Method for grouping unit cells using pattern matching technology of impedance spectrum

• US 6,674,287 B2
• Filed: 07/30/2002
• Issued: 01/06/2004
• Est. Priority Date: 09/20/2001
• Status: Active Grant

• Current Assignee: Korea Kumho Petrochemical Co Limited (Korea Kumho Petrochemical)
• Original Assignee: Korea Kumho Petrochemical Co Limited (Korea Kumho Petrochemical)
• Inventors: Ryu, Sang-Hyo, Sung, Hyun-Kyung, Jang, Jee-Hwan
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US10/208,608
• Publication Number:
  US 20030052689A1
• Time in Patent Office: 525 Days
• Field of Search: 324/426, 324/430, 324/431, 324/434, 320/116, 320/117, 320/110, 320/106
• US Class Current: 324/430
• CPC Class Codes: H01M 10/482 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A method for grouping unit cells of a similar impedance spectrum uses pattern matching technology to optimize the performance of a battery pack made of primary or secondary batteries as the unit cells connected in series, in parallel or in combination of them. To make an optimal battery pack with unit cells of a different internal characteristic, the method includes measuring the impedance spectrum of the individual unit cell in a wide frequency region at the same temperature and in the same state of charge (SOC), digitizing the difference in impedance spectrum among the unit cells into a relative value using the pattern matching technology, and selecting unit cells of a most similar impedance spectrum (i.e., a smallest relative difference in impedance spectrum) to make a battery pack.

Claims

1. A method for grouping unit cells, which is analyzing the impedance spectrum of the individual unit cells using a pattern matching technology and selecting cells of a similar impedance spectrum in groups to make an optimal battery pack, the method comprising:

(a) measuring the impedance spectrum of the individual unit cell in a predetermined frequency region at the same temperature and in the same state of charge;

(b) digitizing the difference in impedance spectrum among the unit cells into a relative value using the pattern matching technology; and

(c) selecting two or more unit cells having the smallest difference in the digitalized impedance spectrum.

2. The method as claimed in claim 1, wherein the pattern matching technology in step (b) comprises using distance measurement between the impedance spectrums to determine similarity of the impedance spectra.

3. The method as claimed in claim 2, wherein the distance measurement between the impedance spectra comprises calculations of Euclidean distance, square of Euclidean distance or Manhattan distance.

4. A method for grouping unit cells, comprising:

(a) measuring complex impedance values of electrochemical power sources at different frequencies in a predetermined frequency region at the same temperature and in the same state of charge;

the electrochemical power sources being produced by a same manufacturing process and having a different internal characteristic;

(b) calculating a similarity in impedance spectrum curves among the power sources measured in the step (a) using a pattern matching technology; and

(c) selecting two or more electrochemical power sources having the similarity in impedance spectrum curves calculated in the step (b) and sorting them in groups of two or more to make an excellent battery pack.

5. The method as claimed in claim 4, wherein the electrochemical power sources comprise primary battery, fuel cell, secondary battery including lithium-ion battery, lithium-ion polymer, lithium polymer, NiCd, NiMH, or lead-acid battery.

6. The method as claimed in claim 4, wherein the measurement in step (a) comprises a multi-sine wave Fourier transformation impedance spectrum measurement.

7. The method as claimed in claim 4, wherein the measurement in step (a) comprises a transient response Laplace transformation impedance spectrum measurement.

8. The method as claimed in claim 4, further comprising:

(d) constructing a tree structure of the electrochemical power sources having the similarity in impedance spectrum using the pattern matching technology based on clustering.

9. The method as claimed in claim 8, wherein the power sources in a lower branch of the tree structure having a similar relative difference in impedance spectrum are sorted in a group for one battery pack.

10. The method as claimed in claim 4, wherein the pattern matching technology in step (b) comprises using distance measurement between the impedance spectra to determine similarity of the impedance spectra.

11. The method as claimed in claim 4, wherein the similarity of the impedance spectra are expressed in a matrix for comparison so as to determine a similarity in impedance spectrum among the power sources.

12. The method as claimed in claim 10, wherein the distance measurement between the impedance spectra comprises calculations of Euclidean distance, square of Euclidean distance or Manhattan distance.