A predictive trip-based method for state of charge maintenance in series PHEVs to boost cold weather efficiency

Plug-in hybrid electric vehicle operating efficiency decreases due to cold weather conditions. This reduced efficiency is the result of factors such as deteriorated lithium-ion battery performance at extreme temperatures and engine operating temperature at start-up. This paper presents a method that considers the particular case of a series configured Extended Range Electric Vehicle (EREV) operating in charge sustaining mode. A computer optimization strategy is proposed and implemented for determining an optimum engine on/off scheduling strategy for cold-weather operation, specifically for charging the traction battery in a series configured EREV operating in charge sustaining mode. Only engine efficiency is considered with respect to warm-up time and trip duration, while considering the advantages of a trip-based on/off scheduling strategy including GPS, traffic pattern monitoring and operator-anticipated trip duration.