A Study on the Impact of Driving in Charge Mode on Well-to-Wheels Greenhouse Gas Emissions of Plug-In Hybrid Electric Vehicles 2022-01-0668

Plug-in hybrid electric vehicles (PHEVs) combine some of the attractive traits of both fully electric vehicles (EVs) and non-plug-in hybrid vehicles (HVs). EV traits shared by PHEVs include the capability to charge the battery via electricity from the grid while the vehicle is parked and the ability to drive an appreciable distance without having to turn the engine on, in what is known as charge depletion mode. HV traits shared by PHEVs include the ability to use the engine to maintain the state of charge (SOC) of the batteries within certain limits, in what is known as charge sustaining mode. Charge sustaining mode allows a PHEV to drive long distances without requiring stops for electrical charging (unlike EVs) but comes at the trade-off that fuel needs to be used. A mode of driving that is unique to PHEVs (though not seeing much real-world use at present day), referred to as “Charge Mode is when the engine is operated at a higher power output than the average vehicle power demand, thereby increasing the SOC of the battery (to allow for electric drive in a subsequent trip section) at the expense of more gas usage while increasing the SOC. This study utilizes an open-source fuel economy simulation software along with a model of Prius Prime (25-mile electric range PHEV) that has been calibrated via on-road testing data to examine the effect of engaging charging mode on the fuel consumption within virtual trips towards a geo-fenced area. Simulation results are in general agreement with on-road testing that the average net impact on fuel consumption is less than 5%.