General Motors Co. is developing ways to discharge the battery in Chevrolet Volts after accidents to prevent fires like the one that followed a government crash-test of the plug-in hybrid car in May. GM is working on safety practices with the US National Highway Traffic Safety Administration and will make them public when completed, Rob Peterson, a GM spokesman, said. The automaker has taken longer to develop a plan than Nissan Motor Co. did for its Leaf electric car. Both the Volt and Leaf went on sale in December 2010. \"I can\'t conceive that they didn\'t have a standard operating procedure in place for handling a wrecked vehicle before the car went on sale,\" said Clarence Ditlow, executive director of the Centre for Auto Safety in Washington. \"NHTSA and GM should have established protocols in place before it went on sale.\" The procedures are intended to keep rescue workers, dealers and auto-salvagers safe and head off potential fires that may jeopardise the safety reputation of the Volt, which is the focus of GM\'s marketing. \"In all instances when there\'s an accident, you have to have a protocol,\" Dan Akerson, GM\'s CEO, told reporters. \"That was a good lesson that came out of this.\" NHTSA is scrutinising the safety of lithium-ion batteries that power all plug-in electric vehicles after a Volt caught on fire three weeks after a May 12 crash-test. GM believes that a coolant leak helped carry an electrical charge to something flammable inside the battery, Peterson said. If a lithium battery is pierced by steel, a chemical reaction will start raising the temperature and can result in a fire. The company now has a process in place to draw down power in the battery so it won\'t catch fire after a collision, Jim Federico, GM\'s chief engineer for electric cars, wrote on a company website. Top crash rating \"The Volt is safe,\" Federico wrote in a November 15 post on ChevroletVoltAge.com. \"The fire occurred because the battery wasn\'t completely discharged after the test.\" Federico also wrote that, \"GM developed its battery depowering process for the Volt after NHTSA\'s test.\" The agency also has given the car its top crash rating. GM had a process to discharge Volt batteries. The automaker didn\'t distribute it to tow truck drivers, body shops, salvage yards and others who may handle the car after emergency crews stabilise the scene of an accident. Rescue plan Nissan has taught firefighters and rescue teams how to approach the Leaf and make sure the battery is disconnected, said Bob Yakushi, director of product safety for Nissan North America. After emergency workers stabilise the scene, Nissan recommends a Leaf be towed to one of its dealers where the battery will be handled by technicians, Yakushi said. Nissan has not encountered any fires with the Leaf since it went on sale in the US, Yakushi said. While there have been several accidents reported and \"quite a few Leafs were destroyed\" during Japan\'s earthquake and tsunami in March, none caught fire, he said.