An anonymous reader writes: A few months ago, reports of battery fires from crashed Chevy Volts caused the National Highway Traffic Safety Administration to open an investigation into the type of batteries used in the Volt and other EVs. That investigation has now concluded, and the NHTSA says the cars are safe. 'The agency and General Motors Co. know of no fires in real-world crashes. GM and federal safety officials say they believe the fires were caused by coolant leaking from damaged plastic casing around the batteries after side-impact collisions. The coolant caused an electrical short, which sparked battery fires seven days to three weeks after the crashes. GM announced earlier this month that it will add steel plates to about 12,000 existing Volts to protect the batteries in the event of a crash.'