Secondary battery system using temperature threshold in response to lithium ion concentrations

A secondary battery system, comprising:

• a secondary battery having an electrode body impregnated with an electrolyte containing lithium ions;
• and
• a control unit configured to permit charge and discharge of the secondary battery when temperature of the secondary battery is equal to or more than a threshold temperature and to restrict the charge and discharge of the secondary battery when the temperature of the secondary battery is less than the threshold temperature, wherein
• the control unit is configured to obtain a value related to a minimum concentration of the lithium ions in a region of the secondary battery, the region having the smallest concentration of the lithium ions out of all regions in the secondary battery due to a deviation in concentration distribution of the lithium ions in the electrode body, and to set the threshold temperature to be higher as an amount of decrease in the minimum concentration becomes larger, the amount of decrease being represented by the related value.