Methods for measuring and modelling a battery's overpotential

During the charge and discharge states a battery’s voltage does not equal its Electro-Motive Force (EMF). The difference between the EMF and the voltage during current-flowing conditions is defined as the overpotential. Measurements, modelling and simulation results obtained for battery overpotentials are presented in this chapter. Overpotential measurements involving partial and full charge/ discharge steps are presented in section 5.1. Overpotential symmetry, a phenomenon discovered during the analysis of the measurement results, is also presented in this section. A new overpotential model that includes C-rate current dependency and the simulation results obtained with this model are presented in section 5.2. These results are also compared with the measurement results. Finally section 5.3 presents concluding remarks.