POWER STORAGE SYSTEM AND POWER STORAGE METHOD

A power storage system includes: a first storage battery that is configured to be supplied with power generated by a power generation element performing environmental power generation and to supply power to an external load apparatus; a second storage battery that is configured to have a capacity larger than a capacity of the first storage battery, and to supply power to the external load apparatus; a first switch unit that performs switching between an electrical connection state and disconnection state between the first storage battery and the second storage battery; and a first changeover unit that compares a voltage of the first storage battery with a first threshold voltage which is equal to or higher than a voltage causing the external load apparatus to be operated, and controls the first switch unit according to a comparison result.