Chevy Volt batteries have caught fire. The National Highway Traffic Administration (NHTSA) is investigating, and General Motors has offered to buy Volts back from any owner who fears the electric cars will catch fire.
So does it mean the Chevy Volt is unsafe? The short answer is, no -- Volts won't be spontaneously bursting into flames on our nation's highways. Rather, according to experts we spoke with, the Volt fires prove that automotive engineers have been justified in employing elaborate and expensive cooling systems in their electric vehicles.
Chevy Volt in a side crash test, performed by the Insurance Institute for Highway Safety.
The truth is, there's always been a well-understood fire risk associated with lithium-ion batteries. "The chemistry is edgy," Donald Sadoway, professor of materials chemistry at the Massachusetts Institute of Technology, told Design News in an email. "The electrolyte is an organic liquid that is flammable, highly volatile at even moderately elevated temperature and in the presence of metallic lithium, which can form on the negative electrode at high charging rates."
Elton Cairns, a professor of chemical and biomolecular engineering at the University of California-Berkeley, explains: "In a lithium-ion battery, you've got electrodes that are tens of microns from one another. If you deform the cell case and it causes the electrodes to touch one another, there's an internal short circuit. That can cause the cell to rapidly discharge and, in so doing, heat up."
All of that might sound like a prescription for an epidemic of electric car fires, but it isn't. Why? Because of the aforementioned cooling systems. The Volt employs a fluid coolant that circulates through 1mm-thick channels machined into 144 metal plates that sit between the battery's cells. Using the coolant, the Volt draws the heat away from the core of its big battery.
Similarly, Toyota's Prius PHV, a plug-in hybrid, uses three fans for air circulation, along with ductwork, and 42 sensors to monitor the temperature of its lithium-ion battery. Virtually every manufacturer of production EVs also employs battery management systems and multiple microcontrollers to track the operation of the battery pack at every moment.
Yes, there will be Volt mishaps. It is being sold to the general public. From previous posts I get it that 3 fires occured, two from non-battery events, and one blatant operator error in providing maintenance/repair after a collision. The Ford Pinto/Mercury Molotov was blessed by management to make do without a simple splash shield to keep gas from hitting the hot muffler in a rear-impact collision. A high revving engine, short wheelbase, short overall length equals very hot exhaust pieces. Management ran the numbers and decided that cost of a splash shield was a higher end cost of product than projected liability. Not to be outdone, Chevy had such poor quality control that when Cosworth wanted to hot rod the 1975 Vega, they spent months cherry picking the engine production line to find 2,000 suitable engines to receive the Cosworth hi-po hardware. The Vega engine had the same metalurgy as the Porsches of the day, and a radiator of unsuitable cooling capacity.
I don't totally disagree, but I niether completely agree with your rationality. I mean, true, no tech will ever be perfect, safety is never perfect. That's why they attack the safety of these products, because it is never perfect and uneducated/uninformed people like to use the absense of perfection or the asbsense of 100% certainty as a means of escape. They did the same with the EV-1, now they intend to do the same with the Volt. My intent wasn't to downplay safety concerns with electrics, my intent was to expose the over exageration of these concerns. 3 fires, 2 had nothing to do with the car and the third was in a collision so bad that any insurer would have clasified it as totalled. Now compare that to the gasoline powered car stats stated above and tell me you are honestly concerned about the fire safety of electrics... do you really feel its appropriate to offer a buy back for the Volt over these 3 false fire examples, while not offering the buy back on the gasoline cars which are catching fire consistently every minute and a half across the US?
Look, I'm not trying to downplay safety concerns with eletrics, neither am I trying to hype the safety concerns of gasoline; I feel gas is as safe as it can be, they've done a good job, but it isn't perfect and THOUSANDS stilll die every year in car fires and explosions. When you do an honest comparison, electric is safer hands down. Yes, you have a blast wall for protection in gas cars, but that only is intended to protect from explosion and not fire... electrics cannot explode, but they can catch fire, so there is no need for a blast wall.
It is an unreasonable stretch of sincerity, to be concerned about a battery explosion when you have so much gas out there. I mean really, say I was holding a can of gasoline in one hand and say 100 D size litherium batteries in the other... which would you be more concerned about? I can tell you with 100% certainty that OSHA would be far more concerned about the gasoline, as would I.
I agree that gasoline powered cars are not safe. But your statistics are not relevent. The Volt hasn't been out a full production year, and there are only 0.006 *10^6 of them on the road. This is compared with 255 * 10^6 gasoline powered passenger vehicles. The real statistical comparison is by miles traveled (especially since the Volt has a much smaller range than gas powered vehicles). We don't have the numbers yet to really know.
What we do know is that lithium is inherently dangerous. Not because you can have batteries that short out, but because when they do it's catastrophic (a reaction that feeds on itself). This being an Engineering blog, the conversation should be about what is being done to APPLY the technology safely. If done right, it could be much safer than gas. If done "normally" (read with management involvement, ROI, profit margin, etc.) then I wouldn't let my family near one.
If you want safe and high efficiency, get a diesel. Personally, I have a gas-electric hybrid with NiMH (probably has it's own defects).
Basically it was a design flaw that left the car more susceptible to fire in a rear-end collision. I was read-ended while driving a Pinto. The car was totaled, but no fire.
I don't disagree with all you state, I agree that if done appropriately, electrics will always be safer than a compairable gasoline car. Ultimately, any basic safety analysis would start with a comparison of energy density and volitility, both of which are higher with gasoline right now and probably will continue to be for the next 10 years... though batteries are improving.
Yes, my states aren't 100% comparable, you'd have to reduce everything and make it a per capita comparison. But still, one can look at this data and make a general order of magnitude comparison to draw the conclusions I did. If you disagree with the conclusions, then do the hard math and challenge them.... but I suspect your just challenging my methods and not my conclusions in which case I agree and attribute the problem to laziness.
I do disagree with the claim of "catostrophic failure" of lithum batteries when they fail. Again, an honest attempt at quick comparison, worst case senarios only: When a lithum battery falses, we end up with a short which could catch fire assuming the cooling system fails. When a gasoline tank fails, say in the case of the pino, gas leaks onto a hot surface, igntites, and could potentially ignitude the gas tank (it does happen though rarely) and you get an explosion. An explosion is obviously more dangerous than a fire in most circumstances. I could honestly say that a gasoline powered car could, theoreticaly, be more safer than an electric, but it would require greater isolation than their lithium battery counterparts due to energy density. They could cordin off the gas tank into isolated sections, but to pass the safety rating of electrics, it would have to contain more isolation. Generally, lithum batterys do not fail "catastrophically"... I mean, can you name one catastrophy that has resulted from a lithum battery failure? It all goes back to energy density.
I understand your question. Is there a significant risk to the consumer, like there was with the Pinto? Others appear to have missed the point. It is interesting that there have already been 3 fires, with so few sold. However, the question should not be asked if there is an issue with the Chevy Volt Lithium-Ion batteries but if there is an issue with all electric/hybrid cars with large battery systems. Lithium-ion batteries were not stable enough to be used in consumer products until very recently. Before this, they we would explode above 70 degrees F. Consumers tend to think batteries are benign things - safe. They are energy storage devices and if mistreated can hurt people. They do catch fire and when they do, they burn hot. They also explode and they tend to explode in a cascading fashion.
To me for Chevy to be willing to buy back the vehicles from worried purchasers means that GM is starting to pay attention to customer reaction; after all GM has a reputation of putting vehicles on the road and letting the customer find the bugs for them.
I'd also like to add that many automotive fires have been caused by far lower energy density storage devices, namely the lead acid battery! While the battery itself may have had few ignition issues the vehicle wiring has had plenty. A short in a starter motor solenoid can result in an overheating starter motor and/or its power cable. Fusable links in many instances have not opened on time. With the trend to thinner and thinner wiring to reduce vehicle weight and the talk about raising the bus voltage to 24 or 48 volts to further reduce losses, the peak fault currents will rise even for non electric drive vehicles.
Regardless of the energy source, the density and amount of "fuel" required to power a practical vehicle will always be dangerous. However, it is kinetic energy that poses the biggest threat to a vehicle's inhabitants.
anytime you sit in a vehicle that has enough stored enegery to propel a 4000+ pound object some 300 miles you are taking a risk.
Fortunately gasoline is a fairly safe fuel - its hard to ignite in bulk liquid form, msotly the vapors are extremely volatile.
The lithium is also hazardous, shorts created by physical shocks in abnormal conditions like collisions risk igniting the batteries. Apparently damage to the cooling system can also cause delayed fires - this is particularly worrisome because circulation cooling systems are active whereas all the gas tank protection is primarily passive in nature.
I guess we'll know a little farther down the road.
Manwhile, is it true that GM has only sold 6-10,000 of the very hyped Volts? Are they on track saleswise?
I heard that of 4 Chevrolet Volts involved in crash testing, 3 ended up burning down. 75% suffered total destruction. Of course I'm not sure I believe that, if Chevrolet conducted the crash tests and got those kinds of results then I'm sure they wouldn't have released the car for production.
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