JP2014120335A - Battery system, battery monitoring device, and battery monitoring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect rise of pressure not accompanied by rise of temperature.SOLUTION: A battery system comprises: a lithium ion battery 2; and a battery monitoring device 10 for monitoring the lithium ion battery 2. The battery monitoring device 10 comprises: a state amount acquisition unit 11 for acquiring a state amount showing an expansion state of the lithium ion battery 2; a change amount calculation unit 12 for calculating temporal change of the state amount acquired by the state amount acquisition unit 11; and a monitoring unit 13 which monitors the temporal change calculated by the change amount calculation unit 12, and compares the monitored temporal change with a temporal change reference value that is obtained in advance and shows deterioration.

Description

  The present invention relates to a battery system, a battery monitoring device, and a battery monitoring method.

  Lithium-ion batteries have high energy density, are compact and lightweight, and therefore are expected to be used in power storage systems such as output fluctuation mitigation for natural energy power generation systems and backup power sources.

  A lithium ion battery deteriorates by repeated charge and discharge. In addition, when a short circuit occurs inside the lithium ion battery, a large current flows to generate heat and the internal temperature suddenly rises, so-called thermal runaway may occur. Lithium-ion batteries measure and monitor the voltage between the electrode terminals, internal resistance, can temperature, etc. in order to prevent the thermal runaway by detecting the deterioration state and the phenomenon leading to the thermal runaway. It has been broken. In addition, when a lithium ion battery is charged and discharged, the battery case itself expands due to expansion of the internal laminate depending on the state of charge. Further, in the lithium ion battery, when the internal temperature that causes thermal runaway increases, the internal pressure increases due to evaporation of the electrolyte, and in this case, the battery case expands.

  FIG. 9 shows an example of a battery system including the pressure release valve 101. This battery system includes a plurality of lithium ion batteries 102. Each of the lithium ion batteries 102 has a battery case 103. The battery case 103 has an insulator 104 attached between them. The battery case 103 has electrode terminals 105 on the upper surface. The pressure release valve 101 is disposed on the upper surface of the battery case 103. The pressure release valve 101 is opened when the internal pressure of the battery case 103 exceeds a predetermined value. However, this battery system detects an abnormality only when the pressure release valve 101 is opened. Therefore, this battery system is accompanied by a rapid pressure change when the pressure release by the pressure release valve 101 occurs. Thereby, in this battery system, an impact force as a reaction force at the time of pressure release may act on the battery rack, or the electrolyte may leak from the pressure release valve 101. Therefore, in such a battery system, it is necessary to detect an abnormality before releasing the pressure.

  Various techniques relating to such a background are known (see, for example, Patent Documents 1 and 2).

  For example, Patent Document 1 describes a method for detecting expansion of an electrochemical element. More specifically, the method for detecting expansion of an electrochemical element includes a fixing surface on which an electrochemical element is fixed when the electrochemical element having an element body and an enclosure that encloses the element body expands. And the circuit part formed in at least one of the fixed surface side surfaces of the electrochemical element is disconnected, and the expansion of the electrochemical element is detected. Thus, depending on the method for detecting expansion of the electrochemical element, the expansion of the electrochemical element can be detected with a simple configuration.

  For example, Patent Document 2 describes a battery system configured by combining a plurality of single cells. More specifically, this battery system has a substantially box-shaped battery housing case, a laminated body formed by laminating a plurality of electrode plates, and a cell case for housing the laminated body. At least one of the first side surfaces facing the stacking direction of the stacked body and at least one of the second side surfaces facing the direction orthogonal to the stacking direction are made to face the battery housing case wall surface or the battery housing case partition plate. In this manner, each cell is housed in a battery housing case. The battery system includes a first side surface, a battery housing case wall surface facing the first side surface, a first separation distance from the battery housing case partition plate, a second side surface, and a second side surface. The second separation distance from the battery housing case wall surface facing the battery or the battery housing case partition plate is detected. Then, this battery system determines that the corresponding cell is abnormal in internal pressure when both the first separation distance and the second separation distance are reduced based on the detection result. Thus, depending on the battery system, the internal pressure abnormality can be accurately detected for each single battery by the expansion of the cell case.

JP 2008-251437 A International Publication No. 2011/115091

  Although the techniques described in Patent Document 1 and Patent Document 2 both detect the expansion of the battery case, they cannot detect a pressure increase without a temperature increase.

  In order to solve the above problems, according to a first embodiment of the present invention, a battery system includes a lithium ion battery and a battery monitoring device that monitors the lithium ion battery, and the battery monitoring device is a lithium ion battery. A state quantity acquisition unit that acquires a state quantity representing an expansion state of the state, a change amount calculation part that obtains a time change of the state quantity obtained by the state quantity acquisition part, and a time change obtained by the change amount calculation part, And a monitoring unit for comparing with a time change reference value indicating deterioration obtained in advance.

  The monitoring unit may further obtain the life from the state quantity based on the reference data indicating the relationship between the state quantity and the life obtained in advance.

  According to a second aspect of the present invention, a battery system includes a lithium ion battery and a battery monitoring device that monitors the lithium ion battery, and the battery monitoring device has a state quantity that represents an expanded state of the lithium ion battery. A state quantity acquisition unit to be acquired, and a monitoring unit that obtains the life from the state quantity based on the reference data indicating the relationship between the state quantity obtained in advance and the life.

  According to a third aspect of the present invention, there is provided a battery monitoring device, a state quantity acquisition unit that acquires a state quantity indicating an expansion state of a lithium ion battery, a change amount calculation part that obtains a time change of the state quantity, and a time And a monitoring unit that monitors the change and compares the change with a time change reference value indicating deterioration obtained in advance.

  According to a fourth aspect of the present invention, there is provided a battery monitoring method, a state quantity obtaining step for obtaining a state quantity representing an expansion state of a lithium ion battery, a time change obtaining step for obtaining a time change of the state quantity, and a time A comparison step of monitoring a change and comparing it with a time change reference value indicating deterioration obtained in advance, and detecting an abnormality when the time change exceeds the time change reference value.

  The above summary of the invention does not enumerate all necessary features of the present invention. Also, a sub-combination of these feature groups can also be an invention.

  As is apparent from the above description, according to the present invention, it is possible to detect an increase in pressure that does not accompany an increase in temperature.

It is a conceptual block diagram of the battery system of a 1st embodiment. It is a block block diagram including sectional drawing of the lithium ion battery in the battery system of 1st Embodiment. It is a time chart at the time of performing abnormality determination of the battery system of 1st Embodiment. It is a time chart explaining the method of calculating | requiring the average change rate at the time of performing abnormality determination of the battery system of 1st Embodiment. It is a flowchart explaining control operation of the battery system of the first embodiment. It is sectional drawing of the lithium ion battery in the battery system of 2nd Embodiment. (A) is a time chart of the internal pressure rise curve from the start of use applied to the battery system of the second embodiment to the end of its life, and (b) is a time chart of the sensor output average value. It is a flowchart explaining the control action of the battery system of 2nd Embodiment. It is a figure which shows an example of the battery system provided with the pressure release valve.

  Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the claimed invention, and all combinations of features described in the embodiments are described below. However, this is not always essential for the solution of the invention.

  FIG. 1 is a conceptual block diagram of the battery system of the first embodiment. As shown in FIG. 1, the battery system 1 includes an assembled battery 3 and a battery monitoring device 10 that monitors and controls the assembled battery 3. The assembled battery 3 includes a lithium ion battery 2 that is a plurality of unit cells. The assembled battery 3 is connected to the power load 4 and can be charged and discharged. An example of the electric power load 4 is an electric vehicle. The power load 4 is a power converter such as an electric motor or an inverter connected to a wheel (not shown), and controls the operation of the power converter such as an inverter and the rotation speed of the electric motor. The electric power load 4 may be an electric motor that drives a wiper or the like. In addition to the electric vehicle, the electric power load 4 may be, for example, an industrial vehicle such as a forklift, a train, or a mobile body such as an airplane or a ship in which a propeller or a screw is connected to an electric motor. Furthermore, the power load 4 may be a stationary system such as a home power storage system or a grid-connected smoothing power storage system combined with a natural energy power generation such as a windmill or sunlight. In other words, the power load 4 relates to the entire system that uses charge / discharge of power by the lithium ion battery 2.

  The battery monitoring device 10 includes a state quantity acquisition unit 11 that acquires a state quantity indicating the expanded state of the lithium ion battery 2. The battery monitoring device 10 includes a change amount calculation unit 12 that obtains a time change of the state amount. And the battery monitoring apparatus 10 is equipped with the monitoring part 13 which monitors a time change and compares with the time change reference value which shows the deterioration obtained beforehand.

  FIG. 2 is a block configuration diagram including a cross-sectional view of the lithium ion battery 2 in the battery system 1. As shown in FIG. 2, the lithium ion battery 2 is housed in a battery housing case 14. The battery housing case 14 is formed in a bottomed box shape with, for example, a resin material having insulating properties. The battery housing case 14 includes an upper opening 15, an upper lid 16, a bottom plate 17, and a side plate 18. For example, four lithium ion batteries 2 are accommodated in the battery housing case 14 in parallel.

  The lithium ion battery 2 has a positive electrode terminal 20 and a negative electrode terminal 21 on the upper surface of the battery case 19. In the lithium ion battery 2, the electrode terminals 20 and 21 are electrically connected in series by a bus bar 22. The bus bar 22 is made of a conductive metal material.

  A battery case 19 of a pair of lithium ion batteries 2 adjacent to each other has a first insulator 23 and a second insulator 24 attached independently between each other. The insulators 23 and 24 are formed of an insulating material and are in contact with the side portion of the battery case 19. The insulators 23 and 24 have a function of preventing electrical contact with each other when, for example, vibrations occur between the lithium ion batteries 2 due to vehicle vibration or the like.

  In the battery system 1, a pressure sensor 25 is attached between the insulators 23 and 24. The pressure sensor 25 has sensing units (not shown) on both sides, and these sensing units are in contact with the insulators 23 and 24. Therefore, the pressure sensor 25 detects the deformation of the expanded state that occurs in the battery case 19 of the lithium ion battery 2 via the insulators 23 and 24, and outputs the detected output signal. Note that a plurality of pressure sensors 25 may be disposed between the insulators 23 and 24 instead of being disposed between the insulators 23 and 24. In that case, the pressure sensor 25 can sense deformation at a plurality of locations of the battery case 19.

  The battery monitoring device 10 has a built-in CPU or the like equipped with a memory having a predetermined capacity. The state quantity acquisition unit 11 is connected to the pressure sensor 25. Therefore, the state quantity acquisition unit 11 acquires the output signal obtained from the pressure sensor 25 as state quantity data S representing the expanded state of the lithium ion battery 2.

  The change amount calculation unit 12 includes a calculation circuit (not shown). The change amount calculator 12 calculates the state amount data S and calculates the time change data T of the state amount data S.

Monitoring unit 13 stores a threshold value a _c as a time variation reference value obtained based on experimental data such as burst test. Monitoring unit 13, the average rate of change A (see FIG. 4) calculated on the basis of the time change data T is compared with a threshold value a _c. Then, the battery monitoring device 10 monitors the temporal change of the output signal of the pressure sensor 25, an abnormality determination by comparing the average rate A and the threshold a _c within a certain time. The battery monitoring device 10 is connected to the stopping device 26. The stop device 26 stops the charging operation when the abnormality determination is performed.

FIG. 3 is a time chart for explaining a specific operation of the abnormality determination of the battery monitoring device 10 in the battery system 1. As shown in FIG. 3, the monitoring unit 13 sets the following two determination conditions between time t ₀ and time t ₁ . The first judgment condition by monitoring unit 13 compares the absolute value of the output signal obtained from the pressure sensor 25, and a threshold value a _c, the absolute value of the output signal of the pressure sensor 25 has exceeded the threshold value a _c In this case, an abnormality is determined. The second determination condition by the monitoring unit 13 compares the average change rate A and the threshold a _c of the pressure sensor 25, the determination of abnormality when the average change rate A of the pressure sensor 25 has exceeded the threshold value a _c Is to do. At the time t _1, exceeds the threshold value a _c is the absolute value of the output signal of the pressure sensor 25, and the average change rate A of the pressure sensor 25 exceeds the threshold value a _c. Thereby, the battery monitoring apparatus 10 performs abnormality determination. Then, the stop device 26 operates. That is, the battery monitoring device 10 does not determine abnormality based only on the absolute value of the output signal of the pressure sensor 25 and does not perform abnormality determination based only on the average change rate A of the pressure sensor 25. Here, when the average change rate A of the pressure sensor 25 does not exceed the threshold value a _c, when only the absolute value of the output signal of the pressure sensor 25 has exceeded the threshold value a _c, the battery monitoring device 10, abnormal determination To do. Thereby, the battery monitoring device 10 can operate the stop device 26 when the memory fails and the determination based on the average change rate A becomes difficult.

FIG. 4 is a time chart for explaining a method for obtaining the average rate of change A when the abnormality determination of the battery monitoring device 10 in the battery system 1 is performed. As shown in FIG. 4, there are the following two methods for obtaining the average rate of change A when performing abnormality determination. The first method is to obtain the average rate of change A from the rate of change obtained at every sampling interval by storing data for a certain period of time in the memory starting from the latest data acquisition time. The second method is to directly calculate the average change rate A for the data holding period from the latest and oldest state quantity data S. Here, the output signals of the pressure sensor 25 are y ₁ , y ₂ , y _{3 to} y _N-2 , y _N−1 , y _N , and the battery monitoring device 10 a The latest change rate a _i of ₁ , a ₂ , a ₃ , a _N−2 , a _N−1 is stored. At this time, the change rate a _i can be obtained by the following equation. Note that i = 1, 2 to N-1.

  The average change rate A can be obtained by the following equation.

The battery system 1 improves the accuracy of abnormality determination by setting a conditional expression at the time of abnormality determination according to the following uses (for stationary use and for mobile objects).
(For stationary use)
When both the following conditional expressions (1) and (2) are satisfied, it is determined that there is an abnormality.
(1) Average rate of change A> threshold a _c
(2) Latest rate of change a ₁ > 0
In addition, since the internal pressure fluctuation at the time of occurrence of an abnormality such as an internal short circuit always shows an upward trend, when the latest change rate is negative, it can be determined that the internal pressure tends to decrease and the possibility of the occurrence of the abnormality is low.
(For mobile objects)
When the following conditional expressions (1) to (3) are all satisfied, it is determined as abnormal.
(1) Average rate of change A> threshold a _c
(2) Latest rate of change a ₁ > 0
(3) The conditions of (1) and (2) should be satisfied N times (N ≧ 2) continuously.
In the case of a moving object, the sensor output signal may temporarily increase due to a sudden load increase or a disturbance such as an impact. Therefore, the sampling timing may coincide with these events. The sensor output signal, it is assumed to detect temporary erroneous exceeds the threshold a _c. Therefore, in order to prevent such erroneous detection, the condition (3) is added for the moving object. Here, when the average change rate A of the pressure sensor 25 does not exceed the threshold value a _c, determining if the absolute value of the output signal of the pressure sensor 25 has exceeded the threshold value a _c, the battery monitoring device 10, abnormal To do. Considering that the time from the occurrence of abnormality until the battery case 19 is damaged is about 1 to 2 (Hr) at the shortest, in order to accurately grasp the tendency of the increase in internal pressure when the abnormality occurs, the sampling period is It is preferable to set it to 5 to 10 minutes or less.

FIG. 5 is a flowchart for explaining a basic control operation of the battery system 1. As shown in FIG. 5, when the control is started, the state quantity acquisition unit 11 acquires the output signal obtained from the pressure sensor 25 as the state quantity data S representing the expanded state of the lithium ion battery 2 (step S101). . Next, the change amount calculation unit 12 calculates the state amount data S and calculates the time change data T of the state amount data S (step S102). Subsequently, the absolute value of the output signal of the pressure sensor 25 exceeds the threshold value a _c, and, whether or not the average change rate A of the pressure sensor 25 has exceeded the threshold value a _c monitoring unit 13 determines (step S103). If the monitoring unit 13 determines that the two determination conditions are satisfied in the determination in step S103, an abnormality determination is performed (step S104). At this time, if it is determined in step S103 that the two determination conditions are not satisfied, the process returns to step S101 to acquire the state quantity data S again without performing abnormality determination.

As described above, according to the battery system 1 of the first embodiment, exceeds the threshold value a _c is the absolute value of the output signal of the pressure sensor 25, and the threshold is the average change rate A of the pressure sensor 25 a _c An abnormality is judged when the value exceeds. Therefore, according to the battery system 1, it is possible to estimate and detect a change in internal pressure that is not accompanied by heat generation.

  Further, according to the battery system 1, the internal pressure can be estimated and detected from the correlation between the internal pressure and the output signal of the pressure sensor 25 without directly measuring the internal pressure of the lithium ion battery 2.

  And according to the battery system 1, early abnormality determination can be performed by indirectly monitoring the time-series change of the internal pressure of the lithium ion battery 2.

  Furthermore, according to the battery system 1, the stop device 26 can be operated even when the memory fails and the determination based on the average change rate A becomes difficult.

According to the battery monitoring device 10 of the first embodiment, in the battery system 1, it exceeds the threshold value a _c is the absolute value of the output signal of the pressure sensor 25, and the average change rate A of the pressure sensor 25 is a threshold value a _c When it exceeds, an abnormality is judged. Therefore, according to the battery monitoring device 10, it is possible to estimate and detect a change in internal pressure that is not accompanied by heat generation.

According to the battery monitoring method of the first embodiment, exceeds the threshold value a _c is the absolute value of the output signal of the pressure sensor 25, and the abnormality determination when the average change rate A of the pressure sensor 25 has exceeded the threshold value a _c I do. Therefore, according to the battery monitoring method, it is possible to estimate and detect a change in internal pressure without heat generation.

  Next, the second embodiment will be described with reference to FIGS. 6 to 7, but the same parts as those in the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted, and only differences will be described. explain. FIG. 6 is a cross-sectional view of the lithium ion battery 2 in the battery system of the second embodiment. As shown in FIG. 6, in this battery system, a single-structure insulator 31 is attached between the battery cases 19. And the pressure sensor 25 is accommodated in the insulator 31 of a single structure. The pressure sensor 25 detects deformation via the insulator 31. Here, the deformation is an expanded state generated in the battery case 19 of each lithium ion battery 2. The pressure sensor 25 outputs the detected output signal. This battery system has a battery monitoring device 32. The battery monitoring device 32 acquires and stores internal pressure increase curve data from the start of use of the lithium ion battery 2 until the end of its life in advance through a performance test or the like.

FIG. 7A is a time chart of the internal pressure increase curve from the start of use to the end of the life applied to the battery system of the second embodiment, and FIG. 7B is a time chart of the sensor output average value. is there. As shown to Fig.7 (a), the battery monitoring apparatus 32 has acquired the internal pressure raise curve from the use start to the time of a lifetime end in advance. Then, as shown in FIG. 7 (b), the battery monitoring device 32 calculates the time variation of the sensor output signal average value Y shown in the left diagram of FIG. 7 and the internal pressure increase curve shown in FIG. 7 (a). Compare sequentially. At this time, output signals of the pressure sensor 25 are y ₁ , y ₂ , y _{3 to} y _N−2 , y _N−1 , and y _N. The battery monitoring device 32 calculates the signal average value Y at life end of the lithium ion battery 2 from a certain time point t _p. Then, the battery monitoring device 32 calculates the time t _e the estimated remaining lifetime from the calculated signal mean value Y. Incidentally, it is estimated remaining life ₌ t e -t _p at time t = t. Here, the signal average value Y can be obtained by the following equation.

  FIG. 8 is a flowchart for explaining the control operation of the battery system according to the second embodiment. As shown in FIG. 8, first, the time change of the signal average value Y of the pressure sensor 25 is monitored (step S201). Next, the average value of the output signal of the pressure sensor 25 at a certain time is calculated (step S202). Then, the remaining life is calculated with reference to the internal pressure increase curve from the start of use until the end of the life (step S203).

  According to the battery system of the second embodiment, the time variation of the signal average value Y of the pressure sensor 25 is monitored, and the signal average value Y is compared with the internal pressure increase curve data. Thereby, according to this battery system, the remaining life of the lithium ion battery 2 can be estimated with high accuracy. Moreover, according to this battery system, since the monitoring unit 13 obtains the life from the state quantity based on the reference data indicating the relationship between the state quantity and the life obtained in advance, an accurate life can be obtained.

  The battery system, the battery monitoring device, and the battery monitoring method of the present invention are not limited to the above-described embodiments, and appropriate modifications and improvements can be made.

DESCRIPTION OF SYMBOLS 1 Battery system 2 Lithium ion battery 5 Battery system 10 Battery monitoring apparatus 11 State quantity acquisition part 12 Change amount calculating part 13 Monitoring part 32 Battery monitoring apparatus

Claims (5)

A lithium-ion battery;
A battery monitoring device for monitoring the lithium ion battery,
The battery monitoring device includes:
A state quantity obtaining unit for obtaining a state quantity representing an expanded state of the lithium ion battery;
A change amount calculation unit for obtaining a time change of the state amount acquired by the state amount acquisition unit;
A battery system comprising: a monitoring unit that monitors a time change obtained by the change amount calculation unit and compares the time change with a time change reference value indicating deterioration obtained in advance. The battery system according to claim 1, wherein the monitoring unit further obtains the life from the state quantity based on reference data indicating a relationship between the state quantity and the life obtained in advance. A lithium-ion battery;
A battery monitoring device for monitoring the lithium ion battery,
The battery monitoring device includes:
A state quantity obtaining unit for obtaining a state quantity representing an expanded state of the lithium ion battery;
A battery system comprising: a monitoring unit that obtains a life from the state quantity based on reference data indicating a relationship between the state quantity and the life obtained in advance. A state quantity obtaining unit for obtaining a state quantity representing an expanded state of the lithium ion battery;
A change amount calculation unit for obtaining a time change of the state quantity;
A battery monitoring device comprising: a monitoring unit that monitors the time change and compares the time change with a time change reference value indicating deterioration obtained in advance. A state quantity acquisition step of acquiring a state quantity representing an expanded state of the lithium ion battery;
A time change obtaining step for obtaining a time change of the state quantity;
A comparison step of monitoring the time change and comparing it with a time change reference value indicating degradation obtained in advance.
An abnormality is detected when the time change exceeds the time change reference value.

Images