WHAT IS CLAIMED IS;
1. A battery management system for optimizing an internal resistance of a
battery, the battery management system comprising:
a current measuring unit configured to measure a charge current of the battery;
a memory configured to store a plurality of voltage-current characteristic profiles; and
a control unit operably coupled to the current measuring unit and the memory, and configured to determine a reference profile from the plurality of voltage-current characteristic profiles based on a state of charge and a temperature of the battery, the reference profile including a start point, an end point, and a plurality of intermediate points disposed between the start point and the end point,
the control unit is further configured to:
determine the internal resistance of the battery based on the start point and the end point,
set one of the plurality of intermediate points as a reference point,
determine a reference resistance that is lower than the internal resistance based on the reference point and the end point, and
determine an optimal resistance that is larger than the internal resistance based on the charge current, the internal resistance, the reference resistance and a predetermined upper limit of charge current.
2. The battery management system according to claim 1, wherein the control

unit is further configured to determine the internal resistance by dividing a difference between a voltage of the start point and a voltage of the end point by a current of the end point, and
the voltage of the start point indicates an open-circuit voltage of the battery corresponding to the state of charge and the temperature of the battery.
3. The battery management system according to claim 2, wherein the current of the end point is equal to the upper limit of charge current.
4. The battery management system according to claim 1, wherein the control unit is further configured to determine the reference resistance based on the voltage of the reference point, the current of the reference point, the voltage of the end point and the current of the end point.
5. The battery management system according to claim 4, wherein the control unit is further configured to determine the reference resistance using the following Equation 1 where Iref denotes the current of the reference point, Vref denotes the voltage of the reference point, lend denotes the current of the end point, Vend denotes the voltage of the end point, and Rref denotes the reference resistance:
6. The battery management system according to claim 5, wherein the control

unit is further configured to determine the optimal resistance using the following Equation 2 where Rint denotes the internal resistance, Ichr denotes the charge current, and RoPt denotes the optimal resistance:
7. The battery management system according to claim 1, wherein the control unit is further configured to determine an intermediate point closest to the end point among the plurality of intermediate points as the reference point.
8. A battery pack comprising the battery management system according to any one of claims 1 to 7.
9. A method for optimizing an internal resistance of a battery, the method comprising:
determining a reference profile from a plurality of voltage-current characteristic profiles based on a state of charge and temperature of the battery, the reference profile including a start point, an end point, and a plurality of intermediate points disposed between the start point and the end point;
determining the internal resistance of the battery based on the start point and the end point;
setting one of the plurality of intermediate points as a reference point;
determining a reference resistance that is lower than the internal resistance based

on the reference point and the end point; and
determining an optimal resistance that is larger than the internal resistance based on the charge current, the internal resistance, the reference resistance and a predetermined upper limit of charge current of the battery.