Battery self-discharge test device and test method for tracking loop zero current

Abstract

The invention relates to a battery self-discharge test device and test method for tracking loop zero current. According to the battery self-discharge testing device, a current testing access terminal of a connector is connected with the positive electrode of a battery to be tested, a positive electrode voltage testing access terminal and a negative electrode voltage testing access terminal of the connector are connected with the positive electrode and the negative electrode of the battery to be tested respectively, and a ground wire access terminal of the connector is connected with the negative electrode of the battery to be tested; a ground wire output terminal of the connector is grounded; the positive electrode end of the current detection unit is connected with the current test output terminal of the connector; the positive electrode end of the voltage detection unit is connected with the positive electrode voltage test output terminal of the connector, and the negative electrode end of the voltage detection unit is connected with the negative electrode voltage test output terminal of the connector; the positive electrode end of the controllable voltage source is connected with the negative electrode end of the current detection unit, and the negative electrode end of the controllable voltage source is grounded; and the controller is connected with the current detection unit, the voltage detection unit and the controllable voltage source.

Description

Technical Field

[0001] The present invention relates to the technical field of battery self-discharge testing, and particularly to a battery self-discharge testing device and testing method for tracking zero current in a circuit. Background Art

[0002] Self-discharge refers to the phenomenon that the capacity of a battery cell spontaneously decays during open-circuit static state, and its essence is an energy dissipation process that occurs spontaneously within the system. According to the recoverability of capacity loss, it can be divided into: (1) Reversible self-discharge: triggered by physical processes such as double-layer relaxation effect and rebalancing of lithium-ion concentration gradient, and the capacity loss can be restored by charging; (2) Irreversible self-discharge: resulting from continuous side reactions inside the battery, mainly including: redox reactions between the positive electrode material and the electrolyte (such as oxygen evolution on the surface of NCM ternary material); continuous lithium consumption caused by the instability of the SEI film on the negative electrode; decomposition reactions triggered by trace impurities in the electrolyte (such as water content > 20 ppm); micro-shorts caused by manufacturing defects (such as diaphragm defects, metal dust pollution, etc.).

[0003] At the module / battery pack level, cells with inconsistent self-discharge rates will produce significant SOC dispersion after storage. Experimental data shows that when the difference in self-discharge rates of cells exceeds 0.1% / day, the SOC difference can reach more than 15% after 3 months of static storage, leading to the following three problems: Decrease in available capacity: Restricted by the cell with the lowest SOC, the system capacity decays faster; Increase in safety risks: The risks of overcharging for high-SOC cells and over-discharging for low-SOC cells are doubled; Reduction in cycle life: Inconsistency accelerates capacity decay, and the life loss reaches 20% - 30%;

[0004] Currently, mainstream lithium battery manufacturers adopt a "high-temperature aging + normal-temperature static storage" screening scheme: High-temperature aging (in an environment of 45°C - 60°C) accelerates side reactions and shortens the detection cycle; Normal-temperature static storage (in a 25°C environment) is used for the final determination of capacity difference; This method needs to balance the contradiction between detection accuracy and time cost: Although extending the static storage time (usually a static storage cycle of 7 - 15 days) can improve the detection rate of abnormal cells, it will cause: Increase in production line residence time, increase in product inventory cost, and decrease in production capacity utilization rate. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a battery self-discharge testing device and testing method for tracking zero current in a circuit, aiming to solve the problems that traditional self-current testing methods require static storage for several days to several weeks, resulting in an increase in production line residence time, an increase in product inventory cost, and a decrease in production capacity utilization rate.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention discloses a battery self-discharge testing device for tracking zero current in a circuit, comprising:

[0008] A connector, wherein the current test access terminal of the connector is connected to the positive electrode of the battery under test, the positive voltage test access terminal and the negative voltage test access terminal of the connector are respectively connected to the positive electrode and the negative electrode of the battery under test, the ground wire access terminal of the connector is connected to the negative electrode of the battery under test, and the ground wire output terminal of the connector is grounded;

[0009] A current detection unit, wherein the positive terminal of the current detection unit is connected to the current test output terminal of the connector;

[0010] A voltage detection unit, wherein the positive terminal of the voltage detection unit is connected to the positive voltage test output terminal of the connector, and the negative terminal of the voltage detection unit is connected to the negative voltage test output terminal of the connector;

[0011] A controllable voltage source, wherein the positive terminal of the controllable voltage source is connected to the negative terminal of the current detection unit, and the negative terminal of the controllable voltage source is grounded;

[0012] A controller, which is connected to the current detection unit, the voltage detection unit and the controllable voltage source. The controller is configured to dynamically adjust the output of the controllable voltage source, and process the data of the current detection unit and the voltage detection unit in real time. When the current detection unit detects that the current stabilizes at a threshold value close to zero, the voltage value at this time is recorded by the voltage detection unit as the target voltage, and the controllable voltage source is controlled to switch to the constant potential mode and output with the target voltage, so as to eliminate the initial polarization and extract the steady-state current, and obtain the self-discharge current of the battery under test.

[0013] Further, the current detection unit adopts a 24-bit Σ-Δ ADC with a resolution of 10 nA, a bandwidth of 1 MHz, and supports a dynamic range of 0.1 μA - 10 mA, which is used to accurately capture the zero-current threshold and suppress transient interference to ensure the microampere-level resolution of the self-discharge current; the voltage detection unit uses a seven-and-a-half-digit digital multimeter module with a voltage accuracy of ±(0.00015% reading + 7.5 μV), which is used to obtain a stable open-circuit voltage during the zero-current tracking stage and provide a high-precision feedback signal for the constant potential mode.

[0014] Further, it further includes: a temperature sensor, which is integrated on the surface of the connector, and is used to collect the temperature of the battery under test in real time and transmit it to the controller;

[0015] The controller is configured to dynamically correct the self-discharge current according to the temperature data, normalize the measured value to the standard temperature through the Arrhenius equation, and eliminate the influence of temperature fluctuations on the zero-current detection accuracy.

[0016] Further, the controllable voltage source is based on a DAC + operational amplifier architecture, with an output range of ±5V, a resolution of 4.7nV, supporting four-quadrant operation, and is used to dynamically output or absorb compensation current in the potentiostatic mode to maintain the microvolt-level stability of the battery voltage.

[0017] Further, the connector uses a four-wire Kelvin connection, with a contact resistance <1mΩ, and uses gold-plated contacts and shielded cables to eliminate the contact resistance voltage drop and electromagnetic interference, ensuring the detection accuracy of microampere-level current and microvolt-level voltage.

[0018] In a second aspect, a method for testing the self-discharge of a battery by tracking the zero current of a loop includes the following steps:

[0019] Step 1: Close the switch to connect the controllable voltage source to the battery;

[0020] Step 2: Gradually adjust the output voltage of the controllable voltage source, and the current detection unit monitors the current in real time until the current detected by the current detection unit stabilizes at a threshold close to zero, and record the voltage value at this time as the target voltage through the voltage detection unit;

[0021] Step 3: Switch the controllable voltage source to the potentiostatic mode, and the output voltage of the controllable voltage source in the potentiostatic mode is the target voltage measured in the previous step;

[0022] Step 4: Record in real time the compensation current required for the controllable voltage source to maintain the target voltage, and calculate the self-discharge current by analyzing the change of the compensation current over time;

[0023] Step 5: Verify the stability of the compensation current. If the standard deviation exceeds the threshold, trigger an alarm and retest.

[0024] Further, in step 4, it includes an initial polarization elimination process and a steady-state current extraction process;

[0025] The specific process of initial polarization elimination is as follows: After the controllable voltage source is switched to the potentiostatic mode, the current within a preset time period contains a significant double-layer effect, and the transient component is stripped by exponential fitting: I comp (t) = I sd + I0e -t / τ , where I comp (t) is the real-time compensation current, I sd is the self-discharge current, I0 is the initial transient current amplitude at time t = 0, t is the current acquisition time, τ is the characteristic time parameter describing the dynamic process of double-layer charge and discharge. When t > N*τ, N is a positive integer, the initial polarization is eliminated, the compensation current tends to be stable, and I comp ≈ I sd ;

[0026] The specific process of steady-state current extraction is as follows: During the steady-state interval, the current detection unit collects current data at a preset sampling frequency. After using moving average filtering to reduce noise on the collected current data, the mean value is taken as the self-discharge current of the battery.

[0027] Furthermore, in step 4, there is also a temperature compensation and correction process. The temperature compensation and correction process specifically normalizes the measured value according to the Arrhenius equation:

[0028]

[0029] I sd(T) is the self-discharge current of the battery at the standard temperature, I sd(meas) is the E a is the activation energy of the reaction, R is the molar gas constant, T ref is the standard temperature, and T is the average temperature collected by the temperature sensor during the test.

[0030] Furthermore, by measuring the self-discharge currents at 20°C, 25°C, and 30°C, fitting the slope based on the Arrhenius equation, the activation energy E a =-k·R.

[0031] Furthermore, the preset multiple is 5 times, which is determined based on the statistical distribution characteristics of the double-layer time constant τ, and the determination condition for the steady-state interval is that the current fluctuation is less than 1% for 10 consecutive minutes.

[0032] The beneficial effects of a battery self-discharge test device and test method for tracking zero current of a tracking loop described in the present invention are as follows:

[0033] Traditional self-discharge tests require the battery to be static for a long time to eliminate the polarization effect. However, this device dynamically adjusts the controllable voltage source through the controller, and then actively adjusts the external voltage to force the loop current to zero, quickly canceling the battery polarization voltage and significantly shortening the test preparation time. In the zero-current state, there is no polarization voltage drop inside the battery, and the voltage detection unit directly measures the true open-circuit voltage (OCV), avoiding the interference of the polarization voltage on the subsequent self-discharge current calculation. By adjusting the external voltage in real time to match the real-time OCV of the battery, the loop current is ensured to be stable, avoiding errors introduced by voltage drift caused by battery self-discharge. In the constant potential mode, the controllable voltage source maintains the target voltage, making the battery in a quasi-static equilibrium state. At this time, the self-discharge current is directly measured by the current detection unit, without relying on long-term static or complex mathematical model derivation, and the test efficiency is significantly improved. Through the use of connectors, the current and voltage detections use independent loops, avoiding the influence of contact resistance caused by shared wires on the measurement accuracy (in traditional series detections, contact resistance will cause voltage measurement deviation). The ground wire access terminal is directly connected to the negative electrode of the battery, ensuring that the test loop is reliably grounded and preventing the high-precision detection circuit from being damaged due to potential fluctuations. The controller integrates functions such as dynamic voltage regulation, threshold judgment, and mode switching, reducing manual intervention and lowering the operation complexity. By setting the "threshold range close to zero" (such as ±1 μA), it is compatible with the small current fluctuations of different battery models, improving the universality of the device. Traditional methods require static for several days to several weeks, and this device can complete the test within several hours through zero-current tracking and constant potential control, reducing the production line residence time, lowering the product inventory cost, and improving the production capacity utilization rate. Brief Description of the Drawings

[0034] Figure 1 is the block diagram of the battery self-discharge test device for tracking zero current in the loop of the present invention;

[0035] Figure 2 is the flow schematic diagram of the battery self-discharge test method for tracking zero current in the loop of the present invention. Detailed Embodiments

[0036] The present invention will be further described below in conjunction with the drawings and specific embodiments.

[0037] As Figure 1 shown, the present invention provides a battery self-discharge test device for tracking zero current in the loop, including:

[0038] A connector, the current test access terminal of the connector is connected to the positive electrode of the battery to be tested, the positive voltage test access terminal and the negative voltage test access terminal of the connector are respectively connected to the positive electrode and the negative electrode of the battery to be tested, the ground wire access terminal of the connector is connected to the negative electrode of the battery to be tested, and the ground wire output terminal of the connector is grounded;

[0039] A current detection unit, the positive terminal of the current detection unit is connected to the current test output terminal of the connector;

[0040] A voltage detection unit, the positive terminal of the voltage detection unit is connected to the positive voltage test output terminal of the connector, and the negative terminal of the voltage detection unit is connected to the negative voltage test output terminal of the connector;

[0041] A controllable voltage source, the positive terminal of the controllable voltage source is connected to the negative terminal of the current detection unit, and the negative terminal of the controllable voltage source is grounded;

[0042] A controller, the controller is connected to the current detection unit, the voltage detection unit and the controllable voltage source. The controller is configured to dynamically adjust the output of the controllable voltage source, and process the data of the current detection unit and the voltage detection unit in real time. When the current detection unit detects that the current stabilizes at a threshold close to zero, the voltage value at this time is recorded by the voltage detection unit as the target voltage, and the controllable voltage source is controlled to switch to the constant potential mode and output with the target voltage, so as to achieve initial polarization elimination and steady-state current extraction, and obtain the self-discharge current of the battery under test.

[0043] Traditional self-discharge tests require the battery to be static for a long time to eliminate the polarization effect. However, this device dynamically adjusts the controllable voltage source through the controller, and then actively adjusts the external voltage to force the loop current to zero, quickly canceling the battery polarization voltage and greatly shortening the test preparation time. In the zero-current state, there is no polarization voltage drop inside the battery, and the voltage detection unit directly measures the true open-circuit voltage (OCV), avoiding the interference of the polarization voltage on the subsequent self-discharge current calculation. By adjusting the external voltage in real time to match the real-time OCV of the battery, the loop current is ensured to be stable, avoiding errors introduced by voltage drift caused by battery self-discharge. In the constant potential mode, the controllable voltage source maintains the target voltage, making the battery in a quasi-static equilibrium state. At this time, the self-discharge current is directly measured by the current detection unit, without relying on long-term static or complex mathematical model derivation, and the test efficiency is significantly improved. Through the use of the connector, the current and voltage detections adopt independent loops, avoiding the influence of contact resistance caused by shared wires on the measurement accuracy (contact resistance in traditional series detection will cause voltage measurement deviation). The ground wire access terminal is directly connected to the negative electrode of the battery to ensure reliable grounding of the test loop and prevent damage to the high-precision detection circuit due to potential floating. The controller integrates functions such as dynamic voltage regulation, threshold judgment, and mode switching, reducing manual intervention and lowering the operation complexity. By setting the range of "threshold close to zero" (such as ±1 μA), it is compatible with the small current fluctuations of different battery models and improves the universality of the device. Traditional methods require static for several days to several weeks. This device can complete the test within several hours through zero-current tracking and constant potential control, reducing the production line residence time, lowering the product inventory cost, and improving the production capacity utilization rate.

[0044] Further, the current detection unit uses a 24-bit Σ-Δ ADC with a resolution of 10 nA, a bandwidth of 1 MHz, and supports a dynamic range of 0.1 μA - 10 mA. It is used to accurately capture the zero-current threshold and suppress transient interference, ensuring a microampere-level resolution for the self-discharge current. The voltage detection unit uses a seven-and-a-half-digit digital multimeter module with a voltage accuracy of ±(0.00015% reading + 7.5 μV). It is used to obtain a stable open-circuit voltage during the zero-current tracking phase and provide a high-precision feedback signal for the potentiostatic mode.

[0045] Further, the battery self-discharge test device for tracking zero current in the tracking loop further includes: a temperature sensor integrated on the surface of the connector, which collects the temperature of the battery under test in real time and transmits it to the controller.

[0046] The controller is configured to dynamically correct the self-discharge current according to the temperature data, normalize the measured value to the standard temperature through the Arrhenius equation, and eliminate the influence of temperature fluctuations on the zero-current detection accuracy.

[0047] Further, the controllable voltage source is based on a DAC + operational amplifier architecture, with an output range of ±5V, a resolution of 4.7 nV, and supports four-quadrant operation. It is used to dynamically output or absorb compensation current in the potentiostatic mode to maintain the microvolt-level stability of the battery voltage.

[0048] Further, the connector uses a four-wire Kelvin connection with a contact resistance <1 mΩ, and gold-plated contacts and shielded cables are used to eliminate the contact resistance voltage drop and electromagnetic interference, ensuring the detection accuracy of microampere-level current and microvolt-level voltage.

[0049] As Figure 2 shown, the present invention also provides a battery self-discharge test method for tracking zero current in the tracking loop, including the following steps:

[0050] Step 1: Close the switch to connect the controllable voltage source to the battery.

[0051] Step 2: Gradually adjust the output voltage of the controllable voltage source, and the current detection unit monitors the current in real time until the current detection unit detects that the current stabilizes at a threshold close to zero. Record the voltage value at this time as the target voltage through the voltage detection unit.

[0052] Step 3: Switch the controllable voltage source to the potentiostatic mode, and the output voltage of the controllable voltage source in the potentiostatic mode is the target voltage measured in the previous step.

[0053] Step 4: Record in real time the compensation current required for the controllable voltage source to maintain the target voltage, and calculate the self-discharge current by analyzing the change of the compensation current over time.

[0054] Step 5: Verify the stability of the compensation current. If the standard deviation exceeds the threshold, trigger an alarm and retest.

[0055] Rapid elimination of polarization effect: Traditional methods rely on battery standing (from several hours to several days) to wait for polarization dissipation, while this method directly cancels the battery polarization voltage by actively adjusting the external voltage to make the loop current zero, shortening the polarization elimination time to the minute level.

[0056] In the zero-current state, there is no polarization voltage drop or ohmic voltage drop inside the battery, and the voltage detection unit directly measures the interference-free OCV, avoiding the voltage measurement deviation caused by residual polarization in traditional methods (the error can be reduced to less than 0.05 mV). Traditional methods need to indirectly infer the self-discharge current through the voltage decay rate after long-term standing, while this method directly characterizes the self-discharge current through the constant-voltage compensation current, eliminating the mathematical model assumption errors (such as temperature drift, capacity estimation error). In the potentiostatic mode, the controllable voltage source continuously matches the real-time OCV of the battery to ensure that the battery is always in a quasi-static equilibrium state during the test, avoiding the influence of voltage changes caused by self-discharge on the measurement results. By statistically calculating the standard deviation of the compensation current (such as setting a threshold of ±5 nA), environmental interference (such as sudden temperature change, poor contact) or battery abnormalities (such as micro-short circuit) can be automatically identified, avoiding the accumulation of invalid data. After the over-standard alarm is triggered, the test process is automatically restarted, reducing manual intervention, especially suitable for the detection scenario of batch battery production lines.

[0057] Furthermore, in step 4, it includes an initial polarization elimination process and a steady-state current extraction process;

[0058] The specific initial polarization elimination process is as follows: After the controllable voltage source switches to the potentiostatic mode, the current within a preset time period contains a significant double-layer effect. The transient component is stripped through exponential fitting: I comp (t) = I sd + I0e -t / τ , where I comp (t) is the real-time compensation current, I sd is the self-discharge current, I0 is the initial transient current amplitude at time t = 0, t is the current acquisition time, τ is the characteristic time parameter describing the dynamic process of double-layer charge and discharge. When t > N*τ, N is a positive integer, the initial polarization is eliminated, and the compensation current tends to be stable, I comp ≈ I sd ;

[0059] The specific steady-state current extraction process is as follows: During the steady-state interval, the current detection unit collects current data at a preset sampling frequency. After using moving average filtering to reduce noise for the collected current data, the mean value is taken as the self-discharge current of the battery.

[0060] The dynamic characteristics of the electric double layer effect (τ is usually in the order of seconds) are different from those of Ohmic polarization / concentration polarization (τ is in the order of minutes). Exponential fitting can specifically strip the transient component of the electric double layer, avoiding over-compensation or under-compensation problems of the traditional "one-size-fits-all" static method. Dynamically adjust the waiting time (such as 5τ) according to the fitted τ instead of a fixed duration, avoiding ineffective waiting for high internal resistance batteries (τ is larger) or premature truncation of low internal resistance batteries (τ is smaller), and improving the polarization elimination efficiency by more than 30%. Moving average filtering can suppress the thermal noise of the current detection unit (such as ±10nA) and environmental electromagnetic interference (such as 50Hz power frequency noise), improving the effective resolution from the nA level to the sub-nA level (such as 0.2nA). Mean extraction cancels out temperature drift (such as 0.1nA / °C) or small fluctuations of the controllable voltage source (such as ±1μV), ensuring long-term test stability. Automatically determine the steady-state interval through the smoothness of the filtered data (such as variance <0.5nA 2 ) to avoid the subjectivity of manual observation and improve the automation level of the test process.

[0061] For example, in the sorting of power battery production lines: set τ = 30s (typical lithium-ion battery), N = 5 → enter the steady state after waiting for 150s; moving average window = 10s (sampling frequency 10Hz → 100-point filtering), standard deviation threshold = 0.3nA. Thus, the single-cell test time is compressed from the traditional 6 hours to 5 minutes, and the production capacity is increased by 70 times.

[0062] For example, in high-precision laboratory tests: extend the acquisition to t = 10τ (fully covering concentration polarization), and the mean calculation duration ≥ 30 minutes; make the measurement uncertainty of the self-discharge current <0.1nA (meeting the ISO 12405-4 standard).

[0063] Furthermore, in step 4, a temperature compensation and correction process is also included. The temperature compensation and correction process specifically normalizes the measured value according to the Arrhenius equation:

[0064]

[0065] I sd(T) is the self-discharge current of the battery at the standard temperature, and I sd(meas) is during the steady-state current extraction process E a is the reaction activation energy, R is the molar gas constant, T ref is the standard temperature, and T is the average temperature collected by the temperature sensor during the test.

[0066] The self-discharge current is highly sensitive to temperature (the self-discharge rate may double for every 10°C increase in temperature). Traditional methods require a strictly constant temperature environment (±0.5°C) to suppress errors. This method quantifies the temperature effect through the Arrhenius equation, allows testing under variable temperature conditions (such as ±5°C fluctuations), and normalizes the results to a standard temperature, improving the data comparability by more than 90% under different environments. Calculate the average temperature T based on the real-time collected temperature data (such as sampling every 10 seconds), and update the compensation coefficient in real time to avoid the lag of traditional offline compensation.

[0067] For different battery systems (such as lithium-ion battery E a ≈50 kJ / mol, lead-acid battery E a ≈30 kJ / mol), preset the corresponding E a parameter library, and automatically match through the controller without manual intervention.

[0068] Furthermore, by measuring the self-discharge current at 20°C, 25°C, and 30°C, fitting the slope based on the Arrhenius equation, and calculating the activation energy E a =-k·R.

[0069] Traditional methods use the general E a value in the literature (such as 50 kJ / mol often taken for lithium-ion batteries), but the E a of actual batteries varies due to material formulations (such as NCM622 vs LFP) and aging degree (thickening of the SEI film). Through actual measurement and fitting, obtain the true E a of the battery under test, reducing the compensation error from ±15% to ±2% and eliminating the influence of material differences.

[0070] Example: The measured E a of an aged NCM811 battery is 58 kJ / mol (higher than 52 kJ / mol of a new battery), reflecting that the thickening of the SEI film leads to an increase in the energy barrier of the self-discharge reaction. The calculated value of the self-discharge current after correction is more in line with the actual attenuation rate.

[0071] Three-point fitting can better suppress random errors than single-point or two-point measurements, and the goodness of fit (R 2 ) can reach more than 0.99. Even when the test temperature exceeds the range of 20 - 30°C (such as 15°C or 35°C), the compensation value can still be extrapolated with high precision through the equation, improving the reliability of temperature compensation extrapolation.

[0072] Further, the preset multiple is 5 times, determined based on the statistical distribution characteristics of the double-layer time constant τ, and the determination condition for the steady-state interval period is that the current fluctuation is less than 1% continuously for 10 minutes. The 1% fluctuation threshold can filter out environmental noise (such as ±0.5 nA) and device thermal noise, ensuring that the signal-to-noise ratio of the steady-state signal > 40 dB. The 10-minute continuous determination condition avoids false acceptance caused by instantaneous stability (such as accidental 30-second stability), and the false positive rate is reduced from 5% of the traditional method to < 0.1%. For high self-discharge current batteries (such as I s = 10 μA), 1% corresponds to a 100 nA fluctuation, and the threshold is dynamically associated with the current amplitude, avoiding the compatibility problem of a fixed absolute value threshold (such as ±1 nA) for large and small currents.

[0073] The above is only a preferred embodiment of the present invention, and does 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 for tracking zero current of a loop, characterized in that, Comprising: A connector, the current test access terminal of the connector is connected to the positive electrode of the battery under test, the positive electrode voltage test access terminal and the negative electrode voltage test access terminal of the connector are respectively connected to the positive electrode and the negative electrode of the battery under test, the ground wire access terminal of the connector is connected to the negative electrode of the battery under test, and the ground wire output terminal of the connector is grounded; A current detection unit, the positive terminal of the current detection unit is connected to the current test output terminal of the connector; A voltage detection unit, the positive terminal of the voltage detection unit is connected to the positive electrode voltage test output terminal of the connector, and the negative terminal of the voltage detection unit is connected to the negative electrode voltage test output terminal of the connector; A controllable voltage source, the positive terminal of the controllable voltage source is connected to the negative terminal of the current detection unit, and the negative terminal of the controllable voltage source is grounded; A controller, the controller is connected to the current detection unit, the voltage detection unit and the controllable voltage source, and the controller is configured to dynamically adjust the output of the controllable voltage source, and process the data of the current detection unit and the voltage detection unit in real time. When the current detection unit detects that the current is stable at a threshold value close to zero, the open circuit voltage at this time is recorded by the voltage detection unit as the target voltage, and the controllable voltage source is controlled to switch to the constant potential mode and output with the target voltage, so as to eliminate the initial polarization and extract the steady-state current, and obtain the self-discharge current of the battery under test.

2. The battery self-discharge test device for tracking zero current of a loop according to claim 1, wherein The current detection unit uses a 24-bit Σ-Δ ADC, with a resolution of 10 nA, a bandwidth of 1 MHz, and supports a dynamic range of 0.1 μA - 10 mA, which is used to accurately capture the zero current threshold and suppress transient interference to ensure the microampere-level resolution of the self-discharge current; the voltage detection unit uses a seven-and-a-half-digit digital multimeter module, with a voltage accuracy of ±(0.00015% reading + 7.5 μV), which is used to obtain a stable open circuit voltage during the zero current tracking stage and provide a high-precision feedback signal for the constant potential mode.

3. The battery self-discharge test device for tracking zero current of a loop according to claim 1, wherein Also comprising: A temperature sensor, the temperature sensor is integrated on the surface of the connector, and the temperature of the battery under test is collected in real time and transmitted to the controller; The controller is configured to dynamically correct the self-discharge current according to the temperature data, normalize the measured value to the standard temperature through the Arrhenius equation, and eliminate the influence of temperature fluctuations on the zero current detection accuracy.

4. The battery self-discharge test device for tracking zero current of a loop according to claim 1, characterized in that, The controllable voltage source is based on a DAC + operational amplifier architecture, with an output range of ±5 V, a resolution of 4.7 nV, and supports four-quadrant operation, which is used to dynamically output or absorb compensation current in the constant potential mode to maintain the microvolt-level stability of the battery voltage.

5. The battery self-discharge test device for tracking zero current of a loop according to claim 1, characterized in that The connector uses a four-wire Kelvin connection, with a contact resistance <1 mΩ, and uses gold-plated contacts and shielded cables to eliminate the contact resistance voltage drop and electromagnetic interference, and ensure the detection accuracy of microampere-level current and microvolt-level voltage.

6. A battery self-discharge test method for tracking zero current in a loop, characterized in that, Including the following steps: Step 1: Close the switch to connect the controllable voltage source to the battery; Step 2: Gradually adjust the output voltage of the controllable voltage source, and the current detection unit monitors the current in real time until the current detection unit detects that the current is stable at a threshold value close to zero, and the voltage value at this time is recorded by the voltage detection unit as the target voltage; Step 3: Switch the controllable voltage source to the potentiostatic mode, and the output voltage of the controllable voltage source in the potentiostatic mode is the target voltage measured in the previous step; Step 4: Record in real time the compensation current required for the controllable voltage source to maintain the target voltage, and calculate the self-discharge current by analyzing the change of the compensation current over time; Step 5: Verify the stability of the compensation current. If the standard deviation exceeds the threshold, trigger an alarm and retest.

7. The battery self-discharge test method for tracking zero current of a loop according to claim 6, characterized in that, In Step 4, it includes an initial polarization elimination process and a steady-state current extraction process; The specific process of initial polarization elimination is as follows: after the controllable voltage source is switched to the potentiostatic mode, the current within the preset time period contains a significant double-layer effect, and the transient component is stripped through exponential fitting: I comp (t) = I sd + I0e -t / τ , where I comp (t) is the real-time compensation current, I sd is the self-discharge current, I0 is the initial transient current amplitude at time t = 0, t is the current acquisition time, τ is the characteristic time parameter describing the dynamic process of double-layer charge and discharge. When t > N*τ, N is a positive integer, the initial polarization is eliminated, and the compensation current tends to be stable, I comp ≈ I sd ; The specific process of steady-state current extraction is as follows: During the steady-state interval, the current detection unit collects current data at a preset sampling frequency. After using moving average filtering to reduce noise on the collected current data, the mean value is taken as the self-discharge current of the battery.

8. The method for testing the self-discharge of a battery by tracking the zero current of a loop according to claim 7, characterized in that, In Step 4, it also includes a temperature compensation correction process. The temperature compensation correction process is specifically to perform temperature normalization on the measured value according to the Arrhenius equation: I sd(T) is the self-discharge current of the battery at the standard temperature, I sd(meas) during the steady-state current extraction process E a is the reaction activation energy, R is the molar gas constant, T ref is the standard temperature, and T is the average temperature collected by the temperature sensor during the test.

9. The method for testing the self-discharge of a battery by tracking the zero current of a loop according to claim 8, characterized in that By measuring the self-discharge current at 20 °C, 25 °C, and 30 °C, fitting the slope based on the Arrhenius equation, and calculating the activation energy E a = -k·R.

10. The method for testing the self-discharge of a battery by tracking the zero current of a tracking circuit according to claim 7, characterized in that, The preset multiple is 5 times, which is determined based on the statistical distribution characteristics of the double-layer time constant τ, and the determination condition for the steady-state interval period is that the current fluctuation is less than 1% for 10 consecutive minutes.

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