A high-voltage battery pack electrochemical impedance spectroscopy detection device and method based on self-excitation of a measured battery

Abstract

The application discloses a high-voltage battery pack electrochemical impedance spectrum detection device and method based on self-excitation of a measured battery. The device comprises a low-voltage precision signal conditioning unit, a high-voltage power absorption unit, a high-voltage side voltage acquisition unit, a digital isolation communication unit, a multi-point temperature acquisition array, an external communication module and a main control processing unit. The high-voltage power absorption unit is directly connected to a bus of a measured high-voltage battery pack and is composed of power semiconductor devices with a voltage resistance level of greater than or equal to 1000 V. Under the drive of a perturbation control signal, the high-voltage power absorption unit only absorbs weak energy of the micro-watt to milliwatt level to generate a current disturbance. The high-voltage side voltage acquisition unit is independent of an EIS power loop and collects a voltage response of a battery pack port through a direct link of a high-voltage precision voltage divider, a precision ADC and a digital isolator, so as to avoid the coupling of current noise of the power absorption loop to a voltage measurement path. The main control processing unit reads complex impedance calculated by the low-voltage precision signal conditioning unit and combines multi-point PT1000 temperature data to perform temperature compensation correction and health state evaluation. The application does not need an external excitation source, supports RS485 and WiFi / Bluetooth / 4G communication, considers online and offline detection, and has the characteristics of low cost, high precision and strong compatibility.

Description

Technical Field

[0001] This invention belongs to the field of battery testing, evaluation, and diagnosis technology, and specifically relates to a high-voltage battery pack electrochemical impedance spectroscopy detection device and method based on the self-excitation of the battery under test. Background Technology

[0002] Electrochemical impedance spectroscopy (EIS) is a non-destructive, in-situ electrochemical analysis method. By applying a small sinusoidal AC perturbation to the test system and simultaneously measuring the response, it obtains characteristic curves (Nyquist plot, Bode plot) of complex impedance as a function of frequency, thereby resolving key parameters such as charge transfer resistance, solid electrolyte interphase (SEI) film characteristics, lithium ion diffusion coefficient, and interface stability.

[0003] In the field of electric vehicles, EIS has been widely recognized as an effective means of assessing the State of Health (SOH) of power batteries and providing early warning of thermal runaway risks. Studies have shown that when aging or abnormal states occur inside the battery, such as lithium dendrite growth, electrolyte decomposition, separator micro-short circuits, or loss of active materials, its electrochemical impedance spectroscopy will show identifiable characteristic shifts in specific frequency bands (especially the mid-to-low frequency band).

[0004] However, existing EIS testing technologies generally suffer from the following technical bottlenecks when applied to high-voltage battery packs (such as 400V / 800V / 1000V platforms): First, they rely on external high-power excitation sources. Laboratory-grade high-voltage EIS equipment, such as the Gamry LPI1010, requires an external high-power electronic load or independent power supply to generate excitation signals and modulate battery current. Such equipment is bulky and expensive (in the hundreds of thousands of yuan range), making it impossible to embed it into charging piles or vehicle battery management systems (BMS) for online monitoring.

[0005] Second, it is only applicable to single-cell or module-level testing. Integrated solutions, represented by battery monitoring chips (AFE) such as Texas Instruments (TI) BQ79826Z and NXP (NXP) BMA7418, integrate the EIS excitation source and detection circuit inside the chip. However, due to the voltage withstand capability of semiconductor processes, they can only measure single-cell batteries (usually below 100V) and cannot directly measure high-voltage systems consisting of hundreds of cells connected in series.

[0006] Third, there is a lack of an independent high-voltage acquisition channel. Existing low-cost EIS solutions based on general-purpose AFEs such as AD5941 have chip architectures primarily designed for the small signal conditioning of electrochemical cells and lack the ability to directly acquire the port voltage of the high-voltage battery pack. If the port voltage is forcibly acquired through the EIS power loop, the switching noise, ripple current, and ground disturbances of the power absorption loop will be severely coupled to the voltage measurement path, resulting in a significant increase in impedance calculation errors and failing to meet the accuracy requirements of the entire battery pack-level EIS.

[0007] Fourth, there is a lack of effective temperature compensation and multi-point thermal monitoring mechanisms. Battery impedance has a significant temperature dependence. Existing high-voltage EIS schemes often only perform single-point temperature measurements or ignore temperature correction, resulting in a lack of comparability of impedance data measured at different ambient temperatures, which affects the accuracy of SOH assessment.

[0008] Fifth, the communication interface is limited, making it difficult to accommodate both online and offline scenarios. Existing dedicated equipment typically only supports wired communication protocols in laboratories, failing to simultaneously meet the flexible needs of embedded RS485 bus communication in charging piles and wireless data transmission (WiFi / Bluetooth / 4G) in after-sales maintenance scenarios.

[0009] Therefore, there is an urgent need for a low-cost EIS testing solution for high-voltage battery packs that requires no external excitation source, no complex power conversion, has independent isolated high-voltage voltage acquisition, supports multi-point temperature compensation and multi-mode communication, and simultaneously supports online integration and offline independent use. Summary of the Invention

[0010] The purpose of this invention is to provide a high-voltage battery pack electrochemical impedance spectroscopy (EIS) detection device and method based on the self-excitation of the battery under test, so as to solve the technical problems in the prior art, such as reliance on external power supply for high-voltage whole pack EIS detection, lack of high-voltage isolation voltage acquisition, EIS accuracy affected by power circuit interference, ineffective compensation for temperature drift, and single communication method.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a high-voltage battery pack electrochemical impedance spectroscopy detection device based on the self-excitation of the battery under test, comprising: a low-voltage precision signal conditioning unit, a high-voltage power absorption unit, a high-voltage side voltage acquisition unit, a digital isolation communication unit, a multi-point temperature acquisition array, an external communication module, and a main control processing unit.

[0012] The high-voltage power absorption unit is directly electrically connected between the positive and negative busbars of the high-voltage battery pack under test, and is composed of power semiconductor devices (such as high-voltage MOSFETs or IGBTs) with a withstand voltage rating of ≥1000V. The low-voltage precision signal conditioning unit generates a micro-perturbation control signal, which is transmitted to the high-voltage side via a digitally isolated communication unit, driving the power semiconductor devices to operate in the linear amplification region or a controlled switching state, thereby absorbing weak energy from the battery pack itself and generating frequency-controllable current disturbances.

[0013] Since the excitation energy comes directly from the battery pack under test and the absorbed power is only in the microwatt to milliwatt range (which does not affect the normal operation of the battery pack), no external independent power supply, DC-DC converter or electronic load is required.

[0014] The low-voltage precision signal conditioning unit synchronously acquires the voltage response signal of the battery pack under current disturbances and directly calculates the complex impedance through its internally integrated Discrete Fourier Transform (DFT) or Digital Correlation Method calculation engine. The calculation result is then digitally isolated and transmitted back to the main control processing unit. The high-voltage side voltage acquisition unit is directly connected to the positive and negative buses of the battery pack, independent of the EIS power absorption circuit. It acquires the port voltage response of the battery pack under current disturbances through a direct link of "high-voltage precision voltage divider network → precision analog-to-digital converter → digital isolator". Because this unit is electrically isolated from the low-voltage precision signal conditioning unit and the high-voltage power absorption unit, the current noise, switching ripple, and ground potential fluctuations of the power absorption circuit are effectively blocked and cannot be coupled to the voltage measurement path, thereby ensuring the purity of the voltage response signal and the accuracy of the EIS calculation.

[0015] The multi-point temperature acquisition array collects multi-point temperature data in real time through multiple PT1000 platinum resistance temperature sensors distributed on the surface of the battery pack and key hot spots. The main control processing unit reads the complex impedance calculated by the low-voltage precision signal conditioning unit and combines it with the multi-point temperature data to perform temperature compensation on the complex impedance through a preset temperature-impedance correction model, and then evaluates the health status of the battery pack based on the compensated complex impedance.

[0016] The external communication module includes at least an RS485 wired communication interface and one or more wireless communication interfaces such as WiFi, Bluetooth, and 4G cellular network, used to upload detection data to a cloud platform or to interact with a host computer or mobile terminal.

[0017] Secondly, the present invention also provides a corresponding detection method, including: connecting to a high-voltage power absorption unit, generating a self-excited current disturbance, acquiring the port voltage response through an electrically isolated independent voltage acquisition channel, calculating the complex impedance spectrum internally by a low-voltage precision signal conditioning unit, reading and performing temperature compensation and health assessment by a main control processing unit, and outputting an early warning, etc. Beneficial effects

[0018] 1. No external excitation source required, system is extremely simple. The excitation energy comes directly from the battery pack under test itself. The perturbation is achieved by controlling the gate signal of the high-voltage power semiconductor device, eliminating the need for a high-power power supply, electronic load or DC-DC converter. The system cost is reduced by an order of magnitude and the size is greatly reduced.

[0019] 2. Independent isolation voltage acquisition ensures EIS accuracy. The high-voltage side voltage acquisition unit is electrically isolated from the EIS power circuit, preventing current disturbance noise from coupling to the voltage measurement path. This solves the problem that general-purpose AFEs cannot directly acquire high-voltage voltages and are susceptible to interference from the power circuit.

[0020] 3. The AFE performs DFT calculations internally, reducing the burden on the MCU. The low-voltage precision signal conditioning unit (such as AD5941) integrates a DFT / correlation calculation engine, which performs complex impedance calculations directly at the chip level. The main control processing unit only needs to read the results and perform temperature compensation and health assessment, which reduces the requirements for the main control MCU's computing power and improves the system's real-time performance.

[0021] 4. High-voltage package compatibility, overcoming AFE withstand voltage limitations. Through an architecture of "low-voltage precision AFE + high-voltage power devices + digital isolation", it achieves 1000V-level package detection, solving the technical bottleneck that existing AFE chips cannot directly measure high-voltage packages.

[0022] 5. Compatible with both online and offline modes. It can be embedded in charging piles or BMS for online monitoring, or it can be used as a standalone portable device for after-sales offline testing, covering the entire lifecycle of R&D, production, operation and maintenance, and secondary utilization.

[0023] 6. Multi-point temperature compensation enhances data comparability. A multi-point PT1000 array is used to collect surface and hot spot temperatures of the battery pack. A temperature-impedance correction model is used to eliminate the influence of temperature drift, ensuring that impedance data measured under different ambient temperatures are comparable.

[0024] 7. Multi-mode communication, supporting cloud collaboration. Integrating RS485 and WiFi / Bluetooth / 4G communication interfaces, it meets the industrial bus access requirements of charging piles / BMS and also supports wireless uploading of test data to the cloud platform for big data analysis and remote diagnostics.

[0025] 8. Non-destructive micro-perturbation, true in-situ detection. The absorbed power is only in the microwatt to milliwatt range, without changing the battery's operating state, and can be performed online during charging, resting, or discharging. Attached Figure Description

[0026] Figure 1 This is a system overall architecture block diagram provided in the embodiments of the present invention; Figure 2 This is a schematic diagram of a high-voltage power absorption unit circuit provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the high-voltage side voltage acquisition unit circuit provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the internal EIS signal link of the core chip of the low-voltage precision signal conditioning unit provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the multi-point temperature acquisition array arrangement provided in an embodiment of the present invention; Figure 6 This is a diagram illustrating the digital isolated communication and external communication architecture provided in an embodiment of the present invention. Figure 7 This is a schematic diagram of an online integration application scenario provided by an embodiment of the present invention; Figure 8 This is a schematic diagram of an offline independent application scenario provided by an embodiment of the present invention; Figure 9 This is an example of a measured Nyquist plot and thermal runaway early warning logic provided for an embodiment of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0028] Example 1: System Overall Architecture like Figure 1 As shown, the high-voltage battery pack electrochemical impedance spectroscopy detection device based on self-excitation of the tested battery provided in this embodiment of the invention includes: • High-voltage power absorption unit 101: Directly connected between the positive and negative busbars (HV+ / HV-) of the high-voltage battery pack 100 under test, it consists of a high-voltage MOSFET (such as IXTH2N150L) or IGBT with a withstand voltage ≥1000V, a gate drive resistor, an overcurrent sampling resistor, a TVS overvoltage protection diode, and a temperature sensor. Under the drive of a perturbation control signal, this unit absorbs weak energy from the battery pack 100 itself to generate a frequency-controllable current perturbation I_perturb.

[0029] • Low-voltage precision signal conditioning unit 102: Includes a general-purpose electrochemical analog front-end chip (such as AD5941) and peripheral signal conditioning circuitry. The AD5941 integrates a waveform generator, HSDAC, gain stage, excitation buffer, LPTIA, MUX, 16-bit 800kHz ADC, and a DFT / digital correlation calculation engine. The AD5941's withstand voltage is significantly lower than the battery pack bus voltage (typically << 5V). Its output perturbation signal drives the high-voltage power absorption unit 101 after digital isolation. Simultaneously, this unit acquires the current response signal through the AIN1 pin, digitizes it via the internal LPTIA and ADC, and the on-chip DFT engine directly calculates the complex impedance at each frequency point. The calculation results are transmitted to the main control processing unit 105 via the SPI interface and digitally isolated communication unit 104.

[0030] • High-voltage side voltage acquisition unit 103: Independent of the EIS power circuit, it is directly connected in parallel to the positive and negative buses of the battery pack 100. It includes a high-voltage precision voltage divider network, a precision analog-to-digital converter (such as a 16-bit Σ-Δ precision ADC with integrated programmable gain amplifier), and a digital isolator (such as an SPI isolator ADuM1401 or ISO7741, with a withstand voltage ≥3000V). The high-voltage precision voltage divider divides the 1000V bus voltage to the ADC input range. The precision ADC directly acquires the divided low-voltage analog signal and converts it into a digital signal. The digital isolator electrically isolates the digital signal output by the ADC and transmits it to the main control processing unit 105.

[0031] • Digital isolation communication unit 104: Employs a digital isolation chip with a withstand voltage of ≥3000V (such as SPI isolator ADuM1401 or ISO7741) to achieve electrical isolation communication between the low-voltage precision signal conditioning unit 102, the high-voltage side voltage acquisition unit 103 and the main control processing unit 105, ensuring safe isolation between the high-voltage side and the low-voltage control side.

[0032] • Main control processing unit 105: includes a microcontroller (such as STM32F103) and firmware running on it, used to control the frequency scanning sequence and amplitude setting of the perturbation signal, read the complex impedance data calculated by the low voltage precision signal conditioning unit 102, receive the voltage data transmitted by the high voltage side voltage acquisition unit 103 through digital isolation, run the temperature compensation algorithm, and execute health status assessment and early warning logic.

[0033] • Multi-point temperature acquisition array 106: includes multiple PT1000 platinum resistance temperature sensors distributed on the surface of the battery pack, near the tabs, and key hot spots of the casing. The temperature of each point is acquired through constant current source excitation and precision ADC, providing the main control processing unit 105 with multi-point temperature data required for temperature compensation.

[0034] • External communication module 107: Includes an RS485 transceiver (supporting Modbus RTU protocol) and a WiFi / Bluetooth / 4G wireless communication module, used for data interaction with the charging pile controller, BMS main controller, host computer software or cloud platform.

[0035] Example 2: Internal EIS signal link of the core chip (AD5941) of the low-voltage precision signal conditioning unit like Figure 4 As shown, this embodiment uses AD5941 as the core chip of the low-voltage precision signal conditioning unit 102, and details the interface relationship between its internal EIS signal link and the external high-voltage expansion unit.

[0036] The AD5941 integrates a waveform generator, a high-speed digital-to-analog converter (HSDAC), a gain stage (GAIN), an excitation buffer, a low-power transimpedance amplifier (LPTIA), a multiplexer (MUX), and a 16-bit 800kHz analog-to-digital converter (ADC).

[0037] Excitation signal generation path: A waveform generator generates a sinusoidal or triangular wave digital signal with a preset frequency (0.01Hz~10kHz), which is converted into an analog voltage signal by an HSDAC, amplified by a gain stage, and then output by the excitation buffer through the CE0 pin. In standard single-cell applications, CE0 is directly connected to the battery under test; however, in the high-voltage scheme of this invention, the CE0 pin is not directly connected to the 1000V bus, but is connected to an external high-voltage gate drive circuit (isolated by a digital isolator) to drive the MOSFET gate in the high-voltage power absorption unit 101, thereby indirectly coupling the perturbation signal to the high-voltage battery pack.

[0038] Current response acquisition path: The precision sampling resistor R_sense in the high-voltage power absorption unit 101 converts the current disturbance I_perturb into a differential voltage signal. After being amplified by an external instrumentation amplifier (such as a differential buffer stage composed of ADB688 or AD8694), it is input to AD5941 through the AIN1 pin. AIN1 acquires the voltage response near the battery end (or the sampling resistor end), reflecting the actual amplitude and phase of the current disturbance.

[0039] Voltage response acquisition path (standard AFE internal channel): In the standard single-cell solution, the battery voltage can be directly input through AIN2 / AIN3 / AIN4, buffered by an external operational amplifier (AD8694) or converted by LPTIA, and then acquired by the ADC. However, in the high-voltage solution of this invention, since the withstand voltage of all analog input pins of AD5941 (AIN1~AIN4, CE0, RE0, SE0, etc.) is much lower than the 1000V bus voltage, direct connection to high voltage is strictly prohibited. Therefore, the battery pack port voltage is not directly acquired by AD5941, but is acquired by an independent high-voltage side voltage acquisition unit 103 (see Embodiment 3). Its output is digitally isolated and transmitted to the main control processing unit 105 through an independent SPI or I²C interface.

[0040] Transimpedance Amplifier (LPTIA) and Internal ADC and DFT Engine: The LPTIA is used to convert weak current signals into voltages, and the transimpedance gain is set with programmable load resistors (Rload) and gain resistors (Rgain). In this scheme, the LPTIA is mainly used to process the current response signal from R_sense, which is then digitized by a 16-bit 800kHz ADC after being selected by the MUX. The DFT (Discrete Fourier Transform) or digital correlation calculation engine integrated within the AD5941 directly performs frequency domain analysis on the digitized current and voltage response signals, calculating the complex impedance Z(f) = R(f) + jX(f) at each target frequency. The calculation results are transmitted to the main control processing unit 105 via the SPI interface through the digitally isolated communication unit 104. The main control processing unit 105 does not need to perform complex DFT calculations; it only needs to read the real and imaginary parts of the complex impedance output by the AD5941.

[0041] Key Design Considerations: The AD5941, as the core of the "Low-Voltage Precision Signal Conditioning Unit," functions as a source of perturbation signals, a precise conditioning source for current response signals, and an on-chip computation unit for complex impedance, rather than a receiver of high-voltage signals. The high-voltage power absorption unit 101 and the high-voltage side voltage acquisition unit 103 handle all functions directly interacting with the 1000V bus. The AD5941 always operates on the safe low-voltage side, achieving cross-voltage domain transmission of control and data through a digital isolator.

[0042] Example 3: High-voltage power absorption unit and isolation voltage acquisition circuit like Figure 2 and Figure 3As shown, the high-voltage power absorption unit 101 includes a high-voltage N-channel MOSFET Q1 (1000V withstand voltage, such as IXTH2N150L, ​​low on-resistance, suitable for fine adjustment in the linear region). The drain of Q1 is connected to the positive bus HV+ of the battery pack via a high-voltage fuse F1, and the source is connected to the negative bus HV- via a precision sampling resistor R_sense. The gate receives the perturbation control signal V_ctrl (isolated by a digital isolator) from the CE0 pin of the AD5941 via a gate resistor R_g and a high-speed digital isolation driver.

[0043] TVS diode D1 is connected in parallel between the drain and source of Q1 to suppress bus voltage spikes. The overcurrent detection circuit monitors the voltage across R_sense via a comparator; when the current exceeds a preset safety threshold, it triggers hardware protection logic to forcibly shut down Q1. A temperature sensor (such as an NTC or a PT1000 integrated near the MOSFET) monitors the junction temperature of the power devices in real time to prevent overheating damage.

[0044] During operation, the perturbation control signal V_ctrl is a low-frequency sinusoidal signal (its amplitude controls the gate voltage of Q1 after isolation driving), causing Q1 to operate at a specific operating point in the linear region. The drain current I_d varies sinusoidally at a preset frequency within the microampere to milliampere range, thereby generating a weak voltage fluctuation ΔV on the battery pack bus. Since the product of I_d·ΔV is only in the milliwatt to watt range, its impact on the energy state and thermal state of the battery pack is negligible.

[0045] The high-voltage side voltage acquisition unit 103 includes: - A high-voltage precision voltage divider: composed of multiple high-voltage resistors connected in series (e.g., three 400V withstand voltage, 2MΩ resistors connected in series, with a total voltage division ratio of 1000:1), which divides the 1000V bus voltage to the 1V level; a protection diode and a filter capacitor are connected in parallel at the output of the voltage divider to suppress transient overvoltage and high-frequency noise; - A precision ADC U1 (e.g., a 24-bit Σ-Δ precision ADC with an integrated programmable gain amplifier PGA): directly acquires the low-voltage differential signal output from the voltage divider, with a resolution of 24 bits and a sampling rate that meets the requirements for capturing EIS voltage response signals; this ADC is deployed in an independent power supply area on the high-voltage side, with its analog input directly connected to the voltage divider output and its digital output connected to a digital isolator; - A digital isolator U2 (e.g., a four-channel SPI isolator ADuM1401 or ISO7741): converts the precision ADC... The digital signal output by U1 is electrically isolated and transmitted to the main control processing unit 105. The isolation withstand voltage is ≥3000V, ensuring that the high-voltage side analog ground (GND_sense) and the low-voltage side control ground (GND_control) are completely separated.

[0046] Design Highlights: The high-voltage side voltage acquisition unit 103 adopts a direct link of "voltage divider → precision ADC → digital isolator," eliminating the intermediate isolation operational amplifier, reducing signal conditioning stages, lowering link noise and phase delay, and improving voltage acquisition accuracy and EIS impedance calculation accuracy. The ground terminal (GND_sense) of the high-voltage side voltage acquisition unit 103 and the power ground (GND_power) of the high-voltage power absorption unit 101 are physically separated, connected only at a single point or completely isolated, to prevent the voltage drop (I_perturb × Z_ground) generated by I_perturb on the power ground line from entering the voltage measurement circuit.

[0047] Example 4: Impedance Calculation and Accuracy Assurance In this system, the calculation of complex impedance is performed by the DFT / digital correlation engine integrated within the low-voltage precision signal conditioning unit 102 (AD5941), and the main control processing unit 105 is responsible for reading the calculation results and performing subsequent processing. AD5941 synchronous acquisition: - Current disturbance signal I(f): indirectly obtained through the voltage across R_sense (acquired via internal LPTIA and ADC); - Voltage response signal V(f): electrically isolated from the high-voltage side voltage acquisition unit 103 and input to AD5941 through an independent channel or used as a reference signal for DFT calculation.

[0048] The AD5941's internal DFT engine calculates: Z(f) = V(f) / I(f) = R(f) + jX(f) Because V(f) is acquired through an independent isolated channel and is not affected by power loop noise, even if I_perturb is only in the milliampere range, the weak voltage response (hundreds of microvolts to several millivolts) generated on the battery pack internal resistance (tens of milliohms) can be accurately extracted, ensuring the reliability of the Nyquist plot. The main control processing unit 105 reads the real part R(f) and imaginary part X(f) of the complex impedance output by AD5941 through the SPI interface, without performing DFT calculations, significantly reducing the computational load on the MCU.

[0049] Example 5: Multi-point temperature acquisition and temperature compensation like Figure 5 As shown, the multi-point temperature acquisition array 106 includes PT1000 sensors T1, T2, T3…Tn arranged at different positions on the surface of the battery pack housing. The PT1000 features high accuracy, high stability, and a wide temperature range (-200°C to +850°C), making it suitable for monitoring the surface temperature of the battery.

[0050] After collecting the temperature at various points, the main control processing unit 105 determines the current equivalent temperature T_eq of the battery pack using a weighted average or hotspot priority strategy. The temperature compensation model can employ an Arrhenius-type temperature correction formula: Z_corrected(f) = Z_measured(f) × exp[ E_a / R × (1 / T_ref - 1 / T_eq) ] Where E_a is the activation energy (calibrated according to the battery chemistry system), R is the gas constant, and T_ref is the standard reference temperature (e.g., 25°C or 298.15K). For lithium iron phosphate or lithium manganese iron phosphate battery systems, a linear correction factor based on experimental calibration can also be used. Z_corrected(f) = Z_measured(f) × [1 + k(T_eq - T_ref)] Where k is the temperature correction coefficient, which is obtained by fitting previous experimental data.

[0051] Example 6: Digital Isolation and Multimode Communication Architecture like Figure 6 As shown, the digital isolation communication unit 104 uses a multi-channel digital isolator (such as a four-channel SPI isolator ADuM1401 or ISO7741) to achieve electrical isolation of SPI communication, GPIO control signals and interrupt signals between the low-voltage side MCU and the high-voltage side AFE and isolated ADC. The isolation withstand voltage is ≥3000V, and the common-mode transient immunity (CMTI) is high, ensuring that the common-mode noise of the high-voltage bus will not interfere with the low-voltage control circuit.

[0052] The external communication module 107 includes: - RS485 interface: Connects to the industrial bus of the charging pile or BMS via an isolated RS485 transceiver, supporting the Modbus RTU protocol for real-time uploading of impedance data, temperature data, and alarm status. - 4G / WiFi module: Connects to the main control processing unit 105 via a UART / SPI interface, supporting MQTT or HTTP protocols to upload detection data to a cloud-based big data platform for remote monitoring, historical data tracing, and algorithm model iteration. - Bluetooth module: Used for short-range data interaction with maintenance personnel's mobile phones or tablets in offline portable scenarios, facilitating quick on-site viewing of detection results.

[0053] Example 7: Online Integration Mode (Charging Pile / BMS Application) like Figure 7As shown, in this embodiment, the detection device is integrated inside the charging gun of the electric vehicle DC charging pile or in the charging pile control cabinet. The high-voltage power absorption unit 101 is connected to the vehicle battery pack 100 through the high-voltage DC bus interface of the charging pile. The sensors of the multi-point temperature acquisition array 106 are arranged near the charging gun terminals and the contact surface of the battery pack housing.

[0054] During charging, the main control processing unit 105 communicates with the main controller of the charging pile via RS485 or CAN bus, injecting perturbation signals during charging intervals (such as the constant current-constant voltage switching stage or the low current stage at the end of charging). The AD5941's internal DFT engine calculates the battery pack impedance spectrum in real time. The main control processing unit 105 reads the complex impedance data and combines it with the temperature compensation results, performing a longitudinal comparison with historical charging data through the cloud platform. When the detected impedance real part offset exceeds the first threshold (e.g., >20%) or the low-frequency phase angle offset exceeds the second threshold (e.g., >15°), it is determined that the battery has a risk of thermal runaway, and a warning or suggestion to terminate charging is issued through the charging pile's human-machine interface.

[0055] Example 8: Offline Standalone Mode (Portable Device Application) like Figure 8 As shown, this embodiment encapsulates the testing device as a standalone portable unit, equipped with a high-voltage safety interface conforming to national standards (such as a GB / T 20234.3 DC charging interface or a dedicated high-voltage insulation probe) and a human-machine interface (display screen + buttons / touchscreen). After the testing personnel connect the device to the busbar of the battery pack under test, the device automatically completes frequency scanning (0.01Hz~10kHz), AD5941 internal DFT calculation, main control processing unit temperature compensation, and result display.

[0056] This mode is applicable to: battery pack after-sales maintenance, rapid health assessment before secondary use, post-accident safety screening, and risk assessment before battery recycling. Test data can be synchronized to a mobile app via Bluetooth or uploaded to a cloud archive via 4G.

[0057] Example 9: Setting Excitation Parameters and Safety Boundaries To ensure the safety of the detection process, the current disturbance amplitude in step S2 is set to no more than 1%C of the rated capacity of the battery pack. For example, for a 100Ah battery pack, the disturbance current amplitude should not exceed 1000mA. The frequency scan range covers 0.01Hz to 10kHz, where the 0.01Hz~1Hz band is used to detect diffusion processes and low-frequency polarization characteristics related to lithium dendrites, and the 1Hz~10kHz band is used to detect charge transfer processes and SEI film characteristics.

[0058] The hardware protection thresholds of the high-voltage power absorption unit 101 are set as follows: bus overvoltage protection point 1100V (for 1000V systems), circuit overcurrent protection point 3 times the rated disturbance current, and device overtemperature protection point 85°C. When any protection is triggered, the hardware circuit cuts off the power absorption path within <<10μs to ensure the safety of the tested battery pack and the detection device.

[0059] Example 10: Health Status Assessment and Thermal Runaway Early Warning like Figure 9 As shown, the main control processing unit 105 reads the complex impedance results calculated by the internal DFT engine of the AD5941 and obtains the real part R(f) and imaginary part X(f) data for each target frequency. Based on these data, the main control processing unit 105 plots a Nyquist plot (-Z_imag vs Z_real) and compares the temperature-compensated complex impedance with a preset healthy reference impedance spectrum.

[0060] For a healthy lithium manganese iron phosphate battery, at 50% SOC and 25°C, the Nyquist plot usually shows a regular semicircle plus a low-frequency oblique line. When the battery exhibits abnormalities such as lithium dendrites, electrolyte decomposition, or bulging, the radius of the mid-frequency semicircle increases, and the low-frequency diffusion line is distorted or the phase angle shifts.

[0061] The main control processing unit 105 executes the following early warning logic: when any of the following conditions are met, a thermal runaway risk warning is output: - The offset of the real part of the impedance at the target frequency (e.g., 1Hz) relative to the reference value ΔR / R0 > the first threshold (e.g., 20%); - The phase angle offset of the imaginary part of the impedance at the target frequency Δθ > the second threshold (e.g., 15°); - The multi-point temperature acquisition array 106 detects that the local temperature rise rate dT / dt exceeds the third threshold (e.g., 5°C / min).

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-voltage battery pack electrochemical impedance spectroscopy detection device based on the self-excitation of the battery under test, characterized in that, include: - Low-voltage precision signal conditioning unit, used to generate perturbation control signals and calculate complex impedance through internally integrated discrete Fourier transform or digital correlation method; - The high-voltage power absorption unit is composed of power semiconductor devices with a withstand voltage rating of ≥1000V. It is directly electrically connected between the positive and negative busbars of the high-voltage battery pack under test. Under the drive of the micro-perturbation control signal, it absorbs weak energy from the high-voltage battery pack under test and generates a frequency-controllable current perturbation. - High-voltage side voltage acquisition unit, used to independently acquire the port voltage response signal of the high-voltage battery pack under test under the current disturbance. The high-voltage side voltage acquisition unit is electrically isolated from the low-voltage precision signal conditioning unit and the high-voltage power absorption unit to reduce the impact of current disturbance in the power absorption circuit on the voltage acquisition accuracy. - A digital isolated communication unit is used to transmit the voltage response signal acquired by the high-voltage side voltage acquisition unit and the signal of the low-voltage precision signal conditioning unit to the main control processing unit with electrical isolation, and the isolation withstand voltage is ≥3000V; - The main control processing unit is used to control the frequency and amplitude of the perturbation control signal, read the complex impedance calculated by the low-voltage precision signal conditioning unit, and perform a health status assessment of the battery pack based on the complex impedance and the port voltage response signal. The high-voltage power absorption unit utilizes only the energy stored in the high-voltage battery pack under test, absorbing weak energy at the milliwatt to watt level. The main control processing unit assesses the health status of the battery pack based on the changing trends of the real and imaginary parts of the complex impedance and outputs an early warning when abnormalities occur.

2. The apparatus according to claim 1, characterized in that, The low-voltage precision signal conditioning unit includes a general-purpose electrochemical analog front-end chip and a signal conditioning circuit. The general-purpose electrochemical analog front-end chip integrates a waveform generator, a high-speed digital-to-analog converter, a gain stage, an excitation buffer, a low-power transimpedance amplifier, a multiplexer, an analog-to-digital converter, and a discrete Fourier transform or digital correlation calculation engine. The voltage rating of the general-purpose electrochemical analog front-end chip is lower than the bus voltage of the high-voltage battery pack under test. The power semiconductor device is a high-voltage MOSFET or IGBT, which operates in the linear amplification region or in a controlled switching state, and finely adjusts the current amplitude absorbed from the battery pack through the gate drive signal.

3. The apparatus according to claim 1, characterized in that, The high-voltage power absorption unit also includes an overvoltage protection circuit, an overcurrent protection circuit, and a short-circuit protection circuit. When the detected bus voltage, loop current, or device temperature exceeds a preset threshold, the power absorption path is automatically cut off.

4. The apparatus according to claim 1, characterized in that, The high-voltage side voltage acquisition unit includes a high-voltage precision voltage divider network, a precision analog-to-digital converter (ADC), and a digital isolator. The high-voltage precision voltage divider network is directly connected to the positive and negative busbars of the high-voltage battery pack under test, dividing the busbar voltage to the input range of the precision ADC. The precision ADC directly acquires the low-voltage analog signal output by the high-voltage precision voltage divider network and converts it into a digital signal. The digital isolator electrically isolates the digital signal output by the precision ADC and transmits it to the main control processing unit, with an isolation withstand voltage ≥3000V.

5. The apparatus according to claim 1, characterized in that, The device is integrated as an embedded module into the DC detection port of an electric vehicle DC charging pile or AC charging pile, or into the slave control unit of a battery management system; or, the device is configured as an independent portable device, connected to the high-voltage battery pack under test via a dedicated high-voltage probe or a standard charging interface.

6. The apparatus according to claim 1, characterized in that, The device also includes a multi-point temperature acquisition array, which comprises multiple PT1000 platinum resistance temperature sensors distributed on the surface of the battery pack and key hot spots for acquiring multi-point temperature data. The main control processing unit reads the complex impedance calculated by the low-voltage precision signal conditioning unit and, in conjunction with the multi-point temperature data, performs temperature compensation on the complex impedance using a preset temperature-impedance correction model. The device also includes a multi-channel switching matrix, which supports adaptive configuration and time-division detection of high-voltage battery packs with different string numbers and topologies.

7. The apparatus according to claim 1, characterized in that, The main control processing unit also includes an external communication module, which includes at least an RS485 wired communication interface and one or more wireless communication interfaces such as WiFi, Bluetooth, and 4G cellular network, for uploading detection data to a cloud platform or interacting with a host computer or mobile terminal.

8. A method for detecting high-voltage battery packs based on self-excitation of the tested battery using electrochemical impedance spectroscopy, characterized in that, Includes the following steps: - S1: The high-voltage power absorption unit is directly electrically connected to the positive and negative busbars of the high-voltage battery pack under test. The high-voltage power absorption unit is composed of power semiconductor devices with a withstand voltage rating of ≥1000V. - S2: A perturbation control signal is generated by the low-voltage precision signal conditioning unit to drive the high-voltage power absorption unit, so that the high-voltage power absorption unit absorbs only weak energy from the high-voltage battery pack under test, generating a current perturbation with controllable frequency and amplitude. - S3: The high-voltage side voltage acquisition unit independently acquires the port voltage response signal of the battery pack under the current disturbance. The high-voltage side voltage acquisition unit is electrically isolated from the low-voltage precision signal conditioning unit and the high-voltage power absorption unit. - S4: The low-voltage precision signal conditioning unit calculates the complex impedance of the battery pack at the target frequency using discrete Fourier transform or digital correlation method to generate an electrochemical impedance spectrum; the main control processing unit reads the complex impedance and corrects it using a temperature compensation model, thereby assessing the battery health status.

9. The method according to claim 8, characterized in that, In step S2, the power level of the weak energy is from milliwatts to watts, the amplitude of the current disturbance does not exceed the current value corresponding to 1%C of the rated capacity of the battery pack, and the frequency scanning range of the disturbance control signal is from 0.01Hz to 10kHz.

10. The method according to claim 8, characterized in that, Step S4 is followed by: comparing the temperature-compensated complex impedance with the preset health reference impedance spectrum, and outputting a battery thermal runaway risk warning when the real part of the impedance offset exceeds the first threshold or the phase angle offset of the imaginary part of the impedance exceeds the second threshold.

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