Battery state-of-charge estimator

• US 7,443,139 B2
• Filed: 06/25/2003
• Issued: 10/28/2008
• Est. Priority Date: 07/12/2002
• Status: Expired due to Fees

• Current Assignee: Toyota Jidosha
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Mitsui, Masahiko, Nakayama, Yoshiyuki
• Primary Examiner(s): Ullah; Akm Enayet
• Assistant Examiner(s): PIGGUSH, AARON C
• Application Number:
  US10/519,573
• Publication Number:
  US 20050269991A1
• Time in Patent Office: 1,952 Days
• Field of Search: 320/132, 320/134, 320/153, 324/427, 324/429
• US Class Current: 320/134
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery ECU estimates the SOC by integrating the battery current measured by a current sensor, and the battery voltage V_nis measured by a voltage sensor, and the battery temperature T_nis measured by a thermometer if the fluctuation of the charging/discharging current is great. If the number m of estimations of SOC_nis m≦10, m is incremented. The battery internal resistance R_nis estimated from the measured battery temperature T_nby using a correlation map showing the correlation between the previously stored battery temperature T and the battery internal resistance R. An estimation charging/discharging current I_nis determined using the measured battery voltage V_n,the battery open voltage V_ocvn-1determined on the basis of the previously estimated charged state, and the estimated battery internal resistance R_n. The SOC_nis estimated by integrating the estimated charging/discharging current I_n. If the number m of estimations of the SOC_nis m=10, the number m of estimations is changed to 0. The charging/discharging current i_nis measured by a current sensor. The battery internal resistance R_nis calculated from the battery voltage V_nand the charging/discharging current i_n. The battery temperature T_nis also measured, and the T-R correlation map is corrected

Claims

1. A battery state-of-charge estimator comprising:

a voltage detector unit which detects a voltage of a battery;

an internal resistance estimator unit which estimates an internal resistance of the battery;

an estimated charging/discharging current calculator unit which calculates an estimated charging/discharging current of the battery based on the internal resistance of the battery determined by the internal resistance estimator unit, the voltage of the battery, and an open voltage of the battery;

an SOC estimator unit which estimates a state of charge SOC of the battery based on the estimated charging/discharging current determined by the estimated charging/discharging current calculator unit;

an open voltage calculator unit which sets the detected voltage of the battery as the open voltage of the battery at an initial calculation of the charging/discharging current and, after the initial calculation, calculates the open voltage of the battery based on the SOC which is previously estimated, and

a current detection abnormality detector unit which compares the measured charging/discharging current value which is detected by the current detector which detects the charging/discharging current of the battery and the estimated charging/discharging current value which is determined by one of the estimated charging/discharging current calculator unit, the first charging/discharging current calculator unit, and the second charging/discharging current calculator unit, and determines that the current detector unit is abnormal when a difference between the current values is greater than a predetermined difference and that the current detector unit is normal when the difference is a predetermined value or smaller,

wherein the estimated charging/discharging current calculator unit, a first charging/discharging current calculator unit, or a second charging/discharging current calculator unit calculates the estimated charging/discharging current of the battery based on the internal resistance of the battery, the voltage of the battery, the open voltage of the battery, and a polarization voltage, and

wherein the SOC is estimated based on the estimated charging/discharging current value when the current detection abnormality detector unit determines that the current detector unit is abnormal and the SOC is estimated using the measured charging/discharging current value when the current detection abnormality detector unit determines that the current detector unit is normal.

2. A battery state-of-charge estimator according to claim 1, wherein SOC estimator unit periodically estimates the SOC at a predetermined interval.

3. A battery state-of-charge estimator according to claim 1, further comprising:

a current detector unit which detects a charging/discharging current of the battery;

a first battery full-capacity calculator unit which determines a full capacity of the battery based on the SOC which is estimated by the SOC estimator unit and an integrated value of the charging/discharging current of the battery which is detected by the current detector unit during the estimation of the SOC; and

a second SOC estimator unit which estimates a state of charge of the battery based on the full capacity of the battery which is obtained by the first battery full-capacity calculator unit and the measured charging/discharging current of the battery which is detected by the current detector unit.

4. A battery state-of-charge estimator according to claim 3, further comprising:

a second battery full-capacity calculator unit which determines a full capacity of the battery based on the SOC which is estimated by the first SOC estimator unit or the second SOC estimator unit and an integrated value of the charging/discharging current of the battery which is detected by the current detector unit during the estimation of the SOC, and

a second SOC estimator unit which estimates a state of charge of the battery based on the full capacity of the battery which is obtained by the second battery full-capacity calculator unit and the measured charging/discharging current of the battery which is detected by the current detector unit.

5. A battery state-of-charge estimator according to claim 3, further comprising:

a remaining capacity detector unit which detects a remaining capacity of each individual cell within the battery; and

a remaining energy calculator unit which detects a minimum remaining capacity based on the remaining capacity of each individual cell which is obtained from the remaining capacity detector unit and calculates an amount of remaining energy of the battery based on the minimum remaining capacity.

6. A battery state-of-charge estimator according to claim 1, wherein

in consideration of on an environmental temperature of the battery, one of the measured charging/discharging current value which is detected by the current detector unit which detects the charging/discharging current of the battery and the estimated charging/discharging current value which is determined by one of the estimated charging/discharging current calculator unit, the first charging/discharging current calculator unit, and the second charging/discharging current unit is selected and

the SOC is estimated based on the selected charging/discharging current value.

7. A battery state-of-charge estimator according to claim 1, further comprising:

a charging/discharging prohibiting unit which prohibits charging and discharging of the battery when the charging/discharging current of the battery considering the polarization voltage exceeds a predetermined value.

8. A battery state-of-charge estimator according to claim 3, wherein

the temperature detector unit is placed in the battery, on a surface of the battery, or near the surface of the battery.

9. A battery state-of-charge estimator according to claim 3, wherein

at least one of the SOC estimator unit, the second SOC estimator unit, and a third SOC estimator unit periodically estimates the SOC at a predetermined interval.