Method and apparatus for measuring heat generation rate of cylindrical battery

Abstract

The application discloses a kind of determination method and determination device of cylindrical battery heat generation rate, the determination device includes temperature control box, battery group placed in temperature control box, charge-discharge tester, and data acquisition processing unit for measuring battery group.The cylindrical battery heat generation rate determination method of the application fully considers the influence of heat loss on lithium ion measurement, through the heat flow meter arranged on the side of the battery to be measured, temperature calibration to accurately monitor the heat loss lost by the side of the battery;At the same time, by introducing annular opening copper sheet on the upper and lower ends of the thermal protection battery, the current is converged to reduce the contact resistance heat, the voltage and temperature are balanced, the heat loss of the upper and lower ends of the battery to be measured is compensated through the temperature rise curve on the copper sheet, and the instantaneous heat generation rate and average heat generation rate of the cylindrical battery can be directly and accurately measured.

Description

Technical Field

[0001] This invention relates to the field of thermal management technology for energy storage batteries, and in particular to a method and apparatus for measuring the heat generation rate of cylindrical batteries. Background Technology

[0002] Safety issues with power batteries are primarily caused by thermal runaway due to excessively high battery temperatures. Therefore, research on the thermal characteristics of power batteries has attracted widespread attention from researchers in the emerging new energy industry. Thermal runaway in power batteries is mainly caused by their imperfect thermal management systems; thus, designing an effective thermal management system is crucial for suppressing thermal runaway. Heat generation rate, as a fundamental thermal characteristic parameter of a battery, characterizes the amount of heat generated by the battery per unit time. The magnitude of the heat generation rate of a power battery determines the magnitude of its temperature rise; therefore, accurately measuring the instantaneous heat generation rate of the battery is necessary for designing a suitable and perfect thermal management system.

[0003] To address the aforementioned issues, invention patent number 201810870549.4 discloses a method for testing the heat generation rate of a power battery. This method first measures the heat loss and temperature change of the power battery during operation, then fits the functional equation of the average temperature of the power battery with operating time to obtain the first derivative of the equation, thereby obtaining the battery's temperature drop rate, and finally obtains the battery's heat generation rate after calibrating the heat loss. This testing process is simple and easy to operate, but it requires heat loss measurement before measurement, so the required testing time is relatively long.

[0004] In addition, invention patent No. 201510487355.2 discloses a method for estimating the heat generation of lithium-ion batteries under charging and discharging conditions. This method tests the lithium battery under external electric heating conditions, uses the differential heat balance equation to determine the relationship between heat loss and temperature of the lithium-ion battery under different electric heating powers, and finally calculates the heat generation rate of the battery based on the temperature rise curve of self-generated heat of the lithium-ion battery under different ambient temperatures and different discharge rates, using the differential heat balance equation. This testing method considers the impact of heat loss on lithium-ion measurement and improves the testing accuracy, but it involves many testing parameters, long testing time, and a cumbersome process.

[0005] Therefore, it is necessary to improve the existing methods to overcome the above-mentioned shortcomings. Summary of the Invention

[0006] The purpose of this invention is to provide a method and apparatus for measuring the heat generation rate of cylindrical batteries, which can realize in-situ non-destructive measurement of cylindrical batteries without the need for additional calibration process, with short measurement time and more accurate measurement results.

[0007] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0008] A method for determining the heat generation rate of a cylindrical battery includes the following steps:

[0009] S1. A number of thermal protection batteries are arranged around the battery under test as the center; the positive and negative terminals of the battery under test are provided with test battery wires for connecting to charge and discharge tests; the positive and negative terminals of the thermal protection batteries are respectively connected in parallel through a ring copper sheet to form a battery pack; the ring copper sheet is provided with ring copper sheet wires for connecting to charge and discharge tests.

[0010] S2. A thermocouple is installed near the upper and lower end faces and the center of the battery under test. A thermocouple is installed near the upper and lower end faces of one of the several thermal protection batteries. A thermocouple is installed at the annular copper sheet. A heat flow meter is installed at the center of the battery under test. The heat flow meter is connected to a data acquisition instrument through a heat flow meter wire to output its temperature and voltage signals.

[0011] S3. Use insulating materials to cover the top, sides and bottom of the battery pack to form a test section; then place the battery pack in a temperature control chamber, and connect the test battery wires and the ring copper wires to the discharge clamp of the charge and discharge tester to perform charge and discharge tests.

[0012] S4. A thermocouple is installed inside the temperature control box, and the thermocouples installed at the battery under test, the thermal protection battery, the annular copper sheet and the temperature control box are connected to the data acquisition instrument respectively, and the temperature signal and voltage signal are output.

[0013] S5. Keep the temperature inside the temperature control box constant at the initial temperature. When the battery temperature and the temperature inside the box reach thermal equilibrium, charge and discharge the test section through the charge and discharge tester. The thermal protection battery is connected in parallel, and the central battery under test is controlled separately. Record the temperature changes on the side of the battery under test, the temperature changes of the annular copper sheet, and the temperature changes of the thermal protection battery. Record the temperature and voltage signals of the battery from the start of discharge to the discharge cutoff process through the data acquisition instrument.

[0014] Let the mass of the battery under test be M, and the average heat generation rate of the battery be P. s The battery discharge time is t, and the temperature difference between the battery and the environment at the end of the discharge is ΔT. s According to the law of conservation of energy, the average heat generation rate P of the battery... s It can be represented as:

[0015]

[0016]

[0017] In the formula: Q loss To test the heat loss, P loss1 and Ploss2 The heat dissipation power of the battery's side and the heat dissipation power of its upper and lower end faces are measured. The side heat dissipation power is measured by a heat flow meter attached to the side.

[0018]

[0019] In the formula: ΔV is the heat flux voltage output by the heat flow meter, S calib This is the sensor conversion factor sensitivity after temperature calibration, measured in V / (℃·W), which was 1.2V / (℃·W) in the heat flow meter calibration experiment. sen Where A is the sensor temperature and A is the battery side surface area;

[0020] The heat loss from the upper and lower end faces of the battery can be approximated by the temperature rise of the annular copper sheet:

[0021]

[0022] In the formula: c cu It is the specific heat of the copper sheet, M cu1 It is the mass of the upper annular copper sheet, M cu2 It is the mass of the lower ring-shaped copper sheet. It is the rate of temperature rise of the annular copper sheet;

[0023] S6. After the discharge is complete, cool the battery pack down to room temperature and let it stand for a period of time before fully charging the battery pack for the next round of testing.

[0024] Furthermore, the internal resistance and capacity of the battery under test and the thermal protection battery mentioned in step S1 are the same, so as to ensure that the discharge time of the battery under test and the thermal protection battery are the same.

[0025] Furthermore, the annular copper sheet mentioned in step S1 has a thin and small structure with connecting holes. The size of the connecting holes is smaller than that of the positive or negative electrode of the battery. Solder is applied through the connecting holes to ensure a tight weld between the positive and negative electrodes of the battery and the copper sheet, avoiding poor soldering. This reduces heat generation due to contact resistance and balances the voltage and temperature of the surrounding battery. The measured resistance between the copper sheet and the battery electrodes is around 1 milliohm or less, which is much smaller than the internal resistance of the battery. This reduces contact resistance caused by poor wire contact and improves the battery pack balance and measurement accuracy.

[0026] Furthermore, the thermocouple mentioned in step S2 is a T-type thermocouple with a wire diameter of 0.25 mm and a measurement tolerance of ±0.4% within the temperature range.

[0027] Furthermore, the heat flow meter mentioned in step S3 is a film-type thermoelectric material with a precision of 1 microvolt. Thermally conductive silicone grease is uniformly applied between the heat flow meter and the side of the battery under test to reduce measurement errors caused by contact.

[0028] Furthermore, the heat insulation material mentioned in step S4 is silica aerogel, the positive and negative electrodes of the battery under test are individually connected to a charge-discharge tester to precisely control its charge and discharge, the thermal protection battery is connected in parallel through a ring copper sheet, and the positive and negative electrodes of the thermal protection battery are connected to the charge-discharge tester through a ring copper sheet wire.

[0029] Furthermore, the charge / discharge tester sets a static condition before setting the constant current discharge condition, with a static time interval of 1 minute to ensure that all batteries of the same model discharge simultaneously, thereby better ensuring the consistency of battery discharge time.

[0030] Furthermore, in step S4, the data acquisition time of the data acquisition instrument is set to 1 second to ensure the integrity of the acquired data.

[0031] Furthermore, in step S5, the specific heat of the battery under test is measured by the thermal protection method. Based on the temperature rise and specific heat value of the central battery under test, combined with the side heat loss measured by the heat flow meter and the heat loss of the upper and lower end faces compensated by the temperature rise of the annular copper sheet, the instantaneous heat generation rate and the average heat generation rate are calculated.

[0032] A device for measuring the heat generation rate of a cylindrical battery includes a temperature control chamber, a battery pack placed inside the temperature control chamber, a charge / discharge tester, and a data acquisition and processing unit for measuring the battery pack.

[0033] The battery pack includes several cylindrical batteries. Each cylindrical battery includes a test battery located at the center and several thermal protection batteries arranged around the test battery. The test battery and the several thermal protection batteries are connected and fixed by an annular copper sheet. The cylindrical batteries and the annular copper sheet are covered with heat-insulating material.

[0034] The charge-discharge tester includes a first test branch and a second test branch. The first test branch is connected to the positive and negative terminals of the battery under test through a wire of the battery under test, and the second test branch is connected to the positive and negative terminals of the thermal protection battery through a ring copper wire.

[0035] The data acquisition and processing unit includes a heat flow meter and several thermocouples. The heat flow meter is connected to the data acquisition instrument via heat flow meter wires to output its temperature and voltage signals. One end of the thermocouple is used to detect the temperature and voltage of the upper, middle and lower ends of the side of the battery under test, the side temperature and voltage of one of the thermal protection batteries, and the temperature and voltage inside the temperature control box. The other end of the thermocouple is connected to the data acquisition instrument, and the computer is connected to and controls the data acquisition instrument.

[0036] In summary, the present invention has the following beneficial effects:

[0037] 1. The method for determining the heat generation rate of cylindrical batteries of the present invention creates a near-adiabatic thermal environment for the battery under test by arranging thermally protected batteries of the same specifications and models. This allows for rapid and accurate measurement of the heat generation rate of the battery under test without the need for an additional thermal loss calibration process. Furthermore, the method can simultaneously measure minute heat losses on the sides and ends during the measurement of the battery's heat generation rate, also without requiring an additional thermal loss calibration process. This results in a short measurement time and high accuracy.

[0038] 2. The cylindrical battery heat generation rate measurement method of the present invention fully considers the influence of heat loss on lithium-ion measurement. It uses a heat flow meter arranged on the side of the battery under test to accurately monitor the heat loss dissipated from the side of the battery. At the same time, by introducing copper sheets at the top and bottom of the thermally protected battery, and obtaining the temperature rise curve of the copper sheets through thermocouple sensors arranged on the copper sheets, the heat loss at the top and bottom of the battery under test is approximately compensated. It can directly and accurately measure the instantaneous heat generation rate and average heat generation rate of the cylindrical battery.

[0039] 3. The cylindrical battery heat generation rate measurement device of the present invention has a simple structure and is easy to operate. The measuring device connects a thermal protection battery in parallel via a perforated copper sheet. This reduces heat generation due to contact resistance, balances the voltage and temperature of the thermal protection battery, and avoids the significant difference in discharge time between the battery under test and the surrounding thermal protection battery caused by voltage inconsistencies due to wire resistance. This ensures that the discharge time of the surrounding thermal protection battery is essentially the same as that of the battery under test. Furthermore, the temperature rise of the copper sheet compensates for heat loss at the top and bottom of the battery under test, thereby improving the measurement accuracy of battery heat generation. By adjusting the initial temperature of the temperature control chamber and the discharge rate of the charge / discharge tester and repeating the measurement process, the heat generation rate of cylindrical batteries under different temperature conditions and discharge rates can be tested. This provides reliable test data on the heat generation rate of cylindrical batteries for cylindrical battery manufacturers, electric vehicle companies, and other organizations, and can be used for battery thermal management and thermal runaway protection design.

[0040] 4. The method for measuring the heat generation rate of cylindrical batteries of the present invention takes into account the temperature calibration of the heat flow meter, accurately measures the heat loss rate of the battery at different temperatures, and is applicable to a wide temperature range, providing a new approach for measuring thermal characteristic parameters such as the heat generation rate of batteries. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the cylindrical battery pack of the present invention.

[0042] Figure 2 This is an exploded view of the cylindrical battery pack structure in this invention.

[0043] Figure 3 A schematic diagram of the cylindrical battery heat generation rate measuring device in this invention.

[0044] Figure 4This is a curve showing the change in side thermal loss of the cylindrical battery under test as a function of depth of discharge (DOD) obtained in an embodiment of the present invention.

[0045] Figure 5 This is a temperature rise diagram of the cylindrical battery under test, the copper sheet, and the adiabatic accelerated calorimeter (ARC) obtained in an embodiment of the present invention.

[0046] Figure 6 The graph shows the heat generation rate of the cylindrical battery under test at a 2C discharge rate as a function of DOD, obtained in an embodiment of the present invention.

[0047] Figure 7 The following figures show the test results of different power levels obtained by the present invention based on a 6063 aluminum simulated battery: (a) temperature rise curve; (b) temperature difference between the surrounding battery and the middle battery; (c) heat loss rate; (d) heat generation rate measured at a given input power. Detailed Implementation

[0048] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to the figures and specific embodiments.

[0049] like Figures 1 to 7 As shown, the present invention proposes a method for determining the heat generation rate of a cylindrical battery, comprising the following steps:

[0050] S1. Place a cylindrical battery to be tested in the center, and distribute N other batteries of the same model at the same height around the battery to be tested to form a thermal protection battery. The battery to be tested in the center is directly connected to the charge and discharge tester by welding wires. The positive and negative terminals of the multiple thermal protection batteries arranged around it are connected in parallel by ring copper sheets. Three wires are welded at equal angles on the upper and lower copper sheets to connect to the external charge and discharge tester, thus forming a battery pack consisting of (N+1) batteries.

[0051] S2. A thermocouple is welded 2mm from the top and bottom of the side of the battery under test and at the center to monitor the side temperature of the battery under test. A thermocouple is also welded at the same position above and below a nearby thermal protection battery to monitor its temperature rise. At the same time, thermocouples are soldered to the copper sheets at the top and bottom to monitor the temperature rise of the copper sheets. A heat flow meter is attached to the center of the side of the battery under test to monitor the heat loss from its side. The heat flow meter outputs a voltage signal proportional to the temperature difference and heat flow through a wire based on the thermoelectric effect. The voltage is read by a data acquisition instrument to calculate the heat loss heat flow.

[0052] S3. Wrap the sides and top and bottom surfaces of the battery pack with insulation material twice to form a test section. Then place the assembled battery pack inside the temperature control box. Connect the two wires on the positive and negative terminals of the battery under test and the six wires on the copper plates at the top and bottom to two pairs of Xinwei charge and discharge tester clips to provide charge and discharge testing.

[0053] S4. Arrange thermocouples for monitoring the temperature inside the temperature control box in the lower left corner, and connect the thermocouples for monitoring the battery temperature, the thermocouples for monitoring the temperature inside the box, and the thermocouples for monitoring the battery under test on the heat flow meter to the data acquisition instrument to output temperature and voltage signals.

[0054] S5. Control the temperature control box to keep the temperature inside the box constant at the initial temperature. Let the battery pack stand in the box for 2 hours to eliminate the inconsistency between the battery pack temperature and the set temperature. When the temperature difference between the battery temperature and the temperature inside the box is controlled within 0.2℃ for 5 consecutive minutes, charge and discharge the test section using the Xinwei charge and discharge tester. The surrounding thermal protection batteries are connected in parallel, and the central battery under test is controlled separately. Record the changes in the side temperature of the battery under test, the copper sheet temperature, and the temperature of the thermal protection battery. Record the temperature and voltage signals of the battery from the start of discharge to the discharge cutoff process using a data acquisition instrument.

[0055] Let the mass of the battery under test be M, and the average heat generation rate of the battery be P. s The battery discharge time is t, and the temperature difference between the battery and the environment at the end of the discharge is ΔT. s According to the law of conservation of energy, the average heat generation rate P of the battery... s It can be represented as:

[0056]

[0057]

[0058] In the formula: Q loss To test the heat loss, P loss1 and P loss2 The heat dissipation power of the battery's side and the heat dissipation power of its upper and lower end faces are measured. The side heat dissipation power is measured by a heat flow meter attached to the side.

[0059]

[0060] In the formula: ΔV is the heat flux voltage output by the heat flow meter, S calib This is the sensor conversion factor sensitivity after temperature calibration, measured in V / (℃·W), which was 1.2V / (℃·W) in the heat flow meter calibration experiment. sen Where A is the sensor temperature and A is the battery side surface area;

[0061] The heat loss from the upper and lower end faces of the battery can be approximated by the temperature rise of the annular copper sheet:

[0062]

[0063] In the formula: c cu It is the specific heat of the copper sheet, M cu1 It is the mass of the upper annular copper sheet, M cu2 It is the mass of the lower ring-shaped copper sheet. It is the rate of temperature rise of the annular copper sheet;

[0064] S6. After the discharge is complete, cool the battery pack down to room temperature and let it stand for a period of time before fully charging the battery pack for the next round of testing.

[0065] The above testing method involves placing one of several identical cylindrical batteries in the center as the test battery. The remaining batteries are evenly distributed around the test battery as thermal protection batteries. The positive and negative terminals of the central test battery are soldered with wires to individually control its charging and discharging. The surrounding thermal protection batteries are connected in parallel via two copper plates. Three wires are soldered to the upper and lower copper plates respectively to control the charging and discharging of the thermal protection batteries. A thermocouple is soldered 2mm from the top and bottom edges and at the center of the test battery to monitor its side temperature. A thermocouple is also soldered at the same positions above and below one of the surrounding thermal protection batteries to monitor its temperature rise. Additionally, a thermocouple is placed at the center of the side of the test battery. A heat flow meter is attached to monitor heat loss from the sides of the battery pack. The heat flow meter's leads are led downwards to connect to an Agilent data acquisition instrument to output temperature and voltage signals. The sides and top and bottom surfaces of the battery pack are then wrapped twice with insulating material to form a test section. This assembled test section is placed inside a temperature-controlled chamber. The positive and negative leads of the battery under test, as well as the leads on the copper plates at the top and bottom, are connected to the clips of a Newway charge / discharge tester to provide charge / discharge testing. A thermocouple is placed in the lower left corner of the temperature-controlled chamber to monitor the chamber temperature. The thermocouples monitoring the battery temperature, the chamber temperature, and the center thermocouple of the battery under test on the heat flow meter are connected to the data acquisition instrument to output temperature and voltage signals. The batteries should have similar or identical internal resistance and capacity to eliminate differences in discharge time between the battery under test and the thermally protected battery caused by inconsistencies in internal resistance and capacity. This ensures that the battery under test remains in a near-insulated environment throughout the discharge process. Insulating material is used to fill the gaps between the batteries to prevent convective heat transfer from air in the gaps.

[0066] Figure 4 This is a curve showing the change in side thermal loss as a function of DOD of the cylindrical battery under test, obtained from an embodiment of the present invention. Figure 5 The temperature rise diagrams of the cylindrical battery under test, the copper sheet, and the ARC obtained in the embodiments of this invention are shown below. Figure 6This is a curve showing the heat generation rate as a function of DOD at a 2C discharge rate of the cylindrical battery under test, obtained in an embodiment of the present invention. Under natural convection conditions, the battery was fully charged at a 0.5C charging rate (100% SOC). The measuring device was then assembled, and the initial temperature of the constant temperature chamber was set to 25°C. The battery was allowed to stand until the temperature difference between the battery and the chamber temperature was consistently controlled within 0.2°C for 5 consecutive minutes. The battery was then discharged at 2C, and data collection was stopped after the discharge was complete. The temperature rise of the battery side and copper sheet was measured experimentally. Figure 5 ) and the heat loss curve of the side of the battery under test ( Figure 4 At this point, the specific heat, as determined by literature on quasi-steady-state thermal protection methods, is 979 J·kg⁻¹. -1 ℃ -1 The instantaneous heat generation rate of the battery under test was calculated according to the heat generation rate formula, and its curve as a function of DOD was plotted. Figure 6 The 2C discharge time was 1749s, and the temperature rise of the battery at the discharge cutoff was 30.075℃. Combining the side heat loss measured by the heat flow meter and the upper and lower end heat losses calculated from the copper sheet temperature rise, the average heat generation rate of the battery at the 2C discharge rate was found to be 0.890W. Simultaneously, the experimentally measured temperature rise was compared with the temperature rise under the 2C discharge rate of the ARC equipment. Figure 5 The temperature rise trends of both devices were basically consistent. At the discharge cutoff, the ARC temperature rise was 29.734℃, with a relative error of 1.15% between the experimental and ARC device temperatures. The average heat generation rate of the ARC device at a 2C discharge rate was 0.881W, with a relative error of only 1.25% between the experimental and ARC device average heat generation rates.

[0067] This method was validated using a 6063 aluminum simulated battery. A 6063 aluminum simulated battery with the same dimensions as a cylindrical battery was prepared. A heating rod (Φ6.5mm × 42mm) was placed in the center of the simulated battery to simulate heat generation. The heating rod was made of 304 stainless steel and weighed 11.9g. The 6063 aluminum casing of the simulated battery weighed 41.9g, and the specific heat capacity of the simulated battery was 811.52 J·kg⁻¹. -1 ℃ -1 A constant power verification experiment ranging from 0.96W to 4.86W was conducted using this measurement method, and the test results are plotted on [the graph / plot]. Figure 7 As can be seen, when the maximum relative error between the output heat generation rate and the input heat generation rate is 1.95W, the average output heat generation rate is 1.93W, and the maximum relative error is only 1.01%, which proves that the test method has high accuracy and meets the engineering accuracy requirements, indicating that the measured values ​​of this method have high reliability.

[0068] The method and apparatus for measuring the heat generation rate of cylindrical batteries provided by this invention can test the heat generation rate of cylindrical batteries under different temperature conditions and different discharge rates. The testing process is simple, the testing time is short, the results are accurate, and it is easy to implement. It can provide reliable test data on the heat generation rate of cylindrical batteries for cylindrical battery manufacturers, electric vehicle companies, research institutes and other institutions, and can be used for battery thermal management and thermal runaway protection design.

[0069] In this document, the terms "upper," "lower," "front," "back," "left," "right," "top," "bottom," "inner," "outer," "vertical," and "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only used for the clarity of expressing the technical solution and for the convenience of description, and therefore should not be construed as limiting the present invention.

[0070] In this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, which includes not only the elements listed but also other elements not expressly listed.

[0071] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for determining the heat generation rate of a cylindrical battery, characterized in that, Includes the following steps: S1. A number of thermal protection batteries of the same type are arranged around the battery under test as the center; the positive and negative terminals of the battery under test are provided with test battery wires (4) for connecting to charge and discharge tests; the positive and negative terminals of the thermal protection batteries are connected in parallel through a ring copper sheet (6) to form a battery pack (9); a ring copper sheet wire (7) for connecting to charge and discharge tests is provided on the ring copper sheet (6); S2. A thermocouple (11) is set near the upper and lower end faces and the center of the battery under test. A thermocouple (11) is set near the upper and lower end faces of one of the several thermal protection batteries. A thermocouple (11) is set at the annular copper sheet (6). A heat flow meter (2) is set at the center of the battery under test. The heat flow meter (2) is connected to a data acquisition instrument (12) through the heat flow meter wire (3) to output its temperature and voltage signals. S3. Use heat insulation material (1) to cover the top, sides and bottom of the battery pack (9) to form a test section; then place the battery pack (9) in the temperature control box (8) and connect the test battery wire (4) and the ring copper wire (7) to the clamp of the charge and discharge tester (14) respectively to perform charge and discharge tests. S4. A thermocouple (11) is installed in the temperature control box (8), and the thermocouples (11) installed at the battery under test, the thermal protection battery, the annular copper sheet (6) and the temperature control box (8) are connected to the data acquisition instrument (12) respectively, and the temperature signal and voltage signal are output. S5. Keep the temperature inside the temperature control box (8) unchanged from the initial temperature. When the battery temperature and the temperature inside the box reach thermal equilibrium, charge and discharge the test section through the charge and discharge tester (14). The thermal protection battery is connected in parallel, and the central test battery is controlled separately. Record the temperature change of the side of the test battery, the temperature change of the annular copper sheet (6) and the temperature change of the thermal protection battery. Record the temperature and voltage signals of the battery from the start of discharge to the discharge cutoff process through the data acquisition instrument (12). Let the mass of the battery under test be M, and the average heat generation rate of the battery be P. s The battery discharge time is t, and the temperature difference between the battery and the environment at the end of the discharge is . According to the law of conservation of energy, the average heat generation rate P of the battery... s It can be represented as: In the formula: Q loss To test the heat loss, P loss1 and P loss2 The heat dissipation power on the side of the battery under test and the heat dissipation power on the top and bottom surfaces of the battery; The heat dissipated from the upper and lower end faces of the battery can be approximated by the temperature rise of the annular copper sheet (6): In the formula: c cu It is the specific heat of the copper sheet, M cu1 The mass of the upper annular copper sheet (6), M cu2 It is the mass of the lower annular copper sheet (6). N is the rate of temperature rise of the annular copper sheet (6), and N is the number of surrounding thermal protection batteries. S6. After the discharge is complete, cool down the battery pack (9) to room temperature and let it stand for a period of time. Then fully charge the battery pack (9) for the next round of testing.

2. The method for determining the heat generation rate of a cylindrical battery according to claim 1, characterized in that, The internal resistance and capacity of the battery under test and the thermal protection battery mentioned in step S1 are the same to ensure that the discharge time of the battery under test and the thermal protection battery are the same.

3. The method for determining the heat generation rate of a cylindrical battery according to claim 1, characterized in that, The annular copper sheet (6) mentioned in step S1 is a thin and small structure. It has connection holes and is tightly welded to the positive and negative terminals of the battery through the connection holes to reduce contact resistance and balance voltage and temperature.

4. The method for determining the heat generation rate of a cylindrical battery according to claim 1, characterized in that, The thermocouple (11) mentioned in step S2 is a T-type thermocouple with a wire diameter of 0.25 mm and a measurement tolerance of ±0.4% within the temperature range.

5. The method for determining the heat generation rate of a cylindrical battery according to claim 1, characterized in that, The heat flow meter (2) mentioned in step S2 is a film based on thermoelectric material with an accuracy of 1 microvolt. Thermal grease is uniformly applied between the heat flow meter (2) and the side of the battery under test to reduce measurement errors caused by contact. The side heat dissipation power is generated by the heat flow meter (2) attached to the side. Temperature calibration is required to accurately measure the heat loss. After calibration, the heat loss rate is measured as follows: In the formula: ∆V is the heat flux voltage output by the heat flow meter (2), S calib This is the calibrated sensor conversion factor sensitivity, in V / ( °C·W). A is the sensor temperature, and A is the side area of ​​the battery.

6. The method for determining the heat generation rate of a cylindrical battery according to claim 1, characterized in that, The heat insulation material (1) mentioned in step S3 is silica aerogel. The positive and negative electrodes of the battery under test are connected separately to the charge and discharge tester (14) to accurately control its charge and discharge. The thermal protection battery is connected in parallel through the positive and negative annular copper sheets (6) and connected to the charge and discharge tester (14) through the annular copper sheet wire (7).

7. The method for determining the heat generation rate of a cylindrical battery according to claim 1, characterized in that, The charge / discharge tester (14) sets a static condition before setting the constant current discharge condition, with a static time interval of 1 minute to ensure that all batteries of the same model discharge at the same time and to ensure the consistency of battery discharge time.

8. The method for determining the heat generation rate of a cylindrical battery according to claim 1, characterized in that, In step S4, the data acquisition time of the data acquisition instrument (12) is set to 1 second to ensure the integrity of the acquired data.

9. The method for determining the heat generation rate of a cylindrical battery according to claim 1, characterized in that, In step S5, the specific heat of the battery under test is measured by the thermal protection method. Based on the temperature rise and specific heat value of the central battery under test, combined with the side heat loss measured by the heat flow meter (2) and the upper and lower end heat loss compensated by the temperature rise of the annular copper sheet (6), the instantaneous heat generation rate and the average heat generation rate are calculated.

10. An apparatus for measuring the heat generation rate of a cylindrical battery, used to implement the measurement method as described in any one of claims 1-9, characterized in that, Includes a temperature control box (8), a battery pack (9) placed inside the temperature control box (8), a charge / discharge tester (14), and a data acquisition and processing unit for measuring the battery pack (9); The battery pack (9) includes several cylindrical batteries (5). Each cylindrical battery (5) includes a battery under test located at the center and several thermal protection batteries arranged around the battery under test. The battery under test and several thermal protection batteries are connected and fixed by an annular copper sheet (6). The cylindrical battery (5) and the annular copper sheet (6) are covered with a heat-insulating material (1). The charge-discharge tester (14) includes a first test branch and a second test branch. The first test branch is connected to the positive and negative terminals of the battery under test through the test battery wire (4). The second test branch is connected to the positive and negative terminals of the thermal protection battery through the ring copper wire (7). The data acquisition and processing unit includes a heat flow meter (2) and several thermocouples (11). The heat flow meter (2) is connected to the data acquisition instrument (12) through the heat flow meter wire (3) to output its temperature and voltage signals. One end of the thermocouple (11) is used to detect the temperature and voltage of the upper, middle and lower ends of the side of the battery under test, the side temperature and voltage of one of the thermal protection batteries, and the temperature and voltage inside the temperature control box (8). The other end of the thermocouple (11) is connected to the data acquisition instrument (12). The computer (13) is connected to and controls the data acquisition instrument (12).

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