Patent ID: 8551630

Claim:
An electric power storage system comprising: a lithium secondary battery including: a positive electrode which has a positive electrode active material containing a metal oxide; a negative electrode containing a negative electrode active material; and an ion conductive medium which is provided between the positive electrode and the negative electrode and which conducts lithium ions; a detection unit to detect a temperature T of the lithium secondary battery; and a control unit programmed to decrease a remaining capacity of the lithium secondary battery based on a temperature Tbx (K) when the detected temperature T increases, the temperature Tbx (K) being a temperature of the lithium secondary battery at which Hs(x,Tbx)>Hd(Tbx) holds, where Hs(x,T) (K/min) indicates a self-heating rate of the lithium secondary battery at a temperature T (K) and a remaining capacity x (%), and Hd(T) (K/min) indicates a heat dissipation rate of the lithium secondary battery at the temperature T (K).