An agricultural baler (10) includes a main bale chamber (26) and a plunger (30) reciprocally movable within the main bale chamber (26) through a compression stroke and a return stroke. The plunger (30) has a duty cycle (100) with a maximum power requirement (108), a minimum power requirement (110), and an average power requirement (102) over the duty cycle. A flywheel (44) is associated with the movement of the plunger (30), and a driveline (50) is associated with the flywheel (44) and couplable with a power take-off (PTO) of a traction unit. The baler is characterized by an auxiliary power system (52) coupled with the driveline (50). The auxiliary power system (52) includes a power indicator (64) providing a plurality of output signals, with each said output signal representing a parameter associated with power usage during the duty cycle of the plunger (30). A power device (54, 58) receives power from and/or transfers power to the driveline (50). An electrical processing circuit (62) is coupled with the power indicator (64) and the power device (54, 58). The electrical processing circuit (62) is operable for receiving each output signal and controlling operation of the power device (54, 58), based on at least one output signal from at least one previous duty cycle.