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Tesla Model S achieves best safety rating of any car ever tested

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Re: Tesla Model S achieves best safety rating of any car ever tested

#161

Post by ErsatzVerkehr »

jlgreco wrote: post #150
agumonkey wrote: post #137

Earlier quoted context omitted.

And I guess it's unrealistic to think of a special draining device to be brought on crash sites to exhaust the car battery. All in all, are electric vehicles more 'instable' energy wise when crashed, compared to petroleum based one ? or is it different flavours of similarly sh*tty situations ?

85KWh is a lot of energy. Back of the envelope calculations puts that at enough to boil around one metric ton of water from 25C.[1] If you wanted to rapidly drain a Tesla you would have to dump that energy somewhere. That might actually be plausible for firefighters to do[2], but I doubt the battery itself would withstand being drained anywhere near fast enough for an emergency situation. It would probably find some…

That's the amount of energy needed to bring nearly 1000 kg of water from 25°C to 100°C, but not enough to begin the phase transition from liquid to gas (i.e. start boiling).

The heat of vaporization of water (i.e. the amount of energy required to convert liquid water at 100°C to vapor at the same temperature) is 2260 J/g. So to completely boil your metric ton of water at 100°C would require an additional 1000 kg * (2260 J/g) = 2.3 GJ, which is 627 kWh!

At 85 kWh, the Tesla's battery contains enough energy to completely boil off 119 kg of water starting at 25°C [0], which is still pretty impressive!

[0] 85 kWh / ((4.181(J/(g * K)) * 75 K) + (2260 J/g))

Re: Tesla Model S achieves best safety rating of any car ever tested

#162

Post by rplnt »

nonchalance wrote: post #25

Isn't this old news? ( http://www.treehugger.com/cars/tesla-model-s-gets-5-star-saf... was posted two weeks ago: http://www.treehugger.com/cars/tesla-model-s-gets-5-star-saf... )

Should be, as these test are done before they can enter the market.

Re: Tesla Model S achieves best safety rating of any car ever tested

#163

Post by jlgreco »

abalone wrote: post #153
jlgreco wrote: post #150

Earlier quoted context omitted.

85KWh is a lot of energy. Back of the envelope calculations puts that at enough to boil around one metric ton of water from 25C.[1] If you wanted to rapidly drain a Tesla you would have to dump that energy somewhere. That might actually be plausible for firefighters to do[2], but I doubt the battery itself would withstand being drained anywhere near fast enough for an emergency situation. It would probably find some…

Also remember we're talking about an accident scenario. There's no way emergency responders would intentionally run a high voltage circuit like that where there's a risk of short circuit in a physically compromised vehicle. They're going to be focused on containing the energy not draining it. It is fun to do back of the envelope calcs though.. You could run 50 space heaters for an hour off that sucker. Insane.

> It is fun to do back of the envelope calcs though.. You could run 50 space heaters for an hour off that sucker. Insane.

Wolfram Alpha puts it at 1/5th the energy in a typical lightning bolt... Absolutely nuts.

Re: Tesla Model S achieves best safety rating of any car ever tested

#164

Post by jlgreco »

ErsatzVerkehr wrote: post #161
jlgreco wrote: post #150

Earlier quoted context omitted.

85KWh is a lot of energy. Back of the envelope calculations puts that at enough to boil around one metric ton of water from 25C.[1] If you wanted to rapidly drain a Tesla you would have to dump that energy somewhere. That might actually be plausible for firefighters to do[2], but I doubt the battery itself would withstand being drained anywhere near fast enough for an emergency situation. It would probably find some…

That's the amount of energy needed to bring nearly 1000 kg of water from 25°C to 100°C, but not enough to begin the phase transition from liquid to gas (i.e. start boiling). The heat of vaporization of water (i.e. the amount of energy required to convert liquid water at 100°C to vapor at the same temperature) is 2260 J/g. So to completely boil your metric ton of water at 100°C would require an additional 1000 kg * (2…

Ah very true. Knew I was forgetting something.

Re: Tesla Model S achieves best safety rating of any car ever tested

#165

Post by simonb »

ghayes wrote: post #72
iandanforth wrote: post #7

Favorite quote: "[T]he exact number is uncertain due to Model S breaking the testing machine"

My favorite was "While this is statistically unlikely to remain the case long term, Tesla is unaware of any Model S or Roadster occupant fatalities in any car ever."

There aren't that many on the road to begin with. To put this into perspective: during 1990-1994 there were 5 fatalities in Volvo 240s with 186000 cars on the road [http://www.iihs.org/externaldata/srdata/docs/sr3009.pdf]

Also the roof holding 4 additional cars, that's cute http://www.aronline.co.uk/blogs/wp-content/uploads/2011/09/v...

Re: Tesla Model S achieves best safety rating of any car ever tested

#166

Post by lutusp »

gargoiler00 wrote: post #157
OGC wrote: post #77

The lack of critism in this thread is astounding.

HN has a raging hard-on for tesla. It's not surprising, but I agree it's ridiculously one sided here. Personally, I hope Tesla fail, and think they will.

> Personally, I hope Tesla fail, and think they will.

Maybe, but you need to realize that the electric car is an obvious and timely technological development, and someone will produce a successful mass-market electric car. Why not Tesla? It's not as though they're making a lot of mistakes.

Re: Tesla Model S achieves best safety rating of any car ever tested

#167

Post by eru »

gargoiler00 wrote: post #157
OGC wrote: post #77

The lack of critism in this thread is astounding.

HN has a raging hard-on for tesla. It's not surprising, but I agree it's ridiculously one sided here. Personally, I hope Tesla fail, and think they will.

Why do you hope for that?

Re: Tesla Model S achieves best safety rating of any car ever tested

#168

Post by lostlogin »

sliverstorm wrote: post #112
spullara wrote: post #102

Earlier quoted context omitted.

I'd gladly go up against every sports car that the Tesla beats off the line and the quarter mile. Which is quite a few.

Err... what? If what you are trying to say, in the most roundabout way possible, is the Tesla accelerates fast- sure. But so does a top fuel dragster, and neither is a sports car. A sports car is a small, usually two seat, two door automobile designed for spirited performance and nimble handling. Sports cars may be spartan or luxurious but high maneuverability and minimum weight are requisite. -- Wikipedia (Notice it…

That's surprising to me. I have always considered a sports car to have a bit of extra power. I guess I'll have to open my mind a bit.

Re: Tesla Model S achieves best safety rating of any car ever tested

#169

Post by abalone »

lutusp wrote: post #155
abalone wrote: post #151

Earlier quoted context omitted.

Wish I had your crystal ball. With improvement, I was referring to the complexity of cutting someone out of a Tesla and all the no-cut zones that could electrocute passengers, emergency responders, even guys towing wrecks. You're right, there is no real safety record yet.

> With improvement, I was referring to the complexity of cutting someone out of a Tesla and all the no-cut zones that could electrocute passengers, emergency responders, even guys towing wrecks. As an electrical engineer with spacecraft experience, I can say that a car like the Model S isn't likely to electrocute anyone. While extracting someone from a wreck, emergency workers use tools like the "jaws of life", stron…

Hi there. Go ahead and watch this video from Tesla about how to cut someone out of a Tesla. The very first step is to cut the circuit like you say, but there are a few things you overlooked.

Much of the video is concerned with instructing responders how to cut around components that may remain electrified such as the converter and capacitors which, in Tesla's own words, present a "serious hazard of shock" because "they can release up to 400 volts in just an instant."

http://www.youtube.com/watch?v=ntK3rvVl2Qw

Re: Tesla Model S achieves best safety rating of any car ever tested

#170

Post by lostlogin »

lsc wrote: post #101
rdtsc wrote: post #32

Earlier quoted context omitted.

> Elon has mentioned how much they prioritized safety in designing the Model S. Definitely a smart move. If nothing this gives them a smaller attack surface against attacks from Tesla's competitors. You can bet they would have attached like leeches to any minor safety flaw. For example, say, a Tesla car caught on fire and its batteries ended up electrocuting a fireman -- there would be no end in sight to the letters…

>Extra effort for increased safety is definitely worth it, if anything at least for marketing purposes. More to the point, traffic deaths are a /real danger/ - more people are killed by falling appliances than by terrorism, and we seem to think it's worth spending huge amounts of money, going to war with the rest of the world, and giving up many of our own rights to fight terrorism. For most of us? Terrorism is not a…

I'd sooner spend the money on preventing night time rage from standing on Lego than on preventing terrorism. So much of the effort is utterly counter productive. I guess ago safety is probably a better use than my suggestion though.
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