Battery thermal resistance measuring system and method

Abstract

The embodiment of the invention discloses a battery thermal resistance measuring system and method. The system comprises battery sample equipment, a constant-temperature environment box, battery testing equipment, temperature acquisition equipment and computing equipment, the battery sample equipment is used for loading a to-be-tested battery; the constant-temperature environment box is used for loading battery sample equipment and providing a constant-temperature environment for the battery sample equipment; the battery test equipment is connected with the to-be-tested battery and is used for acquiring charging and discharging parameters of the to-be-tested battery; the temperature acquisition equipment is connected with the to-be-tested battery and is used for testing the temperature of the to-be-tested battery; the calculation device is connected with the battery test device and the temperature acquisition device and is used for calculating the thermal resistance of the to-be-tested battery based on the charging and discharging parameters of the to-be-tested battery and the temperature of the to-be-tested battery. By using the system, rapid and accurate detection of the thermal resistance of the battery can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of battery detection, and in particular to a battery thermal resistance measurement system and method. Background Art

[0002] As the structure of batteries becomes more and more complex, the thermal conductivity and dimensional parameters of their various component materials are difficult to accurately determine, and the heat generation and heat transfer capabilities of different areas on the battery are different, making it difficult to accurately measure the thermal resistance of the battery. It is urgent to establish a test system to measure the thermal resistance of batteries with different designs. Summary of the invention

[0003] The embodiments of the present invention provide a battery thermal resistance measurement system and method, which can achieve rapid and accurate measurement of the thermal resistance of the battery.

[0004] In a first aspect, the present application provides a battery thermal resistance measurement system, the system comprising: a battery sample device, a constant temperature environment box, a battery testing device, a temperature acquisition device and a computing device; the battery sample device is used to load a battery to be tested; the constant temperature environment box is used to load the battery sample device and provide a constant temperature environment for the battery sample device; the battery testing device is connected to the battery to be tested, and is used to obtain the charge and discharge parameters of the battery to be tested; the temperature acquisition device is connected to the battery to be tested, and is used to test the temperature of the battery to be tested; the computing device is connected to the battery testing device and the temperature acquisition device, and is used to receive the charge and discharge parameters of the battery to be tested sent by the battery testing device, and receive the temperature of the battery to be tested sent by the temperature acquisition device; the computing device is also used to calculate the thermal resistance of the battery to be tested based on the charge and discharge parameters of the battery to be tested and the temperature of the battery to be tested.

[0005] It can be seen that the above system only needs to test the charge and discharge parameters and temperature of the battery to be tested to calculate the thermal resistance of the battery to be tested. The operation is simple, so the rapid detection of the thermal resistance of the battery can be achieved. In addition, the above system uses a battery sample device to directly load the battery to be tested for charge and discharge simulation testing. It can not only accurately measure the charge and discharge parameters of the battery to be tested, but also directly load the battery to be tested without changing the structure of the battery to be tested. Therefore, it will not affect the heat transfer path of the battery to be tested itself. The measured temperature of the battery to be tested is also relatively accurate, so that the thermal resistance of the battery to be tested calculated based on the charge and discharge parameters and temperature of the battery to be tested is also relatively accurate.

[0006] Furthermore, since the above-mentioned system does not change the structure of the battery to be tested when testing the thermal resistance of the battery to be tested, in the scenario where the resistance of the battery to be tested needs to be tested multiple times to reduce the test error, the above-mentioned system can test the same battery to be tested multiple times to obtain multiple test thermal resistances with high repeatability. This is unlike some existing technologies that destroy the structure of the battery to be tested when testing the thermal resistance of the battery to be tested, resulting in a failure to repeatedly test the same battery to be tested.

[0007] In a possible implementation of the first aspect, the battery sample device includes a metal cold plate and insulating foam, the metal cold plate is in contact with the battery to be tested, and the remaining surface of the battery to be tested except the contact surface is covered with the insulating foam; the metal cold plate is used to absorb heat emitted by the battery to be tested.

[0008] In the above scheme, a metal cold plate and insulating foam are set in the battery sample device, the metal cold plate is set to contact the battery to be tested, and the remaining surface of the battery to be tested except the contact surface is set to be covered with insulating foam, which is used to simulate the cooling system inside the battery pack to be tested and improve the reliability and accuracy of the temperature data collected by the temperature acquisition device. Since the collected temperature data will be used to calculate the thermal resistance of the battery to be tested, it will also indirectly improve the reliability and accuracy of the thermal resistance calculation of the above system.

[0009] In a possible implementation manner of the first aspect, the battery sample device further includes a thermally conductive adhesive, and the thermally conductive adhesive is coated on a contact surface between the metal cold plate and the battery to be tested.

[0010] The purpose of the thermal conductive adhesive applied between the metal cold plate and the battery to be tested is to ensure that the heat generated by the battery to be tested can be quickly transferred to the metal cold plate along the contact surface between the battery and the metal cold plate. In some practical application scenarios, the contact between the battery to be tested and the metal cold plate is not tight. At this time, the heat generated by the battery to be tested cannot be transferred to the metal cold plate in time. The thermal conductive adhesive applied here can tightly connect the battery to be tested and the metal cold plate. At the same time, the high thermal conductivity of the thermal conductive adhesive can be used to quickly transfer the heat generated by the battery to be tested to the metal cold plate through the thermal conductive adhesive. This can ensure the reliability and accuracy of the temperature data of the battery to be tested collected by the subsequent temperature acquisition equipment, thereby improving the reliability and accuracy of the thermal resistance of the battery to be tested calculated based on the temperature data.

[0011] In addition, in the above system, since the heat generated by the battery to be tested during the charge and discharge test can be transmitted to the metal cold plate in time, it can also prevent the battery to be tested from being damaged due to excessive temperature when using the above battery thermal resistance system, and thus the above system cannot be used to perform multiple measurements on the battery to be tested, resulting in poor repeatability.

[0012] In a possible implementation of the first aspect, the thickness of the thermally conductive adhesive is greater than or equal to 0.1 mm and less than or equal to 2 mm, and the thermal conductivity of the thermally conductive adhesive is greater than or equal to 0.5 watts per meter·Kelvin and less than or equal to 5 watts per meter·Kelvin.

[0013] In the above scheme, in the battery sample equipment of the present application, there are requirements for the thickness and thermal conductivity of the thermal conductive adhesive between the battery to be tested and the metal cold plate. The reasonable selection of the thickness and thermal conductivity of the thermal conductive adhesive is the prerequisite for the battery thermal resistance measurement system provided by the present application to accurately measure the thermal resistance of the battery to be tested.

[0014] In the battery thermal resistance measurement system provided in this application, the thickness of the thermal conductive adhesive is between 0.1 mm and 2 mm. If the thermal conductive adhesive is too thin, its thermal conductivity will be insufficient. At this time, the thermal conductive adhesive cannot effectively transfer the heat of the battery to be tested. The heat generated by the battery to be tested cannot be quickly transferred from the contact surface of the battery to the metal cold plate, thereby affecting the accuracy of the subsequent collected temperature data. At the same time, when the thermal conductive adhesive is too thin, it is easily affected by machine stress and temperature changes, resulting in failure. When the thermal conductive adhesive is too thick, since the heat of the battery to be tested needs to travel a longer distance to reach the metal cold plate, it will also lead to insufficient heat transfer capacity. At the same time, when the thermal conductive adhesive is too thick, the contact surface bonded with the battery to be tested will promote the accumulation of machine stress, and there will be a risk of damaging the battery to be tested.

[0015] In the battery thermal resistance measurement system provided in the present application, the thermal conductivity of the thermal conductive adhesive is between 0.5 watts per meter Kelvin and 5 watts per meter Kelvin. When the thermal conductivity of the thermal conductive adhesive is too high, it will cause the heat to be transferred too quickly, so that the heat generated by the battery to be tested cannot be evenly distributed, resulting in the temperature of some areas being much higher than that of the surrounding areas, or the temperature of some areas being much lower than that of the surrounding areas, all of which will affect the accuracy of the subsequent temperature data collected. When the thermal conductivity of the thermal conductive adhesive is too low, the heat generated by the battery to be tested cannot be quickly transferred from the contact surface of the battery to the metal cold plate due to the insufficient thermal conductivity of the thermal conductive adhesive, which will also affect the accuracy of the subsequent temperature data collected.

[0016] In a possible implementation of the first aspect, the charging and discharging parameters include: a charging current I cell , discharge current Charging voltage U cell , discharge voltage Open circuit voltage U when not charged oc , open circuit voltage when not discharged Charging time t1 and discharging time t2;

[0017] The calculation device is specifically used to calculate the thermal resistance R of the battery to be tested by the following formula th :

[0018]

[0019] R th =(T2-T1) / HGP

[0020] in, represents the temperature entropy coefficient of the battery to be tested, HGP represents the heat generation power of the battery to be tested, T represents the average value of the highest temperature among the temperatures of multiple points on the battery to be tested and the temperature of the constant temperature environment box, and T2 and T1 represent the temperatures of any two points among the multiple points.

[0021] The above formula calculates the heat generation power of the battery to be tested first and then calculates the thermal resistance between any two points based on the temperature difference between the two points. cell , discharge current Charging voltage U cell , discharge voltage Open circuit voltage U when not charged oc , open circuit voltage when not discharged The charging time t1 and the discharging time t2 can be obtained by the battery testing equipment in the battery thermal resistance measurement system when the battery to be tested is charged and discharged. It is an inherent property of the battery under test and can be obtained by drawing the state of charge-open circuit voltage curve of the battery under test at different temperatures. The maximum temperature of the battery under test and the average temperature T of the constant temperature environment box, and the temperatures T2 and T1 between any two points that need to be measured in the battery under test are all obtained by the temperature acquisition device when the battery under test is charged and discharged.

[0022] Through the above formula and the battery thermal resistance measurement system provided in the present application, the thermal resistance between any two points on the battery to be tested can be measured, and each parameter used in the above formula can be measured multiple times and observed in real time. At the same time, the structure or properties of the battery to be tested will not be affected in the process of obtaining each parameter, and the thermal resistance of the same battery to be tested can be measured repeatedly.

[0023] In a possible implementation of the first aspect, the charging and discharging parameters include: charging power Q chg 、Discharge capacity Q dch , charging time t1 and discharging time t2;

[0024] The calculation device is specifically used to calculate the thermal resistance R of the battery to be tested by the following formula th :

[0025] HGP=(Q chg -Q dch ) / (t1+t2)

[0026] Rth =(T2-T1) / HGP

[0027] Wherein, HGP represents the heat generation power of the battery to be tested, and T2 and T1 represent the temperatures of any two points on the battery to be tested.

[0028] In a second aspect, the present application provides a method for measuring thermal resistance of a battery, which is applied to a battery thermal resistance measurement system, wherein the system comprises: a battery sample device, a constant temperature environment box, a battery testing device, a temperature acquisition device and a computing device; the battery sample device is used to load a battery to be tested; the constant temperature environment box is used to load the battery sample device; the battery testing device is connected to the battery to be tested; the temperature acquisition device is connected to the battery to be tested; the computing device is connected to the battery testing device and the temperature acquisition device;

[0029] The method includes: the battery testing equipment acquires the charge and discharge parameters of the battery to be tested, wherein the battery to be tested is located in a constant temperature environment provided by the constant temperature environment box; the temperature acquisition equipment tests the temperature of the battery to be tested; the computing equipment receives the charge and discharge parameters of the battery to be tested sent by the battery testing equipment, and receives the temperature of the battery to be tested sent by the temperature acquisition equipment; the computing equipment calculates the thermal resistance of the battery to be tested based on the charge and discharge parameters of the battery to be tested and the temperature of the battery to be tested.

[0030] In a possible implementation of the second aspect, the battery sample device includes a metal cold plate and insulating foam, the metal cold plate contacts the battery to be tested, and the remaining surface of the battery to be tested except the contact surface is covered with the insulating foam; the metal cold plate is used to absorb heat emitted by the battery to be tested.

[0031] In a possible implementation manner of the second aspect, the battery sample device further includes a thermally conductive adhesive, and the thermally conductive adhesive is coated on a contact surface between the metal cold plate and the battery to be tested.

[0032] In a possible implementation of the second aspect, the thickness of the thermally conductive adhesive is greater than or equal to 0.1 mm and less than or equal to 2 mm, and the thermal conductivity of the thermally conductive adhesive is greater than or equal to 0.5 watts per meter·Kelvin and less than or equal to 5 watts per meter·Kelvin.

[0033] In a possible implementation of the second aspect, the charging and discharging parameters include: a charging current I cell , discharge current Charging voltage U cell , discharge voltage Open circuit voltage U when not charged oc , open circuit voltage when not discharged Charging time t1 and discharging time t2;

[0034] The calculation device can calculate the thermal resistance R of the battery to be tested based on the charge and discharge parameters of the battery to be tested and the temperature of the battery to be tested by the following formula: th :

[0035]

[0036] R th =(T2-T1) / HGP

[0037] in, represents the temperature entropy coefficient of the battery to be tested, HGP represents the heat generation power of the battery to be tested, T represents the average value of the highest temperature among the temperatures of multiple points on the battery to be tested and the temperature of the constant temperature environment box, and T2 and T1 represent the temperatures of any two points among the multiple points.

[0038] In a possible implementation of the second aspect, the charging and discharging parameters include: charging power Q chg 、Discharge capacity Q dch , charging time t1 and discharging time t2;

[0039] The calculation device can also calculate the thermal resistance R of the battery to be tested based on the charge and discharge parameters of the battery to be tested and the temperature of the battery to be tested by the following formula: th :

[0040] HGP=(Q chg -Q dch ) / (t1+t2)

[0041] R th =(T2-T1) / HGP

[0042] Wherein, HGP represents the heat generation power of the battery to be tested, and T2 and T1 represent the temperatures of any two points on the battery to be tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the background technology, the drawings required for use in the embodiments of the present invention or the background technology will be described below.

[0044] Figure 1 It is a schematic diagram of the composition of a battery thermal resistance measurement system provided in an embodiment of the present application;

[0045] Figure 2 is a schematic diagram of a battery thermal resistance measurement system provided in an embodiment of the present application;

[0046] Figure 3This is a schematic diagram of the positions of key temperature sampling points in a battery thermal resistance measurement provided in an embodiment of the present application;

[0047] Figure 4 This is a schematic diagram of the location of temperature sampling points on the battery surface in a battery thermal resistance measurement provided in an embodiment of the present application;

[0048] Figure 5 This is a schematic diagram of the location of temperature sampling points inside a battery in a battery thermal resistance measurement provided in an embodiment of the present application;

[0049] Figure 6 It is a temperature variation curve diagram of each temperature sampling point in a battery thermal resistance measurement provided in an embodiment of the present application;

[0050] Figure 7 It is a flow chart of a battery thermal resistance measurement method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0052] The terms "including" and "having" and any variations thereof in the specification and claims of the present application and the above drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device comprising a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products or devices.

[0053] It should be noted that the terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms of "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0054] Before introducing the battery thermal resistance measurement system and method provided by the present application, a brief introduction to the background of the present application is first given.

[0055] The battery will lose energy during the charging and discharging process. Part of the electrical energy is converted into heat energy and causes the battery temperature to rise. Since the heat generation capacity, thermal conductivity, specific heat capacity, etc. of various regions in the battery are different, the temperature of each part of the battery is also different. Higher temperatures will affect the service life of the battery, and more raw material costs will be required to meet the available energy and power needs during the battery life cycle. In addition, the temperature difference within the battery will also affect the consistency of the current density in the battery and affect the long-term performance of the battery.

[0056] At present, the general method to solve the above problems is to optimize the comprehensive performance of the battery, regulate the temperature rise and temperature difference of the battery cell, and reasonably match and optimize the cooling system. When optimizing battery performance, it is necessary to repeatedly compare the temperature rise and temperature difference of the battery under different designs. Due to the relatively complex internal structure of the battery, the thermal conductivity and dimensional parameters of its various component materials are also difficult to confirm, and the measurement cycle using traditional methods is long. Nowadays, there is an urgent need to establish a fast, repeatable, and reproducible test system and method to measure the temperature rise and temperature difference of batteries under different designs.

[0057] Among the thermal physical parameters of the battery, thermal resistance can be used to reflect the temperature rise and temperature difference of the battery under different designs and cooling methods. The lower the thermal resistance value, the stronger the heat dissipation ability of the battery, and the smaller the temperature rise and temperature difference. Therefore, the embodiment of the present application provides a fast, repeatable and reproducible battery thermal resistance measurement system and method, which uses the measured battery thermal resistance to reflect the temperature rise and temperature difference of the battery.

[0058] See also Figure 1 , Figure 1 Schematic diagram of a battery thermal resistance measurement system provided in an embodiment of the present application. Figure 1 As shown, the battery thermal resistance measurement system 100 mainly includes a battery sample device 101 , a constant temperature environment box 102 , a battery testing device 103 , a temperature acquisition device 104 and a computing device 105 .

[0059] The battery sample device 101 is used to load the battery to be tested and is located inside the constant temperature environment box 102 .

[0060] The constant temperature environment box 102 is used to load the battery sample device 101 and provide a constant temperature environment for the battery sample device 101 .

[0061] The battery testing device 103 is connected to the battery to be tested and is used to obtain the charging and discharging parameters of the battery to be tested.

[0062] The temperature acquisition device 104 is connected to the battery to be tested and is used to obtain the temperature of the battery to be tested.

[0063] The computing device 105 is connected to the battery testing device 103 and the temperature acquisition device 104, and is used to receive the charge and discharge parameters of the battery to be tested sent by the battery testing device 103, and receive the temperature of the battery to be tested sent by the temperature acquisition device 104, and calculate the thermal resistance of the battery to be tested based on the charge and discharge parameters of the battery to be tested and the temperature of the battery to be tested.

[0064] The communication mode between the computing device 105 and the battery testing device 103 and the temperature acquisition device 104 may be wired or wireless. In the wireless mode, after obtaining corresponding data, the battery testing device 103 and the temperature acquisition device 104 may send the data to the computing device 105 via network transmission. After receiving the data sent by the battery testing device 103 and the temperature acquisition device 104, the computing device 105 calculates the thermal resistance of the battery to be tested.

[0065] When using the battery thermal resistance measurement system 100 to test the thermal resistance of a battery to be tested, the battery to be tested needs to be adjusted to the charge state to be tested first, and then the battery to be tested is placed in the battery sample device 101, and connected to the battery test device 103 and the temperature acquisition device 104. The temperature acquisition device 104 will obtain the temperature data of the battery to be tested. After the temperature acquisition device 104 determines that the temperature of the battery to be tested is stable to the temperature in the constant temperature environment box 102, the battery test device 103 is used to perform a charge and discharge test on the battery to be tested. The battery test device 103 will record the charge and discharge parameters such as the voltage and current of the battery to be tested during charge and discharge. At the same time, the temperature acquisition device 104 will record the charge and discharge of the battery to be tested. Temperature data during the electrical test. After the charge and discharge test is completed, the battery testing device 103 will send the collected charge and discharge parameters such as voltage and current to the computing device 105, and the temperature acquisition device 104 will send the collected temperature data to the computing device 105. After receiving the charge and discharge parameters such as voltage and current and the temperature data, the computing device 105 will extract the charging voltage and discharge voltage, charging current and discharge current and other parameters of the battery to be tested when its surface temperature tends to be stable, and extract the temperature of any two points of the battery to be tested when its surface temperature tends to be stable. Finally, the thermal resistance between the above-mentioned any two points is calculated by the extracted data, and the thermal resistance is the thermal resistance of the battery to be tested.

[0066] It can be seen that the battery thermal resistance measurement system 100 only needs to test the charge and discharge parameters and temperature of the battery to be tested to calculate the thermal resistance of the battery to be tested, and the operation is simple, so the rapid detection of the battery thermal resistance can be achieved. In addition, the battery thermal resistance measurement system 100 uses a battery sample device to directly load the battery to be tested for charge and discharge simulation testing, which can not only accurately measure the charge and discharge parameters of the battery to be tested, but also directly load the battery to be tested without changing the structure of the battery to be tested, so it will not affect the heat transfer path of the battery to be tested itself, and the measured temperature of the battery to be tested is also relatively accurate, so that the thermal resistance of the battery to be tested calculated based on the charge and discharge parameters and temperature of the battery to be tested is also relatively accurate.

[0067] Furthermore, since the battery thermal resistance measurement system 100 does not change the structure of the battery to be tested when testing the thermal resistance of the battery to be tested, in a scenario where the resistance of the battery to be tested needs to be tested multiple times to reduce the test error, the battery thermal resistance measurement system 100 can test the same battery to be tested multiple times to obtain multiple test thermal resistances with high repeatability, unlike some prior arts that, when testing the thermal resistance of the battery to be tested, the structure of the battery to be tested is destroyed, resulting in a failure to repeatedly test the same battery to be tested.

[0068] The following will specifically introduce the various components in the above-mentioned battery thermal resistance measurement system, and introduce the role of each component in measuring the battery thermal resistance.

[0069] See also Figure 2 , Figure 2 is a detailed structural diagram of a battery thermal resistance measurement system provided in an embodiment of the present application,

[0070] Figure 1 The battery sample device 101 shown may include Figure 2 The heat insulating foam 6, the heat conductive adhesive 8, the metal cold plate 9 and the bracket 10, Figure 1 The constant temperature environment box 102 shown is Figure 2 The constant temperature environment box 4, Figure 1 The battery testing equipment 103 shown may include Figure 2 Battery test cabinet 1, connecting wire 3, Figure 1 The temperature acquisition device 104 shown may include Figure 2 Thermocouple 7 and data logger 11, Figure 1 The computing device 105 shown is Figure 2 Computer 2 in. Figure 2 The serial number 5 shown indicates the battery to be tested.

[0071] The specific connection method of each component in the battery sample device 101 is as follows: first, the surface of the battery 5 to be tested is divided into an observation surface and a non-observation surface. Figure 2Taking the battery in as an example, the bottom of the battery 5 to be tested is defined as the observation surface, and the other surfaces are defined as non-observation surfaces. A metal cold plate 9 is placed on the observation surface of the battery 5 to be tested, and a thermally conductive adhesive 8 is evenly coated between the observation surface of the battery 5 to be tested and the metal cold plate 9. Finally, the battery 5 to be tested, the thermally conductive adhesive 8 and the metal cold plate 9 are placed inside the constant temperature environment box 4 using a bracket 10. The thermally conductive adhesive 8 evenly coated between the battery 5 to be tested and the metal cold plate 9 provides a fixed heat transfer flow direction for the battery 5 to be tested. When measuring the thermal resistance of the battery, the present application uses a metal cold plate 9 to simulate the cooling device in the battery pack when the battery 5 to be tested is working, and uses thermally conductive adhesive 8 to ensure that the heat generated by the battery 5 to be tested can be quickly transferred to the metal cold plate 9 along the observation surface of the battery 5 to be tested. When there are multiple batteries to be tested, multiple similar battery sample devices 101 can be constructed to load multiple batteries to be tested.

[0072] The battery 5 to be tested can be a square battery, an aluminum shell, a cylindrical or soft-pack lithium-ion battery, or a sodium-ion battery, etc. This application does not specifically limit the type of the battery 5 to be tested. In the following embodiments, the battery 5 to be tested is a square battery as an example for description.

[0073] It should be noted that Figure 2 In the example, the observation surface of the battery 5 to be tested is taken as the bottom surface of the battery. In a specific implementation, the observation surface of the battery 5 to be tested can be any surface of the battery 5 to be tested.

[0074] The above-mentioned metal cold plate 9 and the insulating foam 6 are used to simulate the heat flow inside the battery 5 to be tested, wherein the metal cold plate 9 can be a liquid cold plate containing coolant, a fin, a metal plate, etc., and the present application does not make specific limitations on this. In the battery sample device 101, it is mainly used as a cooling device in the battery pack to absorb the heat generated by the battery 5 to be tested. The insulating foam 6 is used to prevent the battery 5 to be tested from transmitting heat to other directions except the metal cold plate 9. Since it is necessary to ensure that the heat generated by the battery 5 to be tested flows in a directional manner to the metal cold plate 9 when using the above-mentioned battery 5 thermal resistance measurement system to measure the thermal resistance of the battery 5 to be tested, it is necessary to wrap the insulating foam 6 on all surfaces other than the contact surface between the battery 5 to be tested and the metal cold plate 9 to ensure that the other surfaces of the battery 5 to be tested will not transmit heat to the outside, thereby improving the reliability and accuracy of the temperature data collected by the temperature acquisition device 104. Since the temperature data will be used to calculate the thermal resistance of the battery 5 to be tested, the reliability and accuracy of the thermal resistance of the battery 5 to be tested calculated by the above-mentioned system will also be improved.

[0075] The function of the thermal conductive glue 8 coated between the metal cold plate 9 and the battery to be tested 5 is to ensure that the heat generated by the battery to be tested 5 can be quickly transferred to the metal cold plate 9 along the contact surface between the battery and the metal cold plate 9. In some practical application scenarios, the contact between the battery to be tested 5 and the metal cold plate 9 is not tight, and the heat generated by the battery to be tested 5 cannot be timely transferred to the metal cold plate 9. The thermal conductive glue 8 coated here can tightly connect the battery to be tested and the metal cold plate 9. At the same time, the high thermal conductivity of the thermal conductive glue 8 is utilized to enable the heat generated by the battery to be tested 5 to be quickly transferred to the metal cold plate 9 through the thermal conductive glue 8, ensuring that most of the heat is transferred to the non-metal cold plate 9. Adding the thermal conductive glue 8 to the battery sample device 101 not only ensures the reliability of the temperature data collected subsequently, but also prevents the battery to be tested 5 from being damaged due to excessive temperature when using the above-mentioned battery thermal resistance system, because the heat generated by the battery to be tested 5 during the charge and discharge test can be timely transferred to the metal cold plate 9.

[0076] The thickness and thermal conductivity of the thermally conductive adhesive 8 are also within certain ranges. To ensure that the heat generated by the battery 5 to be tested can be quickly transferred to the metal cold plate 9, in some possible embodiments, the thickness of the thermally conductive adhesive 8 is within the range of 0.1-2.0 mm, and the thermal conductivity of the thermally conductive adhesive 8 is within the range of 0.5-5.0 W / m*K. After applying the thermally conductive adhesive 8 between the battery 5 to be tested and the metal cold plate 9, appropriate force should be applied to fix the battery 5 to be tested on the top of the thermally conductive adhesive 8 to ensure good contact between the battery 5 to be tested and the thermally conductive adhesive 8.

[0077] In the battery sample device 101 provided in the embodiment of the present application, the thickness of the thermal conductive glue 8 is between 0.1 mm and 2 mm. If the thermal conductive glue 8 is too thin, it will lead to insufficient heat conduction capacity. At this time, the thermal conductive glue 8 cannot effectively transfer the heat of the battery 5 to be tested. The heat generated by the battery 5 to be tested cannot be quickly transferred from the contact surface of the battery to the metal cold plate 9, thereby affecting the accuracy of the subsequent collected temperature data. At the same time, when the thermal conductive glue 8 is too thin, it is easily affected by machine stress and temperature changes, resulting in failure. When the thermal conductive glue 8 is too thick, since the heat of the battery 5 to be tested needs to travel a longer distance to reach the metal cold plate 9, it will also lead to insufficient heat transfer capacity. At the same time, when the thermal conductive glue 8 is too thick, the contact surface bonded with the battery 5 to be tested will promote the accumulation of machine stress, and there is a risk of damaging the battery 5 to be tested.

[0078] In the battery sample device 101 provided in the embodiment of the present application, the thermal conductivity of the thermally conductive adhesive 8 is between 0.5 watts per meter·Kelvin and 5 watts per meter·Kelvin. When the thermal conductivity of the thermally conductive adhesive 8 is too high, it will cause the heat to be transferred too quickly, so that the heat generated by the battery 5 to be tested cannot be evenly distributed, resulting in the temperature of some areas being much higher than that of the surrounding areas, or the temperature of some areas being much lower than that of the surrounding areas, all of which will affect the accuracy of the temperature data collected subsequently. When the thermal conductivity of the thermally conductive adhesive 8 is too low, at this time, due to the insufficient thermal conductivity of the thermally conductive adhesive 8, the heat generated by the battery 5 to be tested cannot be quickly transferred from the contact surface of the battery to the metal cold plate 9, which will also affect the accuracy of the temperature data collected subsequently.

[0079] The main function of the constant temperature environment box 4 is to load the above-mentioned battery sample device 101 and keep the temperature inside the box constant, thereby improving the accuracy of the temperature data collected by the data collector 11.

[0080] The battery testing equipment 103 includes a battery testing cabinet 1 connecting line 3. The specific connection method is that the battery testing cabinet 1 is connected to a computer 2 for control, and then the battery testing cabinet 1 is connected to the positive and negative electrodes of the battery 5 to be tested through the connecting line 3. Here, the battery testing cabinet 1 can not only perform charge and discharge tests on the battery 5 to be tested, but also obtain the charge and discharge parameters of the battery 5 to be tested during operation, including voltage, current, etc., and can also send the obtained charge and discharge parameters to the computer 2.

[0081] The computer 2 can not only control the battery test cabinet 1 and control the charging and discharging voltage and current for testing the battery 5, but also receive data related to the battery 5 sent by the battery test cabinet 1 and the data acquisition device 11, and calculate the thermal resistance of the battery 5 based on the received data.

[0082] The data collected by the battery test cabinet 1 and the data collector 11 may include: the voltage, current, time, temperature of the battery 5 to be tested during charging and discharging, and the open circuit voltage of the battery 5 to be tested during charging and discharging.

[0083] In some possible embodiments, the computer 2 may calculate the thermal resistance of the battery 5 to be tested by using the following formula 1 and formula 2.

[0084]

[0085] In formula 1, I cell and are respectively the charging current and discharging current of the battery 5 to be tested, U cell and are respectively the charging voltage and discharging voltage of the battery 5 to be tested, U oc and are the open circuit voltages of the battery 5 under test during the charge test and the discharge test, t1 and t2 are the time of the charge test and the discharge test of the battery 5 under test, T is the average value of the maximum temperature of the battery 5 under test and the temperature of the constant temperature environment box 4, dU oc / dT is the temperature entropy coefficient of the battery 5 to be tested, and HGP is the heat generation power of the battery 5 to be tested.

[0086] Among them, I cell and U cell and U oc and Both t1 and t2 can be obtained by the battery testing device 103 when the battery 5 to be tested is subjected to a charge and discharge test. T can be obtained by drawing a temperature change curve using the temperature data obtained by the temperature acquisition device 104. It is the temperature entropy coefficient of a chemical energy storage battery at different charge states at a certain temperature. The temperature entropy coefficient can be obtained by plotting the charge state and open circuit voltage curve of the battery 5 to be tested at the test temperature by a computer.

[0087] The temperature T is the average value calculated by the maximum temperature of the battery 5 to be tested and the temperature of the constant temperature environment box 4 obtained by the temperature acquisition device 104. The specific process of obtaining the temperature T can refer to the following Figure 6 The relevant description will not be described in detail here.

[0088] After obtaining the HGP of the battery, the thermal resistance calculation of the battery 5 to be tested is completed using Formula 2.

[0089] R th =T2-T1 / HGP Formula 2

[0090] Wherein, T2 and T1 are the temperatures of any two points on the battery 5 to be tested.

[0091] In some possible embodiments, the charge and discharge test of the battery 5 to be tested is a constant current pulse cycle test. At this time, since the current and time of charging and discharging are the same, the heat generation power HGP of the battery 5 to be tested can also be calculated by Formula 3:

[0092] HGP=P loss =(Q chg -Q dch ) / (t1+t2) Formula 3

[0093] Among them, P loss is the energy loss of the battery 5 under test during the charge and discharge process, Q chg and Q dch They are respectively the charged power and the discharged power of the battery 5 to be tested.

[0094] The temperature acquisition device 104 includes a thermocouple 7 and a data collector 11. The specific connection method is that the data collector 11 is connected to the required temperature collection points through the thermocouple 7. The temperature collection points here include the key temperature collection points, surface temperature collection points, and internal temperature collection points of the battery 5 to be tested in the thermal resistance test. The thermocouple 7 in the temperature acquisition device can be arranged inside and outside the battery 5 to be tested. When arranged inside the battery 5 to be tested, the thermocouple 7 can be fixed at the position to be observed by ultraviolet light curing glue, two-liquid mixed curing glue or tape, etc., including the center of the battery, the pole, the lead sheet, the cover plate, the inner measurement of the aluminum shell, etc.

[0095] The following is a detailed illustration to illustrate the distribution of each temperature sampling point of the battery 5 to be tested, and the role of the data of each temperature sampling point in measuring the thermal resistance of the battery. For ease of understanding, the batteries 5 to be tested in the following description are all square batteries.

[0096] See also Figure 3 , Figure 3 This is a schematic diagram of the key temperature sampling point positions in a battery thermal resistance measurement provided in an embodiment of the present application. 17 is the ambient temperature sampling point; 18 is the battery maximum temperature sampling point; 19 is the temperature sampling point at the interface between the battery and the thermal conductive glue 8; 20 is the temperature sampling point at the interface between the thermal conductive glue 8 and the metal cold plate 9.

[0097] The function of the ambient temperature collection point 17 is to determine the temperature of the environment in which the battery 5 to be tested is located, and the temperature is used to calculate the maximum temperature T in the above formula 1, while ensuring that the temperature of the environmental box does not change. When using the battery thermal resistance measurement system provided in the embodiment of the present application, it is necessary to ensure that before the battery 5 to be tested is charged and discharged, the temperature of the battery 5 to be tested is consistent with that of the surrounding environment, and the temperature of the surrounding environment does not change.

[0098] The function of the battery maximum temperature sampling point 18 is to obtain the maximum temperature of the battery 5 to be tested during the charge and discharge test. The maximum temperature is used to calculate the maximum temperature T in the above formula 1. Here, the battery maximum temperature sampling point will be different in batteries made of different materials and shapes. In practical applications, the position of the actual maximum temperature should be used as the basis.

[0099] The temperature sampling point 19 at the interface between the battery 5 to be tested and the thermally conductive adhesive 8 and the temperature sampling point 20 at the interface between the thermally conductive adhesive 8 and the metal cold plate 9 are used to obtain the temperatures of the two points. The temperatures of the two points can be used to determine whether there is a problem of heat loss in the battery sample device 101, such as incomplete wrapping of the thermal insulation foam on the non-observation surface of the battery 5 to be tested. The specific judgment method is as follows:

[0100] Assume that the temperature collected by the ambient temperature collection point 17 is T1, the temperature collected by the temperature collection point 19 at the interface between the battery and the thermally conductive adhesive 8 is T3, and the temperature collected by the temperature collection point 20 at the interface between the thermally conductive adhesive 8 and the metal cold plate 9 is T4. After obtaining T1, T3 and T4, determine whether T3-T4 is equal to T1. Here, the temperature collected by the temperature collection point 19 at the interface between the battery and the thermally conductive adhesive 8 is subtracted from the temperature collected by the temperature collection point 20 at the interface between the thermally conductive adhesive 8 and the metal cold plate 9. The principle is that when there is no problem with the system, when the temperature between the battery and the thermally conductive adhesive 8 is higher than the ambient temperature, the heat generated by the battery will pass through the thermally conductive adhesive 8 to the metal cold plate 9, and finally reach thermal equilibrium, that is, the above T3-T4=T1. Various error factors are considered here. Whether the two sides are equal can be determined within a certain error range. In some possible embodiments, the result fluctuation within 0.5 degrees Celsius is considered to be an acceptable error.

[0101] See also Figure 4 , Figure 4 21 represents the battery, 22 represents the location of the temperature collection point on the battery surface, and there are many locations of the temperature collection points on the battery surface. Figure 4 All the black dots in the figure are the temperature collection points on the battery surface.

[0102] See also Figure 5 , Figure 5 This is a schematic diagram of the location of the temperature sampling points inside the battery in the battery thermal resistance measurement provided by the embodiment of the present application. 23 is the negative lead-out plate of the battery; 24 is the middle and upper part of the battery inner pole core; 25 is the center of the battery inner pole core; 26 is the positive lead-out plate of the battery.

[0103] The temperature collection points on the battery surface and inside the battery are used to find the maximum temperature of the battery. Since the structure and composition of each battery are different, the maximum temperature collection point of each battery will be different. Using multiple temperature collection points for one battery ensures that the maximum temperature collection point of the battery can be accurately found.

[0104] In some possible embodiments, the temperatures acquired at the temperature collection points on the battery surface and the temperature collection points inside the battery can be substituted into the above formula 3 to calculate the thermal resistance between any two points of the battery.

[0105] Above Figure 3 , Figure 4 and Figure 5The temperature obtained at the temperature sampling points in the test data acquisition unit 11 is as follows: since the temperature of the battery will change continuously during the charge and discharge process, after the computer 2 obtains the temperature data of each temperature sampling point collected by the data acquisition unit 11, the computer determines the maximum temperature of the battery 5 to be tested in the charge and discharge test by drawing a temperature change curve diagram, and when the battery 5 to be tested enters a thermal equilibrium state in the charge and discharge test.

[0106] In some possible embodiments, the temperature variation curve diagram can be seen in Figure 6 , Figure 6 is a temperature variation curve diagram of each temperature sampling point in a battery thermal resistance measurement provided by an embodiment of the present application. Figure 6 There are 3 lines in total, which represent the temperature changes of the 3 temperature sampling points of the battery 5 to be tested. It can be clearly seen that the temperature change trends of each temperature sampling point are roughly similar, all of which start to rise from 25 degrees Celsius, and after reaching a certain threshold, no longer change significantly, start to decline at a certain moment, return to 25 degrees Celsius, and start to rise from 25 degrees Celsius at a certain moment, and after reaching a certain threshold, no longer change significantly. Here, 25 degrees is the temperature of the set constant temperature environment box, and this value can be changed according to actual needs. The first rise of the curve is that the battery 5 to be tested enters the charging test stage. At this time, the battery test equipment charges the battery 5 to be tested. Between 5000s and 15000s, the temperature does not change much because the thermal balance of the battery 5 to be tested in the charging stage has been reached at this time. The subsequent decline indicates that the battery test equipment no longer charges the battery 5 to be tested, and the battery temperature drops. The subsequent temperature rise is that the battery 5 to be tested enters the discharge test stage. At this time, the battery 5 to be tested is discharged. Between 40000s-45000s, the temperature does not change much, indicating that the thermal balance of the battery 5 to be tested in the discharge stage has been reached at this time.

[0107] Among them, it can be obviously found that the temperature of Line 3 is the highest. It can also be obviously found that the temperature change curves of each temperature sampling point of the battery 5 to be tested are smooth between 5000s-15000s in the discharge process and between 40000s-45000s in the charging process. By drawing the temperature change curve, it can be easily confirmed when the battery 5 to be tested enters the charging or discharging stage, the maximum temperature of the battery 5 to be tested, and the time of the charging stage and the discharging stage of the battery 5 to be tested. By analyzing the temperature change curve, it is easier to obtain some parameters required for the subsequent thermal resistance calculation.

[0108] The above embodiment introduces in detail the battery thermal resistance measurement system provided by the present application. Based on the same inventive concept, the battery thermal resistance measurement method provided by the present application is further introduced below.

[0109] See also Figure 7 , Figure 7is a flow chart of a battery thermal resistance measurement method provided in an embodiment of the present application. The method can be applied to the battery thermal resistance measurement system provided in the present application. Figure 7 Said method comprises the following steps:

[0110] S701 : The battery testing device 103 obtains the charge and discharge parameters of the battery to be tested, wherein the battery to be tested is placed in a constant temperature environment provided by the constant temperature environment box 102 .

[0111] S702 : the battery testing device 103 sends the charge and discharge parameters of the battery to be tested to the computing device 105 . Correspondingly, the computing device 105 receives the charge and discharge parameters of the battery to be tested sent by the battery testing device 103 .

[0112] S703: The temperature acquisition device 104 tests the temperature of the battery to be tested.

[0113] S704 : the temperature acquisition device 104 sends the temperature of the battery to be tested to the computing device 105 . Correspondingly, the computing device 105 receives the temperature of the battery to be tested sent by the temperature acquisition device 104 .

[0114] S705: The computing device 105 calculates the thermal resistance of the battery to be tested based on the charge and discharge parameters of the battery to be tested and the temperature of the battery to be tested.

[0115] In a possible embodiment, the battery sample device 101 includes a metal cold plate and insulating foam. The metal cold plate contacts the battery to be tested, and the remaining surface of the battery to be tested except the contact surface is covered with insulating foam. The metal cold plate is used to absorb the heat emitted by the battery to be tested.

[0116] In a possible embodiment, the battery sample device 101 further includes thermally conductive adhesive, and the thermally conductive adhesive is coated on the contact surface between the metal cold plate and the battery to be tested.

[0117] In a possible embodiment, the thickness of the thermal conductive adhesive is greater than or equal to 0.1 mm and less than or equal to 2 mm, and the thermal conductivity of the thermal conductive adhesive is greater than or equal to 0.5 watts per meter·Kelvin and less than or equal to 5 watts per meter·Kelvin.

[0118] In a possible embodiment, the above charging and discharging parameters include: charging current I cell , discharge current Charging voltage U cell , discharge voltage Open circuit voltage U when not charged oc , open circuit voltage when not discharged The charging time t1 and the discharging time t2; the above-mentioned calculation device 105 calculates the thermal resistance R of the battery to be tested based on the charging and discharging parameters of the battery to be tested and the temperature of the battery to be tested.th The formula can be:

[0119]

[0120] R th =(T2-T1) / HGP

[0121] in, represents the temperature entropy coefficient of the battery to be tested, HGP represents the heat generation power of the battery to be tested, T represents the average value of the highest temperature among the temperatures of multiple points on the battery to be tested and the temperature of the constant temperature environment box, and T2 and T1 represent the temperatures of any two points among the multiple points.

[0122] In a possible embodiment, the charge and discharge parameters include: the charge power Q chg 、Discharge capacity Q dch , charging time t1 and discharging time t2; the above-mentioned calculation device 105 calculates the thermal resistance R of the battery to be tested based on the charging and discharging parameters of the battery to be tested and the temperature of the battery to be tested. th The formula can be:

[0123] HGP=(Q chg -Q dch ) / (t1+t2)

[0124] R th =(T2-T1) / HGP

[0125] Wherein, HGP represents the heat generation power of the battery under test, and T2 and T1 represent the temperatures of any two points on the battery under test.

[0126] Above Figure 7 The specific implementation process of the battery thermal resistance measurement method shown in the figure to achieve the battery thermal resistance measurement is detailed in the above-mentioned battery thermal resistance measurement system embodiment, which will not be repeated here.

[0127] The battery thermal resistance measurement system and method described above can be applied to the following three scenarios, but the present application does not limit the method and system to be applied only to the following three scenarios.

[0128] Application scenario 1: Verify whether the temperature rise and temperature difference of the battery meet the requirements.

[0129] For example, it is necessary to verify that after optimization, the surface temperature rise of each cell in a battery pack (composed of 30 aluminum shell cells connected in series) does not exceed 10 degrees Celsius, and the temperature difference between each cell does not exceed 5 degrees Celsius. Assume that before optimization, at a charge and discharge current of 10C, the surface temperature rise of the cells in the pack was measured to be 15 degrees Celsius, and the temperature difference between each cell was 11 degrees Celsius using a negative temperature coefficient (NTC) thermistor. At this time, the developer decided to reduce the above temperature and temperature difference from the two levels of the cell and the liquid cooling plate, and proposed 15 solutions. At this time, if the negative temperature coefficient thermistor method is used to measure the temperature rise and temperature difference of the battery to verify these 15 solutions, the problem of long cycle and high cost will occur.

[0130] For the above application scenarios, the system and method provided by the embodiments of the present application can adopt the following steps:

[0131] M1: Take 3 sample cells of the unoptimized battery pack and 3 experimental cells of the above 15 solutions and place them in Figure 2 In the battery thermal resistance test system shown, the specific steps include:

[0132] A metal cold plate of a certain size is placed at the bottom of each battery cell, and a thermal conductive adhesive with the same or similar properties as the battery pack body is applied between each battery cell and the metal cold plate, and the thickness of the thermal conductive adhesive is also the same or similar to that of the battery pack body. A bracket is used to fix the battery cell and the metal cold plate at the inner center of the constant temperature box.

[0133] Here, the deviation of the thickness of the thermal conductive adhesive corresponding to different battery cells needs to be set to less than 0.5mm.

[0134] M2: Adjust all the above cells to be tested to a 50% state of charge, and then use a 10C equivalent current value to perform a cyclic charge and discharge test on all the above cells.

[0135] Here, the battery testing equipment has the same charging and discharging time and the same number of cycles for all cells to be tested. For example, the charging and discharging time may be 30 seconds, and the number of cycles may be 500.

[0136] M3: Extract the temperature of each temperature sampling point and draw a temperature curve based on the temperature.

[0137] The temperature sampling point here can be similar to Figure 3The temperature sampling points are arranged in the temperature collection point layout to obtain the ambient temperature T1, the highest temperature of the battery cell T2, the temperature at the interface between the battery cell and the thermal conductive adhesive T3, and the temperature at the interface between the thermal conductive adhesive and the metal cold plate T4. The T1, T2, T3, and T4 collected at each time are imported into the computer to draw a temperature curve change diagram.

[0138] Before drawing the temperature curve change graph, it is also necessary to determine whether the test is credible. The specific method is to determine whether T3-T4 is equal to T1. Here, the temperature T3 at the interface between the battery cell and the thermal conductive adhesive minus the temperature at the interface between the thermal conductive adhesive and the metal cold plate is equal to the ambient temperature. The principle is that when there is no problem with the battery sample equipment, when the temperature between the battery cell and the thermal conductive adhesive is higher than the ambient temperature, the excess heat will reach the metal cold plate through the thermal conductive adhesive. The error factor is considered here. The result fluctuation within 0.5 degrees Celsius is an acceptable error.

[0139] M4: According to the temperature curve change diagram, extract the circuit parameters and temperature of all the cells to be tested, and then determine the thermal resistance of all the cells.

[0140] Through the temperature curve change diagram, determine the voltage, current, time, temperature, and open circuit voltage of all the cells to be tested during charging and discharging, according to the above-mentioned formula 1:

[0141]

[0142] The heat generation power HGP of the battery is calculated, and finally the thermal resistance of each battery cell is determined by the above formula 2.

[0143] R th =T2-T1 / HGP Formula 2

[0144] M5: Compare the thermal resistance of all battery cells and select the battery cells that meet the requirements.

[0145] After calculating the thermal resistance of all battery cells, since the battery cells with smaller thermal resistance values ​​have smaller temperature rise and temperature difference under the current battery pack design, the corresponding optimization scheme is more effective. By comparing with the unoptimized sample battery cells, it is confirmed whether the optimized battery cells can meet the requirements of the maximum surface temperature rise of each battery cell not exceeding 10 degrees Celsius and the temperature difference between each battery cell not exceeding 5 degrees Celsius after packaging.

[0146] Application scenario 2: Determine whether the structural design of the battery cell is conducive to heat transfer and heat dissipation of the battery cell.

[0147] For example, the size and cooling method of the battery pack have been confirmed. There are now three types of cylindrical and square aluminum shell battery cells that meet the capacity and power requirements and are compatible in size. It is necessary to select a product that can have a thermal resistance of less than 0.4K / W at any two points on the battery cell under the World Light Vehicle Test Procedure (WLTP) or World Light Vehicle Test Cycle (WLTC) conditions.

[0148] The above-mentioned WLTP and WLTC are both tests for automobiles. The WLTP test includes low-speed, medium-speed, high-speed, and ultra-high-speed tests for automobiles, while the WLTC test does not have an ultra-high-speed test.

[0149] When the above method is applied to this application scenario, the thermocouple temperature collection wire used by the temperature collection device needs to be implanted into the battery cell. The specific steps can be: during the battery generation process, use ultraviolet light curing glue, two-liquid mixed curing glue or tape to fix it at the position to be detected. The position here can refer to Figure 6 For square cells, the location of the thermocouple temperature line should at least include the center of the cell, the positive lead sheet, the negative lead sheet, and the middle and upper area of ​​the large surface. For cylindrical cells, the thermocouple temperature line should at least include the center of the cell, the positive lead sheet, the negative lead sheet, and the upper area of ​​the middle thickness of the cell.

[0150] At this time, the steps of calculating the thermal resistance of each battery cell using the battery thermal resistance measurement method provided in this application include:

[0151] N1: Take 3 of each of the above 6 types of batteries and put them in Figure 2 In the battery thermal resistance test system shown, a metal cold plate and a bracket are placed at the bottom of each battery cell, and a thermal conductive adhesive that is the same as or similar to that of the battery pack is applied between the battery cell and the metal cold plate, while ensuring that the thickness error of the thermal conductive adhesive corresponding to each battery cell is less than 0.5 mm.

[0152] N2: According to the WLTP / WLTC working conditions, adjust the battery testing equipment, set the corresponding test current, voltage and time, and record the changes in the voltage and current of the battery cell in real time.

[0153] N3: Test the charge and discharge of all cells and extract Figure 3 The temperatures of each temperature sampling point include (ambient temperature T1, maximum temperature of the battery cell T2, temperature at the interface between the battery cell and the thermal conductive adhesive T3, temperature at the interface between the thermal conductive adhesive and the metal cold plate T4), where the maximum temperature of the battery cell T2 is Figure 6After arranging the thermocouple temperature sampling lines at each temperature sampling point shown, a temperature curve change diagram is drawn according to the extracted temperature, and the highest temperature when thermal equilibrium is reached is screened out.

[0154] Similar to application scenario 1, it is necessary to verify whether the solution is credible before comparison. The verification process can refer to the relevant content of the above application scenario 1, and this application will not describe it in detail here.

[0155] N4: According to the temperature curve change diagram, extract the circuit parameters and temperature of all the cells to be tested, obtain the temperature entropy coefficient of the cell by testing the state of charge-open circuit voltage curve of each cell at different temperatures, and finally determine the thermal resistance of all the cells.

[0156] The temperature entropy coefficient of the battery cell needs to be calculated here because this application scenario is for a variety of different battery cells. When the type of battery cell is different, the temperature entropy coefficient of the battery cell will also be different.

[0157] The voltage, current, time, temperature, open circuit voltage and temperature entropy coefficient of all cells to be tested during charging and discharging are determined through the temperature curve change diagram. The temperature entropy coefficient of the cell can be obtained by testing the state of charge-open circuit voltage curve of the cell at different temperatures using battery testing equipment.

[0158] Finally, the thermal resistance of each cell is determined according to Formula 1 and Formula 2:

[0159]

[0160] The heat generation power HGP of the battery is calculated, and finally the thermal resistance of each battery cell is determined by formula 2.

[0161] R th =T2-T1 / HGP Formula 2

[0162] N5: Select the appropriate type of battery cell by comparing the thermal resistance of each battery cell.

[0163] By comparing the thermal resistance of each battery cell, we can determine whether the structure of each battery cell is conducive to heat transfer and heat dissipation, so as to select the appropriate type of battery cell.

[0164] Application scenario 3: Determine the impact of the package on the temperature of the battery cell and whether the cooling solution design is reasonable.

[0165] For example, there is a battery cell product for packaging, and the temperature distribution of the battery cells in the package under working conditions is known. Testing the battery cell product using the battery thermal resistance measurement system and method provided by this application includes:

[0166] O1: Take 6 samples of this battery cell product and divide them equally into experimental group and control group.

[0167] O2: After the thermocouple collection lines of the temperature collection equipment are arranged on the surface of the battery cells of the experimental group and the control group, the battery cells of the experimental group are fixed on top of the thermal conductive glue and the metal cold plate and then placed on the bracket. The battery cells of the control group are directly placed on the bracket. Finally, the other surfaces of the battery cells of the experimental group and the control group are wrapped with insulating foam.

[0168] Here, after placing the battery cells of the experimental group into the battery thermal resistance measurement system, it is also necessary to adjust the metal cold plate and the bracket so that the heat transfer path from the battery cells to the thermal conductive adhesive is basically consistent with the heat transfer path of the battery cells of the control group.

[0169] Here, the thermal conductive adhesive needs to have high thermal conductivity, such as a thermal conductivity of 2W / m / K. The thickness can be set to about 0.8mm.

[0170] Here, the selection of the metal cold plate needs to be determined according to the internal structure of the package. If the battery cells in the package in the layout application scenario 3 are cooled by bottom liquid cooling, and the coolant flow rate is 5L / min, the heat exchange capacity is calculated based on the type of coolant, flow rate and other information, and a metal cold plate with sufficient heat exchange capacity is selected as a replacement.

[0171] O3: After the cells of the experimental group and the control group are stabilized at the ambient temperature, charge and discharge tests are performed on the cells of the two groups to observe the changes in the data collected by the temperature collector.

[0172] The surface temperatures of the two groups of battery cells are obtained through a temperature data collector. If the temperature of the battery cells in the experimental group is higher than that of the battery cells in the control group, it means that there are other electronic components in the battery pack that heat the battery cells or there is a problem with the cooling method of the battery pack, resulting in insufficient heat exchange capacity.

[0173] In the above-mentioned embodiments, the description of each embodiment has its own emphasis. For the part that is not described in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0174] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0175] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0176] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0177] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application can be essentially or partly embodied in the form of a software product that contributes to the prior art, or all or part of the technical solution. The computer software product is stored in a storage medium, including several instructions to enable a device (which can be a personal computer, server, or network device, robot, single-chip microcomputer, chip, robot, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard disks, read-only memories, random access memories, magnetic disks or optical disks.

[0178] The above is a detailed introduction to the embodiments of the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A battery thermal resistance measurement system, characterized in that: The system includes: battery sample equipment, a constant temperature environment box, battery testing equipment, temperature acquisition equipment and computing equipment; The battery sample device is used to load the battery to be tested; The constant temperature environment box is used to load the battery sample device and provide a constant temperature environment for the battery sample device; The battery testing device is connected to the battery to be tested, and is used to obtain the charge and discharge parameters of the battery to be tested; The temperature acquisition device is connected to the battery to be tested and is used to test the temperature of the battery to be tested; The computing device is connected to the battery testing device and the temperature acquisition device, and is used to receive the charge and discharge parameters of the battery to be tested sent by the battery testing device, and receive the temperature of the battery to be tested sent by the temperature acquisition device; The calculation device is further used to calculate the thermal resistance of the battery to be tested based on the charge and discharge parameters of the battery to be tested and the temperature of the battery to be tested.

2. The system according to claim 1, characterized in that The battery sample device comprises a metal cold plate and thermal insulation foam, wherein the metal cold plate contacts the battery to be tested, and the remaining surface of the battery to be tested except the contact surface is covered with the thermal insulation foam; The metal cold plate is used to absorb the heat emitted by the battery to be tested.

3. The system according to claim 2, characterized in that The battery sample device further comprises a heat-conducting adhesive, and the heat-conducting adhesive is coated on the contact surface between the metal cold plate and the battery to be tested.

4. The system according to claim 3, characterized in that The thickness of the thermally conductive adhesive is greater than or equal to 0.1 mm and less than or equal to 2 mm, and the thermal conductivity of the thermally conductive adhesive is greater than or equal to 0.5 watts per meter·Kelvin and less than or equal to 5 watts per meter·Kelvin.

5. The system according to any one of claims 1 to 4, characterized in that: The charging and discharging parameters include: charging current I cell , discharge current Charging voltage U cell , discharge voltage Open circuit voltage U when not charged oc , open circuit voltage when not discharged Charging time t1 and discharging time t2; The calculation device is specifically used to calculate the thermal resistance R of the battery to be tested by the following formula th : R th =(T2-T1) / HGP in, represents the temperature entropy coefficient of the battery to be tested, HGP represents the heat generation power of the battery to be tested, T represents the average value of the highest temperature among the temperatures of multiple points on the battery to be tested and the temperature of the constant temperature environment box, and T2 and T1 represent the temperatures of any two points among the multiple points.

6. The system according to any one of claims 1 to 4, characterized in that: The charging and discharging parameters include: charging power Q chg 、Discharge capacity Q dch , charging time t1 and discharging time t2; The calculation device is specifically used to calculate the thermal resistance R of the battery to be tested by the following formula th : HGP=(Q chg -Q dch ) / (t1+t2) R th =(T2-T1) / HGP Wherein, HGP represents the heat generation power of the battery to be tested, and T2 and T1 represent the temperatures of any two points on the battery to be tested.

7. A method for measuring thermal resistance of a battery, characterized in that: Applied to a battery thermal resistance measurement system, the system comprises: a battery sample device, a constant temperature environment box, a battery test device, a temperature acquisition device and a computing device; the battery sample device is used to load the battery to be tested; the constant temperature environment box is used to load the battery sample device; the battery test device is connected to the battery to be tested; the temperature acquisition device is connected to the battery to be tested; the computing device is connected to the battery test device and the temperature acquisition device; The method comprises: The battery testing device obtains the charge and discharge parameters of the battery to be tested, wherein the battery to be tested is located in a constant temperature environment provided by the constant temperature environment box; The temperature acquisition device tests the temperature of the battery to be tested; The computing device receives the charge and discharge parameters of the battery to be tested sent by the battery testing device, and receives the temperature of the battery to be tested sent by the temperature acquisition device; The calculation device calculates the thermal resistance of the battery to be tested based on the charge and discharge parameters of the battery to be tested and the temperature of the battery to be tested.

8. The method according to claim 7, characterized in that The battery sample device comprises a metal cold plate and thermal insulation foam, wherein the metal cold plate contacts the battery to be tested, and the remaining surface of the battery to be tested except the contact surface is covered with the thermal insulation foam; The metal cold plate is used to absorb the heat emitted by the battery to be tested.

9. The method according to claim 8, characterized in that The battery sample device further comprises a heat-conducting adhesive, and the heat-conducting adhesive is coated on the contact surface between the metal cold plate and the battery to be tested.

10. The method according to claim 9, characterized in that The thickness of the thermally conductive adhesive is greater than or equal to 0.1 mm and less than or equal to 2 mm, and the thermal conductivity of the thermally conductive adhesive is greater than or equal to 0.5 watts per meter·Kelvin and less than or equal to 5 watts per meter·Kelvin.

11. The method according to any one of claims 7 to 10, characterized in that: The charging and discharging parameters include: charging current I cell , discharge current Charging voltage U cell , discharge voltage Open circuit voltage U when not charged oc , open circuit voltage when not discharged Charging time t1 and discharging time t2; The calculating device calculates the thermal resistance of the battery to be tested based on the charge and discharge parameters of the battery to be tested and the temperature of the battery to be tested, including: The calculation device calculates the thermal resistance R of the battery to be tested by the following formula th : R th =(T2-T1) / HGP in, represents the temperature entropy coefficient of the battery to be tested, HGP represents the heat generation power of the battery to be tested, T represents the average value of the highest temperature among the temperatures of multiple points on the battery to be tested and the temperature of the constant temperature environment box, and T2 and T1 represent the temperatures of any two points among the multiple points.

12. The method according to any one of claims 7 to 10, characterized in that: The charging and discharging parameters include: charging power Q chg 、Discharge capacity Q dch , charging time t1 and discharging time t2; The calculating device calculates the thermal resistance of the battery to be tested based on the charge and discharge parameters of the battery to be tested and the temperature of the battery to be tested, including: The calculation device calculates the thermal resistance R of the battery to be tested by the following formula th : HGP=(Q chg -Q dch ) / (t1+t2) R th =(T2-T1) / HGP Wherein, HGP represents the heat generation power of the battery to be tested, and T2 and T1 represent the temperatures of any two points on the battery to be tested.

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