Real-life EV battery cycling on the test bench

When choosing a battery system for EV applications, there are many parameters we have to take into consideration: technical parameters, operational experience, economic factors, material availability, and the environment (A. Pellerin, Elec. Hybrid Technol. 96, 68-75). In this paper, we want to concentrate on one parameter only: battery life. The lifetime of traction batteries can be expressed either in terms of number of cycles or in terms of calendar life. Both are important and they strongly depend on the mission profile of the vehicle. A lot of work has been concentrating on bench testing to study the cycle life of traction batteries using standard cycle profiles such as ECE15 or DST. We have learned, however, that the results obtained show significant differences to the results obtained with vehicle trials. After a short introduction talking about the importance of the on-board energy, the EV mission profile and the time factor, we discuss the parameters influencing cycle life: rest periods, ambient temperature, depth of discharge (DOD) or peak power demand, etc. In the second part of the paper, we present a 'complex four-season cycle' integrating the previously mentioned parameters to approach real-life vehicle conditions. (C) 1998 Published by Elsevier Science S.A. All rights reserved.