Embodiments of the invention provide a hybrid drive system including a power source. The hybrid drive system can include a hydraulic system operatively coupled to the power source. The hydraulic system can include at least one hydraulic module coupled to the power source and at least one accumulator fluidly coupled to the hydraulic module. The drive system can include at least one drive wheel operatively coupled to the hydraulic system. The drive wheel can be configured and arranged to receive power only from the hydraulic system. The hydraulic system can be configured and arranged to supplement power provided by the power source to the drive wheel. The hybrid drive system can include an electronic control unit in communication with the power source, the hydraulic module, and a sensor associated with the accumulator.
