Credit: GM

Today GM announced that it will introduce changes to the Chevrolet Volt to guard against fires like the ones that occurred after crash tests last year.

New Volts will incorporate the changes, including steel reinforcements, starting this month. The approximately 12,000 cars that have already been built (about 8,000 have been sold so far) can also be retrofitted at dealerships starting in February. The retrofits will be part of a voluntary program, not an official product recall.

GM has also confirmed what caused a handful of Volt battery fires in testing last year. A side-impact test caused part of the Volt's structure to break into the battery casing, and a small coolant leak was exacerbated when, as part of the test procedure, the battery was slowly turned over. When the battery pack was upside down, the coolant leaked onto a circuit board, which caused a short, and then the fully charged battery caught fire.

The fires could likely have been avoided if the batteries had simply been drained of charge after the test—much as a conventional vehicle would have its gas tank drained. The fires didn't start right after the crash tests, so there would be plenty of time to do this. But the changes to the Volt are meant to prevent coolant leaks as the result of a side-impact collision.

Much has been made of the fact that the Volt battery pack isn't encased in metal, while the pack for the Nissan Leaf electric car is. But the Volt pack is, in fact, well protected by a steel tunnel built into the floor of the car.

Battery Reinforcements: Engineers add steel brackets to the undercarriage of the Chevrolet Volt. Credit: GM

GM is adding extra steel braces to the steel tunnel to further protect the battery. The company says tests show this will prevent coolant leaks. GM is also adding coolant level sensors and a special tamper proof cover meant to prevent overfilling of the coolant.

Mary Barra, GM's senior vice president of global product development, said today that the fires were not the result of a problem the battery cells inside the battery pack. She also said no changes will be made to the manufacture of the battery pack itself. And she expressed confidence in the safety of the lithium-ion chemistry GM is using, saying that the cells had been subjected to rigorous tests, including driving nails through them.

Despite all of those tests, apparently the cells—at least when fully charged—are still not robust enough to keep from catching fire after a short caused by a coolant leak.

It's not clear whether a more stable battery chemistry, such as the lithium-iron phosphate materials used by companies such as A123 Systems, could have prevented the fires.

The plug-in Prius. Credit: NAIAS

Nissan and GM have been at the center of attention when it comes to electric vehicles, with the first sales of the Chevrolet Volt and Nissan Leaf last month, but now Ford and Toyota are weighing in.

At the Consumer Electronics Show last week and the North American International Auto Show in Detroit this week, Ford has officially unveiled the electric Ford Focus, which will go on sale late this year, along with new hybrid and plug-in hybrid vehicles, which will go on sale next year. The plug-in hybrid will travel farther than a conventional hybrid under electric power alone, but Ford isn't saying how far.

In Detroit Toyota revealed its plans for a family of Prius hybrid vehicles, which includes a plug-in version of the car (due next year), a larger version of the Prius (Prius v, on sale later this year) and a smaller one (Prius c concept).

Toyota's plan to stick with the successful Prius platform could be wise, as we argue here. These cars (including the plug-in version) use smaller batteries than the Leaf or the Volt, which makes them cheaper.

BYD, the Chinese automaker made famous by an investment from Warren Buffet, says it plans to start selling electric cars in the United States next year, after failing to deliver on a promise to sell the vehicle last year.

Porsche has announced that it will make a production version of its 918 Spyder plug-in hybrid concept car.

The car, which was first shown off this year at the Geneva Auto Show, can accelerate to 60 miles per hour in under 3.2 seconds, and reach a top speed of 198 miles per hour. It pairs an electric motor with an eight-cylinder engine. Drivers will be able to putter along for 16 miles using electricity alone. In ordinary hybrid mode, the car can get 94 miles per imperial gallon (about 78 mpg). For the highest performance, select Sport Hybrid or Race Hybrid mode. The latter includes a "push-to-pass" button that delivers a surge of power from the battery.

With Porsche getting in on the electric-powered action, one wonders how up-starts like Fisker and Tesla will manage.