PHEV Battery Aging Study Using Voltage Recovery and Internal Resistance From Onboard Data

It is well known that batteries do not perform equally throughout their lifetimes. Their properties are in constant degradation, their capacity fades, and the maximum power reduces. Battery aging has been widely studied under laboratory-controlled conditions for different types of cells. In real life, however, every person has their own driving profile, which is almost unique and unpredictable, making the state of health (SOH) during real-life cycles highly difficult to estimate accurately. This paper presents a methodology for aging estimation based on data extracted from onboard data loggers installed in an electric vehicle (EV). When a driver turns off the vehicle, the battery voltage slowly increases until it finally reaches the open circuit voltage (OCV). It has been observed that the recovery voltage transition depends on the temperature and aging, providing new elements to verify the battery SOH.