An electric propulsion system includes a rotary electric machine having an output member, a rechargeable energy storage system (“RESS”) connected to the electric machine, a user interface device, and a controller. The RESS includes multiple battery modules and a switching circuit, the latter being configured, in response to electronic switching control signals, to connect the battery modules in a parallel-connected configuration or a series-connected configuration, as a selected battery configuration. The user interface device receives an operator-requested drive mode request as an electrical signal indicative of a desired drive mode of the electric propulsion system. The controller, which is programmed with mode-specific electrical loss information associated with the desired drive mode, establishes the selected battery configuration in response to the drive mode request, and presents a drive mode recommendation via the user interface device when the loss information associated with the desired drive mode exceeds a calibrated loss threshold.