Battery heating power testing device and calculation method

Abstract

The invention belongs to the technical field of batteries, and provides a battery heating power testing device and a calculating method.The device comprises a testing tool box, a heat preservation layer, a plurality of temperature sensors, a temperature collecting device, a charging and discharging device and a power line, the power line is used for connecting the charging and discharging device and a battery, and the battery is contained in the testing tool box; the test tool box is provided with a wiring hole used for arranging a power line and a temperature sensor, and the wiring hole is provided with a sealing structure. According to the battery heating power testing device and the calculation method, battery spontaneous heating, convective heat transfer between the battery and the internal environment of the testing tool box and radiative heat transfer between the battery and the inner surface of the testing tool box are calculated based on the heat balance principle, and the battery heating power calculated through the method is small in error, high in accuracy and high in reliability. And an important basis can be provided for battery thermal evaluation.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a battery heating power testing device and a calculation method. Background Art

[0002] With the shortage of fossil energy and the aggravation of environmental pollution, energy conservation and emission reduction, energy storage technology has gradually been paid attention to, and electric vehicles, energy storage systems and other fields have developed rapidly. As the core energy conversion and storage device, the safety and life of the battery have a great impact on the operating efficiency and cost of the entire system. During the cycle of the battery, part of the heat generated is irreversible heat caused by the battery's ohmic internal resistance and polarization internal resistance, and the other part is irreversible reaction entropy heat caused by electrochemical reactions.

[0003] During the use and storage of lithium-ion batteries, temperature has an important impact on the performance, life, and safety of the battery. The temperature of lithium-ion batteries affects their energy, power performance, and safe use. When the battery temperature is low, the internal resistance of the battery increases significantly, and the available energy and power of the battery are greatly reduced. When the battery temperature is too high, on the one hand, the internal side reactions of the battery intensify, the battery capacity decays, and the battery life is reduced; on the other hand, overheating of the battery will cause thermal runaway of the battery, resulting in accidents such as battery explosion. Therefore, it is extremely important to accurately and efficiently evaluate the heat generation power of the battery, so as to accurately evaluate the temperature changes during the battery charging and discharging process.

[0004] The existing evaluation method of battery heating power generally adopts accelerated calorimeter (ARC) or Bernardi formula for measurement. The Bernardi formula calculation has problems such as insufficient test accuracy and too many test parameters. The accelerated calorimeter needs to be purchased, and the test has problems such as high cost and complicated test process. Summary of the invention

[0005] The purpose of the present invention is to provide a battery heating power testing device and a calculation method to solve the problems of insufficient accuracy and high cost of the battery heating power evaluation method in the prior art.

[0006] The present invention provides a battery heating power testing device, comprising a test tool box, a heat preservation layer wrapped around the outside of the test tool box, a plurality of temperature sensors arranged in the test tool box, a temperature acquisition device connected to the plurality of temperature sensors, a charging and discharging device connected to a battery, a power line, and a temperature sensor connecting line, wherein the power line is used to connect the charging and discharging device and the battery, the battery is accommodated in the test tool box, a wiring hole for arranging the power line and the temperature sensor is opened on the test tool box, a sealing structure is provided at the wiring hole, and the plurality of temperature sensors are respectively used to obtain the surface temperature of the battery, the center temperature of the battery, the inner surface temperature of the test tool box, the internal environment temperature of the test tool box, and the external environment temperature of the test tool box.

[0007] The above-mentioned battery heating power testing device realizes battery heating power evaluation by collecting the temperature of the battery surface, the battery center, the inner surface temperature of the test tool box, and the internal ambient temperature of the test tool box. The testing device is simple, easy to operate, and low in cost, and can simply and efficiently evaluate the battery heating power demand.

[0008] Furthermore, the test tool box is assembled by splicing.

[0009] Furthermore, the wiring holes are provided on the side or top surface of the test tool box.

[0010] Furthermore, the sealing structure is a sealant.

[0011] The present invention also provides a calculation method for a battery heating power test device, which is applied to the battery heating power test device as described above, and the method comprises:

[0012] Placing the battery to be tested in the test tool box and leaving it to stand for a preset time, so that the temperature of the battery to be tested and the temperature inside and outside of the test tool box are consistent;

[0013] Calculating the convection heat transfer coefficient between the outer surface of the battery to be tested and the internal environment of the test tool box;

[0014] Calculating the thermal resistance between the winding core and the battery housing of the battery to be tested;

[0015] Calculating the radiation heat transfer between the battery to be tested and the inner surface of the test tool box;

[0016] Calculating the convective heat transfer between the battery to be tested and the internal environment of the test tool box;

[0017] Calculating the change in heat absorption of the battery to be tested during the charge and discharge cycle to obtain the self-heating of the battery to be tested;

[0018] The total heat generated by the battery to be tested is calculated, where the total heat generated is the sum of the radiation heat transfer, the convection heat transfer and the self-heating.

[0019] The above-mentioned battery heating power testing device and calculation method are based on the principle of thermal balance, and respectively calculate the battery self-heating, the convection heat transfer between the battery and the internal environment of the test tool box, and the radiation heat transfer between the battery and the inner surface of the test tool box. This method has a small error and high accuracy in calculating the heating power of the battery, which can provide an important basis for battery thermal evaluation.

[0020] Furthermore, the calculation formula of the convective heat transfer coefficient is:

[0021] h=λNu1 / l;

[0022] Among them, h represents the convective heat transfer coefficient, Nu1 is the Nusselt number, λ is the thermal conductivity of air, and l is the characteristic length.

[0023] Furthermore, the calculation formula of the thermal resistance is:

[0024]

[0025] Where R1 is the thermal resistance between the winding core and the battery casing, T cell is the core center temperature, T surf is the battery surface temperature, T amb is the ambient temperature in the test box, h is the convective heat transfer coefficient, A is the outer surface area of ​​the battery excluding the bottom, ε is the emissivity of the outer surface of the battery, σ is the Stefan-Boltzmann constant, T s To test the inner surface temperature of the tooling box; the right side of the thermal resistance calculation formula is the sum of convective heat transfer and radiation heat transfer.

[0026] Furthermore, the formula for radiation heat transfer is:

[0027]

[0028] Where Q1 represents the radiation heat transfer between the battery and the inner surface of the test tool box.

[0029] Furthermore, the calculation formula for the convective heat transfer includes:

[0030] Q2=hA(T surf -T amb );

[0031] Among them, Q2 represents the convection heat transfer between the battery and the internal environment of the test tooling box.

[0032] Furthermore, the calculation formula of the self-heating is:

[0033] Q3=CP1 M(dT cell / d t );

[0034] Wherein, Q3 represents the change in the internal energy of the battery, M represents the mass of the battery, and C p1 represents the specific heat capacity of the battery, dT cell / d t represents the derivative of the core center temperature and time; for batteries without temperature rise points (points) arranged on the core, T cell The value is T cell =T surf +(Q1+Q2)R1. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the results of the battery heating power testing device in the first embodiment of the present invention;

[0036] Figure 2 The diagram shows the points on the outer surface of the battery;

[0037] Figure 3 It is a schematic diagram of the battery coil core layout;

[0038] Figure 4 This is a schematic diagram of the layout of the battery heating power test device at the first viewing angle;

[0039] Figure 5 This is a schematic diagram of the layout of the battery heating power test device under the second viewing angle;

[0040] Figure 6 This is a sealing test diagram of the battery heating power test device;

[0041] Figure 7 It is a flow chart of a calculation method of a battery heating power testing device in a first embodiment of the present invention;

[0042] Figure 8 is the battery equivalent thermal resistance model;

[0043] Fig. 9 The figure shows the comparison between the actual temperature rise of the battery's natural heat dissipation and the simulated temperature rise;

[0044] Fig.10 Shown is a schematic diagram of a battery air cooling test experimental device;

[0045] Fig.11 The figure shows the comparison between the actual temperature rise and the simulated temperature rise of the battery under air cooling.

[0046] Fig.12 The figure shows the ARC constant power discharge verification analysis diagram;

[0047] Fig.13Shown is the ARC constant power charging verification analysis diagram.

[0048] Description of main component symbols:

[0049] Test tool box 10 Charging and discharging equipment 50 Air duct partition 91 Insulation layer 20 Power Line 60 fan 92 Temperature Sensor 30 Chassis 80 Air Inlet 81 Temperature acquisition equipment 40 Insulation cotton 90 Battery 100

[0050] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0051] In order to facilitate understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. Several embodiments of the present invention are provided in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0052] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0054] See also Figure 1 The present invention provides a battery heating power testing device, comprising a test tool box 10, a heat preservation layer 20 wrapped around the outside of the test tool box 10, a plurality of temperature sensors 30 arranged in the test tool box 10, a temperature acquisition device 40 connected to the plurality of temperature sensors 30, a charging and discharging device 50 connected to a battery 100, and a power line 60, wherein the power line 60 is used to connect the charging and discharging device 50 and the battery 100, and the battery 100 is accommodated in the test tool box 10, and a wiring hole (not shown) for arranging the power line 60 and the temperature sensor 30 is opened on the test tool box 10, and a sealing structure, such as a sealant, is provided at the wiring hole, and the plurality of temperature sensors 30 are respectively used to obtain the battery surface temperature, the battery center temperature, the inner surface temperature of the test tool box 10, the internal environment temperature of the test tool box 40, and the external environment temperature of the test tool box 40 of the battery 100.

[0055] In one embodiment, the side of the test tool box 10 is provided with routing holes for arranging the power line 60 and the temperature sensor 30 ; in another embodiment, the top surface of the test tool box 10 is provided with routing holes for arranging the power line 60 and the temperature sensor 30 .

[0056] In one embodiment, the battery is a lithium battery, but may also be other types of batteries.

[0057] Specifically, the temperature acquisition device 40 is connected to a plurality of temperature sensors 30, and is responsible for real-time acquisition of the temperature data measured by each sensor 30, and transmits the data to a subsequent processing unit (such as a computer or a dedicated data recorder, etc.) for analysis and processing. The charging and discharging device 50 is connected to the battery 100 via a power line 60, and the charging and discharging device 50 can charge and discharge the battery 100 according to a set charging and discharging mode (such as constant current charging, constant voltage charging, constant current discharging, etc.), simulating the charging and discharging conditions in actual use, so as to test the heating of the battery under different working conditions. The power line 60 is used to transmit electrical energy, and a special wiring hole is provided on the test tool box 10 for arranging the connection wires of the power line 60 and the temperature sensor 30. In order to prevent heat from being lost through the wiring hole or external air from interfering with the test environment through the wiring hole, a sealing structure is provided at the wiring hole to ensure the stability and sealing of the internal environment of the test tool box. Specifically, the sealing structure can be a sealant.

[0058] The above-mentioned battery heating power testing device realizes the heating power evaluation of the battery 100 by collecting the surface temperature, center temperature, inner surface temperature of the test tool box 10, and internal ambient temperature of the test tool box 10. The testing device is simple, easy to operate, and low in cost, and can simply and efficiently evaluate the battery heating power requirements.

[0059] In one embodiment of the present invention, the test tool box 10 is assembled by splicing. The test tool box 10 preferably adopts a standard square shape to ensure that the battery dissipates heat evenly all around. The material of the test tool box 10 is acrylic, and the structure adopts a splicing type, and each part is connected by screws. Other forms, such as snaps, can also be used to facilitate disassembly and installation. The end plates of the test tool box 10 are connected by threads to ensure the sealing of the device.

[0060] It should be noted that, in the embodiment of the present invention, when the power line 60 is connected, the battery (also called a battery cell) is first placed in the middle of the test tool box 10, and then the power line 60 is connected to the battery cell aluminum bus. Specifically, the power line 60 and the battery cell aluminum bus are connected and fixed with screws to reduce the contact impedance between the battery cell aluminum bus and the conductor (power line 60).

[0061] In one embodiment, the battery is composed of an internal winding core, a shell that wraps the winding core, and two poles extending out of the shell. The temperature rise sensor 30 is arranged at the following locations: Figure 2 Arranging points (01, 02, 03) on the outer surface of the battery. In one embodiment, the points (01, 02, 03) are located at the center of the corresponding surface of the outer surface of the battery; Figure 3 Arrange points for battery coil core (04, 05, 06); Figure 4 and Figure 5 The test device layout is shown, which are arranged on the inner surface (08, 09, 010) of the test tool box 10, inside the test tool box 10 (011, 012, 013), and outside the test tool box 10 (014). The temperature at the corresponding position (distribution point) can be measured through the corresponding distribution points; among them, the distribution points 011, 012, and 013 are at a certain distance from the outer surface of the battery to avoid the influence of the thermal boundary layer on the outer surface of the battery.

[0062] In one embodiment, the test tool box 10 is placed in a temperature chamber, and the distribution point 014 is also a distribution point in the temperature chamber.

[0063] In one embodiment, when the battery is in the shape of a regular hexahedron or a regular cylinder, the side surface of the outer surface of the battery 100 is formed by connecting the first side surface, the second side surface, the third side surface, and the fourth side surface in sequence, the first side surface is opposite to the third side surface and has the same area, and the second side surface is opposite to the fourth side surface and has the same area; point 01 is located on the upper surface of the battery 100, point 02 is located on the first side surface of the battery 100, and point 03 is located on the second side surface of the battery 100; point 08 is located on the first inner surface of the inner surface of the test tool box 10, point 09 is located on the second inner surface of the inner surface of the test tool box 10, and point 010 is located on the top surface of the inner surface of the test tool box 10, the top surface of the inner surface of the test tool box 10 is opposite to the upper surface of the battery 100, and the first inner surface of the test tool box 10 is opposite to the top surface of the test tool box 10. The surface is opposite to the first side surface of the battery 100, the second inner surface of the test tool box 10 is opposite to the second side surface of the battery 100, and the inner surface of the test tool box 10 also includes a third inner surface and a fourth inner surface, which are respectively opposite to the third side surface and the fourth side surface of the battery 100; point 011 is located between the first inner surface of the inner surface of the test tool box 10 and the first side surface of the battery 100, point 012 is located between the second inner surface of the inner surface of the test tool box 10 and the second side surface of the battery 100, and point 013 is located between the top surface of the inner surface of the test tool box 10 and the upper surface of the battery 100; points 04, 05, and 06 are respectively located at the upper, middle, and lower positions of the winding core, and the temperatures of points 04, 05, and 06 are measured and the average value is taken as the center temperature of the winding core, or the center temperature of the battery.

[0064] See also Figure 6In one embodiment, the battery heating power test device is sealed, and the test tool box 10 is wrapped with thermal insulation cotton. Specifically, the wiring holes are wrapped, and the power lines 60 in the temperature box also need to be wrapped to ensure that there is no wind in the test tool box 10 and construct a natural heat dissipation environment.

[0065] See also Figure 7 The embodiment of the present invention further provides a calculation method of a battery heating power test device, which is applied to the battery heating power test device as described above. The method includes steps S01 to S07:

[0066] Step S01 , placing the battery to be tested in the test tool box and leaving it to stand for a preset time, so that the temperature of the battery to be tested is consistent with that of the inside and outside of the test tool box.

[0067] First, place the battery to be tested (i.e., battery 100) in the test tool box 10 and let it stand for a preset time. The purpose of this standing process is to make the temperature of the battery to be tested consistent with that of the inside and outside of the test tool box (the internal ambient temperature of the test tool box and the external ambient temperature of the test tool box) to eliminate the impact of the initial temperature difference on the test results. During the standing process, the temperature sensor 30 continuously monitors the temperature of each part (distribution point). When the temperature change measured by each temperature sensor 30 tends to be stable and the difference is within the allowable error range, it can be considered that the temperature inside and outside the battery 100 and the test tool box 10 has reached a balanced state, and subsequent test operations can be performed at this time.

[0068] Step S02, calculating the convection heat transfer coefficient between the outer surface of the battery to be tested and the internal environment of the test tool box.

[0069] Step S03, calculating the thermal resistance between the winding core and the battery casing of the battery to be tested;

[0070] Step S04, calculating the radiation heat transfer between the battery to be tested and the inner surface of the test tool box;

[0071] Step S05, calculating the convective heat transfer between the battery to be tested and the internal environment of the test tool box;

[0072] Step S06, calculating the change in heat absorption of the battery to be tested during the charge and discharge cycle to obtain the self-heating of the battery to be tested;

[0073] Step S07, calculating the total heat generated by the battery to be tested, where the total heat generated is the sum of the radiation heat transfer, the convection heat transfer and the self-heating.

[0074] The calculation method of the above-mentioned battery heating power test device is based on the principle of thermal balance, and calculates the battery's self-heating, the convective heat transfer between the battery and the internal environment of the test tool box, and the radiation heat transfer between the battery and the inner surface of the test tool box. This method has a small error and high accuracy in calculating the battery's heating power, which can provide an important basis for battery thermal simulation evaluation.

[0075] Specifically, in the embodiment of the present invention, the calculation formula of the convective heat transfer coefficient is:

[0076] h=λNu1 / l; where h represents the convective heat transfer coefficient, Nu1 is the Nusselt number, λ is the thermal conductivity of air, and l is the characteristic length; when calculating the convective heat transfer coefficient between the top surface of the battery outer surface and the internal environment of the test tool box, when the battery is a regular hexahedron, l is 1 / 4 of the circumference of the top surface, and when the battery is a regular cylinder, the diameter of its cross-section circle is selected as the characteristic length l; in one embodiment, 1 / 4 of the circumference of the top surface is uniformly selected as the characteristic length. When calculating the convective heat transfer coefficient between the side surface of the battery outer surface and the internal environment of the test tool box, l is the height of the battery, or the height of the side surface of the battery outer surface.

[0077] Specifically, the determination of the Nusselt number Nu1 requires comprehensive consideration of various factors of the test environment, such as air flow rate, temperature gradient, etc., which can be obtained through relevant empirical formulas or experimental data fitting. The thermal conductivity λ of the air is related to the temperature, humidity and other conditions of the test environment, and can be queried or calculated based on the actual test environment parameters. The characteristic length is usually determined according to the shape and size of the battery. By accurately calculating the convective heat transfer coefficient, it is possible to provide a key parameter basis for the subsequent accurate calculation of convective heat transfer.

[0078] It should be noted that the calculation method for the convective heat transfer coefficient between the outer surface of the battery and the environment is based on the calculation of the convective heat transfer coefficient of natural heat dissipation in a large space. Specifically, the convective heat transfer coefficient of the vertical surface of the battery (battery side) and the horizontal surface of the battery (battery top) need to be calculated separately. The calculation formula is as follows:

[0079] h=λNu1 / l;

[0080] Among them, Nusselt number Nu1 = C (GrPr) m .

[0081] For the vertical surface (side) of the battery:

[0082] When 1.43×10 4 ≤Gr<3×10 9 When C = 0.59, m = 1 / 4;

[0083] When 3×10 9 ≤Gr≤2×10 10When, C = 0.0292, m = 0.39;

[0084] When 2×10 10 <Gr, C = 0.11, m = 1 / 3.

[0085] For the battery horizontal plane (top surface):

[0086] When 10 4 ≤GrPr<10 7 When, C = 0.59, m = 1 / 4;

[0087] When 10 7 ≤GrPr≤10 11 When, C = 0.15, m = 1 / 4.

[0088] Among them, h is the convective heat transfer coefficient; λ is the thermal conductivity of air (obtained by looking up the table according to the ambient temperature); the Nusselt number Nu1 can be calculated according to C, Gr, Pr, m; the calculation formulas of Gr and Pr are as follows respectively. Obtain Gr and Pr through their calculation formulas, then obtain C and m according to the ranges of Gr (and Pr), and further obtain the Nusselt number Nu1.

[0089] Gr = g(α v Δtl 2 ) / V 2 ;

[0090] Coefficient of air expansion: α V = 1 / T m ;

[0091] g: is the acceleration of gravity;

[0092] V: is the kinematic viscosity of air (inherent property, obtained by looking up the table);

[0093] In the formula, T m = 1 / 2(T1 + T2); Δt = (T1 - T2);

[0094] In the formula, T1 is the temperature of the outer surface of the battery cell, T2 is the ambient temperature near the outer surface of the battery cell, that is, the ambient temperature near the outer surface of the battery cell inside the test tooling box 10, or the ambient temperature inside the test tooling box;

[0095] The calculation formula of the Prandtl number Pr is,

[0096] μ is the dynamic viscosity of air, Cp is the specific heat at constant pressure of air; λ is the thermal conductivity of air, l is the characteristic length, which has been described before and will not be elaborated here.

[0097] In the embodiments of the present invention, in combination with Figure 8Battery equivalent thermal resistance model, the thermal resistance calculation formula is:

[0098]

[0099] Where R1 is the thermal resistance between the winding core and the battery casing, T cell is the core center temperature, T surf is the battery surface temperature, T amb is the ambient temperature in the test tool box, h is the convective heat transfer coefficient (i.e., the convective heat transfer coefficient between the outer surface of the battery and the inner environment of the test tool box), A is the outer surface area of ​​the battery (excluding the bottom of the battery, which is insulated), ε is the emissivity of the outer surface of the battery, which can be found in the battery specification, σ is the Stefan-Boltzmann constant, T s To test the inner surface temperature of the tooling box; T s Indicates the surface temperature inside the test tool box where the battery is located.

[0100] Among them, the left side of the thermal resistance calculation formula represents the heat conduction between the core and the outer surface of the battery, and the right side represents the sum of convective heat transfer and radiation heat transfer. Convective heat transfer refers to the convective heat transfer between the battery and the internal environment of the test tool box, and radiation heat transfer refers to the radiation heat transfer between the battery and the inner surface of the test tool box.

[0101] Specifically, in the embodiment of the present invention, the formula for radiation heat transfer is:

[0102]

[0103] Wherein, Q1 represents the radiation heat transfer between the battery and the inner surface of the test tool box. It can be understood that in one embodiment, when the battery is a regular hexahedron or a regular cylinder, Q1 = εσ[A1(T 01 4 -T 010 4 )+2A2(T 02 4 -T 08 4 )+2A3(T 03 4 -T 09 4 )];

[0104] Wherein, A1 is the area of ​​the upper surface of the battery outer surface, A2 is the area of ​​the first side surface of the battery outer surface, and A3 is the area of ​​the second side surface of the battery outer surface; T 01 is the temperature at point 01, T 010 is the temperature at point 010, T 02 is the temperature at point 02, T 08 is the temperature at point 08, T 03is the temperature at point 03, T 09 is the temperature at point 09.

[0105] Specifically, in the embodiment of the present invention, the calculation formula of the convective heat transfer is:

[0106] Q2=hA(T surf -T amb );

[0107] Where Q2 represents the convective heat transfer between the battery and the internal environment of the test tool box, h represents the convective heat transfer coefficient between the outer surface of the battery and the internal environment of the test tool box, A represents the outer surface area of ​​the battery (excluding the bottom surface), T amb To test the internal ambient temperature of the tooling box.

[0108] It can be understood that, in one embodiment, when the battery is in the shape of a regular hexahedron or a regular cylinder, Q2=h1A1(T 01 -T 013 )+2h2A2(T 02 -T 011 )+2h3A3(T 03 -T 012 );

[0109] Among them, T 011 、T 012 、T 013 They are the temperatures at points 011, 012, and 013 respectively; h1 is the convection heat transfer coefficient between the top surface of the battery outer surface and the internal environment of the test tool box, or the convection heat transfer coefficient between points 01 and 013; h2 is the convection heat transfer coefficient between the first side surface of the battery outer surface and the internal environment of the test tool box, or the convection heat transfer coefficient between points 02 and 011, and its value is; h3 is the convection heat transfer coefficient between the first side surface of the battery outer surface and the internal environment of the test tool box, or the convection heat transfer coefficient between points 03 and 012; it can be understood that h2=h3.

[0110] In the embodiment of the present invention, the calculation formula of the self-heating is:

[0111] Q3=C P1 M(dT cell / d t );

[0112] Among them, Q3 represents the change in the internal energy of the battery, M represents the mass of the battery, and C p1 represents the specific heat capacity of the battery, dT cell / d trepresents the derivative of the core center temperature with time, or the rate of change of the core center temperature with time; for batteries without temperature rise points (points) arranged on the core, T cell The value is T cell =T surf +(Q1+Q2)R1.

[0113] In order to verify the accuracy of the patented test device and calculation method of this invention, the measured and simulated data under different working conditions are compared and verified. Figures 9 to 13 .

[0114] Fig. 9 This is a schematic diagram comparing the measured and simulated temperature rise of the battery's natural heat dissipation. Figure 1 The battery heating power test device shown can actually measure the center temperature of the battery core (corresponding to Fig. 9 "Measured core") in the battery surface temperature (corresponding to Fig. 9 The total heat generated by the above calculation is imported into the corresponding simulation model, and the center temperature of the battery core is obtained by thermal simulation (corresponding to Fig. 9 The "patented calculation core" in the battery and the battery surface temperature (corresponding to Fig. 9 The total heat generated by the battery is calculated using the Bernardi formula and then imported into the corresponding simulation model. The center temperature of the battery core is obtained through thermal simulation (corresponding to Fig. 9 "Bernardi formula for calculating the winding core") and the battery surface temperature (corresponding to Fig. 9 "Bernardi formula for calculating blue film" in the paper); compare the measured temperature and simulated temperature errors of the battery core and battery blue film (outer surface) respectively. Fig. 9 It can be seen that the curve fitting degree between the temperature obtained by simulation and the measured temperature after calculation by Bernardi formula is poor in the whole charge and discharge cycle process; the loss (total calorific value) is calculated by the present invention, and then the curve fitting degree between the temperature obtained by simulation and the measured temperature is high in the whole charge and discharge cycle process, indicating that the heat power calculation accuracy of the present invention is high; wherein, Fig. 9 In the figure, the blue film refers to the outer surface of the battery.

[0115] Fig.10 Schematic diagram of a battery air-cooling test experimental device, including a chassis 80 , thermal insulation cotton 90 , an air duct partition 91 , a fan 92 , a battery 100 , and an air inlet 81 ; the battery 100 is placed in the chassis 80 .

[0116] pass Fig.10 The battery air cooling test device can actually measure the center temperature of the battery core (corresponding to Fig.11 "Measured core") in the battery surface temperature (corresponding to Fig.11The total heat generated by the battery is relatively stable under different working conditions. The total heat generated by the above calculation is imported into Fig.10 In the corresponding simulation model, the center temperature of the battery core is obtained by thermal simulation (corresponding to Fig.11 The "patented calculation core" in the battery and the battery surface temperature (corresponding to Fig.11 The total heat generated by the battery is calculated using the Bernardi formula and then imported into Fig.10 In the corresponding simulation model, the center temperature of the battery core is obtained by thermal simulation (corresponding to Fig.11 "Bernardi formula for calculating the winding core") and the battery surface temperature (corresponding to Fig.11 "Bernardi formula for calculating blue film" in the paper); compare the measured temperature and simulated temperature errors of the battery core and battery blue film (outer surface) respectively. Fig.11 It can be seen that the curve fitting degree between the temperature obtained by simulation and the measured temperature after calculation by Bernardi formula is poor in the whole charge and discharge cycle process; the loss (total calorific value) is calculated by the present invention, and then the curve fitting degree between the temperature obtained by simulation and the measured temperature is high in the whole charge and discharge cycle process, indicating that the heat power calculation accuracy of the present invention is high; wherein, Fig.11 In the figure, the blue film refers to the outer surface of the battery.

[0117] Fig.12 The above is a comparison of the heating power (total calorific value) curves calculated by using ARC (accelerated calorimeter) and the present invention (patent) during the constant power discharge process of the battery. Fig.13 The above is a constant power charging process of the battery. The heat generation power (total calorific value) curve calculated by ARC (accelerated calorimeter) is compared with that of the present invention. The graphical results further show that the power loss curve calculated by the present invention has high accuracy (i.e., it has a higher degree of fit with the ARC measured curve).

[0118] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A battery heating power testing device, characterized in that: The test tool box includes a test tool box, an insulation layer wrapped around the outside of the test tool box, multiple temperature sensors arranged in the test tool box, a temperature acquisition device connected to the multiple temperature sensors, a charging and discharging device connected to a battery, a power line, and a temperature sensor connecting line. The power line is used to connect the charging and discharging device and the battery. The battery is accommodated in the test tool box. The test tool box is provided with wiring holes for arranging the power lines and the temperature sensors. A sealing structure is provided at the wiring holes. The multiple temperature sensors are respectively used to obtain the battery surface temperature, the battery center temperature, the inner surface temperature of the test tool box, the internal ambient temperature of the test tool box, and the external ambient temperature of the test tool box.

2. The battery heating power testing device according to claim 1, characterized in that: The test tool box is assembled by splicing.

3. The battery heating power testing device according to claim 1, characterized in that: The wiring holes are provided on the side or top surface of the test tool box.

4. The battery heating power testing device according to claim 1, characterized in that: The sealing structure is a sealant.

5. A calculation method for a battery heating power test device, characterized in that: Applied to the battery heating power testing device according to any one of claims 1 to 4, the method comprising: Placing the battery to be tested in the test tool box and leaving it to stand for a preset time, so that the temperature of the battery to be tested and the temperature inside and outside of the test tool box are consistent; Calculating the convection heat transfer coefficient between the outer surface of the battery to be tested and the internal environment of the test tool box; Calculating the thermal resistance between the winding core and the battery housing of the battery to be tested; Calculating the radiation heat transfer between the battery to be tested and the inner surface of the test tool box; Calculating the convective heat transfer between the battery to be tested and the internal environment of the test tool box; Calculating the change in heat absorption of the battery to be tested during the charge and discharge cycle to obtain the self-heating of the battery to be tested; The total heat generated by the battery to be tested is calculated, where the total heat generated is the sum of the radiation heat transfer, the convection heat transfer and the self-heating.

6. The calculation method of the battery heating power test device according to claim 5, characterized in that: The calculation formula of the convective heat transfer coefficient is: h=λNu1 / l; Among them, h represents the convective heat transfer coefficient, Nu1 is the Nusselt number, λ is the thermal conductivity of air, and l is the characteristic length.

7. The calculation method of the battery heating power test device according to claim 6, characterized in that: The calculation formula of the thermal resistance is: Where R1 is the thermal resistance between the winding core and the battery casing, T cell is the core center temperature, T surf is the battery surface temperature, T amb is the ambient temperature in the test box, h is the convective heat transfer coefficient, A is the outer surface area of ​​the battery excluding the bottom, ε is the emissivity of the outer surface of the battery, σ is the Stefan-Boltzmann constant, T s To test the inner surface temperature of the tooling box; the right side of the thermal resistance calculation formula is the sum of convective heat transfer and radiation heat transfer.

8. The calculation method of the battery heating power test device according to claim 7, characterized in that: The formula for radiation heat transfer is: Q1=εσA(T surf 4 -T s 4 ); Where Q1 represents the radiation heat transfer between the battery and the inner surface of the test tool box.

9. The calculation method of the battery heating power test device according to claim 8, characterized in that: The calculation formula for the convective heat transfer is: Q2=hA(T surf -T amb ); Among them, Q2 represents the convection heat transfer between the battery and the internal environment of the test tooling box.

10. The calculation method of the battery heating power test device according to claim 9, characterized in that: The calculation formula for the self-heating is: Q 3＝ C P1 M(dT cell / d t ); Wherein, Q3 represents the change in the internal energy of the battery, M represents the mass of the battery, and C p1 represents the specific heat capacity of the battery, dT cell / d t represents the derivative of the core center temperature and time; for batteries without temperature rise points (points) arranged on the core, T cell The value is T cell =T surf +(Q1+Q2)R1.

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