Method for inspecting secondary battery, method for controlling secondary battery, and method for controlling power supply of electric vehicle

Abstract

This method for inspecting a secondary battery includes: a calculation step in which the impedance of a secondary battery is calculated in order to simulate a portion of the waveform of the impedance of the secondary battery using a polynomial expression and estimate a predetermined resistance value of the secondary battery; and an estimation step in which the impedance is used as a basis to estimate the predetermined resistance value. In the calculation step, a first impedance at a first frequency higher than the frequency of a region in which an imaginary part of the impedance is negative is calculated in a region in which the imaginary part of the impedance is positive, and a second impedance at a second frequency lower than the first frequency is calculated in the region in which the imaginary part of the impedance is negative. In the estimation step, a waveform of a polynomial intersecting a first axis at two or more points is simulated on the basis of the input first impedance and second impedance, and a predetermined resistance value is estimated on the basis of the value of the real part of the impedance at at least one of the two points.

Description

Secondary battery inspection method, secondary battery control method, and power supply control method for electric vehicles

[0001] The present invention relates to a secondary battery inspection method, a secondary battery control method, and a power supply control method for electric vehicles.

[0002] Conventionally, techniques for simulating the impedance waveform of a battery have been known in order to estimate a predetermined resistance value of a secondary battery (see Patent Documents 1 to 6). For example, Patent Document 1 discloses a configuration for calculating impedance in a region where the imaginary part of the battery impedance is negative, in order to simulate the impedance waveform of the battery using a Nyquist plot curve. Further, for example, Patent Document 2 discloses a configuration for calculating impedance in regions where the imaginary part of the battery impedance is negative and positive, in order to simulate the impedance waveform of the battery using an impedance Nyquist diagram.

[0003] Japanese Unexamined Patent Application Publication No. 2013-250223 International Publication No. 2019-215786 Japanese Patent No. 4477185 Japanese Unexamined Patent Application Publication No. 2022-125441 Japanese Unexamined Patent Application Publication No. 2018-190502 Japanese Unexamined Patent Application Publication No. 2018-121511

[0004] There is a demand for being able to calculate a predetermined resistance value of a secondary battery in a relatively short time while maintaining predetermined accuracy.

[0005] The present invention provides a method for inspecting a secondary battery, which involves simulating a portion of the impedance waveform of the secondary battery using a polynomial, estimating a predetermined resistance value of the secondary battery, and then inspecting the secondary battery. The secondary battery inspection method includes a calculation step of calculating the impedance of the secondary battery based on a predetermined frequency, and an estimation step of estimating a predetermined resistance value based on the calculated impedance. The polynomial is represented by a waveform using a first axis representing the real part of the impedance and a second axis that intersects the first axis and represents the imaginary part of the impedance. The calculation step calculates a first impedance at a first frequency that is relatively higher than the frequency in the region where the imaginary part of the impedance is negative, in the region where the imaginary part of the impedance is positive. The calculation step calculates a second impedance at a second frequency that is relatively lower than the first frequency, in the region where the imaginary part of the impedance is negative. The estimation step simulates the waveform of the polynomial that intersects the first axis at two or more points, based on two or more input impedances. The estimation step simulates the waveform of the polynomial based on the first impedance and the second impedance. The estimation step estimates a predetermined resistance value based on the real part of the impedance at at least one of the two points.

[0006] The present invention provides a method for controlling a secondary battery by simulating a portion of the impedance waveform of the secondary battery using a polynomial, estimating a predetermined resistance value of the secondary battery, and controlling the secondary battery. The secondary battery control method includes a calculation step of calculating the impedance of the secondary battery based on a predetermined frequency, an estimation step of estimating a predetermined resistance value based on the calculated impedance, and a control step of controlling the secondary battery based on the estimated predetermined resistance value. The polynomial is represented by a waveform using a first axis representing the real part of the impedance and a second axis intersecting the first axis and representing the imaginary part of the impedance. The calculation step configures the secondary battery to be at least dischargeable or rechargeable. The calculation step calculates a first impedance at a first frequency that is relatively higher than the frequency in the region where the imaginary part of the impedance is negative, in the region where the imaginary part of the impedance is positive. The calculation step calculates a second impedance at a second frequency that is relatively lower than the first frequency, in the region where the imaginary part of the impedance is negative. The estimation step simulates the waveform of the polynomial intersecting the first axis at two or more points based on two or more input impedances. The estimation step simulates the waveform of the polynomial based on the first impedance and the second impedance. The estimation step estimates a predetermined resistance value based on the real part of the impedance at at least one of the two points. The control step is configured to charge and discharge the secondary battery based on the estimated predetermined resistance value.

[0007] The power supply control method for electric vehicles of the present invention is used in an electric vehicle having electrical equipment and a power supply that supplies power to the electrical equipment. The power supply includes a secondary battery. The secondary battery is controlled by the secondary battery control method described above.

[0008] This invention calculates the impedance of a secondary battery by calculating the impedance in the region where the imaginary part is positive at a relatively higher frequency than the impedance in the region where the imaginary part is negative. Therefore, according to this invention, a predetermined resistance value of a secondary battery can be calculated in a relatively short time while maintaining a predetermined accuracy.

[0009] An electrical circuit relating to the control of the battery pack 100 and the calculation of its impedance Z according to the embodiment. A time chart relating to the calculation of the impedance Z of the battery pack 100 according to the embodiment. An electrical circuit relating to the control of the battery pack 100 and the calculation of its impedance Z according to a modified example of the embodiment. A time chart relating to the calculation of the impedance Z of the battery pack 100 according to a modified example of the embodiment. A simplified equivalent circuit representing the secondary battery 101 according to the embodiment. A schematic diagram showing the Nyquist plot relating to the impedance of the secondary battery 101 according to the embodiment. A schematic diagram showing the state in which the calculation result of the impedance Z of the secondary battery 101 is fitted to the Nyquist plot relating to the impedance of the secondary battery 101 according to the embodiment.

[0010] Embodiments for carrying out the present invention will be described with reference to the drawings. In the electrical circuit drawings, identical components are denoted by the same reference numerals.

[0011] (Configuration of the Embodiment) The calculation device, inspection device, and control device for the secondary battery 101 of the embodiment will be described as having a configuration for inspecting a battery pack 100 that includes a plurality of secondary batteries 101. In the calculation device and inspection device for the secondary battery 101 of the embodiment, it is also possible to configure it to inspect any secondary battery without removing the plurality of secondary batteries 101 from the battery pack 100. In the embodiment, when it is configured to inspect any secondary battery without removing the plurality of secondary batteries 101 from the battery pack 100, the electrical circuit for inspection and the arbitrary secondary battery 101 are connected by individual switches. The arbitrary secondary battery 101 may be the secondary battery 101 on the high-voltage side, the secondary battery 101 on the low-voltage side, or any other secondary battery 101 among the plurality of secondary batteries 101 connected in series. In the calculation device and inspection device for the secondary battery 101 of the embodiment, it is also possible to configure it to inspect all secondary batteries 101 or any secondary battery 101 with the plurality of secondary batteries 101 removed from the battery pack 100.

[0012] (Configuration of the battery pack 100) The configuration of the battery pack 100 will be explained with reference to Figure 1.

[0013] Figure 1 shows an electrical circuit for controlling the battery pack 100 and calculating the impedance Z of the embodiment.

[0014] The battery pack 100 can be used, for example, as a power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs). In other words, the battery pack 100 can be used as an on-board power source. The battery pack 100 may also be used, for example, as a stationary power source.

[0015] The battery pack 100 includes a plurality of secondary batteries 101. The plurality of secondary batteries 101 are installed in series. In adjacent secondary batteries 101, the positive electrode of one secondary battery 101 is connected to the negative electrode of the other secondary battery 101. The secondary batteries 101 are, for example, ternary lithium-ion secondary batteries. A thermistor 102 is attached to the secondary battery 101. The first wiring 103 is connected to the thermistor 102.

[0016] In this embodiment, a battery pack 100 containing multiple secondary batteries 101 is configured as the power source. Figure 1 shows three secondary batteries 101 as an example. The secondary batteries 101 included in the battery pack 100 may be, for example, 6, 12, 48, or 96. In this embodiment, a single secondary battery 101 may be configured as the power source.

[0017] (Charging and discharging of the battery pack 100) The charging and discharging of the battery pack 100 will be explained with reference to Figure 1.

[0018] (Charging of the battery pack 100) The battery pack 100 is configured, for example, as a power source to operate an on-board motor 1004 for driving an electric vehicle or electrical equipment. In this configuration, when charging the battery pack 100, the battery pack 100 is connected to the generator via a converter when the switch 1001 is switched. The charging of the battery pack 100 is controlled by the CCIC 200 and MPU 300. Based on the control of the CCIC 200 and MPU 300, the battery pack 100 is charged from the generator. That is, power is supplied from the generator to the battery pack 100. The battery pack 100 can also be charged by regenerative energy using the on-board motor 1004 during deceleration of the electric vehicle. The CCIC 200 is a Cell Controller Integrated Circuit. The MPU300 is a Micro Processing Unit.

[0019] In charging the battery pack 100, the battery pack 100 may be charged by an external charging device. The external charging device is a charging device installed in a commercial facility or residence and is used when the electric vehicle is stopped.

[0020] (Discharge of the battery pack 100) The battery pack 100 is configured, for example, as a power source to operate an on-board motor 1004 for driving an electric vehicle. In this configuration, when the battery pack 100 is discharged to the on-board motor 1004, the battery pack 100 is connected to the on-board motor 1004 via a relay 1002 and an inverter 1003 when a switch 1001 is switched. The discharge of the battery pack 100 is controlled by the CCIC 200 and the MPU 300. Based on the control of the CCIC 200 and the MPU 300, the battery pack 100 is discharged to the on-board motor 1004. That is, power is supplied from the battery pack 100 to the on-board motor 1004.

[0021] The battery pack 100 may be configured, for example, as a power source for operating electrical equipment mounted on an electric vehicle. The electrical equipment is, for example, an air conditioner. In such a configuration, when discharging from the battery pack 100 to the electrical equipment, the battery pack 100 is connected to the electrical equipment via a relay 1002 and a transformer by switching a switch 1001. In such a configuration, the battery pack 100 is, for example, a so-called 48V pack. The 48V pack corresponds to a power source for a mild hybrid.

[0022] The battery pack 100 may be configured as a power source for operating electrical equipment installed in, for example, commercial facilities, apartment buildings, detached houses, or factory facilities. In such a configuration, when discharging from the battery pack 100 to the electrical equipment, the battery pack 100 is connected to the electrical equipment via an inverter 1003 or a transformer. The electrical equipment may be, for example, lighting equipment, sound equipment, or air conditioners. In such a configuration, the battery pack 100 is, for example, a stationary battery.

[0023] (General circuit for controlling the secondary battery 101) Power supply from the secondary battery 101 to the CCIC 200, voltage control of the secondary battery 101, voltage balancing control of the secondary battery 101, and temperature measurement of the secondary battery 101 will be explained with reference to Figure 1.

[0024] (Power supply from secondary battery 101 to CCIC 200) In the battery pack 100, the positive terminal of the secondary battery 101 located on the highest voltage side is connected to Vin of CCIC 200 by the second wiring 211. Vin is a terminal related to the input voltage to CCIC 200. The secondary battery 101 located on the highest voltage side is the upper secondary battery 101 among the three secondary batteries 101 shown in Figure 1. The first resistor 221 is connected to the second wiring 211. In the battery pack 100, the negative terminal of the secondary battery 101 located on the lowest voltage side is connected to GND of CCIC 200 by the third wiring 212. GND is a terminal related to the ground potential of CCIC 200. The secondary battery 101 located on the lowest voltage side is the lower secondary battery 101 among the three secondary batteries 101 shown in Figure 1.

[0025] The second wiring 211 and the third wiring 212 are connected to the first filter capacitor 222 by the fourth wiring 213. Therefore, the secondary batteries 101 connected in series in the battery pack 100 are connected in parallel with the first filter capacitor 222. The first filter capacitor 222 functions as a filter to remove noise related to the voltage of the secondary batteries 101. The CCIC 200 is connected to the power supply control unit 311 of the MPU 300 via the first communication line 200L.

[0026] The power supply control unit 311 of the MPU 300 controls the power supply from the secondary battery 101 to the CCIC 200.

[0027] (Voltage control of secondary battery 101) In the battery pack 100, the positive terminal of each secondary battery 101 is connected to the first control unit 201 of the CCIC 200 by a fifth wiring 231. A second resistor 241 is connected to the fifth wiring 231. Here, each secondary battery 101 is connected in series. Therefore, the negative terminal of each secondary battery 101 is connected to the first control unit 201 of the CCIC 200 by the fifth wiring 231 to which the second resistor 241 is connected, similar to the positive terminal. The second resistor 241 may be provided only on the positive terminal side of each secondary battery 101, without being provided on the negative terminal side of each secondary battery 101.

[0028] A fifth wire 231 connected to the positive terminal of each secondary battery 101 and a fifth wire 231 connected to the negative terminal of each secondary battery 101 are connected to a second filter capacitor 242 by a sixth wire 232. Therefore, each secondary battery 101 is connected in parallel with the corresponding second filter capacitor 242. The second filter capacitor 242 functions as a filter to remove noise related to the voltage of the secondary battery 101 when the voltage of the secondary battery 101 is controlled.

[0029] The first control unit 201 of the CCIC 200 is connected to the voltage control unit 312 of the MPU 300 via the second communication line 201L. The storage unit 323 of the MPU 300 stores the voltage history of the secondary battery 101 in a way that allows for updating, storage, and input / output.

[0030] The voltage control unit 312 of the MPU 300 controls the operation of the first control unit 201 of the CCIC 200. The first control unit 201 controls the voltage of each secondary battery 101.

[0031] (Balancing control of secondary battery 101 voltage) In the battery pack 100, the positive terminal of each secondary battery 101 is connected to the second control unit 202 of the CCIC 200 by a seventh wiring 251. A third resistor 261 is connected to the seventh wiring 251. Here, each secondary battery 101 is connected in series. Therefore, the negative terminal of each secondary battery 101 is connected to the second control unit 202 of the CCIC 200 by the seventh wiring 251 to which the third resistor 261 is connected, similar to the positive terminal. The third resistor 261 may be provided only on the positive terminal side of each secondary battery 101, rather than on the negative terminal side of each secondary battery 101.

[0032] A third filter capacitor 262 is connected to the positive terminal of each secondary battery 101 by an eighth wire 252, and to the seventh wire 251 connected to the negative terminal of each secondary battery 101. Therefore, each secondary battery 101 is connected in parallel with the corresponding third filter capacitor 262. The third filter capacitor 262 functions as a filter to remove noise related to the voltage of the secondary battery 101 when the voltage of the secondary battery 101 is balanced.

[0033] The second control unit 202 of the CCIC 200 is connected to the voltage control unit 312 of the MPU 300 via the third communication line 202L. The storage unit 323 of the MPU 300 updates, stores, and allows input / output of the voltage balancing history of the secondary battery 101.

[0034] The voltage control unit 312 of the MPU 300 controls the operation of the second control unit 202 of the CCIC 200. The second control unit 202 obtains information about the secondary battery 101 with a relatively high voltage from the storage unit 323. The second control unit 202 balances the voltages of the secondary battery 101 with a relatively high voltage and the secondary battery 101 with a relatively low voltage by discharging the secondary battery 101 with a relatively high voltage. Balancing the voltages of different secondary batteries 101 means making the voltages of the different secondary batteries 101 relatively the same or making the difference in voltage between the different secondary batteries 101 relatively small.

[0035] By modifying the electrical circuit, a configuration may be adopted in which the secondary battery 101 with a relatively higher voltage discharges from the secondary battery 101 with a relatively lower voltage, thereby charging the secondary battery 101 with a relatively lower voltage. In this configuration as well, the voltages of the secondary battery 101 with a relatively higher voltage and the secondary battery 101 with a relatively lower voltage are balanced.

[0036] (Measurement of the temperature of the secondary battery 101) In the battery pack 100, each thermistor 102 is connected to the temperature measuring unit 313 of the MPU 300 via the first wiring 103. The storage unit 323 of the MPU 300 stores the temperature value of the secondary battery 101 in a way that allows it to be updated, accumulated, and input / output.

[0037] The battery pack 100 may be configured to measure the temperature of only some of the secondary batteries 101 among the multiple secondary batteries 101 included in the battery pack 100.

[0038] The temperature measuring unit 313 of the MPU 300 measures the temperature of the secondary battery 101 based on the resistance value of the thermistor 102 when a predetermined current is applied to the thermistor 102. The storage unit 323 of the MPU 300 stores the temperature of the secondary battery 101.

[0039] (General calculations regarding the control of the secondary battery 101) The calculation of the State of Cost (SOC) and State of Health (SOH) of the secondary battery 101 will be explained with reference to Figure 1.

[0040] (Calculation of SOC of secondary battery 101) The SOC calculation unit 321 of the MPU 300 calculates the State of Charge (SOC) of the secondary battery 101. For example, the SOC calculation unit 321 calculates the current SOC of the secondary battery 101 by dividing the current remaining capacity of the secondary battery 101 by the initial full charge capacity of the secondary battery 101 and multiplying the result by 100. The remaining capacity of the secondary battery 101 is calculated based on the cumulative value of the current discharged from the secondary battery 101, etc. Based on the calculated SOC value, etc., the MPU 300 calculates the maximum allowable voltage and maximum allowable current of the secondary battery 101. The storage unit 323 of the MPU 300 stores the SOC value of the secondary battery 101 so that it can be updated, stored, and input / output.

[0041] The SOC calculation unit 321 may calculate the current SOC of the secondary battery 101 based on an SOC-OCV curve indicating the relationship between SOC and open circuit voltage (OCV, Open Circuit Voltage). There is a correlation between the SOC and OCV of the secondary battery 101. OCV is estimated from the voltage, current, and temperature of the secondary battery 101.

[0042] (Calculation of SOH of Secondary Battery 101) The SOH calculation unit 322 of the MPU 300 calculates the capacity degradation rate (SOH, State of Health) of the secondary battery 101. The SOH calculation unit 322 calculates the current SOH of the secondary battery 101, for example, by multiplying by 100 the value obtained by dividing the current full charge capacity of the secondary battery 101 by the initial full charge capacity of the secondary battery 101. The storage unit 323 of the MPU 300 stores the SOH value of the secondary battery 101 in an updatable, accumulable, and input-output enable manner.

[0043] The SOH calculation unit 322 may calculate the current SOH of the secondary battery 101 by multiplying by 100 the value obtained by dividing the current internal resistance value of the secondary battery 101 by the initial internal resistance value of the secondary battery 101.

[0044] (Impedance Calculation Circuit 400 of Secondary Battery 101) The configuration of discharging related to the impedance calculation circuit 400 and the configuration of charging related to the impedance calculation circuit 400 will be described with reference to FIG. 1.

[0045] The impedance Z corresponds to electrochemical impedance.

[0046] (Discharging Configuration Related to Impedance Calculation Circuit 400) The discharging configuration including the first power storage capacitor 422 and the discharging configuration including the second power storage capacitor 425 will be described with reference to FIG. 1.

[0047] (Discharging Configuration Including First Power Storage Capacitor 422) The impedance calculation circuit 400 including the first power storage capacitor 422 for discharging includes an eleventh wiring 411, a first variable current circuit 421, the first power storage capacitor 422, and a current measurement circuit 423. The impedance calculation circuit 400 also includes a first current adjustment unit 440 connected to the first variable current circuit 421.

[0048] By means of the eleventh wiring 411, the first transistor 421A of the first variable current circuit 421, the first power storage capacitor 422, and the components of the current measurement circuit 423 are connected in series to the assembled battery 100 in that order.

[0049] The eleventh wiring 411 is indicated by an eleventh wiring 411a, an eleventh wiring 411b, an eleventh wiring 411c, an eleventh wiring 411d, an eleventh wiring 411e, and an eleventh wiring 411f from the high-voltage side to the low-voltage side of the assembled battery 100.

[0050] In the discharge configuration of the assembled battery 100, the constituent members are arranged in the order of the eleventh wiring 411a, the eleventh wiring 411b, the first transistor 421A of the first variable current circuit 421, the eleventh wiring 411c, the eleventh wiring 411d, the first power storage capacitor 422, the eleventh wiring 411e, the current measurement circuit 423, and the eleventh wiring 411f.

[0051] The first variable current circuit 421 defines the current value of the current discharged from the assembled battery 100. The first variable current circuit 421 corresponds to a current mirror circuit. The first variable current circuit 421 amplifies the mirrored current value.

[0052] The first variable current circuit 421 includes the first transistor 421A, the second transistor 421B, a first resistor 421C, and a second resistor 421D. The first transistor 421A and the second transistor 421B are PNP-type bipolar transistors. The collector side of the second transistor 421B is connected to the base side of the first transistor 421A and the base side of the second transistor 421B. The first resistor 421C is connected to the emitter side of the first transistor 421A. The second resistor 421D is connected to the emitter side of the second transistor 421B.

[0053] The potential of the first transistor 421A and the potential of the second transistor 421B are the same. Therefore, the ratio of the current flowing through the first transistor 421A to the current flowing through the second transistor 421B is the reciprocal of the ratio of the resistances of the first resistor 421C to the second resistor 421D. The resistance value of the first resistor 421C is, for example, 1Ω. The resistance value of the second resistor 421D is, for example, 100Ω. In this embodiment, the ratio of the current flowing through the first transistor 421A to the current flowing through the second transistor 421B is 100:1. When the current flowing through the second transistor 421B is 5mA, the current flowing through the first transistor 421A becomes 500mA. The first variable current circuit 421 can control a relatively large current with a relatively small current.

[0054] The first variable current circuit 421 is controlled by the first current adjustment unit 440, which varies the value of the current flowing through the first transistor 421A.

[0055] The first energy storage capacitor 422 is an energy storage element for storing the power discharged from the secondary battery 101. The charge stored in the first energy storage capacitor 422 is used to charge the secondary battery 101.

[0056] The current measurement circuit 423 is connected to the current measurement unit 332 of the MPU 300 via the fourth communication line 423L. The current measurement circuit 423 amplifies the potential difference generated by the shunt resistor with an amplifier and outputs it. The current measurement circuit 423 measures the amplified potential difference with an A / D converter and converts it into a current value.

[0057] The first current adjustment unit 440 adjusts the current value when discharging from the secondary battery 101, thereby setting a current value that matches the type of secondary battery 101, or setting a battery value that matches the response characteristics of the secondary battery 101.

[0058] The first current adjustment unit 440 adjusts the current flowing through the first transistor 421A of the first variable current circuit 421 by adjusting the current flowing through the second transistor 421B of the first variable current circuit 421. The first current adjustment unit 440 is located between the second transistor 421B of the first variable current circuit 421 and the measurement timing control unit 331 of the MPU 300. The first current adjustment unit 440 includes a resistor 441, a transistor 442, a first operational amplifier 443, and a first converter 444, moving from the side of the second transistor 421B toward the measurement timing control unit 331. The first current adjustment unit 440 also includes a resistor 445. In the first current adjustment unit 440, the emitter side of transistor 442 and the 11th wiring 411 are connected via the resistor 445.

[0059] The first operational amplifier 443 varies the current flowing through the second transistor 421B of the first variable current circuit 421 based on a predetermined voltage value. That is, the current flowing through the second transistor 421B is varied by the voltage output from the first operational amplifier 443. For example, when the current flowing through the second transistor 421B is set to 5 mA, the voltage output from the first operational amplifier 443 is set to 2 V. Also, for example, when the current flowing through the second transistor 421B is set to 2.5 mA, the voltage output from the first operational amplifier 443 is set to 1 V.

[0060] The first converter 444 controls the first operational amplifier 443 based on a predetermined gradation of voltage values. The predetermined gradation is, for example, 256 gradations. The first converter 444 is a digital-to-analog converter. The measurement timing control unit 331 uses the first converter 444 to control the voltage output from the first operational amplifier 443 to the second transistor 421B.

[0061] (Discharge configuration including second energy storage capacitor 425) The impedance calculation circuit 400, which includes the second energy storage capacitor 425 for discharge, includes a first rectifier element 424, a second energy storage capacitor 425, and a first MOS-FET 431.

[0062] The first rectifier element 424, the second energy storage capacitor 425, and the first MOS-FET 431 are connected in parallel to the first energy storage capacitor 422 by the 12th wiring 412.

[0063] The twelfth wiring 412 is connected in parallel to the portions of the eleventh wiring 411d and 11th wiring 411e. The twelfth wiring 412 is indicated by the twelfth wiring 412a, twelfth wiring 412b, twelfth wiring 412c, and twelfth wiring 412d, from the high-voltage side to the low-voltage side of the battery pack 100. The twelfth wiring 412a is connected to the eleventh wiring 411d. The twelfth wiring 412d is connected to the eleventh wiring 411e.

[0064] In the discharge configuration of the battery pack 100, the components are arranged in the following order: 11th wiring 411d, 12th wiring 412a, 1st rectifier element 424, 12th wiring 412b, 2nd energy storage capacitor 425, 12th wiring 412c, 1st MOS-FET 431, 12th wiring 412d, and 11th wiring 411e.

[0065] The first rectifier element 424 prevents the current related to charging the battery pack 100 from flowing from the second energy storage capacitor 425 side to the first energy storage capacitor 422 side.

[0066] The second storage capacitor 425 is a storage element for storing the power discharged from the secondary battery 101. The charge stored in the second storage capacitor 425 is used to charge the secondary battery 101. The second storage capacitor 425 and the first storage capacitor 422 are installed in parallel between the first constant current circuit 521 and the current measurement circuit 423. In the discharge related to the calculation of the impedance Z of the secondary battery 101, the first storage capacitor 422 and the second storage capacitor 425 are connected in parallel.

[0067] The first MOS-FET 431 is used as a switching circuit. The first MOS-FET 431 is connected to the measurement timing control unit 331 of the MPU 300 via the fifth communication line 431L.

[0068] (Charging configuration related to impedance calculation circuit 400) The impedance calculation circuit 400 related to charging includes a current measurement circuit 423, a first energy storage capacitor 422, a second MOS-FET 471, a second energy storage capacitor 425, a second variable current circuit 461, and a second rectifier element 462. The impedance calculation circuit 400 also includes a second current adjustment unit 480 connected to the second variable current circuit 461.

[0069] The 13th wiring 413 connects the current measurement circuit 423, the first energy storage capacitor 422, the second MOS-FET 471, the second energy storage capacitor 425, the first transistor 461A of the second variable current circuit 461, and the second rectifier element 462 in that order to the battery pack 100.

[0070] The 13th wiring 413 is indicated by the 11th wiring 411f, 11th wiring 411e, 11th wiring 411d, 13th wiring 413a, 13th wiring 413b, 13th wiring 413c, 13th wiring 413d, 13th wiring 413e, and 11th wiring 411a, from the low-voltage side to the high-voltage side of the battery pack 100.

[0071] In the charging configuration of the battery pack 100, the components are arranged in the following order: 11th wiring 411f, current measurement circuit 423, 11th wiring 411e, first energy storage capacitor 422, 11th wiring 411d, 13th wiring 413a, second MOS-FET 471, 13th wiring 413b, second energy storage capacitor 425, 13th wiring 413c, first transistor 461A of the second variable current circuit 461, 13th wiring 413d, second rectifier element 462, 13th wiring 413e, and 11th wiring 411a.

[0072] The first energy storage capacitor 422 is used as a discharge element for charging the secondary battery 101.

[0073] The second MOS-FET 471 is used as a switching circuit. The second MOS-FET 471 is connected to the measurement timing control unit 331 of the MPU 300 via the sixth communication line 471L.

[0074] The second energy storage capacitor 425 is used as a discharge element for charging the secondary battery 101. In the charging process related to the calculation of the impedance Z of the secondary battery 101, the first energy storage capacitor 422 and the second energy storage capacitor 425 are connected in series.

[0075] The second variable current circuit 461 defines the current value of the current discharged from the battery pack 100. The second variable current circuit 461 corresponds to a current mirror circuit. The second variable current circuit 461 amplifies the mirrored current value.

[0076] The second variable current circuit 461 includes a first transistor 461A, a second transistor 461B, a first resistor 461C, and a second resistor 461D. The first transistor 461A and the second transistor 461B are PNP bipolar transistors. The collector side of the second transistor 461B is connected to the base side of the first transistor 461A and the base side of the second transistor 461B. The first resistor 461C is connected to the emitter side of the first transistor 461A. The second resistor 461D is connected to the emitter side of the second transistor 461B.

[0077] The potential of the first transistor 461A and the potential of the second transistor 461B are the same. Therefore, the ratio of the current flowing through the first transistor 461A to the current flowing through the second transistor 461B is the reciprocal of the ratio of the resistances of the first resistor 461C to the second resistor 461D. The resistance value of the first resistor 461C is, for example, 1Ω. The resistance value of the second resistor 461D is, for example, 100Ω. In this embodiment, the ratio of the current flowing through the first transistor 461A to the current flowing through the second transistor 461B is 100:1. When the current flowing through the second transistor 461B is 5mA, the current flowing through the first transistor 461A becomes 500mA. The second variable current circuit 461 can control a relatively large current with a relatively small current.

[0078] The second variable current circuit 461 is controlled by the second current adjustment unit 480, which varies the value of the current flowing through the first transistor 461A.

[0079] The second rectifier element 462 prevents the current discharged from the battery pack 100 from flowing through the second variable current circuit 461.

[0080] The second current adjustment unit 480 adjusts the current value when charging the secondary battery 101, thereby setting a current value that matches the type of secondary battery 101, or setting a battery value that matches the response characteristics of the secondary battery 101.

[0081] The second current adjustment unit 480 adjusts the current flowing through the first transistor 461A of the second variable current circuit 461 by adjusting the current flowing through the second transistor 461B of the second variable current circuit 461. The second current adjustment unit 480 is located between the second transistor 461B of the second variable current circuit 461 and the measurement timing control unit 331 of the MPU 300. The second current adjustment unit 480 includes a resistor 441, a transistor 442, a second operational amplifier 483, and a second converter 484, moving from the side of the second transistor 461B toward the measurement timing control unit 331. The second current adjustment unit 480 also includes a resistor 445. In the second current adjustment unit 480, the emitter side of transistor 442 and the 11th wiring 411 are connected via the resistor 445.

[0082] The second operational amplifier 483 varies the current flowing through the second transistor 461B of the second variable current circuit 461 based on a predetermined voltage value. That is, the current flowing through the second transistor 461B is varied by the voltage output from the second operational amplifier 483. For example, when the current flowing through the second transistor 461B is set to 5 mA, the voltage output from the second operational amplifier 483 is set to 2 V. Also, for example, when the current flowing through the second transistor 461B is set to 2.5 mA, the voltage output from the second operational amplifier 483 is set to 1 V.

[0083] The second converter 484 controls the second operational amplifier 483 based on a predetermined gradation voltage value. The predetermined gradation is, for example, 256 gradations. The second converter 484 is a digital-to-analog converter. The measurement timing control unit 331 uses the second converter 484 to control the voltage output from the second operational amplifier 483 to the second transistor 461B.

[0084] (Charge and Discharge Control for Impedance Calculation Circuit 400) Regarding the charge and discharge control for the impedance calculation circuit 400, the control of the discharge frequency, the control of the discharge current value, the control of the charge frequency, and the control of the charge current value will be explained with reference to Figures 1 and 2.

[0085] Figure 2 is a time chart relating to the calculation of the impedance Z of the battery pack 100 in the embodiment.

[0086] (Frequency control related to discharge) The measurement timing control unit 331 of the MPU 300 controls the operation of the first MOS-FET 431 and the first operational amplifier 443.

[0087] While the first operational amplifier 443 is ON, the battery pack 100 charges the first energy storage capacitor 422 while simultaneously discharging. That is, when the first operational amplifier 443 is turned ON, current is discharged from the high-voltage positive terminal of the battery pack 100 towards the low-voltage negative terminal of the battery pack 100, via the first constant current circuit 521, the first energy storage capacitor 422, and the current measurement circuit 423.

[0088] While the first MOS-FET 431 and the first operational amplifier 443 are ON, the battery pack 100 charges the second energy storage capacitor 425 while simultaneously discharging. That is, while the first MOS-FET 431 and the first operational amplifier 443 are ON, the battery pack 100 discharges from the high-voltage positive terminal to the low-voltage negative terminal via the first constant current circuit 521, the second energy storage capacitor 425, and the current measurement circuit 423. The timing of the ON and OFF states of the first operational amplifier 443 and the first MOS-FET 431 is set to be the same.

[0089] The current measuring unit 332 of the MPU 300 controls the operation of the current measuring circuit 423. The current measuring circuit 423 measures the current value during discharge from the battery pack 100.

[0090] Here, the measurement timing control unit 331 of the MPU 300 controls the timing of operation of the first MOS-FET 431 and the first operational amplifier 443, as shown in Figure 2, thereby varying the measurement frequencies of voltage and current in the calculation of the impedance Z of the secondary battery 101.

[0091] The discharge period of the secondary battery 101 is fixed at a constant value. For example, the discharge period is 10 Hz (100 ms).

[0092] On the other hand, the discharge time in each cycle of the discharge of the secondary battery 101 is varied, for example, from a minimum of 400 Hz (1 ms) to a maximum of 10 Hz (50 ms). Specifically, the discharge frequency of the secondary battery 101 is varied by making the duty cycle of the discharge different in each cycle of the discharge, as follows: In each cycle of the discharge, the timing for ending the discharge (turning off the first MOS-FET 431 and the first operational amplifier 443) is set to the same value. On the other hand, in each cycle of the discharge, the timing for starting the discharge (turning on the first MOS-FET 431 and the first operational amplifier 443) is set to a different value. That is, the discharge frequency (the interval between pulses) of the secondary battery 101 is varied by the timing of turning on the first MOS-FET 431 and the first operational amplifier 443.

[0093] (Control of current value related to discharge) The measurement timing control unit 331 of the MPU 300 uses the first converter 444 to convert a predetermined digital signal into an analog signal with a gradation of 256 or the like, and controls the first operational amplifier 443. The first operational amplifier 443 varies the current value flowing through the second transistor 421B of the first variable current circuit 421 based on a predetermined voltage value. Depending on the current flowing through the second transistor 421B of the first variable current circuit 421, the current flowing through the first transistor 421A of the first variable current circuit 421 is varied. The current flowing through the first transistor 421A of the first variable current circuit 421 corresponds to the current value related to the discharge of the secondary battery 101. The measurement timing control unit 331 controls the current value flowing through the second transistor 421B of the first variable current circuit 421 via the first converter 444 and the first operational amplifier 443 to vary the current value related to the charging of the secondary battery 101.

[0094] (Frequency control related to charging) The measurement timing control unit 331 of the MPU 300 controls the operation of the second MOS-FET 471 and the second operational amplifier 483.

[0095] While the second MOS-FET 471 and the second operational amplifier 483 are ON, the first energy storage capacitor 422 and the second energy storage capacitor 425 charge the battery pack 100. That is, when the second MOS-FET 471 and the second operational amplifier 483 are turned ON, the first energy storage capacitor 422 and the second energy storage capacitor 425 charge the positive terminal on the high-voltage side of the battery pack 100 via the second constant current circuit 541.

[0096] The current measuring unit 332 of the MPU 300 controls the operation of the current measuring circuit 423. The current measuring circuit 423 measures the current value while the battery pack 100 is being charged.

[0097] Here, the measurement timing control unit 331 of the MPU 300 controls the timing of operation of the second MOS-FET 471 and the second operational amplifier 483, as shown in Figure 2, thereby varying the measurement frequencies of voltage and current in the calculation of the impedance Z of the secondary battery 101.

[0098] The charging cycle of the secondary battery 101 is fixed to a constant value, for example, a constant value, similar to the discharging cycle. The charging cycle is, for example, 10 Hz (100 ms), similar to the discharging cycle.

[0099] On the other hand, the charging time in each charging cycle of the secondary battery 101 is varied, similar to the discharge time, from a minimum of 400 Hz (1 ms) to a maximum of 10 Hz (50 ms). Specifically, the discharge frequency of the secondary battery 101 is varied by changing the duty cycle of charging in each charging cycle, as follows: In each charging cycle, the timing for ending charging (turning off the second MOS-FET 471 and the second operational amplifier 483) is set to the same value. On the other hand, in each charging cycle, the timing for starting charging (turning on the second MOS-FET 471 and the second operational amplifier 483) is set to a different value. That is, the charging frequency (the interval between pulses) of the secondary battery 101 is varied by the timing of turning on the second MOS-FET 471 and the second operational amplifier 483.

[0100] (Control of current value related to charging) The measurement timing control unit 331 of the MPU 300 uses the second converter 484 to convert a predetermined digital signal into a grayscale analog signal such as 256 and controls the second operational amplifier 483. The second operational amplifier 483 varies the current value flowing through the second transistor 461B of the second variable current circuit 461 based on a predetermined voltage value. Depending on the current flowing through the second transistor 461B of the second variable current circuit 461, the current flowing through the first transistor 461A of the second variable current circuit 461 is varied. The current flowing through the first transistor 461A of the second variable current circuit 461 corresponds to the current value related to charging the secondary battery 101. The measurement timing control unit 331 controls the current value flowing through the second transistor 461B of the second variable current circuit 461 via the second converter 484 and the second operational amplifier 483 to vary the current value related to charging the secondary battery 101.

[0101] (Impedance calculation circuit 500 for secondary battery 101 according to a modified embodiment) Unlike the impedance calculation circuit 400, the impedance calculation circuit 500 according to a modified embodiment fixes the value of the current used to charge and discharge the secondary battery 101 to a constant value. That is, unlike the impedance calculation circuit 400, the impedance calculation circuit 500 does not vary the value of the current used to charge and discharge the secondary battery 101.

[0102] With regard to the impedance calculation circuit 500 of the secondary battery 101 according to the modified example, the discharge configuration related to the calculation of impedance Z and the charging configuration related to the calculation of impedance Z will be explained with reference to Figures 3 and 4.

[0103] Figure 3 shows an electrical circuit for controlling the battery pack 100 and calculating its impedance Z in a modified example of the embodiment. Figure 4 shows a time chart for calculating the impedance Z of the battery pack 100 in a modified example of the embodiment.

[0104] (Discharge configuration related to impedance calculation circuit 500) The discharge configuration including the first energy storage capacitor 422 and the discharge configuration including the second energy storage capacitor 425 will be described with reference to Figure 3.

[0105] (Discharge configuration including the first energy storage capacitor 422) The configuration of the impedance calculation circuit 500 including the first energy storage capacitor 422 for discharge is partially different from the configuration of the impedance calculation circuit 400 including the first energy storage capacitor 422 for discharge.

[0106] The impedance calculation circuit 500 replaces the first variable current circuit 421 of the impedance calculation circuit 400 with a first constant current circuit 521. The impedance calculation circuit 500 replaces the first current adjustment unit 440 of the impedance calculation circuit 400 with a third MOS-FET 531. In the impedance calculation circuit 500, the third MOS-FET 531 is provided between the first constant current circuit 521 and the first energy storage capacitor 422.

[0107] In the impedance calculation circuit 500, which includes a first energy storage capacitor 422 related to discharge, the components of the first constant current circuit 521, the third MOS-FET 531, the first energy storage capacitor 422, and the current measurement circuit 423 are connected in series with respect to the battery pack 100 in that order.

[0108] In the impedance calculation circuit 500, which includes the first energy storage capacitor 422 related to discharge, the components are arranged in the following order: 11th wiring 411a, 11th wiring 411b, first constant current circuit 521, 11th wiring 411c, third MOS-FET 531, 11th wiring 411d, first energy storage capacitor 422, 11th wiring 411e, current measurement circuit 423, and 11th wiring 411f.

[0109] The first constant current circuit 521 and the third MOS-FET 531, which are specific to the impedance calculation circuit 500 related to discharge, will now be explained.

[0110] The first constant current circuit 521 defines the current value of the current discharged from the battery pack 100. The first constant current circuit 521 includes a first transistor 521A, a second transistor 521B, a first resistor 521C, and a second resistor 521D. The first transistor 521A and the second transistor 521B are NPN bipolar transistors. The first transistor 521A and the second transistor 521B are connected in a Dartlin configuration. The emitter side of the first transistor 521A is connected to the base side of the second transistor 521B. The first transistor 521A and the first resistor 521C are connected in parallel. The second transistor 521B and the second resistor 521D are connected in parallel.

[0111] The third MOS-FET 531 is used as a switching circuit. The third MOS-FET 531 is connected to the measurement timing control unit 331 of the MPU 300 via the third communication line 531L.

[0112] (Discharge configuration including the second energy storage capacitor 425) The configuration of the impedance calculation circuit 500 including the second energy storage capacitor 425 for discharge is the same as the configuration of the impedance calculation circuit 400 including the second energy storage capacitor 425 for discharge.

[0113] In the impedance calculation circuit 500, which includes a second energy storage capacitor 425 related to discharge, the components of the first rectifier element 424, the second energy storage capacitor 425, and the first MOS-FET 431 are connected in parallel to the first energy storage capacitor 422 in that order.

[0114] (Charging configuration related to impedance calculation circuit 500) The configuration of the impedance calculation circuit 500 related to charging is partially different from the configuration of the impedance calculation circuit 400 related to charging.

[0115] The impedance calculation circuit 500 replaces the second variable current circuit 461 of the impedance calculation circuit 400 with a second constant current circuit 541. The impedance calculation circuit 500 does not have the first current adjustment unit 440 of the impedance calculation circuit 400.

[0116] In the impedance calculation circuit 500 for charging, the components of the current measurement circuit 423, the first energy storage capacitor 422, the second MOS-FET 471, the second energy storage capacitor 425, the second constant current circuit 541, and the second rectifier element 462 are connected in series with the battery pack 100 in that order.

[0117] Next, we will explain the second constant current circuit 541, which is specific to the impedance calculation circuit 500 related to charging.

[0118] The second constant current circuit 541 defines the current value of the current that charges the battery pack 100. The second constant current circuit 541 includes a first transistor 541A, a second transistor 541B, a first resistor 541C, and a second resistor 541D. The first transistor 541A and the second transistor 541B are NPN bipolar transistors. The first transistor 541A and the second transistor 541B are connected in a Dartlin configuration. The emitter side of the first transistor 541A is connected to the base side of the second transistor 541B. The first transistor 541A and the first resistor 541C are connected in parallel. The second transistor 541B and the second resistor 541D are connected in parallel.

[0119] (Charge and Discharge Control for Impedance Calculation Circuit 500) Regarding the charge and discharge control for the impedance calculation circuit 500, the control of the discharge frequency and the control of the charge frequency will be explained with reference to Figures 3 and 4.

[0120] (Control of discharge frequency) The control of discharge frequency will be explained with reference to Figure 4.

[0121] The control of the discharge impedance calculation circuit 500 differs in part from the control of the discharge impedance calculation circuit 400.

[0122] In controlling the impedance calculation circuit 500, the measurement timing control unit 331 of the MPU 300 controls the operation of the third MOS-FET 531 instead of the first operational amplifier 443. That is, in controlling the impedance calculation circuit 500, the measurement timing control unit 331 controls the operation of the first MOS-FET 431 and the third MOS-FET 531. In the aforementioned control of the impedance calculation circuit 400, the measurement timing control unit 331 controlled the operation of the first MOS-FET 431 and the first operational amplifier 443.

[0123] The measurement timing control unit 331 of the MPU 300 controls the operation of the first MOS-FET 431 and the third MOS-FET 531.

[0124] While the third MOS-FET 531 is ON, the battery pack 100 charges the first energy storage capacitor 422 while simultaneously discharging. That is, when the third MOS-FET 531 is ON, current is discharged from the high-voltage positive terminal of the battery pack 100 towards the low-voltage negative terminal of the battery pack 100, via the first constant current circuit 521, the first energy storage capacitor 422, and the current measurement circuit 423.

[0125] While the first MOS-FET 431 and the third MOS-FET 531 are ON, the battery pack 100 charges the second energy storage capacitor 425 while simultaneously discharging. That is, while the first MOS-FET 431 and the third MOS-FET 531 are ON, current is discharged from the high-voltage positive terminal of the battery pack 100 towards the low-voltage negative terminal of the battery pack 100, via the first constant current circuit 521, the second energy storage capacitor 425, and the current measurement circuit 423. The timing of the ON and OFF of the third MOS-FET 531 and the first MOS-FET 431 is set to be the same.

[0126] The current measuring unit 332 of the MPU 300 controls the operation of the current measuring circuit 423. The current measuring circuit 423 measures the current value during discharge from the battery pack 100.

[0127] The measurement timing control unit 331 of the MPU 300 controls the timing of operation of the first MOS-FET 431 and the third MOS-FET 531. That is, the measurement timing control unit 331 varies the measurement frequency related to the calculation of the impedance Z of the secondary battery 101 during discharge, similar to the control of the impedance calculation circuit 400 described above.

[0128] (Frequency control related to charging) The frequency control related to charging will be explained with reference to Figure 4.

[0129] The control of the impedance calculation circuit 500 related to charging differs in part from the control of the impedance calculation circuit 400 related to charging.

[0130] In controlling the impedance calculation circuit 500, the measurement timing control unit 331 controls only the operation of the second MOS-FET 471. In controlling the impedance calculation circuit 400 described above, the measurement timing control unit 331 controlled the operation of both the second MOS-FET 471 and the second operational amplifier 483.

[0131] The measurement timing control unit 331 of the MPU 300 controls the operation of the second MOS-FET 471.

[0132] While the second MOS-FET 471 is ON, the first and second energy storage capacitors 422 and 425 charge the battery pack 100. That is, when the second MOS-FET 471 is turned ON, the first and second energy storage capacitors 422 and 425 charge the positive electrode on the high-voltage side of the battery pack 100 via the second constant current circuit 541.

[0133] The current measuring unit 332 of the MPU 300 controls the operation of the current measuring circuit 423. The current measuring circuit 423 measures the current value while the battery pack 100 is being charged.

[0134] The measurement timing control unit 331 of the MPU 300 controls the timing of the operation of the second MOS-FET 471. That is, the measurement timing control unit 331 varies the measurement frequency related to the calculation of the impedance Z of the secondary battery 101 during charging, similar to the control of the impedance calculation circuit 400 described above.

[0135] (Nyquist diagram for the impedance of secondary battery 101) The Nyquist diagram for the impedance of secondary battery 101 will be explained with reference to Figures 5 and 6. Hereinafter, the impedance of secondary battery 101 will be referred to as the impedance Z of secondary battery 101.

[0136] Figure 5 is a simplified equivalent circuit of the secondary battery 101 of the embodiment. Figure 6 is a schematic diagram showing the Nyquist plot relating to the impedance of the secondary battery 101 of the embodiment.

[0137] As shown in Figure 5, the secondary battery 101 of the embodiment is simulated by an electrolyte resistance and an equivalent circuit in which a capacitor component connected in parallel and a charge transfer resistance connected in series.

[0138] The impedance Z of the secondary battery 101 is expressed by equation 1. In equation 1, Rs is the electrolyte resistance value (a predetermined resistance value) of the secondary battery 101. In equation 1, Rct is the charge transfer resistance value (a predetermined resistance value) of the secondary battery 101. In equation 1, j is an imaginary number. In equation 1, ω is the angular frequency. The angular frequency is expressed as 2πf, where f is the frequency. In equation 1, Cdl is the capacitor component of the secondary battery 101.

[0139]

[0140] Furthermore, the impedance Z of the secondary battery 101 is expressed by equation 2. Z' in equation 2 is the real part of the impedance Z of the secondary battery 101. The real part of the impedance Z of the secondary battery 101 corresponds to the value of the real component of the impedance Z of the secondary battery 101. Z'' in equation 2 is the imaginary part of the impedance Z of the secondary battery 101. The imaginary part of the impedance Z of the secondary battery 101 corresponds to the value of the imaginary component of the impedance Z of the secondary battery 101.

[0141]

[0142] The real part Z' of the impedance Z of the secondary battery 101 is expressed by equation 3.

[0143]

[0144] The imaginary part Z'' of the impedance Z of the secondary battery 101 is expressed by equation 4.

[0145]

[0146] Number 5 is derived from numbers 3 and 4. Number 5 is obtained by eliminating ω from numbers 3 and 4.

[0147]

[0148] Using equation 5, the electrolyte resistance Rs and charge transfer resistance Rct of the secondary battery 101 are derived from the intersection of the graph representing the Nyquist plot of the impedance Z of the secondary battery 101 and the real part Z' of the impedance Z. The graph is represented in a semicircular shape.

[0149] The Nyquist plot for the impedance Z of the secondary battery 101 is fitted with the calculation result of the impedance Z of the secondary battery 101 to estimate the electrolyte resistance Rs and charge transfer resistance Rct of the secondary battery 101. A portion of the waveform of the impedance Z of the secondary battery 101 is simulated using a polynomial. That is, the waveform of the impedance of the secondary battery 101, excluding the diffusion resistance region, is simulated using a polynomial.

[0150] The polynomial is set up as, for example, a quadratic function. The polynomial is represented by the first and second axes. The first axis is the horizontal axis in Figure 6 and shows the real part Z' of the impedance Z of the secondary battery 101. The real part Z' of the impedance Z of the secondary battery 101 corresponds to the resistance component of the secondary battery 101 when the secondary battery 101 is simulated using an equivalent circuit. The second axis is the vertical axis in Figure 6 and shows the imaginary part Z'' of the impedance Z of the secondary battery 101. The second axis intersects the first axis. The real part Z' of the impedance Z of the secondary battery 101 corresponds to the capacitor and inductive components of the secondary battery 101 when the secondary battery 101 is simulated using an equivalent circuit.

[0151] In a quadratic polynomial, the coefficients of the quadratic function are set to be relatively larger than the coefficients of the linear function.

[0152] The polynomial may be defined as a function of degree 3 or higher. When the polynomial is defined as a function of degree 3 or higher, the coefficients of the quadratic function should be set relatively larger than the coefficients of degree 3 or higher.

[0153] (Plot of the impedance Z of the secondary battery 101 against the Nyquist plot) The plot of the impedance Z of the secondary battery 101 against the Nyquist plot will be explained.

[0154] To calculate the impedance Z of the secondary battery 101, the charging and discharging frequency H of the secondary battery 101 is set.

[0155] The impedance Z of the secondary battery 101 corresponds to the value obtained by dividing the voltage V of the secondary battery 101 by the current I of the secondary battery 101. The voltage V and current I when the secondary battery 101 is charged and discharged are determined by the charging and discharging frequency H. The formulas that express the charging and discharging voltage V and current I of the secondary battery 101 include the parameter of the charging and discharging frequency H. In other words, the voltage V and current I when the secondary battery 101 is charged and discharged change as the charging and discharging frequency H changes.

[0156] For a given value of impedance Z, the real part Z' (first axis) and the imaginary part Z'' (second axis) of impedance Z, as shown in Figure 6, are predetermined. That is, since the real part Z' and imaginary part Z'' of impedance Z are known for a given value of impedance Z, if the value of impedance Z is known, the real part Z' and imaginary part Z'' of impedance Z can be determined. The value of impedance Z for which the real part Z' and imaginary part Z'' of impedance Z are predetermined is plotted to correspond to the Nyquist diagram of secondary battery 101 represented by the real part Z' and imaginary part Z'' of impedance Z.

[0157] The calculation result of the impedance Z of the secondary battery 101 is fitted based on a polynomial by plotting multiple impedance Z values ​​of the secondary battery 101 to correspond to the Nyquist plot of the secondary battery 101. For example, a quadratic function is selected as the polynomial. Based on the least squares method, the waveform of the quadratic function relating to the impedance Z of the secondary battery 101 intersects the first axis at two points is simulated. The least squares method is a method for deriving the most likely relationship such that the sum of the squares of the errors between the measured value and the simulated value is minimized.

[0158] (Calculation of the impedance Z of the secondary battery 101) The calculation of the impedance Z of the secondary battery 101 will be explained with reference to Figure 7.

[0159] Figure 7 is a schematic diagram showing the state in which the calculated impedance Z of the secondary battery 101 of the embodiment has been fitted to the Nyquist diagram relating to the impedance of the secondary battery 101.

[0160] The waveform of the Nyquist plot of the impedance Z of the secondary battery 101 assumes that the frequency of the impedance Z decreases continuously as the imaginary part Z'' of the impedance Z moves from the positive region to the negative region. That is, the waveform of the Nyquist plot of the impedance Z of the secondary battery 101 assumes that the imaginary part Z'' of the impedance Z rises continuously to the upper right as it moves from the positive region to the negative region, as shown in Figure 7.

[0161] The calculation unit 341 calculates the impedance Z of the secondary battery 101 based on a predetermined frequency. The calculation unit 341 corresponds to a configuration that embodies the calculation step. For example, the calculation unit 341 discharges and charges the secondary battery 101 at five different frequencies. For example, the number of frequencies used to calculate the impedance Z is five.

[0162] The number of frequencies used to calculate the impedance Z is determined considering the accuracy of the calculation of the impedance Z of the secondary battery 101 and the time required for the calculation. Increasing the number of frequencies used to calculate the impedance Z improves the accuracy of the calculation of the impedance Z of the secondary battery 101. Decreasing the number of frequencies used to calculate the impedance Z shortens the time required for the calculation of the impedance Z of the secondary battery 101. When the battery pack 100 is installed in an electric vehicle, the time required for the calculation of the impedance Z of the secondary battery 101 must be within a time that can keep up with the control related to the operation of the electric vehicle. When the battery pack 100 removed from an electric vehicle is inspected for recycling, the time required for the calculation of the impedance Z of the secondary battery 101 must be within a predetermined inspection time.

[0163] The five distinct frequencies, as shown in Figure 7, are referred to as the first frequency H1, the third frequency H3, the fourth frequency H4, the fifth frequency H5, and the second frequency H2, respectively, from the side with the relatively higher frequency to the side with the relatively lower frequency. The side with the relatively higher frequency to the side with the relatively lower frequency corresponds to the left to the right side of the first axis shown in Figure 7.

[0164] The first frequency H1, the third frequency H3, the fourth frequency H4, the fifth frequency H5, and the second frequency H2 are set based on the battery type of the secondary battery 101. Specifically, the first frequency H1, the third frequency H3, the fourth frequency H4, the fifth frequency H5, and the second frequency H2 are set based on the type of positive electrode active material and the type of negative electrode active material of the secondary battery 101. Furthermore, the first frequency H1, the third frequency H3, the fourth frequency H4, the fifth frequency H5, and the second frequency H2 are set based on the degree of degradation of the secondary battery 101. The degree of degradation of the secondary battery 101 is determined based on the State of Health (SOH) of the secondary battery 101 and the cumulative operating time of the battery pack 100.

[0165] The calculation unit 341 calculates the first impedance Z1 at the first frequency H1 in the region where the imaginary part Z'' of the impedance Z is positive. The first frequency H1 is set to be relatively higher than the frequencies in the region where the imaginary part Z'' of the impedance Z is negative. For example, the calculation unit 341 sets the first frequency H1 such that the value of the real part Z' of the first impedance Z1 is relatively smaller than the value of the real part Z' of the second impedance Z2. Alternatively, the calculation unit 341 sets the first frequency H1 such that the value of the real part Z' of the first impedance Z1 is less than or equal to 1 / 10 of the value of the real part Z' at the inflection point T of the quadratic function waveform, and greater than 0.

[0166] The calculation unit 341 calculates a third impedance Z3 based on a third frequency H3 in the region where the imaginary part Z'' of impedance Z is negative. The third impedance Z3 is set to have a frequency that is relatively lower than the first impedance Z1 and relatively higher than the second impedance Z2. The third impedance Z3 is set to a relatively high frequency region along the first axis, with the inflection point T of the quadratic function waveform simulated by the estimation step as the boundary.

[0167] The calculation unit 341 calculates a fourth impedance Z4 based on a fourth frequency H4 in the region where the imaginary part Z'' of impedance Z is negative. The fourth impedance Z4 is set to have a frequency that is relatively lower than the third impedance Z3 and a frequency that is relatively higher than the inflection point T of the quadratic function.

[0168] The calculation unit 341 calculates a fifth impedance Z5 based on a fifth frequency H5 in the region where the imaginary part Z'' of the impedance is negative. The fifth impedance Z5 is set to have a frequency lower than the inflection point T of the quadratic function and a relatively higher frequency than the second impedance Z2.

[0169] The calculation unit 341 calculates the second impedance Z2 at the second frequency H2 in the region where the imaginary part Z'' of the impedance Z is negative. The second impedance Z2 is set to have a frequency that is relatively lower than the fifth impedance Z5. The second frequency H2 is set to have a frequency that is relatively lower than the first frequency H1. The second impedance Z2 is set to be in a relatively low-frequency region along the first axis, with the inflection point T of the quadratic function waveform simulated by the estimation step as the boundary.

[0170] The calculation unit 341 sets a first frequency H1, a third frequency H3, a fourth frequency H4, a fifth frequency H5, and a second frequency H2 based on the type of positive electrode active material and the type of negative electrode active material of the secondary battery 101. The frequencies based on the type of positive electrode active material and the type of negative electrode active material of the secondary battery 101 are stored in the storage unit 323 of the MPU 300.

[0171] The calculation unit 341 sets the first frequency H1, third frequency H3, fourth frequency H4, fifth frequency H5, and second frequency H2 to be relatively low, based on the usage history and degradation information of the secondary battery 101. The usage history and degradation information of the secondary battery 101 includes the state of overheardness (SOH) of the secondary battery 101 and the cumulative number of charge cycles of the secondary battery 101. The usage history and degradation information of the secondary battery 101 may also include the cumulative mileage of the electric vehicle.

[0172] The calculation unit 341 sets the interval between the first frequency H1 and the second frequency H2 to be relatively wide. Information on the usage history and degradation of the secondary battery 101 is stored in the storage unit 323 of the MPU 300.

[0173] In calculating the impedance Z of the secondary battery 101, the calculation unit 341 corrects the set frequency based on a table relating to the SOC, SOH, temperature, etc., of the secondary battery 101. The set frequency is shifted to a relatively lower side by a predetermined value, depending on the SOC, SOH, temperature, etc., of the secondary battery 101. The calculation unit 341 obtains information such as the SOH, SOH, temperature, etc., of the secondary battery 101 from the storage unit 323 of the MPU 300. The calculation unit 341 multiplies the set frequency by a correction coefficient relating to the SOC, SOH, temperature, etc., of the secondary battery 101. As a result, the set frequency is corrected from 100 Hz to 105 Hz, or from 100 Hz to 95 Hz. For example, if the set frequency is 100 Hz and the corrected frequency is 105 Hz, the calculation unit 341 performs the calculation using a frequency of 105 Hz.

[0174] The calculation unit 341 may be configured to correct the frequency based on at least one of the SOC, SOH, and temperature of the secondary battery 101.

[0175] The calculation unit 341 may be configured to calculate the impedance Z of the secondary battery 101 based on two different frequencies. That is, the calculation unit 341 configures the secondary battery 101 to be able to discharge and charge using only two different frequencies. In this configuration, the two different frequencies are, for example, a first frequency H1 and a second frequency H2.

[0176] The calculation unit 341 may be configured to calculate the impedance Z of the secondary battery 101 based on only three distinct frequencies. That is, the calculation unit 341 configures the secondary battery 101 to be able to discharge and charge based on only three distinct frequencies. In this configuration, the three distinct frequencies are, for example, a first frequency H1, a third frequency H3, and a second frequency H2.

[0177] The calculation unit 341 may be configured to calculate the impedance Z of the secondary battery 101 based on two or more different frequencies in the region where the imaginary part Z'' of the impedance Z is positive.

[0178] The calculation unit 341 may be configured to calculate the impedance Z of the secondary battery 101 based on six or more different frequencies.

[0179] The calculation unit 341 includes a switching circuit that switches the current path between the first energy storage capacitor 422 (first energy storage element) and the second energy storage capacitor 425 (second energy storage element). The switching circuit corresponds to the first MOS-FET 431 and the second MOS-FET 471 of the impedance calculation circuit 400. The switching circuit connects the first energy storage capacitor 422 and the second energy storage capacitor 425 in parallel or in series. The calculation unit 341 discharges the secondary battery 101 and stores energy in the parallel-connected first energy storage capacitor 422 and the second energy storage capacitor 425 while calculating the impedance Z of the secondary battery 101. The calculation unit 341 discharges the series-connected first energy storage capacitor 422 and the second energy storage capacitor 425 and charges the secondary battery 101 while calculating the impedance Z of the secondary battery 101.

[0180] The calculation unit 341 calculates the impedance Z of the secondary battery 101 based on the voltage and current values ​​of the secondary battery 101. The calculation unit 341 is configured to change the current value of the secondary battery 101 during discharge using the first variable current circuit 421 shown in Figure 1. The calculation unit 341 is configured to change the current value of the secondary battery 101 during charging using the second variable current circuit 461 shown in Figure 1.

[0181] (Measurement of voltage and current values ​​of secondary battery 101 for impedance Z calculation) The measurement of voltage and current values ​​of secondary battery 101 for impedance Z calculation will be explained with reference to Figure 2.

[0182] The first control unit 201 of the CCIC 200 measures the voltage value of the secondary battery 101 for the calculation of impedance Z. The current measuring unit 332 of the MPU 300 measures the current value of the secondary battery 101 for the calculation of impedance Z.

[0183] In principle, as shown in Figure 2, the first control unit 201 and the current measuring unit 332 discharge and charge the secondary battery 101 once each at a frequency corresponding to the Nth pulse, and measure the voltage and current values ​​of the secondary battery 101, respectively. Specifically, at the timing of measurement 1 (M1), the first control unit 201 and the current measuring unit 332 simultaneously measure the voltage value V1 and current value I1 of the secondary battery 101 during discharge, based on a frequency corresponding to the Nth pulse. The calculation unit 341 calculates the impedance of the secondary battery 101 based on a voltage value and current value of the secondary battery 101 in a pulse waveform represented by the amplitude and duty cycle associated with the discharge or charge of the secondary battery 101. That is, the voltage value V1 and current value I1 are measured simultaneously once for each pulse. Similarly, the first control unit 201 and the current measuring unit 332 simultaneously measure the voltage value V1 and current value I2 of the secondary battery 101 during charging, based on the frequency of the Nth pulse at the timing of measurement 2 (M2).

[0184] Next, the first control unit 201 and the current measuring unit 332 discharge and charge the secondary battery 101 once each at the other frequency of the (N+1)th pulse, and measure the voltage and current values ​​of the secondary battery 101, respectively. The other frequency of the (N+1)th pulse is lower than one of the frequencies of the Nth pulse. Specifically, at the timing of measurement 3 (M3), the first control unit 201 and the current measuring unit 332 simultaneously measure the voltage value V3 and current value I3 of the secondary battery 101 during discharge based on the other frequency related to the (N+1)th pulse. Similarly, at the timing of measurement 4 (M4), the first control unit 201 and the current measuring unit 332 simultaneously measure the voltage value V4 and current value I4 of the secondary battery 101 during charging based on the other frequency related to the (N+1)th pulse.

[0185] In this embodiment, the first control unit 201 and the current measuring unit 332 discharge and charge the secondary battery 101, for example, 10 times each, at the first frequency H1, and measure the voltage V and current I of the secondary battery 101. Next, the first control unit 201 and the current measuring unit 332 also discharge and charge the secondary battery 101 10 times each at the third frequency H3, the fourth frequency H4, the fifth frequency H5, and the second frequency H2, and measure the voltage V and current I of the secondary battery 101. The first control unit 201 and the current measuring unit 332 calculate the average value of the voltage V and current I for 10 discharge and charge cycles of the secondary battery 101 at the first frequency H1, the third frequency H3, the fourth frequency H4, the fifth frequency H5, and the second frequency H2.

[0186] The first control unit 201 and the current measuring unit 332 may be configured to measure the voltage value V and current value I only when the secondary battery 101 is discharging, for a first frequency H1, a third frequency H3, a fourth frequency H4, a fifth frequency H5, and a second frequency H2. Similarly, the first control unit 201 and the current measuring unit 332 may be configured to measure the voltage value V and current value I only when the secondary battery 101 is charging.

[0187] The first control unit 201 and the current measuring unit 332 may be configured to discharge and charge the secondary battery 101 once each for a first frequency H1, a third frequency H3, a fourth frequency H4, a fifth frequency H5, and a second frequency H2, and measure the voltage value V and current value I of the secondary battery 101 for each. In such a configuration, the first control unit 201 and the current measuring unit 332 repeat the above measurement for, for example, 10 times. The first control unit 201 and the current measuring unit 332 calculate the average value of the voltage value V and current value I for the 10 measurements.

[0188] (Estimation of electrolyte resistance Rs and charge transfer resistance Rct of secondary battery 101 using impedance Z calculation results) The estimation of electrolyte resistance Rs and charge transfer resistance Rct of secondary battery 101 using impedance Z calculation results will be explained with reference to Figure 7.

[0189] The estimation unit 342 of the MPU 300 estimates the electrolyte resistance value Rs and charge transfer resistance value Rct of the secondary battery 101 based on the calculated impedance Z of the secondary battery 101. The estimation unit 342 corresponds to the estimation step. Based on the input impedances Z, the estimation unit 342 simulates the waveform of a quadratic function that intersects the first axis at two or more points. As shown in Figure 7, the estimation unit 342 simulates the waveform of a quadratic function that intersects the first axis at two points based on five impedances Z: the first impedance Z1, the second impedance Z2, the third impedance Z3, the fourth impedance Z4, and the fifth impedance Z5. For example, the estimation unit 342 simulates the waveform of a quadratic function that intersects the first axis at two points based on the least squares method. The least squares method is a method for deriving the most likely relationship such that the sum of the squares of the errors between the measured value and the simulated value is minimized.

[0190] The estimation unit 342 estimates the electrolyte resistance Rs based on the value of the real part Z' of the impedance Z at the first point P1, which has a relatively higher frequency among the two points intersecting the first axis. The estimation unit 342 estimates the value of the real part Z' of the impedance Z at the first point P1 shown in Figure 7 as the electrolyte resistance Rs.

[0191] The estimation unit 342 estimates the charge transfer resistance value Rct based on the value of the real part Z' of the impedance Z at the second point P2, which has a relatively lower frequency among the two points intersecting the first axis. The estimation unit 342 estimates the charge transfer resistance value Rct as the value obtained by subtracting the value of the real part Z' of the impedance Z at the first point P1 from the value of the real part Z' of the impedance Z at the second point P2 shown in Figure 7.

[0192] The estimation unit 342 may be configured to estimate at least one of the electrolyte resistance value Rs and the charge transfer resistance value Rct of the secondary battery 101 based on the calculated impedance Z of the secondary battery 101.

[0193] The estimation unit 342 may estimate the charge transfer resistance value Rct as the value obtained by subtracting the value of the real part Z' of the impedance Z at the first point P1 and a predetermined value from the value of the real part Z' of the impedance Z at the second point P2.

[0194] The estimation unit 342 may simulate a quadratic function waveform that intersects the first axis at two points based on two impedances Z, a first impedance Z1 and a second impedance Z2. In this case, the waveform of a quadratic function that intersects the first axis at two points may be simulated by adding the values ​​of other impedances pre-stored in the MPU 300 to the two impedances Z, the first impedance Z1 and the second impedance Z2.

[0195] The estimation unit 342 may simulate a quadratic function waveform that intersects the first axis at two points based on three impedances Z: a ​​first impedance Z1, a second impedance Z2, and a third impedance Z3.

[0196] (Calculation method and device for secondary battery 101 using estimated electrolyte resistance Rs and charge transfer resistance Rct) The calculation method and device for secondary battery 101 calculate the impedance Z of the secondary battery 101 in order to estimate the electrolyte resistance Rs and charge transfer resistance Rct of the secondary battery 101 by simulating a part of the impedance waveform of the secondary battery 101 with a polynomial.

[0197] The calculation method for the secondary battery 101 reflects the technical concept of calculating the impedance Z of the secondary battery 101 and estimating the electrolyte resistance Rs and charge transfer resistance Rct of the secondary battery 101 using the calculation result of the impedance Z, in the configuration of the calculation method for the secondary battery 101. The calculation device for the secondary battery 101 is an embodiment of the calculation method for the secondary battery 101 and operates by introducing the program necessary for the calculation. In such a configuration, the secondary battery 101 is, for example, a recyclable secondary battery 101 removed from an electric vehicle.

[0198] (Inspection method and inspection apparatus for secondary battery 101 using estimated electrolyte resistance value Rs and charge transfer resistance value Rct) The inspection method and inspection apparatus for secondary battery 101 estimates the electrolyte resistance value Rs and charge transfer resistance value Rct of the secondary battery 101 by simulating a part of the impedance waveform of the secondary battery 101 using a polynomial, and inspects the secondary battery 101.

[0199] The method for inspecting the secondary battery 101 incorporates the technical concepts of calculating the impedance Z of the secondary battery 101 and estimating the electrolyte resistance Rs and charge transfer resistance Rct of the secondary battery 101 using the calculation results of the impedance Z, into the configuration of the inspection method for the secondary battery 101. The inspection device for the secondary battery 101 embodies the inspection method for the secondary battery 101. In this configuration, the secondary battery 101 is, for example, a recyclable secondary battery 101 removed from an electric vehicle.

[0200] (Control method and control device for secondary battery 101 using estimated electrolyte resistance Rs and charge transfer resistance Rct) The control method and control device for secondary battery 101 estimates the electrolyte resistance Rs and charge transfer resistance Rct of secondary battery 101 by simulating a part of the impedance waveform of secondary battery 101 using a polynomial, and uses these estimates for controlling secondary battery 101.

[0201] The control method for the secondary battery 101 incorporates the technical concepts of calculating the impedance Z of the secondary battery 101 and estimating the electrolyte resistance Rs and charge transfer resistance Rct of the secondary battery 101 using the calculation results of the impedance Z, and reflects these concepts in the configuration of the control method for the secondary battery 101. The control device for the secondary battery 101 is an embodiment of the control method for the secondary battery 101. In such a configuration, the secondary battery 101 is, for example, a secondary battery mounted in an electric vehicle.

[0202] The control unit controls the secondary battery 101 included in the battery pack 100. The control unit corresponds to a configuration that embodies the control steps. The control unit corresponds to, for example, the CCIC 200 and the MPU 300. The control unit charges and discharges the secondary battery 101 based on the electrolyte resistance value Rs and the charge transfer resistance value Rct estimated by the estimation unit 342. That is, the control unit calculates the degree of degradation of the secondary battery 101 based on, for example, the electrolyte resistance value Rs and the charge transfer resistance value Rct. Based on the degree of degradation of the secondary battery 101, the control unit sets the maximum allowable power of the secondary battery 101, etc., and charges and discharges the secondary battery 101.

[0203] The control unit may be configured to reflect the estimated electrolyte resistance Rs and charge transfer resistance Rct in the control of the secondary battery 101 if the difference between the internal resistance of the secondary battery 101 and the charge transfer resistance Rct estimated by the estimation unit 342 is less than or equal to a predetermined value. The internal resistance of the secondary battery 101 is correlated with the charge transfer resistance Rct of the secondary battery 101. In such a configuration, the MPU 300 calculates the internal resistance of the secondary battery 101. The control unit does not reflect the estimated electrolyte resistance Rs and charge transfer resistance Rct in the control of the secondary battery 101 if the difference between the internal resistance of the secondary battery 101 and the charge transfer resistance Rct estimated by the estimation unit 342 exceeds a predetermined value.

[0204] (Control method and control device for electric vehicle powered by secondary battery 101) The control method and control device for electric vehicle powered by secondary battery 101 is used in an electric vehicle that has electrical equipment and a power source that supplies power to the electrical equipment. The power source includes a secondary battery 101. The electrical equipment is an on-board motor 1004 and an air conditioner. The secondary battery 101 mounted on the electric vehicle is controlled by the method and control device for manufacturing the secondary battery 101.

[0205] (Configuration of the calculation unit 341, estimation unit 342, and control unit) In the embodiment and modified embodiments, the calculation unit 341 and estimation unit 342 are configured by an MPU 300, for example. In the embodiment, the control unit is configured by a CCIC 200 and an MPU 300, for example.

[0206] The calculation unit 341, the estimation unit 342, and the control unit may be configured by a single processing unit. The calculation unit 341, the estimation unit 342, and the control unit may be distributed across two or more processing units. The calculation unit 341, the estimation unit 342, and the control unit may each be configured by an independent processing unit.

[0207] The calculation unit 341, the estimation unit 342, and the control unit may each be composed of two or more independent processing units. Specifically, the calculation unit 341 may be composed of two independent processing units.

[0208] The processing unit corresponds to a computer, controller, and processor, etc. A computer corresponds to an electronic calculator.

[0209] The processing unit is composed of, for example, a microprocessing unit (MPU), a central processing unit (CPU), a cell controller integrated circuit (CCIC), a large-scale integrated circuit (LSI), or an integrated circuit (IC).

[0210] The processing unit may be configured by any combination of a microprocessing unit, a central processing unit, a cell control integrated circuit, a large-scale integrated circuit, and an integrated circuit, etc. Specifically, the processing unit may be configured by combining a microprocessing unit and a central processing unit.

[0211] The processing unit may be configured using one or more types of components, such as microprocessing units, central processing units, cell control integrated circuits, large-scale integrated circuits, and integrated circuits. Specifically, the processing unit may be configured using two microprocessing units. Similarly, the processing unit may be configured using two microprocessing units and one central processing unit.

[0212] The processing unit corresponds to the arithmetic unit, control unit, and controller, etc.

[0213] (Effects of the Embodiment) The effects of the embodiment will be explained with reference to Figure 7, etc.

[0214] The calculation method and calculation device for the secondary battery 101 calculate the impedance Z of the secondary battery 101 in order to estimate a predetermined resistance value of the secondary battery 101 by simulating a part of the impedance waveform of the secondary battery 101 using a polynomial. The calculation method and calculation device for the secondary battery 101 have a calculation unit 341 that calculates the impedance of the secondary battery 101 based on a predetermined frequency. The calculation unit 341 corresponds to a configuration that embodies the calculation steps. The polynomial is represented by a waveform using a first axis that shows the real part Z' of the impedance and a second axis that intersects the first axis and shows the imaginary part Z'' of the impedance Z.

[0215] The calculation unit 341 is configured to discharge and charge the secondary battery 101 using two or more variable frequencies that are different from each other. The calculation unit 341 calculates a first impedance Z1 at a first frequency H1 that is relatively higher than the frequencies in the negative region of the imaginary part Z'' of impedance Z, in the region where the imaginary part Z'' of impedance Z is positive. The calculation unit 341 calculates a second impedance Z2 at a second frequency H2 that is relatively lower than the first frequency H1, in the negative region of the imaginary part Z'' of impedance Z.

[0216] The first impedance Z1 and the second impedance Z2 are used to simulate the waveform of a polynomial that intersects the first axis at two or more points. A predetermined resistance value is estimated based on the value of the real part Z' of impedance Z at at least one of the two points where the polynomial waveform intersects the first axis.

[0217] The calculation device for the secondary battery 101 embodies the calculation method for the secondary battery 101. The calculation device for the secondary battery 101 operates by installing the program necessary for the calculation. The calculation method for the secondary battery 101 reflects the technical concept of calculating the impedance Z of the secondary battery 101 and estimating a predetermined resistance value of the secondary battery 101 using the calculation result of impedance Z.

[0218] As an example in this embodiment, the calculation device for the secondary battery 101 corresponds to a configuration that includes some of the functions of the CCIC 200 provided in the battery pack 100 and an impedance calculation circuit 400 that is not provided in the battery pack 100.

[0219] In one example of the embodiment, when the control unit is removed from the battery pack 100, the calculation device for the secondary battery 101 corresponds to a configuration that includes some of the functions of the CCIC 200 and the impedance calculation circuit 400.

[0220] In one example of this embodiment, the calculation device for the secondary battery 101 may be pre-installed in the battery pack 100. That is, an impedance calculation circuit 400 or the like may be pre-installed in the battery pack 100.

[0221] As an example in the embodiment, assuming that there is no battery pack 100 and the secondary battery 101 itself is to be tested, the calculation device for the secondary battery 101 corresponds to a configuration that includes some of the functions of the CCIC 200 and the impedance calculation circuit 400.

[0222] The calculation unit for the secondary battery 101 can calculate a predetermined resistance value of the secondary battery 101 based on a relatively small number of calculations for the first impedance Z1 and the second impedance Z2 of the secondary battery 101. Furthermore, when calculating the impedance Z of the secondary battery 101, the calculation unit for the secondary battery 101 calculates the impedance Z in the region where the imaginary part Z'' is positive at a relatively higher frequency than the impedance Z in the region where the imaginary part Z'' is negative. That is, the first impedance Z1 is calculated on the positive side of the imaginary part Z'' of impedance Z, and the second impedance Z2 is calculated on the negative side of the imaginary part Z'' of impedance Z. As a result, the accuracy of the calculation of the predetermined resistance value of the secondary battery 101 can be maintained regardless of the relatively small number of calculations. Therefore, the calculation unit for the secondary battery 101 can calculate the predetermined resistance value of the secondary battery 101 in a relatively short time while maintaining a predetermined accuracy.

[0223] The calculation device for the secondary battery 101 can be configured by combining an impedance calculation circuit 400 with a CCIC 200 provided in the battery pack 100. That is, the calculation device for the secondary battery 101 can be configured using general-purpose components for the CCIC 200, etc., and specialized components for the impedance calculation circuit 400, etc. The calculation device for the secondary battery 101 can be configured by retrofitting the impedance calculation circuit 400, etc., to an existing CCIC 200. The calculation device for the secondary battery 101 may have two or more CCIC 200s, and the configuration, including the connector for conductivity to the battery pack 100, may be distributed.

[0224] The calculation unit for the secondary battery 101 selects filter constants at timings such as measurement 1 (M1) shown in Figure 2, such as after the discharge or charge voltage related to the pulse waveform has sufficiently changed (saturated). The calculation unit for the secondary battery 101 selects a capacitor having filter constants corresponding to the discharge or charge frequency of the secondary battery 101. In the embodiment, in measurement 1 (M1) shown in Figure 2, etc., an electrical circuit used for controlling the voltage of the secondary battery 101, including a second filter capacitor 242, is used as in the embodiment. In measurement 1 (M1) shown in Figure 2, etc., an electrical circuit used for balancing the voltage of the secondary battery 101, including a third filter capacitor 262, may also be used. That is, measurement 1 (M1) shown in Figure 2 may be performed using an electrical circuit used for balancing the voltage of the secondary battery 101, including a third filter capacitor 262.

[0225] (1) The method and apparatus for inspecting a secondary battery 101 estimates a predetermined resistance value of the secondary battery 101 by simulating a part of the impedance waveform of the secondary battery 101 using a polynomial, and then inspects the secondary battery 101. The apparatus for inspecting the secondary battery 101 has a configuration in which an estimation unit 342 is added to the calculation unit of the secondary battery 101. The estimation unit 342 corresponds to a configuration that embodies the estimation step. The estimation unit 342 estimates a predetermined resistance value based on the calculated impedance Z. The estimation unit 342 is configured to simulate the waveform of a polynomial that intersects the first axis at two or more points based on two or more input impedances Z. The estimation unit 342 simulates the waveform of a polynomial based on a first impedance Z1 and a second impedance Z2. The estimation unit 342 corresponding to the estimation step estimates a predetermined resistance value based on the value of the real part Z' of the impedance Z at at least one of the two points where the polynomial waveform intersects the first axis.

[0226] The inspection device for the secondary battery 101 embodies the inspection method for the secondary battery 101. The inspection method for the secondary battery 101 reflects the technical concept of calculating the impedance Z of the secondary battery 101 and estimating a predetermined resistance value of the secondary battery 101 using the calculation result of the impedance Z.

[0227] As an example in the embodiment, the inspection device for the secondary battery 101 corresponds to a configuration that includes some of the functions of the CCIC 200 and MPU 300 provided in the battery pack 100, and an impedance calculation circuit 400 that is not provided in the battery pack 100.

[0228] As an example in the embodiment, when the control unit is removed from the battery pack 100, the inspection device for the secondary battery 101 corresponds to a configuration that includes some of the functions of the CCIC 200 and MPU 300, and the impedance calculation circuit 400.

[0229] In one example of this embodiment, the inspection device for the secondary battery 101 may be pre-installed in the battery pack 100. That is, an impedance calculation circuit 400 or the like may be pre-installed in the battery pack 100.

[0230] As an example in the embodiment, when inspecting the secondary battery 101 itself in the absence of a battery pack 100, the inspection device for the secondary battery 101 corresponds to a configuration that includes some of the functions of the CCIC 200 and MPU 300, as well as the impedance calculation circuit 400.

[0231] The secondary battery inspection device can calculate a predetermined resistance value of the secondary battery 101 based on the first impedance Z1 and the second impedance Z2 of the secondary battery 101. Therefore, the secondary battery inspection device can calculate a predetermined resistance value of the secondary battery 101 in a relatively short time while maintaining a predetermined accuracy. In other words, the secondary battery inspection device can inspect a relatively large number of secondary batteries 101 per unit time.

[0232] The method and apparatus for inspecting a secondary battery 101 can inspect the secondary battery 101 by charging and discharging it. In other words, the method and apparatus for inspecting a secondary battery 101 can inspect the secondary battery 101 without the secondary battery 101 receiving power from the generator of an electric vehicle or the like. The method and apparatus for inspecting a secondary battery 101 can inspect the secondary battery 101 when it has been removed from the electric vehicle.

[0233] The method and apparatus for inspecting secondary batteries 101 are intended for use, for example, in inspecting secondary batteries 101 intended for recycling. Specifically, the method and apparatus for inspecting secondary batteries 101 are intended for use, for example, in inspecting the condition of secondary batteries 101 contained in a battery pack 100 when the battery pack 100 removed from an electric vehicle is to be reused. According to the method and apparatus for inspecting secondary batteries 101, the state of deterioration of the secondary battery 101 can be inspected by estimating a predetermined resistance value of the secondary battery 101.

[0234] (2) The predetermined resistance value includes the electrolyte resistance value Rs of the secondary battery 101. The estimation unit 342 corresponding to the estimation step estimates the electrolyte resistance value Rs of the secondary battery 101 based on the value of the real part Z' of the impedance Z at the first point P1, which has a relatively higher frequency among the two points where the waveform of the quadratic function intersects the first axis. With this configuration, by estimating the electrolyte resistance value Rs of the secondary battery 101, the state of deterioration of the secondary battery 101 can be inspected based on the electrolyte resistance value Rs.

[0235] (3) The predetermined resistance value includes the charge transfer resistance value Rct of the secondary battery 101. The estimation unit 342 corresponding to the estimation step estimates the charge transfer resistance value Rct of the secondary battery 101 based on the value obtained by subtracting the value of the real part Z' of the impedance Z at the first point P1, which has a relatively higher frequency than the second point P2, which has a relatively lower frequency than the second point P2, where the waveform of the quadratic function intersects the first axis. With this configuration, by estimating the charge transfer resistance value Rct of the secondary battery 101, the state of deterioration of the secondary battery 101 can be inspected based on the charge transfer resistance value Rct.

[0236] (4) The charge transfer resistance value Rct of the secondary battery 101 includes a value due to the material of the positive electrode of the secondary battery 101 and a value due to the material of the negative electrode of the secondary battery 101. With this configuration, lithium composite oxide, which is an example of the active material of the positive electrode of the secondary battery 101, often has relatively lower electrical conductivity compared to the active material of the negative electrode. In this case, the active material of the positive electrode may affect the value of the impedance Z on the relatively lower frequency side along the first axis compared to the active material of the negative electrode. Also, with this configuration, graphite, which is an example of the active material of the negative electrode of the secondary battery 101, often has relatively higher electrical conductivity compared to the active material of the positive electrode. In this case, the active material of the negative electrode may affect the value of the impedance Z on the relatively higher frequency side along the first axis compared to the active material of the positive electrode.

[0237] (5) The polynomials are set to functions of degree three or higher. The coefficients of the second degree are set to be relatively larger than the coefficients of degree three or higher. With this configuration, for example, the waveform of the polynomial can be easily approximated to the Nyquist plot relating to the impedance of a secondary battery 101, such as a lithium-ion secondary battery. By making the coefficients of degree three or higher relatively small and defining the values ​​of the polynomials of degree three or higher, the values ​​of the second degree polynomials can also be defined.

[0238] (6) The coefficients of the quadratic function are set to be relatively larger than the coefficients of the linear function. With this configuration, it is possible to easily approximate the waveform of the polynomial with respect to the Nyquist plot relating to the impedance of a secondary battery 101, such as a lithium-ion secondary battery. When the coefficients of the linear function are set to 0, the polynomial becomes a quadratic function (quadratic curve).

[0239] (7) The polynomial is set up as a quadratic function. With this configuration, it is possible to easily approximate the waveform of the polynomial with respect to the Nyquist plot relating to the impedance of a secondary battery 101, such as a lithium-ion secondary battery.

[0240] (8) The calculation unit 341 corresponding to the calculation step sets the first frequency H1 such that the value of the real part Z' of the first impedance Z1 is relatively smaller than the value of the real part Z' of the second impedance Z2. With this configuration, the calculation unit 341 can calculate the first impedance Z1 with a relatively small value in the region where the imaginary part Z'' of the impedance Z is positive. With this configuration, it may be easier to approximate the polynomial waveform with respect to the Nyquist diagram relating to the impedance of the secondary battery 101.

[0241] (9) The calculation unit 341 corresponding to the calculation step sets the first frequency H1 such that the value of the real part Z' of the first impedance Z1 is 1 / 10 or less of the value of the real part Z' at the inflection point of the polynomial waveform, and greater than 0. With this configuration, the calculation unit 341 can calculate the first impedance Z1 with a relatively small value in the region where the imaginary part Z'' of the impedance Z is positive. With this configuration, it may be easier to approximate the polynomial waveform with respect to the Nyquist diagram relating to the impedance of the secondary battery 101.

[0242] (10) The calculation unit 341 corresponding to the calculation step calculates the second impedance Z2 in a relatively low-frequency region along the first axis, with the inflection point T of the polynomial waveform simulated by the estimation unit 342 corresponding to the estimation step as the boundary. With this configuration, the distance between the first impedance Z1 and the second impedance Z2 can be relatively widened along the first axis, which is the real part Z' of the impedance of the secondary battery 101. Furthermore, with this configuration, the first impedance Z1 and the second impedance Z2 are set with the inflection point of the polynomial as the boundary. For this reason, with this configuration, the accuracy of fitting the first impedance Z1 and the second impedance Z2 to the polynomial can be improved. Here, if the polynomial is a quadratic function, one inflection point T occurs. On the other hand, if the polynomial is a cubic function, for example, two inflection points T occur. Of the two inflection points T that occur, the choice of which inflection point T to select is determined based on the Nyquist diagram relating to the impedance of the secondary battery 101, which is determined for each type of battery.

[0243] (11) The calculation unit 341 corresponding to the calculation step calculates the second impedance Z2 in a relatively high-frequency region along the first axis, with the inflection point T of the polynomial waveform simulated by the estimation unit 342 corresponding to the estimation step as the boundary. With this configuration, the second impedance Z2 can be calculated in a relatively short time.

[0244] (12) The calculation unit 341 corresponding to the calculation step calculates a third impedance Z3 based on a third frequency H3 that is different from the second frequency H2 in the region where the imaginary part Z'' of impedance Z is negative. The estimation unit 342 simulates the waveform of a polynomial that intersects the first axis at two or more points based on the first impedance Z1, the second impedance Z2, and the third impedance Z3. With this configuration, the accuracy of fitting impedance Z to polynomials can be improved by increasing the number of calculations for impedance Z.

[0245] (13) The calculation unit 341 corresponding to the calculation step calculates the first impedance Z1 in one region along the first axis, with respect to the inflection point T of the polynomial waveform simulated by the estimation unit 342 corresponding to the estimation step. The calculation unit 341 calculates the second impedance Z2 in the other region along the first axis. With this configuration, since the first impedance Z1 and the second impedance Z2 exist with respect to the inflection point of the polynomial, the accuracy of fitting the first impedance Z1 and the second impedance Z2 to the polynomial can be improved.

[0246] (14) The calculation unit 341 corresponding to the calculation step sets a first frequency H1 and a second frequency H2 based on the type of positive electrode active material and the type of negative electrode active material of the secondary battery 101. With this configuration, the electrolyte resistance value Rs and charge transfer resistance value Rct of various types of secondary batteries 101 can be estimated with high accuracy.

[0247] (15) Multiple secondary batteries 101 are electrically connected. The calculation unit 341 corresponding to the calculation step calculates the impedance of at least one secondary battery 101. The estimation unit 342 corresponding to the estimation step estimates a predetermined resistance value of the secondary battery 101 calculated by the calculation unit 341. The predetermined resistance value is, for example, the electrolyte resistance value Rs or the charge transfer resistance value Rct. With this configuration, the secondary batteries 101 can be inspected without disassembling the battery pack 100 containing multiple secondary batteries 101 and removing the secondary batteries 101. In other words, with this configuration, it is suitable to inspect the secondary batteries 101 without disassembling the battery pack 100 and then recycle the battery pack 100 in its original state.

[0248] In such a configuration, if the battery pack 100 is provided with a control unit, that control unit may be repurposed as a testing device for the secondary battery 101. The control unit is, for example, a CCIC 200 and an MPU 300. That is, the testing device for the secondary battery 101 may include the CCIC 200 and MPU 300 provided in the battery pack 100, and an impedance calculation circuit 400 that is not provided in the battery pack 100.

[0249] Furthermore, in such a configuration, only one or more secondary batteries 101 included in the battery pack 100 may be selectively inspected. The variation in degradation of multiple secondary batteries 101 included in the same battery pack 100 is estimated to be relatively small. On the other hand, the variation in degradation of multiple secondary batteries 101 included in different battery packs 100 is estimated to be relatively large. This is because the usage history of each secondary battery 101 differs from one battery pack 100 to the other. If the battery pack 100 is performing balancing control, the variation in degradation of the secondary batteries 101 included in the battery pack 100 may be relatively very small. The ratio of degradation of the electrolyte resistance value Rs and the charge transfer resistance value Rct in different secondary batteries 101 is estimated to be about the same. In other words, it is not essential to inspect all secondary batteries 101 included in the battery pack 100. Therefore, a configuration in which only one or more secondary batteries 101 included in the battery pack 100 are inspected is also possible.

[0250] Furthermore, in a modified version of this configuration, if an impedance calculation circuit 400 is provided in the battery pack 100 in addition to the CCIC 200 and MPU 300, the battery pack 100 itself can function as a testing device for the secondary battery 101.

[0251] (16) The secondary batteries 101 are electrically connected to each other by connecting members, or electrically connected to external members. The predetermined resistance value includes the electrolyte resistance value Rs of the secondary batteries 101 and the ohmic resistance value of the connecting members. The estimation unit 342 corresponding to the estimation step estimates the sum of the electrolyte resistance value Rs and the ohmic resistance value based on the value of the real part Z' of the impedance Z at the first point P1, which has a relatively higher frequency, among the two points where the waveform of the quadratic function intersects the first axis. The connecting members correspond to busbars in the battery pack 100. The busbars are inter-cell busbars and end busbars. Inter-cell busbars are busbars that electrically connect adjacent secondary batteries 101 to each other. End busbars are busbars that electrically connect the high-voltage secondary batteries 101 of the stacked secondary batteries 101 to external members (such as the positive electrode busbar on the electric vehicle side). Furthermore, the end busbar is a busbar that electrically connects the low-voltage secondary battery 101 of the stacked secondary batteries 101 to an external component. That is, the sum of the electrolyte resistance value Rs and the ohmic resistance value of the busbar is estimated to be the first point P1. With this configuration, the value of the electrolyte resistance value Rs can be estimated with high accuracy.

[0252] (17) The calculation unit 341 corresponding to the calculation step calculates the impedance Z of the secondary battery 101 based on the voltage and current values ​​of the secondary battery 101 obtained via a measuring instrument that is in contact with the secondary battery 101. The impedance Z of the measuring instrument is known. The estimation unit 342 corresponding to the estimation step estimates the charge transfer resistance value Rct of the secondary battery 101 based on the value obtained by subtracting the value of the real part Z' of the impedance Z at the first point P1, which has a relatively higher frequency than the second point P2, and the electrical resistance value caused by the measuring instrument, from the value of the real part Z' of the impedance Z at the second point P2, which has a relatively lower frequency than the second point P2, where the waveform of the quadratic function intersects the first axis. The measuring instrument corresponds to, for example, a detection harness in the method and apparatus for inspecting the secondary battery 101. The electrical resistance value corresponds to the impedance of the detection harness. Since the detection harness is a probe for inspection, its impedance is known. With this configuration, the charge transfer resistance value Rct of the secondary battery 101 can be estimated by excluding the impedance value caused by the detection harness.

[0253] (18) The calculation unit 341 corresponding to the calculation step calculates the impedance Z of the secondary battery 101 based on the voltage value and current value of the secondary battery 101 obtained by different electrical paths. The different electrical paths correspond to electrical paths in which the cables connected to the detection harness are separated for voltage measurement of the secondary battery 101 and for current measurement of the secondary battery 101. In this embodiment, the voltage value of the secondary battery 101 is measured by the CCIC 200 and the current value of the secondary battery 101 is measured by the impedance calculation circuit 400. With this configuration, the voltage measurement value and the current measurement value of the secondary battery 101 do not interfere with each other, and noise associated with the measurement can be suppressed.

[0254] In a modified embodiment, the voltage and current values ​​of the secondary battery 101 may be obtained using the same electrical path. This same electrical path corresponds to an electrical path in which the cable connected to the detection harness is shared for measuring the voltage of the secondary battery 101 and for measuring the current of the secondary battery 101. In this modified configuration, the length of the detection harness is made relatively shorter in order to suppress interference between the voltage and current measurements of the secondary battery 101.

[0255] (19) The calculation unit 341 corresponding to the calculation step calculates the impedance of the secondary battery 101 based on the voltage and current values ​​of two or more secondary batteries 101 acquired at two or more timings in a single pulse waveform represented by the amplitude and duty cycle associated with the discharge or charge of the secondary battery 101. With this configuration, even if the waveform of one pulse is not an ideal rectangular waveform, but a curved waveform such as a sine wave, the effect can be suppressed. Specifically, when measuring the voltage value V1 and current value I1 during the discharge of the secondary battery 101 at the timing of measurement 1 (M1) shown in Figure 2, even if the pulse waveform is a curved waveform rather than a rectangular waveform as shown in Figure 2, the measurement error can be reduced by measuring the voltage value V1 and current value I1 multiple times at different measurement timings. The voltage value V1 and current value I1 measured multiple times are, for example, calculated as average values.

[0256] The calculation unit 341 corresponding to the calculation step is configured to discharge and charge the secondary battery 101. The calculation unit 341 includes a first energy storage capacitor 422 (energy storage element) and a second energy storage capacitor 425 (energy storage element) for storing power. The calculation unit 341 calculates the impedance Z of the secondary battery 101 while discharging from the secondary battery 101 and storing power in the first energy storage capacitor 422 and the second energy storage capacitor 425. The calculation unit 341 calculates the impedance Z of the secondary battery 101 while discharging from the first energy storage capacitor 422 and the second energy storage capacitor 425 and charging the secondary battery 101. With this configuration, the power discharged from the secondary battery 101 can be used as regenerative energy to charge the secondary battery 101. For example, 70% to 80% of the power discharged from the secondary battery 101 can be used to charge the secondary battery 101. Therefore, when testing the secondary battery 101 while repeatedly discharging it, it is possible to suppress or eliminate the need to supply power to the secondary battery 101 from an external source. In particular, when the secondary battery 101 configured as a battery pack 100 is tested and recycled after being removed from an electric vehicle, it is preferable that external power supply is unnecessary during testing, as power cannot be supplied from the electric vehicle.

[0257] The energy storage element includes a first energy storage capacitor 422 (first energy storage element) and a second energy storage capacitor 425 (second energy storage element). The calculation unit 341 corresponding to the calculation step includes a switching circuit that switches the current path between the first energy storage capacitor 422 and the second energy storage capacitor 425. In the embodiment shown in Figures 1 and 2, the switching circuit is a first MOS-FET 431 and a second MOS-FET 471. In the modified embodiment shown in Figures 3 and 4, the switching circuit is a first MOS-FET 431, a second MOS-FET 471, and a third MOS-FET 531. The switching circuit connects the first energy storage capacitor 422 and the second energy storage capacitor 425 in parallel or in series. The calculation unit 341 discharges from the secondary battery 101 and stores energy in the parallel-connected first energy storage capacitor 422 and second energy storage capacitor 425 while calculating the impedance Z. The calculation unit 341 calculates the impedance Z while discharging the secondary battery 101 by discharging from the first and second energy storage capacitors 422 and 425, which are connected in series. With this configuration, when the power discharged from the secondary battery 101 is used to charge the secondary battery 101, the voltage and current values ​​of the power used to charge the secondary battery 101 can be adjusted. Since it is not possible to use the power discharged from the secondary battery 101 to charge the secondary battery 101 without any loss, it is preferable to be able to adjust the voltage and current values ​​of the power used to charge the secondary battery 101. In particular, with this configuration, the power discharged from the secondary battery 101 and stepped down can be used to charge the secondary battery 101 after being boosted by the first and second energy storage capacitors 422 and 425, which have been changed from parallel to series connection.

[0258] Switching circuits such as the first MOS-FET 431, the second MOS-FET 471, and the third MOS-FET 531 can have their internal transistors function as charge pumps. That is, the switching circuit can arbitrarily change the duty cycle of one pulse when calculating the impedance Z of the secondary battery 101 based on the voltage and current values ​​of the secondary battery 101.

[0259] In the embodiments shown in Figures 1 and 2, the calculation unit 341 corresponding to the calculation step calculates the impedance Z of the secondary battery 101 based on the voltage value and current value of the secondary battery 101. The calculation unit 341 is configured to change the current value during discharge of the secondary battery 101 by the first current adjustment unit 440. The calculation unit 341 is configured to change the current value during charging of the secondary battery 101 by the second current adjustment unit 480. With this configuration, the current value input to the secondary battery 101 can be changed according to the characteristics of the secondary battery 101 being tested.

[0260] (20) The control device for the secondary battery 101 is a device that simulates a part of the impedance waveform of the secondary battery 101 using a polynomial, estimates a predetermined resistance value of the secondary battery 101, and controls the secondary battery 101. The control device for the secondary battery 101 has a configuration that adds a control unit to the inspection device for the secondary battery 101. The control unit corresponds to a configuration that embodies the control steps. The control unit is, for example, a CCIC200 or an MPU300. The control unit is configured to charge and discharge the secondary battery 101 based on the estimated predetermined resistance value.

[0261] The control device for the secondary battery 101 embodies the control method for the secondary battery 101. The control method for the secondary battery 101 reflects the technical concept of calculating the impedance Z of the secondary battery 101 and estimating a predetermined resistance value of the secondary battery 101 using the calculation result of the impedance Z.

[0262] (21) The calculation unit 341 corresponding to the calculation step sets the first frequency H1 and the second frequency H2, etc., to be relatively lower based on the usage history and degradation information of the secondary battery 101. With this configuration, it is possible to accommodate the fact that the Nyquist plot relating to the impedance Z of the secondary battery 101 shifts relatively to the lower frequency side as the degradation of the secondary battery 101 increases. The Nyquist plot relating to the impedance Z of the secondary battery 101 shifts to the right on the first axis shown in Figure 7 as the degradation of the secondary battery 101 increases. In other words, it is possible to accommodate the fact that the Nyquist plot relating to the impedance Z of the secondary battery 101 shifts overall toward the right on the first axis shown in Figure 7 as the cumulative operating time of the secondary battery 101 increases. The timing of setting the first frequency H1 and the second frequency H2, etc. is determined based on the state of overheardiness (SOH) of the secondary battery 101 and the cumulative operating time of the battery pack 100.

[0263] (22) The calculation unit 341 corresponding to the calculation step is set so that the interval between the first frequency H1 and the second frequency H2 is relatively wide. With this configuration, the Nyquist diagram relating to the impedance Z of the secondary battery 101 can correspond to the fact that the width of the arc along the first axis in Figure 7 relatively increases as the degradation of the secondary battery 101 increases. In other words, the longer the cumulative operating time of the secondary battery 101, the wider the arc in the Nyquist diagram relating to the impedance Z of the secondary battery 101 becomes.

[0264] (23) The calculation unit 341 corresponding to the calculation step calculates the internal resistance value of the secondary battery 101. The control unit reflects the estimated predetermined resistance value in the control of the secondary battery 101 if the difference between the internal resistance value and the estimated predetermined resistance value is less than or equal to a predetermined value. With this configuration, it is possible to decide whether or not to reflect the estimated predetermined resistance value in the control of the secondary battery 101 in accordance with the accuracy of the predetermined resistance value estimated by the estimation unit 342. The predetermined resistance value is, for example, the charge transfer resistance value Rct. That is, the internal resistance value of the secondary battery 101 is correlated with the charge transfer resistance value Rct of the secondary battery 101.

[0265] (24) Multiple secondary batteries 101 are electrically connected. The calculation unit 341 corresponding to the calculation step calculates the impedance of at least one secondary battery 101. The estimation unit 342 corresponding to the estimation step estimates a predetermined resistance value of the secondary battery 101 calculated by the calculation unit 341. The predetermined resistance value is, for example, the electrolyte resistance value Rs or the charge transfer resistance value Rct. With this configuration, the calculation load can be reduced in the control device for the secondary battery 101 by suppressing the number of secondary batteries 101 whose impedance is calculated.

[0266] (25) The power supply control device for electric vehicles is an embodiment of the method for controlling the power supply of electric vehicles. The power supply control device for electric vehicles is used in electric vehicles that have electrical equipment and a power supply that supplies power to the electrical equipment. The power supply includes a secondary battery 101. The secondary battery 101 is controlled by the control device for the secondary battery 101.

[0267] The power control unit for the electric vehicle can calculate a predetermined resistance value of the secondary battery 101 based on the first impedance Z1 and the second impedance Z2 of the secondary battery 101. Therefore, the power control unit for the electric vehicle can calculate the predetermined resistance value of the secondary battery 101 relatively quickly while maintaining a predetermined accuracy. As a result, the electric vehicle can run in a manner that reflects the predetermined resistance value of the secondary battery 101, corresponding to the required calculation speed. The power control unit for the electric vehicle can set the maximum allowable voltage value and maximum allowable current value of the secondary battery 101 based on the estimated predetermined resistance value of the secondary battery 101. The power control unit for the electric vehicle performs the same control as the control unit for the secondary battery 101.

[0268] (Other Embodiments) The embodiments are described in detail or in a simplified manner to make the present invention easier to understand, and it is not necessary to have all the configurations described, or to have configurations that are not shown. In addition, some of the configurations of the embodiments may be deleted, replaced with configurations of other embodiments, or combined with configurations of other embodiments.

[0269] In the embodiment, the calculation device, inspection device, and control device for the secondary battery 101 were described as being configured to inspect a battery pack 100 containing multiple secondary batteries 101. In the embodiment, if the multiple secondary batteries 101 included in the battery pack 100 are balanced, it is conceivable that the difference in the degradation state of the multiple secondary batteries 101 included in the same battery pack 100 will be relatively small. On the other hand, in the embodiment, it is conceivable that the difference in the degradation state of the secondary batteries 101 included in different battery packs 100 will be relatively large due to the difference in the usage conditions of the battery pack 100 in different electric vehicles, etc. The present invention is not limited to such embodiments. The calculation device, inspection device, and control device for the secondary battery of the present invention may also be configured to inspect a single secondary battery.

[0270] In the secondary battery calculation device and inspection device of the present invention, the configuration may be such that all secondary batteries or any secondary batteries are inspected without removing multiple secondary batteries from the battery pack. Any secondary battery may be the high-voltage secondary battery, the low-voltage secondary battery, or any other secondary battery among multiple secondary batteries connected in series. Alternatively, the secondary battery calculation device and inspection device of the present invention may be such that all secondary batteries or any secondary batteries are inspected with multiple secondary batteries removed from the battery pack.

[0271] In the calculation device, inspection device, and control device for the secondary battery 101 of the embodiment, the electrolyte resistance value Rs and the charge transfer resistance value Rct of the secondary battery 101 are estimated. The present invention is not limited to this embodiment. In the calculation device, inspection device, and control device for the secondary battery of the present invention, the configuration may be such that at least one of the electrolyte resistance value and the charge transfer resistance value of the secondary battery is estimated. For example, in the calculation device, inspection device, and control device for the secondary battery of the present invention, the configuration may be such that only the charge transfer resistance value of the secondary battery is estimated.

[0272] In the calculation device, inspection device, and control device for the secondary battery 101 of the embodiment, the calculation unit 341 is configured to discharge and charge the secondary battery 101 using two or more different variable frequencies. The present invention is not limited to this embodiment. In the calculation device, inspection device, and control device for the secondary battery of the present invention, the calculation unit 341 may be configured to at least discharge or charge the secondary battery 101 using two or more different variable frequencies. For example, the calculation unit 341 may be configured to only discharge the secondary battery 101 using two or more different variable frequencies.

[0273] In the arithmetic unit, inspection device, and control device of the secondary battery 101 of the embodiment, the polynomial is expressed as a quadratic function. The present invention is not limited to this embodiment. In the arithmetic unit, inspection device, and control device of the secondary battery 101 of the embodiment, a configuration combining two or more polynomials is also possible. In the case of a configuration combining two or more polynomials, different polynomials may be combined on the high-frequency side and the low-frequency side of the real part of the impedance separated by an inflection point. In the case of a configuration combining two or more polynomials, polynomials of different orders may be combined.

[0274] The secondary battery 101 in this embodiment is composed of a ternary lithium-ion secondary battery. The present invention is not limited to this embodiment. The secondary battery of the present invention may be, for example, a lithium iron phosphate secondary battery. Similarly, the secondary battery of the present invention may be an all-solid-state battery.

[0275] 100 Battery pack, 101 Secondary battery, 102 Thermistor, 103 First wiring, 200 CCIC (control unit), 200L First communication line, 201 First control unit, 201L Second communication line, 202 Second control unit, 202L Third communication line, 211 Second wiring, 212 Third wiring, 213 Fourth wiring, 221 First resistor, 222 First filter capacitor, 231 Fifth wiring, 232 Sixth wiring, 241 Second resistor, 242 Second filter capacitor, 251 Seventh wiring, 252 Eighth wiring, 261 Third resistor, 262 Third filter capacitor, 300 MPU (control unit), 311 Power supply control unit, 312 Voltage control unit, 313 Temperature measurement unit, 321 SOC calculation unit, 322 SOH calculation unit, 323 memory unit, 331 measurement timing control unit, 332 current measurement unit, 341 calculation unit, 342 estimation unit, 400 impedance calculation circuit, 411 11th wiring, 412 12th wiring, 413 13th wiring, 421 first variable current circuit, 421A first transistor, 421B second transistor, 421C first resistor, 421D second resistor, 422 first energy storage capacitor (energy storage element, first energy storage element), 423 current measurement circuit, 423L fourth communication line, 424 first rectifier element, 425 second energy storage capacitor (energy storage element, second energy storage element), 431 first MOS-FET (switching circuit), 431L fifth communication line, 440 first current adjustment unit, 441 Resistor, 442 Transistor, 443 First operational amplifier, 444 First converter, 445 Resistor, 461 Second variable current circuit, 461A First transistor, 461B Second transistor, 461C First resistor, 461D Second resistor, 462 Second rectifier element, 471 Second MOS-FET (switching circuit), 471L Sixth communication line, 480 Second current adjustment section, 483 Second operational amplifier, 484 Second converter, 500 Impedance calculation circuit, 521 First constant current circuit, 521A First transistor, 521B Second transistor, 521C First resistor, 521D Second resistor,531 Third MOS-FET (switching circuit), 531L Third communication line, 541 Second constant current circuit, 541A First transistor, 541B Second transistor, 541C First resistor, 541D Second resistor, 1001 Switch, 1002 Relay, 1003 Inverter, 1004 Automotive motor, H1 First frequency, H2 Second frequency, H3 Third frequency, H4 Fourth frequency, H5 Fifth frequency, P1 First point (electrolyte resistance value Rs), P2 Second point (electrolyte resistance value Rs + charge transfer resistance value Rct), Z Impedance, Z' Real part, Z'' Imaginary part, Z1 First impedance, Z2 Second impedance, Z3 Third impedance, Z4 Fourth impedance, Z5 Fifth impedance, T Inflection point, Rs electrolyte resistance value (predetermined resistance value), Rct charge transfer resistance value (predetermined resistance value).

Claims

1. A method for inspecting a secondary battery by simulating a portion of the impedance waveform of the secondary battery using a polynomial, the method comprising: a calculation step of calculating the impedance of the secondary battery based on a predetermined frequency; and an estimation step of estimating a predetermined resistance value based on the calculated impedance, wherein the polynomial is represented by a waveform using a first axis representing the real part of the impedance and a second axis intersecting the first axis and representing the imaginary part of the impedance, the calculation step calculates a first impedance at a first frequency that is relatively higher than the frequency in the region where the imaginary part of the impedance is negative, in the region where the imaginary part of the impedance is positive, and calculates a second impedance at a second frequency that is relatively lower than the first frequency, in the region where the imaginary part of the impedance is negative, and the estimation step simulates the waveform of the polynomial that intersects the first axis at two or more points based on two or more input impedances. A method for inspecting a secondary battery, comprising: simulating the waveform of the polynomial based on the first impedance and the second impedance; and estimating a predetermined resistance value based on the value of the real part of the impedance at at least one of the two points.

2. The method for inspecting a secondary battery according to claim 1, wherein the predetermined resistance value includes the electrolyte resistance value of the secondary battery, and the estimation step estimates the electrolyte resistance value based on the real part of the impedance at the first point of the two points having a relatively higher frequency.

3. The method for inspecting a secondary battery according to claim 1, wherein the predetermined resistance value includes the charge transfer resistance value of the secondary battery, and the estimation step estimates the charge transfer resistance value based on a value obtained by subtracting the value of the real part of the impedance at the first point, which has a relatively higher frequency, from the value of the real part of the impedance at the second point, which has a relatively lower frequency, of the two points.

4. The method for inspecting a secondary battery according to claim 3, wherein the charge transfer resistance value includes a value attributable to the material of the positive electrode of the secondary battery and a value attributable to the material of the negative electrode of the secondary battery.

5. The method for inspecting a secondary battery according to claim 1, wherein the polynomial is set to a function of degree three or higher, and the coefficient of the second degree is set to be relatively larger than the coefficient of degree three or higher.

6. The method for inspecting a secondary battery according to claim 5, wherein the coefficient of the secondary coefficient is set to be relatively larger than the coefficient of the primary coefficient.

7. The method for inspecting a secondary battery according to claim 1, wherein the polynomial is set to a quadratic function.

8. The method for inspecting a secondary battery according to claim 1, wherein the calculation step involves setting the first frequency such that the real part of the first impedance is relatively smaller than the real part of the second impedance.

9. The method for inspecting a secondary battery according to claim 1, wherein the calculation step is to set the first frequency such that the value of the real part of the first impedance is less than or equal to 1 / 10 of the value of the real part at the inflection point of the waveform of the polynomial, and greater than 0.

10. The method for inspecting a secondary battery according to claim 1, wherein the calculation step calculates the second impedance in a relatively low-frequency region along the first axis, with respect to the inflection point of the waveform of the polynomial simulated by the estimation step.

11. The method for inspecting a secondary battery according to claim 1, wherein the calculation step calculates the second impedance in a relatively high-frequency region along the first axis, with respect to the inflection point of the waveform of the polynomial simulated by the estimation step.

12. The method for inspecting a secondary battery according to claim 1, wherein the calculation step calculates a third impedance based on a third frequency different from the second frequency in the region where the imaginary part of the impedance is negative, and the estimation step simulates the waveform of the polynomial that intersects the first axis at two or more points based on the first impedance, the second impedance, and the third impedance.

13. The method for inspecting a secondary battery according to claim 1, wherein the calculation step involves calculating a first impedance in a region on one side along the first axis, with respect to the inflection point of the waveform of the polynomial simulated by the estimation step, and calculating a second impedance in a region on the other side along the first axis.

14. The method for inspecting a secondary battery according to claim 1, wherein the calculation step sets the first frequency and the second frequency based on at least one of the type of positive electrode active material and the type of negative electrode active material of the secondary battery.

15. A method for inspecting a secondary battery according to claim 1, wherein the secondary battery is electrically connected in multiple locations, the calculation step calculates the impedance of at least one of the secondary batteries, and the estimation step estimates a predetermined resistance value of the secondary battery calculated by the calculation step.

16. The secondary battery is electrically connected to each other by connecting members, or electrically connected to an external member, the predetermined resistance value includes the electrolyte resistance value of the secondary battery and the ohmic resistance value of the connecting member, and the estimation step estimates the sum of the electrolyte resistance value and the ohmic resistance value based on the value of the real part of the impedance at the first of the two points where the frequency is relatively higher, the method for inspecting a secondary battery according to claim 1.

17. The method for inspecting a secondary battery according to claim 1, wherein the calculation step calculates the impedance of the secondary battery based on the voltage and current values ​​of the secondary battery obtained through a measuring instrument that is in contact with the secondary battery, the impedance of the measuring instrument is known, and the estimation step estimates the charge transfer resistance of the secondary battery based on the value obtained by subtracting the value of the real part of the impedance at the first point, which has a relatively higher frequency than the other of the two points, and the electrical resistance value at the measuring instrument, from the value of the real part of the impedance at the second point, which has a relatively lower frequency than the other of the two points.

18. The method for inspecting a secondary battery according to claim 1, wherein the calculation step involves calculating the impedance of the secondary battery based on the voltage and current values ​​of the secondary battery obtained by different electrical paths.

19. The method for inspecting a secondary battery according to claim 1, wherein the calculation step involves calculating the impedance of the secondary battery based on two or more voltage values ​​and current values ​​of the secondary battery acquired at two or more timings in a single pulse waveform represented by the amplitude and duty cycle associated with the discharge or charge of the secondary battery.

20. A method for controlling a secondary battery by simulating a portion of the impedance waveform of the secondary battery using a polynomial, the method comprising: a calculation step of calculating the impedance of the secondary battery based on a predetermined frequency; an estimation step of estimating a predetermined resistance value based on the calculated impedance; and a control step of controlling the secondary battery based on the estimated predetermined resistance value, wherein the polynomial is represented by a waveform using a first axis representing the real part of the impedance and a second axis intersecting the first axis and representing the imaginary part of the impedance, the calculation step calculates a first impedance at a first frequency that is relatively higher than the frequency in the region where the imaginary part of the impedance is negative, in the region where the imaginary part of the impedance is positive, and calculates a second impedance at a second frequency that is relatively lower than the first frequency, in the region where the imaginary part of the impedance is negative, and the estimation step is A method for controlling a secondary battery, comprising: simulating the waveform of the polynomial that intersects the first axis at two or more points based on two or more input impedances; simulating the waveform of the polynomial based on the first impedance and the second impedance; estimating a predetermined resistance value based on the real part of the impedance at at least one of the two points; and the control step being configured to charge and discharge the secondary battery based on the estimated predetermined resistance value.

21. The method for controlling a secondary battery according to claim 20, wherein the calculation step is to set the first frequency and the second frequency to be relatively lower based on at least one of the information of the secondary battery's usage history and degradation.

22. The method for controlling a secondary battery according to claim 21, wherein the calculation step is set such that the interval between the first frequency and the second frequency is relatively wide.

23. The method for controlling a secondary battery according to claim 20, wherein the calculation step calculates the internal resistance value of the secondary battery, and the control step reflects the estimated predetermined resistance value in the control of the secondary battery when the difference between the internal resistance value and the estimated predetermined resistance value is less than or equal to a predetermined value.

24. A secondary battery control method according to claim 20, wherein a plurality of secondary batteries are electrically connected, the calculation step performs calculations on at least one of the secondary batteries, the estimation step performs estimations on the secondary batteries calculated by the calculation step, and the control step performs calculations on the secondary batteries estimated by the estimation step.

25. A method for controlling the power supply of an electric vehicle, which is used in an electric vehicle having an electrical device and a power supply that supplies power to the electrical device, wherein the power supply includes a secondary battery, and the secondary battery is controlled by the secondary battery control method described in claim 20.

Images