Battery management system and a battery management method with a plurality of constant current charging stages for a battery
A battery management system and a battery management method. The battery management system includes a sensing unit to generate a sensing signal indicating a voltage and a current of a battery, a memory unit to store a reference charging map for constant-current charging using first to m th reference C-rates, and a control unit to determine a start value indicating a charge factor at a time point at which a charge command is received based on the sensing signal. The control unit generates first to m th reference charge functions corresponding to the first to m th reference C-rates in a one-to-one relationship from the reference charging map. When a charge cycle starts, the control unit controls a charge current supplied to the battery using the first to m th reference C-rates in a sequential order based on the sensing signal, the start value and the first to m th reference charge functions.
1 . A battery management system, comprising:
a sensing unit configured to generate a sensing signal indicating a voltage and a current of a battery;
a memory unit configured to store a reference charging map for constant-current charging using first to mth reference current rates (C-rates), wherein m is a natural number of 2 or greater; and
a control unit configured to determine a start value indicating a charge factor of the battery at a time point at which a charge command is received based on the sensing signal in response to the charge command being received,
wherein the control unit is configured to:
generate first to mth reference charge functions corresponding to the first to mth reference C-rates in a one-to-one relationship from the reference charging map, wherein each reference charge function indicates an adjustable charge factor increase and an adjustable changeover value as a function of the start value, wherein the charge factor increase is an amount of electrical energy stored in the battery that increases while the battery is charged at the corresponding reference C-rate of the reference charge function, and wherein the changeover value is a maximum charge factor at which the battery is charged at the corresponding reference C-rate of the reference charge function,
and
when a charge cycle including the constant-current charging starts:
for each reference charge function, determine the changeover value of the reference charge function based on the start value, and
control a charge current supplied to the battery using the first to mth reference C-rates in a sequential order based on the sensing signal, and the first to mth reference charge functions.
2 . The battery management system according to claim 1 , wherein the control unit is configured to replace the reference charging map stored in the memory unit with the first to mth reference charge functions.
3 . The battery management system according to claim 1 , wherein each reference charge function is a multi-degree polynomial function, and wherein the control unit is configured to generate the first to m th reference charge functions using a curve fitting technique.
4 . The battery management system according to claim 1 , wherein each reference charge function is a multi-degree polynomial function.
5 . The battery management system according to claim 1 , wherein the reference charging map includes first to mth reference arrays corresponding to the first to mth reference C-rates in a one-to-one relationship,
each reference array includes first to nth reference values and first to nth boundary values, wherein n is a natural number of 2 or greater, and
when i is a natural number between 2 and m, and j is a natural number between 1 and n:
a jth boundary value of the first reference array indicates an allowable limit value for constant-current charging with the first reference C-rate when the charge cycle starts at a time point at which the charge factor of the battery is equal to a jth reference value, and
a jth boundary value of an ith reference array indicates an allowable limit value for constant-current charging with an ith reference C-rate from a time point at which the charge factor of the battery reaches a jth boundary value of a i−1th reference array.
6 . The battery management system according to claim 5 , wherein the ith reference C-rate is smaller than a i−1th reference C-rate.
7 . The battery management system according to claim 5 , wherein when k is a natural number between 2 and n,
a kth reference value is larger than a k−1th reference value, and
a kth boundary value of the ith reference array is larger than a k−1th boundary value of the ith reference array.
8 . The battery management system according to claim 5 , wherein the control unit is configured to output a first control signal,
wherein the first control signal is a signal requesting to set the charge current to be equal to the first reference C-rate.
9 . The battery management system according to claim 8 , wherein z is an index value, and
when z is a natural number less than m, the control unit is configured to increase z by 1 and output a zth control signal in response to the charge factor of the battery reaching a zth changeover value by the charge current of a zth reference C-rate, and
wherein the zth control signal is a signal requesting to set the charge current to be equal to the zth reference C-rate.
10 . The battery management system according to claim 9 , wherein the control unit is configured to output a changeover signal requesting to change from the constant-current charging to constant-voltage charging with a threshold voltage in response to the charge factor of the battery reaching the mth changeover value by the charge current of the mth reference C-rate.
11 . The battery management system according to claim 10 , wherein the control unit is configured to set the threshold voltage to be equal to the voltage of the battery at a time point at which the charge factor of the battery reaches the mth changeover value.
12 . The battery management system according to claim 10 , wherein the control unit is configured to terminate the constant-voltage charging in response to the current of the battery reaching a threshold current during the constant-voltage charging.
13 . A battery pack comprising the battery management system according to claim 1 .
14 . An electric vehicle comprising the battery pack according to claim 13 .
15 . A battery management method, comprising:
generating first to mth reference charge functions corresponding to first to mth reference C-rates in a one-to-one relationship from a reference charging map for constant-current charging using the first to mth reference C-rates, and wherein each reference charge function indicates an adjustable charge factor increase and an adjustable changeover value as a function of a start value, wherein the charge factor increase is amount of electrical energy stored in the battery that increases while the battery is charged at the corresponding reference C-rate of the reference charge function, and wherein the changeover value is a maximum charge factor at which the battery is charged at the corresponding reference C-rate of the reference charge function;
in response to receiving a charge command, determining the start value which is the charge factor of the battery at a time point at which the charge command is received;
determining first to mth changeover values from the first to mth reference charge functions respectively based on the start value;
outputting a first control signal requesting to set a charge current to be equal to the first reference C-rate to start a charge cycle including the constant-current charging; and
wherein z is an index value, when z is a natural number that is less than m, increasing z by 1 and outputting a zth control signal requesting to set the charge current to be equal to the zth reference C-rate in response to the charge factor of the battery reaching the zth changeover value by the charge current of the zth reference C-rate.