In May, NHTSA performed a New Car Assessment Program (NCAP) side pole impact test, followed by a post-impact rollover test on a Chevrolet Volt. In connection with that testing, NHTSA identified the potential for intrusion damage to the battery which may result in a substantial thermal reaction and fire. Twenty-one days after the 12 May 2011 testing, delayed thermal heating and pressure release resulted in a fire that consumed the Chevrolet Volt and three other vehicles in close proximity at the test facility.

At that time, said Mary Barra, GM Senior Vice President, Global Product Development, GM had yet to implement a battery de-powering procedure in the wake of a severe crash; i.e., the pack remained powered. GM subsequently developed a process to de-power the Volt battery after a severe crash, which it has been using since July, Barra said. GM has shared the process with NHTSA, and is working to extend the process and technology.

The current de-powering process begins when GM is notified of a Volt crash through OnStar. GM assesses the location of the vehicle, and then dispatches GM employees to the Volt by whatever means necessary, said Micky Bly, GM Executive Director, Global Electrical Systems, Hybrids, Electric Vehicles and Batteries. The GM team reaches the car, hooks up a unit and drains the battery.

During the week of 14 November, NHTSA performed follow-up tests on battery packs—not full vehicles—to simulate the incident, intentionally damaging the battery compartment and rupturing the vehicle’s coolant line. Although this testing occurred after GM had begun implementing the de-powering procedure for real-life incidents, the packs under test remained powered to reproduce the conditions form the May event, Barra said.

Following a test on 16 November that did not result in a fire, a temporary increase in temperature was recorded in a test on 17 November. During the test conducted on 18 November using similar protocols, the battery pack was rotated within hours after it was impacted and began to smoke and emit sparks shortly after rotation to 180 degrees. NHTSA and GM are continuing the forensic analysis of the 18 November fire incident.

On Thursday (24 November), the battery pack that was tested on 17 November and that had been continually monitored since the test caught fire at the testing facility. The agency is currently working with DOE, DOD, and GM to assess the cause and implications of Thursday’s fire.

In each of the battery tests conducted in the past two weeks, the Volt’s battery was impacted and rotated to simulate a real-world, side-impact collision into a narrow object such as a tree or a pole followed by a rollover.

Barra said that although the engineering investigation as the the precise cause of the fire was ongoing, GM believes that it is the electronics within the battery, not the chemistry of the battery.

During the conference call, Barra said GM had established a senior engineering team to develop changes to eliminate concern of potential post-crash electrical fires and work with industry to ensure appropriate electric vehicle protocols were in place. Barra said such electrical fires had not occurred on public roads and NHTSA was not investigating any such potential imminent failure on the roads.

GM and the agency’s focus and research continue to be on the performance, handling, storage and disposal of batteries after a crash or other significant event. We’re working with NHTSA so we all have an understanding about these risks and how they can be avoided in the future. This isn’t just a Volt issue. We’re already leading a joint electric vehicle activity with Society of Automotive Engineers and other automotive companies to address new issues, such as this protocol of de-powering batteries after a severe crash.

—Mary Barra

Barra said the team would continue to work closely with NHTSA, suppliers, dealers and manufacturing teams to initiate any necessary changes as soon as possible.

Mark Reuss, president, GM North America, said the company would take every precaution to assure the driving public of GM’s commitment to the safety of the Volt being handled after a severe incident and the total satisfaction of everyone who owned one.

GM is establishing a Volt owner satisfaction program. Any Volt owner concerned about safety can contact his or her Volt advisor to arrange for a free GM vehicle loan until resolution of the issue.