NHTSA launches safety investigation following Chevrolet Volt battery fires

Following an incident with a Chevrolet Volt catching fire after being crash tested, the National Highway Traffic Safety Administration (NHTSA) has launched a safety investigation into the plug-in hybrid sedans. And General Motors has announced it will offer free loaner cars to any Volt drivers who are concerned about the risk. (Download the letter that GM has prepared for Volt owners.)

The fire resulted after NHTSA evaluated the Volt in a side-impact pole test in July that damaged the battery pack, as well as the battery's coolant lines. Then the car was rotated 360 degrees to simulate a rollover in a real-world crash. Three weeks later, the fire erupted when the car was parked next to other vehicles at the crash-test facility.

While the agency states that it is unaware of any crashes of Volt's on public roads that have resulted in fires, NHTSA did conduct three followup crash tests two weeks ago, trying to duplicate the fire. In the third test, the Volt also caught fire. Last week, the Volt involved in the second followup test also caught fire. NHTSA is conducting its own investigation into the causes of these fires.

A defect investigation, such as the one NHTSA announced Friday, is the prerequisite to a mandatory safety recall.

General Motors has said that in the July test NHTSA did not follow GM's procedure in draining the batteries after the accident. The company is now training tow truck drivers and body shop operators, as well as junk yard workers, to do so. It remains unclear whether NHTSA drained the batteries in the Volts subsequently tested, as they had not returned calls by the time we published.

NHTSA says Volt drivers should take the same precautions following an accident that they would in a traditional gasoline-fueled car: Exit the vehicle if possible, move a safe distance away, and call 9-1-1.

The question NHTSA's investigation will address is not whether electric cars are safe, but whether they are as safe as gas-powered cars. From a fire-safety standpoint, the main difference seems to be that gasoline requires a spark to ignite, and when it does the conflagration is thorough and immediate. Batteries can supply their own sparks, but they're less likely to ignite immediately or burn as quickly. So the key question is how much time the batteries would allow emergency responders to arrive, remove passengers, clean up the accident scene, and drain the batteries before a fire could likely erupt. Whether draining the batteries is an effective remedy is another question.

Complicating both questions is the fact that plug-in hybrids, such as the Volt, also carry a gas tank, which such an electrical fire could ignite.

NHTSA says its testing of electric cars other than the Volt has not raised such safety concerns.

Related:
Chevrolet Volt road test
Video: Chevrolet Volt crash test by the IIHS

—Eric Evarts