US: GM makes Volt changes after NHTSA probe
GM has made changes to Volt structure and battery cooling after NHTSA voiced concerns
General Motors has changed the vehicle structure and battery coolant system in the Chevrolet Volt range extender hybrid which, it said, would further protect the battery from the possibility of an electrical fire occurring days or weeks after a severe crash.
The improvments came after a National Highway Traffic Safety Administration (NHTSA) preliminary evaluation to examine post-severe crash battery performance.
The US government agency began its evaluation on 25 November following a severe-impact lab test on a battery pack that resulted in an electrical fire six days later. The test was conducted to reproduce a coolant leak that occurred in a full-scale vehicle crash test last May that resulted in an electrical fire three weeks later.
GM noted that the Volt is a 'top safety pick' by the Insurance Institute for Highway Safety and has earned other safety awards from third-party organisations. In the first 11 months of 2011, Volt owners accumulated nearly 20m miles without an incident similar to the results in the NHTSA tests.
“The Volt has always been safe to drive. Now, we will go the extra mile to ensure our customers’ peace of mind in the days and weeks following a severe crash,” said Mary Barra, GM's head of global product development.
What GM calls a "customer satisfaction programme' - modifying existing customers' cars to further protect the battery from the possibility of an electrical fire occurring days or weeks after a severe side crash will strengthen an existing portion of the vehicle safety structure to further protect the battery pack in a severe side collision; add a sensor in the reservoir of the battery coolant system to monitor coolant levels and add a tamper-resistant bracket to the top of the battery coolant reservoir to help prevent potential coolant overfill.
GM said it conducted four successful crash tests last month of cars with the structural change which performed as intended.
"There was no intrusion into the battery pack and no coolant leakage in any of the tests," it said.
“These enhancements and modifications will address the concerns raised by the severe crash tests,” Barra 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.”
Current owners will be notified individually when the modifications are available for their vehicles. Changes will be made to new cars when production resumes this month.