A rule-based energy management system integrating a semi-empirical battery model for hybrid wheel loaders

This paper addresses the challenge of developing an energy management system (EMS) for a series hybrid wheel loader that must operate in extreme temperatures (i.e., −20 °C and 35 °C) without an active cooling/heating system. Current research solving similar challenges often relies on EMS strategies that require prior knowledge of future driving conditions, and neglects critical battery behaviours. To overcome these limitations, one of the main contributions of this paper is the experimental characterisation and derivation of a semi-empirical electrical and thermal model for a battery module. In addition, by integrating the battery model, a rule-based EMS is designed to control the battery temperature through the mechanisms, such as decreasing the charging current and maintaining a charge-sustaining at the optimal state of charge. The optimal state of charge is calculated based on the minimisation of average resistance, irreversible heat, and reversible heat by employing the semi-empirical battery model. Simulation results demonstrate that the proposed EMS enables the battery to operate for 8 h without exceeding its thermal limits. In summary, this study offers a practical EMS solution that operates independently of future driving condition forecasts, providing significant advantages for real-time implementations.