JP2010066229A - Device and method for detecting failure of battery - Google Patents

Abstract

A battery failure detection apparatus and a battery failure detection method capable of detecting and classifying a battery failure are provided.
A battery failure detection apparatus includes a full charge capacity detection unit 510 that detects a full charge capacity of a battery 100, an internal resistance detection unit 520 that detects an internal resistance of the battery, and a battery deterioration determination unit 530. . The battery 100 is a lithium ion battery. When the full charge capacity decreases and the internal resistance increases, the battery deterioration determination unit 530 determines that the failure of the battery 100 is due to wear deterioration, and the full charge capacity decreases and the internal resistance increases. If not, it is determined that the battery failure is due to deposition degradation.
[Selection] Figure 1

Description

  The present invention relates to a battery failure detection device and a battery failure detection method, and more particularly to a battery failure detection device and a battery failure detection method capable of classifying battery failures.

  Rechargeable and rechargeable secondary batteries have become increasingly important in recent years from small capacities for portable devices to large capacities such as electric vehicles and hybrid vehicles.

  The life of such secondary batteries is finite, and the performance deteriorates with use. Therefore, it is preferable to detect any deterioration of the secondary battery and take necessary measures such as replacement.

Japanese Patent Laid-Open No. 9-17458 (Patent Document 1) discloses a method for detecting a micro short circuit in a rechargeable lithium battery. This detection method is characterized in that it is detected that the terminal voltage at a preset time during charging with controlled current is smaller than a predetermined voltage.
Japanese Patent Laid-Open No. 9-17458 Japanese Patent Laid-Open No. 11-326471 JP 2003-59544 A JP 2000-341867 A

  Battery charge / discharge control requires information on parameters such as the full charge capacity and internal resistance of the battery. These parameters are not constant and change depending on the use conditions of the battery. As parameters, values estimated from the charge / discharge current of the battery, the voltage between terminals, and the like are used.

  It is preferable if a failure of the battery can be found by observing these parameters necessary for the control of the battery. Although the decrease in the full charge capacity is caused by the deterioration of the battery, there are some classifications of the deterioration, and the countermeasures need to be changed depending on the kind of deterioration.

  An object of the present invention is to provide a battery failure detection device and a battery failure detection method capable of detecting and classifying a battery failure.

  In summary, the present invention is a battery failure detection apparatus, which is a full charge capacity detection unit that detects a full charge capacity of a battery, an internal resistance detection unit that detects an internal resistance of the battery, a full charge capacity, and an internal resistance. And a battery deterioration determination unit that determines whether the failure of the battery is due to wear deterioration or precipitation deterioration.

Preferably, the battery is a lithium ion battery.
More preferably, the battery deterioration determination unit is configured such that when the full charge capacity detected by the full charge capacity detection unit decreases and the internal resistance detected by the internal resistance detection unit increases, the battery failure is caused by wear deterioration. If it is determined that the full charge capacity has decreased and the internal resistance has not increased, it is determined that the failure of the battery is due to deposition degradation.

  In another aspect, the present invention provides a battery failure detection method comprising: detecting a full charge capacity of a battery; detecting an internal resistance of the battery; and a battery based on the full charge capacity and the internal resistance. Determining whether the failure is due to wear deterioration or precipitation deterioration.

Preferably, the battery is a lithium ion battery.
More preferably, the step of determining determines that the failure of the battery is due to wear deterioration when the full charge capacity decreases and the internal resistance increases, the full charge capacity decreases, and the internal resistance decreases. If not increased, it is determined that the battery failure is due to deposition degradation.

  According to the present invention, it is possible to classify battery failures, so that it is possible to perform appropriate measures according to the classification.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  FIG. 1 is a diagram showing a configuration of a vehicle to which the present invention is applied. In addition, although a vehicle is illustrated, if this invention uses a battery other than a vehicle, this invention can be applied to various apparatuses.

  As shown in FIG. 1, a vehicle equipped with the battery failure detection apparatus according to the present embodiment includes a battery 100, a PCU (Power Control Unit) 200, a travel motor 300, an ECU (Electronic Control Unit) 400, and including. This vehicle is an electric vehicle that travels by the driving force of the traveling motor 300. Instead of an electric vehicle, it may be a hybrid vehicle equipped with an engine and a motor, or a fuel cell vehicle equipped with a fuel cell.

  The battery 100 is an assembled battery configured by connecting a plurality of battery modules in which a plurality of battery cells are integrated in series. The PCU 200 converts the DC power supplied from the battery 100 into AC power and supplies it to the traveling motor 300. At the time of regenerative braking of the vehicle, AC power generated by the traveling motor 300 is converted into DC power, and the battery 100 is charged by the converted DC current. The PCU 200 may include a DC / DC converter that boosts the voltage value of the power supplied from the battery 100 or steps down the voltage value of the power generated by the traveling motor 300.

  Traveling motor 300 is a three-phase AC motor. The traveling motor 300 is driven by the electric power stored in the battery 100 and causes the vehicle to travel. During regenerative braking of the vehicle, the traveling motor 300 is driven by wheels (not shown), and the traveling motor 300 operates as a generator. As a result, traveling motor 300 acts as a regenerative brake that converts braking energy into electric power. The electric power generated by the traveling motor 300 is stored in the battery 100 via the PCU 200.

  The ECU 400 executes a predetermined program using a map stored in the driving state of the vehicle, the accelerator opening, the rate of change of the accelerator opening, the shift position, the SOC of the battery 100, and a ROM (Read Only Memory). Thereby, ECU 400 controls devices mounted on the vehicle such that the vehicle is in a desired driving state. Preferably, ECU 400 includes one or more microcomputers.

  ECU 400 is connected to voltage sensor 410 that detects charge / discharge voltage VM, which is a voltage between terminals of battery 100, current sensor 412 that detects charge / discharge current IM, and battery temperature sensor 414 that detects battery temperature TM. ing. The battery temperature sensors 414 are preferably provided in a plurality (for example, three locations). The vehicle further includes an environmental temperature sensor 415 that detects the environmental temperature of the vehicle. The environmental temperature sensor 415 is also connected to the ECU 400.

  ECU 400 operating as the battery failure detection device of the present embodiment includes a full charge capacity detection unit 510 that detects the full charge capacity of battery 100, an internal resistance detection unit 520 that detects the internal resistance of the battery, and a full charge capacity. And a battery deterioration determination unit 530 for determining whether the failure of the battery is due to wear deterioration or precipitation deterioration based on the internal resistance.

  Deposition deterioration is deterioration caused by a phenomenon in which lithium ions are deposited on the negative electrode surface when charging is intermittently performed at a high rate at a low temperature in a lithium ion battery. On the other hand, the wear deterioration is deterioration accompanying normal battery use, and the cause thereof is pulverization of the active material, film formation at the electrode interface, and the like. As the wear deteriorates, the full charge capacity of the battery decreases and the internal resistance increases.

Preferably, battery 100 is a lithium ion battery.
More preferably, the battery deterioration determination unit 530 wears out the battery 100 when the full charge capacity detected by the full charge capacity detection unit 510 decreases and the internal resistance detected by the internal resistance detection unit 520 increases. When it is determined that the battery is due to deterioration and the full charge capacity is decreased and the internal resistance is not increased, it is determined that the battery failure is due to deposition deterioration.

  FIG. 2 is a flowchart for explaining processing for classifying battery failures. The processing of this flowchart is called up and executed every time a predetermined time elapses or a predetermined condition is satisfied from a predetermined main routine.

  Referring to FIG. 2, ECU 400 first detects the full charge capacity in step S1. The detection of the full charge capacity will be described later with reference to FIGS. If the full charge capacity has not decreased from the previous measurement in step S2, it is determined that the battery has not deteriorated, the process proceeds to step S7, and the control is moved to the main routine.

  If a decrease in full charge capacity is detected in step S2, the process proceeds to step S3, and ECU 400 detects the internal resistance of the battery. The detection of the internal resistance will be described later with reference to FIGS. In step S4, if the internal resistance of the battery has not increased compared to the previous measurement, the process proceeds to step S6, where it is determined that the deterioration of the battery is precipitation deterioration. On the other hand, if it is detected in step S4 that the internal resistance of the battery has increased, the process proceeds to step S5, and it is determined that the battery deterioration is wear deterioration.

  The type of deterioration determined in either step S5 or S6 is stored in a storage device inside or outside the ECU 400, read out from the storage device at a repair shop or a store, and used for repair. Alternatively, ECU 400 may notify the driver of the type of deterioration with a notification device such as a warning lamp or a screen. It should be noted that the driver may be informed of the necessity of repair by an alarm device such as a warning lamp only when it is determined that the deposition deterioration is more urgent than the wear deterioration.

  When either step S5 or S6 is completed, the process proceeds to step S7, and control is transferred to the main routine.

  Hereinafter, detection of the full charge capacity executed in step S1 will be described with reference to FIGS.

  FIG. 3 is a diagram for explaining a method of estimating an open circuit voltage (OCV) from current and voltage.

  Referring to FIGS. 1 and 3, ECU 400 uses charging / discharging voltage VM measured by voltage sensor 410 and charging / discharging current IM measured by current sensor 412 during charging / discharging of battery 100, for example, during traveling of the vehicle. The open circuit voltage OCV is estimated from the relationship between the measured values VM and IM.

  The estimation of the open circuit voltage OCV is executed every predetermined period Y. The estimation of the OCV in the period Y is performed based on a plurality of sets of measured values VM and IM acquired in the period Y and stored in the internal memory of the ECU 400.

  As an example, as shown in FIG. 3, an intercept of a □ (white square) of a linear function expression (straight line) obtained by a least square method or the like based on a plurality of sets of measurement values VM and IM is obtained as an estimated OCV. be able to. The estimated open circuit voltage OCV is used to determine the state of charge (SOC) of the battery. In such linear approximation, it is preferable to estimate the open circuit voltage OCV using three or more sets of voltage and current in order to improve the estimation accuracy.

FIG. 4 is a diagram for explaining a method of estimating the state of charge (SOC) from the open circuit voltage.
Referring to FIG. 4, charge state SOC (%) corresponding to open circuit voltage OCV (V) is held in advance in ECU 400 as a map. The same map as shown in FIG. 4 can be used for both new and deteriorated products. As the open circuit voltage OCV increases, the state of charge SOC also increases. If the estimated OCV obtained in FIG. 3 is OCV1, it is possible to obtain SOC1 that is the state of charge SOC corresponding to OCV1 by referring to the map.

Thus, each time the flowchart shown in FIG. 2 is executed, the state of charge SOC is obtained and temporarily stored in the internal memory of ECU 400. When the vehicle travels from point A to point B during travel, the state of charge SOCA stored at the time of execution at point A last time and the state of charge SOCB obtained at point B this time, as shown in the following equation (1): The difference ΔSOC is obtained.
ΔSOC = SOCB−SOCA (1)
Then, the full charge capacity Q is calculated by the following equation (2). Here, the integrated capacity SI can be detected as an integrated value (integrated value) of the charge / discharge current IM.
Q (Ah) = SI (Ah) / ΔSOC (%) × 100 (2)
Thus, every time the flowchart shown in FIG. 2 is executed, the full charge capacity Q is obtained and temporarily stored in the internal memory of the ECU 400.

FIG. 5 is a diagram for explaining a decrease in the full charge capacity.
Referring to FIG. 5, the full charge capacity is calculated to be, for example, 12 (Ah) last time, but when it is calculated to be 6 (Ah) this time, it is determined that the full charge capacity has decreased.

For example, as shown in the following equation (3), ΔQ, which is the difference between the state of charge QA stored at the previous execution and the state of charge QB obtained this time, is obtained.
ΔQ = QB−QA (3)
In step S2 of FIG. 2, if the value of ΔQ is negative, it is determined that the full charge capacity has decreased, it is determined that the battery has deteriorated, and the processes of steps S3 to S6 are executed. On the other hand, if the value of ΔQ is not negative, it is determined that the battery has not deteriorated, and the processes in steps S3 to S6 are not executed.

  Note that the determination of whether the full charge capacity has decreased may be variously modified. For example, in order to prevent erroneous detection, it may be determined that the value of ΔQ is less than a predetermined negative value (decrease significantly), it may be determined that the value has decreased in step S2, or the value of ΔQ is less than a predetermined negative or negative value. May be determined to have decreased in step S2 when this is continuously detected a plurality of times.

  Subsequently, detection of the internal resistance detected in step S3 of FIG. 2 will be described with reference to FIGS.

FIG. 6 is a waveform diagram showing an applied current waveform at the time of measuring internal resistance.
FIG. 7 is a waveform diagram showing an observed voltage waveform during internal resistance measurement.

When the current of FIG. 6 is applied to the battery cell, a voltage waveform as shown in FIG. 7 is observed. The open circuit voltage OCV when the application of this current was started was 3.7 V (new, SOC = 60% at 25 ° C.). In FIG. 6, a constant current of 100 A is applied to the battery for 10 seconds. Then, as shown in FIG. 7, the voltage initially increases from around 3.7 V to about 3.9 V, and then gradually increases until it exceeds 4.0 V in 10 seconds. When the pulse current is expressed as ΔI, the increase in voltage observed 1 second after the start of current application is expressed as ΔV1, and the increase in voltage observed 10 seconds after the start of current application is expressed as ΔV10, the following equations (4) and (5 ), Two internal resistances INR1 (after 1 second) and INR10 (after 10 seconds) are obtained.
INR1 = ΔV1 / ΔI (4)
INR10 = ΔV10 / ΔI (5)
INR1 mainly represents a pure resistance (DC resistance), and INR10 mainly represents a resistance obtained by adding a diffusion resistance (diffusion of lithium ions in the electrolytic solution) to the pure resistance.

  FIG. 8 is a diagram showing a change (10 ° C.) in the internal resistance of the battery when a new product and precipitation deterioration occur.

  FIG. 9 is a diagram showing a change (25 ° C.) in the internal resistance of the battery when a new product and precipitation deterioration occur.

  FIG. 10 is a diagram showing a change in the internal resistance (40 ° C.) of the battery when a new product and precipitation deterioration occur.

  8 to 10, a circle (white circle) indicates the internal resistance INR1 of the new battery, and a circle (solid circle) indicates the internal resistance INR10 of the new battery. Further, Δ (open triangle) indicates the internal resistance INR1 of the battery after 4000 cycles of charging / discharging, and ▲ (solid-colored) indicates the internal resistance INR10 of the battery after 4000 cycles of charging / discharging.

  As can be seen from FIG. 8 to FIG. 10, when precipitation deterioration occurs, there is not much difference in internal resistance between the new article and after 4000 cycles of charge / discharge (after precipitation deterioration). Although not shown, when wear deterioration occurs, the internal resistance is greatly increased compared to a new product. Therefore, it is possible to distinguish the precipitation deterioration from the wear deterioration by the change of the internal resistance.

  As the internal resistance, any one of INR1 and INR10 in the above formulas (4) and (5) may be used. Further, in the region where the state of charge SOC does not change relatively, the current and voltage may be plotted, and the internal resistance may be obtained from the slope obtained by linear approximation by the least square method.

  The internal resistance is calculated every time S3 in the flowchart of FIG. 2 is executed, and is stored in a memory (not shown) of the ECU 400. In step S4, it is determined whether or not the internal resistance calculated this time has increased compared to the previously calculated internal resistance stored in the memory.

FIG. 11 is a diagram for explaining an increase in internal resistance.
As shown in FIG. 11, in step S4, for example, when the internal resistance of the battery cell has increased from 1 mΩ to 1.4 mΩ, the process proceeds to step S5, and the deterioration is determined to be wear deterioration. . If the internal resistance of the battery cell has not increased, the process proceeds to step S6, and the deterioration is determined to be precipitation deterioration.

  As described above, in this embodiment, the full charge capacity and internal resistance of the battery due to deterioration are measured, and when the full charge capacity decreases and the internal resistance increases, it is determined that the wear is deteriorated. On the other hand, when the full charge capacity is reduced, but the internal resistance is not substantially changed, it is determined as deposition deterioration. As a result, the type of deterioration can be determined, and appropriate processing according to the type of deterioration can be quickly performed.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a figure which shows the structure of the vehicle to which this invention is applied. It is a flowchart for demonstrating the process which classifies the failure of a battery. It is a figure for demonstrating the method of estimating an open circuit voltage (OCV) from an electric current and a voltage. It is a figure for demonstrating the method of estimating a charge condition (SOC) from an open circuit voltage. It is a figure for demonstrating the reduction | decrease in a full charge capacity. It is a wave form diagram which showed an applied current waveform at the time of internal resistance measurement. It is a wave form diagram which showed an observation voltage waveform at the time of internal resistance measurement. It is the figure which showed the change (10 degreeC) of the internal resistance of the battery at the time of new article and precipitation degradation. It is the figure which showed the change (25 degreeC) of the internal resistance of the battery at the time of new article and precipitation degradation. It is the figure which showed the change (40 degreeC) of the internal resistance of the battery at the time of new article and precipitation degradation. It is a figure for demonstrating the increase in internal resistance.

Explanation of symbols

  100 battery, 300 travel motor, 410 voltage sensor, 412 current sensor, 414 battery temperature sensor, 415 environmental temperature sensor, 510 full charge capacity detection unit, 520 internal resistance detection unit, 530 battery deterioration determination unit.

Claims (6)

A battery failure detection device,
A full charge capacity detector for detecting a full charge capacity of the battery;
An internal resistance detector for detecting the internal resistance of the battery;
A battery failure detection device comprising: a battery deterioration determination unit that determines whether the battery failure is due to wear deterioration or precipitation deterioration based on the full charge capacity and the internal resistance.   The battery failure detection device according to claim 1, wherein the battery is a lithium ion battery.   The battery deterioration determination unit is configured such that when the full charge capacity detected by the full charge capacity detection unit decreases and the internal resistance detected by the internal resistance detection unit increases, a failure of the battery is caused by the wear deterioration. 3. If the full charge capacity decreases and the internal resistance does not increase, it is determined that the battery failure is due to the deposition deterioration. The failure detection apparatus of the battery as described in 2. A battery failure detection method comprising:
Detecting the full charge capacity of the battery;
Detecting an internal resistance of the battery;
Determining whether the failure of the battery is due to wear deterioration or precipitation deterioration based on the full charge capacity and the internal resistance.   The battery failure detection method according to claim 4, wherein the battery is a lithium ion battery.   The step of determining determines that the failure of the battery is due to the wear deterioration when the full charge capacity decreases and the internal resistance increases, the full charge capacity decreases, and the The battery failure detection method according to claim 4 or 5, wherein when the internal resistance is not increased, it is determined that the failure of the battery is caused by the deposition deterioration.

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