A multi-parameter early warning method and device for overcharge and thermal runaway of lithium battery packs

Abstract

The present invention provides a multi-parameter early warning method for overcharge thermal runaway of a lithium battery pack, comprising the following steps: S1: collecting characteristic parameter values ​​of voltage E, temperature T, and pressure P at intervals of X seconds to determine whether E is within the normal operating range; if not, proceeding to step 2, and if so, repeating step 1; S2: calling a voltage, temperature, and pressure processing subroutine to collect E, T, and P, and using the coordinate data of T and P to perform a K-means clustering algorithm to determine which overcharge stage the battery is in; S3: calling a voltage, temperature, and pressure processing subroutine to determine whether the rate of change of E, T, and P is within the overcharge stage threshold determined by the K-means clustering algorithm, and performing a secondary judgment of the overcharge stage; when the secondary judgment is consistent with the clustering algorithm judgment, a warning alarm is issued and displayed on a display terminal; when the secondary judgment is inconsistent with the clustering algorithm judgment, the secondary judgment shall prevail. The present invention also provides an early warning device using the above method.

Description

Technical Field

[0001] The present invention relates to the technical field of battery safety detection, and in particular to a multi-parameter early warning method and device for overcharge and thermal runaway of a lithium battery pack. Background Art

[0002] With the country's dual carbon goals and strategic direction for energy structure transformation, the new energy industry has gradually become a key area of ​​future development. Against this backdrop, lithium-ion batteries, as one of the most efficient energy storage methods, have received strong policy support. Lithium-ion batteries are widely used in energy storage power stations, new energy vehicles, aerospace, and other fields, providing strong support for the adjustment and transformation of the country's energy structure. However, with the widespread use of lithium-ion batteries, the incidence of fire safety accidents has increased year by year, with overcharging becoming a major cause of thermal runaway in lithium batteries.

[0003] At this point, the lithium battery's voltage exceeds its rated voltage, leading to overheating and runaway chemical reactions, potentially posing serious risks such as fire and explosion. Therefore, it's crucial for lithium battery manufacturers and users to be able to warn of overcharge and prevent it. To prevent this safety issue, lithium batteries require effective monitoring and early warning systems. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a multi-parameter early warning method and device for overcharge thermal runaway of a lithium battery pack, which can judge whether the lithium battery is overcharged and the overcharge stage and provide an early warning.

[0005] In order to solve the above technical problems, the present invention provides a multi-parameter early warning method for overcharge thermal runaway of a lithium battery pack, comprising the following steps:

[0006] S1: Collect characteristic parameter values ​​of voltage E, temperature T, and pressure P at intervals of X seconds to determine whether voltage E is within the normal operating range; if not, proceed to step 2; if so, repeat step 1;

[0007] S2: Call the voltage processing subroutine, temperature processing subroutine, and pressure processing subroutine to collect voltage E, temperature T, and pressure P, and use the coordinate data of temperature T and pressure P to perform K-means clustering algorithm to determine whether the battery is in a slightly overcharged, moderately overcharged, or severely overcharged stage;

[0008] S3: Call the voltage processing subroutine, temperature processing subroutine, and pressure processing subroutine to determine whether the change rate of voltage E, temperature T, and pressure P is within the overcharge stage threshold determined by the K-means clustering algorithm, and perform a secondary judgment on the overcharge stage; when the secondary judgment is consistent with the clustering algorithm judgment, a warning alarm is issued and the display terminal is displayed; when the secondary judgment is inconsistent with the clustering algorithm judgment, it is sent to a lighter stage for comparison until the secondary judgment result falls within the threshold range of the correct overcharge stage, and a display terminal is displayed and a warning alarm is issued.

[0009] In some embodiments, the specific method of the secondary judgment in S3 is:

[0010] 1) When the change rates of two or more of the voltage E, temperature T, and pressure P are within the slight overcharge threshold range, it is determined to be in the slight overcharge stage. Otherwise, the subroutine is returned to continue calling the clustering algorithm for judgment;

[0011] 2) If the clustering algorithm determines that the vehicle is in the moderate overcharge stage, and the change rates of two or more of the voltage E, temperature T, and pressure P are within the moderate overcharge stage threshold, the vehicle is determined to be in the moderate overcharge stage. Otherwise, the vehicle is sent to the slight overcharge stage for judgment.

[0012] 3) When the clustering algorithm determines that the vehicle is in the severe overcharge stage, and the change rates of two or more of the voltage E, temperature T, and pressure P are within the severe overcharge stage threshold, the vehicle is determined to be in the severe overcharge stage. Otherwise, the vehicle is sent to the moderate overcharge stage for judgment.

[0013] In some embodiments, the specific data processing flow of the voltage processing subroutine is as follows:

[0014] 1) Enable the voltage AD acquisition program, assign E1 to the voltage value at the start of the experiment, assign E2 to the voltage at NS, and assign E3 to the voltage at 2NS;

[0015] 2) Calculate the voltage change rate V 12 =(E2-E1) / N, V 23 =(E3-E2) / N, determine whether V 12 >V 23 If the value is satisfied, the corresponding time t1 and t2 of E2 and E3 are output. If not, the value of E2 is assigned to E1 and the value of E3 is assigned to E2. The voltage at the moment after NS is continuously refreshed and assigned to E3. It is judged again whether V is satisfied. 12 >V 23 , reciprocating assignment outputs the corresponding times t1 and t2 of E2 and E3 that meet the above conditions;

[0016] 3) The value of t1 when the change rate decreases for the first time is assigned to a as the reference time point of the medium overcharge stage.

[0017] In some embodiments, the specific data processing flow of the temperature processing subroutine is as follows:

[0018] 1) Initialize the temperature T, and then perform clustering algorithm judgment based on the temperature and voltage coordinate data that changes every second;

[0019] 2) When the clustering algorithm determines that it is a slightly overcharged stage, T1 is assigned as the temperature value at the beginning of the experiment, and T m The temperature value at 100% SOC, T is assigned as the real-time temperature, T2 is assigned as the temperature value at NS; calculate the temperature difference TT at the current moment m , and calculate the temperature change rate V T =(T2-T1) / N; assign T1 to T2 value, assign T2 to N Temperature value after S, every N S refreshes the values ​​of T1 and T2 once and calculates the temperature change rate;

[0020] 3) When the clustering algorithm determines that it is a moderate overcharge stage, the temperature values ​​corresponding to t1, t2, and a are assigned to T1, T2, and T a , assign the real-time temperature to T, and calculate the current temperature difference to TT a , and calculate the temperature change rate VT = (T2-T1) / N; refresh t1 and t2 every NS to update T1 and T2, and continuously output the calculation results.

[0021] In some embodiments, the specific data processing flow of the pressure processing subroutine is as follows:

[0022] 1) Initialize the pressure P, and then perform clustering algorithm judgment based on the pressure and voltage coordinate data that changes every second;

[0023] 2) When the clustering algorithm determines that it is a slightly overcharged stage, assign P1 as the pressure value at the beginning of the experiment, and assign P m Assign P to the real-time pressure and P2 to the pressure value at NS; calculate the pressure difference PP at the current moment m , and calculate the pressure change rate V P =(P2-P1) / N; assign P1 to the value of P2, assign P2 to the pressure value at the moment after NS, refresh the values ​​of P1 and P2 every NS, and calculate the pressure change rate;

[0024] 3) When the clustering algorithm determines that it is a moderate overcharge stage, the pressure values ​​corresponding to the time t1, t2, and a are assigned to P1, P2, and P a , assign the real-time pressure to P, and calculate the current pressure difference to PP a, and calculate the pressure change rate V P =(P2-P1) / N; refresh t1 and t2 every NS to update P1 and P2, and continuously output the calculation results.

[0025] In some embodiments, the temperature T is collected by a thermocouple, and the pressure P is collected by a thin film pressure strain gauge.

[0026] In order to solve the above technical problems, the present invention also provides an early warning device that adopts the above-mentioned multi-parameter early warning method for overcharge and thermal runaway of a lithium battery pack, which is characterized in that it includes a detection terminal and a display terminal; the detection terminal includes an acquisition module, a signal processing circuit, a detection terminal MCU, and a detection terminal wireless communication module. The acquisition module is used to collect the voltage E, temperature T, and pressure P during the charging process of the lithium battery pack. The signal processing circuit is used to process the signal collected by the acquisition module and input it into the detection terminal MCU. The detection terminal MCU is used to perform data processing of the subroutine, and the data processing result is transmitted to the display terminal through the detection terminal wireless communication module for display.

[0027] In some embodiments, the display terminal includes a display terminal wireless communication module, a display terminal MCU, and a display screen; the display terminal wireless communication module receives the signal from the detection terminal wireless communication module and inputs it into the main program of the display terminal MCU for judgment and digital-to-analog conversion, and the converted signal of the display terminal MCU is transmitted to the display screen for display.

[0028] In some embodiments, the display terminal further includes a buzzer for early warning of overcharging.

[0029] In some embodiments, the detection terminal further includes an RTC clock circuit, and the RTC clock circuit and the detection terminal MCU exchange signals; the display terminal further includes an RTC clock circuit, and the RTC clock circuit and the display terminal MCU exchange signals.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention collects voltage, temperature, and pressure data to perform a clustering algorithm to determine the overcharge stage, and calls a subroutine to calculate the voltage, temperature, and pressure change rate for secondary judgment of the overcharge stage. This method can effectively utilize multiple parameters to more accurately determine whether a lithium battery is overcharged and the overcharge stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is an overall design diagram of the lithium battery pack overcharge thermal runaway warning device of Example 1;

[0032] Figure 2 This is a flow chart of the voltage subroutine data processing in Example 1;

[0033] Figure 3 This is a flow chart of the temperature subroutine data processing in Example 1;

[0034] Figure 4 This is a flow chart of the pressure subroutine data processing in Example 1;

[0035] Figure 5 This is a flowchart of the algorithm of the multi-parameter early warning method of Example 1;

[0036] Figure 6 This is the voltage, temperature and expansion force change curve of lithium battery overcharge test;

[0037] Figure 7 This is the temperature change rate curve of the lithium battery overcharge experiment;

[0038] Figure 8 This is the pressure change rate curve of the lithium battery overcharge experiment. DETAILED DESCRIPTION

[0039] In order to make the purpose and technical solution of the present invention clearer, the specific embodiments of the present invention are further described below with reference to the accompanying drawings.

[0040] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, rather than all embodiments. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be understood as limiting the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0041] Overcharging is one of the most common safety issues with lithium batteries. Overcharging can lead to thermal runaway and explosion. To prevent this, early warning of overheating and runaway of lithium battery packs is necessary.

[0042] Therefore, this embodiment provides a multi-parameter early warning method for lithium battery overcharge thermal runaway, including the following steps:

[0043] S1: Collect characteristic parameter values ​​of voltage E, temperature T, and pressure P every 1 second to determine whether voltage E is within the normal working range;

[0044] S2: When the display terminal shows that the voltage E exceeds the normal operating range, the voltage processing subroutine, temperature processing subroutine, and pressure processing subroutine are called to collect the voltage E, temperature T, and pressure P. The coordinate data of temperature T and pressure P are used to perform a K-means clustering algorithm to determine whether the battery is in a slightly overcharged, moderately overcharged, or severely overcharged stage;

[0045] S3: Call the voltage processing subroutine, temperature processing subroutine, and pressure processing subroutine to determine whether the change rate of voltage E, temperature T, and pressure P is within the overcharge stage threshold determined by the K-means clustering algorithm, and perform a secondary judgment on the overcharge stage; when the secondary judgment is consistent with the clustering algorithm judgment, a warning alarm is issued and the display terminal is displayed; when the secondary judgment is inconsistent with the clustering algorithm judgment, it is sent to a lighter stage for comparison until the secondary judgment result falls within the threshold range of the correct overcharge stage, and a display terminal is displayed and a warning alarm is issued.

[0046] The specific method of the secondary judgment of S3 is:

[0047] 1) When the change rates of two or more of the voltage E, temperature T, and pressure P are within the slight overcharge threshold range, it is determined to be in the slight overcharge stage. Otherwise, the subroutine is returned to continue calling the clustering algorithm for judgment;

[0048] 2) If the clustering algorithm determines that the vehicle is in the moderate overcharge stage, and the change rates of two or more of the voltage E, temperature T, and pressure P are within the moderate overcharge stage threshold, the vehicle is determined to be in the moderate overcharge stage. Otherwise, the vehicle is sent to the slight overcharge stage for judgment.

[0049] 3) When the clustering algorithm determines that the vehicle is in the severe overcharge stage, and the change rates of two or more of the voltage E, temperature T, and pressure P are within the severe overcharge stage threshold, the vehicle is determined to be in the severe overcharge stage. Otherwise, the vehicle is sent to the moderate overcharge stage for judgment.

[0050] The specific judgment methods for the mild overcharge stage, moderate overcharge stage, and severe overcharge stage, as well as the secondary judgment methods for determining whether each rate of change parameter meets the requirements of each overcharge stage, are as follows:

[0051] Take the overcharge test of ternary lithium battery with 80% SOC and 1C charge rate at 20℃ as an example. Figure 6As shown in the figure, in the early stages of lithium-ion battery overcharge, a significant voltage rise is observed, while changes in temperature and expansion force are relatively slow. This phenomenon results from the complex interplay of physical and chemical processes within the battery. Subsequently, the battery temperature begins to rise sharply. At point B, the battery temperature and voltage continue to rise, while the battery expansion force begins to decrease. After reaching point C, the battery temperature and expansion force suddenly change, showing an upward trend, while the voltage decreases and then continues to rise. The experiment was divided into three phases based on the characteristics of the battery state and pressure changes. The first phase (mild overcharge phase) is defined from the time the pressure curve begins to decrease until the pressure curve begins to increase and the voltage begins to decrease. The third phase (severe overcharge phase) is defined from the time the pressure curve begins to increase and the voltage begins to decrease. At this point, the lithium battery has already cracked.

[0052] like Figure 7 As shown, data extraction was performed on the temperature rise rate of three groups of experiments with lithium batteries having an initial SOC of 80%. It can be found that the temperature rise rate increases with the increase of the overcharge rate. The highest temperature rise rate was in the experiment with an initial charge of 80% SOC and an overcharge rate of 1.5C, and the lowest temperature rise rate was in the experiment with an initial charge of 80% SOC and an overcharge rate of 0.5C. The temperature rise rates of the three groups of experiments were all greater than or equal to 0.4℃ / min after entering the medium overcharge stage. Therefore, the temperature rise rate greater than or equal to 0.4℃ / min is used as the criterion for the ternary lithium battery to enter the medium stage of overcharge. At the same time, through the temperature difference data, the following can be observed: in the slight overcharge stage, the temperature difference is usually less than 5℃; in the data of the medium overcharge stage, the temperature difference exceeds 5℃. The temperature difference of 5℃ is used as the dividing line between the slight overcharge stage and the medium overcharge stage.

[0053] like Figure 8 As shown in the figure, during the moderate overcharge stage, the experimental pressure change rate is generally within the range of 1.0 to 2.0 N / min. Therefore, this range is used as the criterion for the moderate overcharge stage. The overcharge stage is determined based on the combination of multiple parameters. Furthermore, analysis of the experimental data reveals a clear dividing line between the pressure difference in the moderate overcharge stage and the pressure values ​​in the other two stages. The pressure difference at this dividing line is -3 N. This dividing line is used as the boundary between the mild overcharge stage and the moderate overcharge stage.

[0054] Furthermore, the specific data processing flow of the voltage processing subroutine is as follows:

[0055] 1) Enable the voltage AD acquisition program, assign E1 to the voltage value at the start of the experiment, assign E2 to the voltage at 60 seconds, and assign E3 to the voltage at 120 seconds;

[0056] 2) Calculate the voltage change rate V 12 =(E2-E1) / 60, V 23 =(E3-E2) / 60, determine whether V 12 >V 23 If the value is satisfied, the corresponding time t1 and t2 of E2 and E3 are output. If the value is not satisfied, the value of E2 is assigned to E1 and the value of E3 is assigned to E2. The voltage after 60S is continuously refreshed and assigned to E3. It is judged again whether V 12 >V 23 , reciprocating assignment outputs the corresponding times t1 and t2 of E2 and E3 that meet the above conditions;

[0057] 3) The value of t1 when the voltage change rate first decreases is assigned to a as the reference time point of the moderate overcharge stage.

[0058] The specific data processing flow of the temperature processing subroutine is as follows:

[0059] 1) Initialize the temperature T, and then perform clustering algorithm judgment based on the temperature and voltage coordinate data that changes every second;

[0060] 2) When the clustering algorithm determines that it is a slightly overcharged stage, T1 is assigned as the temperature value at the beginning of the experiment, and T m The temperature value at 100% SOC, T is the real-time temperature, T2 is the temperature value 60 seconds after the start of the experiment; calculate the temperature difference TT at the current moment m , and calculate the temperature change rate V T =(T2-T1) / 60; assign T1 to the value of T2, assign T2 to the temperature value 160 seconds after the current T (that is, 120 seconds after the start of the experiment), refresh the values ​​of T1 and T2 every 60 seconds, and calculate the temperature change rate;

[0061] 3) When the clustering algorithm determines that it is a moderate overcharge stage, the temperature values ​​corresponding to t1, t2, and a are assigned to T1, T2, and T a , assign the real-time temperature to T, and calculate the current temperature difference to TT a , and calculate the temperature change rate V T =(T2-T1) / 60; refresh t1 and t2 every 60 seconds to update T1 and T2, and continuously output the calculation results.

[0062] The specific data processing flow of the pressure processing subroutine is as follows:

[0063] 1) Initialize the pressure P, and then perform clustering algorithm judgment based on the pressure and voltage coordinate data that changes every second;

[0064] 2) When the clustering algorithm determines that it is a slightly overcharged stage, assign P1 as the pressure value at the beginning of the experiment, and assign P m The pressure value at 100% SOC, P is assigned as the real-time pressure, and P2 is assigned as the pressure value 60S after the start of the experiment; calculate the current pressure difference PP m , and calculate the pressure change rate V P =(P2-P1) / 60; assign P1 to the value of P2, assign P2 to the pressure value 60 seconds after the current P1 (that is, 120 seconds after the start of the experiment), refresh the values ​​of P1 and P2 every 60 seconds, and calculate the pressure change rate;

[0065] 3) When the clustering algorithm determines that it is a moderate overcharge stage, the pressure values ​​corresponding to t1, t2, and a are assigned to P1, P2, and P a , assign the real-time pressure to P, and calculate the current pressure difference to PP a , and calculate the pressure change rate V P =(P2-P1) / 60; refresh t1 and t2 every 60 seconds to update P1 and P2, and continuously output the calculation results.

[0066] The early warning method of this embodiment is applied to a multi-parameter early warning device for overcharge thermal runaway of a lithium battery pack. The early warning device includes a detection terminal and a display terminal. The detection terminal includes an acquisition module, a signal processing circuit, a detection terminal MCU, and a detection terminal wireless communication module. The acquisition module is used to collect the voltage E, temperature T, and pressure P of the lithium battery pack during charging. The acquisition module uses a thin film pressure strain gauge, four K-type thermocouples, and a module for collecting battery voltage to complete the collection of lithium battery pressure P, temperature T, and voltage E data. After being processed by the signal processing circuit, the data is input into the detection terminal MCU for data processing in a subroutine. The data processing results are transmitted to the display terminal via the detection terminal wireless communication module for display.

[0067] The display terminal includes a display terminal wireless communication module, a display terminal MCU, and a display screen; the display terminal wireless communication module receives the signal from the detection terminal wireless communication module and inputs it to the display terminal MCU for main program judgment and digital-to-analog conversion. The signal converted by the MCU is transmitted to the display screen for display. The display terminal also includes a buzzer to warn of overcharging.

[0068] In order to ensure that the detection terminal data can be sent to the display terminal on time, the detection terminal also introduces an RTC clock circuit, and the RTC clock circuit and the detection terminal MCU signals are transmitted to each other; the display terminal also introduces an RTC clock circuit, and the RTC clock circuit and the display terminal MCU signals are transmitted to each other.

[0069] The embodiments described herein are intended only to help understand the method and core concept of the present invention. Furthermore, those skilled in the art will appreciate that variations in the specific embodiments and scope of application are possible based on the principles of the present invention. In summary, this specification should not be construed as limiting the present invention.

Claims

1. A multi-parameter early warning method for overcharge thermal runaway of a lithium battery pack, characterized in that: The following steps are involved: S1: Collect characteristic parameter values ​​of voltage E, temperature T, and pressure P at intervals of X seconds to determine whether voltage E is within the normal operating range; if not, proceed to step 2; if so, repeat step 1; S2: Call the voltage processing subroutine, temperature processing subroutine, and pressure processing subroutine to collect voltage E, temperature T, and pressure P, and use the coordinate data of temperature T and pressure P to perform K-means clustering algorithm to determine whether the battery is in a slightly overcharged, moderately overcharged, or severely overcharged stage; S3: Call the voltage processing subroutine, temperature processing subroutine, and pressure processing subroutine to determine whether the change rate of voltage E, temperature T, and pressure P is within the overcharge stage threshold determined by the K-means clustering algorithm, and perform a secondary judgment on the overcharge stage; when the secondary judgment is consistent with the clustering algorithm judgment, a warning alarm is issued and the display terminal is displayed; when the secondary judgment is inconsistent with the clustering algorithm judgment, it is sent to a lighter stage for comparison until the secondary judgment result falls within the threshold range of the correct overcharge stage, and a display terminal is displayed and a warning alarm is issued.

2. The multi-parameter early warning method for overcharge thermal runaway of a lithium battery pack according to claim 1, characterized in that: The specific method of the secondary judgment of S3 is: 1) When the change rates of two or more of the voltage E, temperature T, and pressure P are within the slight overcharge threshold range, it is determined to be in the slight overcharge stage. Otherwise, the subroutine is returned to continue calling the clustering algorithm for judgment; 2) If the clustering algorithm determines that the vehicle is in the moderate overcharge stage, and the change rates of two or more of the voltage E, temperature T, and pressure P are within the moderate overcharge stage threshold, the vehicle is determined to be in the moderate overcharge stage. Otherwise, the vehicle is sent to the slight overcharge stage for judgment. 3) When the clustering algorithm determines that the vehicle is in the severe overcharge stage, and the change rates of two or more of the voltage E, temperature T, and pressure P are within the severe overcharge stage threshold, the vehicle is determined to be in the severe overcharge stage. Otherwise, the vehicle is sent to the moderate overcharge stage for judgment.

3. The multi-parameter early warning method for overcharge thermal runaway of a lithium battery pack according to claim 1, characterized in that: The specific data processing flow of the voltage processing subroutine is as follows: 1) Enable the voltage AD acquisition program, assign E1 to the voltage value at the start of the experiment, assign E2 to the voltage at NS, and assign E3 to the voltage at 2NS; 2) Calculate the voltage change rate V 12 =(E2-E1) / N, V 23 =(E3-E2) / N, determine whether V 12 >V 23 If the value is satisfied, the corresponding time t1 and t2 of E2 and E3 are output. If not, the value of E2 is assigned to E1 and the value of E3 is assigned to E2. The voltage at the moment after NS is continuously refreshed and assigned to E3. It is judged again whether V is satisfied. 12 >V 23 , reciprocatingly assigning outputs to the corresponding times t1 and t2 of E2 and E3 that meet the above conditions; 3) The value of t1 when the change rate decreases for the first time is assigned to a as the reference time point of the medium overcharge stage.

4. The multi-parameter early warning method for overcharge thermal runaway of a lithium battery pack according to claim 3, characterized in that: The specific data processing flow of the temperature processing subroutine is as follows: 1) Initialize the temperature T, and then perform clustering algorithm judgment based on the temperature and voltage coordinate data that changes every second; 2) When the clustering algorithm determines that it is a slightly overcharged stage, T1 is assigned as the temperature value at the beginning of the experiment, and T m The temperature value at 100% SOC, T is assigned as the real-time temperature, T2 is assigned as the temperature value at NS; calculate the temperature difference TT at the current moment m , and calculate the temperature change rate V T =(T2-T1) / N; assign T1 to T2, assign T2 to the temperature value after NS, refresh the values ​​of T1 and T2 every NS, and calculate the temperature change rate; 3) When the clustering algorithm determines that it is a moderate overcharge stage, the temperature values ​​corresponding to t1, t2, and a are assigned to T1, T2, and T a , assign the real-time temperature to T, and calculate the current temperature difference to TT a , and calculate the temperature change rate V T =(T2-T1) / N; refresh t1 and t2 every NS to update T1 and T2, and continuously output the calculation results.

5. The multi-parameter early warning method for overcharge thermal runaway of a lithium battery pack according to claim 3, characterized in that: The specific data processing flow of the pressure processing subroutine is as follows: 1) Initialize the pressure P, and then perform clustering algorithm judgment based on the pressure and voltage coordinate data that changes every second; 2) When the clustering algorithm determines that it is a slightly overcharged stage, assign P1 as the pressure value at the beginning of the experiment, and assign P m Assign P to the real-time pressure and P2 to the pressure value at NS; calculate the pressure difference PP at the current moment m , and calculate the pressure change rate V P =(P2-P1) / N; assign P1 to the value of P2, assign P2 to the pressure value at the moment after NS, refresh the values ​​of P1 and P2 every NS, and calculate the pressure change rate; 3) When the clustering algorithm determines that it is a moderate overcharge stage, the pressure values ​​corresponding to t1, t2, and a are assigned to P1, P2, and P a , assign the real-time pressure to P, and calculate the current pressure difference to PP a , and calculate the pressure change rate V P =(P2-P1) / N; refresh t1 and t2 every NS to update P1 and P2, and continuously output the calculation results.

6. The multi-parameter early warning method for overcharge thermal runaway of a lithium battery pack according to claim 1, characterized in that: The temperature T is collected by a thermocouple, and the pressure P is collected by a thin film pressure strain gauge.

7. An early warning device using the multi-parameter early warning method for overcharge thermal runaway of a lithium battery pack according to any one of claims 1 to 6, characterized in that: It includes a detection terminal and a display terminal; the detection terminal includes an acquisition module, a signal processing circuit, a detection terminal MCU, and a detection terminal wireless communication module. The acquisition module is used to collect the voltage E, temperature T, and pressure P during the charging process of the lithium battery pack. The signal processing circuit is used to process the signal collected by the acquisition module and input it into the detection terminal. MCU, the detection terminal MCU is used to perform data processing of the subroutine, and the data processing results are transmitted to the display terminal through the detection terminal wireless communication module for display.

8. The multi-parameter early warning device for overcharge and thermal runaway of a lithium battery pack according to claim 7, characterized in that: The display terminal includes a display terminal wireless communication module, a display terminal MCU, and a display screen; the display terminal wireless communication module receives the signal from the detection terminal wireless communication module and inputs it into the main program of the display terminal MCU for judgment and digital-to-analog conversion, and the converted signal of the display terminal MCU is transmitted to the display screen for display.

9. The multi-parameter early warning device for overcharge and thermal runaway of a lithium battery pack according to claim 8, characterized in that: The display terminal also includes a buzzer for early warning and alarm during overcharging.

10. The multi-parameter early warning device for overcharge and thermal runaway of a lithium battery pack according to claim 8, characterized in that: The detection terminal further includes an RTC clock circuit, and the RTC clock circuit and the detection terminal MCU exchange signals; the display terminal further includes an RTC clock circuit, and the RTC clock circuit and the display terminal MCU exchange signals.

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