We know that GM is intent on defusing the firestorm that erupted at the beginning of November with disclosure that a Chevy Volt battery pack had burst into fire last May. Today GM's Mary Barra and Mark Reuss held a press conference to explain battery pack modifications the company has developed.
During the press conference Mary Barra explained the failure mode analysis of the Chevy Volt which underwent extreme side impact crash testing last May, catching fire three weeks later. It was determined the failure mode begins with a side impact causing "a minor intrusion" of "a portion of the vehicle" into the battery pack, causing a leak of one-quarter cup of coolant. The NHTSA procedure is to then rotate the crashed vehicle in a "slow roll" taking twenty minutes total for each complete rotation of the vehicle. During the slow roll, when the crashed vehicle was upside down, a liter (over four cups) more coolant leaked out, and spilled onto circuit boards contained inside the battery pack container. After three weeks this condition of coolant spilled onto circuit boards led to the battery pack fire, in part (GM says) because the battery was still charged up.
The battery pack modifications entail these steps:
- Strengthen the Volt's safety structures and battery pack containment to protect the battery pack in side impact collisions
- Add sensors to the coolant reservoir to monitor coolant levels
- Add a bracket to prevent overfilling the coolant reservoir
GM will conduct what's called a "Customer Satisfaction Program" to install these modifications in the Chevy Volt fleet, at GM's expense. This sort of program is essentially a recall, but is not conducted through the NHTSA and does not have the full stature of a recall. Volt owners have begun receiving registered letters from GM explaining the findings and the process for having modifications installed in their cars.
During the press conference GM's Barra stressed that the battery cells were not the cause of the fire. They do not plan to change anything in the battery pack manufacturing, because they're confident of the testing they'd performed on the cells. At the time GM chose LG Chem as the cell supplier, LG Chem described these cells as a very safe lithium ion chemistry, and GM says they put the cells through a laundry list of torture tests.
In other words, GM's engineering team believes their thorough testing of the cells demonstrates the cells are safe, and that the culprit is coolant leaking onto circuit boards. The fixes they've developed reduce the risk of coolant leakage.
The modifications were developed in response to the NHTSA Preliminary Evaluation in the investigation of the battery pack fires in 2011. There was one fire in May 2011 occuring 3 weeks following an extreme side impact crash test, then in November there were two more fires following an NHTSA test meant to reproduce a coolant leak observed with the original fire.
GM's Mark Reuss revealed during the press conference that 250 Volt owners had requested either a loaner car, or that GM buy back their Volt's. That's 250 Volt owners out of the nearly 8000 Volt's which were sold in 2011, who were scared enough to take action. Other Volt owners showed they were not scared, with several hundred signing an open letter to GM reaffirming their support for the company and their love of the Volt. Additionally sales Chevy Volt volume grew significantly during November and December, despite all the fearism being perpetrated through the news media.
The NHTSA investigation is not finished, and the agency is "continuing to gather and assess information on the post-crash fire risk in these vehicles." The investigation includes representatives from NHTSA, GM and the Energy Department, and from preliminary results "it appears that both battery intrusion and coolant leakage must be present to enable post-crash fire in the Volt."
Both the NHTSA and GM have conducted multiple crash tests during December using Chevy Volts on which the modifications have been installed. The NHTSA test occurred on December 22, and the crashed Volt has been monitored since with no indication of either coolant leakage, intrusion into the battery pack, or a fire.
The NHTSA expects to conclude their investigation "in the coming weeks" (which doesn't give us much hint how much longer the investigation will take) and plans to share results with "consumers, the emergency response community, and tow truck operators and storage facility managers".
“These enhancements and modifications will address the concerns raised by the severe crash tests,” Mary Barra, GM senior vice president of Global Product Development said. “There are no changes to the Volt battery pack or cell chemistry as a result of these actions. We have tested the Volt’s battery system for more than 285,000 hours, or 25 years, of operation. We’re as confident as ever that the cell design is among the safest on the market.”
“We’re focused on one thing right now: doing what’s right by our customers,” said GM North America President Mark Reuss. “We’ll live up to our commitment to make sure our customers are delighted with their purchase.”
See:
GM Announces Enhancements to Chevrolet Volt
$250k Chevy Volt subsidy claim bogus says TheStreet.com
Are the Chevy Volt or Nissan Leaf flops as some naysayers claim?
Overhyped bashing of electric car charging station subsidies in the Washington Post
Nissan's Leaf survived fine in Fukushima tsunami, no fires
GM to use different battery technology in Spark EV than the Volt
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