Disconnecting the main battery is a common sense procedure for worker safety when repairing a collision damaged electric vehicle. But, discharging the battery, even though it is disconnected, can be just as important for repair facilities that may have one of these vehicles inside their shop.

The National Highway Traffic Safety Administration is investigating the cause of a fire in a Chevrolet Volt that burst into flames three weeks after its lithium-ion battery was damaged in a government crash test. According to a report in the Associated Press over the weekend, the car that caught fire was crash tested in May and three weeks later, while the car was parked at the test facility, it caught fire and set several nearby vehicles on fire.

According to the AP report, the crash test facility did not follow GM's procedure of discharging the battery after a crash and a coolant leak may have caused a short in the still-charged battery leading to the fire.

The Lithium-ion batteries used in the Volt are similar to those used in laptop computers and other consumer devices, which also have a history of sometimes catching fire when damaged. For this reason, airlines no longer allow these types of batteries to be included in checked-baggage.

"NHTSA is focused on identifying the best ways to ensure that consumers and emergency responders are aware of any risks they may encounter in electric vehicles in post-crash situations," NHTSA said in a statement. "Ultimately, we hope the information we gather will lay the groundwork for detailed guidance for first-responders and tow truck operators for use in their work responding to incidents involving these vehicles.

The AP report said that the NHTSA investigation is not questioning the safety of the Volt, but the agency is investigating how to handle the vehicles longer-term, for the safety of tow truck drivers, salvage yards and body shops. The agency recommends against storing a severely damaged electric vehicle inside a garage or near other vehicles.

Jim Federico, General Motors chief engineer for electric vehicles, said in a separate statement relating to the NHTSA investigation, "Safety protocols for electric vehicles are clearly an industry concern. At GM, we have safety protocols to depower the battery of an electric vehicle after a significant crash. We are working with other vehicle manufacturers, first responders, tow truck operators, and salvage associations with the goal of implementing industry-wide protocols."