Chevy Volt fires raise question: are electric cars good for the environment AND safe?
Friday, December 2, 2011
The fire, especially when reported in those words, has caused concern not just for Volt owners but for electric car advocates in general, raising fears that “green,” petroleum-free transportation options might come with safety concerns.
However, the account given in the first sentence is an incomplete summation of the story. The Volt involved in the side-impact crash did catch fire–three weeks later, when it was in storage. The 400-pound battery pack was damaged in the crash and the coolant line was ruptured. In the meantime, the car’s lithium-ion battery was never “de-energized,” as is the protocol when an electric car is involved in a crash.
NHTSA went on to do more tests on Volts last month in which batteries were intentionally damaged and the coolant line intentionally ruptured. In the first test, there was no fire. In the second test, the battery caught fire a week later. In the third test, the battery “began to smoke and emit sparks,” according to NHTSA, a few hours after impact and shortly after the battery was turned upside down. (The rotation was meant to simulate a vehicle rollover after a crash.)
According to NHTSA’s statement:
NHTSA is not aware of any roadway crashes that have resulted in battery-related fires in Chevy Volts or other vehicles powered by lithium-ion batteries. However, the agency is concerned that damage to the Volt’s batteries as part of three tests that are explicitly designed to replicate real-world crash scenarios have resulted in fire. NHTSA is therefore opening a safety defect investigation of Chevy Volts, which could experience a battery-related fire following a crash. [emphasis added] Chevy Volt owners whose vehicles have not been in a serious crash do not have reason for concern.
General Motors responded by offering to buy back any Volts from concerned owners or provide loaner cars until the problem is identified and said it will recall and repair the vehicles once the cause of the fires is determined. GM chairman and CEO Dan Akerson told Reuters the company will look into whether it needs to redesign the battery.
So how much should electric vehicle owners, or those considering an electric car, be worried?
“This is not to say we don’t need to fully understand why the battery packs eventually caught fire, but preliminary information [on the NHTSA fires] clearly shows GM’s published safety protocols were not followed,” said Paul Scott. “The resultant thermal incidents clearly would not have happened if the battery packs had been disconnected and drained of energy after the crash.”
Scott is a co-founder of the electric-car advocacy group Plug In America and also sells an electric car, the Nissan Leaf, at Nissan of Downtown Los Angeles. (The Volt is a plug-in hybrid electric vehicle, has a small gasoline generator that powers the car after about 35 miles of operating with the electric battery, and its battery has what is known as an active cooling system, using fluid. The Leaf is an all-electric car that uses what’s known as a passive cooling system, with an air-cooled battery.)
Scott says the risk of fire is far greater in vehicles with internal combustion engines [ICE]. “NHTSA rules, and all of the automakers’ protocols, call for the draining of gas tanks after a major crash and before storage,” he said. “Just imagine how many fires we’d have if those rules were not obeyed. As it is, ICE vehicles are responsible for around 200,000 fires every year. Hundreds die and thousands are injured. We’ve become inured to these tragedies.
“I’ll bet if you were to ask firefighters and first responders who go to crash scenes if they would rather go to crashes involving gas cars or electric cars, I can almost guarantee you they would say, give me an electric car any time. Once you’ve punctured a gas tank, that stuff is bad, and sparks are everywhere.”
“If you have a combustion engine with a gasoline tank, first responders generally come in and drain that tank and disconnect the 12-volt battery that starts the car,” GM’s Akerson told Reuters. “In a Volt, we have protocols that you come in and drain the battery, because the battery is like a gas tank, it’s a reservoir of energy.”
No fires, either in crash test or real-world situations, have been reported with the Leaf. Energized lithium combined with the Volt’s cooling fluid is being considered as a possible cause of the Volt fires, but the Leaf battery has no cooling fluid.
In an article in Scientific American last year, writer Mark Fischetti mentioned that some early lithium-ion power packs in laptop computers caught fire.
The usual cause was thermal runaway, a chemical reaction that could start from excessive overheating, then potentially cause a cell to catch fire or explode. Although even extreme driving conditions are unlikely to trigger those problems, a crash could, and so could a sudden overcharge—for example, if lightning struck a charging port while a car was being recharged.
Fischetti quoted Chris Orendorff of the Battery Abuse Testing Laboratory at Sandia National Laboratories in Albuquerque as saying, while lithium-ion batteries may have a higher chance of catching fire than standard lead-acid batteries, “the chances of flammability are far less than what you have in a combustion vehicle that is carrying 15 gallons of gasoline onboard.”
“We basically have grandfathered these risk factors [with fossil fuels]. Gasoline catches on fire all the time,” said Denholm. Electrical energy storage systems aren’t inherently riskier than petroleum or natural gas, according to Denholm, but their risks are different.
And manufacturers take those risks into account in designing electric cars. According to John O’Dell, who reports on alternative vehicles such as electric cars as a senior editor of Edmunds AutoObserver.com, “automakers use multiple safety systems in their EV [electric vehicle] battery packs to safeguard against heat build-up and other ‘thermal incidents’ that could lead to EV battery fires.”
At least one observer is less than reassured by the direction NHTSA is taking in looking into the cause of the Volt fires. Sean Kane of Safety Research & Strategies, an organization that monitors vehicle and product safety, wrote on his blog that the investigation “is already hitting a few troubling notes”:
One would expect that this high-profile and technically specific investigation would require an investigator with lots of experience in hybrid electric vehicle systems and design – or at a minimum with an electrical engineering background. Instead, the lead investigator in this sensitive investigation is a mechanical engineer fresh out of college with no apparent electrical engineering background or experience. She joined the agency one month before the Volt ignited.
More than 6,000 Volts have been purchased since the vehicle went on the market in January, while Nissan has sold nearly 9,000 Leafs since that vehicle was launched last year.
UPDATE 12/7/11: Associated Press auto writer Tom Krisher reports the fluid that cools the Volt’s batteries has been identified as the likely cause of the fires.