Method for Measuring SOC of a Battery in a Battery Management System and the Apparatus Thereof
According to an embodiment of this invention, a method for measuring SOC (State Of Charge) of a battery comprises the steps of: obtaining current data, voltage data and temperature by measuring the current, the voltage and the temperature of a battery; calculating SOCi (State Of Charge based on current) by accumulating the current data; calculating open circuit voltage by using an equivalent circuit model which simply presents the current data, the voltage data and the battery through an electric circuit; calculating SOCv (State Of Charge based on voltage) by using the temperature data and the open circuit voltage; and choosing at least one of the SOCi and the SOCv as SOC of the battery by using the SOCi and the SOCv based on the judgment on the current state of the battery for a certain time interval.
1 . A method for measuring SOC of a battery, comprising:
obtaining current data, voltage data and temperature data by measuring current, voltage and temperature of the battery;
calculating SOCi (State Of Charge based on current) by accumulating the current data;
calculating OCV (Open Circuit Voltage) using an equivalent circuit model in which the current data, the voltage data and the battery are simply expressed by an electric circuit;
calculating SOCv (State Of Charge based on voltage) using the temperature data and the OCV; and
judging a current state of the battery for a desired period of time, and setting up the SOC of the battery using at least one of the SOCv and the SOCi.
2 . The method of claim 1 , wherein the calculating of OCV using an equivalent circuit model in which the current data, the voltage data and the battery are simply expressed by an electric circuit comprises:
Filtering the current data and the voltage data using a low pass filter;
Calculating a parameter used in the equivalent circuit model by applying the filtered current data and voltage data to the equivalent circuit model and an adaptive digital filter; and
calculating the OCV using the parameter.
3 . The method of claim 2 , wherein the low pass filter is a third order low pass filter.
4 . The method of claim 2 , wherein the equivalent circuit model is expressed by an electric circuit using a resistance parameter R, a current parameter I, a capacitor parameter C, a terminal voltage parameter V and VOC parameter Vo.
5 . The method of claim 2 , wherein a value of the parameter used in the equivalent circuit model is renewed by the adaptive digital filter.
6 . The method of claim 1 , wherein the judging of the current state of the battery for the desired period of time, and setting of the SOC of the battery using at least one of the SOCv and the SOCi comprises:
setting up the SOCv to the SOC of the battery, if the battery is in a low current state for the desired period of time; and
setting up the SOCv to the SOC of the battery, if the battery is not in a low current state for the desired period of time.
7 . The method of claim 6 , wherein the desired period of time is 20˜60 seconds, and the low current criteria is 2A.
8 . The method of claim 1 , wherein the calculating of the OCV using the equivalent circuit model in which the current data, the voltage data and the battery are simply expressed by the electric circuit comprises
calculating the OCV using an integration model of the equivalent circuit model in which the current data, the voltage data and the battery are simply expressed by the electric circuit.
9 . An apparatus for measuring SOC of a battery, comprising:
a battery information obtaining part that measures current, voltage and temperature of the battery and obtains current data, voltage data and temperature data;
a current accumulating part that calculates SOCi by accumulating the current data;
a OCV calculating part that calculates OCV using an equivalent circuit model in which the current data, the voltage data and the battery are simply expressed by an electric circuit;
a SOCv estimating part that estimates SOCv using the temperature data and the OCV; and
a SOC setting part that judges a current state of the battery for a desired period of time, and sets up the SOC of the battery using at least one of the SOCv and the SOCi.
10 . The apparatus of claim 9 , further comprising a low pass filtering part that filters the current data and the voltage data using a low pass filter,
wherein the OCV calculating part applies the current data and the voltage data filtered by the low pass filtering part to the equivalent circuit model and an adaptive digital filter, calculates a parameter used in the equivalent circuit model and then calculates the OCV using the parameter.
11 . The apparatus of claim 10 , wherein the low pass filter is a third order low pass filter.
12 . The apparatus of claim 10 , wherein the equivalent circuit model is expressed by an electric circuit using a resistance parameter R, a current parameter I, a capacitor parameter C, a terminal voltage parameter V and VOC parameter Vo.
13 . The apparatus of claim 10 , wherein the adaptive digital filter renews a value of the parameter using in the equivalent circuit model, continuously.
14 . The apparatus of claim 9 , wherein the SOC setting part sets up the SOCv to the SOC of the battery, if the battery is in a low current state for the desired period of time, and also sets up the SOCi to the SOC of the battery in other case.
15 . The apparatus of claim 14 , wherein the desired period of time is 2060 seconds, and the low current criteria is 2A.
16 . The apparatus of claim 9 , wherein the OCV calculating part calculates the OCV through an integration model of the equivalent circuit model.
17 . A computer-readable recording medium which records a program for executing the method of claim 1 .