Judgment system and judgment method

Abstract

This invention provides a detection system and method that can monitor battery pack overheating even while the ECU is stopped. [Solution] When the ECU is stopped, if an abnormality in the first state value indicating the state of the battery pack, caused by overheating inside the battery pack, is detected by a mechanical sensor, a startup operation is performed to start the ECU, and overheating inside the battery pack is determined after the ECU is started.

Description

Technical Field

[0001] The present invention relates to a determination system and a determination method.

Background Art

[0002] There is known a technique for detecting an abnormality in a battery pack that houses a plurality of battery cells, measuring an internal state value of the battery pack by a state value measurement unit different from a thermistor that acquires a voltage value of the battery cell and acquires the temperature of the battery cell, and determining an abnormality in the battery pack based on the voltage value and the state value (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the technique described in Patent Document 1, since the battery ECU determines an abnormality in the battery pack, there is a problem that overheating of the battery pack cannot be monitored while the battery ECU is stopped.

[0005] The problem to be solved by the present invention is to provide a determination system and a determination method capable of monitoring overheating of a battery pack even while an ECU is stopped.

Means for Solving the Problems

[0006] The present invention performs a startup operation for starting an ECU when an abnormality in a first state value indicating the state of a battery pack caused by overheating in the battery pack is detected by a mechanical sensor in a state where the ECU is stopped, and solves the above problems by determining overheating in the battery pack after the ECU is started. [Effects of the Invention]

[0007] According to the present invention, overheating of the battery pack can be monitored even while the ECU is stopped. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a block diagram of a determination system according to one embodiment of the present invention. [Figure 2] Figure 2 is a schematic plan view showing an example of the interior of a battery pack according to this embodiment. [Figure 3] Figure 3 shows an example of the status value, ECU status, and determination result in this embodiment. [Figure 4] Figure 4 is a flowchart showing an example of the processing procedure of the determination method executed in the determination system according to the first embodiment of the present invention. [Figure 5] Figure 5 is a block diagram of a determination system according to a second embodiment of the present invention. [Modes for carrying out the invention]

[0009] <<First Embodiment>> Hereinafter, a determination system and determination method according to an embodiment of the present invention will be described with reference to the drawings. Figure 1 is a block diagram of a determination system according to the first embodiment of the present invention. As shown in Figure 1, the determination system 100 comprises a battery pack 1, a cell 2, a mechanical sensor 3, an ECU activation mechanism 4, a voltage sensor 5, and an ECU 10.

[0010] The battery pack 1 comprises multiple cells 2 internally. The battery pack 1 comprises battery groups in which multiple battery cells (battery groups) 2 are connected in series or parallel. The battery pack 1 is equipped with multiple battery modules, each modularized with multiple cells (battery cells) 2, and houses the battery modules in a case. The cells 2 are, for example, lithium-ion secondary batteries. As an example of a cell 2, a flat laminate film lithium-ion secondary battery has a power generation element in which electrode layers (positive electrode layer and negative electrode layer) and a separator are laminated and filled with electrolyte, a positive electrode tab connected to the positive electrode layer, a negative electrode tab connected to the negative electrode layer, and an outer casing member that houses and seals these. A detailed explanation of the materials included in the lithium-ion secondary battery and the detailed structure of the battery is omitted, but well-known battery materials and structures can be applied to lithium-ion secondary batteries. The cell 2 is not limited to a secondary battery containing electrolyte, but may also be a lithium-ion battery containing a solid electrolyte layer (a so-called all-solid-state lithium-ion battery). The cell 2 is an example of a "battery cell" in the claims. Battery pack 1 is installed in the vehicle and used as a battery to supply power to the vehicle.

[0011] The mechanical sensor 3 is a sensor that mechanically detects a state value indicating the state of the battery pack 1. The state value detected by the mechanical sensor 3 is also called the first state value. The mechanical sensor 3 is a device that detects physical changes in the battery pack 1 and converts them into electrical signals. Specifically, the mechanical sensor 3 controls the on / off switching of the electrical signal through mechanical operation. The state value is a value indicating the physical state of the battery pack 1, and includes the temperature, pressure, and voltage of the battery pack 1. The first state value includes, for example, the temperature and pressure of the battery pack 1. As will be described later, the second state value is a value different from the first state value, and includes, for example, the voltage of the battery pack 1.

[0012] The mechanical sensor 3 performs a startup operation to activate the ECU 10 when it detects an abnormality in the first state value caused by overheating in the battery pack 1 while the ECU 10 is stopped. Overheating causes an abnormality in the state of the battery pack 1. This causes abnormalities in the state value of the battery pack 1 detected by the sensor, such as an excessive rise or fall. Overheating means a state in which the heat cannot be controlled due to an abnormal increase in heat. If overheating occurs in one cell 2 in the battery pack 1, it is possible that other cells 2 will also overheat in a chain reaction. The startup operation is, for example, an operation to turn on an electrical signal switch, which outputs an electrical signal to the ECU startup mechanism 4. As described above, the mechanical sensor 3 performs detection of the first state value and the startup operation without power supply. In this embodiment, the mechanical sensor 3 may also perform a startup operation to directly activate the ECU 10 without going through the ECU startup mechanism 4.

[0013] The mechanical sensor 3 is installed inside the battery pack 1. For example, the mechanical sensor 3 is installed around the cell 2. The mechanical sensor 3 is also installed on a gas discharge path for discharging gas generated inside the battery pack 1 to the outside. Here, the placement of the mechanical sensor 3 will be explained using Figure 2. Figure 2 is a schematic plan view showing an example of the inside of a battery pack according to this embodiment. Multiple cells 2 are arranged inside the battery pack 1. In the example in Figure 2, four battery modules are arranged. The battery pack 1 is equipped with a gas discharge port 7 for discharging gas generated inside the battery pack 1 to the outside. The placement of the mechanical sensor 3 is the hatched area in Figure 2. Specifically, the placement of the mechanical sensor 3 includes the area 3a around the battery module and the area 7a on the gas discharge path for discharging gas generated inside the battery pack 1 to the outside.

[0014] In this embodiment, the ECU 10 transitions to a stopped state (sleep state) when the ignition switch of the vehicle equipped with the battery pack 1 is turned off. For example, the ECU 10 enters a stopped state when the vehicle is parked.

[0015] The mechanical sensor 3 is, for example, a mechanical temperature sensor that mechanically detects the temperature of the battery pack 1. A bimetallic thermostat is used as the mechanical temperature sensor. When the mechanical sensor 3 is a mechanical temperature sensor, it activates when it detects an abnormal temperature caused by overheating in the battery pack 1 while the ECU 10 is stopped. Specifically, the mechanical sensor 3 switches an electrical signal on and off in response to temperature changes. When the temperature exceeds a temperature threshold, the mechanical sensor 3 operates to switch the electrical signal on. The temperature threshold is a threshold value used to determine a temperature rise, and is set in advance according to the battery material of cell 2, the battery structure of cell 2, etc. The temperature threshold may also be a value determined experimentally. The mechanical sensor 3 is designed in terms of materials and structure to activate mechanically when the temperature exceeds the temperature threshold.

[0016] The mechanical sensor 3 is, for example, a mechanical pressure sensor that mechanically detects the pressure inside the battery pack 1. When the mechanical sensor 3 is a mechanical pressure sensor, it activates when it detects an abnormal pressure caused by overheating inside the battery pack 1 while the ECU 10 is stopped. Specifically, the mechanical sensor 3 switches an electrical signal on and off in response to changes in pressure. When the pressure exceeds the pressure threshold, the mechanical sensor 3 operates to switch the electrical signal on. The inside of the battery pack 1 is a sealed space that can contain the pressure, and the pressure rises due to thermal expansion. The mechanical sensor 3 is installed in the sealed space. The pressure threshold is a threshold value for determining the pressure rise, and is set in advance according to the battery material of cell 2, the battery structure of cell 2, etc. The pressure threshold may also be a value determined experimentally. The mechanical sensor 3 is designed in terms of materials and structure to mechanically activate when the pressure exceeds the pressure threshold.

[0017] The ECU starting mechanism 4 operates by the starting operation of the mechanical sensor 3 to start the ECU 10. For example, when an electrical signal is input from the mechanical sensor 3, the ECU starting mechanism 4 outputs a control command for starting (waking up) the ECU 10 to the ECU 10.

[0018] The voltage sensor 5 is a sensor that detects the cell voltages of the plurality of cells 2. The voltage sensor 5 detects the voltage between the terminals of the cell 2 and is connected between the wirings connected to the positive and negative electrodes of the cell 2. The voltage sensor 5 outputs the detected voltage of the cell 2 to the ECU 10. A plurality of voltage sensors 5 may be provided according to the number of cells 2, or there may be one. The voltage sensor 5 may be provided outside the battery pack 1, or the voltage sensor 5 may be provided inside the battery pack 1. For example, the cell 2 has a tab for voltage detection, and a wiring for extraction is connected to the detection tab. Then, by connecting the voltage sensor 5 to the wiring for extraction from outside the pack, the voltage sensor 5 can be electrically connected to the cell 2 to detect the voltage of the cell 2.

[0019] The ECU 10 is an electronic control unit that determines overheating inside the battery pack 1. In the present embodiment, the ECU 10 determines overheating inside the battery pack 1 after startup. The ECU 10 includes a controller 11. The controller 11 is composed of a computer having hardware and software, and has a memory that stores programs and a CPU that executes the programs stored in this memory. The controller 11 determines overheating inside the battery pack based on the second state value of the battery pack 1. The second state value is a state value different from the first state value among the state values of the battery pack 1, and for example, is the voltage of the battery pack 1, that is, the detected voltage of the voltage sensor 5. The controller 11 has functions such as a function to start the ECU 10, a function to determine abnormality of the cell voltage, and a function to determine overheating inside the battery pack 1, and has a startup unit 12, a voltage abnormality determination unit 13, and an overheating determination unit 14 as function blocks corresponding to each function.

[0020] The startup unit 12 executes a startup process for starting the ECU 10. When the startup unit 12 receives a control command for starting the ECU 10 from the ECU startup mechanism 4, it executes the startup process to put the ECU 10 into an operating state (wake-up state). In this embodiment, after the ECU 10 is started, the ECU 10 determines overheating in the battery pack 1 by the voltage abnormality determination unit 13 and the overheat determination unit 14.

[0021] The voltage abnormality determination unit 13 determines an abnormality in the voltage of the battery pack 1 based on the detected voltage of the voltage sensor 5. The voltage abnormality determination unit 13 acquires the detected voltage of the cell 2 from the voltage sensor 5. The voltage abnormality determination unit 13 compares the detected voltage of the cell 2 with the cell voltage threshold value. The cell voltage threshold value is a determination threshold value for determining a decrease in the cell voltage, and is preset according to the battery material included in the cell 2, the battery structure of the cell 2, etc. Note that the cell voltage threshold value may be a value experimentally obtained according to the voltage drop that occurs when overheating occurs in the cell 2. A normal operating voltage range is preset for the cell 2. For example, when the battery pack 1 is mounted on a vehicle, the operating voltage range is determined so as to include the range of voltage changes caused by charging and discharging of the battery pack 1 during vehicle running, vehicle parking, or charging by an external charging device of the vehicle. Then, the cell voltage threshold value may be set to a voltage lower than the lower limit value of the operating voltage range.

[0022] When the detected voltage of the cell 2 is less than or equal to the cell voltage threshold value, the voltage abnormality determination unit 13 determines that an abnormality in the voltage of the battery pack 1 has occurred. On the other hand, when the detected voltage of the cell 2 is higher than the cell voltage threshold value, the voltage abnormality determination unit 13 determines that no abnormality in the voltage of the battery pack 1 has occurred.

[0023] Also, in this embodiment, the controller 11 is not limited to determining an abnormality in the voltage of the battery pack 1 in the voltage abnormality determination, and may determine an abnormality in another second state value as long as it can determine an abnormality in the state of the battery pack 1 caused by overheating of the battery pack 1.

[0024] After the ECU 10 is started, the overheating detection unit 14 determines whether the battery pack 1 is overheating based on the voltage of the battery pack 1 as a second state value. Specifically, the overheating detection unit 14 determines that overheating has occurred in the battery pack 1 if the voltage abnormality detection unit 13 determines that there is an abnormality in the voltage of the battery pack 1. The overheating detection unit 14 determines that there is no overheating in the battery pack 1 if the voltage abnormality detection unit 13 determines that there is no abnormality in the voltage of the battery pack 1.

[0025] As described above, the determination system 100 according to this embodiment uses a mechanical sensor 3 to start the ECU 10 when the ECU 10 is stopped. The mechanical sensor 3 does not consume power and does not start the ECU 10 unless an abnormality in the battery pack 1 is detected, so it can accurately determine abnormalities due to overheating of the battery pack 1 while saving power consumption. Also, when overheating occurs in the cell 2 within the battery pack 1, the cell 2 becomes hot. On the other hand, heat generation in the cell 2 also occurs during normal charging and discharging, so the temperature of the cell may rise sharply during rapid charging or high-load driving. In this embodiment, overheating is different from this type of heat generation. However, unlike this embodiment, a determination method that judges based only on the temperature rise of the cell 2 cannot distinguish whether the high temperature abnormality of the cell 2 is due to overheating or other factors, and there is a risk of false detection. Therefore, in this embodiment, by combining the detection of an abnormality in the first state value (temperature or pressure) of the battery pack 1 by the mechanical sensor 3 and the determination of an abnormality in the second state value (voltage) of the battery pack 1 by the ECU 10, overheating inside the battery pack 1 can be determined more accurately by monitoring two different abnormal state values.

[0026] Referring to Figure 3, the cell state value characteristics, judgment logic, and judgment method when overheating occurs in the battery pack 1 will be explained. Figure 3 is a diagram showing an example of the state value, ECU state, and judgment result in this embodiment. In the graph of Figure 3, the state of the ECU 10 indicates "sleep state" at a low level and "started state" at a high level. The judgment flag of the judgment result indicates "normal" at a low level and "abnormal" at a high level. "Normal" means that no overheating has occurred in the battery pack 1. "Abnormal" means that overheating has occurred in the battery pack 1. The mechanical sensor 3 detects the first state value of the battery pack 1 at a predetermined period. The first state value is pressure or temperature. In the example of Figure 3, the battery pack 1 begins to overheat at time t1, and as a result, the first state value also begins to rise. Also, from time t1, the second state value begins to fall. The second state value is voltage. When the first state value exceeds a threshold at time t2, the mechanical sensor 3 detects an abnormality in the first state value and performs a startup operation to start the ECU 10. As a result, at time t2, ECU10 transitions from sleep state to wake-up state. After waking up, ECU10 acquires a second state value and determines whether or not an abnormality has occurred in the second state value. In the example in Figure 3, at time t2 when ECU10 was woken up, the second state value is below the threshold, so ECU10 determines that an abnormality has occurred in the second state value. Based on the abnormality determination of the second state value, ECU10 then determines that overheating has occurred in the battery pack 1. In the example in Figure 3, at time t3, ECU10 determines that overheating has occurred, and the determination flag is updated to "abnormal".

[0027] Next, with reference to Figure 4, an example of the procedure for the determination method performed by the determination system 100 will be described. Figure 4 is a flowchart showing an example of the processing procedure for the determination method performed in the determination system according to the first embodiment of the present invention. The processing described below is performed by the determination system 100 at predetermined time intervals.

[0028] First, in step S1, the mechanical sensor 3 detects a first state value, and if an abnormality is detected in the first state value, the process proceeds to step S2. The first state value is pressure or temperature. If the mechanical sensor 3 does not detect an abnormality in the first state value, the control flow ends. If the mechanical sensor 3 does not detect an abnormality in the first state value, the detection of the first state value by the mechanical sensor 3 is repeatedly performed. In step S2, the mechanical sensor 3 performs a startup operation to start the ECU 10. For example, the startup operation turns on an electrical signal switch. In step S3, the ECU startup mechanism 4 is activated by the power supplied by the startup operation in step S2, and the ECU 10 is started. After startup, in step S4, the ECU 10 determines if there is an abnormality in the second state value. The second state value is the voltage of the battery pack 1. For example, the ECU 10 determines that an abnormality in the second state value has occurred if the voltage of the battery pack 1 has fallen below a threshold. In step S5, the ECU 10 performs an overheating determination based on the determination result in step S4. Specifically, if the ECU10 determines in step S4 that an abnormality has occurred in the second state value, it proceeds to step S6. If the ECU10 determines in step S4 that no abnormality has occurred in the second state value, it proceeds to step S7. In step S6, the ECU10 determines that overheating has occurred in the battery pack 1. In step S7, the ECU10 determines that the battery pack 1 is normal. The control flow ends after the determination.

[0029] As described above, the determination system according to this embodiment is a determination system comprising a battery pack, a mechanical sensor, and an ECU that determines overheating in the battery pack. When the mechanical sensor detects an abnormality in a first state value indicating the state of the battery pack caused by overheating in the battery pack while the ECU is stopped, it performs a startup operation to start the ECU, and the ECU determines overheating in the battery pack after startup. This allows monitoring of overheating of the battery pack even while the ECU is stopped.

[0030] Furthermore, the determination system according to this embodiment further includes an ECU activation mechanism that activates the ECU, and the ECU activation mechanism is activated by an activation operation to activate the ECU. This makes it possible to activate the ECU by the activation operation of a mechanical sensor.

[0031] Furthermore, in the determination system according to this embodiment, after startup, the ECU determines overheating inside the battery pack based on a second state value that is different from the first state value among the state values ​​indicating the state of the battery pack. By determining overheating inside the battery pack using two different state values, it is possible to monitor overheating inside the battery pack more accurately.

[0032] Furthermore, in the determination system according to this embodiment, after startup, the ECU determines overheating inside the battery pack based on the voltage of the battery pack as a second state value. As a result, since the voltage remains in an abnormal state even after time has passed, overheating inside the battery pack can be accurately determined even when the ECU is activated by a mechanical sensor to determine overheating.

[0033] Furthermore, in the determination system according to this embodiment, the mechanical sensor includes a mechanical pressure sensor that mechanically detects the pressure inside the battery pack. The mechanical pressure sensor is installed in a sealed space that can contain the pressure inside the battery pack. When the ECU is stopped, if an abnormal pressure inside the battery pack caused by overheating is detected, the ECU performs an activation operation. After activation, the ECU determines overheating inside the battery pack based on a second state value different from the pressure inside the battery pack. This allows for more accurate monitoring of overheating inside the battery pack by determining overheating using two different state values, including the pressure inside the battery pack. Moreover, in the determination system according to this embodiment, after activation, the ECU determines overheating inside the battery pack based on the voltage of the battery pack as a second state value. As a result, since the voltage remains in an abnormal state even after time has passed, overheating inside the battery pack can be accurately determined even when the ECU is activated by the mechanical sensor.

[0034] Furthermore, in the determination system according to this embodiment, the mechanical sensor includes a mechanical temperature sensor that mechanically detects the temperature of the battery pack. The mechanical temperature sensor activates when it detects an abnormal temperature in the battery pack caused by overheating inside the battery pack while the ECU is stopped. After activation, the ECU determines overheating inside the battery pack based on a second state value different from the actual battery pack temperature. This allows for early detection of abnormal temperature in the battery pack caused by overheating, enabling the ECU to be activated in the initial stages of overheating. Moreover, in the determination system according to this embodiment, after activation, the ECU determines overheating inside the battery pack based on the voltage of the battery pack as a second state value. As a result, since the voltage remains in an abnormal state even after time has passed, overheating inside the battery pack can be accurately determined even when the overheating determination is made after the ECU has been activated by the mechanical sensor.

[0035] As described above, the determination method according to this embodiment is a determination method performed by a determination system comprising a battery pack, a mechanical sensor, and an ECU that determines overheating in the battery pack. The mechanical sensor performs a startup operation to start the ECU when it detects an abnormality in a first state value indicating the state of the battery pack caused by overheating in the battery pack while the ECU is stopped, and the ECU determines overheating in the battery pack after startup. This allows monitoring of overheating in the battery pack even while the ECU is stopped.

[0036] <<Second Embodiment>> Furthermore, as shown in Figure 5, the determination system 100 of the present invention may also be equipped with a cooling unit 6 in the battery pack 1. Figure 5 is a block diagram of the determination system according to the second embodiment of the present invention. In the second embodiment, the configurations other than those described below are the same as those of the first embodiment described above, and in the following description, the same configurations and control processes as in the first embodiment will be omitted from the description, but the description of the first embodiment will be appropriately referenced in the omitted descriptions. The cooling unit 6 is a cooling device that cools the cells 2 in the battery pack 1, and cools the cells 2 in the battery pack 1 by means of, for example, water cooling or air cooling. The controller 11 may further be equipped with a cooling determination unit 15. The cooling determination unit 15 determines whether or not to cool the cells 2. If the cooling determination unit 15 determines that the cells 2 should be cooled, it causes the cooling unit 6 to cool the cells 2. For example, the cooling determination unit 15 determines that the cells 2 should be cooled on the condition that the ECU 10 has been started, and outputs a control command to the cooling unit 6 to cool the cells 2.

[0037] As described above, the determination system according to this embodiment further includes a cooling unit for cooling the battery cells in the battery pack. After startup, the ECU determines whether or not to cool the battery cells, and if it determines that the battery cells should be cooled, it cools the battery cells using the cooling unit. This allows the ECU to monitor for overheating of the battery pack and execute necessary processes to suppress the occurrence of overheating of the battery pack, even while the ECU is stopped.

[0038] Furthermore, in the determination system according to this embodiment, the mechanical sensor includes a mechanical temperature sensor that mechanically detects the temperature of the battery pack. The mechanical temperature sensor activates when it detects an abnormal temperature in the battery pack caused by overheating inside the battery pack while the ECU is stopped. This allows for early detection of abnormal temperatures in the battery pack caused by overheating inside the battery pack, enabling the ECU to be activated in the initial stages of overheating. [Explanation of symbols]

[0039] 1 Battery pack 2 cells 3 Mechanical Sensors 4 ECU activation mechanism 5. Voltage Sensor 6 Cooling section 10 ECU 11 Controllers 12 Starting part 13 Voltage Anomaly Detection Unit 14 Overheating judgment section 15 Cooling judgment section 100 Judgment System

Claims

1. A determination system comprising a battery pack, a mechanical sensor, and an ECU for determining overheating within the battery pack, The mechanical sensor, when the ECU is stopped, detects an abnormality in the first state value indicating the state of the battery pack caused by overheating inside the battery pack, and performs a startup operation to start the ECU. The ECU is a determination system that determines overheating in the battery pack after startup.

2. A determination system according to claim 1, The ECU startup mechanism for starting the aforementioned ECU is further provided, The ECU startup mechanism is a determination system that operates in response to the startup operation and starts the ECU.

3. A determination system according to claim 1 or 2, The ECU is a determination system that, after startup, determines overheating in the battery pack based on a second state value, which is different from the first state value, among the state values ​​indicating the state of the battery pack.

4. A determination system according to claim 3, The ECU is a determination system that, after startup, determines overheating in the battery pack based on the voltage of the battery pack as the second state value.

5. A determination system according to claim 3, The mechanical sensor includes a mechanical pressure sensor that mechanically detects the pressure inside the battery pack. The aforementioned mechanical pressure sensor is It is installed in a sealed space that can contain the pressure inside the battery pack, When the ECU is stopped, if an abnormal pressure in the battery pack caused by overheating in the battery pack is detected, the startup operation is performed. The ECU is a determination system that, after startup, determines overheating in the battery pack based on a second state value different from the pressure inside the battery pack.

6. A determination system according to claim 5, The ECU is a determination system that, after startup, determines overheating in the battery pack based on the voltage of the battery pack as the second state value.

7. A determination system according to claim 3, The mechanical sensor includes a mechanical temperature sensor that mechanically detects the temperature of the battery pack. The mechanical temperature sensor performs the startup operation when it detects an abnormal temperature in the battery pack caused by overheating inside the battery pack while the ECU is stopped. The ECU is a determination system that, after startup, determines overheating in the battery pack based on a second state value different from the temperature of the battery pack.

8. A determination system according to claim 7, The ECU is a determination system that, after startup, determines overheating in the battery pack based on the voltage of the battery pack as the second state value.

9. A determination system according to claim 1 or 2, The battery pack further includes a cooling unit for cooling the battery cells within the battery pack, The aforementioned ECU is After startup, it is determined whether or not to cool the battery cell. A determination system that, when it is determined that the battery cell needs to be cooled, causes the cooling unit to cool the battery cell.

10. A determination system according to claim 9, The mechanical sensor includes a mechanical temperature sensor that mechanically detects the temperature of the battery pack. The mechanical temperature sensor is a determination system that performs the startup operation when it detects an abnormal temperature in the battery pack caused by overheating inside the battery pack while the ECU is stopped.

11. A determination method performed by a determination system comprising a battery pack, a mechanical sensor, and an ECU for determining overheating within the battery pack, The mechanical sensor, when the ECU is stopped, detects an abnormality in the first state value indicating the state of the battery pack caused by overheating inside the battery pack, and performs a startup operation to start the ECU. The ECU is a determination method for determining overheating in the battery pack after startup.

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