GM finds fix for Volt fires

DETROIT—General Motors Co. is advising Chevrolet Volt owners to return their electric cars to dealerships for repairs to lower the risk of battery fires.

Three Volt batteries caught fire after government crash tests last year, prompting a U.S. federal investigation, sending GM engineers into a mad-scramble to find a fix.

The company say it’s adding steel to the plates protecting the batteries to the 8,000 Volts on U.S. roads—for free—and the other 4,400 sitting on dealer lots to ease worries about the car's safety. It will also add a sensor in the reservoir of the battery coolant system to monitor coolant levels.

A tamper-resistant bracket on top of the coolant reservoir will prevent coolant overfill.

GM and federal safety officials believe last year's 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.

No owners, however, have reported fires after crashes.

Fixing the Volt’s image is a hugely important for GM as it tries to reform its image into a greener, more innovative carmaker despite weak sales figures from its first fully electric car.

The safety stumble could still make it harder for the Volt to compete with rival electric cars like the Nissan Leaf. To contain the bad publicity after the fires, GM last year offered to buy back Volts from worried owners.

Adding the steel will spread the force of a crash over a larger area, says Mary Barra, GM's product development chief. Tests by GM and the government have shown that the repairs, to start in February, will prevent battery damage and coolant leaks.

GM has done crash tests on four reinforced Volts, finding the fix had worked. The National Highway Traffic Safety Administration (NHTSA) also has crash-tested a Volt with the added steel.

“The preliminary results of the crash test indicate the remedy proposed by General Motors today should address the issue,” the federal safety agency says.

The agency will monitor the crashed car for another week as it continues its investigation.

GM sold 7,671 Volts last year, falling short of its goal of 10,000. Its main competitor, Nissan's Leaf, sold 9,674. The Volt had its best month ever in December with 1,529 sales.

The $40,000 Volt has a T-shaped, 181 kilogram battery pack that powers the car for about 56 kilometres. After that, a small gasoline generator kicks in to run the electric motor.

NHTSA began studying the Volt batteries after a test car caught fire last June. The fire broke out three weeks after a side-impact test.

At first, GM blamed NHTSA for the June fire, saying it should have drained the battery to prevent any fires after the test.

But the company quickly retreated, conceding it had never told NHTSA to drain the battery. GM executives also said there was no formal procedure in place to drain batteries after crashes involving owners.

NHTSA opened an investigation into the Volt's safety in November following that fire and two others that occurred after tests.

Now the company sends out a team to drain the batteries after being notified of a crash by its OnStar safety system.

Publicity about the fires touched off a massive effort by GM engineers to find the cause and fix the problems quickly.

In December, GM CEO Dan Akerson offered to buy back Volts from any owner who wasn't satisfied and offered free loaner cars to customers concerned about safety.

So far, about 250 of the owners have asked for a loaner or a buyback.