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LetoAtreidesII
User Rank
Platinum
Re: Battery torn apart in accident?
LetoAtreidesII   9/4/2013 12:50:21 PM
The problem with the battery pack damage is that Lithium is hughly reactive.  When a battery pack of EV size ruptures the cell can go into an overheated runaway state and basically melt down, catch fire, off gas some pretty nasty stuff.

One of the scariest parts about this is it does not need to happed right after an crash.  If the casing is cracked their can be a slow reactive build up that can take minutes, hour up to days and than boom you have battery thermal runaway.

This problem is being worked on and will eventually be solved their are new battery chemistry and assembly systems that prevent this but most current EV battery packs have this problem.  Is it worse than a gas tank rupture??  Like all else it depends but it is one of the often not discussed issue with EV vechiles.

 

Tool_maker
User Rank
Platinum
Re: Let's think about this for a second
Tool_maker   9/4/2013 12:47:08 PM
NO RATINGS
  Just curious. How many times have you been involved in an auto accident where you slam int a stationary object? How does the Tesla do when it is t-boned by another Tesla? A Camry? A BMW? A Ford F-150?

  Those are not tests. They are everyday occurences.

tluxon
User Rank
Gold
Battery torn apart in accident?
tluxon   9/4/2013 12:38:18 PM
NO RATINGS
Hmmm - most accidents I've witnessed involving internal combustion powered vehicles do not involve fire or explosions.  Considering how many such vehicles are on the road, I believe they have a pretty fair track record when it comes to detonations.

I understand the water and high voltage danger, but I'm curious as to what kind of risks are at play in the event the Tesla's battery block were to be torn apart in an accident.

irishmuse
User Rank
Gold
Re: Let's think about this for a second
irishmuse   9/4/2013 11:23:02 AM
NO RATINGS
Yes, Tesla has done a great job.  HOWEVER, let's not forget that this is a REALLY expensive automobile with lots of functional shortcomings.  Let's see how they do on a true 4 passenger vehicle with a 400 mile range for $15,000 delivered.

szyhxc
User Rank
Iron
Re: Electrical Crashes
szyhxc   9/4/2013 11:18:52 AM
NO RATINGS
The jury is still out.  We have not had enough EVs involved in accidents in wet weather conditions to tell.  I pray for the first responders who encounter wet metal, crushed into a 300 VDC battery.  Occupants likewise must be very careful steping onto wet ground from a similarly damaged vehicle.

bob from maine
User Rank
Platinum
Re: Let's think about this for a second
bob from maine   9/4/2013 10:43:21 AM
NO RATINGS
I congratulate Tesla on doing so well in the NHTSA crash tests. The tests are carefully designed to try to predict surivivabilty of the occupants in a crast situation of fairly limited scope. Controlled crumple zones reduce the perceived g-forces seen by the occupants; these crumple zones are the result of a great deal of analysis of materials, fastentings and assemblies. A 5 star sweep of all tests indicates some very thorough engineering design and a good understanding of composite materials. The Tesla S is designed to fit a small market nitche and it does that very well. It is not a 'peoples' car but the people who can afford to buy it are enriching their own lives as well as allowing Tesla to continue to further the science of EVs. It is one step on a long road - imagine what our greaet grand children will be using for transportation - this vehicle and others like it are proving - or disproving - the viability of EVs and composite technology. Wish I could justify one. Attaboy Tesla! Nice article Charles.

fauxscot
User Rank
Silver
Re: Another Misleading article on EV's
fauxscot   9/4/2013 10:06:06 AM
NO RATINGS
Those are good points.

I particularly like the one that we can't imagine what the real world shortcomings and risks are until we get some substantial experience with the tech.  It's a chicken or egg problem, though.  Looks like we chose one and now, we'll see what happens in a few years of highway experience.

Tesla is forcing the issue. For good or bad, they are filling up the sample pool.  Most things in life and engineering trade off something or other for something else.   If this is like anything else I've seen, worst case we'll probably see a change in the character of risks, and best case we MAY see an overall decrease in risks. 

The one fly in the ointment is economics.  If we put $70,000 into a Yugo, I'm betting it could be made pretty safe.  But the market would not tolerate it.   The chief benefit of the Tesla is that it is clearing SOME of the blockages that have been chorused for a long time.... people won't buy it.... you can't recharge it.... it won't go 1000 miles...  who will maintain it.....   batteries are heavy and unreliable.... 

I'm impressed anyone can build a car (that isn't a dune buggy!) and steal business away from Ford, GM, BMW, and Mercedes. 

LetoAtreidesII
User Rank
Platinum
Re: Another Misleading article on EV's
LetoAtreidesII   9/4/2013 9:57:10 AM
NO RATINGS
George,

Good points about the fire issue.  As always test results are only as good as the test.

To all who think I hate EV's I do not, I currently use an E-mower and E-chainsaw, E-weedeater (i hate small gas engines).  and when I can afford a spare vechile I would love to make an EV-Jeep.  As an EE engineer I love to mess with E-stuff.  It just burns me when people attempt to push their case with false or skewed data.

EV should stand on the own X-batteries with the pros and cons clearly marked.

Watashi
User Rank
Platinum
Let's think about this for a second
Watashi   9/4/2013 9:52:54 AM
NO RATINGS
Going point-by-point:

Rollover was a, mostly overblown, concern with Jeeps and SUVs.  Tesla is designed from the ground up as a sports car.  Sports cars always have a low center of gravity to enable faster cornering.  Although I will give a slight nod that if designed right, EVs have the inherent ability to always have a low CG.

"So the shock wave is pretty much transferred to the area directly behind the engine, with minimal energy absorption." – This is just nonsense.  The engine block is not rigidly fixed to the frame of the car so no 'shock wave' can transmit through it.  It also has something called mass.  The mass of the engine will help work against the momentum of the impact.  The engine block will either shear its mounts or cause the frame to bend absorbing energy.  It also gets pushed into the firewall in a crash which will absorb more energy and prevent it from entering the passenger cabin.  This just sounds like propaganda; knowing one of the biggest EV weaknesses is actually survivability.

"You don't have a highly volatile liquid onboard, which can quickly get away from you during a crash and become a real problem." – This is a fair comment.  But let's not forget that EVs have been burning up all over the place due to shorting of the high energy storage.  In my mind this is a wash between the two if EV electrical systems designed with collision survivability in mind.  Gas burns when it finds heat and air; high current can melt, heat or burn any material.  Gas can explode, but in car wrecks it just burns.  Batteries can explode, but not very impressively.

All in all I say a score of one to Tesla (not all EVs) and minus two for David Cole.

GeorgeG
User Rank
Platinum
Re: Another Misleading article on EV's
GeorgeG   9/4/2013 9:49:01 AM
NO RATINGS
More importantly, you can't test quality in. When it comes to safety, you have to begin early in design to design safety in. In a complex system it is unlikely that all of the potential safety challenges can be thoroughly tested for in any practical amount of time. Also, as has been commented, one tends to test for what one imagines to be the most important challenges while real life has a way of creating challenges that can only be imagined after the fact. And your mileage may vary. It is practicaly impossible to obtain statistically valid samples of most safety concerns.

Looking at the stats for vehicular fatalities, a disturbing proportion of them are due to fire with a significant portion of those not the result of a collision or other accident. Yet, safety testing does not dwell on the involvement of fire; in fact, they usually put any fire out before it plays out (crash test dummies and instruments are expensive). Human factors also play an important part since about 1/3 of fire fatalities occur when persons attempt to extinguish the fire. Gasoline burns and in a broad range of conditions explodes. Part of the problem is that this is common knowledge so it goes under-examined with respect to vehicle safety. They test TV recliners to see how rapidly they become consumed by flame but not vehicles.   

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