Electrified vehicle control of bi-directional DC/DC converter for high voltage power assist from low voltage system

A vehicle comprising:

• a traction battery having a first nominal voltage;
• an auxiliary battery having a second nominal voltage lower than the first nominal voltage of the traction battery;
• a bi-directional DC/DC converter configured to convert voltage associated with the traction battery and the auxiliary battery between the first nominal voltage and the second nominal voltage;
• an electric machine powered by the traction battery and configured to provide propulsive power to the vehicle;
• an internal combustion engine;
• a plurality of electric accessories;
• and
• a controller programmed to control the DC/DC converter and the electric machine to supply power from the auxiliary battery through the DC/DC converter to the electric machine for a specified period of time in response to electric machine power demand being between a first threshold and a second threshold, and to reduce power supplied to at least one of the plurality of electric accessories in response to the electric machine power demand exceeding the second threshold.