Method of selecting used secondary battery and method of manufacturing battery pack

• US 9,453,887 B2
• Filed: 10/01/2014
• Issued: 09/27/2016
• Est. Priority Date: 11/25/2013
• Status: Active Grant

• Current Assignee: Primearth EV Energy Company Limited (Toyota Motor Corporation), Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Primearth EV Energy Company Limited (Toyota Motor Corporation), Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Habu, Hirochika, Koba, Daisuke, Takeda, Sachio, Ichikawa, Koichi, Takahashi, Yasuhiro
• Primary Examiner(s): Berhanu, Samuel
• Application Number:
  US14/503,809
• Publication Number:
  US 20150145521A1
• Time in Patent Office: 727 Days
• Field of Search: 324/430
• US Class Current: 1/1
• CPC Class Codes: G01R 31/385 Arrangements for measuring battery or accumulator variables for monitoring G01R31/382
• CPC Class Codes: H01M 10/345 Gastight metal hydride accumulators
• CPC Class Codes: H01M 10/4207 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/443 in response to temperature
• CPC Class Codes: H01M 10/54 Reclaiming serviceable parts of waste accumulators
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02W 30/84 Recycling of batteries or fuel cells
• CPC Class Codes: Y10T 29/49004 including measuring or testing of device or component part

Abstract

A method of selecting a used secondary battery includes an internal resistance measurement step of measuring a specific internal resistance (second internal resistance) at a specific battery temperature (second battery temperature) of each of used secondary batteries, and a selection step of selecting a used secondary battery or batteries having the specific internal resistance (second internal resistance) smaller than a preset threshold from the plurality of used secondary batteries whose specific internal resistances (second internal resistance) have been measured in order to exclude an electrode-deteriorated battery from the used secondary batteries.

Claims

1. A method of selecting a used secondary battery that is reusable from a plurality of collected used secondary batteries, comprising:

an internal resistance measurement step of measuring a specific internal resistance at a specific battery temperature of each of the used secondary batteries; and

a selection step of selecting used secondary batteries having the specific internal resistance smaller than a preset threshold from the plurality of used secondary batteries whose specific internal resistances have been measured;

the threshold being set by a process including a step of measuring the specific internal resistance of each of a plurality of sample secondary batteries that are used secondary batteries prepared for determining the threshold;

continuously discharging each of the sample secondary batteries at a battery temperature equivalent to the specific battery temperature, and measuring a minimum voltage in the each sample secondary battery during a period of the discharge;

plotting the specific internal resistances and the minimum voltages of each of the sample secondary batteries to create a correlation chart;

determining a regression line of sample secondary batteries including at least all of the sample secondary batteries having a specific internal resistance not exceeding a reference value among the plurality of sample secondary batteries in the correlation chart;

determining a lower limit line that is parallel to the regression line and shifted a predetermined value from the regression line to a side where the minimum voltage is lower in the correlation chart;

calculating a value obtained by dividing a ranking number of batteries in region of the plurality of sample secondary batteries in ascending order of the specific internal resistance by a total number of sample secondary batteries, wherein the batteries in region are contained in a region of the correlation chart where the specific internal resistance is larger than the reference value and the minimum voltage does not exceed the lower limit line;

specifying a battery having a smallest specific internal resistance out of the batteries contained in the region and having a calculated value exceeding a preset value; and

setting the specific internal resistance of the specified battery contained in the region as the threshold.

2. The method of selecting a used secondary battery according to claim 1, wherein the regression line is a regression line of sample secondary batteries having a specific internal resistance not exceeding the reference value, of the plurality of sample secondary batteries.

3. The method of selecting a used secondary battery according to claim 1, wherein the predetermined value for determining the lower limit line is one half of an allowable voltage difference between the used secondary batteries determined by a control device of a battery pack during use of the battery pack formed by the plurality of used secondary batteries.

4. The method of selecting a used secondary battery according to claim 1, wherein the specific battery temperature in the internal resistance measurement step is a temperature of 0°

C. or less.

5. The method of selecting a used secondary battery according to claim 1, wherein

the used secondary batteries are used nickel-metal hydride secondary batteries, and

the reference value is a value of 70% of the specific internal resistance a nickel-metal hydride secondary battery initially has.

6. A method of manufacturing a battery pack formed by combining a plurality of used secondary batteries, comprising:

a step of selecting a plurality of used secondary batteries from the plurality of used secondary batteries selected by the method of selecting a used secondary battery according to claim 1 such that a maximum difference between the specific internal resistances is within an allowable limit; and

an assembling step of forming a battery pack by electrically connecting the plurality of selected used secondary batteries.

7. A method of manufacturing a battery pack formed by combining a plurality of used secondary batteries, comprising:

a first internal resistance measurement step of measuring a first internal resistance at a first battery temperature that is a normal temperature of each of the used secondary batteries;

a second internal resistance measurement step of measuring a second internal resistance at a second battery temperature that is lower than the normal temperature of each of the used secondary batteries;

a first selection step of selecting used secondary batteries having the second internal resistance smaller than a preset threshold from the plurality of used secondary batteries whose second internal resistances have been measured;

a second selection step of selecting a plurality of used secondary batteries having a maximum difference between the first internal resistances not exceeding an allowable limit, as well as a maximum difference between the second internal resistances not exceeding the allowable limit, from the plurality of the used secondary batteries selected in the first selection step;

an assembling step of forming the battery pack by electrically connecting the plurality of the used secondary batteries selected in the second selection step,

the threshold being set by a process including a step of measuring the second internal resistance of each of a plurality of sample secondary batteries that are used secondary batteries prepared for determining the threshold;

continuously discharging each of the sample secondary batteries at a battery temperature equivalent to the second battery temperature, and measuring a minimum voltage in the each sample secondary battery during a period of the discharge;

plotting the second internal resistances and the minimum voltages of each of the sample secondary batteries to create a correlation chart;

determining a regression line of sample secondary batteries including at least all of the sample secondary batteries having a specific internal resistance not exceeding a reference value among the plurality of sample secondary batteries in the correlation chart;

determining a lower limit line that is parallel to the regression line and shifted a predetermined value from the regression line to a side where the minimum voltage is lower in the correlation chart;

calculating a value obtained by dividing a ranking number of batteries in region of the plurality of sample secondary batteries in ascending order of the second internal resistance by a total number of the sample secondary batteries, wherein the batteries in region are contained in a region of the correlation chart where the second internal resistance is larger than the reference value and the minimum voltage does not exceed the lower limit line;

specifying a battery having a smallest second internal resistance out of the batteries contained in the region and having a calculated value exceeding a preset value; and

setting the second internal resistance of the specified battery contained in the region as the threshold.

8. The method of manufacturing a battery pack according to claim 7, wherein the second battery temperature in the second internal resistance measurement step is a temperature of 0°

C. or less.

9. The method of manufacturing a battery pack according to claim 7, wherein

the used secondary batteries are used nickel-metal hydride secondary batteries, and

the reference value is a value of 70% of the second internal resistance a nickel-metal hydride secondary battery initially has.