Lithium battery calorific value testing device

Abstract

The invention discloses a device for testing the calorific value of a lithium battery. The device comprises a liquid-cooled heat exchanger, an Agilent thermodetector, a constant-temperature water bath box, a discharger, a peristaltic pump and a thermocouple, the liquid-cooled heat exchanger is divided into an upper piece and a lower piece which are split, the lithium battery to be tested is totally coated, each heat exchanger adopts a double-layer metal plate, the outer side metal plate is coated with a heat insulation material, a pipeline for enabling a heat exchange working medium to flow is arranged between the double-layer metal plates, and an inlet and an outlet of the pipeline are positioned at two ends of the heat exchanger; the inlet and the outlet of the pipeline are respectively provided with a small hole for placing a thermocouple, and the surface of the inner side of the heat exchanger contacted with the lithium battery is provided with a slot communicated with the outside for inserting the thermocouple to measure the temperature of the surface of the lithium battery. According to the invention, the temperature of the battery under a high-rate discharge working condition can be controlled within a safe range, the heating value of the battery is monitored in real time, the heating test research of the lithium battery is realized by using high-precision measurement equipment, and the lithium battery has the characteristics of high precision, good following performance and the like.

Description

Technical Field

[0001] The invention relates to the technical field of lithium batteries, in particular to a device for testing the heat output of lithium batteries. Background Art

[0002] At present, lithium batteries are widely used in various fields such as aerospace, military industry, power electronics, etc. With the continuous improvement of battery performance, more stringent requirements are also put forward for battery thermal management. The increase in battery pack temperature will affect the working life and safety of the equipment, so appropriate means are needed to manage the thermal performance of the battery pack, and thermal characteristic parameters such as battery heat generation are important parameters for thermal management.

[0003] The requirement for ensuring the accuracy of the lithium battery calorific value test is to control the heat leakage so that all the heat generated by the lithium battery discharge is used for the temperature rise of the lithium battery itself or the temperature rise of the heat exchange medium. The existing calorific value test methods mainly include adiabatic calorimetry, which creates a nearly adiabatic environment for the lithium battery by tracking the surface temperature of the lithium battery. However, the heat cannot be dissipated, resulting in excessively high battery temperatures, which poses certain safety hazards. At the same time, the low accuracy of the equipment under high-rate discharge conditions leads to untimely heat tracking, and there is a large temperature difference between the external temperature and the surface of the lithium battery, which causes errors. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a device for testing the heat generation of a lithium battery, which improves the accuracy of the heat generation test of the lithium battery while ensuring the safety of the lithium battery.

[0005] The present invention is implemented as follows: a test device for the heat generation of a lithium battery comprises a liquid-cooled heat exchanger, an Agilent thermometer, a constant temperature water bath, a discharger, a peristaltic pump, and a thermocouple;

[0006] The liquid-cooled heat exchanger is a split type consisting of two upper and lower parts, which completely cover the lithium battery to be tested. Each heat exchanger uses a double-layer metal plate, and the outer metal plate is wrapped with heat insulation material. A pipeline for the flow of heat exchange medium is set between the double-layer metal plates. The inlet and outlet of the pipeline are located at both ends of the heat exchanger. Small holes for placing thermocouples are set at the inlet and outlet of the pipeline. The surface of the inner side of the heat exchanger that contacts the lithium battery is opened with a groove that communicates with the outside world, which is used to insert a thermocouple to measure the surface temperature of the lithium battery;

[0007] A constant temperature water bath is connected between the inlet and outlet of the pipeline to ensure that the temperature of the liquid at the inlet is constant;

[0008] A peristaltic pump is arranged between the constant temperature water bath and the inlet of the pipeline to control the flow speed of the heat exchange medium in the pipeline;

[0009] The discharge meter is connected to the tab of the lithium battery to be tested and is used to set the discharge condition and the termination voltage;

[0010] Agilent temperature meter, measuring the temperature of heat exchange fluid and battery.

[0011] A computer is also provided, which is connected to the Agilent thermometer and is used for data export and processing and analysis.

[0012] The double-layer metal plate is made of aluminum, copper or aluminum alloy.

[0013] The heat insulating material wrapped on the outer metal plate is a rubber material with low thermal conductivity.

[0014] The pipeline is a serpentine pipeline.

[0015] The split upper and lower parts of the liquid-cooled heat exchanger are of the same size and symmetrical structure, wrapping the single lithium battery and fitting tightly.

[0016] The advantages and technical effects of the present invention are as follows:

[0017] (1) All the heat generated by the lithium battery is removed by the heat exchange medium, and the heat generation of the lithium battery is calculated by calculating the temperature rise of the heat exchange medium, which overcomes the disadvantage of large errors in the previous high-rate battery heat generation test;

[0018] (2) It can improve the safety of lithium batteries in heat generation tests;

[0019] (3) Adaptable heat exchangers are designed for lithium batteries of different sizes, and different flow channels are designed inside the heat exchanger to reduce heat leakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of a test device for the heat generation of a lithium battery of the present invention;

[0021] Figure 2 Schematic diagram of a liquid-cooled heat exchanger of a lithium battery heat generation test device of the present invention;

[0022] Figure 3 It is a schematic diagram of the interior of a liquid-cooled heat exchanger of a lithium battery heat generation test device of the present invention. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation methods described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] In the description of the present invention, it should be noted that the orientations or positional relationships indicated by terms such as “upper”, “middle”, “lower”, “inside”, “outside”, and “both sides” are based on the orientations or positional relationships shown in the accompanying drawings, and are only simplified descriptions for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0025] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] The electrical devices, controllers, etc. described in the present invention are all conventionally configured, and the electrical connection method is also conventionally connected.

[0027] like Figure 1 As shown, the test device for the heat generation of a lithium battery of the present invention comprises a liquid-cooled heat exchanger 1, an Agilent thermometer 2, a constant temperature water bath 3, a discharger 4, a peristaltic pump 5, and a thermocouple;

[0028] The liquid-cooled heat exchanger 1 is a split type with two upper and lower pieces, which completely cover the lithium battery to be tested. Each heat exchanger uses a double-layer metal plate, and the outer metal plate is wrapped with a heat-insulating material. A pipe 6 for the flow of heat exchange medium is arranged between the double-layer metal plates. The inlet 11 and the outlet 12 of the pipe 6 are located at both ends of the heat exchanger. Small holes 13 and 14 for placing thermocouples are arranged at the inlet and outlet of the pipe 6. The surface of the inner side of the heat exchanger that contacts the lithium battery is provided with a groove 15 that communicates with the outside world, which is used to insert a thermocouple to measure the surface temperature of the lithium battery;

[0029] A constant temperature water bath 3 is connected between the inlet 11 and the outlet 12 of the pipeline 6 to ensure that the temperature of the liquid at the inlet 11 is constant;

[0030] A peristaltic pump 5 is provided between the constant temperature water bath 3 and the inlet 11 of the pipeline 6 to control the flow speed of the heat exchange medium in the pipeline 6;

[0031] The discharge instrument 4 is connected to the tab of the lithium battery to be tested and is used to set the discharge condition and the termination voltage;

[0032] Agilent thermometer 2, measuring the temperature of the heat exchange fluid and the battery.

[0033] A computer 7 is also provided, which is connected to the Agilent thermometer 2 and is used for data export and processing and analysis.

[0034] The double-layer metal plate is made of aluminum, copper or aluminum alloy.

[0035] The heat insulating material wrapped on the outer metal plate is a rubber material with low thermal conductivity.

[0036] The split upper and lower parts of the liquid-cooled heat exchanger 1 are of the same size and symmetrical structure, wrapping the single lithium battery and fitting tightly.

[0037] The principle of the present invention is that the battery in the discharge state is tightly fitted with the liquid-cooled heat exchanger, which is composed of two split parts, the upper and lower parts, and the lithium battery is fully covered by the split heat exchanger. The flowing heat exchange medium in the heat exchanger takes away all the heat generated by the battery, controls the heat leakage, and measures the temperature difference of the heat exchange medium at the inlet and outlet of the heat exchanger and integrates it to obtain the heat generated by the lithium battery.

[0038] The calculation formula of heating power is as follows:

[0039] Φ=ρc p vAdT (1-1)

[0040] Where: Φ is the heating power of the battery; ρ is the density of the heat exchange medium; c p is the specific heat capacity of the heat exchange medium; v is the flow rate of the heat exchange medium; A is the cross-sectional area of ​​the heat exchanger channel; dT is the temperature difference between the fluid at the outlet and the fluid at the inlet of the heat exchanger, which can be measured by a thermocouple.

[0041] The heat exchanger of the present invention takes into account both heat exchange efficiency and practical applicability. The heat exchanger has high heat exchange efficiency, high sealing, is easy to process, can cover the entire battery surface, and the inlet and outlet are kept away from the pole ear. There are certain differences between the heat exchanger of the present invention and the traditional radiator. The fundamental purpose of the traditional radiator is to dissipate heat from the product, so the materials are mostly made of metals such as aluminum and copper with high thermal conductivity. The heat exchanger of the present invention is a carrier of heat transfer in a certain sense. The heat generated by the battery is transferred to the heat exchange medium through the inner aluminum plate of the heat exchanger. The flowing heat exchange medium continuously takes away the heat generated by the battery, which can improve the safety of the lithium battery. Part of the heat is transferred to the upper aluminum plate of the heat exchanger, and finally the heat is transferred to the air. The heat exchanger of the present invention can be customized to different heat exchanger sizes according to the size of the lithium battery.

[0042] The outermost part of the heat exchanger of the present invention in contact with the air is made of rubber material with low thermal conductivity to prevent heat from being transferred to the outside and causing large errors in the experimental results. The lower aluminum plate is still made of metal aluminum material to ensure that all the heat generated by the battery can enter the cooling medium in the heat exchanger.

[0043] like Figure 2 The figure shows the three-dimensional modeling diagram of the heat exchanger. The inlet and outlet of the heat exchanger are located at both ends. Small holes are made above the inlet and outlet for placing thermocouples to measure the inlet and outlet temperatures. The heat exchanger material is aluminum alloy, which has high thermal conductivity. The heat generated by the battery is first transferred to the aluminum alloy. The aluminum alloy with high thermal conductivity can transfer the heat to the fluid in the flow channel in a very short time.

[0044] The simulation proves that the different pipeline structures have little effect on the battery heat generation test results. Therefore, the traditional serpentine channel structure was selected for the experiment. After experimental verification, the heat exchanger was used to indirectly test the battery heat generation, and the battery temperature was always controlled within a reasonable range during the experiment. The serpentine flow channel structure heat exchanger meets the temperature control requirements during the battery discharge process and can accurately measure the battery heat generation. Figure 3 The figure shows the flow channel structure and dimensions of a heat exchanger suitable for a certain type of lithium battery. The channel height is 3mm, the channel width is 5mm, and the thickness of the upper and lower heat exchanger plates is 2mm. Heat exchangers are attached to both sides of the battery. After the outlet and inlet temperature difference is measured and the heat generation is calculated, the heat generation measured by the upper and lower heat exchangers needs to be added together to obtain the total heat generation of the battery.

[0045] In the heat generation test, two heat exchangers of the same size and symmetrical structure are used to wrap the single battery to ensure a tight fit. The outside is wrapped with insulation material to reduce heat leakage.

[0046] In this embodiment, Figure 1 As shown, a total of five thermocouples are set up for the calorific value test, among which thermocouple Temp1 is used to measure the fluid temperature at the inlet. Thermocouple Temp2 and thermocouple Temp3 probes are placed at the outlets of the upper and lower heat exchangers respectively to measure the fluid temperature at the outlet. Thermocouple Temp4 and thermocouple Temp5 are placed on one side of the battery respectively to observe the temperature change of the battery. The surface of the heat exchanger is grooved to place the thermocouples to ensure the close fit between the battery and the heat exchanger. Set the discharge condition and termination voltage on the discharge equipment. When the battery starts to discharge, turn on the Agilent data acquisition device to record the temperature every second until the battery is discharged to the termination voltage to end the experiment. Finally, export the data and process and analyze it.

[0047] The present invention can control the battery temperature under high-rate discharge conditions within a safe range, monitor the heat generation of the battery in real time, and realize the lithium battery heating test research by using high-precision measuring equipment, which has the characteristics of high accuracy, good followability, etc. The present invention has excellent effect on the heat generation test of lithium batteries under high-rate discharge conditions.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A lithium battery heat generation test device, characterized in that: It includes a liquid-cooled heat exchanger (1), an Agilent temperature measuring instrument (2), a constant temperature water bath (3), a discharge instrument (4), a peristaltic pump (5), and a thermocouple; The liquid-cooled heat exchanger (1) is a split type upper and lower two-piece heat exchanger that completely covers the lithium battery to be tested. Each heat exchanger uses a double-layer metal plate, and the outer metal plate is wrapped with a heat insulating material. A pipe (6) for the heat exchange medium to flow is arranged between the double-layer metal plates. The inlet (11) and outlet (12) of the pipe (6) are located at both ends of the heat exchanger. Small holes for placing thermocouples are arranged at the inlet and outlet of the pipe (6). The surface of the inner side of the heat exchanger that contacts the lithium battery is provided with a groove (15) that communicates with the outside and is used to insert a thermocouple to measure the surface temperature of the lithium battery. A constant temperature water bath (3) is connected between the inlet (11) and the outlet (12) of the pipeline (6) to ensure that the temperature of the liquid at the inlet (11) is constant; A peristaltic pump (5) is arranged between the constant temperature water bath (3) and the inlet (11) of the pipeline (6) to control the flow speed of the heat exchange medium in the pipeline (6); A discharge instrument (4), connected to the tab of the lithium battery to be tested, for setting the discharge condition and the termination voltage; Agilent thermometer (2) measures the temperature of the heat exchange fluid and the battery.

2. The device for testing the heat generation of a lithium battery according to claim 1, characterized in that: A computer (7) is also provided, and the computer (7) is connected to the Agilent thermometer (2) and is used for data export and processing and analysis.

3. The device for testing the heat generation of a lithium battery according to claim 1, characterized in that: The double-layer metal plate is made of aluminum, copper or aluminum alloy.

4. The device for testing the heat generation of a lithium battery according to claim 1, characterized in that: The heat insulating material wrapped on the outer metal plate is a rubber material with low thermal conductivity.

5. The lithium battery heat generation testing device according to claim 1, characterized in that: The pipeline (6) is a serpentine pipeline.

6. The device for testing the heat generation of a lithium battery according to claim 1, characterized in that: The split upper and lower parts of the liquid-cooled heat exchanger (1) are of the same size and symmetrical structure, and wrap the single lithium battery in a tightly fitted manner.

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