Nissan this week announced a new warranty clause for owners of its Leaf electric vehicle, promising to restore battery capacity for any cars that fall below a certain threshold within five years or 60,000 miles. Executive Vice President Andy Palmer announced the new policy Thursday, telling Leaf owners that Nissan would "repair or replace" any lithium-ion battery that falls below nine out of the 12 available bars — about 70 percent of its original capacity.

Palmer said the warranty would go into effect during the Spring of 2013, and that it would apply to the 2013 Leaf, as well as 2011 and 2012 models. For now, only US drivers are eligible, though the company plans to extend coverage to other markets, as well.

"At or above nine bars."

Nissan says its new policy is intended to "put customer minds at ease regarding the topic of battery capacity loss," noting that it is the first EV manufacturer to offer this kind of coverage. There are, however, some caveats to consider. Nissan was careful to point out that it would only restore battery capacity "at or above a minimum of nine bars" — rather than a full charge — since gradual capacity loss is normal for electric vehicles.

It's unclear whether Nissan has made significant progress toward improving this standard degradation, though the manufacturer has been working on sharpening the precision of its battery capacity gauges. According to Palmer, they'll "have more to report on this topic in the New Year."