Following a fire in a Chevy Volt battery pack that had been damaged in a National Highway Traffic Safety Administration crash test, NHTSA recently performed additional impact tests on Volt battery packs to simulate that incident. Two of the three batteries that were tested experienced what the agency calls “thermal events”, including fire. As a result, NHTSA has now opened a formal investigation into potential risks from “intrusion damage” in Volt batteries. It should be pointed out that the tests involved a very specific sequences of events. The original crash test was a 20 mph side pole impact test, followed by a post impact rollover. Chevy Volts have a sophisticated battery conditioning and temperature management system that involves liquid cooling. In the crash test the Volt battery case was penetrated and a battery coolant line was cut. Three weeks later, while the wrecked Volt was sitting in a storage lot, its battery caught fire, burning the Volt and nearby vehicles. GM now says that their own procedure in the event of a serious collision is to drain the battery’s electrical charge. That information was not shared with NHTSA and the burned Volt’s battery had not been discharged.