Battery control system

A battery control system including a lithium-ion secondary battery having a positive electrode plate and a negative electrode plate, and a control device for setting an allowable maximum inter-terminal voltage and an allowable charging current at the time of charging of the secondary battery and controlling the charging from a power supply to the secondary battery,

• wherein when a normal temperature range ATj of a battery temperature T is set to 20 to 45° C. and a low-temperature range ATl of a battery temperature T is set to −30 to 0° C.,
• the negative electrode plate has a characteristic such that
• when characteristics of the negative electrode plate are compared in cases where the battery temperature T is within the normal temperature range ATj and within the low-temperature range ATl,
• reaction resistance Rr(T) caused in the negative electrode plate is higher in the low-temperature range ATl, and
• a ratio of the reaction resistance Rr(T) of the negative electrode plate in internal resistance R(T) of the secondary battery is larger in the low-temperature range ATl,
• wherein the battery control system includes:
• a voltage storage unit for storing an initial maximum inter-terminal voltage Vm0(T) allowed at an early use of the secondary battery in the maximum inter-terminal voltage Vm(T) for each battery temperature T;
• a resistance storage unit for storing initial internal resistance R0(T) caused at the early use of the secondary battery at least at a predetermined battery temperature Tja within the normal temperature range ATj;
• an electric current storage unit for storing the allowable charging current Im(T) for each battery temperature T;
• a difference obtaining unit for obtaining difference resistance ΔR(Tja) as a difference between normal internal resistance Rj(Tja) at the predetermined battery temperature Tja within the normal temperature range Atj in the internal resistance of the secondary battery at timing when the battery temperature T of the secondary battery becomes the predetermined battery temperature Tja and the corresponding initial internal resistance R0(Tja) at the predetermined battery temperature Tja stored in the resistance storage unit;
• and
• a maximum voltage calculating unit for, at least when the battery temperature T is within the low-temperature range ATl, setting the maximum inter-terminal voltage Vm(T) corresponding to the battery temperature T to a value obtained by adding a product of the difference resistance ΔR(Tja) and the allowable charging current Im(T) stored in the electric current storage unit to the initial maximum inter-terminal voltage Vm0(T) stored in the voltage storage unit.