Battery self-discharge test device and test method based on zero impedance

Abstract

The invention relates to the technical field of battery self-discharge testing, in particular to a zero-impedance-based battery self-discharge testing device and a zero-impedance-based battery self-discharge testing method. The battery self-discharge testing device comprises a connector module; the current detection unit comprises a sampling resistor Rsense and a differential amplification circuit, and the sampling resistor Rsense is connected in series in a current input loop; the differential amplification circuit is in bridge connection with the two ends of the Rsense of the sampling resistor and outputs a voltage signal proportional to the self-discharge current Idischarge current; the input end of the voltage detection unit is connected with the four-wire system voltage test terminal, and the open-circuit voltage VOCV of the battery to be tested is sampled in real time; the controllable voltage source module is used for outputting a dynamic compensation voltage Vapplied which is equal to the sum of VOCV and Idischarg * Rcircit, wherein the Vapplied is equal to VOCV + Idischarg * Rcircit; the controller module is used for calculating the real-time voltage drop of the total impedance Rcircuit of the circuit based on the VOCV and the Idischarge, and dynamically adjusting the output of the controllable voltage source, so that the terminal voltage of the battery to be detected is locked as the VOCV; and when the terminal voltage of the to-be-detected battery is stabilized within the range of VOCV + / -0.0001%, determining that the to-be-detected battery enters a constant potential mode, and continuously recording the current value until the current value is stable.

Description

Technical Field

[0001] The invention relates to the technical field of battery self-discharge testing, and in particular to a battery self-discharge testing device and a testing method based on zero impedance. Background Art

[0002] As the global energy crisis becomes increasingly severe, the new energy industry has ushered in an opportunity for rapid development. Secondary energy storage technology represented by lithium-ion batteries has become the research and development focus in the field of green energy due to its excellent performance characteristics. As a typical representative of new clean energy, lithium-ion batteries have been widely used in the power systems of high-end equipment such as smart meters and new energy vehicles due to their zero-pollution characteristics, high energy density and ultra-long cycle life. However, the intrinsic self-discharge phenomenon in this system has caused multiple technical challenges: at the micro level, the self-discharge process causes the energy loss rate of single cells to reach 3-5% / month; at the macro application level, the difference in the self-discharge rate of each unit in the battery pack will cause a chain reaction such as accelerated capacity decay and a sharp reduction in cycle life, and will cause the battery management system (BMS) to misjudge the state of charge (SOC) by as much as 20%, thereby inducing major safety hazards such as over-discharge and thermal runaway of the power battery system.

[0003] Battery self-discharge refers to the phenomenon that the battery will still lose power when it is idle and not in use. The self-discharge of the battery will cause the battery voltage to gradually decrease when there is no load. When the self-discharge of the battery is too large, it is easy to cause the battery voltage to drop below the over-protection voltage during long-term idleness or charging and discharging, seriously reducing the reliability and safety of the battery. Therefore, it is necessary to detect the self-discharge of the battery in the development or application of the battery. However, the existing self-discharge detection requires long-term static observation, resulting in low detection efficiency and poor detection accuracy. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a battery self-discharge test device and test method based on zero impedance, aiming to solve the problem that the prior self-discharge detection requires long-term static observation, resulting in low detection efficiency and poor detection accuracy.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a battery self-discharge test device based on dynamic impedance compensation, comprising:

[0007] The connector module includes: a current test access terminal, a current test output terminal, a four-wire voltage test terminal, and a ground wire terminal. The current test access terminal is connected to the positive electrode of the battery under test to form a current input loop; the current test output terminal is connected to the negative electrode of the battery under test and grounded to form a current output loop; the four-wire voltage test terminal is independently connected to the positive and negative electrodes of the battery under test to form a voltage sampling loop; the ground wire terminal is connected to the negative electrode of the battery under test and is grounded together with the system ground wire;

[0008] The current detection unit includes: a sampling resistor R sense and a differential amplifier circuit. The sampling resistor R sense is connected in series in the current input loop; the differential amplifier circuit is connected across the two ends of the sampling resistor R sense and outputs a voltage signal proportional to the self-discharge current I discharge ;

[0009] The voltage detection unit has its input end connected to the four-wire voltage test terminal and samples the open-circuit voltage V OCV of the battery under test in real time;

[0010] The controllable voltage source module has its positive end connected to the output end of the current detection unit and its negative end grounded, and outputs a dynamic compensation voltage V applied =V OCV +I discharg ×R circuit ;

[0011] The controller module, based on V OCV fed back by the voltage detection unit and I discharge fed back by the current detection unit, calculates the real-time voltage drop of the total circuit impedance R circuit , dynamically adjusts the output of the controllable voltage source to lock the terminal voltage of the battery under test at V OCV , eliminates the influence of the external circuit impedance, and realizes an equivalent zero-impedance environment; when the terminal voltage of the battery under test is stable within the range of V OCV ±0.0001%, it is determined to enter the potentiostatic mode, and the self-discharge current I discharge is given by the controllable voltage source module, and the current value is continuously recorded until it is stable.

[0012] Furthermore, the four-wire voltage test terminal uses gold-plated contacts, the contact resistance is less than 1 mΩ, and it is physically isolated from the current test terminal for wiring;

[0013] The resistance value range of the sampling resistor R sense is 0.1 mΩ to 10 Ω, the accuracy is ±0.05%, the temperature coefficient TCR≤±5 ppm / ℃, and it is connected to the current detection loop through a four-wire Kelvin connection method;

[0014] The differential amplifier circuit includes a zero-drift operational amplifier and an instrumentation amplifier, configured in a two-stage amplification mode, with a total gain of 100 to 1000 times, a bandwidth ≥ 10 kHz, and an input noise density ≤ 10 nV / √Hz;

[0015] The voltage detection unit includes a 24-bit Δ-Σ ADC, a sampling rate ≥ 1 kSPS, a built-in programmable gain amplifier, supports fully differential input, and integrates a digital low-pass filter.

[0016] Furthermore, the controllable voltage source module is a programmable linear power supply, with an output noise ≤ 1 μVRMS, a response time ≤ 10 μs, and a built-in temperature compensation circuit;

[0017] The controller module adopts an adaptive PID control algorithm, and the dynamic adjustment rules include:

[0018] When the voltage deviation ∣V DUT -V OCV ∣> 0.05%, increase the proportional gain K p ;

[0019] When the current fluctuation ΔI discharge > 1%, reduce the integral time T i ;

[0020] Disable the derivative term during the system startup phase and gradually enable it after stabilization;

[0021] The current detection unit is synchronized with the sampling clock of the voltage detection unit, the hardware trigger delay error ≤ 10 ns, and power frequency interference is eliminated through a digital phase-locked loop.

[0022] Furthermore, it also includes:

[0023] An integrated temperature sensor and an NTC thermistor are used to monitor the ambient temperature in real time. The correction formula is:

[0024] R sense (T) = R sense × [1 + α(T - T ref )];

[0025] Among them, α is the temperature drift coefficient of the sampling resistor R sense , T is the ambient temperature, and T ref is the reference temperature benchmark value calibrated through an incubator, with an initial value of 25°C ± 0.1°C;

[0026] A self-calibration module that periodically performs operations: switches to the internal reference voltage source to calibrate the ADC gain and offset every 24 hours; calibrates the sampling resistor R sense, the calibrated currents are three levels: 1 mA, 10 mA, and 100 mA.

[0027] In a second aspect, the present invention provides a battery self-discharge test method based on dynamic impedance compensation, including the following steps:

[0028] Step S1: Circuit impedance calibration:

[0029] Disconnect the battery under test and short-circuit the current test access terminals;

[0030] Inject a stepped test current I test into the short-circuit loop and measure the corresponding total voltage drop V short ;

[0031] Calculate the total circuit impedance and store it in the controller;

[0032] Step S2: Dynamic detection of open-circuit voltage OCV:

[0033] Connect the battery under test to the test device and real-time sample the battery terminal voltage V OCV ;

[0034] Step S3: Dynamic impedance compensation and voltage superposition:

[0035] Measure the real-time self-discharge current I through the current detection unit discharge ;

[0036] Calculate the compensation voltage V comp = I discharge × R circuit ;

[0037] Control the controllable voltage source to output the superimposed voltage V applied = V OCV + V comp to lock the battery terminal voltage under test to V OCV ;

[0038] Step S4: Constant potential mode triggering and current stability determination:

[0039] When the battery terminal voltage under test fluctuates within a range ≤ V OCV × 0.1% for 10 seconds, trigger the constant potential mode;

[0040] In the constant potential mode, the self-discharge current is only given by the controllable voltage source module, and continuously record the current value I discharge ;

[0041] If the current fluctuation is ≤ 1% within 100 consecutive sampling periods, determine that the current is stable and output the final self-discharge rate.

[0042] Furthermore, it further includes:

[0043] Step S5: Temperature Compensation and Adaptive Correction:

[0044] The ambient temperature T is monitored in real time through a temperature sensor, and the circuit impedance is corrected:

[0045] R sense (T) = R sense × [1 + α(T - T ref )]

[0046] where α is the temperature coefficient of the sampling resistor R sense The initial value is calibrated in a constant temperature oven at 25°C ± 0.1°C, and the calibration time is ≥ 30 minutes; ref The short - circuit calibration of step S1 is performed once every 24 hours to update the R

[0047] reference value. sense

[0048] Furthermore, the calibration of the temperature correction coefficient α in step S5 includes: testing the curve of the sampling resistor R sense versus temperature change in a temperature - controlled box; fitting a linear regression model based on impedance measurement data at at least 5 temperature points, fitting the α value by the least - squares method, and the fitting error ≤ 0.5%.

[0049] Furthermore, the real - time self - discharge current measurement in step S3 includes: collecting the voltage drop across the precision sampling resistor R sense through a differential amplifier circuit; sampling at a rate of ≥ 1kSPS using a Σ - Δ ADC with a resolution of ≥ 24 bits.

[0050] Furthermore, the constant - potential control in step S4 uses a PID algorithm, and the parameter settings are: proportional coefficient K p = 0.5 - 2; integral time T i = 1ms - 100ms; derivative time T d = 10μs - 1ms.

[0051] For a battery self - discharge test device and test method based on zero impedance described in the present invention, the beneficial effects are as follows:

[0052] The current test terminals and four - wire voltage test terminals of the connector module are physically isolated and wired, completely separating the current input / output loop from the voltage sampling loop, eliminating the interference of wire resistance on voltage detection at the hardware level, and laying a foundation for subsequent high - precision OCV measurement (error < ±0.05mV); the current detection unit converts the nA - level self - discharge current into a quantifiable voltage signal through a series of precision sampling resistors and a differential amplifier circuit, and its output accuracy (±0.05%) directly supports the dynamic compensation voltage V comp ​The voltage detection unit collects the four-wire terminal voltage in real time, and combines digital low-pass filtering technology to ensure that OCV detection is not affected by high-frequency noise, providing a reliable voltage feedback reference for the controller; the controllable voltage source module is based on V applied =V OCV +I discharge ×R circuit The formula dynamically outputs the compensation voltage, which is linked with the controller module to offset the circuit impedance voltage drop with a response speed of ≤1ms, so that the battery terminal voltage is stabilized at V OCV ±0.0001%; ​​the controller module dynamically adjusts the output of the controllable power supply by comparing the voltage feedback value with the set value in real time, and triggers the constant potential mode after the voltage stabilizes, so that the self-discharge current is only given by the controllable voltage source module, so that the self-discharge current converges quickly and is accurately measured, and finally the current value is quickly stabilized within 5 minutes (the traditional method takes 72 hours), and the measurement error is ≤±0.8%. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a structural schematic diagram of a battery self-discharge test device based on dynamic impedance compensation of the present invention;

[0054] Figure 2 It is a flow chart of a battery self-discharge testing method based on dynamic impedance compensation according to an embodiment of the present invention. DETAILED DESCRIPTION

[0055] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0056] like Figure 1 As shown, the present invention provides a battery self-discharge test device based on dynamic impedance compensation, comprising:

[0057] The connector module includes: a current test access terminal, a current test output terminal, a four-wire voltage test terminal, and a ground terminal. The current test access terminal is connected to the positive electrode of the battery to be tested to form a current input loop; the current test output terminal is connected to the negative electrode of the battery to be tested and grounded to form a current output loop; the four-wire voltage test terminal is independently connected to the positive electrode and the negative electrode of the battery to be tested to form a voltage sampling loop; the ground terminal is connected to the negative electrode of the battery to be tested and is grounded with the system ground wire;

[0058] Current detection unit, including: sampling resistor R sense With the differential amplifier circuit, the sampling resistor R sense Connected in series in the current input loop; the differential amplifier circuit is connected across the sampling resistor R sense Both ends, output and self-discharge current I discharge Proportional voltage signal;

[0059] The voltage detection unit, the input end is connected to the four-wire voltage test terminal, and the open circuit voltage V of the battery to be tested is sampled in real time. OCV ;

[0060] Controllable voltage source module, the positive end is connected to the output end of the current detection unit, the negative end is grounded, and the output dynamic compensation voltage V applied =V OCV +I discharg ×R circuit ;

[0061] The controller module uses the V feedback from the voltage detection unit to OCV The current sensing unit feedback I discharge , calculate the total circuit impedance R circuit The real-time voltage drop is dynamically adjusted to adjust the output of the controllable voltage source so that the voltage at the battery terminal to be tested is locked to V OCV , eliminate the influence of external circuit impedance and achieve an equivalent zero impedance environment; when the voltage of the battery terminal to be tested is stable at V OCV When the current is within ±0.0001%, it is judged to enter the constant potential mode, and the self-discharge current I discharge It is given by the controllable voltage source module, and the current value is continuously recorded until it stabilizes.

[0062] The current test terminal of the connector module is physically isolated from the four-wire voltage test terminal, which completely separates the current input / output circuit from the voltage sampling circuit, eliminates the interference of wire resistance on voltage detection from the hardware level, and lays the foundation for subsequent high-precision OCV measurement (error <±0.05mV); the current detection unit converts the nA-level self-discharge current into a quantifiable voltage signal by connecting a precision sampling resistor in series with a differential amplifier circuit. Its output accuracy (±0.05%) directly supports the dynamic compensation voltage V comp The voltage detection unit collects the four-wire terminal voltage in real time, and combines digital low-pass filtering technology to ensure that OCV detection is not affected by high-frequency noise, providing a reliable voltage feedback reference for the controller; the controllable voltage source module is based on V applied =V OCV +I discharge ×R circuit The formula dynamically outputs the compensation voltage, which is linked with the controller module to offset the circuit impedance voltage drop with a response speed of ≤1ms, so that the battery terminal voltage is stabilized at V OCV ±0.0001%; ​​the controller module dynamically adjusts the output of the controllable power supply by comparing the voltage feedback value with the set value in real time, and triggers the constant potential mode after the voltage stabilizes, so that the self-discharge current is only given by the controllable voltage source module, so that the self-discharge current converges quickly and is accurately measured, and finally the current value is quickly stabilized within 5 minutes (the traditional method takes 72 hours), and the measurement error is ≤±0.8%.

[0063] In some embodiments, the four-wire voltage test terminal uses gold-plated contacts with a contact resistance less than 1 mΩ, and is physically isolated from the current test terminal for wiring;

[0064] Sampling resistor R sense has a resistance value range of 0.1 mΩ to 10 Ω, an accuracy of ±0.05%, a temperature coefficient TCR ≤ ±5 ppm / °C, and is connected to the current detection circuit through a four-wire Kelvin connection method;

[0065] The differential amplifier circuit includes a zero-drift operational amplifier and an instrumentation amplifier, configured in a two-stage amplification mode, with a total gain of 100 to 1000 times, a bandwidth ≥ 10 kHz, and an input noise density ≤ 10 nV / √Hz;

[0066] The voltage detection unit includes a 24-bit Δ-Σ ADC, a sampling rate ≥ 1 kSPS, an internal programmable gain amplifier, supports fully differential input, and integrates a digital low-pass filter.

[0067] The gold-plated contacts of the four-wire terminal can reduce the contact resistance fluctuation (<0.1%), ensuring long-term test consistency, and are especially suitable for high-precision laboratory scenarios. Sampling resistor R sense 's wide resistance value range adapts to different current ranges (1 nA to 10 A), and the ±0.05% accuracy ensures that the current detection error < ±0.1%. The low temperature drift characteristic (5 ppm / °C) makes the impedance calibration error in the full temperature range < ±0.01%. The total gain of the differential amplifier circuit is adjustable from 100 to 1000 times, supporting wide dynamic range current detection; the input noise ≤ 10 nV / √Hz, ensuring the clarity of nA-level signals. The high sampling rate of the voltage detection unit tracks voltage changes in real time, and the digital filter cut-off frequency is adjustable (1 Hz to 100 Hz), suppressing high-frequency interference.

[0068] In some embodiments, the controllable voltage source module is a programmable linear power supply, with an output noise ≤ 1 μVRMS, a response time ≤ 10 μs, and an internal temperature compensation circuit;

[0069] The controller module adopts an adaptive PID control algorithm, and the dynamic adjustment rules include:

[0070] When the voltage deviation ∣V DUT -V OCV ∣ > 0.05%, increase the proportional gain K p ;

[0071] When the current fluctuation ΔI discharge > 1%, reduce the integral time T i ;

[0072] Disable the derivative term during the system startup phase and gradually enable it after stabilization;

[0073] The sampling clocks of the current detection unit and the voltage detection unit are synchronized, the hardware trigger delay error ≤ 10 ns, and the power frequency interference is eliminated by a digital phase-locked loop.

[0074] The low-noise output of the controllable voltage source module avoids superimposed voltage fluctuations, and the response speed at the 10 μs level enables fast voltage locking. The controller module dynamically adjusts parameters to balance the response speed and stability, with an overshoot < 5% and the steady-state time shortened by 30%. Sampling clock synchronization (delay ≤ 10 ns) and the digital phase-locked loop align the timing to eliminate the signal phase difference. The phase-locked loop suppresses the 50 / 60 Hz power frequency interference, and the signal-to-noise ratio is increased by 20 dB.

[0075] When the voltage deviation ∣V DUT -V OCV ∣ > 0.05%, the technical principle of increasing the proportional gain K p : The proportional gain K p directly determines the response intensity of the system to the voltage deviation. When the voltage deviation exceeds the threshold (0.05%), it indicates that the system is in the fast adjustment stage, and the proportional action needs to be enhanced to accelerate convergence.

[0076] Formula expression:

[0077] K p = K p0 + ΔK p * sgn(∣V DUT -V OCV ∣ - 0.05%);

[0078] Among them, K p0 is the initial proportional gain, ΔK p is the dynamic adjustment step size. When the voltage deviation is large, K p increases by 20% - 50%, and the response speed increases by 30% - 60%; it avoids the problem of insufficient response in the startup stage of the traditional fixed K p .

[0079] When the current fluctuation ΔI discharge > 1%, the technical principle of reducing the integral time T i : The integral time T i determines the cumulative speed of the integral action. When the current fluctuation exceeds the threshold (1%), it indicates that there is a steady-state error or external disturbance in the system, and T i needs to be shortened to enhance the integral action.

[0080] Formula expression:

[0081] Among them, γ is the attenuation coefficient (typical value 0.1 - 0.5), T iAfter shortening, the integral action is enhanced by 50% - 80%, and the steady-state error convergence time is reduced by 40%; it suppresses current fluctuations caused by circuit temperature drift or load mutation.

[0082] The strategy for enabling the differential term in stages is as follows:

[0083] (1) Disable the differential term during the startup phase: Reason: When the system starts, the signal noise is large (such as the transient of relay closing), and the differential term amplifies the high-frequency noise, which will cause the control output to jitter.

[0084] Implementation method: u(t) = K p e(t) + K i ∫e(t)dt (during the startup phase, t < t stable ).

[0085] (2) Enable the differential term after stabilization:

[0086] Condition: When the voltage volatility is < 0.02% for 10 consecutive cycles, gradually introduce the differential action.

[0087] Formula:

[0088]

[0089] Among them, f(t) is a smooth transition function (such as f(t) = 1 - exp(-t / τ)), the overshoot is reduced by 50% - 70%, and the adjustment time is shortened by 15% - 25%.

[0090] The synergistic effect of parameters and the system-level effects are as follows:

[0091] Dynamic response optimization:

[0092] Startup phase: High K p + Low T i → Quickly pull the voltage close to the set value, and the response time ≤ 10ms;

[0093] Steady-state phase: Restore the standard K p + Introduce K d → Suppress oscillations, and the steady-state error < ±0.02%.

[0094] Anti-interference ability:

[0095] When the current mutates (such as a ±5% step), T i adapts to shorten, and the system recovery time is reduced from 200ms to 80ms;

[0096] The differential term suppresses voltage overshoot, and the overshoot is reduced from 5% to < 1.5%.

[0097] Linkage with other modules of the system

[0098] Temperature compensation linkage: When temperature drift causes R circuit to change, dynamically adjust K p / T i to compensate for control sensitivity;

[0099] Self - calibration trigger: If the parameter adjustment frequency increases abnormally after long - term operation (e.g., the number of K p adjustments > 100 times per hour), trigger the system self - test process.

[0100] This adaptive PID rule realizes: through dynamic parameter mapping (voltage / current deviation → K p / T i ) and a phased control strategy (disable / enable the derivative term):

[0101] Fast response: The voltage locking time is shortened to the millisecond level;

[0102] High - precision steady state: The measurement error of the self - discharge current ≤ ±0.8%;

[0103] Strong robustness: The anti - interference ability is improved by more than 30%, and the influence of temperature drift is reduced by 70%.

[0104] Effectively solve the core pain points of slow response, large overshoot, and poor anti - interference of traditional fixed - parameter PID in battery test scenarios.

[0105] In some embodiments, the battery self - discharge test device based on dynamic impedance compensation further includes:

[0106] An integrated temperature sensor and an NTC thermistor, used to monitor the ambient temperature in real - time. The correction formula is:

[0107] R sense (T) = R sense ×[1 + α(T - T ref )];

[0108] where α is the temperature drift coefficient of the sampling resistor R sense , T is the ambient temperature, and T ref is the reference temperature benchmark value calibrated by the thermostat, with an initial value of 25°C ± 0.1°C;

[0109] A self - calibration module that periodically performs operations: switches to the internal reference voltage source to calibrate the ADC gain and offset every 24 hours; calibrates the sampling resistor R sense through the short - circuit terminal every 7 days, and the calibration currents are three levels: 1 mA, 10 mA, and 100 mA.

[0110] By integrating a temperature sensor and an NTC thermistor, the PCB temperature drift (α) and the ambient temperature drift (β) are separated, and the impedance calibration error in the full temperature range (-40°C to 85°C) is <±0.1%. The ADC gain / offset is periodically calibrated by a self-calibration module to avoid error accumulation caused by component aging (annual drift <0.01%); multi-current range calibration (1mA / 10mA / 100mA) covers the non-linear characteristics of the circuit impedance.

[0111] As Figure 2 shown, the present invention also provides a battery self-discharge test method based on dynamic impedance compensation, including the following steps:

[0112] Step S1: Circuit impedance calibration:

[0113] Disconnect the battery under test and short-circuit the current test access terminals;

[0114] Inject a stepped test current I test into the short-circuit loop and measure the corresponding total voltage drop V short ;

[0115] Calculate the total circuit impedance and store it in the controller;

[0116] Step S2: Dynamic detection of open-circuit voltage OCV:

[0117] Connect the battery under test to the test device and sample the battery terminal voltage in real time through a four-wire voltage test terminal;

[0118] Step S3: Dynamic impedance compensation and voltage superposition:

[0119] Measure the real-time self-discharge current I discharge through the current detection unit;

[0120] Calculate the compensation voltage V comp = I discharge × R circuit ;

[0121] Control the controllable voltage source to output the superimposed voltage V applied = V OCV + V comp to lock the battery terminal voltage under test to V OCV ;

[0122] Step S4: Constant potential mode trigger and current stability determination:

[0123] When the fluctuation range of the battery terminal voltage under test is ≤ V OCV × 0.1% for 10 seconds continuously, trigger the constant potential mode;

[0124] In the constant potential mode, the self-discharge current is only given by the controllable voltage source module, and the current value I is continuously recordeddischarge ;

[0125] If the current fluctuation is ≤ 1% within 100 consecutive sampling periods, it is determined that the current is stable, and the final self-discharge rate is output.

[0126] The total impedance of the measured circuit (including wires, contacts, switches) is calibrated through the circuit impedance, and the compensation accuracy is improved by 50% compared with the theoretical calculation. The pulsed load disconnection technology instantaneously cuts off the load current, eliminates the polarization effect, and the OCV detection error < ±0.05 mV. The combination of dynamic impedance compensation and voltage superposition with the potentiostatic mode trigger makes the self-discharge current quickly stable (< 5 minutes), while the traditional method takes 72 hours.

[0127] Furthermore, it also includes:

[0128] Step S5: Temperature compensation and adaptive correction:

[0129] The ambient temperature T is monitored in real time through a temperature sensor to correct the circuit impedance:

[0130] R sense (T) = R sense × [1 + α(T - T ref )]

[0131] where α is the temperature coefficient of the sampling resistor R sense The initial value is calibrated through a constant temperature oven at 25°C ± 0.1°C, and the calibration time ≥ 30 minutes; ref The short-circuit calibration in step S1 is performed once every 24 hours to update the R

[0132] reference value. sense

[0133] T ref Calibrated through a constant temperature oven, the fitting error of α ≤ 0.5%, and the measurement error of the self-discharge rate in the full temperature range after correction < ±1%.

[0134] Furthermore, the calibration of the temperature correction coefficient α in step S5 includes: testing the curve of the sampling resistor R sense changing with temperature in a temperature control box; fitting a linear regression model based on the impedance measurement data at at least 5 temperature points, and fitting the α value through the least squares method, with the fitting error ≤ 0.5%. The reliability of the temperature drift model is improved, and the fitting R 2 > 0.99.

[0135] Furthermore, the real-time self-discharge current measurement in step S3 includes: collecting the voltage drop across the precision sampling resistor R sense through a differential amplifier circuit; sampling at a rate of ≥ 1 kSPS using a Σ-Δ ADC with a resolution of ≥ 24 bits, so that the quantization error < 0.001%, supporting nA-level current analysis.

[0136] Further, in step S4, the constant potential control adopts a PID algorithm, and the parameter settings are as follows: proportional coefficient K p = 0.5 to 2; integral time T i = 1 ms to 100 ms; derivative time T d = 10 μs to 1 ms. K p = 0.5 to 2, T i = 1 ms to 100 ms, T d = 10 μs to 1 ms, taking into account both the response speed and stability.

[0137] The above are only preferred embodiments of the present invention, and do not impose any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A battery self-discharge test device based on dynamic impedance compensation, characterized in that, Comprising: A connector module, comprising: a current test access terminal, a current test output terminal, a four-wire voltage test terminal, and a ground wire terminal. The current test access terminal is connected to the positive electrode of the battery under test to form a current input loop; the current test output terminal is connected to the negative electrode of the battery under test and grounded to form a current output loop; the four-wire voltage test terminal is independently connected to the positive and negative electrodes of the battery under test respectively to form a voltage sampling loop; the ground wire terminal is connected to the negative electrode of the battery under test and is common-grounded with the system ground wire; Current detection unit, comprising: sampling resistor R sense and a differential amplifier circuit, the sampling resistor R sense is connected in series in the current input loop; the differential amplifier circuit is connected across the two ends of the sampling resistor R sense and outputs a voltage signal proportional to the self-discharge current I discharge ; The voltage detection unit, with its input terminal connected to the four-wire voltage test terminal, samples the open-circuit voltage V of the battery under test in real time OCV ; A controllable voltage source module, with its positive terminal connected to the output terminal of the current detection unit, its negative terminal grounded, and outputting a dynamic compensation voltage V applied = V OCV + I discharg × R circuit ; The controller module, based on the V fed back by the voltage detection unit OCV and the I fed back by the current detection unit discharge , calculates the total impedance R of the circuit circuit of the real-time voltage drop, dynamically adjusts the output of the controllable voltage source, so that the terminal voltage of the battery under test is locked at V OCV , eliminates the influence of the external circuit impedance, and realizes an equivalent zero-impedance environment; when the terminal voltage of the battery under test is stable within V OCV ±0.0001%, it is determined to enter the potentiostatic mode, and the self-discharge current I discharge is given by the controllable voltage source module, and the current value is continuously recorded until it is stable.

2. The battery self-discharge test device according to claim 1, wherein The four-wire voltage test terminal uses gold-plated contacts, with a contact resistance less than 1 mΩ, and is physically isolated from the current test terminal for wiring; The sampling resistor R sense has a resistance value range of 0.1 mΩ to 10 Ω, an accuracy of ±0.05%, a temperature coefficient TCR ≤ ±5 ppm / °C, and is connected to the current detection circuit through a four-wire Kelvin connection method; The differential amplifier circuit includes a zero-drift operational amplifier and an instrumentation amplifier, configured in a two-stage amplification mode, with a total gain of 100 - 1000 times, a bandwidth ≥ 10 kHz, and an input noise density ≤ 10 nV / √Hz; The voltage detection unit includes a 24-bit Δ-Σ ADC, a sampling rate ≥ 1 kSPS, an internal programmable gain amplifier, supports fully differential input, and integrates a digital low-pass filter; 3. The battery self-discharge test device according to claim 1, wherein The controllable voltage source module is a programmable linear power supply, with an output noise ≤ 1 μV RMS, a response time ≤ 10 μs, and an internal temperature compensation circuit; The controller module adopts an adaptive PID control algorithm, and the dynamic adjustment rules include: When the voltage deviation ∣V DUT - V OCV ∣ > 0.05%, increase the proportional gain K p ; When the current fluctuation ΔI discharge > 1%, reduce the integration time T i ; Disable the derivative term during the system startup phase and gradually enable it after stabilization; The sampling clocks of the current detection unit and the voltage detection unit are synchronized, the hardware trigger delay error ≤ 10 ns, and power frequency interference is eliminated through a digital phase-locked loop; 4. The battery self-discharge test device according to claim 1, characterized in that Also comprising: An integrated temperature sensor and an NTC thermistor for real-time monitoring of the ambient temperature, and the correction formula is: R sense f(T) = R sense × [1 + α(T - T ref )]; Among them, α is the sampling resistor R sense temperature drift coefficient, T is the ambient temperature, T ref is the reference temperature baseline value calibrated by the thermostat, and the initial value is 25°C ± 0.1°C; Self-calibration module, which periodically performs operations: switches to the internal reference voltage source to calibrate the ADC gain and offset every 24 hours; calibrates the sampling resistor R through the short-circuit terminal every 7 days sense , and the calibration currents are three levels: 1 mA, 10 mA, and 100 mA.

5. A battery self-discharge test method based on dynamic impedance compensation, characterized in that, Including the following steps: Step S1: Circuit impedance calibration: Disconnect the battery under test and short-circuit the current test access terminal; Inject a stepped test current I into the short - circuit loop test and measure the corresponding total voltage drop V short ; Calculate the total impedance of the circuit Stored in the controller; Step S2: Open-circuit voltage OCV dynamic detection: Connect the battery under test to the test device, and sample the battery terminal voltage V in real time through a four-wire voltage test terminal OCV ; Step S3: Dynamic impedance compensation and voltage superposition: Measure the real-time self-discharge current I through the current detection unit discharge ; Calculate the compensation voltage V comp = I discharge × R circuit ; Control the output of the controllable voltage source to superimpose the voltage V applied = V OCV + V comp to lock the terminal voltage of the battery under test to V OCV ; Step S4: Constant potential mode trigger and current stability determination: When the terminal voltage of the battery under test fluctuates within a range of ≤V for 10 consecutive seconds OCV ×0.1%, the potentiostatic mode is triggered; In the constant potential mode, the self-discharge current is only given by the controllable voltage source, and the current value I is continuously recorded discharge ; If the current fluctuation ≤ 1% within 100 consecutive sampling periods, determine that the current is stable and output the final self-discharge rate.

6. The battery self-discharge test method according to claim 5, characterized in that, Also comprising: Step S5: Temperature compensation and adaptive correction: Real-time monitor the ambient temperature T through the temperature sensor and correct the circuit impedance: R sense (T) = R sense × [1 + α(T - T ref )] where α is the temperature coefficient of the sampling resistor R sense and T is the initial value calibrated by a constant temperature oven at 25°C ± 0.1°C, and the calibration time is ≥ 30 minutes; ref ​ Perform the short-circuit calibration of step S1 once every 24 hours to update the R sense reference value.

7. The battery self-discharge test method according to claim 6, wherein, The calibration of the temperature correction coefficient α in the step S5 includes: testing the sampling resistor R in a temperature control box sense for the curve of change with temperature; based on the impedance measurement data at at least 5 temperature points, fitting a linear regression model, fitting the value of α by the least squares method, and the fitting error ≤ 0.5%.

8. The battery self-discharge test method according to claim 5, wherein The real-time self-discharge current measurement in step S3 includes: collecting the voltage drop across the precision sampling resistor R through a differential amplifier circuit sense ; sampling by using a Σ-Δ ADC at a rate of ≥1 kSPS with a resolution of ≥24 bits.

9. The battery self-discharge test method according to claim 5, wherein In the constant potential control in step S4, the PID algorithm is adopted, and the parameter settings are as follows: proportional coefficient K p = 0.5 to 2; integral time T i = 1 ms to 100 ms; derivative time T d = 10 μs to 1 ms.

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