A hydraulic shovel is provided with a lower travelling body and an upper revolving body revolvably disposed on the lower travelling body. The hydraulic shovel is also provided with a motor disposed on the upper revolving body for driving the hydraulic shovel, a first battery unit disposed on the upper revolving body, a second battery unit disposed on the lower travelling body, and a power supplier that supplies external power to the first battery unit and the second battery unit.

A display controller for controlling a content displayed on the display provided on the working machine comprises a display control unit. The display control unit is configured to display, on the display, an icon image indicating information regarding the working machine and a plurality of graphic meter images indicating respective conditions of the working machine so that the graphic meter images, each in an arcuate shape, are displayed as being arranged so as to surround the icon image.

In an electric drive system in which a battery is not connected to a DC bus, even when a load on a traveling electric motor increases suddenly, it is made possible to avoid such a situation that the DC bus voltage drops to a level equal to or lower than an operating voltage of an inverter and the inverter stops working. To this end, a DC bus voltage drop prevention device controls such that, when the voltage of the DC bus drops below a first threshold value, the output torque of the traveling electric motor is decreased according to an amount of decrease in the voltage of the DC bus, and when the voltage of the DC bus drops below a second threshold voltage lower than the first threshold voltage, the output torque of the traveling electric motor is decreased to zero or a value within a range of magnitude with which a work vehicle stays stationary on a level ground.

A main controller and a hybrid controller control an engine, an assist generator motor, a hydraulic pump and an electricity storage device. In this case, the hybrid controller is provided with a performance state recovery part that performs performance state recovery of the electricity storage device. In a case where a performance state amount varying with repetition of a discharge and a charge of the electricity storage device, specifically, a current integrated value ratio of the electricity storage device goes beyond a predetermined threshold value (L1%), the performance state recovery part limits power of the hydraulic pump. Thereby, the performance state recovery part performs the performance state recovery of the electricity storage device.

An engine cooling system (22) includes an engine (11), an engine cooling pipe line (23), an engine water pump (24) and an engine radiator (25). An electricity storage device cooling system (27) includes an electricity storage device (19), an electricity storage device cooling pipe line (28), an electricity storage device water pump (29) and an electricity storage device radiator (31). Different heat-transfer media (engine cooling water and electricity storage device cooling water) flow respectively in the engine cooling system (22) and the electricity storage device cooling system (27). Further, a heating heat exchanger (32) is provided in the halfway of the engine cooling pipe line (23) and in the halfway of the electricity storage device cooling pipe line (28) for performing heat exchange between the engine cooling water and the electricity storage device cooling water.

A method for operating a drive system for a work machine is described. A first electric motor is associated with a travel drive of the drive system and a second electric motor is associated with a work drive of the drive system. An electric energy store for operating the first and the second electric motors is associated with the travel drive and the work drive. The method includes operating the first electric motor in generator mode to produce braking power of the travel drive, electric power being produced in the generator mode. The method further includes supplying, completely or partly to the energy store and/or to the second electric motor depending on a state of the energy store, the electric power.

A main controller and a hybrid controller control an engine, an assist generator motor, a hydraulic pump and an electricity storage device. In this case, the hybrid controller is provided with a performance state recovery part that performs performance state recovery of the electricity storage device. In a case where a performance state amount varying with repetition of a discharge and a charge of the electricity storage device, specifically, a current integrated value ratio of the electricity storage device goes beyond a predetermined threshold value (L1%), the performance state recovery part limits power of the hydraulic pump. Thereby, the performance state recovery part performs the performance state recovery of the electricity storage device.

A mobile mining machine includes a plurality of traction elements, a plurality of motors, a power source in electrical communication with the plurality of motors, and an energy storage system in electrical communication with the plurality of motors and the power source. Each of the motors is coupled to an associated one of the plurality of traction elements. Each of the motors is driven by the associated traction element in a first mode, and drives the associated traction element in a second mode. The energy storage system includes a shaft, a rotor secured to the shaft, a stator extending around the rotor, and a flywheel coupled to the shaft for rotation therewith. In the first mode, rotation of the motors causes rotation of the flywheel to store kinetic energy. In the second mode, rotation of the rotor and the flywheel discharges kinetic energy to drive the motors.

A storage battery (21) is configured of a plurality of cells (22A) to (22N) series-connected to each other. A battery controller (27) receives power supplied from a lead battery (31). The battery controller (27) executes balancing control that reduces variation in cell voltages (VcA) to (VcN) of the plurality of cells (22A) to (22N). The battery controller (27) executes the balancing control in a time range during which a voltage of the lead battery (31) becomes equal to or more than a predetermined given voltage value (V1) and a charging rate of the storage battery (21) becomes equal to or more than a predetermined given charging rate value (SOC1) after a key switch (16) is switched from an on state to an off state.

A hydraulic pump supplies hydraulic energy to a hydraulic system load. A vehicle controller establishes a commanded rotor speed for the motor or electric machine based on a target pump rotational speed of a pump rotor or pump shaft for operation of the hydraulic pump at a set point or within an operational region consistent with the hydraulic system load or estimated work task of the vehicle for one or more sampling intervals, where the set point or operational region is defined by a hydraulic pump flow rate versus head characterization curve and where the target pump rotational speed can be independent of a rotational speed of the engine shaft (e.g., in a first mode).