Battery thermorunaway cause estimation system, and battery thermorunaway cause estimation method

Abstract

To provide a battery thermorunaway cause estimation system and battery thermorunaway cause estimation method that can speed up identifying a cause of thermorunaway occurence.SOLUTION: A battery thermorunaway cause estimation system 1 has: a thermorunaway analysis unit 13 that implements a thermorunaway analysis, letting at least two parameters of a current, voltage, temperature, amount of charge, and deterioration as an analysis condition; an analysis result storage unit 14 that stores the analysis condition and an analysis result; a sensor 10 that is attached to a battery system 2 composed of a plurality of chargeable / dischargeable secondary batteries; a state estimation unit 11 that estimates an amount of state of the battery system 2 from a physical quantity the sensor 10 measures; a state storage unit 12 that stores the physical quantity and / or the amount of state; a calculation unit 30, when comparing homogeneous parameters the analysis result storage unit and the state storage unit 12 store respectively, and similarity exceeds a prescribed value, estimates the analysis condition as a battery thermorunaway cause; and a display unit 22 that displays the battery thermorunaway cause.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a system and a method for estimating the cause of battery thermal runaway. [Background technology]

[0002] Since the output of solar and wind power generation fluctuates depending on the weather and time of day, it is hoped that energy storage systems can be used to adjust supply and demand in the power grid. The energy storage system is composed of, for example, a large number of batteries. For example, lithium ion batteries are used as batteries for such applications. A phenomenon called thermal runaway is known for lithium ion batteries, in which a specific part inside the battery heats up for some reason, which leads to the next reaction and further heat generation. When a lithium ion battery goes into thermal runaway, adjacent batteries may go into thermal runaway in a chain reaction, which may develop into a fire. When such a fire occurs, it takes a lot of time and money to recover, and it is not uncommon for operation to not be resumed until the cause of the fire can be identified. For this reason, it is desirable to quickly identify the cause of the battery's thermal runaway. In addition, lithium ion batteries are not limited to industrial and home energy storage systems connected to power grids, but are also used in applications such as electric vehicles, cordless vacuum cleaners, power tools, and mobile terminals, and in these applications as well, it is desirable to quickly identify the cause when a battery goes into thermal runaway.

[0003] Known technologies related to battery thermal runaway include those described in Patent Document 1 and Patent Document 2. Patent Document 1 discloses a technology that identifies and reports a thermal runaway level by comparing the expansion force, battery voltage, and battery temperature of a battery with respective threshold values. Patent Document 2 discloses a technology that compares the battery voltage and ambient temperature with respective threshold values, and determines and reports thermal runaway from the duration of the results. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-108252 [Patent Document 2] Patent Publication No. 2021-144875 Summary of the Invention [Problem to be solved by the invention]

[0005] The technologies disclosed in Patent Documents 1 and 2 both aim to prevent thermal runaway from occurring by detecting and reporting the occurrence of precursor phenomena of thermal runaway, but it is difficult to say that they can be used to identify the cause of thermal runaway after it actually occurs. Currently, when a fire accident occurs, a hypothesis of the cause is made based on an on-site investigation, and a third party interviews the relevant parties and conducts a reproduction experiment. The cause of thermal runaway may be a manufacturing defect in the battery itself, an abnormality in peripheral devices, or multiple factors occurring simultaneously, and it may take more than a year to identify the cause.

[0006] Therefore, the present invention provides a system and method for estimating the cause of thermal runaway in a battery, which enable quick identification of the cause of the occurrence of thermal runaway. [Means for solving the problem]

[0007] In order to solve the above problems, the battery thermal runaway cause estimation system of the present invention is characterized in having a thermal runaway analysis unit that performs thermal runaway analysis using at least two parameters from among current, voltage, temperature, charge amount, and deterioration level as analysis conditions, an analysis result memory unit that stores the analysis conditions and analysis results, a sensor attached to a battery system composed of a plurality of rechargeable secondary batteries, a state estimation unit that estimates a state quantity of the battery system from a physical quantity measured by the sensor, a state memory unit that stores the physical quantity and / or the state quantity, a calculation unit that compares parameters of the same type stored in the analysis result memory unit and the state memory unit, and if the similarity exceeds a predetermined value, estimates that the analysis conditions are the cause of battery thermal runaway, and a display unit that displays the cause of the battery thermal runaway.

[0008] Furthermore, the method for estimating the cause of battery thermal runaway according to the present invention is characterized by comprising the steps of: a thermal runaway analysis unit performing an analysis of thermal runaway using at least two parameters selected from among current, voltage, temperature, charge amount, and deterioration level as analysis conditions; an analysis result storage unit storing the analysis conditions and analysis results; a calculation unit comparing measured values ​​of at least two parameters selected from among current, voltage, temperature, charge amount, and deterioration level with the analysis conditions, and estimating that the analysis conditions are the cause of the battery thermal runaway if the similarity exceeds a predetermined value; and a display unit displaying the cause of the battery thermal runaway. Effect of the Invention

[0009] According to the present invention, it is possible to provide a system and a method for estimating the cause of thermal runaway in a battery, which enable quick identification of the cause of the occurrence of thermal runaway. Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram showing an overall schematic configuration of a battery thermal runaway cause estimation system according to a first embodiment of the present invention. [Diagram 2] 2 is a block diagram showing a configuration example of the battery system of FIG. 1. [Diagram 3] FIG. 2 is a block diagram showing a hardware configuration of a calculation unit in FIG. [Figure 4] 4 is a flowchart illustrating the operation of the battery thermal runaway cause estimating system according to the first embodiment. [Diagram 5] FIG. 2 is an explanatory diagram of a method for analyzing thermal runaway in the battery thermal runaway cause estimating system according to the first embodiment. [Figure 6] 4 shows an example of analysis conditions and analysis results in the battery thermal runaway cause estimation system according to the first embodiment. [Figure 7] 2 is an example of a parameter input screen shown on the display unit of FIG. 1. [Figure 8] 2 is an example of fault causal relationship information stored in a fault causal relationship storage unit in FIG. 1. [Figure 9] 2 is an example of a cause estimation result shown on the display unit of FIG. 1. [Figure 10] FIG. 11 is a block diagram showing an overall schematic configuration of a battery thermal runaway cause estimation system according to a second embodiment of the present invention. [Figure 11] FIG. 11 is a block diagram showing an overall schematic configuration of a battery thermal runaway cause estimation system according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] A battery thermal runaway cause estimating system and a battery thermal runaway cause estimating method according to an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings used in this specification, the same or corresponding components are designated by the same reference numerals, and repeated description may be omitted. EXAMPLES

[0012] <Configuration> Fig. 1 is a block diagram showing an overall schematic configuration of a battery thermal runaway cause estimating system according to embodiment 1 of the invention. As shown in Fig. 1, the battery thermal runaway cause estimating system 1 according to this embodiment includes a sensor 10 connected to a battery system 2, a state estimation unit 11, a state storage unit 12, a thermal runaway analysis unit 13, an analysis result storage unit 14, a calculation unit 30, an operation unit 21, a display unit 22, and a failure causal relationship storage unit 41.

[0013] The battery system 2 is configured by connecting a plurality of cells 23, which are the minimum unit of a battery and are not shown in FIG. 1, in series and / or parallel. FIG. 2 is an explanatory diagram showing a configuration example of the battery system of FIG. 1. Representative examples of the battery system 2 include a module 24 configured by connecting a plurality of cells 23 in series as shown in the upper left diagram of FIG. 2, a rack 25 configured by connecting a plurality of modules 24 in series as shown in the upper right diagram of FIG. 2, and a container 26 configured by connecting a plurality of racks 25 in parallel as shown in the lower diagram of FIG. 2. In addition, the battery system 2 may be called a pack, a unit, a string, a bank, a board, etc. The battery system 2 also includes wiring, bolts, a control device, a communication device, a switch, a circuit breaker, an emergency stop device, an initial charging resistor, a cooling device, an air conditioning device, lighting, a fire alarm, a fire extinguisher, etc., which are not shown in FIG. 2. A lithium ion battery is used for the cell 23. However, the cell 23 is not limited to a lithium ion battery, and any secondary battery may be used.

[0014] The sensor 10 shown in FIG. 1 measures various physical quantities of the battery system 2. Examples of the sensor 10 are a voltage sensor, a current sensor, a temperature sensor, a smoke sensor, a gas sensor, and a camera. The state estimation unit 11 is also called a BMS (Battery Management System), and estimates the state of the battery system 2 from the physical quantities measured by the sensor 10. For example, the state estimation unit 11 estimates the state of charge (SOC), the deterioration rate (SOH), and the charge / discharge allowable power (SOP) of the battery system 2 from physical quantities such as current, voltage, and temperature. The deterioration rate may be distinguished between a deterioration rate SOHQ (State of Health Capacity) that indicates a decrease in capacity and a state of health resistance (SOHR) that indicates an increase in internal resistance. The state storage unit 12 stores the measured value of at least one sensor 10 and the calculated value of at least one state estimation unit 11. The number and configurations of the sensors 10, the state estimation unit 11, and the state storage unit 12 are determined by the configuration of the battery system 2. For example, when the battery system 2 has a hierarchical structure of the cells 23, modules 24, and racks 25 as shown in FIG. 2, each module 24 may have a sensor 10, a state estimation unit 11, and a state storage unit 12, or each module 24 may have a sensor 10 and a state estimation unit 11, and each rack 25 may have a state storage unit 12 that consolidates and stores the calculation results of the state estimation units 11 of each module 24 in the rack 25. Such a hierarchical structure is determined from the viewpoints of cost, communication speed, redundancy, and the like. In addition, the state storage unit 12 periodically stores the state of the battery system 2, for example, at one-second intervals. Therefore, when a thermal runaway occurs in the battery system 2, the state storage unit 12 stores time-series data of various states before and after the thermal runaway.

[0015] The calculation unit 30 is configured by a calculation system such as a computer, and executes a program for the battery thermal runaway cause estimation system. Fig. 3 is a block diagram showing the hardware configuration of the calculation unit in Fig. 1. The calculation unit 30 includes a processor 33, a main memory device 35, an auxiliary memory device 36, a communication interface 34, an input / output interface 37, and a bus 38 that communicatively connects these. In the following, the interface will be referred to as "I / F".

[0016] The processor 33 is a central processing unit that controls the operation of each part of the calculation unit 30. The processor 33 can be configured, for example, with a CPU (Central Processing Unit), a DSP (Digital Signal Processor), or an ASIC (Application Specific Integrated Circuit), etc. The processor 33 deploys a program stored in the auxiliary storage device 36 in a working area of ​​the main storage device 35 so that the program can be executed.

[0017] The main memory device 35 stores programs executed by the processor 33 and data processed by the processor 33. The main memory device 35 can be configured with a flash memory, a RAM (Random Access Memory), a ROM (Read Only Memory), or the like.

[0018] The auxiliary storage device 36 stores various programs and various data. The auxiliary storage device 36 stores, for example, an OS (Operating System), various programs, and various data such as tables. The auxiliary storage device 36 can be configured with a silicon disk including a non-volatile semiconductor memory (for example, a flash memory and an EPROM (Erasable Programmable ROM)), a solid state drive device, a hard disk device (HDD: Hard Disk Drive), or the like.

[0019] The communication I / F 34 is a component having a function of transmitting and receiving data between the calculation unit 30 and an external device. Examples of the external device are the state storage unit 12 and the analysis storage unit 14.

[0020] The input / output I / F 37 receives operations and instructions from an operator who operates the operation unit 21 shown in Fig. 1. The input / output I / F 37 also outputs data and information processed by the processor 33, and further data and information stored in the main memory device 35 and the auxiliary memory device 36, to the display unit 22 shown in Fig. 1.

[0021] The operation unit 21 is, for example, a switch, a button, a keyboard, a touch panel, a mouse, a microphone, and the like.

[0022] The display unit 22 is, for example, a screen, a printer, etc. Examples of the screen are an LCD (Liquid Crystal Display), an EL (Electro Luminescence) panel, an organic EL panel, etc.

[0023] <Method> FIG. 4 is a flow chart for explaining the operation of the battery thermal runaway cause estimation system according to the present embodiment. As shown in FIG. 4, in step S11, the thermal runaway analysis unit 13 shown in FIG. 1 analyzes the physical phenomenon related to the thermal runaway and its propagation in the battery system 2. Next, in step S12, the analysis result storage unit 14 shown in FIG. 1 stores the results of the analysis by the thermal runaway analysis unit 13. In the following step S13, the cause estimation unit 40 of the calculation unit 30 shown in FIG. 1 collates the data in the state storage unit 12 and the analysis result storage unit 14 to estimate the cause of the thermal runaway that occurred in the battery system 2. Finally, in step S14, the display unit 22 shown in FIG. 1 displays the cause of the thermal runaway. Details of each step will be explained below.

[0024] <Thermal runaway analysis> FIG. 5 is an explanatory diagram of a method for analyzing thermal runaway in the battery thermal runaway cause estimation system according to the present embodiment. For simplicity, FIG. 5 shows an example in which three adjacent cells are electrically connected in series. Here, the three cells are referred to as cell a, cell b, and cell c. As shown in FIG. 5, cell a is expressed by three analysis models, namely, an electric circuit model 3a, a heat generation model 4a, and a thermal circuit model 5a. The same is true for cells b and c, so their explanations are omitted. The negative electrode of cell a is electrically connected to the positive electrode of cell b, and the negative electrode of cell b is electrically connected to the positive electrode of cell c. A current source 54 is connected between the positive electrode of cell a and the negative electrode of cell c.

[0025] The electric circuit models 3a, 3b, and 3c each include an equivalent circuit of a battery that is composed of a resistor 511, a resistor 512, a capacitor 52, and a voltage source 53. This equivalent circuit is an example, and several other equivalent circuits are known, but the present invention does not depend on the configuration of the equivalent circuit. When a current flows through the electric circuit model 3a, power is consumed by the resistors 511 and 512. The heat generation model 4a calculates the amount of heat from the power consumed by the resistors 511 and 512. Then, the thermal circuit model 5a calculates the temperature of each point of the cell a from the amount of heat calculated by the heat generation model 4a. The temperature calculated by the heat generation model 4a may be fed back to the electric circuit model 3a to take into account the temperature characteristics of the resistors 511, 512, the capacitor 52, and the voltage source 53. Such temperature characteristics may be given by a calculation formula based on physics, an approximate formula obtained experimentally, or a look-up table.

[0026] The heat generation model 4a includes thermal runaway characteristics, and when the temperature calculated by the thermal circuit model 5a exceeds at least one threshold, it is deemed that thermal runaway has occurred, and a large amount of heat is instantaneously generated. It is desirable to apply the results of experimental evaluation of an actual battery to such thermal runaway characteristics. The thermal circuit model 5a considers thermal conduction, heat transfer, and heat radiation. It is desirable to apply values ​​related to these that are estimated by experimental evaluation of an actual battery, but if this is difficult, they can be obtained from the dimensions, shape, and physical quantities specific to the material of the battery.

[0027] The above explanation of cell a also applies to cells b and c, and so the explanation will be omitted. Also, since cell b is adjacent to cell a, heat transfer occurs due to thermal conduction. In other words, if the temperature of cell a rises, the temperature of cell b also rises. To represent this, the calculation results of thermal circuit model 5a are passed to thermal circuit model 5b. Similarly, the calculation results of thermal circuit model 5b are passed to thermal circuit model 5c. The connections of these thermal circuit models are determined with reference to the actual cell arrangement.

[0028] A switch 55 is connected in parallel to the voltage source 53. If this switch 55 is shorted, an internal short circuit of the cell a can be simulated. At this time, in order to more accurately simulate the actual phenomenon, a resistor may be connected in series to the switch 55. Similarly, a switch 56 is connected in parallel to the current source 54. If this switch 56 is shorted, an external short circuit can be simulated. At this time, in order to more accurately simulate the actual phenomenon, a resistor may be connected in series to the switch 56. If such an internal short circuit or external short circuit occurs, it may develop into thermal runaway. The current source 54 simulates the current flowing through the cells a, b, and c. If the current is excessive, it may develop into thermal runaway. The thermal circuit models 5a, 5b, and 5c take into account the ambient temperature. If the ambient temperature is high, it may cause thermal runaway. In addition, by arbitrarily setting values ​​for resistor 511, resistor 512, capacitor 52, and voltage source 53, and values ​​related to heat conduction, heat transfer, and heat radiation for thermal circuit model 5a, it becomes possible to analyze whether a cell will experience thermal runaway, and whether, after one cell experiences thermal runaway, the thermal runaway will propagate in a chain reaction to adjacent cells.

[0029] FIG. 6 shows an example of analysis conditions and analysis results in the battery thermal runaway cause estimation system according to the present embodiment. In the example shown in FIG. 6, the analysis conditions are five parameters, namely, current, temperature, SOC, SOHR, and SOHQ. The contents of the analysis conditions are appropriately set according to the application of the battery system. The thermal runaway analysis unit 13 shown in FIG. 1 comprehensively analyzes thermal runaway while changing the analysis conditions as shown in FIG. 6. In the example shown in FIG. 6, overcharging is set as the primary cause, and the value of SOC is changed. Specifically, the SOC is set to 120% in case 1, 130% in case 2, and 140% in case 3. As a result of the analysis, no thermal runaway occurs in case 1, one cell goes into thermal runaway with a maximum temperature of 854° C. in case 2, and two cells go into thermal runaway with a maximum temperature of 856° C. in case 3. The contents of the analysis results are appropriately set according to the application of the battery system, similar to the analysis conditions.

[0030] In addition, Fig. 6 shows an example where the SOC is changed (varied) little by little as a parameter, but the present invention is not limited to this. For example, in addition to the SOC, the current may be changed (varied) little by little, i.e., two parameters may be changed (varied) little by little to perform the analysis, or in addition to the SOC and current, the temperature may be changed (varied) little by little, i.e., three parameters may be changed (varied) little by little to perform the analysis. The number of parameters to be changed may be set appropriately. 6 shows five parameters, namely, current, temperature, SOC, SOHR, and SOHQ, as the analysis conditions, but is not limited to these. For example, it is desirable to use at least two parameters among current, temperature, SOC (also called charge amount), and SOH (also called deterioration level) as the analysis conditions.

[0031] The analysis result storage unit 14 shown in Fig. 1 stores the analysis conditions and analysis results shown in Fig. 6. When an operation is performed from the operation unit 21, a part or all of the analysis result storage unit 14 can be displayed on the display unit 22.

[0032] <Cause estimation> First, the user inputs various parameters of the situation where thermal runaway actually occurs using the operation unit 21. FIG. 7 is an example of a parameter input screen shown on the display unit 22 in FIG. 1. The types of parameters include the analysis conditions and analysis results stored in the analysis result storage unit 14. The user may give an instruction from the operation unit 21 to refer to a list of parameters or some or all of the information in the state storage unit 12. In this way, the user does not need to input parameters one by one from the operation unit 21. In addition, since various parameters at the moment when thermal runaway occurs may not be obtained, the parameters at the moment when thermal runaway occurs may be estimated from various parameters in advance and provided. Such information provided by the user is hereinafter referred to as "input information", and the information held by the analysis result storage unit 14 is referred to as "reference information".

[0033] Next, the cause estimation unit 40 obtains the similarity of the thermal runaway occurrence conditions based on the distance between the parameters of the same type, for example, by using the formula (1). Qs = Qsa + Qsb + Qsc…(1) Where: Qsa=a|Ameas-Asim| Qsb=b|Bmeas-Bsim| Qsc=c|Cmeas-Csim| Here, Qs is the similarity of the thermal runaway occurrence conditions, Ameas, Bmeas, and Cmeas are various parameters of the input information, Asim, Bsim, and Csim are various parameters of the reference information, and A, B, and C each represent the same type of parameter. For example, A is current, B is temperature, and C is SOC. Also, a, b, and c are weights for parameters A, B, and C, respectively. Although an example of three types of parameters is shown in equation (1), this is not limited to this, and two or more types of parameters will suffice, and equation (1) can be easily expanded according to the number of types of parameters of the input information.

[0034] According to formula (1), the closer the values ​​of the parameters of the input information and the reference information are, i.e., the smaller the distance, the smaller Qs becomes. The smaller Qs is, the more similar the analysis results are to the actual thermal runaway phenomenon, i.e., the higher the similarity is. If Qs is below a predetermined value, the reference information is determined to be a parameter of the primary cause of thermal runaway.

[0035] Also, each of Qsa, Qsb, and Qsc may be compared with a predetermined value, and the primary cause of the thermal runaway may be determined based on the results. Either method is an example of a method for calculating based on the distance between similar parameters, and the present invention is not limited to these.

[0036] This calculation is performed comprehensively for some or all of the analysis cases stored in the analysis result storage unit 14. It can be said that the reference information with a smaller Qs is closer to the situation of the thermal runaway that actually occurred. In the following, it is assumed that the case with the smallest Qs is case 3 in FIG.

[0037] Next, the cause estimation unit 40 infers the primary cause by referring to the causal relationships of the failure stored in the failure causal relationship storage unit 41. FIG. 8 is an example of information on the causal relationships of the failure stored in the failure causal relationship storage unit 41 of FIG. 1. In this example, performance degradation, high current, and overcharging are identified as causes of thermal runaway. These are the first layer of causes (primary causes), and the causal relationships are further structured into the second layer, the third layer, and so on. The failure causal relationship storage unit 41 stores the occurrence probability of each causal relationship, and identifies the most likely cause by reverse lookup from the result of thermal runaway.

[0038] FIG. 9 is an example of a cause estimation result shown on the display unit 22 of FIG. 1. The assumed primary causes are shown in order of increasing similarity, i.e., decreasing Qs. Here, the primary causes correspond to the causes in the first hierarchy shown in FIG. 8, and the assumed causes (secondary causes) correspond to the causes in the second hierarchy or lower hierarchy shown in FIG. 8. Furthermore, the assumed causes (secondary causes) are shown in order of increasing probability based on their occurrence probability. In this example, overcharging is identified as the direct cause (primary cause) that led to the thermal runaway, and furthermore, a sensor abnormality and a BMS abnormality are identified as assumed causes (secondary causes) in order of increasing probability.

[0039] As described above, according to this embodiment, by comprehensively comparing various parameters of the situation in which thermal runaway actually occurred with the thermal runaway analysis results prepared in advance, multiple primary causes can be identified, and further, by referring to the causal relationships of failures prepared in advance, multiple causes that cause such primary causes can be identified. From the indicated causes and their probabilities, the user can obtain suggestions as to which part of the battery system 2 should be investigated as a priority. Therefore, according to this embodiment, it is possible to provide a battery thermal runaway cause estimation system and a battery thermal runaway cause estimation method that enable rapid identification of the cause of thermal runaway occurrence. EXAMPLES

[0040] 10 is a block diagram showing an overall schematic configuration of a battery thermal runaway cause estimating system according to Example 2. The battery thermal runaway cause estimating system 1 according to this embodiment differs from Example 1 in that it includes sensors 10 provided in a transformer 62, a filter 63, and a converter 64. The other configurations are the same as those of Example 1, and therefore, in the following, descriptions that overlap with those of Example 1 will be omitted.

[0041] The converter 64 converts the DC current of the battery system 2 into an AC current. The filter 63 removes a predetermined frequency component from the AC current output by the converter 64. The transformer 62 transmits energy between a plurality of windings by utilizing electromagnetic induction, and provides the AC power output from the filter 63 to the AC system 61. With this configuration, the battery system 2 can absorb active power from the AC system 61 and supply active power to the AC power system 61. That is, the battery system 2 is used to provide a service to the AC system 61.

[0042] The transformer 62, the filter 63, and the converter 64 are connected to sensors 10, respectively, which measure physical quantities such as voltage, current, and temperature. Some or all of the physical quantities measured by these sensors 10 are stored in the state storage unit 12 and are used by the cause estimation unit 40 to estimate the cause of thermal runaway. In this way, it is possible to identify the cause of thermal runaway caused by an abnormality in elements electrically connected to the battery system 2, such as the AC system 61, the transformer 62, the filter 63, and the converter 64.

[0043] Therefore, according to this embodiment, it is possible to provide a battery thermal runaway cause estimation system suitable for an energy storage system connected to a power grid. EXAMPLES

[0044] 11 is a block diagram showing an overall schematic configuration of a battery thermal runaway cause estimating system according to Example 3. The battery thermal runaway cause estimating system 1 according to this example differs from Example 1 in that it includes sensors 10 provided on the motor 65 and the converter 64. The other configurations are the same as those of Example 1, and therefore, in the following, descriptions that overlap with those of Example 1 will be omitted.

[0045] The converter 64 converts the direct current of the battery system 2 into alternating current and drives the motor 65. If a fan (not shown) is attached to the motor 65, the fan rotates when the motor 65 is driven, generating suction force. With this configuration, a cordless vacuum cleaner can be configured using the energy of the battery system 2. Furthermore, if a reduction gear (not shown) is attached to the motor 65 and wheels are further attached that are mechanically connected to the reduction gear, a car that can run using the energy of the battery system 2 can be configured.

[0046] The converter 64 and the motor 65 are connected to sensors 10, respectively, which measure physical quantities such as voltage, current, acceleration, angular velocity, and temperature. Some or all of the physical quantities measured by the sensors 10 are stored in the state storage unit 12 and are used by the cause estimation unit 40 to estimate the cause of thermal runaway. In this way, it is possible to identify the cause of thermal runaway caused by an abnormality in elements electrically and mechanically connected to the battery system 2, such as the converter 64 and the motor 65.

[0047] Therefore, according to this embodiment, it is possible to provide a battery thermal runaway cause estimation system that enables rapid identification of the cause of thermal runaway that occurs in a cordless vacuum cleaner or an electric vehicle.

[0048] The present invention is not limited to the above-mentioned embodiment, but includes various modified examples. For example, the above-mentioned embodiment has been described in detail to easily explain the present invention, and the present invention is not necessarily limited to those including all of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. [Explanation of symbols]

[0049] 1. Battery thermal runaway cause estimation system 2. Battery system 3a, 3b, 3c…Electric circuit model 4a, 4b, 4c…Fever model 5a, 5b, 5c…Thermal circuit model 10…Sensor 11... State estimation unit 12...Status memory section 13…Thermal runaway analysis department 14…Analysis result storage unit 21...Operation unit 22...Display section 23…Cell 24…Module 25…Rack 26…Container 30...Calculation section 33…Processor 34…Communication interface 35…Main memory 36…Auxiliary storage device 37... Input / Output Interface 38…Bus 40…Cause estimation department 41…Failure causation memory section 51,511,512…Resistance 52…Capacitor 53...Voltage source 54…Current source 55,56…Switch 61…AC system 62...Trans 63…Filter 64...Converter 65…Motor

Claims

1. a thermal runaway analysis unit that performs an analysis of thermal runaway using at least two parameters among a current, a voltage, a temperature, a charge amount, and a deterioration degree as analysis conditions; an analysis result storage unit that stores the analysis conditions and the analysis results; A sensor attached to a battery system including a plurality of chargeable and dischargeable secondary batteries; a state estimation unit that estimates a state quantity of the battery system from the physical quantity measured by the sensor; a state storage unit that stores the physical quantity and / or the state quantity; a calculation unit that compares the same type of parameters stored in the analysis result storage unit and the state storage unit, and when the degree of similarity between the parameters exceeds a predetermined value, estimates that the analysis condition is the cause of the battery thermal runaway; a display unit that displays the cause of the battery thermal runaway.

2. The battery thermal runaway cause estimation system according to claim 1, A battery thermal runaway cause estimating system, characterized in that the similarity is calculated based on a distance between parameters of the same type stored in the analysis result storage unit and the state storage unit, respectively.

3. 3. The battery thermal runaway cause estimation system according to claim 2, The thermal runaway analysis unit analyzes an electric circuit model, a heat generation model, and a thermal circuit model of the battery system.

4. The battery thermal runaway cause estimation system according to claim 3, The system for estimating the cause of thermal runaway in a battery, wherein the analysis result storage unit stores the analysis results including the presence or absence of thermal runaway and the number of times the thermal runaway has propagated.

5. The battery thermal runaway cause estimation system according to claim 4, Further, a failure causal relationship storage unit is provided for storing the causal relationship and occurrence probability of the failure, The system for estimating the cause of battery thermal runaway, wherein the calculation unit estimates a secondary cause of the cause of the battery thermal runaway based on the information stored in the failure causal relationship storage unit.

6. The battery thermal runaway cause estimation system according to claim 5, The battery thermal runaway cause estimating system according to the present invention is characterized in that the display unit displays a plurality of the battery thermal runaway causes and / or the secondary causes in order of likelihood.

7. 7. A battery thermal runaway cause estimating system according to claim 6, the battery system is connected to a power grid via a power converter; The battery thermal runaway cause estimating system according to the present invention, wherein the state memory unit stores information from a sensor attached to the power converter.

8. 7. The battery thermal runaway cause estimation system according to claim 6, the battery system is connected to a motor via a power converter; The battery thermal runaway cause estimating system according to the present invention, wherein the state memory unit stores information of a sensor attached to the power converter and / or the motor.

9. A thermal runaway analysis unit performs an analysis of thermal runaway using at least two parameters from among current, voltage, temperature, charge amount, and deterioration degree as analysis conditions; an analysis result storage unit storing the analysis conditions and the analysis results; a calculation unit comparing the analysis conditions with measured values ​​of at least two parameters among current, voltage, temperature, charge amount, and deterioration level, and estimating that the analysis conditions are the cause of the battery thermal runaway when the degree of similarity exceeds a predetermined value; a display unit displaying the cause of the battery thermal runaway.

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