The batch mill grinding equation can be described as being developed with respect to a control volume defined around the batch mill, How ever the advent of ball mill charge motion simulation using the discrete element method opens the door to determining the frequency of breakage events as well as the energy engaged therein, One can now envisage the development of a breakage model around the control volume defining the breakage event. In addition, one can postulate from first principles that an energy balance can be defined for this event along with a mass balance. In this paper, just such a hypothesis is formed and a fundamental batch mill model defined. Further an identification procedure is proposed that allows model calibration from experimental data. Simulation results are compared with results obtained from the batch grinding equation using published parameters.