The way GM designed the Volt's batteries I suspect even a degraded battery won't need replacing. Remember, the Volt never charges past 90% total SOC. This allows for up to 10% battery degradation without impacting the vehicle's sell specification.If these reports of diminished battery capacity from the recall update are accurate, it's interesting to think about how this interacts with the mandated 10-year battery warranty in California (and possibly also other CARB states). According to the New York Times, "The California-spec warranty does not allow for degradation of the battery’s capacity. If it’s not performing to “the highest standard” — that is, as new — during the warranty period, G.M. must repair or replace it, according to David Clegern, a spokesman for the California Air Resources Board." A Battery Warranty With a Warning - The New York Times (nytimes.com)
This California requirement is a bit ridiculous, since all batteries degrade over 10 years. But ridiculous or not, if it's a legal requirement, it would seem to create liability for GM.