Difference between constant efficiency and loss map of an electric drive on fuel saving on a P-HEV

Retrofit electrification of engine-powered vehicles to plug-in hybrid electric vehicles is growing. Different hybrid solutions exist, but all of them must compromise between integration constraints, cost and efficiency. Full vehicle simulation, including the powertrain subsystems is thus mandatory. During the pre-design step, some sub-systems are not available. Use a simplified model for some subsystems is then common, to initiate the sizing process. In this paper, two electric drive models are compared: one using a torque and speed dependent loss map and another with a constant efficiency. Using Dynamic Programming, the fuel consumption is estimated for both models. The simple average efficiency leads to only 3% of errors on fuel saving. Such simple model can thus be relevant for the comparison of solutions in terms of fuel saving.