This paper presents a method to model losses of the electric drive for electric vehicles from the limited information provided in the efficiency map. A Particle Swarm Optimisation (PSO) algorithm and simple loss model based method is used to extract the loss coefficients from the motor drive efficiency map. The copper loss, hysteresis loss, eddy current loss and windage loss of the motor and switching and conduction losses of the inverter are considered. The method is used to analyze how to increase the range of heavy duty electric trucks. Sensitivity analysis is performed to identify the key parameters contributing to the range. Influence of different powertrain architectures on the range are studied. The proposed method proves to be effective. Comapred to directly applying the efficiency map, the proposed method provides more insigts into the loss distribution in the inverters and motors, reveals the key factors influencing the powertrain loss and can be used to guide the optimisation of the powertrain architecture and motors for future designs.@en