Return air ducts for vehicles

A vehicle comprising:

• an air inlet passage in fluid communication with an outside of the vehicle;
• a cargo compartment configured for holding a battery which heats surrounding air when energized such that air in the cargo compartment becomes heated air;
• a passenger compartment disposed between the air inlet passage and the cargo compartment;
• a heating, ventilation, and air conditioning (HVAC) unit operably disposed between the air inlet passage and the passenger compartment;
• wherein the HVAC unit includes:
• a first inlet, a second inlet, and an outlet all in fluid communication with one another;
• and
• a recirculation door configured for moving between a pass-through position and a recirculation position;
• and
• a return air duct operably extending between the cargo compartment and the second inlet and configured to direct the flow of the heated air from the cargo compartment directly to the HVAC unit;
• wherein the HVAC unit is configured to intake air through the first inlet and exhaust air through the outlet to the passenger compartment when the recirculation door is in the pass-through position;
• and
• wherein the HVAC unit is configured to intake air through the second inlet and exhaust air through the outlet to the passenger compartment when the recirculation door is in the recirculation position.

A method of cooling a battery in a cargo compartment of a vehicle, the method comprising:

• operating a heating, ventilation, and air conditioning (HVAC) unit with a recirculation door in a recirculation position;
• exhausting air from an outlet of the HVAC unit into a passenger compartment;
• drawing air from the passenger compartment into the cargo compartment;
• heating air within the cargo compartment;
• and
• exhausting heated air from the cargo compartment to the HVAC unit through a return air duct such that the heated air is cooled by the HVAC unit.