JP2010019664A - Battery deterioration detection device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and a method for detecting deterioration in a battery used for a motor drive vehicle, or the like. <P>SOLUTION: An analysis section 14 obtains estimated full charging capacities Qab, Qbc, Qcd corresponding to three open voltage variation ranges. The analysis section 14 obtains a first determination value D1 obtained by subtracting the estimated full charging capacity Qab from the estimated full charging capacity Qbc, and further obtains a second determination value D2 obtained by subtracting the estimated full charging capacity Qbc from the estimated full charging capacity Qcd. The analysis section 14 determines whether the first determination value D1 is larger than a prescribed threshold T1 and the second determination value D2 is larger than a prescribed threshold T2. When the first determination value D1 is larger than the prescribed threshold T1 and the second determination value D2 is larger than the prescribed threshold T2, the analysis section 14 stores information on detection of a lithium deposition phenomenon in a fault information storage section 22, and the analysis section 14 operates a warning device 24. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus and a method for detecting battery deterioration based on changes in charge / discharge characteristics.

  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. A lithium ion battery is widely used as this battery. Lithium ion batteries can be repeatedly charged and discharged. A lithium ion battery used in a motor-driven vehicle supplies power to the motor and is charged by regenerative braking power generation of the motor.

  When a lithium ion battery is used under severe conditions such as charging with an excessive current, lithium is deposited on the electrode. Such a lithium deposition phenomenon may reduce the power supply performance of the lithium ion battery and may reduce the running performance of the motor-driven vehicle.

  The present invention has been made for such a problem. That is, an object of the present invention is to provide an apparatus and method for detecting deterioration of a battery used in a motor-driven vehicle or the like.

  The present invention provides an OCV measuring means for measuring the open circuit voltage of a battery, and for each range of a plurality of preset open circuit voltage ranges, the variation value of the charging depth with respect to the variation within the open circuit voltage range of the measured open circuit voltage is opened. SOC fluctuation acquisition means determined based on initial characteristics of charge depth with respect to voltage, current integration means for determining a charge / discharge current integrated value of the battery for fluctuations in measured open voltage within each open voltage range, and determined charge depth Based on the fluctuation value and the integrated charge / discharge current value, a full charge capacity estimating means for obtaining an estimated full charge capacity for each open voltage range, and the battery based on the estimated full charge capacity obtained for each open voltage range. Deterioration detecting means for detecting deterioration.

  Moreover, in the battery deterioration detection apparatus according to the present invention, it is preferable that the deterioration detection means detects the deterioration of the battery based on a difference of the estimated full charge capacity obtained for each open voltage range.

  Further, in the battery deterioration detection device according to the present invention, the battery is a lithium ion battery, and the deterioration detection means causes a difference in the estimated full charge capacity for each open voltage range and a lithium precipitation phenomenon. It is preferable to detect the lithium precipitation phenomenon based on a comparison with the difference in the case.

  Further, the present invention is mounted on a motor-driven vehicle, and in the battery deterioration detection device in which the battery supplies power to a driving motor, the motor-driven vehicle limits a range of charging depth of the battery to a predetermined range. A charge state limiting unit is provided, and the plurality of open voltage ranges are open voltage ranges determined based on a charge depth range limited by the charge state limit unit.

  Moreover, in the battery deterioration detection apparatus according to the present invention, it is preferable to include a charge / discharge unit that changes an open circuit voltage of the battery.

  Further, the present invention provides a step of measuring the open circuit voltage of the battery, and for each range of a plurality of preset open circuit voltage ranges, the variation value of the charging depth with respect to the variation within the open circuit voltage range of the measured open circuit voltage is opened. A step of obtaining based on an initial characteristic of a charge depth with respect to a voltage, a step of obtaining a charge / discharge current integrated value of a battery with respect to a change in a measured open voltage within each open voltage range, and a obtained charge depth fluctuation value and charge / discharge Determining an estimated full charge capacity for each open voltage range based on the integrated current value; and detecting deterioration of the battery based on the estimated full charge capacity determined for each open voltage range. It is characterized by that.

  According to the present invention, it is possible to detect deterioration of a battery that can be charged and discharged, such as a lithium ion battery.

  FIG. 1 shows a configuration of a vehicle drive system with a battery deterioration detection function according to an embodiment of the present invention. The vehicle drive system with a battery deterioration detection function is mounted on a motor-driven vehicle using a lithium ion battery, and detects a lithium deposition phenomenon in the lithium ion battery. The detection of the lithium precipitation phenomenon is performed based on the deterioration of the charge / discharge performance that appears with use.

  When the vehicle drive system with the battery deterioration detection function detects the lithium deposition phenomenon, an estimated value of the full charge capacity of the lithium ion battery 10 is obtained. Therefore, here, a basic technique for obtaining an estimated value of the full charge capacity will be described. The OCV measurement unit 12 measures the open voltage of the lithium ion battery 10 and outputs the measurement result to the analysis unit 14. Here, the open circuit voltage is an output voltage of the lithium ion battery 10 in a state where no current flows through the lithium ion battery 10 such as when the motor-driven vehicle is stopped, and is generally referred to as OCV (Open Circuit Voltage). The ammeter 16 measures the current flowing through the battery with the direction flowing into the positive terminal of the battery as positive, and outputs the measurement result to the analysis unit 14.

  The analysis unit 14 obtains the integrated value of the battery current from the time when the open circuit voltage is a certain voltage V1 to the time when the voltage V2 is different from the voltage V1 as the charge amount fluctuation. The charge amount variation indicates the amount of charge that is charged / discharged in the lithium ion battery 10 until the open circuit voltage changes from V1 to V2.

  The OCV-SOC characteristic storage unit 20 stores an initial characteristic (OCV-SOC initial characteristic) of the charging depth with respect to the open-circuit voltage for the lithium ion battery 10 to be measured. Here, the charge depth is a value representing the ratio of the charge amount to the full charge capacity as a percentage, and is generally referred to as SOC (State Of Charge). The initial characteristics refer to characteristics when the lithium precipitation phenomenon does not occur in the lithium ion battery 10, for example, characteristics when the lithium ion battery 10 satisfies the design characteristics such as immediately after manufacture.

The analysis unit 14 refers to the OCV-SOC initial characteristics stored in the OCV-SOC characteristic storage unit 20, and sets the charging depth corresponding to the open circuit voltage V1 and the open circuit voltage V2 to the first charge depth and the second charge, respectively. Find as depth. Then, the SOC variation obtained by subtracting the first charging depth from the second charging depth is obtained. The analysis unit 14 obtains a value obtained by multiplying the value obtained by dividing the charge amount variation by the SOC variation by 100 as the estimated value of the full charge capacity. That is, the estimated full charge capacity is obtained based on the following (Equation 1).
(Equation 1) Estimated full charge capacity (Ah) = charge amount fluctuation (Ah) × 100 / SOC fluctuation

  Here, the value obtained in (Equation 1) is set as the “estimated value” by using the OCV-SOC initial characteristics even when the characteristics of the lithium ion battery 10 are changed. This is because the value obtained based on the actual value may deviate from the true full charge capacity. The vehicle drive system with a battery deterioration detection function obtains an estimated full charge capacity as the open circuit voltage changes from V1 to V2 through such processing.

  The lithium ion battery 10 is connected to the motor driving device 18 to supply electric power to the motor driving device 18 or to be charged by regenerative braking power generation of the motor driving device 18. The open circuit voltage of the lithium ion battery 10 varies as the motor-driven vehicle travels. The analysis unit 14 calculates the estimated full charge capacity based on the above processing with respect to fluctuations of the open-circuit voltage in each of the predetermined open-circuit voltage ranges Va to Vb, Vb to Vc, and Vc to Vd. Ask. These voltages are assumed to have a relationship of Va <Vb <Vc <Vd. For example, when the voltages Vα and Vβ have a relationship Va ≦ Vα <Vβ ≦ Vb, the open circuit voltage increases from the voltage Vα to the voltage Vβ or decreases from the voltage Vβ to the voltage Vα as the motor-driven vehicle travels. When, the analysis part 14 calculates | requires an estimated full charge capacity based on the fluctuation | variation of the open circuit voltage V (alpha) -V (beta). By the same processing, the analysis unit 14 obtains an estimated full charge capacity with respect to an open-circuit voltage fluctuation within the range of the open-circuit voltages Vb to Vc and an open-circuit voltage fluctuation within the range of the open-circuit voltages Vc to Vd.

  The vehicle drive system with a battery deterioration detection function detects a lithium deposition phenomenon based on an estimated full charge capacity obtained corresponding to each open-circuit voltage fluctuation range. Hereinafter, the detection principle will be described.

  FIG. 2 shows the characteristics of the open circuit voltage OCV with respect to the charge amount of the lithium ion battery 10. The horizontal axis indicates the amount of charge, and the vertical axis indicates the open circuit voltage. The solid line indicates the initial characteristics, and the broken line indicates the characteristics after the lithium precipitation phenomenon occurs. The charge amount QF indicates the initial full charge capacity. The open circuit voltage VF indicates the open circuit voltage when fully charged. The open circuit voltage VE indicates a charge amount lower limit value (a value at which it is difficult to obtain practical power). The full charge capacity QG after the lithium precipitation phenomenon occurs is reduced by Δ with respect to the initial full charge capacity QF (hereinafter, the expression “after the lithium precipitation phenomenon has occurred” is simply referred to as “after lithium precipitation”. .)

  FIG. 3 shows the charge depth characteristics (OCV-SOC characteristics) with respect to the open-circuit voltage of the lithium ion battery 10. The horizontal axis indicates the charging depth, and the vertical axis indicates the open circuit voltage. The solid line shows the initial characteristics, and the broken line shows the characteristics after lithium deposition. The state where the charge depth is 100% in the initial stage corresponds to the state where the charge amount in FIG. 2 has reached the full charge capacity QF, and the state where the charge depth is 100% after lithium deposition is the charge amount shown in FIG. Corresponds to the state of reaching QG. Therefore, the characteristic of FIG. 3 corresponds to the characteristic obtained by converting the horizontal axis of the characteristic of FIG. 2 from the charge amount to the charge depth. A hybrid vehicle may include a state-of-charge limiting unit that limits the range of battery charging depth to a predetermined range. In this case, a lithium ion battery is often used within a range of a charging depth of 40% to 80%. FIG. 4A shows an enlarged OCV-SOC characteristic in the range of 40% to 80% charge depth.

  In FIG. 4B, the characteristics after lithium deposition in FIG. 4A are slid in the positive direction of the charging depth in order to overlap the characteristics after lithium deposition with the initial characteristics. The open-circuit voltages Va, Vb, Vc, and Vd are open-circuit voltages that delimit the open-circuit voltage range according to the relationship between the slope of the characteristics after lithium deposition and the slope of the initial characteristics. When the open circuit voltage is in the range of Va to Vb, the slope after lithium deposition is larger than the initial slope. In addition, when the open circuit voltage is in the range of Vb to Vc, the slopes are substantially the same after lithium deposition and in the initial stage. In the range of the open circuit voltage from Vc to Vd, the slope after lithium deposition is smaller than the initial slope.

  When obtaining the estimated full charge capacity based on (Equation 1), the analysis unit 14 refers to the OCV-SOC initial characteristics to determine the SOC variation relative to the open circuit voltage variation, regardless of whether or not the lithium deposition phenomenon has occurred. Ask. Therefore, in the open-circuit voltage range from Va to Vb in which the slope of the OCV-SOC characteristic is increased due to the lithium precipitation phenomenon, the analysis unit 14 obtains an SOC fluctuation larger than the true value of the SOC fluctuation. In addition, in the open-circuit voltage range of Vb to Vc in which no change is observed in the slope of the OCV-SOC characteristic due to the lithium precipitation phenomenon, the analysis unit 14 obtains the SOC fluctuation close to the true value of the SOC fluctuation. Then, in the open circuit voltage range of Vc to Vd where the slope of the OCV-SOC characteristic is reduced due to the lithium precipitation phenomenon, the analysis unit 14 obtains an SOC fluctuation smaller than the true value of the SOC fluctuation. Moreover, since the charge amount variation obtained by the analysis unit 14 is based on the time integration value of the battery current, it is substantially equal to the actual charge amount that is charged or discharged regardless of whether or not the lithium deposition phenomenon has occurred.

  Therefore, after lithium deposition, the estimated full charge capacity Qab obtained by the analysis unit 14 within the open voltage range of Va to Vb is the estimated full charge capacity Qbc obtained by the analysis unit 14 within the open voltage range of Vb to Vc. Smaller than. Further, after lithium deposition, the estimated full charge capacity Qcd obtained by the analysis unit 14 within the open-circuit voltage range of Vc to Vd is larger than the estimated full charge capacity Qbc.

  The vehicle drive system with a battery deterioration detection function according to the present embodiment detects the lithium deposition phenomenon using such a principle. That is, it is determined whether or not the difference between the estimated full charge capacities obtained for the three open circuit voltage ranges Va to Vb, Vb to Vc, and Vc to Vd is a difference that is found based on the lithium deposition phenomenon. Thus, the lithium precipitation phenomenon can be detected. More generally, in a vehicle drive system with a battery deterioration detection function, an open voltage is divided into a plurality of ranges, an estimated full charge capacity is obtained for each open voltage range, and a difference in each estimated full charge capacity is a lithium precipitation phenomenon. The lithium precipitation phenomenon can be detected by determining whether or not the difference is found based on the above.

  A specific process for detecting the lithium precipitation phenomenon will be described. FIG. 5 is a flowchart showing the processing. In the open circuit voltages Va, Vb, Vc, and Vd, when the open circuit voltage is in the range of Va to Vb, the slope of the OCV-SOC initial characteristic after lithium deposition is larger than the initial slope, and the open circuit voltage is Vb to Vc. In this range, the slope after the lithium deposition is almost equal to the initial slope, and in addition, the slope after the lithium deposition is set to be smaller than the initial slope when the open circuit voltage is in the range of Vc to Vd. To do. Moreover, it is preferable that the range of open circuit voltage Va-Vd is set in the open circuit voltage range corresponding to the range whose charge depth is 40%-80% in OCV-SOC initial characteristic.

  The open-circuit voltage of the lithium ion battery 10 varies as the motor-driven vehicle travels. The analysis unit 14 corresponds to the open-circuit voltage fluctuations within the open-circuit voltage ranges of Va to Vb, Vb to Vc, and Vc to Vd, which are determined in advance, respectively, and the estimated full charge capacities Qab, Qbc, and Qcd, respectively. Is obtained (S101). The analysis unit 14 obtains a first determination value D1 obtained by subtracting the estimated full charge capacity Qab from the estimated full charge capacity Qbc (S102), and further, a second determination value obtained by subtracting the estimated full charge capacity Qbc from the estimated full charge capacity Qcd. D2 is obtained (S103). The analysis unit 14 determines whether or not the first determination value D1 is greater than the predetermined threshold T1 and the second determination value D2 is greater than the predetermined threshold T2 (S104). When the first determination value D1 is greater than the predetermined threshold value T1 and the second determination value D2 is greater than the predetermined threshold value T2, the analysis unit 14 indicates that the lithium information phenomenon has been detected in the failure information storage unit 22. Is stored (S105). Further, the analysis unit 14 operates the warning device 24 (S106). The failure information storage unit 22 is means for storing failure information of a device mounted on a motor-driven vehicle, and the stored contents are read out during maintenance inspection of the motor-driven vehicle. The warning device 24 notifies the user that the lithium deposition phenomenon has been detected by lighting an indicator, sounding a warning sound, or the like. The analysis unit 14 returns to the execution of step S101 when the first determination value D1 is equal to or less than the predetermined threshold value T1 or when the second determination value D2 is equal to or less than the predetermined threshold value T2.

  According to such a process, the precipitation phenomenon of the lithium ion battery 10 can be detected, and the fact that the precipitation phenomenon has occurred in the lithium ion battery 10 can be notified to the user of the motor-driven vehicle, the maintenance inspector, and the like.

  Depending on the driving situation of the motor-driven vehicle, the frequency with which the open voltage takes voltages within the three open voltage ranges Va to Vb, Vb to Vc, and Vc to Vd is low, and the detection frequency of the lithium ion precipitation phenomenon is high. It may be difficult to do. FIG. 6 shows a configuration of a vehicle drive system with a battery deterioration detection function according to an application example for solving this problem. The same components as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted. In this configuration, the charging / discharging device 26 that forcibly changes the open-circuit voltage of the lithium ion battery 10 is connected in parallel to the motor driving device 18. Based on the control of the analysis unit 14, the charging / discharging device 26 forcibly forces the lithium ion battery 10 so that the open circuit voltage becomes a voltage within the three open circuit voltage ranges of Va to Vb, Vb to Vc, and Vc to Vd. Is charged and discharged. The analysis part 14 calculates | requires an estimated full charge capacity with respect to three open circuit voltage ranges, and detects a lithium precipitation phenomenon based on said process.

  In the above description, the example in which the range of the open circuit voltage is divided into three ranges based on the relationship between the slope of the characteristic after lithium deposition and the slope of the initial characteristic has been described. In addition to dividing the open-circuit voltage range into three ranges in this way, if it is possible to determine whether the difference in each estimated full charge capacity is a difference seen based on the lithium deposition phenomenon, the open-circuit voltage range is It can be divided into any number.

It is a figure which shows the structure of the vehicle drive system with a battery degradation detection function which concerns on embodiment. It is a figure which shows the OCV-charge amount characteristic of a lithium ion battery. It is a figure which shows the OCV-SOC characteristic of a lithium ion battery. It is an enlarged view of the OCV-SOC characteristic of a lithium ion battery. It is a flowchart which shows the process which detects a lithium precipitation phenomenon. It is a figure which shows the structure of the vehicle drive system with a battery degradation detection function which concerns on an application example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Lithium ion battery, 12 OCV measurement part, 14 Analysis part, 16 Ammeter, 18 Motor drive device, 20 OCV-SOC characteristic memory | storage part, 22 Fault information memory | storage part, 24 Warning device, 26 Charging / discharging apparatus.

Claims (6)

OCV measuring means for measuring the open circuit voltage of the battery;
SOC fluctuation obtaining means for obtaining a fluctuation value of the charging depth with respect to fluctuation within the open voltage range of the measured open voltage for each range of a plurality of preset open voltage ranges based on an initial characteristic of the charging depth with respect to the open voltage. ,
Current integration means for obtaining a charge / discharge current integrated value of the battery with respect to fluctuations in measured open voltage within each open voltage range;
Full charge capacity estimation means for obtaining an estimated full charge capacity for each open-circuit voltage range based on the obtained charge depth variation value and charge / discharge current integrated value;
Deterioration detecting means for detecting deterioration of the battery based on the estimated full charge capacity obtained for each open-circuit voltage range;
A battery deterioration detecting device comprising: The battery deterioration detection device according to claim 1,
The deterioration detecting means includes
A battery deterioration detection device that detects deterioration of the battery based on a difference between the obtained estimated full charge capacity for each open-circuit voltage range. The battery deterioration detection device according to claim 2,
The battery is a lithium ion battery;
The deterioration detecting means includes
A battery deterioration detection device that detects a lithium deposition phenomenon based on a comparison between a difference in an estimated full charge capacity for each open-circuit voltage range and the difference when a lithium deposition phenomenon occurs. The battery deterioration detection device according to any one of claims 1 to 3, wherein the battery deterioration detection device is mounted on a motor-driven vehicle and the battery supplies power to a drive motor.
The motor-driven vehicle is
A charge state limiter that limits a range of charge depth of the battery to a predetermined range;
The plurality of open circuit voltage ranges are:
The battery deterioration detection device, wherein the battery deterioration detection device is an open-circuit voltage range determined based on a charge depth range restricted by the charge state restriction unit. In the battery deterioration detection device according to any one of claims 1 to 4,
A battery deterioration detection apparatus comprising a charge / discharge unit that changes an open circuit voltage of the battery. Measuring the open circuit voltage of the battery;
For each range of a plurality of preset open-circuit voltage ranges, obtaining a variation value of the charge depth with respect to a variation in the open-circuit voltage range of the measured open-circuit voltage based on the initial characteristics of the charge depth with respect to the open-circuit voltage;
Obtaining a charge / discharge current integrated value of the battery with respect to fluctuations in the measured open-circuit voltage within each open-circuit voltage range;
Obtaining an estimated full charge capacity for each open-circuit voltage range based on the obtained charge depth variation value and charge / discharge current integrated value;
Detecting deterioration of the battery based on the estimated full charge capacity determined for each open voltage range;
A battery deterioration detection method comprising:

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