CN114779094A - Method and apparatus for swelling test of battery module - Google Patents
Method and apparatus for swelling test of battery module Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/374—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC] with means for correcting the measurement for temperature or ageing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/378—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC] specially adapted for the type of battery or accumulator
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/385—Arrangements for measuring battery or accumulator variables
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- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/392—Determining battery ageing or deterioration, e.g. state of health
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
- H01M10/482—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte for several batteries or cells simultaneously or sequentially
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- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/385—Arrangements for measuring battery or accumulator variables
- G01R31/387—Determining ampere-hour charge capacity or SoC
Abstract
The present invention relates to the field of battery management and diagnostics. The invention provides a method for expansion test of a battery module, wherein the battery module comprises a plurality of battery cells, and the method comprises the following steps: s1: acquiring parameters related to expansion characteristics of the battery module during a cycle charge and discharge operation of the battery module over a plurality of test cycles, wherein the parameters of the battery module are acquired in a charge and discharge phase and a recovery phase of at least one test cycle respectively; and, S2: performing trend analysis on the parameters cumulatively acquired over a plurality of test periods to draw conclusions about the state of health of the battery module. The invention also relates to equipment for the expansion test of the battery module. The invention provides a new analysis dimension for the state and structure degradation of the battery module, can analyze failure reasons from the expansion level, and lays a reliable foundation for the subsequent research and development of power batteries.
Description
Technical Field
The present invention relates to a method for the swelling test of a battery module, an apparatus for the swelling test of a battery module, and a computer program product.
Background
With the vigorous push and development of new energy technologies, more and more vehicles are driven by using power batteries as energy carriers. During the use of the power battery, the expansion or bulging of the battery core is a common phenomenon. In this case, because the rigidity restriction of the whole steel-aluminum frame of module, the reaction force that the battery core inflation produced can act on battery core itself, consequently can lead to finally that battery core is compressed and arouse cycle performance diving. Simultaneously, the power that the cell inflation produced may lead to the module frame to warp on the whole to make the battery module can't correctly joint with electronic equipment.
Therefore, it is necessary to study the swelling characteristics of the battery to avoid potential safety hazards in practical applications.
The typical current cycle test method generally adopts a mode of constant current charging to a cut-off voltage and then constant current discharging. However, most of the current mainstream methods only consider data sampling performed in the charging and discharging phase and analyze accumulated results after several cycles, but the consideration on the battery characteristics in the standing recovery phase is very little, which not only results in that the analysis on the overall health state of the battery is not comprehensive, but also the standing time period in each cycle is not fully utilized, resulting in waste of time efficiency.
It is therefore desirable to provide an improved battery cycling test scheme to improve test efficiency while ensuring that battery state of health can be analyzed in the expansion dimension.
Disclosure of Invention
It is an object of the present invention to provide a method for the swelling test of a battery module, an apparatus for the swelling test of a battery module and a computer program product to solve at least some of the problems of the prior art.
According to a first aspect of the present invention, there is provided a method for swelling test of a battery module including a plurality of cells, the method comprising the steps of:
s1: acquiring parameters related to expansion characteristics of the battery module during a cycle charge and discharge operation of the battery module over a plurality of test cycles, wherein the parameters of the battery module are acquired in a charge and discharge phase and a recovery phase of at least one test cycle respectively; and
s2: performing trend analysis on the parameters cumulatively acquired over a plurality of test periods to draw conclusions about the state of health of the battery module.
The invention comprises in particular the following technical concepts: it has been recognized that battery swelling events cause many characteristic changes in the battery as the number of charge and discharge increases, and by monitoring parameters related to swelling characteristics, a health analysis of battery performance can be performed well. In addition, the battery state is influenced by a plurality of environmental factors in the charging and discharging stage, and the expansion characteristic of the battery is in dynamic change, so that the detection result has certain uncertainty. By respectively acquiring data in the recovery period and the charge-discharge period of the cycle test, more sufficient data samples can be obtained under the limited cycle times so as to realize more stable analysis of the expansion characteristic of the battery.
Optionally, the conclusion about the state of health of the battery module includes:
the expansion level of the battery module and/or the battery cell over a plurality of test cycles;
the expansion level of the battery module and/or the battery core influences the cycle performance of the battery module and/or the battery core;
the influence of the expansion level of the battery module and/or the battery core on the overall frame structure of the battery module; and
the influence of the charge-discharge operation of the battery module on the expansion level of the battery module and/or the battery core.
The following technical advantages are achieved in particular here: compared with the conventional cycle life test of the battery, the novel analysis dimension is provided for the state degradation and the structure degradation of the battery module, the failure reason can be analyzed from the expansion level, and a reliable foundation is laid for the subsequent research and development of the power battery.
Optionally, the parameters related to the expansion characteristics include an expansion parameter and a cycle performance parameter, the expansion parameter includes an expansion force and an expansion rate of the battery module and/or the battery cell, and the cycle performance parameter includes an output voltage, a temperature, a capacity value, and a capacity retention rate of the battery module and/or the battery cell.
The following technical advantages are achieved in particular here: by recording multiple data types, a more complete analysis of battery performance can be performed over the entire life cycle, thereby locating the cause of the failure more quickly.
Optionally, different detection schemes are respectively applied to the battery module to determine the parameters in a charging and discharging phase and a recovery phase in the at least one test cycle; and/or
And in a charging and discharging phase and a recovery phase in the at least one test cycle, respectively, sampling the parameters at different sampling frequencies, wherein the sampling frequency applied in the charging and discharging phase is greater than the sampling frequency applied in the recovery phase.
The following technical advantages are achieved in particular here: therefore, the data acquisition mode can be adapted to the state change characteristics of the battery at different stages, and the data acquisition cost and the storage cost are reduced on the premise of ensuring the data samples to be sufficiently reliable.
Optionally, in each test cycle, the following operations are performed on the battery module:
charging the battery module to an upper limit voltage in a charging stage;
discharging the battery module to a lower limit voltage in a discharging stage;
a recovery phase is provided between the charging phase and the discharging phase and/or after the discharging phase, in which neither a charging operation nor a discharging operation is performed on the battery module.
The following technical advantages are achieved in particular here: by flexibly adjusting the position or sequence of the recovery stage in the test period, the time required by the whole cycle test can be shortened on the premise of ensuring the stable performance of the battery, and the test efficiency is improved.
Optionally, the battery module is charged in a constant current and/or constant current-constant voltage manner in the charging phase of each test cycle, and the battery module is discharged in a constant current manner, particularly at a fixed discharge rate, in the discharging phase of each test cycle; and/or
The charging phase of each test cycle is divided into a plurality of subintervals, in which the battery modules are charged at different charging rates, in particular at decreasing charging rates.
The following technical advantages are achieved in particular here: the charging process can be remarkably accelerated through a stepped charging strategy, so that the overall cycle test time is shortened. On the other hand, because the polarization effect is eliminated, the heating phenomenon of the battery is obviously reduced, and the overcharge is avoided, so that the battery is well protected.
Optionally, the method further comprises an operation preparation step before the cyclic charge and discharge operation is performed, wherein a test assembly for detecting the parameter related to the expansion characteristic is integrated into the battery module to be tested, wherein a certain number of cells in a partial section, in particular in a middle section, of the battery module are replaced by the test assembly.
The following technical advantages are achieved in particular here: this kind of embedded arrangement can effectively promote the detection precision of the inside bulging force of battery module to can let the test assembly adapt to different model batteries, expanded the range of application.
Optionally, the method further includes an initialization step before performing the cyclic charge and discharge operation, wherein the residual capacity of the battery module to be tested is discharged and the initial charge capacity and the initial discharge capacity of the battery module are detected.
The following technical advantages are achieved in particular here: the actual charge and discharge capacity of the battery may deviate from the nominal value, and by performing such measurements at one time under experimental environmental conditions, real reference capacity information can be obtained, thereby providing a good reference for subsequent performance decay analysis and making the analysis result more persuasive.
According to a second aspect of the present invention, there is provided an apparatus for swelling test of a battery module, the apparatus for performing the method according to the first aspect of the present invention, the apparatus comprising:
a charge and discharge unit configured to perform a cyclic charge and discharge operation on the battery module over a plurality of test periods;
a detection unit configured to acquire parameters of the battery module related to expansion characteristics during a cyclic charge and discharge operation of the battery module, the detection unit further configured to acquire the parameters of the battery module during a charge and discharge phase and a recovery phase of at least one test cycle, respectively; and
an analysis unit configured to perform trend analysis on the parameters cumulatively acquired over a plurality of test periods to draw a conclusion about the state of health of the battery module.
According to a third aspect of the present invention, a computer program product is provided, wherein the computer program product comprises a computer program for implementing the method according to the first aspect of the present invention when executed by a computer.
Drawings
The principles, features and advantages of the present invention may be better understood by describing the invention in more detail below with reference to the accompanying drawings. The drawings include:
fig. 1 illustrates a block diagram of an apparatus for swelling test of a battery module according to an exemplary embodiment of the present invention;
fig. 2 illustrates a flowchart of a method for a swelling test of a battery module according to an exemplary embodiment of the present invention;
FIG. 3 shows a flow chart of a process for performing a cyclical charge-discharge operation;
FIG. 4 shows a flow chart of one method step shown in FIG. 2;
fig. 5 a-5 b show the trend of capacity retention exhibited by square-can battery modules of two electrochemical systems when subjected to a swelling test by means of the method according to the invention;
fig. 6 shows the trend of the frame deformation amount of the battery module obtained by means of the method according to the present invention over time; and
fig. 7 shows the trend of the internal swelling force of the battery module obtained by means of the method according to the present invention over time.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and exemplary embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of the invention.
Fig. 1 shows a block diagram of an apparatus 1 for swelling test of a battery module according to an exemplary embodiment of the present invention.
As shown in fig. 1, a corresponding apparatus 1 is shown for the swelling test of the battery module 100. In this embodiment, the apparatus 1 includes a charging and discharging unit 10, an acquisition unit 20, and an analysis unit 30.
Here, the battery module 100 includes, for example, a case and a plurality of battery cells (not specifically shown for the sake of brevity) arranged within the case, which are stacked on each other in a certain direction to form the battery module 100. The battery module 100 relates to, for example, a lithium ion battery module, but it may also relate to other recyclable electrochemical cells having a high energy storage level.
In practical use, the battery module 100 may swell with the passage of time, which in turn causes degradation of various electrical and mechanical characteristics. In order to investigate such a state change, it is necessary to study the expansion characteristics of the battery module 100 over a plurality of charge and discharge cycles. For this reason, the cyclic charge and discharge process that the battery module undergoes during actual use is simulated by the charge and discharge unit 10.
Specifically, the charge and discharge unit 10 includes a charge module 11 and a corresponding charge switch 12. In the charging phase, the charging switch 12 is closed, and the charging module 11 charges the battery module 100 with a proper charging current. Here, depending on the selected charging strategy, the charging module 11 may adjust a desired charging current and charge the battery module 100 in a constant current manner or a constant current-constant voltage manner, for example. The charging module 11 also has a timer function, for example, to switch the charging rate at an appropriate timing.
In addition, the charge and discharge unit 10 further includes a variable load 13 and a corresponding discharge switch 14. In the discharging stage, the charging switch 12 is opened, the charging module 11 stops charging the battery module 100, and the discharging switch 14 is closed, so that the battery module 100 and the variable load 13 form a complete loop, and the battery module 100 can discharge electric energy on the variable load 13. Here, for example, a desired discharge current or discharge rate can be generated by appropriately adjusting the impedance of the variable load 13.
In order to monitor the parameters of the battery module 100 related to the swelling characteristics in real time over a plurality of test cycles, the battery module 100 is also connected to the acquisition unit 20. The acquisition unit 20 includes, for example, different types of test components to measure different types of parameters of the battery module 100. In the embodiment shown in fig. 1, the acquisition unit 20 includes, for example, a pressure sensor 21, a displacement sensor 22, a voltage measurement module 23, a current measurement module 24, and a temperature measurement/setting module 25.
The pressure sensor 21 may be coupled to the battery module 100, for example, externally or internally, and configured to measure the force due to cell swelling. The internal coupling means that the pressure sensor 21 is arranged in the battery module 100 so as to be able to replace a certain number of cells in a partial section, in particular in an intermediate section, of the battery module 100. Externally coupled means that the pressure sensor 21 is clamped to the housing of the battery module 100 in order to measure the force which is jointly generated by one or more cells and is exerted on the housing.
The displacement sensor 22 is, for example, used to detect the displacement of the end of the battery module 100 to be tested in at least one direction and output a displacement signal. As an example, one or more displacement sensors may be respectively disposed at corresponding positions on both sides of the battery module 100 in the length and width directions, for example, to further improve the test accuracy.
The voltage measuring module 23 is configured to be able to monitor the voltage across the entire battery module 100. In addition, the voltage measuring module 23 may also measure voltages at two ends of each battery cell of the battery module 100, so as to monitor the cycle performance of a single battery cell in real time. Here, the voltage measurement may be performed in a charging phase, a discharging phase, or a standing recovery phase.
The current measurement module 24 is configured to measure the current flowing through the battery module 100 over a plurality of test cycles, such current signals may be provided for accurate control of a charge-discharge strategy or for performing a health life analysis, for example. Here, although the directly measured parameter is the current or the voltage, the capacity of the battery module, and the parameter related to the capacity can be further determined on the basis thereof. The capacity of the battery module is defined, for example, as the number of ampere hours required for complete discharge under preset conditions (e.g., determination of temperature, discharge rate).
In addition, the temperature measurement/setting module 25 provides a suitable controlled temperature environment for the battery module 100, so that the battery module 100 to be tested is placed under different temperature conditions in different testing links (e.g., operation preparation phase, initialization phase, and cyclic charge and discharge phase). The temperature measurement/setting module 25 is also used to monitor the heat generation of the battery module 100 during charging and discharging, for example. The temperature measuring/setting module 25 can be designed here in particular as a heating cabinet with a temperature sensor or other suitable heating or cooling device.
The individual test components of the acquisition unit 20 are connected to the analysis unit 30 in order to feed the real-time measurement results centrally back to the analysis unit 30 and to carry out corresponding calculations and analysis processes there. The analysis unit 30 is configured, for example, as a processor and is used to perform trend analysis on the parameters obtained cumulatively over a plurality of test cycles to draw conclusions about the state of health of the battery module 100. Here, based on the relationship between the expansion force applied to the battery module 100 and the number of charge/discharge cycles, it is possible to estimate or evaluate the state of health of the battery module 100 and to make remedial measures as necessary. The analysis unit 30 is connected to a cloud or other terminal device, for example, so that reference can be provided for the usage of the power battery during the driving of the vehicle. Furthermore, analysis unit 30 may also be coupled to one or more simulation models to use the analysis results to calculate more accurate system model parameters.
Fig. 2 illustrates a flowchart of a method for a swelling test of a battery module according to an exemplary embodiment of the present invention. The method exemplarily comprises the steps S01, S02, S1, S2 and may be implemented, for example, using the apparatus 1 shown in fig. 1.
Before the execution of the cyclic charge and discharge operation is formally started, for example, the operation preparation step S01 and the initialization step S02 may be implemented.
In operation preparation step S01, the battery module under test is assembled. For example, a test component for detecting a parameter related to the expansion characteristic is integrated into the battery module to be tested. As an example, a certain number of cells in a partial section, in particular in the middle section, of the battery module can be replaced by a test assembly. For different types of battery modules, in particular, a test assembly can be used instead of a different number of cells.
In the initialization step S02, after the battery module to be tested is assembled, it is necessary to perform a discharging operation on the residual capacity of the battery module and perform a complete charge and discharge cycle on the battery module under preset conditions, so as to determine the actual charge capacity and discharge capacity of the battery module. Due to differences in manufacturing lots, environmental conditions, and the like of the battery modules, the initial capacity of each battery module may deviate from the nominal capacity. In this case, it is advantageous to perform the initial volumetric determination once in an experimental environment (or in an application environment).
Next, in step S1, during the cyclic charge and discharge operations of the battery module over a plurality of test cycles, parameters of the battery module related to the expansion characteristic are acquired, wherein the parameters of the battery module are acquired during the charge and discharge phases and the recovery phases of at least one test cycle, respectively.
Parameters relating to expansion characteristics in the sense of the present invention are not only referred to as "expansion forces" per se, but also include those parameters which are potentially linked to expansion characteristics (e.g. parameters which change as a result of the expansion characteristics, or which influence the expansion characteristics as a result of the manner in which such parameters are applied). Thus, the "expansion characteristic-related parameters" defined herein include, for example, expansion parameters and cycle performance parameters. The expansion parameters include, for example, the expansion force and the expansion rate of the battery module and/or the battery cell, and the frame deformation amount of the battery module, and the cycle performance parameters include, for example, the output voltage, the temperature, the capacity value, and the capacity retention rate of the battery module and/or the battery cell.
Next, in step S2, trend analysis is performed on the parameters obtained cumulatively over a plurality of test periods to draw conclusions about the state of health of the battery modules.
Here, the conclusion about the state of health of the battery module includes: the expansion level of the battery module and/or the cell over a plurality of test cycles; the expansion level of the battery module and/or the battery core influences the cycle performance of the battery module and/or the battery core; the influence of the expansion level of the battery module and/or the battery core on the overall frame structure of the battery module; and the influence of the charging and discharging operation of the battery module on the expansion level of the battery module and/or the battery core. By knowing the state of health of the battery, it is possible to predict the life of the battery module, for example, in combination with the swelling characteristics, and define a new threshold or limit for the capacity retention rate.
Fig. 3 shows a flowchart of a procedure for performing a cyclic charge-discharge operation.
In step 101, the temperature of the test cabinet is adjusted to a preset temperature (e.g., 35 degrees) and the battery module to be tested is left to stand for a certain period of time (e.g., 120 minutes). The battery module has already undergone an initialization phase and therefore requires a certain time for a recovery phase, for example, in order to achieve overvoltage equalization and to eliminate polarization.
In step 102, a suitable charging rate is selected in turn from a plurality of possible charging rates. As an example, the charging rate is selected from 1C, 0.5C, 0.2C, 0.05C, for example. Here, the charge rate is defined as a ratio of a charge current to a rated capacity of the battery module and represents a measure of how fast the battery module is charged, for example, when the battery module having a rated capacity of 1200mAh is charged with a current of 1200mA, the charge rate is 1C, and so on.
In step 103, the battery module is charged in a constant current manner with the selected charging rate.
In particular, this relates to a stepped charging strategy in constant current mode, i.e., the entire charging phase is divided into a plurality of sub-intervals, for example, in accordance with the time or in accordance with the voltage class achieved. The switching of the charging rate occurs upon switching from one subinterval to another. As an example, first, charging of the battery module is performed at a first rate (e.g., 1C) from the lower limit voltage, and when the real-time output voltage is found to reach the first voltage level, the charging rate is switched from the first rate to a second rate (e.g., 0.5C), and so on until all the charging rates are traversed.
In step 104, it is checked whether all charging rates have been traversed.
If this is not the case, then the process returns to step 102 and continues to charge at the next possible charge rate.
If it is found that all charging rates have been traversed, the voltage monitored in real time is compared with the upper limit voltage during the charging performed at the last charging rate, for example, in step 105, and it is determined whether the upper limit voltage is reached.
If the upper limit voltage has not been reached, the charging is continued at the currently selected charging rate (e.g., 0.05C), for example.
If the upper voltage limit has been reached, the charging process should be stopped in order to prevent overcharging damaging the battery, which means that the charging phase has ended. Then, the battery module is subjected to a discharging operation in a constant current manner with the determined discharge rate, for example, in step 106.
In step 107, the real-time monitored output voltage of the battery module is compared with the lower limit voltage, and it is determined whether the lower limit voltage has been reached. If this is not the case, for example, the discharge is continued to be performed at a certain rate.
If the lower voltage limit has been reached, the discharge phase is ended and the recovery phase is entered, for example in step 108. In the recovery phase, neither the charging operation nor the discharging operation is performed on the battery module, but the battery module is in an open state. Typically, such a recovery phase lasts for e.g. 30 minutes in each test cycle, however the duration of the recovery phase may also be lengthened or shortened according to the actual requirements.
In step 109 it is checked whether a loop termination condition has been reached. Here, for example, the examination: whether a predetermined number of cycles have been performed, the number being related to a particular battery type and associated criteria. As another example, it is checked whether the currently measured capacity retention rate has fallen below a certain threshold (e.g., 80%), and if this is the case, it also indicates to some extent that the tested battery module has approached the end stage of its service life.
If the cycle end condition has not been reached, for example, it is possible to return from step 109 to step 102 and start the charge-discharge test of the next cycle.
Conversely, if the cycle end condition has been reached, the cyclic charge and discharge operation may be ended in step 110.
In the flowchart shown in fig. 3, the operation steps of performing the cyclic charge and discharge are shown, and possible intervals of acquiring the parameter associated with the expansion characteristic are also shown in dotted lines. It can be seen that data sampling can be performed not only at a certain sampling frequency during the charge phase and the discharge phase of each test cycle, but also at another sampling frequency during the recovery phase. It is also conceivable to perform sampling for different data types in the charge, discharge and recovery phases, respectively.
Fig. 4 shows a flow chart of the method steps shown in fig. 2. In the exemplary embodiment, method step S02 in FIG. 2 includes, for example, steps S021-S026.
In step S021, after the test battery module is assembled, the temperature of the cabinet is adjusted to 25 degrees and the assembled battery module is left standing for 120 minutes.
In step S022, discharging is performed on the battery modules at, for example, a 1C discharge rate until a lower limit voltage is reached to empty the residual charge in the battery module to be tested. In order to ensure the accuracy of the initial charge capacity determination, a rest recovery period of 30 minutes, for example, is provided after this discharge process to allow the battery module to be sufficiently recovered and then recharged.
In step S023, the battery module is charged at a plurality of charging rates in a constant current manner until the upper limit voltage is reached. Here, for example, the battery modules are charged in the order of 1C +0.5C +0.2C +0.05C while being switched in a stepwise decreasing rate.
In step S024, the initial charging capacity of the battery module is determined, and here, for example, the individual charging capacities of the respective sections may be calculated based on the charging rates and the corresponding charging durations, and finally the charging capacities corresponding to the respective sections are superimposed to obtain the overall charging capacity of the battery module. In order to obtain a sufficiently accurate charge/discharge capacity, for example, a rest recovery phase with a duration of 30 minutes is provided after the end of the charging phase.
In step S025, the battery module is discharged to the lower limit voltage at the determined discharge rate (e.g., 1C).
In step S026, an initial discharge capacity of the battery module is determined. The initial discharge capacity and/or the initial charge capacity thus obtained may be stored as a reference for a subsequent test procedure, for example, instead of the nominal capacity of the battery module.
Fig. 5 a-5 b show the trend of the capacity retention exhibited by square-can battery modules of two electrochemical systems when subjected to the swelling test by means of the method according to the invention.
Fig. 5a shows, for example, a trend of the capacity retention rate of the lithium iron phosphate battery module with time. Here, the capacity retention ratio is understood as a ratio of the available capacity stored in the battery module to the initial capacity under a preset condition (e.g., a certain temperature, humidity, discharge rate). In order to calculate the capacity retention rate, the number of ampere-hours may be obtained, for example, based on the duration when the battery module is completely discharged (discharged to the lower limit voltage) under the preset condition and the discharge current.
As shown in fig. 5a, the capacity retention rate of the battery module gradually decreases as the number of charge and discharge cycles of the battery module increases. In the first few cycles, a brief capacity rise may occur due to incomplete battery modularity, followed by gradual recovery of the test capacity into the normal trend of change.
As can be seen from the observation as a whole, significant swelling and internal deterioration of the battery module did not occur at the early stage of the test, and thus the capacity retention rate was maintained at a high level around 100%. As the swelling of the battery module progresses (e.g., more and more charge and discharge cycles are performed), the capacity retention rate is further decreased.
The trend of the capacity retention rate of the ternary lithium battery module with time is shown in fig. 5 b. When performing swelling tests on lithium iron phosphate battery modules and ternary lithium battery modules by means of the method according to the invention, all operating steps, experimental conditions, data acquisition time periods and acquisition frequencies are set for both battery modules, for example to be identical or similar. As can be seen from comparison of fig. 5a to 5b, the capacity retention rate of the ternary lithium battery module decreases more rapidly than the capacity fading condition of the lithium iron phosphate battery module. In addition, studies have shown that after a certain number of cycles, the lithium iron phosphate battery module is generally less swollen than the ternary lithium battery module, and therefore, from the dimensional analysis of swelling characteristics, a greater swelling degree is highly likely to constitute an important cause of faster capacity decay of the ternary lithium battery module.
Fig. 6 shows the trend of the frame deformation amount of the battery module obtained by the method according to the present invention over time.
Here, two sets of expansion deformation amount curves are exemplarily shown, and the upper curve represents, for example, a change in the amount of longitudinal displacement of the frame detected by means of a first displacement sensor arranged at an end face of the battery module (in the length direction). The lower curve represents, for example, the amount of change in the lateral displacement of the frame detected by means of a second displacement sensor arranged (in the width direction) at the outer side of the housing of the battery module. It can be seen that each displacement variation curve comprises a series of alternating peaks and troughs, each pair of peaks and troughs representing, for example, a charging and discharging process in one test cycle. As the charging progresses, the frame deformation degree of the battery module gradually increases, and the increased size of the outer case of the battery module is shrunk again due to the expansion while the discharging. However, as can be seen by observing the profiles enveloping the valleys and peaks respectively, although the amount of deformation of the frame due to cell expansion shows a tendency to rise first and then fall in each individual test cycle, it still shows an irreversible tendency to increase as a whole. That is, as the number of cycles of charge and discharge increases, the amount of deformation of the frame caused by the battery module also increases, and once the frame elastic limit is exceeded, the battery module can no longer return to the original structural size.
If the upper displacement amount curve and the lower displacement amount curve are observed together, it can be seen that: the battery module expands more in the length direction than in the width direction, and therefore, causes a greater degree of deformation of the frame in the length direction.
It should be noted here that, although the test results of only two displacement sensors are shown in fig. 6 for the sake of simplicity, it is also possible to dispose a greater number of displacement sensors at more locations of the battery module during the actual test and consider the test results of these sensors, for example, in superposition or fusion.
Fig. 7 shows the trend of the internal expansion force of the battery module obtained by means of the method according to the present invention over time.
Similar to the frame deformation variation tendency shown in fig. 6, the internal expansion force of the battery module shown in fig. 7 also includes a plurality of alternately changing peaks and valleys. As a whole, the internal expansion force of the battery module also shows an irreversible increasing tendency. That is to say, along with the increase of the cycle charge and discharge number of times of battery module, the inflation degree of battery module is also more and more obvious, and the inside stress of crescent not only probably arouses frame structure to destroy, but also can lead to electric core to receive the extrusion each other, and then leads to many-sided deterioration such as capacity decay, voltage jump water suddenly.
Although specific embodiments of the invention have been described herein in detail, they have been presented for purposes of illustration only and are not to be construed as limiting the scope of the invention. Various substitutions, alterations, and modifications may be devised without departing from the spirit and scope of the present invention.
Claims (10)
1. A method for swelling testing of a battery module (100), the battery module (100) comprising a plurality of cells, the method comprising the steps of:
s1: acquiring parameters of the battery module (100) related to expansion characteristics during a cyclic charge and discharge operation of the battery module (100) performed over a plurality of test cycles, wherein the parameters of the battery module (100) are acquired during a charge and discharge phase and a recovery phase, respectively, of at least one test cycle; and
s2: performing trend analysis on the parameters obtained cumulatively over a plurality of test periods to draw conclusions about the state of health of the battery module (100).
2. The method according to claim 1, wherein the conclusion about the state of health of the battery module (100) comprises:
the expansion level of the battery module (100) and/or the battery cell over a plurality of test cycles;
the influence of the expansion level of the battery module (100) and/or the cell on the cycle performance of the battery module (100) and/or the cell;
the influence of the expansion level of the battery module (100) and/or the cell on the overall frame structure of the battery module (100); and
the influence of the charging and discharging operations of the battery module (100) on the expansion level of the battery module (100) and/or the cell.
3. The method according to claim 1 or 2, wherein the parameters related to the expansion characteristics comprise expansion parameters and cycle performance parameters, the expansion parameters comprise expansion force of the battery module (100) and/or the battery cell, expansion rate and frame deformation of the battery module (100), and the cycle performance parameters comprise output voltage, temperature, capacity value and capacity retention rate of the battery module (100) and/or the battery cell.
4. The method of any one of claims 1 to 3,
applying different detection schemes to the battery module (100) respectively in a charge-discharge phase and a recovery phase in the at least one test cycle to determine the parameters; and/or
And in a charging and discharging phase and a recovery phase in the at least one test cycle, respectively, sampling the parameters at different sampling frequencies, wherein the sampling frequency applied in the charging and discharging phase is greater than the sampling frequency applied in the recovery phase.
5. The method according to any one of claims 1 to 4, wherein, in each test cycle, the following is performed on the battery module (100):
charging the battery module (100) to an upper limit voltage in a charging stage;
discharging the battery module (100) to a lower limit voltage in a discharging stage;
a recovery phase is provided between the charging phase and the discharging phase and/or after the discharging phase, in which neither a charging operation nor a discharging operation is performed on the battery module (100).
6. The method of any one of claims 1 to 5,
charging the battery module (100) in a constant-current and/or constant-current-constant-voltage manner in a charging phase of each test cycle, and discharging the battery module (100) in a constant-current manner, particularly at a fixed discharge rate, in a discharging phase of each test cycle; and/or
The charging phase of each test cycle is divided into a plurality of sub-intervals, and the charging of the battery module (100) is carried out at different charging rates, in particular at decreasing charging rates, in successive sub-intervals.
7. The method according to one of claims 1 to 6, wherein the method further comprises an operation preparation step before a cyclic charge and discharge operation is carried out, wherein a test assembly for detecting parameters relating to the expansion behavior is integrated into the battery module (100) to be tested, wherein a certain number of cells in a partial section, in particular in a middle section, of the battery module (100) is replaced by the test assembly.
8. The method according to any one of claims 1 to 7, wherein the method further comprises an initialization step before performing the cyclic charge and discharge operation, in which the residual charge of the battery module (100) to be tested is discharged and the initial charge capacity and the initial discharge capacity of the battery module (100) are detected.
9. An apparatus (1) for swelling testing of a battery module (100), the apparatus (1) being for performing the method according to any one of claims 1 to 8, the apparatus (1) comprising:
a charge and discharge unit (10) configured to perform a cyclic charge and discharge operation on the battery module (100) over a plurality of test periods;
a detection unit (20) configured to acquire parameters of the battery module (100) related to expansion characteristics during a cyclic charge and discharge operation performed on the battery module (100), the detection unit (20) being further configured to acquire the parameters of the battery module (100) during a charge and discharge phase and a recovery phase of at least one test cycle, respectively; and
an analysis unit (30) configured to perform a trend analysis on the parameters cumulatively acquired over a plurality of test periods to draw conclusions about the state of health of the battery module (100).
10. A computer program product, wherein the computer program product comprises a computer program for implementing the method according to any one of claims 1 to 8 when executed by a computer.
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| CN202210319672.3A CN114779094A (en) | 2022-03-29 | 2022-03-29 | Method and apparatus for swelling test of battery module |
| DE102023001072.3A DE102023001072A1 (en) | 2022-03-29 | 2023-03-20 | Method and device for testing the expansion of a battery module |
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| CN115356645A (en) * | 2022-10-20 | 2022-11-18 | 苏州琞能能源科技有限公司 | Compression roller detection method and device, electronic equipment and storage medium |
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| CN117872168A (en) * | 2024-03-12 | 2024-04-12 | 苏州市洛肯电子科技有限公司 | Intelligent detection method and system for embedded RFID new energy battery |
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| CN115356645A (en) * | 2022-10-20 | 2022-11-18 | 苏州琞能能源科技有限公司 | Compression roller detection method and device, electronic equipment and storage medium |
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