The US automotive safety authority and General Motors are investigating why a Chevrolet Volt caught fire three weeks after it was subjected to a crash test.
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The news of the fire has sparked concerns over the safety of the vehicle’s lithium-ion battery pack, although at this stage both GM and the National Highway Traffic Safety Administration (NHTSA) have defended the pioneering plug-in hybrid until further tests are conducted.

The Volt caught fire three weeks after a side impact crash test – conducted on May 12 – while parked at the NHTSA’s Wisconsin testing facility, setting fire to other nearby vehicles. Somewhat ironically, after the crashed Volt was subjected to the ‘rotisserie test’ – where the car is rolled and rotated to test for leaks that may have occurred during the crash – it was awarded the maximum five-star safety rating. Subsequent tests have failed to replicate the fire.

But GM says a few simple post-crash preventative measures that were not conducted by the NHTSA could have removed the fire risk. GM chief engineer for electric vehicles Jim Federico said his company was working with a number of interest groups to ensure its internally developed safety protocols were understood throughout the industry.

He explained GM’s protocol was to depower the battery of an electric vehicle after a significant crash, although admitted the NHTSA was not aware of this protocol at the time of the fire.

"First and foremost, I want to make this very clear: the Volt is a safe car,” Mr Federico said.“We are working cooperatively with NHTSA as it completes its investigation. However, NHTSA has stated that based on available data, there's no greater risk of fire with a Volt than a traditional gasoline-powered car.”He said safety protocols for electric vehicles were a concern for the industry."We are working with other vehicle manufacturers, first responders, tow truck operators, and salvage associations with the goal of implementing industry-wide protocols."

LG Chem, the South Korea-based supplier of the Volt’s batteries, said it is “fully aware of the situation and is working closely with GM and NHTSA on the investigation”.

Early signs suggest the car’s usually inert liquid coolant may have come into contact with the lithium-ion battery cells and crystallised in the cold weather. It is believed this led to the battery shorting and catching fire.

The NHTSA and the US Department of Energy will test the battery modules separate from the cars in the coming days, analysing them immediately after impact and again a few weeks later.

The crash test results may give authorities more information to help educate emergency services, tow truck drivers, other first responders and scrap yard operators on the best ways to deal with battery-powered vehicles.

The Chevrolet Volt combines a front-mounted petrol engine/generator with a 180kg T-shaped lithium-ion battery that runs down the middle of the car and branches out below the rear seats.

There are currently around 5000 Volts on the road in the US. GM says it is not aware of any other fires involving the plug-in hybrid and the NHTSA says it has not received any complaints about fires involving it or any other EVs.

Nissan has more than 8000 LEAF electric vehicles on the road in the US and also says there are no reported fires linked to the car.

One GM spokesman said his company expects to distribute a safety device early next year specifically designed to depower the battery after a crash.

The Chevrolet Volt will go on sale in Australia in 2012 badged as a Holden. It follows the Mitsubishi i-MiEV and Tesla Roadster EVs already on the market, and will be joined by the LEAF and the Renault Fluence Z.E. in the coming 12 months.