Lithium battery internal resistance test system

Abstract

The invention provides a lithium battery internal resistance test system, which relates to the technical field of lithium battery internal resistance test, and comprises a power supply subsystem, a control and measurement subsystem, a switching and wiring subsystem, a data storage and processing subsystem, a temperature control subsystem, a safety protection subsystem and an auxiliary subsystem, the auxiliary subsystem comprises a differential amplifier subsystem, a frequency change subsystem, an adjustable current source subsystem, a cooling system, a multi-channel test subsystem and a data communication and remote monitoring subsystem, through linkage of the control and measurement subsystem, the switching and wiring subsystem and other subsystems, an automatic test process is realized, manual intervention is reduced, and the test efficiency is improved. The test efficiency and accuracy are improved, different test parameters such as a current range, a frequency range and a temperature range can be set and adjusted through flexible control of the control and measurement subsystem so as to meet the test requirements of lithium batteries of different types and specifications, and the internal resistance value of the battery can be measured more accurately.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium battery internal resistance testing, and more specifically, relates to a lithium battery internal resistance testing system. Background Art

[0002] A lithium battery internal resistance test system is a device used to measure the internal resistance of lithium batteries. Lithium battery internal resistance refers to the electrical resistance within the battery and is a key parameter in measuring battery performance and condition. By measuring the internal resistance of a lithium battery, one can assess its capacity decay, performance stability, and battery life.

[0003] Common lithium battery internal resistance test systems may have the following technical problems: 1. Traditional test systems may have large measurement errors, resulting in inaccurate measurement results of lithium battery internal resistance; 2. Traditional systems may require a lot of manual operation and intervention, and the testing process is not automated enough, resulting in low efficiency; 3. The test parameters and operations of traditional systems are often limited by hardware design and functions, cannot be freely adjusted and optimized, and cannot meet the testing requirements of different lithium batteries; 4. Traditional systems may have insufficient safety protection measures, such as overload, overheating and other safety issues that are not effectively protected.

[0004] Therefore, in view of this, the existing structure and defects are studied and improved, and a lithium battery internal resistance testing system is provided to achieve a more practical purpose. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a lithium battery internal resistance testing system to solve the above problems.

[0006] A lithium battery internal resistance testing system includes a power supply subsystem, a control and measurement subsystem, a switching and wiring subsystem, a data storage and processing subsystem, a temperature control subsystem, a safety protection subsystem and an auxiliary subsystem. The power supply subsystem provides a power supply with stable voltage and current, which is used to provide operating voltage and current to the lithium battery under test; the control and measurement subsystem includes a controller and a measuring instrument, which are used to control the test process and measure the internal resistance of the battery. The controller usually has functions such as controlling the battery charging and discharging process, setting test parameters and recording test data. The measuring instrument generally includes a voltmeter and an ammeter, which are used to measure the voltage and current of the battery; the switching and wiring subsystem is used to connect the lithium battery under test and the control and measurement subsystem, and switch the circuit during the test process. The switch is usually used to switch the charge and discharge mode and connect the battery to the charging or discharging circuit; the wiring part provides connection with the positive and negative poles of the battery and ensures good electrical contact; the data storage and processing subsystem is used to store, process and analyze test data. Typically includes data storage devices (such as hard disks, solid-state memory) and data processing software for recording test results, generating reports, and performing data analysis. The temperature control subsystem is used to control the temperature of the test environment so that lithium batteries can be tested at a constant temperature. The temperature controller typically includes a temperature sensor and a heating / cooling device. The safety protection subsystem is used to provide safety protection for the battery and test system during the test, including overcurrent protection, overtemperature protection, short-circuit protection, etc., to ensure the safety and reliability of the test process. Among them, the auxiliary subsystem includes a differential amplifier subsystem, a frequency change subsystem, an adjustable current source subsystem, a cooling system, a multi-channel test subsystem, and a data communication and remote monitoring subsystem. The differential amplifier subsystem can enhance the sensitivity of the test system to small current and small voltage changes by introducing a differential amplifier, thereby improving the test accuracy and resolution; the frequency change subsystem can obtain battery internal resistance data at different frequencies by changing the frequency during the test process, thereby realizing the test analysis of the high-frequency response and dynamic characteristics of the lithium battery; the adjustable current source subsystem can adjust the current size as needed during the test process to realize internal resistance testing under different working conditions, such as transient response and testing under large current discharge conditions; the cooling system is a lithium battery that generates heat due to energy conversion during the charging and discharging process. Adding a cooling system can control the temperature change of the battery, provide a constant temperature environment, and test the internal resistance of the battery more accurately; the multi-channel test subsystem can perform internal resistance testing on multiple lithium batteries at the same time by adding multiple test channels, thereby improving test efficiency and the degree of automation of the production line; the data communication and remote monitoring subsystem connects the test system with a computer or remote server to realize Real-time data transmission and remote monitoring facilitate data analysis, fault diagnosis, and remote control. The linkage of the control and measurement subsystem, the switching and wiring subsystem, and other subsystems enables an automated testing process, reduces manual intervention, and improves test efficiency and accuracy. Flexible control of the control and measurement subsystem allows for setting and adjusting different test parameters, such as current range, frequency range, and temperature range, to meet the testing requirements of lithium batteries of different types and specifications. Innovative subsystems, such as the differential amplifier subsystem, the frequency variation subsystem, and the adjustable current source subsystem, enable more accurate measurement of the battery's internal resistance, improving test accuracy and reliability. The safety protection subsystem provides multiple protection measures during the testing process, such as overcurrent protection, overtemperature protection, and short-circuit protection, effectively preventing safety issues such as battery overload and overheating. The multi-channel test subsystem allows for simultaneous testing of the internal resistance of multiple lithium batteries, improving test efficiency and making it suitable for both batch and production line testing. The data storage and processing subsystem facilitates the storage and management of test data, and data processing software enables data analysis and report generation, providing more convenient data management and analysis capabilities. The power subsystem provides stable voltage and current, and supports 0-50V / 0-100A adjustable output; The control and measurement subsystems are linked to the power subsystem through the PID algorithm to achieve ±0.1% accuracy control of the test current; The differential amplifier subsystem in the auxiliary subsystem uses a differential amplifier circuit to improve the voltage sampling accuracy to 10μV; Each subsystem realizes real-time data interaction through the CANopen bus, and the communication delay is ≤1ms.

[0007] Preferably, the switching and wiring subsystem includes: Four-quadrant power switching module, supporting fast switching of charge and discharge modes within 0.5 seconds; Kelvin four-wire connection structure eliminates the ±0.5mΩ measurement error caused by lead resistance; The control and measurement subsystem controls the switch through the SPI interface to achieve automatic on and off of the test loop.

[0008] Preferably, the frequency change subsystem adopts DDS digital frequency synthesis technology: Frequency adjustment range 10mHz-10kHz, resolution 1mHz; Cooperating with the frequency sweep algorithm of the control and measurement subsystem, generating internal resistance-phase characteristic curves at different frequencies; The data storage and processing subsystem performs FFT transformation on the data at each frequency point and extracts the electrochemical impedance spectroscopy parameters.

[0009] Preferably, the temperature control subsystem constructs a three-level temperature control system: Environmental chamber temperature control (-40℃-125℃, accuracy ±0.5℃); Battery surface mount PT100 sensor (response time ≤ 2 seconds); The control and measurement subsystem adjusts the semiconductor cooling plate through the fuzzy PID algorithm to achieve a battery temperature field uniformity of ≤±1℃.

[0010] Preferably, the security protection subsystem includes a triple protection mechanism: Hardware-level overcurrent protection (response time ≤ 10μs, action threshold 0-100A adjustable); Software-level over-temperature protection (automatically cuts off the circuit when the battery surface temperature exceeds 85°C); The control and measurement subsystem monitors the slope of the VI curve in real time and triggers short-circuit protection (cut-off time ≤ 1ms) when an abnormality occurs.

[0011] Preferably, the multi-channel test subsystem adopts time division multiplexing technology: Supports 16-channel synchronous testing, with independent configuration of test parameters for each channel; Channel switching time ≤ 50ms, crosstalk between channels ≤ 0.1%; The control and measurement subsystem realizes multi-channel data parallel acquisition through a polling mechanism, with a sampling rate of ≥10kHz.

[0012] Preferably, the data communication and remote monitoring subsystem: Support OPCUA protocol to achieve real-time synchronization of test data in the cloud; The remote monitoring software has a three-dimensional visual interface, which can retrieve the VIT curve of any test node in real time; When the control and measurement subsystem receives remote instructions, it implements hierarchical authority management (three-level authority authentication).

[0013] Preferably, the adjustable current source subsystem adopts a linear + switching hybrid topology: The low current range (0-1A) uses a linear power supply (ripple ≤ 100μA); The high current segment (1-100A) adopts phase-shifted full-bridge topology (efficiency ≥ 95%); The control and measurement subsystem automatically switches the topology according to the test conditions to achieve high-precision output over the full range of 0.1mA-100A.

[0014] Preferably, the cooling system adopts phase change energy storage + forced air cooling composite heat dissipation: Phase change material (melting point 25°C) absorbs transient heat generation in the battery; The centrifugal fan (air volume 150CFM) is combined with the air guide duct to ensure that the wind speed uniformity on the battery surface is ≥90%; The temperature control subsystem automatically adjusts the fan speed (0-3000rpm) according to the battery temperature rise rate.

[0015] Another technical problem to be solved by the present invention is to provide a testing method for a lithium battery internal resistance testing system, comprising: Parameter collaborative optimization step: The control and measurement subsystems automatically match the frequency-current-temperature combination parameters according to the battery type; Dynamic calibration steps: Before testing, full-scale drift compensation is performed using a standard resistor array (accuracy ±0.01%); Data credibility assessment steps: The data storage and processing subsystem performs Grubbs criterion on the test data to remove outliers; The method automates the entire process from parameter setting to report generation, shortening the time required for a single test by 60% compared to traditional systems.

[0016] Compared with the prior art, the present invention has the following beneficial effects: In the present invention, through the linkage of the control and measurement subsystem, the switching and wiring subsystem and other subsystems, an automated testing process is realized, manual intervention is reduced, and testing efficiency and accuracy are improved. Through the flexible control of the control and measurement subsystem, different test parameters, such as current range, frequency range, temperature range, etc., can be set and adjusted to meet the testing requirements of lithium batteries of different types and specifications. Through creative subsystems, such as the differential amplifier subsystem, the frequency change subsystem, the adjustable current source subsystem, etc., the internal resistance of the battery can be measured more accurately, and the accuracy and reliability of the test can be improved. The safety protection subsystem provides multiple protection measures for the testing process, such as overcurrent protection, overtemperature protection and short-circuit protection, which effectively prevent safety problems such as battery overload and overheating. Through the multi-channel testing subsystem, the internal resistance of multiple lithium batteries can be tested at the same time, improving testing efficiency, and is suitable for batch testing and production line testing. Through the data storage and processing subsystem, test data can be conveniently stored and managed, and data processing software is used for data analysis and report generation, providing more convenient data management and analysis capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the system structure of the present invention. DETAILED DESCRIPTION

[0018] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0019] See also Figure 1The present invention provides a lithium battery internal resistance testing system, including a power supply subsystem, a control and measurement subsystem, a switching and wiring subsystem, a data storage and processing subsystem, a temperature control subsystem, a safety protection subsystem and an auxiliary subsystem; the power supply subsystem provides a power supply with stable voltage and current, which is used to provide working voltage and current to the lithium battery under test; the control and measurement subsystem includes a controller and a measuring instrument, which are used to control the test process and measure the internal resistance of the battery. The controller usually has functions such as controlling the battery charging and discharging process, setting test parameters and recording test data. The measuring instrument generally includes a voltmeter and an ammeter, which are used to measure the voltage and current of the battery; the switching and wiring subsystem is used to connect the lithium battery under test and the control and measurement subsystem, and switch the circuit during the test process. The switch is usually used to switch the charge and discharge mode and connect the battery to the charging or discharging circuit; the wiring part provides connection with the positive and negative poles of the battery and ensures good electrical contact; the data storage and processing subsystem is used to store, process and analyze the test data. Typically includes data storage devices (such as hard disks, solid-state memory) and data processing software for recording test results, generating reports, and performing data analysis. The temperature control subsystem is used to control the temperature of the test environment so that lithium batteries can be tested at a constant temperature. The temperature controller typically includes a temperature sensor and a heating / cooling device. The safety protection subsystem is used to provide safety protection for the battery and test system during the test, including overcurrent protection, overtemperature protection, short-circuit protection, etc., to ensure the safety and reliability of the test process. Among them, the auxiliary subsystems include differential amplifier subsystem, frequency change subsystem, adjustable current source subsystem, cooling system, multi-channel test subsystem, data communication and remote monitoring subsystem; The differential amplifier subsystem enhances the test system's sensitivity to small current and voltage changes by introducing a differential amplifier, thereby improving test accuracy and resolution. The frequency variation subsystem obtains battery internal resistance data at different frequencies by changing the frequency during the test, thereby enabling testing and analysis of the high-frequency response and dynamic characteristics of lithium batteries. The adjustable current source subsystem adjusts the current as needed during the test to enable internal resistance testing under different operating conditions, such as transient response and high-current discharge testing. The cooling system controls the temperature changes of the battery, providing a constant temperature environment and enabling more accurate testing of the battery's internal resistance, as heat is generated during the charge and discharge process of the lithium battery due to energy conversion. The multi-channel test subsystem enables simultaneous internal resistance testing of multiple lithium batteries by adding multiple test channels, improving test efficiency and the degree of automation of the production line. The data communication and remote monitoring subsystem connects the test system to a computer or remote server to achieve real-time data transmission and remote monitoring, facilitating data analysis, fault diagnosis, and remote control. The control and measurement subsystem is linked to the power subsystem. The controller sets the voltage and current of the power output through communication with the power subsystem to provide the required test conditions. The switching and wiring subsystem is linked to the control and measurement subsystem, wherein the switch switches the charge and discharge mode and connects or disconnects the battery and the test instrument according to the command of the control and measurement subsystem; The control and measurement subsystem is linked to the temperature control subsystem. The controller receives feedback from the temperature sensor and controls the heating / cooling device to achieve a constant temperature test environment according to the set temperature range. The control and measurement subsystem is linked to the data storage and processing subsystem. The controller transmits the test parameters and recorded test data to the data storage and processing subsystem to save the test results and perform data processing and analysis. The control and measurement subsystem is linked to the multi-channel test subsystem. The controller controls the actions and parameters of multiple test channels simultaneously to perform internal resistance tests on multiple lithium batteries. The data communication and remote monitoring subsystem is connected to the control and measurement subsystem, and transmits the data of the control and measurement subsystem to the remote monitoring software through the data communication equipment to realize remote monitoring and control; The inspection steps are as follows: S1: Set test parameters; through the operation interface of the control and measurement subsystem or related software, set the test parameters, including the test current range, test frequency range, test temperature range, etc. S2: Connect the battery; connect the positive and negative poles of the lithium battery under test to the corresponding interfaces in the switching and wiring subsystem respectively to ensure good electrical connection; S3: Start the test; click the test start button or use the control command, the controller starts charging or discharging the battery and measures the battery voltage and current at the same time; S4: Test data acquisition and processing; the control and measurement subsystem transmits the voltage and current data obtained from the test to the data storage and processing subsystem for data acquisition and processing, and stores the results in a designated location; S5: Analysis and report generation: Use data processing software to analyze the collected test data and obtain the internal resistance value of the lithium battery. Generate test reports and data analysis results as needed; S6: Terminate the test; after the test is completed, stop charging, discharging and measuring, and disconnect the battery under test.

[0020] Through the linkage of the control and measurement subsystem, the switching and wiring subsystem and other subsystems, an automated testing process is achieved, manual intervention is reduced, and test efficiency and accuracy are improved. Through the flexible control of the control and measurement subsystem, different test parameters such as current range, frequency range, temperature range, etc. can be set and adjusted to meet the testing needs of lithium batteries of different types and specifications. Through creative subsystems such as the differential amplifier subsystem, frequency change subsystem, and adjustable current source subsystem, the internal resistance of the battery can be measured more accurately, improving the accuracy and reliability of the test. The safety protection subsystem provides multiple protection measures for the testing process, such as overcurrent protection, overtemperature protection and short-circuit protection, effectively preventing safety issues such as battery overload and overheating. The multi-channel test subsystem can test the internal resistance of multiple lithium batteries at the same time, improving test efficiency, which is suitable for batch testing and production line testing. The data storage and processing subsystem can conveniently store and manage test data, and the use of data processing software for data analysis and report generation provides more convenient data management and analysis capabilities.

[0021] System overall architecture and communication design: The lithium battery internal resistance test system provided in this embodiment adopts a modular design. Its seven subsystems exchange data in real time via a CANopen bus (1Mbps transmission rate, using the TJA1050 transceiver). The power subsystem and the control and measurement subsystem are connected via a dedicated shielded twisted-pair cable, with signal latency ≤1ms. The differential amplifier subsystem in the auxiliary subsystem and the measuring instrument are connected via coaxial cable, ensuring the acquisition of 10μV voltage signals without attenuation. The core control unit utilizes an STM32H743VI microcontroller (480MHz main frequency) coupled with an AD7606 16-bit synchronous sampling ADC (200kSPS sampling rate) for high-precision data acquisition. The power subsystem and the control and measurement subsystem are linked to achieve: 1. Power supply topology and precision control: The power subsystem adopts the front-stage PFC switching power supply (model LRS-1000-48) + post-stage linear adjustment circuit structure: Voltage output module: Extended by TI's LM317T three-terminal voltage regulator and filtered by a 20000μF / 63V electrolytic capacitor, it achieves continuous adjustment from 0-50V with a voltage ripple of ≤500μV. Current output module: The low current range (0-1A) uses the OPA549 power op amp to form a constant current source, and the high current range (1-100A) uses the IR2110 to drive the IGBT (model FF300R12ME4) to form a phase-shifted full-bridge circuit with an efficiency of ≥95%; PID algorithm implementation: The control subsystem adopts an incremental PID algorithm with parameters configured as Kp=2.5, Ki=0.1, and Kd=0.05. The output current is sampled in real time by the ADC, and after PID calculation, the PWM signal is driven to adjust the power supply output, achieving ±0.1% current accuracy control. 2. Differential amplification and signal acquisition: The differential amplifier subsystem uses the AD8221 differential amplifier from Analog Devices, configured in 1000x gain mode: The input stage uses 0.1% precision thin film resistors (1kΩ / 1MΩ voltage divider network) to ensure a minimum resolution of 10μV; The measurement circuit adopts the Kelvin four-wire system, with the voltage sampling line and the current line wired separately (spacing ≥ 10mm), eliminating the ±0.5mΩ measurement error caused by lead resistance; The control subsystem controls the analog switch ADG1608 through the SPI interface (clock frequency 10MHz) to achieve automatic on-off of the test loop, with a switching time of ≤50μs. Frequency variation subsystem and electrochemical impedance spectroscopy: 1.DDS frequency synthesis implementation: The frequency change subsystem uses the AD9833DDS chip as its core to construct a 10mHz-10kHz sweep frequency signal source: Frequency resolution reaches 1mHz, and the frequency sweep strategy can be configured through the control subsystem (such as collecting 100 data points every 10 times the frequency); The output signal is buffered by the OPA2227 op amp and injected into the test loop. The AD8302 phase detector is used to synchronously collect the amplitude and phase of the voltage and current. The data storage and processing subsystem uses the ARMCMSIS-DSP library to implement 1024-point FFT transformation, uses the Hanning window function to reduce spectrum leakage, and extracts the real / imaginary parameters of the electrochemical impedance spectroscopy (EIS). 2. Impedance spectrum analysis process: When the control subsystem executes the frequency sweep algorithm, it generates the internal resistance-phase characteristic curve according to the following logic: Starting from 10mHz, increase the frequency in logarithmic steps to 10kHz; Apply 100mA test current at each frequency point and collect 100 sets of voltage and current data; Perform FFT transformation on the data and calculate the impedance modulus and phase angle at the frequency; The Randles equivalent circuit model (Rct-CPE-Q) was used to fit the EIS data, and the charge transfer resistance Rct was extracted as the battery internal resistance. Three-level temperature control implementation of the temperature control subsystem: 1. Environmental chamber and sensor configuration: The temperature control subsystem builds a three-level temperature control system: Level 1 temperature control: The environmental chamber uses a TEC1-12706 semiconductor refrigeration chip + a 2000W nickel-chromium electric heating wire, controlled by a solid-state relay (G3MB-202P), achieving -40°C to 125°C temperature control with an accuracy of ±0.5°C. Secondary temperature control: A PT100 temperature sensor (three-wire connection) is mounted on the battery surface and amplified by the instrumentation amplifier INA128 before being sent to the control subsystem. The response time is ≤ 2 seconds. Level 3 temperature control: Phase change material (melting point 25°C, model RT25HC) is laid on the bottom of the battery to absorb transient heat. A centrifugal fan (air volume 150 CFM) is used to force heat dissipation, ensuring that the wind speed uniformity on the battery surface is ≥90%.

[0022] 2. Fuzzy PID control algorithm: The control subsystem uses 7×7 fuzzy subsets to achieve temperature control: Definition of fuzzy variables: temperature deviation e∈{-3,-2,-1,0,1,2,3}, deviation change rate ec∈{-3,-2,-1,0,1,2,3}; The control rule base contains 49 rules (e.g. ife=NBandec=NBthenu=PB), and the output u is the PWM duty cycle; The current of the semiconductor cooling chip is adjusted by PWM signal (frequency 10kHz), and the fan speed (0-3000rpm) is combined to achieve battery temperature field uniformity ≤±1℃. Triple protection mechanism of the security protection subsystem: 1. Hardware-level overcurrent protection: The hardware protection circuit of the safety protection subsystem includes: Sampling resistor: 0.1mΩ / 5W manganese copper resistor (accuracy 0.01%), connected in series to the current loop; Comparator circuit: uses LM319 high-speed comparator, the reference voltage is provided by TL431 precision reference source, and the response time is ≤10μs; Cut-off execution: When overcurrent occurs, the optocoupler 6N137 is driven to quickly shut down the IGBT drive signal. The action threshold can be adjusted in the range of 0-100A by the potentiometer. 2. Software-level security policy: The control subsystem performs dual software protection in real time: Over-temperature protection: When the PT100 sensor detects that the battery surface temperature is greater than 85°C, a command is sent through the SPI interface to cut off the power output; Short-circuit protection: Calculates the VI curve slope in real time (sampling interval 100μs). When the slope change rate is greater than 5V / A·ms, a hardware interrupt is triggered, cutting off the test circuit within 1ms. Multi-channel testing and remote monitoring implementation: 1. Channel time division multiplexing design: The multi-channel test subsystem uses the ADG1608 multi-way analog switch to build a 16-channel switching circuit: Channel switching timing: The control subsystem completes 16-channel switching every 50ms through a polling mechanism, with a sampling rate of 10kHz; Crosstalk suppression: Each channel input stage uses an independent operational amplifier (OPA2333) for buffering, the isolation resistance between channels is ≥10MΩ, and the crosstalk is ≤0.1%; Parallel acquisition: Each channel is equipped with an independent sample-and-hold circuit (LF398) to achieve synchronous data acquisition of 16 channels. 2. Remote monitoring and data interaction: The data communication and remote monitoring subsystem implements a three-layer architecture: Communication protocol: Adopts OPCUA protocol stack (FreeOpcUa open source library) and realizes cloud synchronization through Ethernet interface (W5500 chip); Visualization interface: The remote monitoring software is developed based on the Qt framework, and the 3D visualization module uses the VTK library, which can retrieve the VIT curve of any channel in real time; Authority management: When the control subsystem receives a remote command, it performs three-level authority authentication (administrator / engineer / operator) and transmits the command data using AES-128 encryption. Full process automation of test methods: 1. Parameter collaborative optimization: Control and measurement subsystem built-in battery type-parameter mapping table: 2. Dynamic calibration and data evaluation: The test method includes triple precision assurance: Full-scale drift compensation: Before testing, a standard resistor array (0.1mΩ-100mΩ, accuracy ±0.01%) is connected and the measurement circuit is calibrated using the four-point method. Outlier elimination: The data storage and processing subsystem uses the Grubbs criterion (95% confidence level) to automatically eliminate data when it deviates from the mean by 3σ; Process automation: The entire process from parameter setting to report generation is scheduled by the control subsystem. A single test takes only 8 minutes, which is 60% shorter than the traditional system (20 minutes). Example verification data: The 18650 ternary lithium battery (capacity 2200mAh) was tested at 25°C and the following data was obtained: Internal resistance measurement accuracy: ±0.2mΩ (standard value 35.6mΩ, measured 35.8mΩ); Frequency response: Impedance modulus 36.2mΩ at 100Hz, phase angle -12.5°; Multi-channel consistency: When 16 channels are tested simultaneously, the maximum deviation is ≤0.5%; Safety response: Overcurrent (100A) protection response time 8μs, short-circuit protection cut-off time 0.8ms.

[0023] This implementation method achieves high-precision, automated testing of lithium battery internal resistance through specific hardware selection, algorithm parameters, and test data.

[0024] The embodiments of the present invention are presented for purposes of illustration and description and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those skilled in the art. The embodiments are chosen and described in order to better illustrate the principles of the invention and its practical application and to enable those skilled in the art to understand the invention and design various embodiments with various modifications as suited for specific applications.

Claims

1. A lithium battery internal resistance test system, characterized by: Including power supply subsystem, control and measurement subsystem, switching and wiring subsystem, data storage and processing subsystem, temperature control subsystem, safety protection subsystem and auxiliary subsystem; The power subsystem provides stable voltage and current, and supports 0-50V / 0-100A adjustable output; The control and measurement subsystems are linked to the power subsystem through the PID algorithm to achieve ±0.1% accuracy control of the test current; The differential amplifier subsystem in the auxiliary subsystem uses a differential amplifier circuit to improve the voltage sampling accuracy to 10μV; Each subsystem realizes real-time data interaction through the CANopen bus, and the communication delay is ≤1ms.

2. A lithium battery internal resistance testing system as claimed in claim 1, characterized in that: The switching and wiring subsystem includes: Four-quadrant power switching module, supporting fast switching of charge and discharge modes within 0.5 seconds; Kelvin four-wire connection structure eliminates the ±0.5mΩ measurement error caused by lead resistance; The control and measurement subsystem controls the switch through the SPI interface to achieve automatic on and off of the test loop.

3. A lithium battery internal resistance testing system as claimed in claim 1, characterized in that: The frequency change subsystem uses DDS digital frequency synthesis technology: Frequency adjustment range 10mHz-10kHz, resolution 1mHz; Cooperating with the frequency sweep algorithm of the control and measurement subsystem, generating internal resistance-phase characteristic curves at different frequencies; The data storage and processing subsystem performs FFT transformation on the data at each frequency point and extracts the electrochemical impedance spectroscopy parameters.

4. A lithium battery internal resistance testing system as claimed in claim 1, characterized in that: The temperature control subsystem builds a three-level temperature control system: Environmental chamber temperature control; Battery surface mount PT100 sensor; The control and measurement subsystem adjusts the semiconductor cooling plate through the fuzzy PID algorithm to achieve a battery temperature field uniformity of ≤±1℃.

5. A lithium battery internal resistance testing system as claimed in claim 1, characterized in that: The security protection subsystem includes a triple protection mechanism: Hardware-level overcurrent protection; Software-level over-temperature protection; The control and measurement subsystem monitors the slope of the VI curve in real time and triggers short-circuit protection when an abnormality occurs.

6. A lithium battery internal resistance testing system as claimed in claim 1, characterized in that: The multi-channel test subsystem uses time division multiplexing technology: Supports 16-channel synchronous testing, with independent configuration of test parameters for each channel; Channel switching time ≤ 50ms, crosstalk between channels ≤ 0.1%; The control and measurement subsystem realizes multi-channel data parallel acquisition through a polling mechanism, with a sampling rate of ≥10kHz.

7. A lithium battery internal resistance testing system as claimed in claim 1, characterized in that: Data communication and remote monitoring subsystem: Support OPCUA protocol to achieve real-time synchronization of test data in the cloud; The remote monitoring software has a three-dimensional visual interface, which can retrieve the VIT curve of any test node in real time; When the control and measurement subsystem receives remote instructions, it performs hierarchical authority management.

8. A lithium battery internal resistance testing system as claimed in claim 1, characterized in that: The adjustable current source subsystem adopts a linear + switching hybrid topology: The low current range (0-1A) uses a linear power supply (ripple ≤ 100μA); The high current segment (1-100A) adopts phase-shifted full-bridge topology (efficiency ≥ 95%); The control and measurement subsystem automatically switches the topology according to the test conditions to achieve high-precision output over the full range of 0.1mA-100A.

9. A lithium battery internal resistance test system as claimed in claim 1, wherein the cooling system adopts a phase change energy storage + forced air cooling composite heat dissipation method: Phase change materials absorb transient heating of the battery; The centrifugal fan is combined with the air guide duct to ensure that the wind speed uniformity on the battery surface is ≥90%; The temperature control subsystem automatically adjusts the fan speed according to the battery temperature rise rate.

10. A method for testing a lithium battery internal resistance test system according to any one of claims 1 to 9, characterized in that include: Parameter collaborative optimization step: The control and measurement subsystems automatically match the frequency-current-temperature combination parameters according to the battery type; Dynamic calibration steps: Before testing, full-scale drift compensation is performed using a standard resistor array; Data credibility assessment steps: The data storage and processing subsystem performs Grubbs criterion on the test data to remove outliers; The method automates the entire process from parameter setting to report generation, shortening the time required for a single test by 60% compared to traditional systems.

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