Having logged a quarter of a million miles on the road in pre-production models, built more than 300 prototype battery packs and completed tests for more than 50,000 lithium-ion battery cells, GM says its Chevy Volt is on track to meet its remaining production milestones less than a year from launch. But the U.S. car giant, which lost $1.2 billion in its most recent quarter, says there were several key challenges it wrestled with but has now solved: reducing road noise when driving in electric mode, extending battery life and managing energy storage in hot climates.
According to Bill Wallace, Voltec battery engineering group manager, noise was “more evident than we expected” for the Volt. He said the automaker knew it would be an issue (internal combustion engines in conventional vehicles help drown out road noise) for electric mode, but loud culprits were “things we didn’t necessarily expect.” The Volt team discovered, for example, that it wouldn’t be able to use off-the-shelf bushings (used to reduce friction between mechanical parts) or certain hydraulic solutions. “We had some interesting noise coming in” from the bottom of the car, said Farah, so designers “made pressure-relief changes to block those things.”
For the battery, Wallace said GM is “really happy with minor changes” the company has made in conjunction with cell supplier LG Chem. “Battery chemistries, while they may all be lithium-ion,” he said, “are not all created equal.” Farah explained, “This application is not a cell phone,” and so “very small adjustments” to the chemistry were necessary, primarily to extend battery life.
Equipping the battery system to withstand high temperatures presented one of the major hurdles for the Volt team, said Farah. “We have a very sophisticated control system in the vehicle. Our biggest challenge is hot weather storage, where we can’t control that environment.” If you drive the Volt mostly in urban, temperate environments, he said the battery could last “significantly longer” than the guaranteed 10 years. “Our goal is to get that life for everybody,” said Farah, but if you park the car at the Phoenix Sky Harbor Airport all summer, it’s just not realistic. “If you live in Phoenix or Mesa, as long as you charge the car at night and run it during the day,” he said, “our system will keep the battery very happy.”
While battery life has been one of the “biggest challenges” for the Volt, Farah said durability has become one of the “biggest assets in this battery.” With the fourth-generation battery pack that’s deployed in current versions of the Volt, and which will go into production vehicles next year, GM anticipates a competitive advantage. Asked whether the company would data about battery packs’ expected life span in marketing, Farah said, “We believe this is one of the areas where the Chevy Volt will be superior…I don’t know why we wouldn’t use that.”
GM knows it needs to sell a lot more than the performance of its energy storage system. “Our whole goal here is to put together a great vehicle for customers,” said Farah, “not just a battery on wheels.”
However, despite GM’s work on noise, heat and battery life, several questions remain up in the air. “Quite a bit of evolution is still going on,” when it comes to regulations for plug-in vehicles and fuel efficiency ratings, said Volt Vehicle Chief Engineer Andrew Farah in a call with reporters this morning. And at this point, Farah said GM is “not ready to commit to a final [fuel] tank volume because we’re still learning so much.”