Method and apparatus for estimating terminal voltage of battery, method and apparatus for computing open circuit voltage of battery, and method and apparatus for computing battery capacity

• US 20020145430A1
• Filed: 02/22/2002
• Published: 10/10/2002
• Est. Priority Date: 02/23/2001
• Status: Active Grant

• Current Assignee: Yazaki Corporation
• Original Assignee: Yazaki Corporation
• Inventors: Kawaguchi, Tomohiro, Arai, Youichi, Enomoto, Michito, Kamohara, Hideaki
• Granted Patent: US 6,624,636 B2
• Time in Patent Office: Days
• US Class Current: 324/426
• CPC Class Codes: B60K 6/22 characterised by apparatus, components or means specially adapted for HEVs
• CPC Class Codes: B60K 6/28 characterised by the electric energy storing means, e.g. batteries or capacitors
• CPC Class Codes: B60K 6/485 Motor-assist type
• CPC Class Codes: B60W 10/26 for electrical energy, e.g. batteries or capacitors
• CPC Class Codes: G01R 31/386 using test-loads
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y10S 903/904 Component specially adapted for hev
• CPC Class Codes: Y10S 903/907 Electricity storage, e.g. battery, capacitor

Abstract

A method and an apparatus for computing a charging state of a battery without being affected by an influence of polarization are provided. First computing means computes a voltage-current characteristic including the influence of the polarization during an decrease of a discharge current of the battery on the basis of a terminal voltage and discharge current measured while the battery carries out a constant load discharge with a current value large enough to cancel a charge-side polarization arisen in the battery at least just before the discharge. A second computing means shifts the voltage-current characteristic to a specific extent in the direction of a voltage coordinate axis. A residual voltage drop value in advance stored by storing means is added to a present estimated voltage value estimated by estimating means on the basis of the shifted voltage-current characteristic, thereby a present open circuit voltage of the battery is computed.

Claims

1. A method for estimating a terminal voltage of a battery comprising the steps of:

periodically measuring a terminal voltage and a discharge current of a battery that supplies an electric power to loads in a vehicle;

calculating a voltage-current characteristic expressing a correlation between the terminal voltage and the discharge current; and

estimating an estimated voltage that is an estimated terminal voltage of the battery in a constant load discharging state thereof from the voltage-current characteristic,

wherein when the battery carries out a constant load discharge with a current value large enough to cancel a charge-side polarization arisen in the battery at least just before the discharge, the voltage-current characteristic including an influence of a polarization is calculated from the terminal voltage and the discharge current of the battery, which are periodically measured while the discharge current of the constant load discharge decreases from the maximum current value,

the voltage-current characteristic including the influence of the polarization is shifted in the direction of a voltage coordinate axis so that a voltage value at a reference current value lower than the maximum current value in the voltage-current characteristic including the influence of the polarization agrees with a reference voltage value at the reference current value in the voltage-current characteristic, which does not include the influence of the polarization but depends only on a pure resistance component of the battery, and

a voltage value corresponding to a predetermined imaginary current value in the voltage-current characteristic including the influence of the polarization shifted in the direction of the voltage coordinate axis is estimated as a value of the estimated voltage.

2. The method for estimating a terminal voltage of a battery according to claim 1, wherein the voltage-current characteristic including the influence of the polarization is expressed by an approximate curve equation.

3. The method for estimating a terminal voltage of a battery according to claim 1 or 2, wherein the current value large enough to cancel a charge-side polarization arisen in the battery at least just before the discharge is set to be a predetermined large current value required to drive a maximum power consuming load independently out of the loads in the vehicle, which receive an electric power from the battery, and

after the discharge current of the battery starts decreasing from the predetermined large current value, while the discharge current of the battery is lower than the predetermined large current value and is decreasing up to a target current value that is higher than a maximum discharge current value when the loads in the vehicle except the maximum power consuming load are driven, a voltage-current characteristic including an influence of a polarization for the battery in an equilibrium state thereof and the voltage-current characteristic including the influence of the polarization are calculated from the periodically measured terminal voltage and discharge current of the battery.

4. A method for computing an open circuit voltage of a battery comprising the steps of:

periodically measuring a terminal voltage and a discharge current of a battery that supplies an electric power to loads in a vehicle;

calculating a voltage-current characteristic expressing a correlation between the terminal voltage and the discharge current;

estimating an estimated voltage that is an estimated terminal voltage of the battery in a constant load discharging state thereof from the voltage-current characteristic; and

computing an open circuit voltage of the battery corresponding to a terminal voltage of the battery in an equilibrium state thereof on the basis of the estimated voltage,

wherein when the battery carries out a constant load discharge with a current value large enough to cancel a charge-side polarization arisen in the battery at least just before the discharge, the voltage-current characteristic including an influence of a polarization is calculated from the terminal voltage and the discharge current of the battery, which are periodically measured while the discharge current of the constant load discharge decreases from the maximum current value,

the voltage-current characteristic including the influence of the polarization is shifted in the direction of a voltage coordinate axis so that a voltage value at a reference current value lower than the maximum current value in the voltage-current characteristic including the influence of the polarization agrees with a reference voltage value at the reference current value in the voltage-current characteristic, which does not include the influence of the polarization but depends only on a pure resistance component of the battery,

a difference value between the open circuit voltage value at the current being zero in the voltage-current characteristic not including the influence of the polarization and the estimated voltage value estimated on the basis of the voltage-current characteristic including the influence of the polarization shifted in the direction of the voltage coordinate axis is in advance calculated as a residual voltage drop value due to an influence of a residual polarization upon a completion of the discharge of the battery,

thereafter, whenever the battery carries out a constant load discharge with a current value large enough to cancel a charge-side polarization arisen in the battery at least just before the discharge, the voltage-current characteristic including the influence of the polarization is newly calculated from the terminal voltage and the discharge current of the battery periodically measured during the constant load discharge,

the newly calculated voltage-current characteristic including the influence of the polarization is shifted in the direction of a voltage coordinate axis so that a voltage value at the reference current value in the newly calculated voltage-current characteristic including the influence of the polarization agrees with the reference voltage value in the voltage-current characteristic not including the influence of the polarization when the voltage-current characteristic including the influence of the polarization is newly calculated,

a present estimated voltage is estimated on the basis of the newly calculated voltage-current characteristic including the influence of the polarization shifted in the direction of the voltage coordinate axis, and

a present open circuit voltage is computed by adding the residual voltage drop value to the present estimated voltage value.

5. The method for computing an open circuit voltage of a battery according to claim 4, wherein after the residual voltage drop value is calculated, whenever the battery carries out a constant load discharge with a current value large enough to cancel a charge-side polarization arisen in the battery at least just before the discharge, the voltage-current characteristic not including the influence of the polarization is calculated when the voltage-current characteristic including the influence of the polarization is newly calculated from the terminal voltage and the discharge current of the battery periodically measured during the constant load discharge.

6. The method for computing an open circuit voltage of a battery according to claim 4 or 5, wherein whenever the battery becomes in an equilibrium state thereof, the terminal voltage value of the battery measured in the equilibrium state thereof is obtained as a present open circuit voltage value,

a newest voltage-current characteristic not including the influence of the polarization is calculated from the terminal voltage and the discharge current of the battery, which are periodically measured when the battery carries out a constant load discharge with a current value large enough to cancel a charge-side polarization arisen in the battery at least just before the discharge starting from the equilibrium state,

a newest voltage-current characteristic including the influence of the polarization is calculated from the terminal voltage and the discharge current of the battery periodically measured while a discharge current of the constant load discharge, which the battery carries out with a current value large enough to cancel a charge-side polarization arisen in the battery at least just before the discharge starting from the equilibrium state, is decreasing from a predetermined large current value,

a newest residual voltage drop value is calculated on the basis of the obtained terminal voltage value and the newest voltage-current characteristic including the influence of the polarization, and

thereafter, the present open circuit voltage is computed on the basis of the newest residual voltage drop value and the newest voltage-current characteristic not including the influence of the polarization.

7. The method for computing an open circuit voltage of a battery according to claim 4 or 5, wherein the voltage-current characteristic including the influence of the polarization is expressed by an approximate curve equation.

8. The method for computing an open circuit voltage of a battery according to claim 4 or 5, wherein the current value large enough to cancel a charge-side polarization arisen in the battery at least just before the discharge is set to be a predetermined large current value required to drive a maximum power consuming load independently out of the loads in the vehicle, which receive an electric power from the battery, and

after the discharge current of the battery starts decreasing from the predetermined large current value, while the discharge current of the battery is lower than the predetermined large current value and is decreasing up to a target current value that is higher than a maximum discharge current value when the loads in the vehicle except the maximum power consuming load are driven, a voltage-current characteristic including an influence of a polarization for the battery in an equilibrium state thereof and the voltage-current characteristic including the influence of the polarization are calculated from the periodically measured terminal voltage and discharge current of the battery.

9. The method for computing an open circuit voltage of a battery according to claim 4 or 5, wherein whenever a present estimated voltage of the battery is estimated on the basis of the voltage-current characteristic including the influence of the polarization shifted in the direction of the voltage coordinate axis, the residual voltage drop value is revised in response to an inside or circumferential temperature of the battery upon the estimation and another inside or circumferential temperature of the battery when the voltage-current characteristic not including the influence of the polarization for the battery in the equilibrium state thereof is obtained, and the present open circuit voltage is computed from the revised residual voltage drop value.

10. A method for computing a battery capacity comprising the step of computing a present charging capacity of the battery from the present open circuit voltage computed by a method for computing an open circuit voltage of a battery according to claim 4 or 5.

11. An apparatus for estimating a terminal voltage of a battery executing the steps of:

periodically measuring a terminal voltage and a discharge current of a battery that supplies an electric power to loads in a vehicle;

calculating a voltage-current characteristic expressing a correlation between the terminal voltage and the discharge current; and

estimating an estimated voltage that is an estimated terminal voltage of the battery in a constant load discharging state thereof from the voltage-current characteristic,

the apparatus comprising;

first computing means for computing a voltage-current characteristic including an influence of a polarization from a terminal voltage and a discharge current of the battery periodically measured after the discharge current of the battery starts decreasing from a maximum current value, in a constant load discharge that the battery carries out with a current value large enough to cancel a charge-side polarization arisen in the battery at least just before the discharge,

second computing means for computing a voltage-current characteristic including an influence of a polarization shifted in the direction of a voltage coordinate axis so that a voltage value at a reference current value lower than the maximum current value in the voltage-current characteristic including the influence of the polarization computed by the first computing means agrees with a reference voltage value at the reference current value in the voltage-current characteristic, which does not include the influence of the polarization but depends only on a pure resistance component of the battery, when the first computing means computes the voltage-current characteristic including the influence of the polarization, and

estimating means for estimating a voltage value corresponding to a predetermined imaginary current value in the voltage-current characteristic including the influence of the polarization shifted in the direction of the voltage coordinate axis computed by the second computing means is estimated as a present value of the estimated voltage of the battery.

12. The apparatus for estimating a terminal voltage of a battery according to claim 11, wherein the first computing means computes the voltage-current characteristic including the influence of the polarization as an approximate curve equation.

13. The apparatus for estimating a terminal voltage of a battery according to claim 11 or 12, wherein the current value large enough to cancel a charge-side polarization arisen in the battery at least just before the discharge is a predetermined large current value required to drive a maximum power consuming load independently out of the loads in the vehicle, which receive an electric power from the battery, and

after the discharge current of the battery starts decreasing from the predetermined large current value, while the discharge current of the battery is decreasing up to a target current value that is higher than a maximum discharge current value when the loads in the vehicle except the maximum power consuming load are driven, the first computing means computes the voltage-current characteristic including the influence of the polarization from the periodically measured terminal voltage and discharge current of the battery.

15. The apparatus for computing an open circuit voltage of a battery according to claim 14, further comprising third computing means for computing the voltage-current characteristic not including the influence of the polarization from the periodically measured terminal voltage and discharge current of the battery, which carries out a constant load discharge with a current value large enough to cancel a charge-side polarization arisen in the battery at least just before the discharge, wherein the second computing means computes the voltage-current characteristic including the influence of the polarization shifted in the direction of a voltage coordinate axis on the basis of the voltage-current characteristic including the influence of the polarization computed by the first computing means and the voltage-current characteristic not including the influence of the polarization computed by the third computing means.

16. The apparatus for computing an open circuit voltage of a battery according to claim 14 or 15, further comprising:

judging means for judging whether or not the battery is in an equilibrium state thereof;

measuring means for measuring a terminal voltage of the battery when the battery is judged to be in an equilibrium state thereof by the judging means;

calculating means for calculating the newest residual voltage drop value by subtracting the present estimated voltage value estimated by the estimating means on the basis of the terminal voltage and discharge current of the battery, which is judged in an equilibrium state thereof by the judging means, periodically measured while the battery carries out the constant load discharge with a current value large enough to cancel a charge-side polarization arisen in the battery at least just before the discharge from a terminal voltage value of the battery most newly measured by the measuring means;

renewing means for renewing the residual voltage drop value stored by the storing means to the newest residual voltage drop value calculated by the calculating means; and

fourth computing means for computing a newest voltage-current characteristic not including the influence of the polarization on the basis of the terminal voltage and discharge current of the battery, which is judged in an equilibrium state thereof by the judging means, periodically measured while the battery carries out the constant load discharge with a current value large enough to cancel a charge-side polarization arisen in the battery at least just before the discharge.

17. The apparatus for computing an open circuit voltage of a battery according to claim 16, further comprising:

detecting means for detecting an inside or circumferential temperature of the battery; and

revising means for revising the residual voltage drop value stored by the storing means in response to an inside or circumferential temperature of the battery detected by the detecting means when the estimating means estimates the present estimated voltage and another inside or circumferential temperature of the battery detected by the detecting means when the renewing means renews the residual voltage drop value stored by the storing means to the newest residual voltage drop value calculated by the calculating means,

wherein the present open circuit voltage is computed by adding the residual voltage drop value revised by the revising means to the estimated voltage value estimated by the estimating means.

18. The apparatus for computing an open circuit voltage of a battery according to claim 14 or 15, wherein the first computing means computes the voltage-current characteristic including the influence of the polarization as an approximate curve equation.

19. The apparatus for computing an open circuit voltage of a battery according to claim 14 or 15, wherein the current value large enough to cancel a charge-side polarization arisen in the battery at least just before the discharge is a predetermined large current value required to drive a maximum power consuming load independently out of the loads in the vehicle, which receive an electric power from the battery, and

after the discharge current of the battery starts decreasing from the predetermined large current value, while the discharge current of the battery is decreasing up to a target current value that is higher than a maximum discharge current value when the loads in the vehicle except the maximum power consuming load are driven, the first computing means computes the voltage-current characteristic including the influence of the polarization from the periodically measured terminal voltage and discharge current of the battery.

20. An apparatus for computing a battery capacity comprising the apparatus for computing an open circuit voltage of a battery according to claim 14 or 15, wherein a present charging capacity of the battery is computed from the present open circuit voltage computed by the apparatus for computing an open circuit voltage of a battery.

14. An apparatus for computing an open circuit voltage of a battery executing the steps of:

periodically measuring a terminal voltage and a discharge current of a battery that supplies an electric power to loads in a vehicle;

calculating a voltage-current characteristic expressing a correlation between the terminal voltage and the discharge current;

estimating an estimated voltage that is an estimated terminal voltage of the battery in a constant load discharging state thereof from the voltage-current characteristic; and

computing an open circuit voltage of the battery corresponding to a terminal voltage of the battery in an equilibrium state thereof on the basis of the estimated voltage,

the apparatus comprising;

storing means for storing a residual voltage drop value due to a residual polarization upon a completion of the discharge when the battery carries out a constant load discharge with a current value large enough to cancel a charge-side polarization arisen in the battery at least just before the discharge;

first computing means for computing the voltage-current characteristic including an influence of a polarization from the periodically measured terminal voltage and discharge current of the battery after the discharge current of the battery starts decreasing from a maximum current value, during the constant load discharge that the battery carries out with a current value large enough to cancel a charge-side polarization arisen in the battery at least just before the discharge;

second computing means for computing a voltage-current characteristic including the influence of the polarization shifted in the direction of a voltage coordinate axis so that a voltage value at a reference current value lower than the maximum current value in the voltage-current characteristic including the influence of the polarization, which is computed by the first computing means, agrees with a reference voltage value at the reference current value in the voltage-current characteristic, which does not include the influence of the polarization but depends only on a pure resistance component of the battery, when the first computing means computes the voltage-current characteristic including the influence of the polarization; and

estimating means for estimating a present estimated voltage of the battery on the basis of the voltage-current characteristic including the influence of the polarization shifted in the direction of a voltage coordinate axis computed by the second computing means,

wherein the storing means in advance stores a difference value between

a value of the estimated voltage in advance estimated on the basis of an in advance computed voltage-current characteristic including the influence of the polarization sifted in the direction of a voltage coordinate axis, which is obtained by shifting the in advance computed voltage-current characteristic including the influence of the polarization in the direction of the voltage coordinate axis, so that a voltage value at the reference current value in the in advance computed voltage-current characteristic including the influence of the polarization agrees with the reference voltage value in the in advance computed voltage-current characteristic not including the influence of the polarization and

a value of the open circuit voltage at the current being zero in the in advance computed voltage-current characteristic not including the influence of the polarization,

and a present open circuit voltage is computed by adding the residual voltage drop value in advance stored by the storing means to the present estimated voltage value estimated by the estimating means.