JP2010048656A - Devie and methof of measuring battery deterioration - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery deterioration measuring device and a measuring method capable of accurately measuring the battery deterioration. <P>SOLUTION: The one end of a battery 10 is connected to the one end of a discharge control unit 14 through an ammeter 12. The other end of the battery 10 is connected to the other end of the discharge control unit 14. The ammeter 12 measures the current flowing to the battery 10 and outputs the measured result to an analysis unit 18. A voltmeter 16 measures the output voltage of the battery 10 and outputs the measured result to the analysis unit 18. The discharge control unit 14 controls the current flowing in the battery 10 based on the control of the analysis unit 18. The analysis unit 18 discharges the battery 10 by the discharge control unit 14, and measures the deterioration of the battery 10 based on the ratio of the time integration value of the battery output voltage to the time integration value of the battery current. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus and a method for measuring the degree of deterioration of a battery based on the output voltage and current of the battery.

  Motor-driven vehicles such as hybrid vehicles and electric vehicles are widely used. A battery for supplying electric power to the motor is mounted on the motor-driven vehicle. As this battery, a lithium ion battery or the like that can be repeatedly charged and discharged is used. The battery mounted on the motor-driven vehicle supplies power to the motor and is charged by regenerative braking power generation of the motor.

JP 2006-338944 A

  In a battery, by repeatedly charging and discharging, ions in the electrolyte solution are unevenly distributed, and the internal resistance may increase. As a result, the electric power that can be output by the battery is reduced, which may affect the running performance of the vehicle.

  Therefore, a method has been devised in which the ratio of the time change of the battery output voltage to the time change of the battery current is measured as the internal resistance of the battery, and the degree of deterioration of the battery is measured based on the increase of the internal resistance. Thus, even when the output voltage does not change linearly with respect to changes in battery current, the internal resistance of the battery can be defined and measured. However, according to this method, during a period in which the battery current is constant, the time change of the battery current that becomes a denominator when the internal resistance is obtained becomes extremely small, and it is difficult to accurately obtain the internal resistance. This makes it difficult to measure the degree of deterioration of the battery.

  The present invention has been made for such a problem. That is, an object of the present invention is to provide a battery deterioration degree measuring device and a measuring method capable of accurately measuring the degree of battery deterioration.

  The present invention relates to a battery deterioration degree measuring apparatus for measuring a battery deterioration degree, a difference voltage measuring unit that measures a difference voltage between a reference voltage and an output voltage of the battery, and a voltage integration for obtaining a time integral value of the difference voltage. A current measuring unit that measures a current flowing through the battery, a current integrating unit that obtains a time integrated value of a measured current in a time zone in which the voltage integrating unit performs time integration, and a time integrated value of the difference voltage An evaluation reference value setting unit that obtains a ratio of the time integral value of the battery current in the time zone in which the time integral value is obtained for the battery before deterioration, and sets the ratio as an evaluation reference value; and the current integration unit A measurement unit that measures the degree of deterioration of the battery based on the ratio of the time integration value obtained by the voltage integration unit to the time integration value obtained by the method and the evaluation reference value. .

  Further, in the battery deterioration degree measuring apparatus according to the present invention, the battery deterioration degree measuring apparatus includes a temperature detection unit that detects the temperature of the battery, and the evaluation reference value acquisition unit acquires the evaluation reference value corresponding to the temperature of the battery, The measurement unit is based on a ratio of the time integration value obtained by the voltage integration unit to the time integration value obtained by the current integration unit and the evaluation reference value corresponding to the temperature detected by the temperature detection unit. It is preferable to perform the measurement.

  The battery deterioration degree measuring apparatus according to the present invention further includes an open-circuit voltage measuring unit that measures the open-circuit voltage of the battery, wherein the reference voltage is an open-circuit voltage measured by the open-circuit voltage measuring unit, and the difference is determined. It is preferable that the voltage measuring unit measures a voltage obtained by subtracting the output voltage of the battery from the open voltage measured by the open voltage measuring unit as the difference voltage.

  The battery deterioration degree measuring apparatus according to the present invention further includes an output voltage measuring unit that measures the output voltage of the battery, and the open-circuit voltage measuring unit includes measurement results of the current measuring unit and the output voltage measuring unit. It is preferable to obtain the open-circuit voltage based on the above.

  According to another aspect of the present invention, there is provided a battery degradation level measuring method for measuring a degradation level of a battery, a voltage integration step for obtaining a time integral value of a difference voltage between a reference voltage and the output voltage of the battery, and a time integration of the difference voltage. A current integration step for obtaining a time integral value of the current flowing through the battery in a time zone to be performed, and a ratio of the time integral value of the battery current in the time zone in which the time integral value is obtained with respect to the time integral value of the difference voltage, An evaluation reference value setting step for acquiring the battery before deterioration and setting the ratio as an evaluation reference value, and a ratio of the time integration value obtained by the voltage integration step to the time integration value obtained by the current integration step And a measuring step for measuring the degree of deterioration of the battery based on the evaluation reference value.

  ADVANTAGE OF THE INVENTION According to this invention, the battery deterioration degree measuring apparatus and measuring method which can detect the deterioration degree of a battery correctly can be provided.

  FIG. 1 shows a configuration of a battery deterioration degree measuring apparatus according to an embodiment of the present invention. The battery deterioration degree measuring device discharges the battery 10 by the discharge controller 14 and measures the deterioration degree of the battery 10 based on the ratio of the time integral value of the battery output voltage to the time integral value of the battery current. The battery 10 to be measured is a secondary battery such as a lithium ion battery or a nickel metal hydride battery.

  One end of the battery 10 is connected to one end of the discharge control unit 14 via the ammeter 12. The other end of the battery 10 is connected to the other end of the discharge control unit 14. The ammeter 12 measures the current flowing through the battery 10 and outputs the measurement result to the analysis unit 18. The voltmeter 16 measures the output voltage of the battery 10 and outputs the measurement result to the analysis unit 18. The discharge controller 14 controls the current flowing through the battery 10 based on the control of the analyzer 18.

  The analysis unit 18 controls the discharge control unit 14 so that a current having a predetermined time waveform flows through the battery 10 during a certain time t1 to time t2. FIG. 2A shows an example of a time waveform of the battery current. The horizontal axis represents time, and the vertical axis represents the battery current when the direction flowing into the positive electrode terminal of the battery 10 is positive. FIG. 2A shows that the current of −I0 flows to the battery 10 between time t1 and time t2 by the discharge control unit 14. In the case of a battery used for a motor-driven vehicle, for example, I0 = 200 A, and the time from time t1 to time t2 is, for example, 3 seconds to 10 seconds. FIG. 2B shows a time waveform of the output voltage of the battery 10 when the current shown in FIG. In FIG. 2B, the horizontal axis indicates time, and the vertical axis indicates output voltage. When the battery 10 is used for a motor-driven vehicle and is composed of a plurality of cells, the open output voltage per cell is 3 V to 4 V, and the range of the vertical axis in FIG. When the output voltage for one cell is expressed, it is approximately 2.8V to 4V. However, the output voltage of the battery targeted by the present invention is not limited to this range. Since the internal resistance of the battery 10 does not follow Ohm's law, the output voltage of the battery 10 does not necessarily have the same value for the same battery current value.

  The principle by which the battery deterioration measuring device according to the present embodiment measures the degree of battery deterioration will be described. In general, when a current having a time waveform shown in FIG. 2A is supplied to a battery, a battery having a large degree of deterioration tends to have a larger change in output voltage than a battery having a small degree of deterioration. FIG. 3 shows this state. The voltage waveform L0 shows initial characteristics. Here, the initial characteristics refer to characteristics when the battery is not deteriorated, for example, characteristics when the battery satisfies the design characteristics such as immediately after manufacture. The voltage waveforms L1, L2, and L3 in FIG. 3 indicate that the discharge from time t1 to time t2 by the current waveform shown in FIG. 2A is one discharge, and the number of discharges is in the order of voltage waveforms L1, L2, and L3. This is a characteristic when increased. From this, it can be seen that the change in the output voltage increases as the discharge is repeated and the degree of deterioration of the battery increases.

  In the present embodiment, the battery 10 is discharged and the ratio of the voltage integral value to the current integral value is obtained as the evaluation value. Here, the current integration value is a value obtained by integrating the battery current over time with the integration start time t0 when the magnitude of the battery current exceeds a predetermined measurement start threshold A. The integrated current value represents the area of a region sandwiched between the straight line indicating the threshold value -A and the current waveform in FIG. The integrated voltage value is a value obtained by integrating the difference voltage obtained by subtracting the output voltage of the battery 10 from the reference voltage Vs with the integration start time t0 when the magnitude of the battery current exceeds a predetermined measurement start threshold A. is there. Here, the reference voltage Vs is a value set in order to determine the deterioration of the battery 10, and for example, an open circuit voltage (OCV) of the battery 10 is set. The setting of the reference voltage Vs will be described later. The voltage integral value represents the area of a region sandwiched between the straight line indicating the reference voltage Vs in FIG. 3 and the output voltage waveform.

FIG. 4 shows an evaluation value-integration time characteristic in which the horizontal axis represents the integration time and the vertical axis represents the evaluation value. A characteristic line E0 indicates an initial characteristic. When the evaluation value is obtained based on the values of the battery current and the output voltage exemplified above, the range of the vertical axis in FIG. 4 is 0 to 6 × 10 ⁻³ . The characteristic line E2 is a characteristic for a battery in which the number of discharges is larger than the number of discharges of the battery for which the characteristic line E1 is obtained. As can be seen from FIG. 4, the evaluation value increases as the discharge is repeated and the deterioration degree of the battery increases. Therefore, the degree of deterioration of the battery can be measured by obtaining the evaluation value of the battery and obtaining the degree of increase from the initial evaluation value. The evaluation value is a ratio of the voltage integral value to the current integral value. Therefore, if the current integral value is a significant value, an evaluation value with a small error can be obtained even when the time change of the current is small.

  In addition, even if the battery current fluctuates between time t1 and time t2, the evaluation value is almost the same value as when the battery current takes a constant value between time t1 and time t2. It has been confirmed. The solid line in FIG. 5 (a) shows the same battery current waveform as in FIG. 2 (a), and the broken line in FIG. 5 (a) shows the case where the current value is intentionally varied between time t1 and time t2. The battery current waveform of is shown. The characteristic indicated by the solid line in FIG. 5B shows the evaluation value-integral time characteristic obtained with respect to the battery current indicated by the solid line in FIG. 5A, and the characteristic indicated by the broken line in FIG. The evaluation value-integral time characteristic calculated | required with respect to the battery current shown with the broken line of a) is shown.

  Based on such a principle, the process which a battery deterioration measuring apparatus performs is demonstrated. FIG. 6 is a flowchart showing processing executed by the analysis unit 18. When the magnitude of the measured current value output by the ammeter 12 exceeds the measurement start threshold A, the analysis unit 18 starts integration of the measured current value output by the ammeter 12 with the integration start time t0 as that time. . Then, a current integrated value-integral time characteristic indicating a current integrated value with respect to the integration time is obtained (S101). Further, the analysis unit 18 obtains a difference voltage obtained by subtracting the measured voltage value output from the voltmeter 16 from the reference voltage Vs, and starts integration of the difference voltage from the reference time t0. Then, a voltage integrated value-integral time characteristic indicating a voltage integrated value with respect to the integration time is obtained (S102).

  The analysis unit 18 obtains an evaluation value-integral time characteristic obtained by dividing the voltage integral value at each time of the voltage integral value-integral time characteristic by the current integral value of the current integral value-integral time characteristic at the corresponding time (S103). ).

  The initial characteristic storage unit 20 stores an initial characteristic of an evaluation value-integral time characteristic. This stored content is stored in advance when the battery deterioration measuring apparatus is manufactured. The analysis unit 18 reads the initial characteristic of the evaluation value-integral time characteristic from the initial characteristic storage unit 20 (S104). The analysis unit 18 subtracts the evaluation value at the comparison reference time td in the evaluation value-integration time characteristic read in step S104 from the evaluation value at the comparison reference time td in the evaluation value-integration time characteristic obtained in step S103. The determined determination value D is obtained (S105). Here, the comparison reference time td is a time that can be arbitrarily set within the integration time range. The integration end time is suitable as the comparison reference time td. The analysis unit 18 determines whether or not the determination value D exceeds a predetermined threshold B (S106). When the determination value D exceeds the predetermined threshold B, information indicating that the battery 10 has deteriorated and the determination value D are output to the display unit 22 (S107, S108). On the other hand, when the determination value D is less than or equal to the predetermined threshold B, the determination value D is output to the display unit 22 (S108). The display unit 22 displays the information output from the analysis unit 18.

  According to such processing, it is possible to detect the deterioration of the battery 10 based on whether or not the evaluation value at the comparison reference time td is larger than the predetermined threshold B than the initial evaluation value. Further, the determination value D can be displayed on the display unit 22. The determination value D indicates that the greater the value, the greater the degree of deterioration of the battery. A user of the motor-driven vehicle, a maintenance inspector, and the like can know the degree of deterioration of the battery 10 based on the determination value D.

  Here, the evaluation value-integration time characteristic is obtained based on the current integral value-integration time characteristic and the voltage integral value-integration time characteristic, and the determination is made based on the evaluation value at the comparison reference time td of the evaluation value-integration time characteristic. The process for acquiring the value D has been described. In addition to such processing, the current integrated value and voltage integrated value from the time when the magnitude of the measured current value output by the ammeter 12 exceeds the measurement start threshold A to the comparison reference time td are obtained, and the current of the voltage integrated value is obtained. A ratio to the integral value may be obtained as an evaluation value. In this case, a value obtained by subtracting the initial evaluation value from the evaluation value may be a value indicating the degree of deterioration of the battery.

  As described above, the analysis unit 18 measures the degree of deterioration of the battery 10 using a value obtained by integrating the value obtained by subtracting the measured value of the output voltage of the battery 10 from the reference voltage Vs. The output voltage of the battery 10 varies depending on various conditions such as the battery current history as well as the battery current during the processing of the analysis unit 18. Therefore, it is preferable to set the reference voltage Vs as follows.

  In FIG. 7A, the horizontal axis represents time, and the vertical axis represents the measured voltage value of the voltmeter 16 and the measured current value of the ammeter 12. The voltmeter 16 and the ammeter 12 shall measure discretely with respect to time. The black circle in FIG. 7A indicates the measured voltage value, and the white circle indicates the measured current value. A solid line connecting black circles and a broken line connecting white circles are obtained by interpolating measured values in order to grasp discretely measured values as continuous ones.

  The analysis unit 18 measures the measured current value −I1 when the measured current value exceeds the measurement start threshold A, the measured current value −I0 output immediately before the measured current value −I1, and the measured current value. Output voltage-battery current characteristics shown in FIG. 7 (b) based on the measured voltage value V1 when the magnitude exceeds the measurement start threshold A and the measured voltage value V0 output immediately before the measured voltage value V1. Is obtained as a reference voltage Vs. The reference voltage Vs corresponds to the open voltage of the battery 10. This characteristic is obtained from the output voltage-battery current characteristic when it is assumed that the battery 10 has an internal resistance according to Ohm's law. The output voltage-battery current characteristic is expressed by a linear equation connecting a point where the output voltage is V0 and the battery current is -I0 and a point where the output voltage is V1 and the battery current is -I1. The analysis unit 18 obtains the vertical axis intercept of this straight line using the measured current values -I0 and -I1 and the measured voltage values V0 and V1.

  In the above description, the change in the evaluation value-integral time characteristic based on the temperature change of the battery 10 is not considered. However, in order to perform more rigorous measurement, it is preferable to consider the change of the evaluation value-integration time characteristic according to the temperature of the battery 10. Therefore, FIG. 8 shows a configuration of a battery deterioration measuring apparatus according to an application example that performs measurement in consideration of the temperature of the battery 10. The same components as those of the battery deterioration measuring apparatus in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  The battery thermometer 24 measures the temperature of the battery 10 and outputs the measurement result to the analysis unit 18. The initial characteristic storage unit 20 stores initial characteristics of evaluation value-integral time characteristics for a plurality of temperatures. This initial characteristic is stored in advance at the time of manufacture. FIG. 9 shows an example of evaluation value-integration time characteristics stored for temperatures T1, T2, and T3. These temperatures have a relationship of T1 <T2 <T3. As shown in FIG. 9, the evaluation value decreases as the temperature of the battery increases.

  In step S <b> 104 shown in FIG. 6, the analysis unit 18 reads the initial characteristic of the evaluation value-integral time characteristic corresponding to the temperature of the battery 10 based on the measurement result of the battery thermometer 24.

  According to such a configuration and processing, it is possible to measure the degree of deterioration of the battery 10 using the initial characteristic of the evaluation value-integral time characteristic according to the temperature of the battery 10. As a result, more accurate measurement can be performed.

  Next, the hybrid vehicle drive system according to the present embodiment will be described. FIG. 10 shows the configuration of the hybrid vehicle drive system. This vehicle drive system uses the measurement result of the battery deterioration detection device for control of a hybrid vehicle. The same components as those of the battery deterioration measuring apparatus in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  The operation unit 34 includes an accelerator, a brake, and a gear change lever, and outputs a driving operation command to the control unit 26. The control unit 26 controls the engine 32 and the motor control unit 28 based on the traveling state of the hybrid vehicle and the driving operation command.

  The engine 32 drives the hybrid vehicle according to the control of the control unit 26. The motor control unit 28 supplies the electric power of the battery 10 to the motor 30 and supplies the regenerative braking generated electric power of the motor 30 to the battery 10 under the control of the control unit 26. The motor 30 accelerates or regeneratively brakes the hybrid vehicle according to the control of the motor control unit 28.

  With such a configuration, the hybrid vehicle drive system adjusts the contribution of the motor 30 to the vehicle drive force and the contribution of the engine 32 to the vehicle drive force based on the traveling state of the hybrid vehicle and the driving operation command, and energy Increase efficiency.

  In the hybrid vehicle drive system according to the present embodiment, the analysis unit 18 outputs the determination value D to the control unit 26. The control unit 26 adjusts the contribution of the motor 30 to the vehicle driving force and the contribution of the engine 32 to the vehicle driving force according to the determination value D. That is, when the determination value D increases, the contribution of the motor 30 and the engine 32 to the vehicle driving force is adjusted so that the contribution of the motor 30 to the vehicle driving force is limited. For example, when the determination value D exceeds a predetermined value, the motor control unit 28 is controlled so that electric power of a predetermined value or more is not supplied from the battery 10 to the motor 30, and the driving force of the engine 32 is increased instead.

  According to such a system configuration, even if the power supply performance is reduced due to deterioration of the battery 10 and the motor driving force is reduced, the driving force of the engine 32 can compensate for the reduction. As a result, it is possible to avoid a decrease in the running performance of the hybrid vehicle.

It is a figure which shows the structure of the battery deterioration measuring apparatus which concerns on embodiment. It is a figure which shows a battery current waveform and the output voltage of a battery. It is a figure which shows the tendency of the output voltage at the time of battery deterioration. It is a figure which shows an evaluation value-integral time characteristic. It is a figure which shows the battery current waveform at the time of changing the value of an electric current intentionally, and the evaluation value-integral time characteristic with respect to it. It is a flowchart which shows the process which an analysis part performs in a battery deterioration measurement. It is a figure explaining the setting of a reference voltage. It is a figure which shows the structure of the battery deterioration measuring apparatus which concerns on an application example. It is a figure which shows the initial characteristic of the evaluation value-integral time characteristic about several temperature. It is a figure showing composition of a hybrid vehicle drive system concerning an embodiment.

Explanation of symbols

  10 battery, 12 ammeter, 14 discharge control unit, 16 voltmeter, 18 analysis unit, 20 initial characteristic storage unit, 22 display unit, 24 battery thermometer, 26 control unit, 28 motor control unit, 30 motor, 32 engine, 34 Operation unit.

Claims (5)

In a battery deterioration measuring device that measures the deterioration of a battery,
A differential voltage measuring unit for measuring a differential voltage between a reference voltage and the output voltage of the battery;
A voltage integrating unit for obtaining a time integral value of the difference voltage;
A current measuring unit for measuring a current flowing through the battery;
A current integrating unit for obtaining a time integrated value of a measured current in a time zone in which the voltage integrating unit performs time integration;
An evaluation reference value for obtaining a ratio of the time integral value of the battery current in the time zone in which the time integral value is obtained with respect to the time integral value of the difference voltage for the battery before deterioration, and setting the ratio as an evaluation reference value A setting section;
A measurement unit that measures the degree of deterioration of the battery based on the ratio of the time integration value obtained by the voltage integration unit to the time integration value obtained by the current integration unit and the evaluation reference value;
A battery deterioration degree measuring apparatus comprising: In the battery deterioration measuring device according to claim 1,
A temperature detection unit for detecting the temperature of the battery;
The evaluation reference value acquisition unit
Obtaining the evaluation reference value corresponding to the temperature of the battery;
The measuring unit is
Performing a measurement based on a ratio of the time integration value obtained by the voltage integration unit to the time integration value obtained by the current integration unit and the evaluation reference value corresponding to the temperature detected by the temperature detection unit. A battery deterioration degree measuring device. In the battery deterioration measuring device according to claim 1 or 2,
An open-circuit voltage measuring unit for measuring the open-circuit voltage of the battery;
The reference voltage is
The open circuit voltage measured by the open circuit voltage measurement unit,
The differential voltage measurement unit includes:
A battery deterioration degree measuring apparatus that measures a voltage obtained by subtracting an output voltage of the battery from an open circuit voltage measured by the open circuit voltage measuring unit as the difference voltage. In the battery deterioration measuring device according to claim 3,
An output voltage measuring unit for measuring the output voltage of the battery;
The open-circuit voltage measurement unit
A battery deterioration degree measuring apparatus, wherein an open circuit voltage is obtained based on measurement results of the current measuring unit and the output voltage measuring unit. In the battery deterioration degree measuring method for measuring the battery deterioration degree,
A voltage integration step for obtaining a time integral value of a difference voltage between a reference voltage and the output voltage of the battery;
A current integration step for obtaining a time integration value of a current flowing through the battery in a time zone for performing the time integration of the differential voltage;
An evaluation reference value for obtaining a ratio of the time integral value of the battery current in the time zone in which the time integral value is obtained with respect to the time integral value of the difference voltage for the battery before deterioration, and setting the ratio as an evaluation reference value Configuration steps;
A measurement step of measuring the degree of deterioration of the battery based on the ratio of the time integration value obtained by the voltage integration step to the time integration value obtained by the current integration step and the evaluation reference value;
A battery deterioration degree measuring method comprising:

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