CN117949836B - Method, device, terminal and storage medium for identifying hidden danger of thermal runaway of battery - Google Patents
Method, device, terminal and storage medium for identifying hidden danger of thermal runaway of battery Download PDFInfo
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Abstract
The application discloses a method, a device, a terminal and a storage medium for identifying potential thermal runaway hazards of a battery, wherein a rigid mechanism is arranged on one side of the expansion direction of the battery, and a pressure sensor is arranged on one side of the rigid mechanism, which is not contacted with the battery; the method comprises the following steps: acquiring a pressure value of the pressure sensor, establishing an initial pressure reference, and recording the pressure value of the current pressure sensor as an initial pressure value F P0; judging whether the pressure sensor fails or not based on the measuring range of the pressure sensor and the initial pressure value F P0; if yes, a warning of failure of the pressure sensor is sent out, if not, a pressure value of the pressure sensor is obtained in real time based on the detection frequency f, and whether the battery explosion-proof valve is opened is identified based on the pressure value obtained in real time. The method, the device, the terminal and the storage medium applying the method improve the identification precision of potential thermal runaway hazards of the battery.
Description
Technical Field
The application relates to the technical field of battery safety control, in particular to a method, a device, a terminal and a storage medium for identifying potential hazards of thermal runaway of a battery.
Background
Currently, lithium batteries are widely applied to electric vehicles or energy storage systems, whether electric vehicles or energy storage applications, and the safety problem of the lithium batteries is always a discussed hot spot problem, and the prevention and identification of thermal runaway of the batteries are also important investigation factors in battery safety, although in the design of the battery core, investigation of potential thermal runaway hazards, such as insulation design, NP ratio design, explosion-proof valve design and the like of the battery core, are considered, and after parameterization, the qualified fresh battery core is safe; in addition, if these variables can be detected at any time during the system design and application, the safety of the battery cell is predictable and controllable to some extent throughout the life of the battery cell, and thermal runaway is not theoretically caused, causing explosion.
However, in practical situations, the safety design of the battery cell is almost encapsulated inside the battery cell, so that the battery cell is difficult to detect by an effective means; at present, a detection object with higher feasibility is an explosion-proof valve positioned on the surface of the battery cell; the explosion-proof valve, namely the safety valve, is the last barrier after the failure of the cell structure and before explosion, and whether the battery has a thermal runaway hidden trouble is judged by identifying the opening of the explosion-proof valve. Currently, regarding related designs for identifying whether a battery explosion-proof valve is opened, the following two directions are mainly used at present:
The method is to provide a basis for designing a battery pack or a battery pack by determining the opening air pressure value of the battery explosion-proof valve so as to prevent the battery from explosion. The principle is that the data related to the pressure bearing performance of the heat insulation component of the battery pack, such as the data of the stress area, the thickness parameter, the temperature parameter and the like of the component, are related to the compression rate of the heat insulation component, so as to determine the valve opening pressure value of the explosion-proof valve of the battery pack, and the core point of the method is that the pressure value inside a core needs to be acquired in the actual implementation process, and the method has the following defects:
(1) Strong specialization is required, and new potential safety hazards can be introduced when the operation is improper; the pressure value inside the battery core is required to be acquired, which is equivalent to that an air pressure sensor is implanted inside the battery core, the existing standard equipment cannot be realized, manual operation is required, once manual operation is improper, even only shaking hands, short circuit in the battery core can be possibly caused, and thermal runaway is caused, so that the requirement on the specialization of the operation method is extremely high;
(2) The energy density of the battery is reduced; the air pressure sensor needs to occupy the internal space of the battery cell, so that the space cannot participate in the electrochemical reaction of the battery in the charging and discharging process, and therefore, the charging and discharging energy cannot be represented, and the energy density of the battery is reduced;
(3) The service life of the battery may also be reduced; the reason is that around the implanted sensor, the transmission path of lithium ions is affected, there is a possibility of causing precipitation of lithium, and thus, a battery decay pattern is changed, thereby reducing the service life of the battery.
In addition, whether the battery pack or the battery bin body triggers the opening action of the battery explosion-proof valve is judged by detecting the air pressure value of the battery pack or the battery bin body according to the change of the air pressure value, and in the practical implementation process, the core point of the method is to design a battery vacuum bin or a closed space, and the method has the following defects:
(1) The manufacturing cost is high, and more than one mechanism is needed to be matched to form a vacuum environment;
(2) The manufacturing process is greatly different from the existing battery grouping technology or battery PACK technology, and although the welding technology for protecting the vacuum environment is applied to the battery core working procedure, the technology is still immature, and the related application is hardly carried out in the battery grouping working procedure;
(3) The related variables which need to be controlled in the process of transportation and use of the battery vacuum bin are also greatly different from the typical design of the battery PACK technology, and if the variables are not well controlled, the vacuum bin can be damaged.
Therefore, in the prior art, by monitoring whether the explosion-proof valve of the battery is opened or not, and then identifying the hidden danger of thermal runaway of the battery, a method for acquiring the pressure value in the current core or a method for designing a vacuum chamber or a closed space has certain difficulty, influences the design parameters of the battery, even causes the instability of the valve opening pressure of the explosion-proof valve, and hardly determines the time node of the opening of the explosion-proof valve; moreover, because the air pressure is generally between 0.3 and 0.8mpa when the explosion-proof valve is opened, the range is wide, if some external interference force is added, the valve opening pressure value of the explosion-proof valve is more discrete, whether the explosion-proof valve is opened or not is difficult to judge, and the hidden danger of thermal runaway of the battery cannot be accurately identified and early warning cannot be sent out in time.
Disclosure of Invention
In order to improve the recognition accuracy of potential battery thermal runaway hazards, the application provides a method, a device, a terminal and a storage medium for recognizing the potential battery thermal runaway hazards.
In a first aspect, the application provides a method for identifying potential thermal runaway hazards of a battery, which adopts the following technical scheme: a rigid mechanism is arranged on one side of the expansion direction of the battery, and a pressure sensor is arranged on one side of the rigid mechanism, which is not contacted with the battery; the method comprises the following steps:
Acquiring a pressure value of the pressure sensor, establishing an initial pressure reference, and recording the pressure value of the current pressure sensor as an initial pressure value F P0;
Judging whether the pressure sensor fails or not based on the measuring range of the pressure sensor and the initial pressure value F P0;
If yes, sending out a warning of the failure of the pressure sensor;
If not, based on the detection frequency f, acquiring the pressure value of the pressure sensor in real time, and identifying whether the battery has a thermal runaway hidden trouble or not based on the pressure value acquired in real time.
By adopting the technical scheme, the pressure sensor and the rigidity mechanism are selected and arranged in the expansion direction of the battery, the pressure value of the pressure sensor is obtained in real time, and the explosion-proof valve can be timely perceived and early-warned through a series of calculation and judgment, so that the high-precision identification of the hidden danger of thermal runaway of the battery is realized; compared with the existing mode of detecting the pressure in the battery, the technical scheme of the application does not need to use an air pressure sensor to detect the air pressure in the battery core, avoids the position of an explosion-proof valve, is directly outside the battery, does not need to damage the internal structure and parameters of the battery, does not need to design a vacuum chamber or a closed space of the battery, effectively inhibits the expansion of the battery core, is beneficial to the positive electrode, the negative electrode and the diaphragm of the battery core to keep a lithium ion channel, and can delay the capacity water jump of the battery; the technical scheme of the application is applicable to the conditions of single battery cells, multiple battery cells or battery modules, and is more convenient to use.
In a specific embodiment, before the acquiring, based on the detection frequency f, the pressure value of the pressure sensor in real time, the method further includes:
acquiring the operation data of the battery, and judging whether a potential risk event exists in the battery currently based on the operation data of the battery;
If yes, adjusting the preset initial detection frequency f1 to obtain a detection frequency f;
The potential risk event comprises one or more of battery short-circuit time exceeding a preset short-circuit time threshold, battery overcharge time exceeding a preset overcharge time threshold and battery temperature rise rate exceeding a preset temperature rise rate threshold.
Through adopting above-mentioned technical scheme, the staff can set for an initial detection frequency f1 to the battery, when practical application, again according to the operation data of battery, when judging that the battery exists the potential risk event, indicate that during this period explosion-proof valve opens the probability bigger, the probability that the battery takes place thermal runaway is bigger also, consequently can correspond the increase initial detection frequency f1, improves the recognition precision to the hidden danger of battery thermal runaway.
In a specific embodiment, based on the detection frequency f, the pressure value of the pressure sensor is obtained in real time, and based on the pressure value obtained in real time, whether the battery has a thermal runaway risk is identified, which specifically includes:
Generating a plurality of detection time nodes based on the detection frequency f, and acquiring the pressure value of the pressure sensor, the cycle number a of the battery and the environmental temperature T of the battery in real time at each detection time node;
Based on the pressure value of the pressure sensor, a pressure value sequence Q1, Q1= { F P1,FP2,FP3……FPn }; wherein n is a natural number, and F Pn represents a pressure value corresponding to the nth detection time node of the pressure sensor;
Estimating an expansion force value of the battery based on the cycle number a, the ambient temperature T and a pre-constructed expansion force estimation model to obtain an expansion force value sequence Q2, Q2= { F e1,Fe2,Fe3……Fen }; wherein n is a natural number, and F en represents an expansion force value corresponding to the battery at an nth detection time node;
Based on the pressure value sequence Q1 and the expansion force value sequence Q2, judging whether each pressure value in the pressure value sequence Q1 and a corresponding expansion force value in the expansion force value sequence Q2 satisfy: f Pn≤FP0+Fen; if yes, determining that the battery has a thermal runaway hidden trouble, and giving out an early warning.
By adopting the technical scheme, when the cycle number a of the battery and the ambient temperature T change, the expansion force of the battery also changes continuously, so that in the identification process of the potential thermal runaway hazard of the battery, on one hand, the expansion force value of the battery is estimated through an expansion force estimation model based on the cycle number a of the battery and the ambient temperature T; on the other hand, according to the pressure value obtained by the pressure sensor in real time, through multiple comparison and judgment, if the actual collected pressure value and the estimated expansion force value all meet F Pn≤FP0+Fen in a plurality of times, the actual pressure value in the battery is smaller than the theoretical estimated value in a period of time, at the moment, the explosion-proof valve can be judged to be opened and the pressure of the battery is relieved, and the potential risk of thermal runaway of the battery can be accurately warned, so that the manual intervention is facilitated in time. Erroneous judgment is effectively avoided.
In a specific embodiment, the expansion force estimation model comprises:
Fe=k1*ln(a)+△Fe+m；
Wherein F e is an expansion force value, and the unit is kN; k 1 is a cyclic attenuation characteristic quantity, and the unit is kN; a is the number of cycles; Δf e characterizes the influence of the ambient temperature T on the expansion force, Δf e =0 when the ambient temperature T is less than T s, Δf e=k2*(T-Ts)²,k2 is a temperature characteristic quantity when the ambient temperature T is greater than or equal to T s, and kN/°c 2;Ts is a standard ambient temperature; m is the correction amount and the unit is kN.
In a specific embodiment, based on the detection frequency f, the pressure value of the pressure sensor is obtained in real time, and based on the pressure value obtained in real time, whether the battery has a thermal runaway risk is identified, and the method specifically further includes:
Sliding window sampling is carried out on the pressure value sequence Q1 to obtain a pressure value subsequence Q3{ F Pa,FPa+1……FPb }; wherein a and b are natural numbers, and a is more than b and less than or equal to n;
Judging whether the data in the pressure value subsequence Q3 are all larger than F Pmax;
If yes, determining that the pressure sensor fails, and sending out a prompt; wherein F Pmax is the range of the pressure sensor.
By adopting the technical scheme, whether the pressure sensor fails or not is detected in real time in the process of identifying the potential thermal runaway hazards of the battery, and erroneous judgment caused by the failure of the pressure sensor is avoided.
In a specific embodiment, the method further comprises, before obtaining the pressure value of the pressure sensor and establishing the initial pressure reference:
Controlling the cyclic charge and discharge of the battery, and obtaining the pressure change conditions of each position of the expansion side of the battery in the cyclic charge and discharge process of the battery, so as to obtain a pressure change cloud picture of the battery;
and determining the installation position of the pressure sensor on the rigid mechanism based on the pressure change cloud chart.
In a specific embodiment, the acquiring the pressure value of the pressure sensor, establishing an initial pressure reference, and recording the pressure value of the current pressure sensor as an initial pressure value F P0 specifically includes:
acquiring a voltage value output by the pressure sensor and recording the voltage value as an initial voltage value V0;
based on the initial voltage value V0, the measuring range, the power supply voltage and the sensitivity of the pressure sensor, an initial pressure value F P0 is obtained through calculation;
The relation between the pressure value of the pressure sensor and the voltage value output by the pressure sensor is as follows:
Pressure value/measurement range= (output voltage value/supply voltage) = (sensitivity).
By adopting the technical scheme, the initial pressure value F P0 is calculated according to the initial voltage value V0 initially output by the pressure sensor and by combining the data of the measuring range, the power supply voltage and the sensitivity of the pressure sensor, and the initial pressure reference value is established, so that whether the battery has the thermal runaway hidden trouble or not can be conveniently judged.
In a second aspect, the present application provides a device for identifying potential thermal runaway hazards of a battery, which adopts the following technical scheme: the device applies the method for identifying potential thermal runaway of a battery in the first aspect or any of the possible embodiments of the first aspect,
The device comprises an MCU, a rigid mechanism and a pressure sensor, wherein the MCU is in communication connection with the pressure sensor; a rigid mechanism is arranged on one side of the expansion direction of the battery, and a pressure sensor is arranged on one side of the rigid mechanism, which is not contacted with the battery;
The MCU is used for acquiring the pressure value of the pressure sensor, establishing an initial pressure reference, and recording the pressure value of the current pressure sensor as an initial pressure value F P0;
The MCU is further used for judging whether the pressure sensor fails or not based on the measuring range of the pressure sensor and the initial pressure value F P0; if yes, the MCU sends out a pressure sensor failure prompt, if not, the MCU acquires the pressure value of the pressure sensor in real time based on the detection frequency f, and identifies whether the battery has a thermal runaway hidden trouble based on the pressure value acquired in real time.
In a third aspect, the present application provides a terminal, which adopts the following technical scheme: the terminal comprises a processor, a memory and a communication bus; the communication bus is used for realizing connection communication between a processor and a memory, and the processor is used for executing one or more programs stored in the memory to realize the method for identifying the thermal runaway hidden trouble of the battery in the first aspect or any implementation mode of the first aspect.
In a fourth aspect, the present application provides a computer readable storage medium, which adopts the following technical scheme: the computer readable storage medium stores instructions that, when executed, perform a method of identifying a thermal runaway risk of a battery as described above in the first aspect or any of the possible embodiments of the first aspect.
In summary, the technical scheme of the application at least comprises the following beneficial technical effects:
1. The pressure sensor and the rigidity mechanism are selected and arranged in the expansion direction of the battery, the pressure value of the pressure sensor is obtained in real time, and through a series of calculation and judgment, the potential thermal runaway hazard of the battery can be timely sensed and early warned, so that the identification precision of the potential thermal runaway hazard of the battery is improved;
2. compared with the existing mode of detecting the pressure in the battery, the technical scheme of the application does not need to use an air pressure sensor to detect the air pressure in the battery core, avoids the position of an explosion-proof valve, is directly outside the battery, does not need to damage the internal structure and parameters of the battery, does not need to design a vacuum chamber or a closed space of the battery, effectively inhibits the expansion of the battery core, is beneficial to the positive electrode, the negative electrode and the diaphragm of the battery core to keep a lithium ion channel, and can delay the capacity water jump of the battery; the technical scheme of the application is applicable to the conditions of single battery cell, multiple battery cells or battery modules, and is more convenient to use;
3. In the identification process of the potential thermal runaway hazard of the battery, on one hand, based on the cycle number a of the battery and the environmental temperature T, the expansion force value of the battery is estimated through an expansion force estimation model; on the other hand, according to the pressure value obtained through the pressure sensor in real time, through multiple comparison and judgment, if the actual collected pressure value and the estimated expansion force value all meet F Pn≤FP0+Fen in a continuous and multiple time, the actual pressure value in the battery is smaller than the theoretical estimated value in a period of time, at the moment, the explosion-proof valve can be judged to be opened and the battery is decompressed, and the potential thermal runaway hazard of the battery at the moment can be accurately warned, so that the manual intervention is convenient in time. Erroneous judgment is effectively avoided.
Drawings
FIG. 1 is an exploded view of a pressure sensor, a rigidity mechanism, and a battery in an embodiment of the application;
FIG. 2 is a schematic diagram of a first process of identifying a thermal runaway risk of a battery according to an embodiment of the present application;
FIG. 3 is a schematic diagram of a second flow chart of a method for identifying potential thermal runaway hazards of a battery in an embodiment of the application;
FIG. 4 is a graph showing the relationship between the expansion force value and the number of cycles in the embodiment of the present application;
FIG. 5 is a cloud of battery expansion side pressure changes in an embodiment of the application;
FIG. 6 is a schematic diagram of signal connections of a pressure sensor in an embodiment of the application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, embodiments of the present application will be described in further detail with reference to the accompanying drawings.
According to the electrochemical characteristics of a lithium battery, the change of the expansion force of the battery is from the overall influence of the process of removing lithium from the graphite of the negative electrode and the macroscopic change of the anode olive Dan Tieli pole piece, the expansion rate is strongly related to the SOH (health degree) of the battery, and in practical application, as the SOH of the battery is reduced, irreversible side reaction occurs in the battery, gas is generated inside the battery, and the external appearance is shown as swelling of the battery; when the air pressure generated by the bulge force acts on the explosion-proof valve and exceeds the bearing limit, the explosion-proof valve is opened; after the explosion-proof valve is opened, the battery is decompressed, so that the explosion can not be immediately started, when the inflammable and explosive gas volatilized from the electrolyte in the battery contacts with oxygen in the air, the fire can be caused once sparks exist, such as electrostatic ignition or micro short circuit of the electrode plate. Therefore, from the opening of the explosion-proof valve to the occurrence of fire disaster of the battery, a certain time exists in the middle of the opening, if the opening node of the explosion-proof valve of the battery can be accurately identified, the node of the battery with the hidden danger of thermal runaway can be accurately identified, and a worker can execute corresponding operation by utilizing the time period, so that the occurrence of the thermal runaway phenomenon can be effectively prevented.
The embodiment of the application provides a method for identifying potential hazards of thermal runaway of a battery, which takes a battery module formed by square batteries as an example, as shown in fig. 1, the arrangement of the battery, a rigidity mechanism and a pressure sensor is shown in the figure, one side of the battery in the expansion direction is provided with the rigidity mechanism, one side of the rigidity mechanism, which is not contacted with the battery, is provided with the pressure sensor, the pressure sensor and the rigidity mechanism are fixed on the battery through a fixing plate, and preferably, no gap exists between the pressure sensor and the rigidity mechanism, namely, the gap is 0.
In the present application, a rigidity mechanism for transmitting a force generated when the battery expands to the pressure sensor is provided between the pressure sensor and the battery. The setting of the rigid mechanism has the following advantages: firstly, the contact area is increased, so that the situation that the contact area is too small when the pressure sensor is directly arranged on the battery is avoided, and the battery shell is easily damaged; secondly, the pressure sensor is convenient to collect the expansion force of the battery better, the force generated by the expansion of the battery can be transmitted to the pressure sensor better, when any position of the battery, which is in contact with the rigid mechanism, expands, the rigid mechanism can bulge, and particularly, the central position of the rigid mechanism bulges; in particular, the rigidity mechanism is, for example, an aluminum plate having a relatively high rigidity, and of course, other materials may be used, and the present application is not limited to this, as long as the rigidity mechanism can transmit the expansion force at any position on the battery side to the pressure sensor in a good manner when the rigidity mechanism is in contact with the battery.
As shown in fig. 2 and 3, the method comprises steps S1-S3.
S1, acquiring a pressure value of the pressure sensor, establishing an initial pressure reference, and recording the pressure value of the current pressure sensor as an initial pressure value F P0.
In one possible implementation manner, in step S1, a pressure value of the pressure sensor is obtained, an initial pressure reference is established, and a current pressure value of the pressure sensor is recorded as an initial pressure value F P0, which specifically includes:
a1, acquiring a voltage value output by the pressure sensor, and recording the voltage value as an initial voltage value V0;
A2, obtaining an initial pressure value F P0 through calculation based on the initial voltage value V0, the measuring range, the power supply voltage and the sensitivity of the pressure sensor;
The relation between the pressure value of the pressure sensor and the voltage value output by the pressure sensor is as follows:
Pressure value/measurement range= (output voltage value/supply voltage) = (sensitivity).
In step A1, after the voltage value output by the pressure sensor is obtained, the voltage value output by the pressure sensor may be conditioned to obtain a voltage value with higher accuracy. The voltage value signal output by the pressure sensor can not be accurately collected due to the fact that the signal amplitude is too small, or the voltage value signal is too large and exceeds a bearable range, so that equipment for receiving the voltage value output by the pressure sensor is damaged, a signal conditioning process is increased, interference noise is filtered, and the collection accuracy of the pressure value of the pressure sensor is improved.
Through the steps A1-A2, firstly, according to an initial voltage value V0 initially output by the pressure sensor, an initial pressure value F P0 is calculated by combining the data of the measuring range, the power supply voltage and the sensitivity of the pressure sensor, and through establishing an initial pressure reference value, whether the battery explosion-proof valve is opened or not is conveniently judged in the follow-up process.
S2, judging whether the pressure sensor fails or not based on the measuring range of the pressure sensor and the initial pressure value F P0; if yes, sending out a warning of the failure of the pressure sensor;
In step S2, it is determined whether the pressure sensor fails, specifically, the following determination method is adopted: judging whether the initial pressure value F P0 meets 0 < F P0＜FPmax; if yes, the pressure sensor is not disabled, and if not, the pressure sensor is disabled; wherein F Pmax is the range of the pressure sensor.
And S3, if not, acquiring the pressure value of the pressure sensor in real time based on the detection frequency f, and identifying whether the battery has a thermal runaway hidden trouble or not based on the pressure value acquired in real time.
In step S3, the process of acquiring the pressure value of the pressure sensor in real time refers to the above steps A1-A2, and the voltage value output by the pressure sensor is first acquired and recorded as a voltage value V; based on the voltage value V, and the range, supply voltage, and sensitivity of the pressure sensor, the formula is: pressure value/measuring range= (output voltage value/power supply voltage) ×sensitivity, and calculating to obtain a corresponding pressure value. And will not be described in detail herein.
In a possible implementation manner, step S3, before obtaining the pressure value of the pressure sensor based on the detection frequency f, further includes the following steps:
B1, acquiring operation data of the battery, and judging whether a potential risk event exists in the battery currently based on the operation data of the battery;
B2, if yes, adjusting a preset initial detection frequency f1 to obtain a detection frequency f;
If not, taking the preset initial detection frequency f1 as the detection frequency f;
The potential risk event comprises one or more of battery short-circuit time exceeding a preset short-circuit time threshold, battery overcharge time exceeding a preset overcharge time threshold and battery temperature rise rate exceeding a preset temperature rise rate threshold.
The staff can set an initial detection frequency f1 for the battery, when the staff is in actual use, and when the potential risk event of the battery is judged according to the operation data of the battery, the probability that the explosion-proof valve is opened during the period is higher, and the probability that the battery is out of control is also higher, so that the initial detection frequency f1 can be correspondingly increased to obtain the detection frequency f, and the identification precision of the hidden danger of the battery in thermal control is improved.
Further, the above-mentioned detection frequency f can be adjusted by those skilled in the art based on the number of batteries. Specifically, the method for identifying the potential thermal runaway hazards of the battery can be applied to a group of batteries, and can identify a plurality of groups of batteries at the same time; wherein the detection frequency f can be increased when the number of battery packs is increased.
In a possible embodiment, before step S1, the method further comprises the following steps:
initializing a system; the system initialization comprises system clock initialization, timer initialization, communication interface initialization and analog sampling ADC initialization.
In one possible implementation manner, step S3, based on the detection frequency f, acquires the pressure value of the pressure sensor in real time, and identifies whether the battery has a thermal runaway risk based on the pressure value acquired in real time, specifically includes the following steps:
c1, generating a plurality of detection time nodes based on detection frequency f, and acquiring a pressure value of the pressure sensor, cycle times a of the battery and an environment temperature T of the battery in real time at each detection time node;
C2, based on the pressure value of the pressure sensor, obtaining a pressure value sequence Q1, Q1= { F P1,FP2,FP3……FPn }; wherein n is a natural number, and F Pn represents a pressure value corresponding to the nth detection time node of the pressure sensor;
c3, estimating the expansion force value of the battery based on the cycle number a, the ambient temperature T and a pre-constructed expansion force estimation model to obtain an expansion force value sequence Q2, Q2= { F e1,Fe2,Fe3……Fen }; wherein n is a natural number, and F en represents an expansion force value corresponding to the battery at an nth detection time node;
C4, based on the pressure value sequence Q1 and the expansion force value sequence Q2, judging whether each pressure value in the pressure value sequence Q1 and a corresponding expansion force value in the expansion force value sequence Q2 meet the following conditions: f Pn≤FP0+Fen; if yes, the explosion-proof valve of the battery is determined to be opened, namely the battery is determined to have a thermal runaway hidden trouble, an early warning is sent out, and a manual intervention is requested to avoid secondary accidents such as fire and the like;
if not, determining that the current battery has no thermal runaway hidden trouble, and repeatedly executing the steps of C1-C4 to continuously monitor the battery.
Note that, among the plurality of detection time nodes generated above, the time difference Δt=1/f between any two adjacent detection time nodes.
And when the battery is subjected to one complete charge and discharge, the battery is characterized to finish one cycle, namely the cycle number a of the battery is increased once. Preferably, n may be 10, that is, when 10 detection time nodes are generated based on the detection frequency F, and at each detection time node, F Pn≤FP0+Fen is satisfied by the pressure value obtained in real time and the estimated expansion force value for 10 consecutive times, that is, each time the collected pressure value is equal to or less than the sum of the initial pressure value F P0 and the estimated expansion force value, it is determined that the explosion-proof valve of the battery is opened, and there is a thermal runaway hidden danger in the battery.
In one possible implementation manner, step S3, based on the detection frequency f, acquires the pressure value of the pressure sensor in real time, and identifies whether the battery has a thermal runaway hidden danger based on the pressure value acquired in real time, and specifically further includes:
C5, sampling the pressure value sequence Q1 in a sliding window to obtain a pressure value subsequence Q3{ F Pa,FPa+1……FPb }; wherein a and b are natural numbers, and a is more than b and less than or equal to n;
Judging whether the data in the pressure value subsequence Q3 are all larger than F Pmax;
If yes, determining that the pressure sensor fails, and sending out a prompt; wherein F Pmax is the range of the pressure sensor.
Through the step C5, in the process of identifying the potential thermal runaway hazards of the battery, whether the pressure sensor fails or not is detected in real time, and erroneous judgment caused by the failure of the pressure sensor is avoided.
Through the steps C1-C4, when the cycle number a of the battery and the ambient temperature T change, the expansion force of the battery also changes continuously, so that in the identification process of the hidden danger of thermal runaway of the battery, on one hand, the expansion force value of the battery is estimated through an expansion force estimation model based on the cycle number a of the battery and the ambient temperature T; on the other hand, according to the pressure value obtained through the pressure sensor in real time, through multiple comparison and judgment, if the actual collected pressure value and the estimated expansion force value all meet F Pn≤FP0+Fen in a continuous and multiple time, the actual pressure value in the battery is smaller than the theoretical estimated value in a period of time, at the moment, the explosion-proof valve can be judged to be opened and the battery is decompressed, and the potential thermal runaway hazard of the battery at the moment can be accurately warned, so that the manual intervention is convenient in time. Erroneous judgment is effectively avoided.
In one possible embodiment, the expansion force estimation model includes: f e=k1*ln(a)+△Fe +m;
wherein F e is an expansion force value, and the unit is kN; k 1 is a cyclic attenuation characteristic quantity, and the unit is kN; a is the number of cycles; Δf e characterizes the influence of the ambient temperature T on the expansion force, Δf e =0 when the ambient temperature T is less than T s, Δf e=k2*(T-Ts)²,k2 is a temperature characteristic quantity when the ambient temperature T is greater than or equal to T s, and kN/°c 2;Ts is a standard ambient temperature; m is the correction amount, and the unit is kN; standard ambient temperature T s and ambient temperature T are in units of ℃.
It should be noted that, a person skilled in the art may determine the value of the standard ambient temperature T s from factors such as the type of the battery and the variation condition of the battery expansion force under different ambient temperatures, which is not particularly limited in the present application, when the ambient temperature T is less than T s, the change of the ambient temperature basically does not cause the increase of the battery expansion force, and when the ambient temperature T is greater than or equal to T s, the change of the ambient temperature causes the increase of the battery expansion force as a judgment standard, and particularly determines the value of the standard ambient temperature T s. For example, the standard ambient temperature T s may be 10 ℃.
In a possible implementation manner, step S1 obtains a pressure value of the pressure sensor, and before establishing the initial pressure reference, the method further includes the following steps:
D1, collecting an expansion force value F e in the battery cyclic charge and discharge process at a standard environment temperature T s to obtain first corresponding data between the expansion force value F e and the cyclic times a; fitting a first functional relation between the expansion force value F e and the cycle number a based on the first corresponding data;
Specifically, the first functional relationship is: f e=k1 ×ln (a) +m; wherein the unit of the expansion force value F e is kN; k 1 is a cyclic attenuation characteristic quantity, and the unit is kN; a is the number of cycles; m is the correction amount and the unit is kN.
By means of the step D1, specific values of the cyclic attenuation characteristic quantity k 1 and the correction quantity m can be obtained after fitting the first functional relation between the expansion force value F e and the cyclic number a.
D2, respectively collecting expansion force values F e in the cyclic charge and discharge processes of the battery at different environmental temperatures T to obtain a second corresponding data set; the second corresponding data set includes second corresponding data between the expansion force value F e and the number of cycles a at different ambient temperatures T.
D3, obtaining a first standard expansion force value F es1 corresponding to the battery when the cycle number a is the standard reference number a x at the standard environment temperature T s based on a preset standard reference number a x and the first functional relation;
Obtaining a second standard expansion force value F es2 set based on a preset standard reference frequency a x and the second corresponding data set; the second standard expansion force value F es2 set comprises a second standard expansion force value F es2 corresponding to the battery when the cycle number a is the standard reference number a x at different ambient temperatures T;
Obtaining a third corresponding data set based on the first standard expansion force value F es1 corresponding to the standard environment temperature T s and the second standard expansion force value F es2 corresponding to the different environment temperatures T; the third corresponding data set comprises third corresponding data between an expansion force difference DeltaF e and a temperature difference DeltaT; wherein Δf e=Fes2-Fes1,△T=T-Ts.
It should be noted that, those skilled in the art may flexibly set the value of the standard reference number a x according to factors such as the actual application scenario of the battery, the expansion force variation condition of the battery under different cycle numbers, and the like, which is not limited in the present application. For example, under different ambient temperatures, when the cycle number a of the battery is the standard reference number a x, the expansion force values corresponding to the battery are smaller and more stable, and those skilled in the art can determine the value of the standard reference number a x from this point of view, so that the expansion force estimation model is more accurately constructed.
D4, fitting a third functional relation between the expansion force difference DeltaF e and the temperature difference DeltaT based on the third corresponding data set;
specifically, the third functional relationship is:
Δf e =0 when the ambient temperature T < T s;
When the ambient temperature T is more than or equal to T s, deltaF e=k2 is DeltaT; further Δt=t-T s, Δf e=k2*(T-Ts); wherein DeltaF e represents the influence quantity of the ambient temperature T on the expansion force, and the unit is kN; k 2 is a temperature characteristic quantity, and the unit is kN/. Degree.C. 2.
By the step D4, after fitting the third functional relation between the expansion force difference Δf e and the temperature difference Δt, a specific value of the temperature characteristic k 2 is obtained.
D5, constructing an expansion force estimation model based on the first functional relation and the third functional relation;
Specifically, the expansion force estimation model includes: f e=k1*ln(a)+△Fe +m;
Wherein F e is an expansion force value, and the unit is kN; k 1 is a cyclic attenuation characteristic quantity, and the unit is kN; a is the number of cycles; deltaF e characterizes the influence of the ambient temperature T on the expansion force in kN; when the ambient temperature T is less than T s, deltaF e =0, when the ambient temperature T is more than or equal to T s, deltaF e=k2*(T-Ts)²,k2 is a temperature characteristic quantity, the unit is kN/. Degree.C 2;Ts is a standard ambient temperature, and the unit is the temperature; m is the correction amount and the unit is kN.
In the above step, when calculating the temperature characteristic quantity k 2, a set of fitted third functional relation is adopted when the cycle number a is the standard reference number a x, so as to obtain a specific numerical value of the temperature characteristic quantity k 2; of course, a person skilled in the art may change the values of the standard reference times a x, select multiple sets of data, respectively fit a third functional relationship between the expansion force difference Δf e and the temperature difference Δt under different standard reference times a x, thereby obtaining values of a plurality of temperature feature quantities k 2, and calculate the most accurate temperature feature quantity k 2 by taking an average value or other manners based on the values of the plurality of temperature feature quantities k 2.
Thus, through steps D1-D5 described above, a first functional relationship between the expansion force F e and the number of cycles a is first derived; and then, through a series of data acquisition and processing, the influence of the ambient temperature T on the expansion force is evaluated, and a third functional relation is obtained, so that an expansion force estimation model with higher precision is constructed according to the first functional relation and the third functional relation.
For example, referring to fig. 4, fig. 4 shows the functional relationship between the expansion force F e of the battery and the cycle number a at three different sets of ambient temperatures T, i.e., the ambient temperatures T are 10 ℃, 25 ℃ and 45 ℃, respectively, and a schematic diagram of the corresponding functional relationship is drawn, and it can be seen that the expansion force F e is positively correlated with the cycle number a; taking a curve with a temperature of 25℃as an example, when a < 10, the expansion force F e satisfies: f e is less than 1.5kN and more than 0.7 kN; when a is more than or equal to 10 and less than 20, the expansion force F e meets the following conditions: f e and F e are less than or equal to 1.5 and less than 2kN; when a is more than or equal to 20 and less than 100, the expansion force F e meets the following conditions: f e is more than or equal to 2kN and less than 3kN; when a is more than or equal to 100 and less than 400, the expansion force F e meets the following conditions: f e is more than or equal to 3kN and less than 4kN; when a is more than or equal to 400 and less than 1000, the expansion force F e meets the following conditions: f e is less than or equal to 4kN and less than 4.5kN; when a > 1000, the expansion force F e satisfies: f e > 4.5kN. As can also be seen from fig. 4, when the explosion-proof valve is opened, the expansion force F e of the battery is rapidly reduced when the battery is depressurized.
In a possible implementation manner, step S1 obtains a pressure value of the pressure sensor, and before establishing the initial pressure reference, the method further includes the following steps:
E1, controlling the cyclic charge and discharge of the battery, and obtaining the pressure change conditions of each position of the expansion side of the battery in the cyclic charge and discharge process of the battery, so as to obtain a pressure change cloud picture of the battery; the swelling side of the battery is the swelling side when the battery swells;
and E2, determining the installation position of the pressure sensor on the rigid mechanism based on the pressure change cloud chart.
For example, referring to fig. 5, for the pressure change conditions at each position on the expansion side of the battery during the cyclic charge and discharge of the battery, the darker the color indicates the greater the pressure value, it can be seen that: the pressure of the side from the edge to the center position is gradually increased, the pressure of the center position of the battery is the largest, and the battery shows the characteristic that the pressure is larger when the battery is closer to the center position in the whole cycle charge and discharge process of the battery, so that the identification of the opening of the battery explosion-proof valve is more accurate if the pressure sensor is arranged at the center position of the expansion side of the battery for the battery. Of course, the pressure distribution conditions of the batteries with different shapes may be different, and the person skilled in the art can refer to the method, and for the batteries with different shapes, the optimal mounting position of the pressure sensor on the rigid mechanism can be obtained by detecting the pressure of each position on the expansion side of the battery.
Preferably, the pressure sensor is mounted in a central position of the rigid mechanism.
Therefore, the application selects the pressure sensor and the rigidity mechanism, is arranged in the expansion direction of the battery, acquires the pressure value of the pressure sensor in real time, and identifies whether the battery has thermal runaway hidden trouble through a series of calculation and judgment. Compared with the existing mode of detecting the pressure in the battery, the technical scheme of the application does not need to use an air pressure sensor to detect the air pressure in the battery core, avoids the position of an explosion-proof valve, is directly outside the battery, does not need to damage the internal structure and parameters of the battery, does not need to design a vacuum chamber or a closed space of the battery, effectively inhibits the expansion of the battery core, is beneficial to the positive electrode, the negative electrode and the diaphragm of the battery core to keep a lithium ion channel, and can delay the capacity water jump of the battery; the explosion-proof valve can be timely sensed and early warned when being opened, so that the high-precision identification of the hidden danger of thermal runaway of the battery is realized;
The identification method provided by the application is applicable to the conditions of single battery cells, multiple battery cells and battery modules, and can be used for identifying the thermal runaway hidden dangers of a plurality of batteries at the same time by only installing the rigid mechanism and the pressure sensor outside the corresponding battery structure when the identification method is required to be applied to the identification of the thermal runaway hidden dangers of the plurality of batteries, so that the cost is lower and the identification method is more convenient.
The embodiment of the application provides a device for identifying potential battery thermal runaway hazards, which is applied to the method for identifying potential battery thermal runaway hazards in the embodiment; specifically, the device comprises an MCU, a rigid mechanism and a pressure sensor; a rigid mechanism is arranged on one side of the expansion direction of the battery, a pressure sensor is arranged on one side of the rigid mechanism, which is not contacted with the battery, and no gap exists between the pressure sensor and the rigid mechanism; referring to fig. 6, the MCU is communicatively connected to the pressure sensor; the pressure sensor comprises a power line which is connected with a power supply; the pressure sensor also comprises two signal output lines which are respectively connected with the MCU, and specifically, the device also comprises a signal conditioning circuit, and the signal output lines are connected with the MCU through the signal conditioning circuit; the pressure sensor further includes a shield wire that is grounded.
The MCU is used for executing a system initialization process, wherein the system initialization comprises system clock initialization, timer initialization, communication interface initialization and analog sampling ADC initialization;
The MCU is used for acquiring the pressure value of the pressure sensor, establishing an initial pressure reference, and recording the pressure value of the current pressure sensor as an initial pressure value F P0;
The MCU is further used for judging whether the pressure sensor fails or not based on the measuring range of the pressure sensor and the initial pressure value F P0; if yes, the MCU sends out a pressure sensor failure prompt, if not, the MCU acquires the pressure value of the pressure sensor in real time based on the detection frequency f, and identifies whether the battery has a thermal runaway hidden trouble based on the pressure value acquired in real time.
An embodiment of the present application provides a terminal, including: a processor, a memory, and a communication bus; the communication bus is used for realizing connection communication between the processor and the memory, and the processor is used for executing one or more programs stored in the memory so as to realize the battery thermal runaway hidden danger identification method in the embodiment.
An embodiment of the present application provides a computer-readable storage medium storing instructions that, when executed, perform the method for identifying a thermal runaway risk of a battery described in the above embodiment.
The preferred embodiments of the present application are not intended to limit the scope of the present application, so: all equivalent changes in structure, shape and principle of the application should be covered in the scope of protection of the application.
Claims (8)
1. A method for identifying potential hazards of thermal runaway of a battery is characterized in that a rigid mechanism is arranged on one side of the expansion direction of the battery, and a pressure sensor is arranged on one side of the rigid mechanism, which is not in contact with the battery; the pressure sensor is installed at a central position of an expansion side of the battery, and the method includes:
Acquiring a pressure value of the pressure sensor, establishing an initial pressure reference, and recording the pressure value of the current pressure sensor as an initial pressure value F P0;
Judging whether the pressure sensor fails or not based on the measuring range of the pressure sensor and the initial pressure value F P0;
If yes, sending out a warning of the failure of the pressure sensor;
if not, based on the detection frequency f, acquiring the pressure value of the pressure sensor in real time, and identifying whether the battery has a thermal runaway hidden trouble or not based on the pressure value acquired in real time;
The method comprises the steps of acquiring a pressure value of the pressure sensor in real time based on a detection frequency f, and identifying whether a thermal runaway hidden danger exists in a battery based on the pressure value acquired in real time, and specifically comprises the following steps:
Generating a plurality of detection time nodes based on the detection frequency f, and acquiring the pressure value of the pressure sensor, the cycle number a of the battery and the environmental temperature T of the battery in real time at each detection time node;
Based on the pressure value of the pressure sensor, a pressure value sequence Q1, Q1= { F P1,FP2,FP3……FPn }; wherein n is a natural number, and F Pn represents a pressure value corresponding to the nth detection time node of the pressure sensor;
Estimating an expansion force value of the battery based on the cycle number a, the ambient temperature T and a pre-constructed expansion force estimation model to obtain an expansion force value sequence Q2, Q2= { F e1,Fe2,Fe3……Fen }; wherein n is a natural number, and F en represents an expansion force value corresponding to the battery at an nth detection time node;
Based on the pressure value sequence Q1 and the expansion force value sequence Q2, judging whether each pressure value in the pressure value sequence Q1 and a corresponding expansion force value in the expansion force value sequence Q2 satisfy: f Pn≤FP0+Fen; if yes, determining that the battery has a thermal runaway hidden trouble, and giving an early warning;
wherein the expansion force estimation model comprises: f e=k1*ln(a)+△Fe +m;
F e is the expansion force value, in kN; k 1 is a cyclic attenuation characteristic quantity, and the unit is kN; a is the number of cycles; Δf e characterizes the influence of the ambient temperature T on the expansion force, Δf e =0 when the ambient temperature T is less than T s, Δf e=k2*(T-Ts)²,k2 is a temperature characteristic quantity when the ambient temperature T is greater than or equal to T s, and kN/°c 2;Ts is a standard ambient temperature; m is the correction amount and the unit is kN.
2. The method for identifying potential thermal runaway in a battery according to claim 1, wherein before the acquiring the pressure value of the pressure sensor in real time based on the detection frequency f, further comprises:
acquiring the operation data of the battery, and judging whether a potential risk event exists in the battery currently based on the operation data of the battery;
If yes, adjusting the preset initial detection frequency f1 to obtain a detection frequency f;
The potential risk event comprises one or more of battery short-circuit time exceeding a preset short-circuit time threshold, battery overcharge time exceeding a preset overcharge time threshold and battery temperature rise rate exceeding a preset temperature rise rate threshold.
3. The method for identifying a thermal runaway risk of a battery according to claim 1, wherein the method for identifying a thermal runaway risk of a battery according to claim 1 comprises the steps of acquiring a pressure value of the pressure sensor in real time based on the detection frequency f, and identifying whether the thermal runaway risk exists in the battery based on the pressure value acquired in real time, and specifically further comprises:
Sliding window sampling is carried out on the pressure value sequence Q1 to obtain a pressure value subsequence Q3{ F Pa,FPa+1……FPb }; wherein a and b are natural numbers, and a is more than b and less than or equal to n;
Judging whether the data in the pressure value subsequence Q3 are all larger than F Pmax;
If yes, determining that the pressure sensor fails, and sending out a prompt; wherein F Pmax is the range of the pressure sensor.
4. The method for identifying a thermal runaway risk of a battery according to claim 1, wherein acquiring the pressure value of the pressure sensor, before establishing the initial pressure reference, further comprises:
Controlling the cyclic charge and discharge of the battery, and obtaining the pressure change conditions of each position of the expansion side of the battery in the cyclic charge and discharge process of the battery, so as to obtain a pressure change cloud picture of the battery;
and determining the installation position of the pressure sensor on the rigid mechanism based on the pressure change cloud chart.
5. The method for identifying a thermal runaway risk of a battery according to claim 1, wherein the step of obtaining the pressure value of the pressure sensor, establishing an initial pressure reference, and recording the current pressure value of the pressure sensor as an initial pressure value F P0, specifically comprises the steps of:
acquiring a voltage value output by the pressure sensor and recording the voltage value as an initial voltage value V0;
based on the initial voltage value V0, the measuring range, the power supply voltage and the sensitivity of the pressure sensor, an initial pressure value F P0 is obtained through calculation;
The relation between the pressure value of the pressure sensor and the voltage value output by the pressure sensor is as follows: pressure value/measurement range= (output voltage value/supply voltage) = (sensitivity).
6. The device is characterized by comprising an MCU, a rigid mechanism and a pressure sensor, wherein the MCU is in communication connection with the pressure sensor; a rigid mechanism is arranged on one side of the expansion direction of the battery, a pressure sensor is arranged on one side of the rigid mechanism, which is not contacted with the battery, and the pressure sensor is arranged at the center position of the expansion side of the battery;
The MCU is used for acquiring the pressure value of the pressure sensor, establishing an initial pressure reference, and recording the pressure value of the current pressure sensor as an initial pressure value F P0;
The MCU is further used for judging whether the pressure sensor fails or not based on the measuring range of the pressure sensor and the initial pressure value F P0; if yes, the MCU sends out a pressure sensor failure prompt, if not, the MCU acquires the pressure value of the pressure sensor in real time based on the detection frequency f, and identifies whether the battery has a thermal runaway hidden trouble or not based on the pressure value acquired in real time;
The MCU acquires the pressure value of the pressure sensor in real time based on the detection frequency f, and identifies whether the battery has a thermal runaway hidden trouble based on the pressure value acquired in real time, and specifically comprises the following steps:
the MCU generates a plurality of detection time nodes based on the detection frequency f, and acquires the pressure value of the pressure sensor, the cycle number a of the battery and the environmental temperature T of the battery in real time at each detection time node;
The MCU obtains a pressure value sequence Q1, Q1= { F P1,FP2,FP3……FPn } based on the pressure value of the pressure sensor; wherein n is a natural number, and F Pn represents a pressure value corresponding to the nth detection time node of the pressure sensor;
The MCU estimates the expansion force value of the battery based on the cycle number a, the ambient temperature T and a pre-constructed expansion force estimation model to obtain an expansion force value sequence Q2, Q2= { F e1,Fe2,Fe3……Fen }; wherein n is a natural number, and F en represents an expansion force value corresponding to the battery at an nth detection time node;
The MCU judges whether each pressure value in the pressure value sequence Q1 and a corresponding expansion force value in the expansion force value sequence Q2 meet the following conditions based on the pressure value sequence Q1 and the expansion force value sequence Q2: f Pn≤FP0+Fen; if yes, determining that the battery has a thermal runaway hidden trouble, and giving an early warning;
wherein the expansion force estimation model comprises: f e=k1*ln(a)+△Fe +m;
F e is the expansion force value, in kN; k 1 is a cyclic attenuation characteristic quantity, and the unit is kN; a is the number of cycles; Δf e characterizes the influence of the ambient temperature T on the expansion force, Δf e =0 when the ambient temperature T is less than T s, Δf e=k2*(T-Ts)²,k2 is a temperature characteristic quantity when the ambient temperature T is greater than or equal to T s, and kN/°c 2;Ts is a standard ambient temperature; m is the correction amount and the unit is kN.
7. A terminal, comprising: a processor, a memory, and a communication bus; the communication bus is used for realizing connection communication between a processor and a memory, and the processor is used for executing one or more programs stored in the memory so as to realize the battery thermal runaway hidden danger identification method according to any one of claims 1 to 5.
8. A computer-readable storage medium, characterized by: the computer readable storage medium stores instructions that, when executed, perform the battery thermal runaway hazard identification method of any of claims 1-5.
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