DETROIT — Federal safety regulators on Friday said they have begun a formal defect investigation of the Chevrolet Volt because a second battery caught fire after a crash simulation.
The regulators have been examining batteries in several plug-in cars since a June fire involving a Volt that had been heavily damaged in a government crash test.
On Thursday, a Volt battery pack that was intentionally damaged Nov. 17 as part of that testing caught fire, the National Highway Traffic Safety Administration said. The agency also recorded a temporary temperature increase in another battery pack one day after it was damaged, and a third pack “began to smoke and emit sparks” after it was damaged and then turned upside down to simulate a rollover crash.
“N.H.T.S.A. 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,” it said in a statement. “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.”
The N.H.T.S.A. said its battery testing had not raised any safety concerns about the batteries in other plug-in cars and that “Chevy Volt owners whose vehicles have not been in a serious crash do not have reason for concern.”
General Motors, which began selling the Volt about a year ago, said in a statement that it was not surprised by the investigation, but insisted that the car was not defective. It has been working closely with the agency to try to replicate the June fire, which was first disclosed publicly this month, and neither had experienced any similar incidents until last week’s tests.
“The Volt is safe and does not present undue risk as part of normal operation or immediately after a severe crash,” Jim Federico, G.M.’s chief engineer for electric vehicles, said in the statement. “G.M. and the agency’s focus and research continues to be on battery performance, handling, storage and disposal after a crash or other significant event, like a fire, to better serve first and secondary responders. There have been no reports of comparable incidences in the field.”
G.M. attributed the June fire, which occurred at a storage facility three weeks after the car was crash-tested, to a failure to deactivate the battery. In July, it began publicizing postcrash safety protocols to emergency personnel that call for the battery to be isolated from the rest of the car via a disconnect switch and then depleted by the company.
The company says it believes the June fire was a result of crystallized coolant that leaked out of the battery’s cooling system and pooled on another portion of the pack when it was rotated as part of the crash test, a G.M. spokesman, Rob Peterson, said in an interview last week.
The N.H.T.S.A. said the testing last week that resulted in the more recent fire included damaging the battery compartment and rupturing the coolant line.
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