrespondersOhashi said firefighters may need a course on how to handle electric cars. He also said Tesla may provide guidance.
"Maybe now they'll come up with some sort of procedure to share with our industry," he said.
Tex beat me to it.
Here is a recent comment from Tesla: "Tesla Says Car Fire Began in Battery"
"....Company spokeswoman Liz Jarvis-Shean said the fire Tuesday was caused by a large metallic object that directly hit one of the battery pack's modules in the pricey Model S. The fire was contained to a small section at the front of the vehicle, she said, and no one was injured...."
Tesla Says Car Fire Began in Battery After Crash - ABC News
"....Company spokeswoman Liz Jarvis-Shean said the fire Tuesday was caused by a large metallic object that directly hit one of the battery pack's modules in the pricey Model S. The fire was contained to a small section at the front of the vehicle, she said, and no one was injured...."
Tesla Says Car Fire Began in Battery After Crash - ABC News
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