A battery self-discharge detection method based on reverse dynamic current excitation

Abstract

The present invention discloses a battery self-discharge detection method based on reverse dynamic current excitation, and the method comprises the following steps: step one: battery self-discharge determination; step two: battery self-discharge detection device construction; step three: battery self-discharge detection process step setting and testing; step four: battery self-discharge current result output. The main principle of this method is the charge conservation formula. Through a short-term reverse excitation current, a small amount of capacity is quickly charged without affecting the safety state of the battery, and then the self-discharge current is used to clear it, thereby realizing accurate calculation of the self-discharge current. The present invention does not require long-term current and voltage testing, and at the same time, combined with the temperature correction scheme of the Nernst equation, it avoids the decrease in measurement accuracy caused by environmental changes, and provides an effective solution for further clarifying the health status information inside the battery and assisting the development of the next generation of batteries.

Description

Technical Field

[0001] The invention belongs to the technical field of battery detection, and relates to a battery self-discharge detection method, and in particular to a battery self-discharge detection method based on reverse dynamic current excitation. Background Art

[0002] Lithium-ion batteries are widely used in 3C digital, transportation and logistics, special operations and other fields due to their high voltage, high power and long cycle characteristics. However, they usually have spontaneous discharge behavior after charging, which causes the battery power to gradually dissipate when not in use. Therefore, monitoring the self-discharge current of the battery is crucial to maintaining the stable operation of the battery system. At present, the monitoring method of lithium-ion battery self-discharge mainly focuses on the continuous detection of current and voltage. Although the self-discharge current of the battery can be obtained, the detection time is relatively long, usually 10 to 20 days. At the same time, it is greatly affected by temperature and has low detection accuracy. Therefore, it is urgent to develop a new battery self-discharge detection method to improve accuracy and shorten detection time.

[0003] Most existing technologies apply a small current signal to the battery and monitor the battery voltage change at the same time. When the battery potential stabilizes and does not change, the current value at this time is considered to be the self-discharge current. This method is significantly affected by the external environment and is prone to large test errors. Summary of the invention

[0004] In view of the above problems existing in the background technology, the present invention provides a battery self-discharge detection method based on reverse dynamic current excitation, which is used to shorten the self-discharge current test time and improve the test accuracy. The method obtains the self-discharge current through step current and relaxation voltage test, and corrects the ambient temperature noise based on the sensor data. It has the characteristics of wide application range, test time period and good detection accuracy.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A battery self-discharge detection method based on reverse dynamic current excitation comprises the following steps:

[0007] Step 1: Determine battery self-discharge

[0008] (1) Take the battery to be tested after being charged and put aside, test the current voltage value and compare it with the battery voltage before being put aside;

[0009] (2) When the voltage drops and the drop is ≥0.05V, the self-discharge estimation method is used to preliminarily determine that the battery has self-discharged. Otherwise, there is no need to perform the next test;

[0010] (3) For batteries that self-discharge, read the current voltage value and estimate the self-discharge current value x based on the theoretical formula;

[0011] Step 2: Build a battery self-discharge detection device

[0012] (1) Connecting the battery that has self-discharged in step 1 to a temperature sensor and fixing it on a battery charge and discharge test mold;

[0013] (2) Setting the temperature of the thermostat box to a fixed value between 25 and 30° C., and after the box temperature stabilizes, transferring the battery and its mold from step 2 (1) into the box, and sealing the box for standby use;

[0014] Step 3: Battery self-discharge detection process setting and testing

[0015] (1) Record the battery voltage at the beginning of the test as value y, and set the constant current charging step according to the self-discharge current x estimated in step 1 (3), wherein: the current is set to 10 to 100 times x, the constant current charging time is set to 10 to 20 seconds, the data acquisition time is set to 10 to 30 seconds, the temperature sensor is kept turned on synchronously with the constant current charging, and the temperature acquisition frequency is the same as the acquisition frequency of the charge and discharge tester, which is 0.03 to 0.10 Hz;

[0016] (2) After constant current charging is completed, the test is stopped and the rest time is recorded. The temperature sensor is kept turned on synchronously and the temperature detection result is output at the same time.

[0017] (3) Since the voltage change caused by the self-discharge current is small, in order to reduce the voltage measurement error caused by temperature fluctuations, the temperature output results obtained in step 3 (1) and step 3 (2) are corrected for temperature on the test voltage value according to the data correction equation, and the time acquisition result is further corrected;

[0018] Step 4: Output the battery self-discharge current result

[0019] (1) Collect the constant current charging current value I1 in step 3 (1), the charging start time t and the corrected end time t1, and calculate the charging capacity obtained by short-time dynamic current excitation according to the formula Q=I1*(t1-t);

[0020] (2) Collect the corrected end time t2 of the idle time in step 3 (2), and calculate the self-discharge current I2 that consumes the dynamic excitation capacity during the idle time according to the charge conservation formula I1*(t1-t)=I2*(t2-t1).

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. The present invention proposes for the first time a new battery testing method that can quickly detect the self-discharge current, which greatly shortens the detection time compared to the traditional K value detection method.

[0023] 2. The present invention utilizes short-term dynamic current excitation to quickly input a small amount of capacity, and realizes accurate detection of self-discharge through voltage balance, which effectively solves the problems of difficulty in finding self-discharge current and long test time in traditional detection methods.

[0024] 3. The present invention is based on the charge conservation principle and the Nernst equation, and combines the Nernst equation with temperature sensing, which can greatly shorten the test time, reduce the interference of the external environment on the test results, effectively alleviate the problem that the traditional method is greatly affected by the ambient temperature, and further improve the test accuracy.

[0025] 4. The present invention is a non-destructive testing method that does not require destruction of the battery structure and can be used for rapid batch screening of the health status of large-scale storage batteries.

[0026] 5. The overall testing process of the present invention is simple and easy to operate, and can be applied to the research of various battery systems, providing a new detection method for the next generation of battery development and battery operation and maintenance management. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the reverse dynamic current excitation test principle;

[0028] Figure 2 is a diagram of the experimental test device;

[0029] Figure 3 This is the measured battery voltage and temperature curve

[0030] Figure 4 This is a comparison chart of data correction based on temperature sensing;

[0031] Figure 5 This is a self-discharge current detection effect verification diagram. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below in conjunction with the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0033] The present invention provides a battery self-discharge detection method based on reverse dynamic current excitation, which is used for rapid batch detection of the self-discharge current of storage batteries or fresh batteries. The main principle of this method is the charge conservation formula. Through a short-term reverse excitation current, a small amount of capacity is quickly charged without affecting the safety status of the battery, and then the self-discharge current is used to clear it, thereby achieving accurate calculation of the self-discharge current. The present invention does not require long-term current and voltage testing, and at the same time, combined with the temperature correction scheme of the Nernst equation, it avoids the decrease in measurement accuracy caused by environmental changes, and provides an effective solution for further clarifying the health status information inside the battery and assisting the development of the next generation of batteries. The specific principle is as follows Figure 1 As shown, the specific implementation steps are as follows:

[0034] Step 1: Determine battery self-discharge

[0035] (1) Take the battery to be tested after being charged and set aside, test the current voltage value and compare it with the battery voltage before being set aside, wherein: the size and type of the battery to be tested is one of cylindrical battery 18650, cylindrical battery 21700, cylindrical battery 4680, soft pack battery, square battery, button battery; the battery system of the battery to be tested is one of lithium ion battery, sodium ion battery, lithium metal battery, sodium metal battery, lead-acid battery;

[0036] (2) When the voltage drops and the drop is ≥0.05V, the self-discharge estimation method is used to preliminarily determine that the battery has self-discharged. Otherwise, no further test is required, wherein the self-discharge estimation method includes one or more of a theoretical calculation method based on voltage difference and shelf time, a direct reading method of theoretical self-discharge current, a short-time constant potential method, and a short-time constant current method;

[0037] (3) For batteries that self-discharge, read the current voltage value and estimate the self-discharge current value x based on the theoretical formula;

[0038] Step 2: Build a battery self-discharge detection device

[0039] (1) connecting the battery detected in step 1 to have self-discharge behavior to a temperature sensor and fixing them on a battery charge and discharge test mold, wherein: the connection between the battery and the temperature sensor is one of an external bonding connection and an internal implantation connection, and the temperature sensor is one of a thermistor type, a thermocouple type, a resistor type, and an IC type;

[0040] (2) Setting the temperature of the thermostat box to a fixed value between 25 and 30° C., and after the box temperature stabilizes, transferring the battery and its mold from step 2 (1) into the box, and sealing the box for standby use;

[0041] Step 3: Battery self-discharge detection process setting and testing

[0042] (1) Record the battery voltage at the beginning of the test as value y, and set the constant current charging step according to the self-discharge current x estimated in step 1 (3), wherein: the current is set to 10 to 100 times x, the constant current charging time is set to 10 to 20 seconds, the data acquisition time is set to 10 to 30 seconds, the temperature sensor is kept turned on synchronously with the constant current charging, and the temperature acquisition frequency is the same as the acquisition frequency of the charge and discharge tester, which is 0.03 to 0.10 Hz;

[0043] (2) After constant current charging is completed, the test is stopped and the rest time is recorded. The temperature sensor is kept turned on synchronously and the temperature detection result is output at the same time.

[0044] (3) Since the voltage change caused by the self-discharge current is small, in order to reduce the voltage measurement error caused by temperature fluctuation, the temperature output results obtained in step 3 (1) and step 3 (2) are corrected for the test voltage value according to the data correction equation, and the time acquisition result is further corrected, wherein: the data correction equation is one of the Nernst equation and the Arrhenius equation;

[0045] Step 4: Output the battery self-discharge current result

[0046] (1) Collect the constant current charging current value I1 in step 3 (1), the charging start time t and the corrected end time t1, and calculate the charging capacity obtained by short-time dynamic current excitation according to the formula Q=I1*(t1-t);

[0047] (2) Collect the corrected end time t2 of the idle time in step 3 (2), and calculate the self-discharge current I2 that consumes the dynamic excitation capacity during the idle time according to the charge conservation formula I1*(t1-t)=I2*(t2-t1).

[0048] Example:

[0049] (1) Battery self-discharge determination and theoretical value estimation: Take a commercial 18650 ternary lithium-ion battery that is charged to 4.3V and left for 48 hours. After removing the charging polarization, its voltage is 4.03V before leaving. After testing the battery voltage, its voltage value is 3.97V. The difference between the two batteries is calculated to be 0.06V, which is greater than the set 0.05V determination standard. It is determined that the battery has self-discharged during the shelf time. The experiment uses a 18650 lithium-ion battery with ternary 811 material as the positive electrode material and graphite as the negative electrode. The theoretical capacity is 1500mAh. The query shows that its theoretical self-discharge range is 1 / 5000C to 1 / 50000C. The minimum value is taken as the theoretical self-discharge value x.

[0050] (2) Construction of the test end of the battery self-discharge detection device: Assemble the above-mentioned battery in Figure 2 On the battery mold shown, adjust the length of the fixture to 20cm, clamp the two sides of the battery with conductive copper columns, and the bottom of the mold is insulating plastic. Connect the two ends of the mold to the charge and discharge test device with wires. Test the open circuit voltage, determine that the circuit connection is normal without short circuit or false connection problems, and then connect the temperature sensor based on thermistor. The thermistor end of the sensor is bonded to the battery housing with krafton tape. The position is selected in the middle of the battery, and the other end is connected to the computer USB communication port. Turn on the temperature sensing test, and complete the connection of the test end device after the temperature transmission is correct.

[0051] (3) Setting up the environment of the battery self-discharge detection device: Set the temperature of the incubator to 25°C, place the above-mentioned battery test end mold, temperature sensor and its connecting lines stably inside the box, close the box, seal the wiring port with a rubber plug, and then turn on the temperature sensor and box temperature monitor. Observe the values ​​of both at the same time. When both values ​​reach 25°C and the temperature fluctuation is stable within the range of ±0.1°C, turn off the temperature sensor and prepare for testing.

[0052] (4) Battery self-discharge detection process setting and test flow: Turn on the battery charge and discharge test device, test the open circuit voltage, and obtain a test result of 3.96V. After recording its value as y, turn on the charging module and charge the battery with a constant current. The charging current is set to 100 times the theoretical self-discharge current value x, that is, 1 / 500C. Combined with the theoretical capacity of the battery, the current value is set to 3mA and recorded as I1. At the same time, the constant current charging time is set to 20s, and the start time of the constant current charge battery is recorded as t=65s. The voltage and current data acquisition time interval is set to 10s. The constant current module is turned on synchronously with the temperature sensor module. The temperature sampling time is kept the same as the voltage sampling time, and the sampling frequency is set to 0.1Hz.

[0053] (5) Battery self-discharge test data collection process: After the constant current charging step is completed, record the charging end time t1 = 85s and transfer the test battery to the shelf process, start recording the battery voltage change, set the voltage data collection time interval to 10s, and keep the temperature sensor turned on at 0.1Hz to ensure the synchronous output of temperature data and voltage data. The test ends when the battery voltage drops back to ≤3.96V. Output the voltage curve and the temperature change curve for backup. The results are as follows Figure 3 shown.

[0054] (6) Battery self-discharge test data correction: The temperature output and shelf voltage output results obtained in (5) are corrected according to the Nernst equation E = E(standard) - (RT) / (nF) ln (([C] c ·[D] d ) / ([A]a [B] b ) to correct the test voltage value, the result is as follows Figure 4 According to the corrected battery voltage curve, the time value corresponding to when the voltage drops back to 3.96V is accurately determined and recorded as t2 = 1195s.

[0055] (7) Output of battery self-discharge current result: According to the constant current charging current value I1 in step (4), the charging time start time t and the corrected end time t1, according to the formula Q = I1*(t1-t), the charging capacity Q = 0.0167mAh obtained by short-time dynamic current excitation is calculated. According to the corrected standby end time t2 in step (6), according to the charge conservation formula I1*(t1-t) = I2*(t2-t1), the self-discharge current I2 = 1 / 27750C that consumes the dynamic excitation capacity during the standby time is calculated.

[0056] (8) Verification of battery self-discharge test results: The above battery is set to a constant current charging step, with the current magnitude equal to the self-discharge current value I2 detected in step (7), and the battery voltage change is detected. The output voltage curve is continuously recorded for 50,000 seconds. Figure 5 As shown, it is found that the voltage is maintained in a stable range and does not drop, verifying that the effect is good.

Claims

1. A battery self-discharge detection method based on reverse dynamic current excitation, characterized in that The method comprises the following steps: Step 1: Determine battery self-discharge (1) Take the battery to be tested after being charged and put aside, test the current voltage value and compare it with the battery voltage before being put aside; (2) When the voltage drops and the drop is ≥0.05V, the self-discharge estimation method is used to preliminarily determine that the battery has self-discharged. Otherwise, there is no need to perform the next test; (3) For batteries that self-discharge, read the current voltage value and estimate the self-discharge current value x based on the theoretical formula; Step 2: Build a battery self-discharge detection device (1) Connecting the battery that has self-discharged in step 1 to a temperature sensor and fixing it on a battery charge and discharge test mold; (2) Setting the temperature of the thermostat box to a fixed value between 25 and 30° C., and after the box temperature stabilizes, transferring the battery and its mold from step 2 (1) into the box, and sealing the box for standby use; Step 3: Battery self-discharge detection process setting and testing (1) Record the battery voltage at the beginning of the test as value y, and set the constant current charging step according to the self-discharge current x estimated in step 1 (3); (2) After constant current charging is completed, the test is turned on and the battery voltage is monitored. When the battery voltage drops back to the voltage y value at the beginning of the test, the test is stopped and the standby time is recorded. The temperature sensor is kept turned on and the temperature detection result is output at the same time. (3) Since the voltage change caused by the self-discharge current is small, in order to reduce the voltage measurement error caused by temperature fluctuations, the temperature output results obtained in step 3 (1) and step 3 (2) are corrected for temperature by the test voltage value according to the data correction equation, and the time acquisition result is further corrected; Step 4: Output the battery self-discharge current result (1) Collect the constant current charging current value I1 in step 3 (1), the charging start time t and the corrected end time t1, and calculate the charging capacity obtained by short-time dynamic current excitation according to the formula Q=I1*(t1-t); (2) Collect the corrected end time t2 of the idle time in step 3 (2), and calculate the self-discharge current I2 that consumes the dynamic excitation capacity during the idle time according to the charge conservation formula I1*(t1-t)=I2*(t2-t1).

2. The battery self-discharge detection method based on reverse dynamic current excitation according to claim 1 is characterized in that The type of the battery to be tested is one of a cylindrical battery, a soft-pack battery, a square battery, and a button battery.

3. The battery self-discharge detection method based on reverse dynamic current excitation according to claim 1 or 2, characterized in that The battery system of the battery to be tested is one of a lithium ion battery, a sodium ion battery, a lithium metal battery, a sodium metal battery, and a lead-acid battery.

4. The battery self-discharge detection method based on reverse dynamic current excitation according to claim 1 is characterized in that The self-discharge estimation method includes one or more of a theoretical calculation method based on voltage difference and shelf time, a theoretical self-discharge current direct reading method, a short-time constant potential method, and a short-time constant current method.

5. The battery self-discharge detection method based on reverse dynamic current excitation according to claim 1 is characterized in that The battery and the temperature sensor are connected in one of an external bonding connection and an internal implantation connection.

6. The battery self-discharge detection method based on reverse dynamic current excitation according to claim 1 or 5, characterized in that The temperature sensor is one of thermistor type, thermocouple type, resistor type and IC type.

7. The battery self-discharge detection method based on reverse dynamic current excitation according to claim 1 is characterized in that In the constant current charging step, the current is set to 10 to 100 times x, the constant current charging time is set to 10 to 20 seconds, the data acquisition time is set to 10 to 30 seconds, the temperature sensor is kept turned on synchronously with the constant current charging, and the temperature acquisition frequency is the same as the acquisition frequency of the charge and discharge tester.

8. The battery self-discharge detection method based on reverse dynamic current excitation according to claim 7 is characterized in that The temperature acquisition frequency and the charge and discharge tester acquisition frequency are 0.03-0.10 Hz.

9. The battery self-discharge detection method based on reverse dynamic current excitation according to claim 1 is characterized in that The data correction equation is one of the Nernst equation and the Arrhenius equation.

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