Research on a piecewise mathematical model with decay factor for battery

The classical battery equivalent circuit model has a shortcoming that it doesn't reflect the effects caused by electrochemical polarization and concentration polarization to battery terminal voltage well. In this study, in order to overcome the shortcoming, the classical equivalent circuit model for Nickel metal hydride battery used in electric vehicles was improved. According to the circuit theory, the analysis was carried out for the four different phases of battery by the improved equivalent circuit model. Four different phases were charge phase, change idle phase, discharge phase, discharge idle phase, respectively. A new piecewise mathematical model with decay factor was deduced according to the equivalent circuit equation. Pulse discharge and charge experiments were designed, and identification method of parameters was introduced. Predicted data by the model and measured data were compared and the results show the predicted data matched the measured data very well. In addition, the model exhibits good precision.