METHOD AND DEVICE FOR DETERMINING BATTERY DISCHARGE CAPABILITY, AND POWER SUPPLY SYSTEM

• US 20090027007A1
• Filed: 07/08/2008
• Published: 01/29/2009
• Est. Priority Date: 01/12/2006
• Status: Active Grant

• Current Assignee: Furukawa Electric Company Limited
• Original Assignee: Furukawa Electric Company Limited
• Inventors: IWANE, Noriyasu, FUJIMURA, Koji, SUGIMURA, Takezo
• Granted Patent: US 7,764,049 B2
• Time in Patent Office: Days
• US Class Current: 320/129
• CPC Class Codes: G01R 31/3647 for determining the ability of a battery to perform a critical function, e.g. cranking
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

Regarding a method for determining battery discharge capability of the present invention, the optimum state vector X is estimated by extended Kalman filter operation. Using the estimated state vector X, element parameters of an equivalent circuit are renewed to the optimum (step S7). Furthermore, based on the equivalent circuit 21 using the renewed element parameters, at the time of discharging with a predetermined current pattern from a battery 12, a voltage drop ΔV is estimated (step S8). Therefore the discharge capacity of the battery 12 is determined (step S9).

Claims

1. A method for determining battery discharge capability based on an equivalent circuit of a battery, which comprises the steps of:

setting a state vector, which has elements of at least element parameters and a predetermined function of the element parameters of the equivalent circuit;

measuring for evaluating current and voltage of the battery;

estimating the state vector, using the measured current value and the voltage value, and state of charge (SOC) calculated by a predetermined SOC calculating method as observed values;

applying the element parameters as elements of the estimated state vector to the equivalent circuit to estimate the voltage value of the battery at the time of discharging under a predetermined current pattern; and

comparing the estimated voltage value with a predetermined voltage tolerance to determine the discharge capability of the battery.

2. The method for determining battery discharge capability of claim 1, wherein the state vector is estimated using secondary observed values calculated from the current, the voltage and the state of charge (SOC) of the battery.

3. The method for determining battery discharge capability of claim 1 or 2, wherein impedance for one or more frequencies is added into elements of the observed values;

and

the state vector is estimated using the measured current value and the voltage value, the SOC calculated by the SOC calculating method, and the impedance for one or more frequencies which is calculated by a predetermined impedance calculating method.

4. The method for determining battery discharge capability of claim 3, wherein the impedance calculating method measures the current and the voltage at the time of discharging or charging a pulse current through the battery, evaluates each amplitude constituent corresponding to the one or more frequencies by Fourier expanding the measured current value and the voltage value respectively, and then calculates the impedance for one or more frequencies from the amplitude constituent.

5. The method for determining battery discharge capability of claim 3, wherein the impedance calculating method measures the current and the voltage at the time of power supplying to electric equipments from the battery, evaluates each amplitude constituent corresponding to the one or more frequencies by Fourier transforming the measured current value and the voltage value respectively, and then calculates the impedance for one or more frequencies from the amplitude constituent.

6. The method for determining battery discharge capability of claim 4 or 5, wherein the impedance calculating method calculates the impedance Zbat of the battery, for the impedance (as Zmes) evaluated by the Fourier expanding or the Fourier transforming, to remove also an affect of the impedance (as Zx) of the electric equipments parallel connected with the battery, by a relational expression:

1/Zmes=1/Zx+1/Zbat.

7. The method for determining battery discharge capability of any one of claims 1 to 5, and 6, wherein the element parameters carry out a predetermined correction calculation regarding at least either one from the current value/the temperature/the SOC of the battery.

8. The method for determining battery discharge capability of any one of claims 1 to 6, and 7, wherein the SOC calculating method uses at least either one from a stable OCV measured value/a current integrated value/an I/V (I-V:

current-voltage) characteristic of the battery.

9. A device for determining battery discharge capability to determine the discharge capability of the battery based on the equivalent circuit of the battery comprising:

a current sensor to determine the current of the battery;

a voltage sensor to determine the voltage of the battery; and

a control means to determine the discharge capability of the battery, in which the state vector, which has element parameters of the equivalent circuit and predetermined functions of the element parameters as elements, is estimated using the current value inputted through the current sensor, the voltage value inputted through the voltage sensor, and the SOC calculated by the predetermined calculating method, the voltage value of the battery at the time of discharging under the predetermined current is estimated applying the element parameters as the elements of the estimated state vector to the equivalent circuit, and then the estimated voltage value is compared with the predetermined voltage tolerance to determine the discharge capability of the battery.

10. The device for determining battery discharge capability of claim 9, wherein the control means adds the impedance for one or more frequencies into the elements of the observed values, and estimates the state vector using the current value and the voltage value inputted through the current sensor and the voltage sensor respectively, the SOC calculated by the SOC calculating method and the impedance for one or more frequencies calculated by the predetermined impedance calculating method.

11. The device for determining battery discharge capability of claim 10, which further comprises:

a discharge circuit or a charge circuit for discharging or charging a pulse current to the battery; and

the control means, in which the current value and the voltage value are inputted through the current sensor and the voltage sensor respectively at the time of discharging or charging the pulse current by the discharge circuit or the charge circuit, the current value and the voltage value are Fourier expanded or Fourier transformed respectively to evaluate each amplitude constituent corresponding to the one or more frequencies, and then the impedance for one or more frequencies is calculated from the each amplitude constituent.

12. A power supply system comprising the device for determining battery discharge capability of any one of claims 9 to 11.