Experimental Assessment of Battery Cycle Life Within the SIMSTOCK Research Program

Abstract

The steadiness over time, of on-board Energy Storage Systems (ESS) performances is a major issue fora successful and massive diffusion of electrified, hybrid and electric vehicles. Capacity fade and internal resistance increase due to ageing will directly affect vehicle range and performances. Therefore, ESS ageing forecasting remains an important area of investigations. Reaching this goal involves fundamental research on materials, experimentation, simulation and design by the end users. This paper describes the main results of a 3.5-year, 4.2 M€ collaborative research program on battery ageing, SIMSTOCK, which was finished in fall 2011. This program has involved 15 partners among which, research labs, ESS manufacturers, automotive components suppliers and vehicle manufacturers, with the support of the French agency ADEME.This paper will then focus mainly on modeling and simulation of a lithium-ion high power cell tested within the program. First, it describes the development of a numerical equivalent electrical circuit model of battery, associated with a calibration tool and its experimental validation. Secondly, it describes the construction of a Design of Experiments (DOE), its use and validation, for defining mathematical expressions, representing the battery model parameters evolutions, as a function of battery ageing. Thirdly, the paper details a mathematical method created with the aim to take into account the cycling and the calendar effects on battery characteristics during the experiment on tests benches. Finally, the battery model is integrated in a full hybrid vehicle model, on Imagine Lab AMESim simulation platform, to determine, with realistic driving conditions, the impact of battery ageing on the vehicle performance and fuel consumption.