Charging Patterns for Users of Plug-In Hybrid Vehicles (PHEVs)

Slowik, Linda, Nizar Al-Holou, Arthur Smith-Vaughn, M. Tamer, and Mohammed Arafat

Vehicles that run on electricity with gas generator support systems can, in practice, be driven on a regular basis using only gasoline, without charging; this pattern of use would negate the possibilities of cost savings and reduced greenhouse gas production that are intended to be achieved with such vehicles.  What little research exists on this topic indicates people primarily use PHEVs to save money.  However, these studies bear little resemblance to the reality of daily life for average people, as they focus on early adopters (those in the upper class), fail to use vehicles such as what the average person drives (i.e., average vehicle age is now 10.8 years), and also fail to include other psychological factors.  To address these shortcomings, the Department of Electrical Engineering and Psychology Department conducted an interdisciplinary project exploring factors related to charging behavior in a study designed to closely approximate the real plug-in experience of average people using typical vehicles.  

In the current study, the participants’ own daily-use vehicle was set up with a charging device that was similar to the power cord and plug of a PHEV.  An OBD-II device recorded miles driven.  For six weeks, their charging and driving data were collected and assessed to determine the “gas savings” achieved through “charging” the vehicle, which was used to reward participants for charging the vehicle and therefore saving gas.  To determine the degree to which gas cost may influence charging behavior, gas prices varied over the course of the study.  Participants also completed a brief survey assessing personality and other stable characteristics, questions about their habits with regard to their car/truck, charging common devices (i.e., phone, labtop), and anticipated charging habits with a real PHEV. 

A total of five participants volunteered for the study, representing middle class and average person reasonably well.  The simulated charge device operated fairly well; participants “charged” their vehicle an average of 36 hours/week.  Contrary to past research, charging patterns did not vary as a function of gas prices; rather, some people tended to charge more than others.  Interestingly, the best predictors of simulated charging were car care habits (degree to which they kept their car clean and properly maintained) and agreeableness.  Agreeableness, which refers to caring about the needs and feelings of others, was also related to car care habits and expected charging behavior of real PHEV.  Interpreting the results using life space theory (cf., Lewin, 1969) suggests that those who are more agreeable and attentive to others are similarly attentive to maintaining their vehicle.  Following operant conditioning theory (cf., Skinner, 1951), the charging habit is a relatively simple extension of the established habits of caring for the car. 

             Future research should extend the current study by including more people for a longer period of time.  Other psychological aspects should be considered, and more attention should be focused on establishing the psychometric properties of the scales included here.