This chapter elucidates the relationship between the electric drive system and the vehicle. Starting from the longitudinal force balance, it derives the tractive effort requirements that define the motor’s external characteristic: the constant-torque region limited by current, the constant-power region constrained by voltage, and the base speed that separates them. The combined characteristics of the motor and transmission are analyzed, along with the power flow and efficiency chain from the DC source to the mechanical output. Finally, the influence of battery voltage variation on drive system performance is examined, completing the closed-loop analysis of energy conversion from on-board energy storage to vehicle dynamics.