CHARGER, CHARGING SYSTEM, AND CHARGING METHOD

A completion time setting section sets a completion time that is a time at which charging of a secondary battery is completed. An output current measurement section acquires an output value of a current from a natural energy power supply apparatus. A power amount measurement section acquires an amount of power that is supplied until the charging of the secondary battery is completed. A predicted time calculation section calculates a time at which the charging of the second battery is completed by only the natural energy power based on the output value and the power amount as a predicted time. A control section causes the secondary battery to be charged with only the natural energy power when the predicted time is earlier than the completion time.