US Patent 10114079 System and method for identifying vehicle battery decay

A vehicle includes a traction battery. A controller is configured to operate the traction battery according to a capacity estimate. The capacity estimate is based on a difference between a current-based estimation and a voltage-based estimation of a change in battery state of charge over a time interval. The difference is evaluated over a predetermined number of time intervals. When more than a predetermined percentage of the differences exceed a threshold, the capacity estimate is updated based on an average of the differences.