METHOD OF SELECTING USED SECONDARY BATTERY AND METHOD OF MANUFACTURING BATTERY PACK
First Claim
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.
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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.
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Citations
9 Claims
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1. A method of selecting a used secondary battery that is reusable from a plurality of collected used secondary batteries, comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of manufacturing a battery pack formed by combining a plurality of used secondary batteries, comprising:
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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. - View Dependent Claims (8, 9)
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Specification