A battery control device comprising: a battery controller that calculates a maximum current value (imax2) which can be made to flow through a battery; and a storage unit containing a database storing an exponential function, wherein the battery controller includes a battery equivalent circuit model unit that calculates a polarization voltage (VpO) at a present time of the battery by using each information of a current value, a battery closed circuit voltage, and a temperature of the battery; wherein the storage unit stores a parameter (Gt) representing a temporal change in a polarization voltage after a predetermined time t determined based on the exponential function stored in the database; and wherein the battery controller calculates the maximum current value at the time t, based on a corrected value of an allowable current value in the case where it is assumed that the current battery is in a non-polarization state (Imax1), wherein the correction is obtained by substracting from the allowable current value in the case where it is assumed that the current battery is in a non-polarization state a value (Δi) obtained by: a product (Vp0.Gt) of the parameter representing the temporal change in the polarization voltage stored in the storage unit and the polarization voltage at a present time calculated by the battery equivalent circuit model unit, the product being the divided by a value of a predicted battery internal resistance after a constant current has flowed for a predetermined time, assuming that the constant current flows form an initialized non-polarization state. a battery controller that calculates a maximum current value (imax2) which can be made to flow through a battery; and a storage unit containing a database storing an exponential function, wherein the battery controller includes a battery equivalent circuit model unit that calculates a polarization voltage (VpO) at a present time of the battery by using each information of a current value, a battery closed circuit voltage, and a temperature of the battery; wherein the storage unit stores a parameter (Gt) representing a temporal change in a polarization voltage after a predetermined time t determined based on the exponential function stored in the database; and wherein the battery controller calculates the maximum current value at the time t, based on a corrected value of an allowable current value in the case where it is assumed that the current battery is in a non-polarization state (Imax1), wherein the battery controller includes a battery equivalent circuit model unit that calculates a polarization voltage (VpO) at a present time of the battery by using each information of a current value, a battery closed circuit voltage, and a temperature of the battery; wherein the storage unit stores a parameter (Gt) representing a temporal change in a polarization voltage after a predetermined time t determined based on the exponential function stored in the database; and wherein the battery controller calculates the maximum current value at the time t, based on a corrected value of an allowable current value in the case where it is assumed that the current battery is in a non-polarization state (Imax1), wherein the correction is obtained by substracting from the allowable current value in the case where it is assumed that the current battery is in a non-polarization state a value (Δi) obtained by: a product (Vp0.Gt) of the parameter representing the temporal change in the polarization voltage stored in the storage unit and the polarization voltage at a present time calculated by the battery equivalent circuit model unit, the product being the divided by a value of a predicted battery internal resistance after a constant current has flowed for a predetermined time, assuming that the constant current flows form an initialized non-polarization state.