A power storage system, comprising: a parameter detector configured to detect a parameter of a secondary battery; a table storage unit configured to store a table indicating a correspondence between the parameter of the secondary battery and a charging condition; and a charging control unit configured to refer to, based on the detected parameter, a corresponding charging condition from the table and make control to charge the secondary battery in this charging condition, wherein the table is a table showing a correspondence between a combination of the temperature of the secondary battery with an internal resistance and a charging condition, wherein the charging condition is provided as an optimal charging current that is defined to ensure a predetermined use period of the secondary battery, wherein the power storage system further comprises: an amount-of-deterioration calculator configured to calculate an amount of deterioration of the secondary battery; and an allowable amount-of-deterioration calculator configured to calculate an allowable amount of deterioration of the secondary battery, wherein the charging control unit is configured to compare the calculated amount of deterioration with the calculated allowable amount of deterioration and to update the charging condition of the table such that the deterioration speed of the secondary battery is suppressed according to a result thereof, wherein the amount-of-deterioration calculator and the allowable amount-of-deterioration calculator calculate the amount of deterioration and the allowable amount of deterioration, respectively, according to a predetermined timing condition, and characterized in that the charging control unit is configured to update, if a change value of the amount of deterioration that is next acquired with respect to the amount of deterioration at a point of time at which the charging condition of the table was updated is larger than a change value of the allowable amount of deterioration that is next acquired with respect to the allowable amount of deterioration at the point of time at which the charging condition of the table was updated, the charging condition of the table such that a deterioration speed of the secondary battery is reduced. a parameter detector configured to detect a parameter of a secondary battery; a table storage unit configured to store a table indicating a correspondence between the parameter of the secondary battery and a charging condition; and a charging control unit configured to refer to, based on the detected parameter, a corresponding charging condition from the table and make control to charge the secondary battery in this charging condition, wherein the table is a table showing a correspondence between a combination of the temperature of the secondary battery with an internal resistance and a charging condition, wherein the charging condition is provided as an optimal charging current that is defined to ensure a predetermined use period of the secondary battery, wherein the power storage system further comprises: an amount-of-deterioration calculator configured to calculate an amount of deterioration of the secondary battery; and an allowable amount-of-deterioration calculator configured to calculate an allowable amount of deterioration of the secondary battery, an amount-of-deterioration calculator configured to calculate an amount of deterioration of the secondary battery; and an allowable amount-of-deterioration calculator configured to calculate an allowable amount of deterioration of the secondary battery, wherein the charging control unit is configured to compare the calculated amount of deterioration with the calculated allowable amount of deterioration and to update the charging condition of the table such that the deterioration speed of the secondary battery is suppressed according to a result thereof, wherein the amount-of-deterioration calculator and the allowable amount-of-deterioration calculator calculate the amount of deterioration and the allowable amount of deterioration, respectively, according to a predetermined timing condition, and characterized in that the charging control unit is configured to update, if a change value of the amount of deterioration that is next acquired with respect to the amount of deterioration at a point of time at which the charging condition of the table was updated is larger than a change value of the allowable amount of deterioration that is next acquired with respect to the allowable amount of deterioration at the point of time at which the charging condition of the table was updated, the charging condition of the table such that a deterioration speed of the secondary battery is reduced.