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

Patent metadata

Field	Value
Publication number	US-9453887-B2
Application number	US-201414503809-A
Country	US
Kind code	B2
Filing date	Oct 1, 2014
Priority date	Nov 25, 2013
Publication date	Sep 27, 2016
Grant date	Sep 27, 2016

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.

First claim

The invention claimed is:

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.

Assignees

• Primearth Ev Energy Co Ltd
• Toyota Motor Co Ltd

Inventors

• KOBA Daisuke
• Takeda Sachio
• Ichikawa Koichi
• Takahashi Yasuhiro
• Habu Hirochika

Classifications

• Y02W30/84

  Recycling of batteries or fuel cells · CPC title

• Y10T29/49004

  including measuring or testing of device or component part · CPC title

• H01M10/443

  in response to temperature · CPC title

• H01M10/54

  Reclaiming serviceable parts of waste accumulators · CPC title

• G01R31/3627 Primary

  Physics · mapped topic