Power system for a transport refrigeration unit

A vehicle for transporting goods comprising:

• an axle;
• a transport refrigeration unit (TRU);
• and
• a power system, the power system comprising:
• an energy storage device configured to electrically power the TRU;
• a generator configured to generate electrical power and to supply the electrical power to the energy storage device;
• a multi-speed gearbox mechanically coupling the axle to the generator;
• and
• a controller configured to receive data indicative of a speed of the vehicle and a state-of-charge of the energy storage device, and to control the multi-speed gearbox;
• wherein the controller is configured to set a gear ratio of the multi-speed gearbox to a speed-based gear ratio when the vehicle is in a first state, wherein the speed-based gear ratio is selected based on the speed of the vehicle, and wherein the state-of-charge of the energy storage device is below a first charge threshold in the first state;
• and
• wherein the controller is configured to disengage the multi-speed gearbox or to set the gear ratio to a gear ratio that is lower than the speed-based gear ratio when the vehicle is in a second state, wherein the state-of-charge of the energy storage device is above the first charge threshold in the second state.