The present invention relates to an electronically driven pressure boosting system that is used to boost the torque output of an internal combustion engine. The system comprises an electrically driven pressure charging device, an electrical supply system for providing electrical power to drive the pressure charging device including a battery and an engine-driven battery recharger, and an electronic control system for controlling the operation of the pressure charging device and the electrical supply system. The electronic control system determines one or more allowable operating limits to the operation of the pressure charging device based on the state of the electrical supply system, and drives the pressure charging device using the engine-driven battery recharger when the state of the electrical supply system is within an acceptable range. The engine control system then isolates at least partially the battery from the engine-driven battery recharger and drive the pressure charging device using the battery when the state of the electrical supply system is not within an acceptable range.