GM damps Volt fire furor

GENERAL Motors has added more steel protection around the lithium-ion battery pack of its petrol-electric Volt to help prevent potential fires caused by fluid leaking from punctured battery cells.

The company will also add a fluid leak sensor and an additional bracket to prevent overfilling of the Volt battery in response to an official investigation by the United States National Highway and Traffic Administration (NHTSA) after a Volt went up in smoke in a holding yard three weeks after an independent side pole crash test.

The leaking fluid apparently crystalised, causing a chemical reaction that shorted out electronics in the under-floor pack, starting the fire that spread to some other crashed cars in the yard.

The chemical reaction was later replicated in a NHTSA laboratory test, in which the fire started six days after the pack was punctured.

No fires have been reported in cars in customer hands in the US, where almost 10,000 Volts are already on the roads.

GM says the fix will be made on all new cars built after the Christmas factory shutdown ends this month, and from February can be retrofitted to cars already on the roads in North America

Left: Volt structural enhancements and a still from the car's side impact pole test.

The same modifications can be expected on Volts to be sold under Holden badges in the fourth quarter of this year.

GM says it successfully crashed tested four vehicles fitted with the modifications in December.

“The enhancement performed as intended,” the company said in a statement. “There was no intrusion into the battery pack and no coolant leakage in any of the tests.”

GM senior vice president of global product development Mary Barra defended the Volt’s safety record, saying it had always been safe to drive.

“Now, we will go the extra mile to ensure our customers' peace of mind in the days and weeks following a severe crash," she said.

Ms Barra said no changes had been made to the Volt battery pack or cell chemistry, only the surrounding steel protection.

“We have tested the Volt's battery system for more than 285,000 hours, or 25 years, of operation,” she said.

“We're as confident as ever that the cell design is among the safest on the market."In the US, Volt customers will be individually notified when the modifications are available for their vehicles.

While GM is confident it has the problem licked, NHTSA says its investigation continues.

"The agency has not concluded that investigation and is continuing to gather and assess information on the post-crash fire risk in these vehicles," the agency said.