Method and system for estimating state of health of battery set

• US 9,411,019 B2
• Filed: 12/16/2013
• Issued: 08/09/2016
• Est. Priority Date: 12/16/2013
• Status: Active Grant

• Current Assignee: Automotive Research & Testing Center
• Original Assignee: Automotive Research & Testing Center
• Inventors: Hwang, Bo-Han, Weng, Kuo-Liang, Lin, Deng-He
• Primary Examiner(s): Yi, Roy Y
• Application Number:
  US14/108,318
• Publication Number:
  US 20150168498A1
• Time in Patent Office: 967 Days
• US Class Current: 1/1
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health

Abstract

A method and a system for estimating the State of Health (SOH) of a battery set are disclosed. The method utilizes a discrete quantization algorithm to estimate the SOH of the battery set, wherein the voltage standard deviations are calculated according to the loop voltages of the battery cells, and comparing the rated discharge capacity with the voltage standard deviations for estimating the SOH of the battery set.

Claims

1. A method for estimating a State of Health (SOH) of a battery set, comprising:

a measuring step, for repeatedly measuring a plurality of loop voltages of a plurality of battery cells of the battery set by a plurality of distinct discharge capacities of a predetermined sampling condition;

a discretization step, for statistical-distributed-calculating the loop voltages of the battery cells according to a standard deviation formula, to get a plurality of voltage standard deviations, wherein each of the voltage standard deviations corresponding to each of the battery cells;

a differential step, for getting a discrete curve according to the discharge capacities and the voltage standard deviations, to calculate a standard-deviation-trough-value of the discrete curve by using a differential formula;

an estimating step, for calculating a rated discharge capacity of the battery set and a discharge quantity corresponding to the standard-deviation-trough-value according to a SOH calculating formula, to get the SOH of the battery set; and

wherein the SOH calculating formula in the estimating step is k(AH_valley)/(AH_original)×

100%, and k is a constant of proportionality, AH_valley is the discharge quantity corresponding to the standard-deviation-trough-value, and AH_original is the rated discharge capacity of the battery set.

2. The method of claim 1, wherein the predetermined sampling condition of the measuring step is to measure the loop voltages of the battery cells of the battery set at every hundred milliampere-hour(mAh).

3. The method of claim 2, wherein the discharge capacities of the battery set in the measuring step are obtained by a coulomb counting method.

4. The method of claim 3, wherein the standard deviation formula in the differential step is 1/n Σ

_i=1ⁿ X_i−

u_i/Z_i, and X_i is a random variable of the loop voltages, u_i is a mean value corresponding to the loop voltages of each of the battery cells, Z_i is a standard score of values of the loop voltages of each of the battery cells, and n is a total number of the loop voltages corresponding to each of the battery cells.

5. The method of claim 4, wherein the differential formula in the differential step is dσ

(AH)/dAH, and σ

(AH) is a function of the voltage standard deviations to the discharge capacities, AH are the discharge capacities.

6. A system for estimating a State of Health (SOH) of a battery set, comprising:

the battery set, including a plurality of battery cells;

a voltage detecting circuit electrically connected to the battery set, the voltage detecting circuit repeatedly measures a plurality of loop voltages of the battery cells of the battery set by a plurality of distinct discharge capacities of a predetermined sampling condition;

a current detecting circuit electrically connected to the battery set, the current detecting circuit measures discharge current of the battery set for calculating the discharge capacities; and

an operating module electrically connected to the battery set, the operating module comprises;

a discretization unit, which statistical-distributed-calculates the loop voltages of the battery cells according to a standard deviation formula, to get a plurality of voltage standard deviations, wherein each of the voltage standard deviations respectively corresponding to each of the battery cells;

a differential unit, which gets a discrete curve according to the discharge capacities and the voltage standard deviations, to calculate a standard-deviation-trough-value of the discrete curve by using a differential formula; and

a SOH calculating unit, which calculates a rated discharge capacity of the battery set and a discharge quantity corresponding to the standard-deviation-trough-value according to a SOH calculating formula, to get the SOH of the battery set;

wherein the SOH calculating formula is k(AH_valley)/(AH_original)×

100%, and k is a constant of proportionality, AH_valley is the discharge quantity corresponding to the standard-deviation-trough-value, AH_original is the rated discharge capacity of the battery set.

7. The system of claim 6, wherein the predetermined sampling condition is to measure the loop voltages of the battery cells of the battery set at every hundred milliampere-hour(mAh).

8. The system of claim 7, wherein the discharge capacities of the battery set obtained by a coulomb counting method.

9. The system of claim 8, wherein the standard deviation formula is 1/n Σ

_i=1ⁿ X_i−

u_i/Z_i, and X_i is a random variable of the loop voltages, u_i is a mean value corresponding to the loop voltages of each of the battery cells, Z_i is a standard score of values of the loop voltages of each of the battery cells, and n is a total number of the loop voltages corresponding to each of the battery cells.

10. The system of claim 9, wherein the differential formula is dσ

(AH)/dAH;

σ

(AH) is a function of the voltage standard deviations to the discharge capacities, and AH are the discharge capacities.

11. The system of claim 6, further comprising:

a memory module electrically connected to the operating module;

a display module electrically connected to the operating module, for displaying the SOH of the battery set; and

a load electrically connected to the voltage detecting circuit and the current detecting circuit, is utilized to make the load, the battery set, the voltage detecting circuit and the current detecting circuit connected in series and thereby forms a loop.