Automatic testing device for temperature entropy coefficient of battery

Abstract

The utility model relates to the technical field of lithium battery testing, in particular to a battery temperature entropy coefficient automatic testing device, which comprises a temperature test box, a charging and discharging module, a data acquisition module and a control module, the temperature test box, the charging and discharging module and the data acquisition module are in communication connection with the control module, and an inner cavity of the temperature test box is divided into at least two layers. The temperature can be independently controlled; the acquisition precision of the voltage data is 0.1 mv; the charging and discharging module is used for adjusting the state of charge (SOC) of the tested single battery; and the control module is used for acquiring the voltage and temperature data acquired by the data acquisition module, controlling the automatic linkage test, and calculating the temperature entropy coefficient of the battery according to the acquired voltage and temperature data. According to the utility model, the automatic parallel test of the battery temperature entropy coefficients of a plurality of tested single batteries can be completed, and the test accuracy is high.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium battery testing, in particular to an automatic testing device for the temperature entropy coefficient of a battery. Background Technique

[0002] Monitoring results of air pollution and the greenhouse effect show that the exhaust gas emitted by fuel vehicles is one of the main sources of the greenhouse gas CO2 and an important factor causing air pollution. To solve the problems related to the exhaust emissions of fuel vehicles, hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), and fuel cell vehicles (FCVs) have received increasing attention due to their lower or even zero exhaust emissions and higher energy conversion efficiency. Lithium-ion batteries have currently become the preferred energy storage modules for HEVs, PHEVs, and BEVs, etc., due to their low self-discharge rate, high energy / power density, and long cycle life.

[0003] However, the electrochemical characteristics of lithium-ion batteries are greatly affected by temperature. For example, when operating at low temperatures, the available capacity and output power of lithium-ion batteries will significantly decrease, and it may even cause the vehicle to fail to start; while when the operating temperature is high, the cycle life of lithium-ion batteries will be significantly shortened. More importantly, hundreds or thousands of battery cells are arranged in a specific series-parallel form in the battery pack. Due to the temperature difference caused by the physical position difference of each battery cell, the temperature difference will lead to performance differences among each cell, and ultimately the performance differences among the battery cells will result in a reduction in the available capacity and cycle life of the entire battery system. Therefore, in order to enable the battery pack to operate within an ideal temperature range and at the same time try to maintain the temperature uniformity among the battery cells, it is necessary to develop an effective and reliable thermal management system (TMS).

[0004] During the development of the TMS, it is necessary to obtain key parameters such as the heat generation power and temperature of the battery under specific working conditions. An effective method for obtaining the heat generation power of the battery is to calculate according to the Bernardi formula:

[0005]

[0006] In the formula, q is the heat generation power of the battery, with the unit of W; I is the battery current, with the unit of A; OCV is the open-circuit voltage of the battery, with the unit of V; U is the working voltage of the battery, with the unit of V; T is the ambient temperature, with the unit of Kelvin; is the temperature entropy coefficient, with the unit of V / K.

[0007] As can be seen from the above, the key to calculating the heat generation of the battery by the Bernardi formula is to accurately obtain the temperature-entropy coefficient of the battery. In the prior art, the temperature-entropy coefficient of the battery is obtained by first testing the open-circuit voltage of the battery at different ambient temperatures and then calculating the rate of change of the open-circuit voltage with respect to temperature. However, this method has many deficiencies:

[0008] First, the acquisition of the open-circuit voltage usually requires a long time of static placement, and the test period is as long as several months, resulting in low test efficiency;

[0009] Second, the traditional method is manual testing. The battery cell under test needs to be placed in a temperature test chamber, and the temperature test chamber provides a stable ambient temperature. When changing the ambient temperature or adjusting the SOC, the temperature test chamber needs to be opened. During the process of opening the temperature test chamber, the ambient temperature of the battery cell under test will change, which will further cause fluctuations in the open-circuit voltage. Such subtle fluctuations may bring non-negligible interference to the test results;

[0010] Third, the rate of change of the open-circuit voltage with respect to temperature is usually small. If only relying on the experience of the tester to judge, the test accuracy is not high enough, resulting in a large deviation between the calculated value and the measured value of the heat generation power;

[0011] Fourth, the temperature determination of the battery cell under test is not precise enough, which will also cause deviation to the test results. Utility Model Content

[0012] The utility model provides an automatic test device for the temperature-entropy coefficient of a battery, which can automatically complete data acquisition and recording in the test process of the temperature-entropy coefficient, improve the test efficiency, reduce the workload and test cost of the tester, and greatly improve the accuracy of the test results at the same time.

[0013] The present application provides the following technical solutions:

[0014] An automatic test device for the temperature-entropy coefficient of a battery, comprising a temperature test chamber, a charge and discharge module, a data acquisition module and a control module. The temperature test chamber, the charge and discharge module, and the data acquisition module are communicatively connected to the control module. Among them,

[0015] The temperature test chamber is used to adjust the ambient temperature of the battery cell under test;

[0016] The data acquisition module is used to acquire the voltage and temperature of the battery cell under test;

[0017] The charge and discharge module is used to adjust the SOC of the battery cell under test;

[0018] The control module is used to obtain voltage and temperature data, control the automatic linkage test, and calculate the temperature-entropy coefficient of the battery according to the obtained voltage and temperature data.

[0019] Technical principle: The battery under test is placed in a temperature test chamber, and the control module controls a variety of instrument equipment to complete the automated test of the battery temperature entropy coefficient, including controlling the charge and discharge process of the battery cell under test to adjust the SOC, obtaining the test data of the battery cell in real time through the data acquisition module, controlling the temperature test chamber in real time to adjust the ambient temperature, and monitoring the stability of the ambient temperature through the data acquisition module to ensure that the test data is obtained under the required ambient temperature conditions.

[0020] Beneficial effects: It realizes precise adjustment and real-time monitoring of ambient temperature and battery SOC, and can realize automatic testing under various temperatures and various SOC conditions, which reduces the workload of testers and improves test efficiency. At the same time, the data acquisition module ensures the accuracy of test results.

[0021] Furthermore, the battery temperature entropy coefficient includes test results of the tested battery cells under different ambient temperatures and different SOC conditions, where the different ambient temperatures include high temperature, normal temperature and low temperature, and the different SOC conditions include 0, 20%, 40%, 60%, 80% and 100%.

[0022] Beneficial effects: The device can complete the temperature entropy coefficient test under various ambient temperatures and various SOC conditions at one time, and can provide comprehensive and accurate design data for the development of thermal management systems.

[0023] Furthermore, the temperature test box has a temperature adjustment range of -30°C to 60°C, and the inner cavity of the temperature test box is divided into at least two layers, and different layers can be independently temperature controlled.

[0024] Beneficial effects: According to the requirements of GB / T 31486-2015 Electrical Performance Requirements and Test Methods for Power Batteries for Electric Vehicles, power batteries need to complete discharge performance tests at ambient temperatures of -20°C and 55°C. The temperature adjustment range of the temperature test chamber covers this requirement. At the same time, the temperature test chamber is set up with multiple layers of independent temperature control to meet the requirements of testing multiple battery cells at the same time. Different layers can be used to place different battery cells and set the ambient temperature independently. Parallel testing shortens the test time and improves the test efficiency.

[0025] Furthermore, the data acquisition module is used to collect temperature and voltage data, and the acquisition accuracy of voltage data is 0.1mv.

[0026] Beneficial effects: The data acquisition module collects the temperature and voltage data of the tested battery cell, wherein a 16-bit resolution ADC is used for the voltage data to ensure that the acquisition accuracy can reach the fifth decimal place, which greatly improves the accuracy of the voltage data and is conducive to the accurate calculation of the battery temperature entropy coefficient.

[0027] Further, the control module saves the temperature and voltage data at preset intervals, and the test data can be exported as an EXCEL file.

[0028] Beneficial effects: The data throughout the test process is automatically saved and can be exported as an EXCEL file for further analysis.

[0029] Further, the battery cells under test include cylindrical batteries, square batteries, and pouch batteries.

[0030] Beneficial effects: This device can support the testing of battery cells in various packaging forms.

[0031] Further, at least two battery cells can be tested simultaneously.

[0032] Beneficial effects: Through the hierarchical design of the incubator and the configuration of corresponding channels in the data acquisition module, parallel testing of battery cells under various different working conditions can be achieved, improving the testing efficiency.

[0033] Further, the data acquisition module allocates 1 voltage channel, 5 temperature channels, and 1 charge and discharge channel to each battery cell under test.

[0034] Beneficial effects: 1 voltage channel completes the voltage sampling of the battery cell under test, 1 charge and discharge channel monitors the charge and discharge current rate of the battery cell, and 5 temperature channels complete the temperature sampling of the battery cell under test. The accuracy of temperature sampling is characterized by calculating the average difference of the 5 temperature sampling data.

[0035] Further, a matching temperature sensor layout scheme is designed according to the type of the battery cell under test.

[0036] Beneficial effects: The heat generation distribution of battery cells in different packaging forms is also different, so different temperature sampling schemes need to be considered. For example, the temperature sensors of pouch batteries and square shell batteries are arranged at the center and four corners of the upper surface of the battery, and the temperature sensors of cylindrical batteries are arranged on the top surface, bottom surface, upper middle part of the side surface, middle part of the side surface, and lower middle part of the side surface of the cylindrical shell to obtain more realistic temperature sampling results. Description of the Drawings

[0037] Figure 1 is a schematic structural diagram of an automatic battery temperature-entropy coefficient testing device of the present utility model;

[0038] Figure 2 is a schematic diagram of parallel testing of multiple battery cells in the second embodiment of the present utility model. Detailed Description of the Preferred Embodiments

[0039] The following is a further detailed description through specific embodiments:

[0040] The markings in the attached drawings of the specification include: the battery cell under test 1, the temperature test chamber 2, the charge and discharge connection wires 3, the charge and discharge equipment 4, the data acquisition connection wires 5, the data acquisition instrument 6, the control signal wire 7, and the control module 8.

[0041] Embodiment 1

[0042] As Figure 1 shown, an automated test device for the temperature-entropy coefficient of a battery includes a temperature test chamber 2, charge and discharge equipment 4, a data acquisition instrument 6, and a control module 8. Among them, devices such as the temperature test chamber 2, the charge and discharge equipment 4, and the data acquisition instrument 6 can be connected to the control module 8 through various hardware interfaces, including GPIB, LAN, USB, etc., to complete real-time data transmission and interactive communication. In this embodiment, the charge and discharge equipment 4 is a CTP2-6-300 3ISO with 6V 300A, and the data acquisition instrument 6 is a HIOKI LR8450, which is connected to the control module 8 through a USB interface.

[0043] The temperature test chamber 2 adjusts the ambient temperature of the battery cell under test 1 according to the instructions of the control module 8. The temperature adjustment range is from -30°C to 60°C, meeting the requirements of the national standard for discharge performance testing. The inner cavity of the temperature test chamber 2 is used to place the battery cell under test 1, which is divided into at least two layers, and each layer can be independently temperature-controlled. In actual use, different types of battery cells under test 1 can be placed in different layers and the ambient temperature can be independently set. The temperature test chamber 2 is connected to the control module 8 through the control signal wire 7.

[0044] The charge and discharge equipment 4 charges or discharges the battery cell under test 1 according to the instructions of the control module 8 to complete the adjustment of the state of charge (SOC) of the battery cell under test 1. A set of charge and discharge equipment 4 is required for each battery cell under test 1, and the battery cell under test 1 is connected to the charge and discharge equipment 4 through the charge and discharge connection wires 3. The charge and discharge equipment 4 is connected to the control module 8 through the control signal wire 7.

[0045] The data acquisition instrument 6 is communicatively connected to the control module 8 through the control signal line 7 and is connected to the battery cell under test 1 through the data acquisition connection line 5, and is used to collect the voltage and temperature data of the battery cell under test. The resolution of the voltmeter is 16 bits, ensuring that the voltage acquisition accuracy can reach 0.1 mv. For each battery cell under test, 1 voltage channel is allocated to sample the voltage of the battery cell under test, 1 charge and discharge channel monitors the charge or discharge current rate of the battery cell, and 5 temperature channels complete the temperature sampling of the battery cell under test. The accuracy of the temperature sampling is characterized by calculating the mean difference of the 5 temperature sampling data. Since there are various forms of packaging for battery cells, including cylindrical, square, and soft-pack, etc., the heat generation distribution of different packaging forms is also different. Therefore, it is necessary to design a corresponding temperature sensor layout scheme according to the packaging form. For example, the temperature sensors of the soft-pack battery and the square shell battery are arranged at the center and four corners of the upper surface of the battery, and the temperature sensors of the cylindrical battery are arranged on the top surface, bottom surface, upper middle part of the side surface, middle part of the side surface, and lower middle part of the side surface of the cylindrical shell to obtain more realistic temperature sampling results. The temperature sensor includes a sensor body and a fixing part. The fixing part uses a U-shaped buckle to clamp the temperature sensor. The bottom of the fixing part is provided with an adhesive surface, and the adhesive surface is coated with glue, or a magnetic attraction surface is provided to be quickly fixed at the position where the temperature sensor needs to be arranged through magnetic attraction.

[0046] The control module 8 is communicatively connected to the temperature test chamber 2, the charge and discharge device 4, and the data acquisition instrument 6 through the control signal line 7 to perform real-time data transmission and interactive communication, send control instructions according to the acquired data, and achieve automatic linkage control; when the battery temperature and voltage reach the cut-off conditions, the control module can automatically stop the entire test process to achieve the purpose of safety protection. The control module is also used to obtain the voltage and temperature data collected by the data acquisition 6, calculate the battery temperature entropy coefficient according to the acquired voltage and temperature data; automatically save the test data at a preset interval, and save the data at a time interval within 100 ms at most, and the save time interval can be set; the test data supports being exported into an EXCEL file. The control module is preferably implemented by a single-chip microcomputer, a PLC, or a computer PC. In this embodiment, the control signal line 7 includes a USB cable between the control module and the temperature test chamber 2, the charge and discharge device 4, and the data acquisition instrument 6.

[0047] During actual use, the control module realizes the automatic acquisition of the temperature entropy coefficient according to the following test process:

[0048] a) The control module sends a command signal to the temperature test chamber to adjust the temperature in the temperature test chamber to 25 °C. After maintaining it for 1 hour, the control module sends a command signal to the data acquisition instrument, and measures the surface temperature of the battery every 1 min through the temperature sensor. When the temperature change rate of the battery under test is less than 1 °C / min, it is considered that the battery cell under test has reached thermal equilibrium;

[0049] b) The control module sends a command signal to the charge and discharge device to perform constant current charging on the battery at a certain rate. After reaching the cut-off voltage, constant voltage charging is carried out until the charging current is less than 0.025 times the original current. At this time, the battery SOC is considered to be 100%. The control module sends a command signal to the charge and discharge device to disconnect the connection with the battery;

[0050] c) The control module sends a command signal to the temperature test chamber to set the temperature of the temperature test chamber to a certain higher temperature (for example, 45 °C). After maintaining for 1 hour, the control module sends a command signal to the data acquisition system to test the surface temperature of the battery every 1 min through the temperature sensor. When the temperature change rate of the measured battery is less than 1 °C / min, it is considered that the measured battery cell has reached thermal equilibrium;

[0051] d) The control module sends a command signal to the data acquisition instrument to measure the battery voltage every 5 minutes. When the voltage change dE / dt < 0.1 mV / min for two consecutive measurements, record the OCV of the battery at this time;

[0052] e) The control module sends a command signal to the temperature test chamber. Taking 5 °C as the temperature step, adjust the temperature of the temperature test chamber from 45 °C to -20 °C in sequence, and repeat the above steps c and d;

[0053] f) After completing the voltage tests corresponding to different temperatures at the above SOC, the control module calculates the rate of change of voltage with temperature to obtain the temperature entropy coefficient at this SOC;

[0054] g) The control module sends a command signal to the charge and discharge device to perform constant current discharge on the battery at a certain current rate for several minutes with 20% as the SOC adjustment step (in this embodiment, a 0.5C rate is adopted, and the corresponding time is 24 minutes). Repeat the above steps c to f to complete the temperature entropy coefficient tests at battery SOC of 80%, 60%, 40%, 20%, and 0 in sequence.

[0055] Embodiment 2

[0056] The difference between this embodiment and Embodiment 1 is that multiple measured battery cells are placed in the inner cavity of the temperature test chamber for parallel testing. As Figure 2As shown in the figure, cylindrical batteries are placed on the first layer, square batteries are placed on the second layer, and pouch batteries are placed on the third layer. When the first layer is undergoing a normal temperature test, the refrigeration system of the temperature test chamber can control the temperature of the second and third layers separately. In this way, the normal temperature test of the first layer, the low temperature test of the second layer, and the high temperature test of the third layer can be carried out in parallel. Through reasonable arrangement of the test plan, when the first layer is undergoing a normal temperature test, high temperature or low temperature tests can be carried out simultaneously on other layers, and when other layers are undergoing a normal temperature test, high temperature or low temperature tests can be carried out on the first layer. Considering that the temperature-entropy coefficient test of a single battery cell often takes more than 60 hours, the method of Embodiment 2 can greatly reduce the test time, reduce equipment energy consumption and test costs, and at the same time, there is no need to add additional temperature chamber equipment.

[0057] The above are only embodiments of the present invention. The present invention is not limited to the fields involved in this embodiment. Common knowledge such as the specific structures and characteristics known in the solutions is not described in detail herein. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to interpret the content of the claims.

Claims

1. A battery temperature entropy coefficient automatic testing device, characterized in that: It includes a temperature test box, a charge and discharge module, a data acquisition module and a control module. The temperature test box, the charge and discharge module, the data acquisition module and the control module are connected in communication. Temperature test chamber, used to adjust the ambient temperature of the battery cells under test; A data acquisition module, used to collect voltage and temperature data of the tested battery cells; The charge and discharge module is used to adjust the state of charge SOC of the battery cell under test; The control module is used to obtain voltage and temperature data, control the automated linkage test, and calculate the battery temperature entropy coefficient based on the obtained voltage and temperature data.

2. The battery temperature entropy coefficient automatic testing device according to claim 1, characterized in that: The battery temperature entropy coefficient includes test results of the tested battery cells under different ambient temperatures and different SOC conditions, the different ambient temperatures include high temperature, normal temperature and low temperature, and the different SOC conditions include 0, 20%, 40%, 60%, 80%, and 100%.

3. The battery temperature entropy coefficient automatic testing device according to claim 1, characterized in that: The temperature test box has a temperature adjustment range of -30°C to 60°C, and the inner cavity of the temperature test box is divided into at least two layers, and different layers can be independently temperature controlled.

4. The battery temperature entropy coefficient automatic testing device according to claim 1, characterized in that: The data acquisition module is used to collect temperature and voltage data, and the acquisition accuracy of voltage data is 0.1mv.

5. The battery temperature entropy coefficient automatic testing device according to claim 1, characterized in that: The control module saves temperature and voltage data at preset intervals, and the test data can be exported as an EXCEL file.

6. The battery temperature entropy coefficient automatic testing device according to claim 1, characterized in that: The battery cells tested include cylindrical batteries, square batteries and soft-pack batteries.

7. The battery temperature entropy coefficient automatic testing device according to claim 1, characterized in that: At least two battery cells can be tested simultaneously.

8. The battery temperature entropy coefficient automatic testing device according to claim 7, characterized in that: The data acquisition module allocates one voltage channel, five temperature channels and one charge and discharge channel to each battery cell under test.

9. The battery temperature entropy coefficient automatic testing device according to claim 7, characterized in that: Design a matching temperature sensor arrangement scheme based on the type of battery cell being tested.

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