Safety of lithium-ion batteries plug-in electric vehicles

     Federal auto-safety regulators are scrutinizing the safety of lithium-ion batteries that power all plug-in electric vehicles after a General Motors Chevrolet Volt caught fire, people familiar with the probe said. The regulators have asked automakers, including GM, Nissan and Ford, that sell or have plans to sell vehicles with lithium-ion batteries about the batteries' fire risk, four people familiar with the inquiry said. The Volt caught fire while parked at a National Highway Traffic Safety Administration testing center in Wisconsin, three weeks after a side-impact crash test May 12, said an agency official. A plug-in Prius and an electric version of the RAV4 sport-utility vehicle will use lithium batteries.

Seoul-based LG Chem, South Korea's biggest chemical maker, supplies Volt batteries. In June, GM and NHTSA both crashed a Volt and could not replicate the May fire, Martin said. GM has safety procedures for handling the Volt and its battery after an accident. "There are safety protocols for conventional cars," Martin said. Lithium batteries could catch on fire if the battery case and some of the internal cells that store electricity are pierced by steel or another ferrous metal, he said.

"The Nissan Leaf battery pack has been designed with multiple safety systems in place to help ensure its safety in the real world. In the simulated side-impact crash test, a new U.S. safety test for the 2011 model year, metal punctured the battery, the official said. The fire in May was severe enough to burn vehicles parked near the Volt, the agency official said. Investigators determined the battery was the source of the fire, the official said.

"Based on the available data, NHTSA does not believe the Volt or other electric vehicles are at a greater risk of fire than gasoline-powered vehicles. In fact, all vehicles -- both electric and gasoline-powered -- have some risk of fire in the event of a serious crash." The request also includes recommendations for minimizing fire risk. NHTSA said it does not believe the Volt and other electric vehicles are at greater risk for fire than gasoline-powered engines.

The Volt is a plug-in electric hybrid that also has a gasoline engine. GM said it was not aware of any other Volt fires. A senior NHTSA official said the agency has received no consumer complaints about fires involving GM or other electric cars. The agency plans additional electric car battery tests with Energy Department experts in coming weeks. Those batteries deliver the power and range that electric vehicles require, but the current generation of lithium-ion batteries also has a tendency to overheat.

Nissan Motor Co Ltd makes the other mass-produced electric car, the Leaf. Nissan officials said there have been no reports of Leaf fires. "The Nissan Leaf battery pack has been designed with multiple safety systems in place to help ensure its safety in the real world," Nissan spokesman David Reuter said. South Korean battery maker LG Chem Ltd, which supplies the Volt battery cells, had no immediate comment. NHTSA said the Volt crash test last May -- a side-impact test -- damaged the battery pack, but the exact reason for the fire is not yet clear. Pure electric vehicles like the Leaf also have limited range before recharging. GM has sold about 5,000 Volts.