Extending battery lifetime for electric wheel loaders with electric-hydraulic hybrid powertrain

Electrification is the future trend for construction machinery due to its advantage of zero-carbon emission. The battery of electric construction machinery has an inevitable degradation phenomenon, which will increase the maintenance cost. In this paper a parallel electric-hydraulic hybrid powertrain is proposed to extend battery lifetime of an electric wheel loader by utilizing a hydraulic powertrain to provide and capture power during launch and braking. Different operation modes are analyzed and a rule-based energy management strategy is developed to determine the holding and switching conditions of each mode. Powertrains and battery aging models are introduced in detail and dynamic simulation is developed in Simulink. Results show that the parallel electric-hydraulic hybrid powertrain with the proposed strategy can reduce the battery full equivalent cycles, thereby achieving a 15.64% improvement in the battery lifetime compared with the pure electric powertrain. Moreover, influences of the strategy parameters on extending the battery lifetime are further discussed, which gives a parametric design guideline to the energy management strategy.