Design of energy storage unit for hybrid excavator power management

Hybrid technology which has been successfully used on vehicles, is introduced to hydraulic excavators whose load condition is totally different from that of vehicles. An electric motor is employed to the power system to assist the ICE to satisfy the power requirements of the load. Due to the sharply fluctuations of the load, the Energy storage unit (ESU) is considered to be the most important component that affect the energy efficiency, the drivability and the life-time of the hybrid excavators. The design methodology of ESU that for hybrid electric vehicles is inapplicable for HHE for their different load conditions. This paper presents a methodology for determining whether a hybrid excavator ESU should consists of batteries only, ultra capacitors only or a combination of both, and two kinds of ESU consist of NIMH battery and ultra-capacitors separately are designed for 5-ton hybrid excavator test bench. Theoretical analyzing and experimental results show that the ESU with ultra-capacitors only is proposed to be the best one for hybrid excavators. The experimental results also show that the benefits of the BO-ESU are not limited to the ESU efficiency and the cost, it extended to fuel efficiency of the engine and the life extension of the power source.