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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

#281

Post by moocowduckquack »

sliverstorm wrote: post #272
moocowduckquack wrote: post #261

Earlier quoted context omitted.

85 kWh of potential energy sitting under the car... A 40 litre petrol tank holds about 380 kWh though.

A 40 liter petrol tank can't discharge 85kWh of potential energy in seconds without ideal conditions (good vaporization or atomization combined with sufficient oxygen)

Neither can a battery. The internal resistance is too high. They can cook and go on fire a bit, but much less than a gasoline fire, but they cannot shock you with their entire capacity in a few seconds.

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

#283

Post by moocowduckquack »

JshWright wrote: post #278
moocowduckquack wrote: post #261

Earlier quoted context omitted.

85 kWh of potential energy sitting under the car... A 40 litre petrol tank holds about 380 kWh though.

Yeah, but we've had almost a century of experience dealing with that... The issues involved are also very different. A tank of gas is actually a very stable thing. Barring a puncture, there's not much you can do to a gas tank to make it do bad things. Cutting a gas line is no major concern. Shorting a high voltage/high current power line to the frame of the vehicle is putting a lot of trust in the batteries failsafes…

As far as I can tell, unless people have done something stupid, your worst worry is not the shock from the batteries. The batteries are a variety of potential difference spread over a large area and will go on fire rather then discharge everything at once, which is an issue, but they will not explode with their total chemical potential, not even close. It is any big fat capacitors that you have to worry about. Now they are not storing anywhere near the capacity of the battery, but they can let it out with very low internal resistance and after heavy braking are likely to be fully charged. So it is a current that can be easily discharged, but you have to know it is there.

edit - I said it earlier somewhere else, but EMT gloves with built in glowy multimeters might be a really good plan.

double edit - if you think this is a good plan, feel free to nick it.

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

#284

Post by X-Istence »

The way cars collapse and fall apart at crashes is absolutely amazing. Just over 30 days ago I was involved in a head on collision with a Nissan Titan full-size pickup truck WITH cargo in the bed, and walked away from an accident the EMT's, fire fighters, and police all told me it was almost impossible I did. The adjuster didn't believe me when I told him the state of the car, but when he did go out to check it out he called me and asked me if I was sure I was alright...

Here are pictures: http://imgur.com/a/nIMOP#0

I was driving 20 Mph, turning left at a traffic light, the pickup truck was driving (according to the driver) 45 - 50 Mph, although the adjuster and off-duty police suggest he may have been driving faster.

---

One thing I will note though, my car is significantly cheaper than the Tesla... and fares extremely well in the NHTSA tests.

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

#285

Post by X-Istence »

dredmorbius wrote: post #121
stevewilber wrote: post #78

Earlier quoted context omitted.

First: SUVs don't survive crashes particularly well This is outdated information, SUVs are now far safer than cars. Death rate (per 1M vehicle years) for 4WD midsize SUV: 23. Midsize Sedan: 51 [1] [1] http://www.iihs.org/externaldata/srdata/docs/sr4605.pdf

Interesting. The change is almost totally attributable to ESC (electronic stability control), which directly addresses SUV's Achilles' heel. It's also interesting to note the variability in results -- the Audi A6 is one of the safest luxury vehicles (I suspect the Tesla S will change that), and the Honda Accord is remarkably safe for a mid-sized sedan (though the Civic doesn't do as well relative to its class). It's…

I got hit by a Nissan Titan: http://imgur.com/a/nIMOP#0

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

#286

Post by chongli »

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…

While that's true, I don't think it's what the parent meant. Colloquially, when we say to boil water we don't mean until the vessel is dry, just until a roiling boil is reached (this is typically how we cook pasta).

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

#287

Post by toast0 »

agumonkey wrote: post #196
gambiting wrote: post #190

Earlier quoted context omitted.

Most cars automatically shut down fuel supply to the engine when a collision is detected. Even if it's just a minor hit the engine can't be started again without clearing the collision warning from the computer.

Thanks, now I wish to know more about the protocols and checks in car controllers.

Shut down fuel supply is code for turn off the fuel pump.

This can be done all mechanically, scroll down on this page to see a deconstructed inertia switch. http://www.therangerstation.com/tech_library/InertiaSwitch.h...

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

#288

Post by jccooper »

gargoiler00 wrote: post #256
lutusp wrote: post #247

Earlier quoted context omitted.

> What does that mean for the user. Do batteries today last twice what they lasted 30 years ago? Nope. Are rechargeable batteries any more viable today? Nope. You are flat wrong on both counts. Modern batteries provide much more energy per size, weight and cost than their rechargeable predecessors. As to "viable", how can you make any kind of claim about batteries that didn't exist 30 years ago? > Even batteries in l…

My first laptop was an Amstrad PPC512 in the mid 80s - almost 30 years ago. I'm still not convinced batteries have come that far since then. I'm actually thinking of going back to my nokia which has a battery that lasts a week on standby. Compared to modern smartphones which last a day. You're right though - Inefficient bloated buggy software is becoming the driving force for requiring more power from batteries - goi…

"I don't want software running my car."

Too late. Every car since about 1993 is entirely reliant on electronic computers, and many were even in 1980. Most of them reprogrammable, though usually cumbersome to do so.

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

#289

Post by jccooper »

gargoiler00 wrote: post #256
lutusp wrote: post #247

Earlier quoted context omitted.

> What does that mean for the user. Do batteries today last twice what they lasted 30 years ago? Nope. Are rechargeable batteries any more viable today? Nope. You are flat wrong on both counts. Modern batteries provide much more energy per size, weight and cost than their rechargeable predecessors. As to "viable", how can you make any kind of claim about batteries that didn't exist 30 years ago? > Even batteries in l…

My first laptop was an Amstrad PPC512 in the mid 80s - almost 30 years ago. I'm still not convinced batteries have come that far since then. I'm actually thinking of going back to my nokia which has a battery that lasts a week on standby. Compared to modern smartphones which last a day. You're right though - Inefficient bloated buggy software is becoming the driving force for requiring more power from batteries - goi…

"I don't want software running my car."

Too late. Every car since about 1993 is entirely reliant on electronic computers--and many were much earlier. Most of them reprogrammable, though usually cumbersome to do so. Changing software during service is common these days--and the dealer may not even bother to mention it.

Tesla's use of software is pretty normal. Go sit in BMW 5 series, or a Ford Focus. All soft interface. Tesla's is just nicer, and not afraid of taking advantage of the fact that everything is software already.

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

#290

Post by dredmorbius »

X-Istence wrote: post #285
dredmorbius wrote: post #121

Earlier quoted context omitted.

Interesting. The change is almost totally attributable to ESC (electronic stability control), which directly addresses SUV's Achilles' heel. It's also interesting to note the variability in results -- the Audi A6 is one of the safest luxury vehicles (I suspect the Tesla S will change that), and the Honda Accord is remarkably safe for a mid-sized sedan (though the Civic doesn't do as well relative to its class). It's…

I got hit by a Nissan Titan: http://imgur.com/a/nIMOP#0

I can't get over how intact the interior is. Any injuries to you?

What were the crash parameters? Speeds? Head-on? (Looks like it).

Your car was a Subaru something or other?

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