Unified Power-Based Analysis of Combustion Engine and Battery Electric Vehicle Energy Consumption

The previously developed power-based fuel consumption theory for Internal Combustion Engine Vehicles (ICEV) is extended to Battery Electric Vehicles (BEV). The main difference between the BEV model structure and the ICEV is the bi-directional character of traction motors and batteries. A traction motor model was developed as a bi-linear function of positive and negative traction power. Another difference is that the accessories and cabin heating are powered directly from the battery, and not from the powertrain. The resulting unified model for ICEV and BEV energy consumption has linear terms proportional to positive and negative traction power, accessory power, and overhead, in varying proportions. Compared to the ICEV, the BEV powertrain has a high marginal efficiency and low overhead. As a result, BEV energy consumption data under a wide range of driving conditions are mainly proportional to net traction power, with only a small offset. Powertrain ‘bottom-up’ data and vehicle ‘top-down’ data are well described by the model. The observed powertrain transfer function can be used to estimate the energy consumption changes when it is used in different vehicle variants or under different driving conditions. Analytically derived range estimates are then possible for variants of a base BEV, just as analytically derived fuel economy can be estimated for ICEV variants.