Power supply system, transportation apparatus, and method for controlling power supply system

A power supply system comprising:

• a first energy storage having a first power density and a first energy density, a first charge rate indicating a charge rate of the first energy storage;
• a second energy storage having a second power density higher than the first power density and a second energy density lower than the first energy density, a second charge rate indicating a charge rate of the second energy storage;
• a power transmission electric circuit via which an electrical load is connected to the first energy storage and to the second energy storage;
• and
• circuitry configured to
• control the power transmission electric circuit in a first mode when the second charge rate is higher than a second switching threshold while controlling the power transmission electric circuit in a second mode, a ratio of a first electric power amount of an electric power to be supplied from the first energy storage to the electrical load and a second electric power amount of an electric power to be supplied from the second energy storage to the electrical load being changed in accordance with the first charge rate at least in the first mode among the first mode and the second mode, and
• control the power transmission electric circuit in the second mode when the second charge rate is lower than a first switching threshold lower than the second switching threshold while controlling the power transmission electric circuit in the first mode, the second electric power amount in the second mode being smaller than the second electric power amount in the first mode.