Battery system

Abstract

This device accurately determines whether or not delamination of the thermal conductive material has occurred. [Solution] If the execution conditions are met (YES in S100), the ECU executes a process that includes the steps of acquiring the battery temperature and the inlet temperature (S102), acquiring the amount of heat exchanged in the chiller (S104), acquiring the amount of heat generated by the battery (S106), acquiring the amount of heat exchanged in the heat exchanger (S108), calculating the thermal resistance k (S110), and if it is determined that the thermal resistance k is greater than the threshold k (0) (YES in S112), determining that peeling of the thermal conductive material has occurred (S114).

Description

Technical Field

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[0001] The present disclosure relates to a battery system.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2021-064488 (Patent Document 1) discloses a technique for determining that an abnormality has occurred in the refrigerant system of a cooling device when an abnormality of an air conditioner has not been detected and the detected value of a temperature sensor is higher than a predetermined value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a battery system includes, for example, a battery and a heat exchange member, and a heat conductive material is provided between the battery and the heat exchange member, peeling of the heat conductive material may occur due to external impact during rough driving caused by poor coating of the heat conductive material or the like. When peeling occurs in the heat conductive material, it becomes impossible to adjust the battery to an appropriate temperature. Since the state of the heat conductive material cannot be confirmed from the outside of the battery system, it is required to accurately determine whether or not peeling has occurred in the heat conductive material.

[0005] The present disclosure has been made to solve the above-described problems, and an object thereof is to provide a battery system that accurately determines whether or not peeling has occurred in a heat conductive material.

Means for Solving the Problems

[0006] A battery system relating to a certain aspect of this disclosure includes an energy storage device, a heat exchanger that performs heat exchange with the energy storage device using a refrigerant, a thermal conductive material provided between the energy storage device and the heat exchanger, a first detection device that detects a first temperature which is the temperature of the refrigerant flowing into the heat exchanger, a second detection device that detects a second temperature which is the temperature of the energy storage device, and a control device that calculates the thermal resistance between the heat exchanger and the energy storage device by dividing the value obtained by subtracting the second temperature from the first temperature by the amount of heat exchanged in the heat exchanger. The control device determines that the thermal conductive material is in an abnormal state if the calculated thermal resistance is greater than a threshold value.

[0007] In this configuration, if the thermal conductive material delaminates, heat exchange between the energy storage device and the heat exchanger will not function properly, causing the temperature of the energy storage device to rise and the amount of heat exchanged in the heat exchanger to decrease. As a result, the thermal resistance will increase. Therefore, the abnormal condition of the thermal conductive material can be accurately determined using thermal resistance.

[0008] In one embodiment, the heat exchanger is connected to a chiller. The control device calculates the amount of heat exchanged in the heat exchanger using a predetermined relationship between the amount of heat generated by the energy storage device, the amount of heat exchanged in the chiller, and the amount of heat exchanged in the heat exchanger.

[0009] In this way, the amount of heat exchanged in a heat exchanger can be calculated with high accuracy using a map.

[0010] Furthermore, in one embodiment, the control device determines that a state in which the thermal conductive material has detached from at least one of the heat exchanger and the energy storage device is an abnormal state if the thermal resistance is greater than a threshold.

[0011] In this way, it is possible to accurately determine whether or not delamination of the thermal conductive material has occurred using thermal resistance. [Effects of the Invention]

[0012] According to this disclosure, it is possible to provide a battery system that can accurately determine whether or not delamination of the thermal conductive material has occurred. [Brief explanation of the drawing]

[0013] [Figure 1] This figure shows an example of the configuration of a vehicle equipped with a battery system according to an embodiment of the present disclosure. [Figure 2] This flowchart shows an example of a process performed by the ECU. [Figure 3] This figure shows an example of the relationship between the heat generated by the battery, the heat exchange rate of the chiller, and the heat exchange rate of the heat exchanger. [Modes for carrying out the invention]

[0014] The embodiments of this disclosure will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0015] Figure 1 shows an example of the configuration of a vehicle 200 equipped with a battery system 100 according to an embodiment of the present disclosure.

[0016] Vehicle 200 is electrically connected to power stand 300 via cable 310, enabling power exchange (charging and discharging) between the vehicle and power stand 300. AC power is exchanged between the vehicle 200 and the connector 311 provided at the end of cable 310. Power stand 300 exchanges power with the power grid PG.

[0017] Vehicle 200 is equipped with a battery system 100, an inlet 210, an MG (Motor Generator) 220, and a charger / discharger 230.

[0018] Vehicle 200 is configured to run using electricity stored in the battery 40 of the battery system 100. Vehicle 200 is, for example, an electric vehicle (BEV) without an engine (internal combustion engine). However, it is not limited to this, and vehicle 200 may be a plug-in hybrid electric vehicle (PHEV) equipped with an internal combustion engine, or another electric vehicle (xEV).

[0019] The inlet 210 is provided on the exterior portion of the vehicle 200 and has a shape that can be fitted with the connector 311. The exterior portion includes an opening / closing lid, and when the inlet 210 is not in use, the opening / closing lid is closed, thereby suppressing the inlet 210 from being covered by the opening / closing lid and being exposed to the outside.

[0020] MG220 is, for example, a three-phase alternating current rotating electric machine. MG220 functions as a driving motor for the vehicle 200. MG220 is driven by the alternating current power from the battery system 100 and rotates the driving wheels of the vehicle 200. Also, MG220 performs regenerative power generation and outputs the generated alternating current power to the battery system 100. Note that the number of driving motors provided in the vehicle 200 is not particularly limited to one and may be two or more.

[0021] The charger / discharger 230 is connected to the inlet 210 and the battery system 100 (specifically, the relay 60), respectively. The charger / discharger 230 performs power conversion when transmitting power to and from the power stand 300. The charger / discharger 230, for example, converts the alternating current power supplied from the power stand 300 into direct current power and supplies it to the battery system 100, or converts the direct current power supplied from the battery system 100 into alternating current power and supplies it to the power stand 300. The charger / discharger 230 includes a power conversion circuit (for example, an inverter and a converter) and is configured to be able to adjust the charging current or the discharging current.

[0022] The battery system 100 includes an ECU (Electronic Control Unit) 10, a PCU (Power Control Unit) 20, a battery 40, an SMR (System Main Relay) 50, and a relay 60.

[0023] ECU 10 is a control device including a processor 11, a RAM (Random Access Memory) 12, and a storage device 13. The storage device 13 is configured to be able to store the stored information. In addition to programs, information used in the programs (for example, maps, mathematical formulas, and various parameters) are stored in the storage device 13. In the present embodiment, by the processor 11 executing the programs stored in the storage device 13, various processes by the ECU 10 are executed. However, these processes may be executed only by hardware (electronic circuits) without using software. The ECU 10 controls, for example, the operations of the PCU 20, the SMR 50, the relay 60, and the charger / discharger 230.

[0024] A voltage sensor 43, a current sensor 44, a battery temperature sensor 45, and an inlet temperature sensor 46 are connected to the ECU 10. The voltage sensor 43 detects the voltage Vb of the battery 40 and outputs a signal indicating the detection result to the ECU 10. The current sensor 44 detects the current Ib flowing through the battery 40 and outputs a signal indicating the detection result to the ECU 10. Further, the battery temperature sensor 45 detects the temperature Tb of the battery 40 and outputs a signal indicating the detection result to the ECU 10. Also, the inlet temperature sensor 46 detects the temperature Tw of the refrigerant flowing into the heat exchanger 240 and outputs a signal indicating the detection result to the ECU 10.

[0025] The battery 40 includes a plurality of storage cells. The plurality of storage cells are arranged, for example, in a predetermined number array along the thickness direction of the storage cells. The predetermined number is not particularly limited. The storage cell is a secondary battery, and typically a lithium-ion secondary battery. The lithium-ion secondary battery is a battery using lithium as a charge carrier, and may include, in addition to a lithium-ion secondary battery with a liquid electrolyte, an all-solid-state battery using a solid electrolyte. Also, the battery 40 may be any power storage device, and for example, a large-capacity capacitor or the like may be used instead of the battery 40.

[0026] The SMR50 switches the connection / disconnection of the power line from the battery 40 to the PCU20 in response to the control signal received from the ECU10. The SMR50 is closed (connected) when the vehicle 200 is running. The SMR50 is also closed when power is exchanged between the battery 40 and the inlet 210 (and consequently, the power stand 300). Furthermore, the SMR50 is closed when temperature rise control using ripple current, as described later, is performed.

[0027] Relay 60 is located between the charger / discharger 230 and the battery 40. Relay 60 switches the connection / disconnection of the power line (charge / discharge line) from the inlet 210 to the battery 40 according to the control signal received from the ECU 10.

[0028] In this embodiment, the charge / discharge line, passing through the inlet 210, the charge / discharge unit 230, and the relay 60, is connected to the power line connecting the SMR50 and the PCU20. That is, the charge / discharge line is connected to the SMR50 such that the charge / discharge unit 230 is in parallel with the PCU20. However, it is not limited to this, and the charge / discharge line may also be connected to the power line connecting the battery 40 and the SMR50. That is, the charge / discharge line may be connected to the battery 40 such that the charge / discharge unit 230 is in parallel with the SMR50.

[0029] In the plugged-in vehicle 200, external charging (i.e., charging of the battery 40 with power from the power station 300) and external discharging (i.e., discharging power from the battery 40 to the power station 300) are possible. Note that the vehicle 200 may only be capable of external charging. When external charging or external discharging is performed, the relay 60 is controlled to a closed state (connected state), and when neither external charging nor external discharging is performed, the relay 60 is controlled to an open state (disconnected state).

[0030] The PCU20 includes a circuit (for example, an inverter and a converter) that drives the MG220 using power supplied from the battery 40. The inverter and converter are configured, for example, by combining multiple switching elements and perform switching operations that convert power in response to control signals received from the ECU10, or switching operations that boost the voltage.

[0031] Vehicle 200 is further equipped with a cooling system for cooling the battery 40. The cooling system comprises refrigerant circuits C1 and C2 and a chiller 270. Refrigerant circuit C1 includes a heat exchanger 240, a reserve tank (R / T) 250, and a pump 260.

[0032] The heat exchanger 240 is located below the battery 40, and a thermal conductive material 42 is provided between the battery 40 and the heat exchanger 240. The thermal conductive material 42 is made of, for example, a silicone-based adhesive. The thermal conductive material 42 may also be, for example, a thermally conductive gel, grease, paste, or sheet that can be adhered to the battery 40 or the heat exchanger 240.

[0033] Pump 260 circulates refrigerant in refrigerant circuit C1. The refrigerant flowing through refrigerant circuit C1 cools the battery 40 when its temperature rises. The refrigerant includes, for example, coolant. If the temperature of the battery 40 is low due to weather or location (for example, a cold region), the temperature of the battery 40 may be raised by heating the refrigerant before it flows into the heat exchanger 240 adjacent to the battery 40 using a heater (not shown). Refrigerant circuit C2 includes a refrigeration cycle device 280. The refrigeration cycle device 280 includes various devices (for example, a compressor, condenser, expansion valve, and evaporator) (not shown) that adjust the temperature through a refrigeration cycle (a cycle of evaporation, compression, condensation, and expansion strokes). The cooling circuit of an air conditioning system (not shown) mounted on the vehicle 200 may constitute the refrigeration cycle device 280. The refrigerant flowing through refrigerant circuit C2 is cooled by the refrigeration cycle device 280. Chiller 270 is connected to refrigerant circuits C1 and C2, and performs heat exchange between the refrigerant circulating in refrigerant circuit C1 and the refrigerant circulating in refrigerant circuit C2.

[0034] In the vehicle 200 having the above configuration, a heat conductive material 42 is provided between the battery 40 and the heat exchanger 240. Due to a defect in the coating of this heat conductive material 42, peeling of the heat conductive material 42 may occur due to external impacts from driving on rough roads. If peeling occurs in the heat conductive material which is bonded to at least one of the battery 40 and the heat exchanger 240, it becomes impossible to adjust the battery 40 to an appropriate temperature. Since the condition of the heat conductive material 42 cannot be checked from outside the battery system 100, it is necessary to accurately determine whether or not peeling has occurred in the heat conductive material 42.

[0035] Therefore, in this embodiment, the ECU 10 calculates the thermal resistance k between the heat exchanger and the battery 40 using the temperature Tw (first temperature) of the refrigerant flowing into the heat exchanger 240, the temperature Tb (second temperature) of the battery 40, and the amount of heat exchanged in the heat exchanger 240 Q. If the calculated thermal resistance k is greater than the threshold k(0), the ECU 10 determines that the heat conductive material 42 is in an abnormal state. For example, the ECU 10 calculates the thermal resistance k by subtracting the temperature Tb from the temperature Tw and dividing the result by the amount of heat exchanged in the heat exchanger 240 Q. More specifically, the ECU 10 calculates the thermal resistance k using the formula k = (Tw - Tb) / Q.

[0036] In this way, if the thermal conductive material 42 peels off, the heat exchange between the battery 40 and the heat exchanger 240 will not be performed properly, and the amount of heat exchanged in the heat exchanger 240 Q will decrease, causing the value of the thermal resistance k to increase. Therefore, by determining that the thermal resistance k is greater than the threshold k(0), it is possible to accurately determine an abnormal state (i.e., a state in which the thermal conductive material 42 has peeled off).

[0037] The following describes an example of processing performed by ECU10, with reference to Figure 2. Figure 2 is a flowchart showing an example of processing performed by ECU10.

[0038] In step 100 (hereinafter referred to as S), the ECU 10 determines whether the execution conditions are met. The execution conditions may include, for example, the condition that the refrigerant circuit C1 shown in Figure 1 is formed, and the condition that charging or discharging is taking place. For example, the ECU 10 may determine that the refrigerant circuit C1 is formed when the operation of a switching valve (not shown) forms a refrigerant circuit including the heat exchanger 240, R / T 250, pump 260, and chiller 270 shown in Figure 1. Furthermore, the ECU 10 may determine that charging or discharging is taking place when the magnitude of the current is not zero. If it is determined that the execution conditions are met (YES in S100), the process moves to S102.

[0039] In S102, the ECU10 acquires temperatures Tb and Tw. The ECU10 acquires temperatures Tb and Tw using the battery temperature sensor 45 and the inlet temperature sensor 46. The process then moves to S104.

[0040] In S104, the ECU10 obtains the amount of heat exchanged in the chiller 270 over a predetermined period. The predetermined period is, for example, a period that is adapted by experimentation or other means depending on the accuracy of the calculation of the thermal resistance k. The amount of heat exchanged in the chiller 270 is obtained based on the operating state of the refrigeration cycle device 280 (for example, the operating amount of the compressor of the refrigeration cycle device 280, the temperature of the refrigerant flowing into the condenser, the temperature of the refrigerant flowing out of the chiller 270 from the evaporator, etc.). The ECU10 may, for example, obtain the amount of heat exchanged in the chiller 270 using a map or formula that shows the relationship between the operating state of the refrigeration cycle device 280 and the amount of heat exchanged in the chiller 270. The process then proceeds to S106.

[0041] In S106, the ECU 10 obtains the amount of heat generated by the battery 40 over a predetermined period. The predetermined period is the same as the predetermined period in the process of S104, so a detailed explanation will not be repeated. The ECU 10 obtains the amount of heat generated by the battery 40 using, for example, the amount of Joule heat generated and the amount of heat absorbed due to chemical changes over the predetermined period. The ECU 10 calculates the amount of Joule heat generated and the amount of heat absorbed due to chemical changes using, for example, the detection results of the voltage sensor 43, the current sensor 44, and the battery temperature sensor 45. The method for calculating the amount of Joule heat generated and the amount of heat absorbed due to chemical changes can be done using known techniques, and a detailed explanation will not be given. The process then moves to S108.

[0042] In S108, the ECU10 obtains the amount of heat exchanged in the heat exchanger 240 Q. Specifically, the ECU10 uses, for example, the table and map shown in Figure 3 to obtain the amount of heat exchanged in the heat exchanger 240 Q from the amount of heat exchanged in the chiller 270 (chiller heat exchange amount) obtained in S104 and the amount of heat exchanged in the battery 40 (battery heat generation amount) obtained in S106.

[0043] Figure 3 shows an example of the relationship between the heat generated by the battery, the heat exchanged by the chiller, and the heat exchanged by the heat exchanger 240, Q. The table in Figure 3 shows that when the chiller heat exchange rate is 1 kW, the heat exchanged by the heat exchanger 240 is 4 kW, 3 kW, 2 kW, and 1 kW when the heat generated by the battery is 1 kW, 2 kW, 3 kW, and 4 kW, respectively.

[0044] Furthermore, the table in Figure 3 shows that when the chiller heat exchange rate is 2 kW, the heat exchange rates in the heat exchanger 240 are 5 kW, 4 kW, 3 kW, and 2 kW, respectively, when the battery heat generation is 1 kW, 2 kW, 3 kW, and 4 kW.

[0045] Furthermore, the table in Figure 3 shows that when the chiller heat exchange rate is 3 kW, the heat exchange rates in the heat exchanger 240 are 5 kW, 5 kW, 4 kW, and 3 kW, respectively, when the battery heat generation is 1 kW, 2 kW, 3 kW, and 4 kW.

[0046] Furthermore, the table in Figure 3 shows that when the chiller heat exchange rate is 4 kW, the heat exchange rates in the heat exchanger 240 are 5 kW, 5 kW, 5 kW, and 4 kW, respectively, when the battery heat generation is 1 kW, 2 kW, 3 kW, and 4 kW.

[0047] For example, if the chiller heat exchange rate obtained in S104 is 2kW, the relationship between the battery heat output and the heat exchange rate Q in the heat exchanger 240 will be as shown in the thick-lined box in the table in Figure 3, and will be a linear relationship as shown in LN1 of Figure 3(A). The vertical axis of Figure 3(A) represents the heat exchange rate Q in the heat exchanger. The horizontal axis of Figure 3(A) represents the battery heat output. As shown in LN1 of Figure 3, for example, if the chiller heat exchange rate is 2kW and the battery heat output is 4kW, the heat exchange rate Q in the heat exchanger 240 is calculated as 2kW. The process then moves to S110.

[0048] In S110, ECU10 calculates the thermal resistance k. That is, ECU10 calculates the thermal resistance k using the formula k = (Tw - Tb) / Q mentioned above. The process then moves to S112.

[0049] In S112, the ECU 10 determines whether the thermal resistance k is greater than the threshold value k(0). The threshold value is a value that allows for the determination of whether delamination has occurred in the thermal conductive material 42, and is a value that is determined through experiments or other means. The threshold value k(0) may be a predetermined value, or it may be set according to the operating period of the vehicle 200, the total mileage, the history of outside temperatures, the type of material used for the thermal conductive material 42, etc. The process then proceeds to S114.

[0050] In S114, the ECU10 determines that delamination of the thermal conductive material 42 has occurred. The ECU10 may, for example, set a diagnostic flag indicating that the thermal conductive material 42 has delaminated to the ON state, or it may illuminate a predetermined warning light or notify the user that delamination has occurred. The process is then terminated. If it is determined that the execution conditions are not met (NO in S100), or if it is determined that the thermal resistance k is less than or equal to the threshold k(0) (NO in S112), the process is then terminated.

[0051] The operation of the ECU 10 based on the structure and flowchart described above will now be explained. For example, if the conditions that the battery 40 is charged and that a refrigerant circuit C1 including the heat exchanger 240, R / T 250, pump 260, and chiller 270 is formed are met, it is determined that the execution conditions are met (YES in S100). Therefore, the battery temperature and inlet temperature are obtained (S102). Subsequently, the chiller heat exchange amount is obtained (S104), and the battery heat generation amount is obtained (S106). The heat exchange amount Q in the heat exchanger 240 is obtained using the obtained chiller heat exchange amount, battery heat generation amount, and the table in Figure 3 (S108). Then, the thermal resistance k is calculated using the formula k=(Tw-Tb) / Q (S110). If the calculated thermal resistance k is determined to be greater than the threshold k(0) (YES in S112), it is determined that peeling of the thermal conductive material 42 has occurred (S114). On the other hand, if it is determined that the thermal resistance k is less than or equal to the threshold k(0) (NO in S112), the system waits until the next execution condition is met.

[0052] As described above, according to the battery system 100 of this embodiment, if the heat conductive material 42 peels off, heat exchange between the battery 40 and the heat exchanger 240 will not be performed properly, and the value of the heat exchange amount Q in the heat exchanger 240 will decrease, causing the value of the thermal resistance k to increase. Therefore, by determining that peeling of the heat conductive material 42 has occurred when the thermal resistance k is greater than the threshold k(0), it is possible to accurately determine an abnormal state (i.e., a state in which the heat conductive material 42 has peeled off). Thus, it is possible to provide a battery system that can accurately determine whether or not peeling of the heat conductive material has occurred.

[0053] Furthermore, since the amount of heat exchanged in the heat exchanger is calculated using a map that shows the relationship between the heat generated by the battery 40, the amount of heat exchanged in the chiller 270, and the amount of heat exchanged in the heat exchanger 240 Q, the amount of heat exchanged in the heat exchanger can be calculated with high accuracy.

[0054] Furthermore, by calculating the thermal resistance k using the formula k=(Tw-Tb) / Q, it is possible to accurately determine whether or not heat exchange between the battery 40 and the heat exchanger 240 is being performed properly.

[0055] The following describes variations. In the above-described embodiment, the abnormal state in which the heat conductive material 42 peels off was described assuming, for example, a state in which the entire surface of the heat conductive material 42 is peeled off from at least one of the battery 40 and the heat exchanger 240 (a state in which it is not adhered). However, the abnormal state may be determined in multiple stages by setting multiple threshold values ​​for the thermal resistance k corresponding to an abnormal state in which only a part has peeled off.

[0056] Furthermore, although the above-described embodiment explained that the battery temperature sensor 45 is provided on the battery 40, the ECU 10 may, for example, correct the detection result of the battery temperature sensor 45 according to the position on the battery 40 where the battery temperature sensor 45 is provided. For example, the ECU 10 may correct the detection result of the battery temperature sensor 45 to the temperature of the part of the battery 40 that is close to the contact surface with the thermal conductive material 42. In this way, the amount of heat generated by the battery can be calculated with high accuracy, and the thermal resistance k can be determined with high accuracy. As a result, it is possible to determine with high accuracy whether or not peeling of the thermal conductive material 42 has occurred.

[0057] Furthermore, although the above embodiment was described as calculating the thermal resistance k using the formula k=(Tw-Tb) / Q, the thermal resistance k may also be calculated by dividing the magnitude of the temperature difference between Tw and Tb by the amount of heat exchanged in the heat exchanger 240 Q, or the thermal resistance k may be calculated when the inlet water temperature is greater than the battery temperature.

[0058] Furthermore, in the above-described embodiment, it was explained that peeling of the thermal conductive material 42 is determined when the thermal resistance k is greater than the threshold k(0). However, for example, it may be determined that the thermal conductive material 42 has not peeled from either the heat exchanger 240 or the battery 40 when the thermal resistance k is less than or equal to the threshold k(0).

[0059] Furthermore, the above-mentioned modifications may be implemented by combining all or part of them as appropriate. The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0060] 10 ECU, 11 Processor, 12 RAM, 13 Memory, 20 PCU, 40 Battery, 42 Thermal Conductor, 43 Voltage Sensor, 44 Current Sensor, 45 Battery Temperature Sensor, 46 Inlet Temperature Sensor, 50 SMR, 60 Relay, 100 Battery System, 200 Vehicle, 210 Inlet, 230 Charger / Discharger, 240 Heat Exchanger, 250 Reserve Tank (R / T), 260 Pump, 270 Chiller, 280 Refrigeration Cycle Equipment, 300 Power Stand, 310 Cable, 311 Connector, PG Power System.

Claims

1. Energy storage device, A heat exchanger that performs heat exchange with the energy storage device using a refrigerant, A heat conductive material is provided between the energy storage device and the heat exchanger, A first detection device for detecting a first temperature, which is the temperature of the refrigerant flowing into the heat exchanger, A second detection device for detecting a second temperature, which is the temperature of the energy storage device, The system includes a control device that calculates the thermal resistance between the heat exchanger and the energy storage device by dividing the value obtained by subtracting the second temperature from the first temperature by the amount of heat exchanged in the heat exchanger, The control device determines that the thermal conductive material is in an abnormal state if the calculated thermal resistance is greater than a threshold value, in a battery system.

2. The heat exchanger is connected to the chiller, The battery system according to claim 1, wherein the control device calculates the amount of heat exchange in the heat exchanger using a predetermined relationship between the amount of heat generated by the energy storage device, the amount of heat exchange in the chiller, and the amount of heat exchange in the heat exchanger.

3. The battery system according to claim 1 or 2, wherein the control device determines that the thermal resistance is greater than the threshold value, and that the thermal conductive material has detached from at least one of the heat exchanger and the energy storage device, is an abnormal state.

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