A battery resistance estimation apparatus comprising: a memory unit which stores a resistance lookup table in which resistance data is recorded according to a state of charge-temperature, SOC-T, condition of a battery; and a control unit, wherein the control unit includes: a resistance accumulation calculation unit which is configured to measure I-V data while the battery is charged/discharged during an operation cycle, calculate resistances by dV/dI repeatedly on a periodic basis in the operation cycle, and store the resistances in the memory unit, wherein the resistances for the operation cycle are accumulated and stored by the SOC-T condition; and a resistance data update unit which is configured, for the SOC-T conditions, to calculate a weighted average of a new resistance data according to the SOC-T condition and previously stored resistance data according to the SOC-T condition, and update the resistance data according to the SOC-T condition to the weighted average, wherein the new resistance data is an average of the resistances stored in the memory unit for the operation cycle for the SOC-T condition, or an average of a maximum and a minimum of the resistances stored in the memory unit for the operation cycle for the SOC-T condition, or a maximum of the resistances stored in the memory unit for the operation cycle for the SOC-T condition. a memory unit which stores a resistance lookup table in which resistance data is recorded according to a state of charge-temperature, SOC-T, condition of a battery; and a control unit, wherein the control unit includes: a resistance accumulation calculation unit which is configured to measure I-V data while the battery is charged/discharged during an operation cycle, calculate resistances by dV/dI repeatedly on a periodic basis in the operation cycle, and store the resistances in the memory unit, wherein the resistances for the operation cycle are accumulated and stored by the SOC-T condition; and a resistance data update unit which is configured, for the SOC-T conditions, to calculate a weighted average of a new resistance data according to the SOC-T condition and previously stored resistance data according to the SOC-T condition, and update the resistance data according to the SOC-T condition to the weighted average, wherein the new resistance data is an average of the resistances stored in the memory unit for the operation cycle for the SOC-T condition, or an average of a maximum and a minimum of the resistances stored in the memory unit for the operation cycle for the SOC-T condition, or a maximum of the resistances stored in the memory unit for the operation cycle for the SOC-T condition. a resistance accumulation calculation unit which is configured to measure I-V data while the battery is charged/discharged during an operation cycle, calculate resistances by dV/dI repeatedly on a periodic basis in the operation cycle, and store the resistances in the memory unit, wherein the resistances for the operation cycle are accumulated and stored by the SOC-T condition; and a resistance data update unit which is configured, for the SOC-T conditions, to calculate a weighted average of a new resistance data according to the SOC-T condition and previously stored resistance data according to the SOC-T condition, and update the resistance data according to the SOC-T condition to the weighted average, wherein the new resistance data is an average of the resistances stored in the memory unit for the operation cycle for the SOC-T condition, or an average of a maximum and a minimum of the resistances stored in the memory unit for the operation cycle for the SOC-T condition, or a maximum of the resistances stored in the memory unit for the operation cycle for the SOC-T condition.