CN116660768B

CN116660768B - Circulation test method and battery test system

Info

Publication number: CN116660768B
Application number: CN202310954296.XA
Authority: CN
Inventors: 岳锦霞
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2023-08-01
Filing date: 2023-08-01
Publication date: 2024-01-05
Anticipated expiration: 2043-08-01
Also published as: CN116660768A

Abstract

The application discloses a circulation test method and a battery test system, wherein the circulation test method comprises the following steps: charging or discharging at least two batteries arranged in parallel in a plurality of test groups, wherein a state difference exists between the at least two batteries arranged in parallel in each group, and the state difference comprises at least one of a voltage difference between the batteries, a residual electric quantity difference between battery monomers in the interior of the batteries, a temperature difference between the batteries and a health state difference between the batteries; acquiring output data of at least two batteries in each test group, wherein the output data comprises at least one of output current, output voltage and output electric quantity; and comparing the output data of at least two batteries in each group of test groups with preset data to obtain a test result, wherein the test result comprises that the parallel structure of at least two batteries in each group generates circulation or does not generate circulation. By the scheme, the circulation test of the batteries with the parallel structure can be realized.

Description

Circulation test method and battery test system

Technical Field

The present disclosure relates to battery testing, and more particularly, to a circulation testing method and a battery testing system.

Background

With the improvement of living standard, people increasingly start to use various batteries in daily life. For example, a power battery is used as a core component in an electric device such as an electric automobile, the battery is generally tested before leaving the factory, and the battery is sold under the condition that the performance of the battery meets the requirement after the battery is tested. However, the current test for the battery is limited to the test of battery capacity and the like, because the test is carried out for a single battery, a plurality of batteries are used in parallel in many cases in the practical application process, but the batteries can be mutually influenced when being used in parallel, and the power utilization devices such as vehicles and the like are invalid.

Disclosure of Invention

The application provides at least one circulation testing method and a battery testing system.

The application provides a circulation testing method, which comprises the following steps: charging or discharging at least two batteries arranged in parallel in a plurality of test groups, wherein a state difference exists between the at least two batteries arranged in parallel in each group, and the state difference comprises one or more of a voltage difference between the batteries, a residual electric quantity difference between battery monomers in the interior of the batteries, a temperature difference between the batteries and a health state difference between the batteries; acquiring output data of at least two batteries in each test group, wherein the output data comprises one or more of output current, output voltage and output electric quantity; and comparing the output data of at least two batteries in each group of test groups with preset data to obtain a test result, wherein the test result comprises that the parallel structure of at least two batteries in each group generates circulation or does not generate circulation.

In the above scheme, considering that the batteries in many current power utilization devices may be arranged in parallel, the power reserve provided for the power utilization devices is prepared for at least two batteries with state differences during testing, then the at least two batteries arranged in parallel are charged/discharged, and whether the two batteries in the parallel structure generate circulation due to the state differences of the two batteries in the parallel structure can be determined by acquiring the output data of the two batteries in the parallel structure, so that the generation of the circulation is reduced by carrying out targeted optimization on the batteries in the parallel structure according to the reason of generating the circulation, and the stability of the power utilization devices is improved.

In some embodiments, prior to charging or discharging at least two batteries arranged in parallel in the number of test groups, the loop current test method further comprises: respectively adjusting the state differences of at least two batteries which are arranged in parallel in each group, wherein the state differences between at least two batteries which are arranged in parallel in at least part of the groups are different, and each state difference comprises a preset limit state difference; and executing the step of charging or discharging the at least two batteries which are arranged in parallel in the plurality of test groups in response to the state difference between the at least two batteries which are arranged in parallel in each group reaching the corresponding preset state difference of each group.

In the above scheme, the state difference of at least two batteries arranged in parallel in each group is adjusted before the at least two batteries arranged in parallel are charged and discharged, wherein the state difference of the two batteries in at least part of the groups is set to be different, so that the state difference between the batteries and the influence of the generated circulation are conveniently and comprehensively tested, and the influence of the state difference on the circulation is conveniently and subsequently determined. In addition, through adjusting each state difference to limit state difference, through the circulation change of each battery under limit state difference of test, after the battery is optimized to the pertinence based on this test result of convenience follow-up, can improve the stability of power consumption device more in daily use in the follow-up.

In some embodiments, the at least two batteries arranged in parallel in each test set include a first battery and a second battery, and adjusting the difference in state of the at least two batteries arranged in parallel in each set includes at least one of: adjusting a voltage difference between the first battery and the second battery in at least one group to a preset limit voltage difference, wherein the preset limit voltage difference is between 9.5V and 10.5V; the method comprises the steps of adjusting the difference value between the residual electric quantity of one or more battery monomers in at least one group of first batteries and the first average residual electric quantity to be in a first difference value interval, adjusting the residual electric quantity difference value between each battery monomer in a second battery to be in a second difference value interval, wherein the first average residual electric quantity is the average value of the residual electric quantities of each battery monomer in the first battery, the maximum value in the first difference value interval is smaller than the minimum value in the second difference value interval, the first difference value interval is a preset limit difference value interval, and the preset limit difference value interval comprises 3%; adjusting the temperature difference between the first battery and the second battery in at least one group to a preset limit temperature difference interval, wherein the preset limit temperature difference interval comprises delta T which is more than or equal to 5 ℃ and less than or equal to 20 ℃; the ratio between the direct current impedances of the first battery and the second battery in at least one group is adjusted to a preset limit ratio interval, wherein the preset limit ratio interval comprises 1.5, and the health state difference comprises the direct current impedance difference.

In the scheme, the factors which cause circulation generation are roughly determined to be direct current impedance difference and voltage difference between two batteries according to mechanism research, residual electric quantity difference between different battery monomers in a single battery pack, difference between two battery temperatures and the like, in addition, the allowable voltage difference limit between the two battery packs is roughly 9.5V to 10.5V through pre-experimental research, the difference limit between different battery monomers in the single battery is roughly 3%, the temperature difference between different batteries is probably between 5 ℃ and 20 ℃, and the limit of the proportion between the direct current impedance is roughly 1.5, so that the scheme can better reflect the condition that the parallel structure generates circulation of the power utilization device under the limit working condition by adjusting each state difference at the corresponding limit before charging and discharging the batteries which are arranged in parallel.

In some embodiments, the loop test method further comprises, prior to adjusting the difference in state of the at least two batteries of each set of parallel arrangement separately: obtaining detection data of a power utilization device at a parallel structure where at least two batteries in a normal use scene and a historical failure scene are located, wherein the power utilization device is equipment comprising at least two batteries which are arranged in parallel; based on the detection data, counting the state differences between at least two batteries in each scene from each normal use scene and each historical failure scene to obtain a plurality of candidate state differences; respectively adjusting the state difference of at least two batteries arranged in parallel in each group, comprising: and respectively adjusting the state differences of at least two batteries arranged in parallel in each group to be candidate state differences.

In the scheme, the detection data of the parallel structure where at least two batteries are located in a normal use scene and a failure scene of the power utilization device are obtained, then the circulation can be determined in which scenes appear according to the detection data, and the state difference between the two batteries in the parallel structure in each scene is counted, so that the state difference limit between the batteries is conveniently researched, and the state difference between the at least two batteries which are arranged in parallel in the test process is adjusted to be the state difference limit.

In some embodiments, the step of obtaining output data for at least two cells in each test set comprises: obtaining output data of the batteries in each group in a preset period of time after each battery is charged to 100% SOC; or, obtaining output data of the batteries in each group after each battery is discharged to 0% SOC and then standing for a preset period of time.

In the above scheme, considering that the generation time of the circulation is not necessarily in the charging or discharging process, and sometimes the circulation is still in the standing time after the battery is charged or discharged, the method obtains the output data of the battery in more scenes by fully charging and standing or fully discharging and standing, thereby better determining the influence condition of the state difference among the batteries on the circulation.

In some embodiments, the step of charging or discharging at least two batteries disposed in parallel in the number of test groups comprises: and charging at least two batteries which are arranged in parallel with the plurality of groups of test groups according to a preset whole vehicle charging strategy, or discharging at least two batteries which are arranged in parallel with the plurality of groups of test groups according to a WLTC strategy.

In the above scheme, the charging mode may be a whole vehicle charging strategy, and the WLTC discharging strategy is worse than other discharging strategies in discharging working conditions, and at least two batteries arranged in parallel are controlled to charge and discharge under worse working conditions, so that the battery or the parallel structure after optimization according to the test result has better stability under each working condition.

In some embodiments, the output data of at least two batteries in each test set is the sum of the output data of at least two batteries connected in parallel, and the step of comparing the output data of at least two batteries in each test set with preset data to obtain a test result includes: for each test group: in response to the difference between the output data and the preset data being greater than or equal to the preset difference, determining that a parallel structure where at least two batteries in the test set are located generates a circulation; or, in response to the difference between the output data and the preset data being smaller than the preset difference, determining that the parallel structure where at least two batteries in the test set are located does not generate circulation.

In the scheme, whether the circulation current generated by the parallel structure is generated or not is judged by judging the difference condition between the output data of the battery and the preset data. For example, if the battery output data in the parallel structure is over-current, over-voltage or over-discharge, it can be determined that the parallel structure has a circulation.

In some embodiments, the loop test method further comprises: responding to the test result of the test group to generate circulation for the parallel structure where at least two batteries are located, and performing health detection on the at least two batteries in the test group to obtain health detection results of the batteries; based on the health detection result, a degree of influence of a state difference between at least two batteries in the test group on battery health after charging or discharging is determined.

In the scheme, under the condition that the parallel structure generates the circulation, the health detection is carried out on the battery, the influence condition of the circulation on the health of the battery can be determined, and the subsequent targeted optimization of the battery can be facilitated according to the health change of the battery.

In some embodiments, after determining the extent to which a state difference between at least two batteries in a test set affects battery health after charging or discharging based on the health detection result, the loop current test method further comprises: and determining an improvement mode corresponding to the state difference with the influence degree larger than the preset influence degree.

In the above-described scheme, by determining the target manner of improving the factor after determining the influencing factor that causes the circulation of the parallel structure in which the battery is located, the probability of the circulation of the parallel structure in the following can be reduced.

In some embodiments, the circulation testing method is applied to a battery testing system, the battery testing system comprises a charging and discharging machine, at least two incubators and at least two groups of charging channels, each incubator is used for placing a battery to be tested, the charging channels of each group are arranged in parallel, and each charging channel of each group is connected with the battery in one incubator; the step of charging or discharging at least two batteries arranged in parallel in the plurality of test groups comprises the following steps: and controlling the charging and discharging motor to charge or discharge at least two batteries which are arranged in parallel in the plurality of test groups.

In the scheme, the two temperature boxes are arranged in the battery test system, and the two batteries are connected in parallel through the two groups of charging channels, so that the setting condition of the parallel structure in the power utilization device is simulated.

The application provides a battery test system, comprising: the device comprises a controller, a charging and discharging machine, a data detection part, at least two incubators and at least two groups of charging channels, wherein each incubator is respectively used for placing a battery to be tested, the charging channels of each group are connected in parallel, and each group of charging channels is respectively connected with the charging and discharging machine and the battery in one incubator; the controller is connected with the charge-discharge machine and is arranged to control the charge-discharge machine to charge or discharge at least two batteries which are arranged in parallel in a plurality of test groups, and state differences exist between the at least two batteries which are arranged in parallel in each group, wherein the state differences comprise one or more of voltage differences among the batteries, residual electric quantity differences among battery monomers in the batteries, temperature differences among the batteries and health state differences among the batteries; the data detection part is respectively connected with the output ends of the batteries and the controller, the controller is configured to control the data detection part to acquire output data of at least two batteries in each group of test groups, the output data comprises one or more of output current, output voltage and output electric quantity, the controller is further used for respectively comparing the output data of the at least two batteries in each group of test groups with preset data to obtain a test result, and the test result comprises that the parallel structure of the at least two batteries in each group generates circulation or does not generate circulation.

In some embodiments, the battery testing system further comprises a thermal management system coupled to the controller and the battery in the incubator, respectively, the controller configured to adjust a temperature of a thermal management medium in the thermal management system, the thermal management medium being for heat exchange with the battery.

In the scheme, the thermal management system is arranged in the test system, so that the use scene of the battery in the power utilization device can be conveniently and better simulated or the test temperature of the battery can be conveniently and well controlled.

In some embodiments, the thermal management system includes a water cooler connected to the thermal management line and to the thermal management line, the water cooler further connected to a controller for controlling an output temperature of the water cooler, the thermal management line connected to the battery, and the thermal management medium in the thermal management line in thermal communication with the battery.

In the scheme, the water cooling machine is arranged, so that the controller can conveniently control the water cooling machine to adjust the temperature of the thermal management medium.

In some embodiments, a controller is coupled to the incubator, the controller configured to control the incubator to regulate the temperature within the incubator.

In the scheme, the controller is connected with the incubator, so that the environment temperature in the incubator can be conveniently adjusted, and the testing condition of the battery under low-temperature or high-temperature environment temperature and other environment temperatures can be simulated.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and, together with the description, serve to explain the technical aspects of the application.

FIG. 1 is a schematic diagram of a battery testing system provided in some embodiments of the present application;

FIG. 2 is a flow chart of a loop test method provided in some embodiments of the present application;

fig. 3 is another flow chart of a loop test method according to some embodiments of the present disclosure.

Reference numerals:

battery test system 1, battery 2, controller 10, charge-discharge machine 20, data detection member 30, incubator 40, charging channel 50, thermal management system 60, water cooling machine 61, thermal management pipeline 62.

Detailed Description

The following describes the embodiments of the present application in detail with reference to the drawings.

In the following description, for purposes of explanation and not limitation, specific details are set forth such as the particular sub-system architecture, interfaces, techniques, etc., in order to provide a thorough understanding of the present application.

The term "and/or" is herein merely an association relationship describing an associated object, meaning that there may be three relationships, e.g., a and/or B, may represent: a exists alone, A and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship. Further, "a plurality" herein means two or more than two. In addition, the term "at least one" herein means any one of a plurality or any combination of at least two of a plurality, for example, including at least one of A, B, C, and may mean including any one or more elements selected from the group consisting of A, B and C.

However, the current test for the battery is limited to the test of battery capacity and the like, because the test is carried out for a single battery, a plurality of batteries are used in parallel in many cases in the practical application process, but the batteries can be mutually influenced when being used in parallel, and the power utilization devices such as vehicles and the like are invalid.

The circulation testing method disclosed by the embodiment of the application can be applied to a battery testing system. The at least two batteries arranged in parallel may be applied to an electric device using the batteries as a power source or various energy storage systems using the batteries as energy storage elements. The electrical device may be, but is not limited to, an electric car, an electric toy, an electric tool, a battery car, a ship, a spacecraft, etc. Among them, the electric toy may include fixed or mobile electric toys, such as game machines, electric car toys, electric ship toys, electric plane toys, and the like, and the spacecraft may include planes, rockets, space planes, and spacecraft, and the like.

The battery may be a battery cell, a battery module, or a battery module. The battery cell may be a secondary battery or a primary battery; but not limited to, lithium sulfur batteries, sodium ion batteries, or magnesium ion batteries. The battery cells may be cylindrical, flat, rectangular, or otherwise shaped. The battery cell refers to the smallest unit constituting the battery. For example, the battery cell may include end caps, a housing, an electrode assembly, and other functional components. The end cap refers to a member that is covered at the opening of the case to isolate the inner environment of the battery cell from the outer environment. The case is an assembly for mating with the end cap to form an internal environment of the battery cell, wherein the formed internal environment may be used to house the electrode assembly, electrolyte, and other components. The electrode assembly is a component in which electrochemical reactions occur in the battery cells. The electrode assembly is mainly formed by winding or stacking a positive electrode sheet and a negative electrode sheet, and a separator is generally provided between the positive electrode sheet and the negative electrode sheet. The end of the battery cell can be a current input end or an output end, for example, the end of the battery cell can be the end where the end cover is positioned.

The plurality of battery cells can be connected in series or in parallel or in series-parallel connection, and the series-parallel connection refers to that the plurality of battery cells are connected in series or in parallel. The plurality of battery monomers can be directly connected in series or in parallel or in series-parallel connection, and the formed whole forms a battery module; of course, the battery can also be in a form of a battery module formed by connecting a plurality of battery monomers in series or in parallel or in series-parallel connection, and then connecting a plurality of battery modules in series or in parallel or in series-parallel connection to form a whole, wherein the whole is the battery module.

As shown in fig. 1, an embodiment of the present application provides a battery test system 1, including: a controller 10, a charge and discharge machine 20, a data detection member 30, at least two incubators 40, and at least two sets of charging channels 50. Each temperature box 40 is used for placing the battery 2 to be tested, each group of charging channels 50 are arranged in parallel, and each group of charging channels 50 is respectively connected with the charging and discharging machine 20 and the battery 2 in one temperature box 40. The controller 10 is connected to the charge/discharge machine 20, and the controller 10 is configured to control the charge/discharge machine 20 to charge or discharge at least two batteries 2 arranged in parallel in a plurality of test groups, and there is a state difference between the at least two batteries 2 arranged in parallel in each group. The state difference includes one or more of a voltage difference between the batteries 2, a residual amount difference between the battery cells inside the batteries 2, a temperature difference between the batteries 2, and a health state difference between the batteries 2. The data detecting member 30 is connected to the output terminal of each battery 2 and the controller 10, respectively, and the controller 10 is configured to control the data detecting member 30 to acquire output data of at least two batteries 2 in each test group. The output data includes one or more of an output current, an output voltage, and an output power. The controller 10 is further configured to compare output data of at least two batteries 2 in each test group with preset data to obtain a test result, where the test result includes that a parallel structure where at least two batteries 2 in each group are located generates a circulating current or does not generate a circulating current.

The controller 10 may be a control circuit or a control chip such as a CPU. The controller 10 may be provided in a device such as a computer or may be independent of a device such as a computer. The charge and discharge machine 20 may charge and/or discharge the battery 2. The data detecting means 30 may be a device such as an ammeter, a voltmeter, a power detecting means, etc. that can be used to detect the current, voltage, and power outputted from the battery 2. The controller 10 may be coupled to the incubator 40, the controller 10 being configured to control the incubator 40 to regulate the temperature within the incubator 40. The incubator 40 may be understood as a case body with a heat preservation function, and is capable of isolating the temperature inside and outside the case body, so that the ambient temperature outside the incubator 40 and the ambient temperature inside the incubator 40 are independent, wherein the temperature inside the incubator 40 can be controlled to simulate the working condition of the battery 2 at a high temperature or a low temperature, for example, the temperature inside the incubator 40 can be controlled to perform a circulation test on the battery 2 at-20 ℃, and the temperature inside the incubator 40 can be controlled to perform a circulation test on the battery 2 at 0 ℃. Each incubator 40 is capable of accommodating at least one battery 2. The charging path 50 is connected to the battery 2 in the charge/discharge machine 20 and the incubator 40, respectively, for charging or discharging the battery 2 connected thereto. Optionally, the charging channel 50 is a high voltage line. In some application scenarios, the controller 10 controls the charge/discharge machine 20 to charge each battery 2 in the battery test system 1, and in other application scenarios, the controller 10 controls the charge/discharge machine 20 to discharge each battery 2 in the battery test system 1.

The voltage difference between the batteries 2 may be understood as an initial voltage difference of each battery 2, and the voltage difference of the batteries 2 may be caused by a difference in the remaining capacity between the batteries 2, that is, the voltage difference between the batteries 2 may be understood as a difference in the remaining capacity between the batteries 2, that is, an SOC difference. In some application scenarios, each battery 2 includes a plurality of battery cells, and for one battery 2, the remaining power of each battery cell in the battery 2 is generally the same, but the remaining power of each battery cell may be different due to an error generated in the production process of each battery 2, and the like, so that the difference of the remaining power of each battery cell in each battery 2, that is, the difference of the remaining power of different battery cells in a single battery 2, that is, the difference of the SOC of each battery cell in the single battery 2. The temperature difference between the batteries 2 may be due to the difference in the heat generated by the batteries 2 themselves and the like, which may cause the temperature of the batteries 2 to be different at the same time. The difference in health status between the batteries 2 may specifically be a difference in dc impedance and a difference in capacity between the batteries 2, and may cause a difference in dc impedance of the batteries 2 due to a difference in aging conditions of the batteries 2 during use of the batteries 2. Therefore, it is necessary to combine these state differences at the time of the test, and to perform the loop test on the battery 2. The output data of the batteries 2 may be the respective output data of each battery 2 or the sum of the output data of each battery 2, that is, the data of the main path connected to the output terminal of each battery 2. The preset data may be data that does not generate a circulation or data that generates a circulation, and in some application scenarios, the preset data is data that does not generate a circulation, and the controller 10 is further configured to compare the output data of at least two batteries 2 in each test set with the preset data, respectively, and determine that a circulation may have occurred if the difference is large, and determine that a circulation does not occur if the difference is small. In some application scenarios, the preset data is data for generating a circulation, if the comparison result is that the difference between the output data of the battery 2 and the preset data is large, it is determined that the circulation does not occur, and if the difference is small, it is determined that the circulation occurs, and the specific comparison mode is not specifically limited herein.

In other embodiments, the battery testing system 1 further includes a thermal management system 60, the thermal management system 60 being coupled to the controller 10 and the battery 2 in the incubator 40, respectively, and the thermal management system 60. The controller 10 is configured to adjust the temperature of the thermal management medium in the thermal management system 60, which is used to exchange heat with the battery 2.

The thermal management system 60 may be a system having a heat exchange function with the battery 2. The thermal management medium may be water or other medium with a heat conducting function.

In the above scheme, by arranging the thermal management system 60 in the battery test system 1, the use situation of the battery 2 in the power utilization device can be conveniently and better simulated or the test temperature of the battery 2 can be controlled.

In some embodiments, the thermal management system 60 may include a thermal management line 62 and a water cooler 61 connected to the thermal management line 62, where the water cooler 61 is further connected to the controller 10, and the controller 10 is configured to control the output temperature of the water cooler 61 in the thermal management system 60 so as to adjust the output temperature of the thermal management medium in the thermal management line 62, where the thermal management line 62 is connected to the battery 2, and where the thermal management medium in the thermal management line 62 exchanges heat with the battery 2, so as to raise or lower the temperature of each battery 2 to a specific temperature.

In the above-mentioned scheme, by providing the water cooler 61, the controller 10 can conveniently control the water cooler 61 to adjust the temperature of the thermal management medium.

In some embodiments, the controller 10 is coupled to the incubator 40, the controller 10 being configured to control the incubator 40 to regulate the temperature within the incubator 40.

The temperature box 40 has a temperature adjusting function, and the controller 10 can control the temperature box 40 to adjust the internal temperature thereof, and can simulate the working condition that the environmental temperature where the power utilization device or the battery is located is high temperature or low temperature.

In other embodiments, the difference in DC impedance of the battery 2 in the different temperature chambers 40 may be achieved by a resistor (not shown) in series with the battery 2 across the charging path 50.

Referring to fig. 2, the loop current testing method provided in the present application may be applied to the above-mentioned battery testing system. The loop test method may include the following contents of steps S11 to S13. Step S11: and charging or discharging at least two batteries which are arranged in parallel in a plurality of test groups, wherein a state difference exists between the at least two batteries which are arranged in parallel in each group. The state difference includes one or more of a voltage difference between the batteries, a remaining amount difference between the battery cells in the interior of the batteries, a temperature difference between the batteries, and a health state difference between the batteries. Step S12: output data of at least two batteries in each test group are obtained. The output data includes one or more of an output current, an output voltage, and an output power. Step S13: and comparing the output data of at least two batteries in each test group with preset data to obtain a test result. The test results include that the parallel structure where at least two cells in each group are located generates a circulating current or does not generate a circulating current.

Several test sets refer to one or more sets. The voltage difference between the batteries may be understood as an initial voltage difference of each battery, which may be caused by a difference in the remaining capacity between the batteries, that is, the voltage difference between the batteries may be understood as a difference in the remaining capacity between the batteries, that is, an SOC difference. In some application scenarios, each battery includes a plurality of battery cells, and for one battery, the residual electric quantity of each battery cell in the battery is generally the same, but the residual electric quantity of each battery cell may be different due to the reasons such as errors generated in the production process of each battery, etc., and the residual electric quantity difference between each battery cell in each battery, that is, the residual electric quantity difference between different battery cells in a single battery, that is, the SOC difference between each battery cell in a single battery. The temperature difference between the batteries may be due to the difference in heat generated from the batteries themselves and the like, which may cause the temperature of the batteries to be different at the same time. The difference in health status between the batteries may specifically be a difference in dc impedance and a difference in capacity between the batteries, and in the use process of the batteries, the aging condition of the batteries may occur, which may cause the dc impedance of the batteries to be different. Therefore, it is necessary to combine these state differences and perform a loop test on the battery during the test. The output data of the batteries may be the respective output data of each battery or the sum of the output data of each battery, that is, the data of the main circuit connected to the output terminal of each battery. The preset data may be circulation data or circulation data, in some application scenarios, the preset data is circulation data, the controller is further configured to compare output data of at least two batteries in each test set with the preset data, determine that circulation may occur if the difference is large, and determine that circulation does not occur if the difference is small. In some application scenarios, the preset data is data for generating a circulation, if the comparison result is that the difference between the battery output data and the preset data is large, the circulation is determined not to occur, if the difference is small, the circulation is determined to occur, and the specific comparison mode is not specifically limited. Alternatively, the state differences may be tested separately by a test method of the controlled variable method.

In some embodiments, the circulation testing method is applied to a battery testing system, and the battery testing system comprises a charging and discharging motor, at least two incubators and at least two groups of charging channels, wherein each incubator is respectively used for placing a battery to be tested, the charging channels of each group are arranged in parallel, and each charging channel of each group is connected with the battery in one incubator. The above-mentioned manner of charging or discharging at least two batteries arranged in parallel in a plurality of test groups may be: and controlling the charging and discharging motor to charge or discharge at least two batteries which are arranged in parallel in the plurality of test groups.

The specific structure of the battery test system may refer to the above-mentioned embodiment of the battery test system, and will not be described herein.

In some embodiments, prior to charging or discharging at least two batteries disposed in parallel in the number of test groups, the method further comprises: and respectively adjusting the state difference of at least two batteries arranged in parallel in each group. The state differences between at least two batteries arranged in parallel in at least part of the groups are different, and each state difference comprises a preset limit state difference. And executing the step of charging or discharging the at least two batteries which are arranged in parallel in the plurality of test groups in response to the state difference between the at least two batteries which are arranged in parallel in each group reaching the corresponding preset state difference of each group.

When the test sets are multiple sets, the state difference between the batteries in the different sets is different. For example, after each battery is placed in the incubator, the voltage difference between each battery and the residual electric quantity difference between different battery cells in a single battery can be adjusted by a charging and discharging machine in the battery test system, the temperature difference between each battery can be adjusted by a thermal management system in the battery test system, and the direct current impedance difference between each battery can be adjusted by a series resistance with one of the batteries. After the state difference between the batteries reaches the preset state difference corresponding to each group, each battery can be charged or discharged. The preset state difference is exemplified by that the temperature difference between the two batteries is 20 ℃, and when the temperature difference between the two batteries is detected to reach 20 ℃, the state difference between at least two batteries arranged in parallel in the group is determined to reach the corresponding preset state difference of the group. The limit state difference can be understood as the limit that can be reached by counting the state difference, for example, the limit interval of the temperature difference between the batteries is 5 ℃ to 25 ℃ by counting experimental data and market end data, the statistical structure can cover 95% of the total data, that is, the temperature difference between the batteries can be outside 5 ℃ to 25 ℃ in the statistical data rarely.

In the above scheme, the state difference of at least two batteries arranged in parallel in each group is adjusted before the at least two batteries arranged in parallel are charged and discharged, wherein the state difference of the two batteries in at least part of the groups is set to be different, so that the state difference between the batteries and the influence of the generated circulation are conveniently and comprehensively tested, and the influence of the state difference on the circulation is conveniently and subsequently determined.

The at least two batteries arranged in parallel in each test set include a first battery and a second battery, and of course, may include at least one other battery in addition to the first battery and the second battery, and the number of batteries in each test set is not particularly limited herein. The manner of adjusting the state difference between at least two cells arranged in parallel may include one or more of the steps described above for each test set. For example, for the a test group, the voltage difference between the first battery and the second battery in the group may be adjusted to a preset limit voltage difference, and the difference between the remaining amount of one battery cell in the first battery and the first average remaining amount may be adjusted to 3%. In other embodiments, the maximum value of the difference between the remaining amounts of the battery cells in the first battery is 3%, and for example, one of the battery cells has a remaining amount of 30% soc and the first average remaining amount of 27% soc, the difference between the remaining amounts of the two battery cells is 3% soc. A maximum value in the first difference interval being smaller than a minimum value in the second difference interval may be understood as the first difference interval and the second difference interval not having an intersection. The health status differences include direct current impedance differences, and may also include battery capacity differences in other embodiments. The adjusting of the ratio between the dc impedances (DCR) of the two cells in the at least one group to the preset limit ratio interval may be adjusting the ratio between the dc impedances of the two cells in the at least one group to 1.5, i.e. the dc impedance of one cell is the initial dc impedance and the dc impedance of the other cell is 1.5 times the initial dc impedance.

In some embodiments, prior to performing the step of adjusting the state differences of the at least two batteries of each set of parallel settings, respectively, the loop current test method further comprises: and obtaining detection data of the power utilization device at the parallel structure where at least two batteries are located in a normal use scene and a historical failure scene. The electricity consuming device is a device comprising at least two batteries arranged in parallel. Based on the detection data, counting the state differences between at least two batteries in each scene from each normal use scene and each historical failure scene to obtain a plurality of candidate state differences. The above manner of adjusting the state difference of at least two batteries respectively arranged in parallel in each group may be: and respectively adjusting the state differences of at least two batteries arranged in parallel in each group to be candidate state differences.

The normal use scene of the electric device can be understood as a scene that the electric device is in a normal interval of the use data, and the electric device can work normally. The failure scene of the electric device is a scene that the electric device cannot work normally, such as a scene that a vehicle cannot be started. The detection data acquisition position is the same as the detection position of the output data in step S12, and may be, for example, the output end of a single battery or the main path to which the output sides of the respective batteries are connected. Specifically, a range where voltage differences between the batteries in the parallel structure are located in a normal use scene and a failure scene can be obtained, and the voltage differences in the range where the voltage differences are located can be used as voltage differences between two batteries in a circulation test to carry out the circulation test. By way of example, by counting the voltages between the batteries in the normal use scenario and the failure scenario, the range of the voltage difference is 0V to 10V, and then any voltage difference from 0V to 10V can be used as the voltage difference between the two batteries in the loop test. And in the same way, under the normal use scene and the failure scene, the temperature difference range where the temperature difference between the batteries in the parallel structure is located, the range where the health state difference is located and the range where the residual electric quantity difference of each battery monomer under a single battery are located can be obtained. The data in each range is then used as candidate state differences, such as candidate voltage differences between batteries, candidate temperature differences, candidate state of health differences, and candidate residual charge differences between different cells within a single battery. And then testing each battery according to each candidate state difference. Of course, in addition to analysis using normal use scenarios and failure scenarios in the powered device, candidate state differences for testing the battery may also be determined by laboratory experiments.

In other embodiments, by analyzing the normal usage scenario, failure scenario, etc. of the power device, the determined circulation typical test conditions may include a full charge and rest condition, a full discharge and rest condition, and a power change process condition. I.e. in these three typical scenarios the probability of occurrence of circulation is high. Under the working condition of full charge and static state, the charging working condition is a whole vehicle charging strategy, and the limit state difference between the batteries comprises: 1.5% < SOC difference in the bag (difference of residual electric quantity among battery monomers in a single battery) < 3%,5 ℃ < temperature difference < 20 ℃, and DCR difference corresponding to SOH difference is less than or equal to 1.5R0 (R0 is DCR of an initial state sample), wherein the voltage difference is 10V or the pressure difference between branches is the maximum pressure difference allowed by the whole vehicle strategy. Under the full-discharge and static working conditions, the discharge working conditions are WLTC, and the limit state difference comprises: 1.5% < SOC difference in the bag < 3%, temperature difference < 20 ℃ at 5 ℃, DCR difference corresponding to SOH difference (health state difference) is less than or equal to 1.5R0 (R0 is DCR of initial state sample), voltage difference is 10V or pressure difference between branches is the maximum pressure difference allowed by whole vehicle strategy. In the power conversion process, the pressure difference between the branches in the full charge state is the maximum pressure difference allowed by the whole vehicle strategy, and the SOC difference in the bag is less than 1.5 percent and less than 3 percent.

In some embodiments, the step S12 may include the following steps: and obtaining output data of the batteries in each group in a preset period of time after each battery is charged to 100% SOC. Or, obtaining output data of the batteries in each group after each battery is discharged to 0% SOC and then standing for a preset period of time.

If each battery is charged in step S11, step S12 may include obtaining output data of the battery in each group after each battery is charged to 100% soc and then the battery is left for a preset period of time. If each battery is discharged in step S11, step S12 may include: and obtaining output data of the batteries in each group in a preset period of time after each battery is discharged to 0% SOC. Standing refers to charging the battery without using a charging and discharging motor in the battery test system, and discharging the battery without using the charging and discharging motor in the battery test system. The preset time period may be, for example, half an hour or more, and the setting of the preset time period is not particularly limited herein. In other embodiments, step S12 may include output data during charging or discharging of the battery, depending on whether the battery is charged or discharged in step S11.

In some embodiments, the above manner of charging or discharging at least two batteries arranged in parallel in several test groups may be: and charging at least two batteries which are arranged in parallel with a plurality of groups of test groups according to a preset whole vehicle charging strategy. Or discharging at least two batteries which are arranged in parallel with a plurality of groups of test groups according to the WLTC strategy.

For example, there are many charging strategies for the current vehicle, and a specific preset overall charging strategy may be selected from a plurality of charging strategies, which are not specifically limited herein. There are many discharge strategies at present, but WLTC strategies work worse than others, although other discharge strategies, such as CLTC strategies, etc., may be used in other embodiments.

In some embodiments, the output data of at least two cells in each test set is the sum of the output data of at least two cells in parallel. The above-mentioned way of comparing the output data of at least two batteries in each test group with preset data to obtain test results may be: for each test group: and determining that the parallel structure of at least two batteries in the test group generates circulation in response to the difference between the output data and the preset data being greater than or equal to the preset difference. Or, in response to the difference between the output data and the preset data being smaller than the preset difference, determining that the parallel structure where at least two batteries in the test set are located does not generate circulation.

For example, the preset data is a current in a circulating current scene, if the difference between the current output by the parallel structure and the current in the circulating current scene is small, the parallel structure can be considered to generate a circulating current, and conversely, the parallel structure does not generate a circulating current. The existence of a loop current in the parallel structure is specifically understood to mean that the voltages at the output ends of two batteries are different, so that the current at the output end of one battery flows to the output end of the other battery, and the battery is charged, that is, one battery is in a discharging state, and the other battery is in a charging state. In other embodiments, the preset data is a voltage under the loop scene, and if the difference between the voltage output by the parallel structure and the voltage under the loop scene is small, the parallel structure can be considered to generate the loop, and conversely, the parallel structure does not generate the loop. The existence of a loop current in the parallel structure is understood to mean in particular that the voltages at the output terminals of the two batteries differ, so that the current at the output terminal of one battery flows to the output terminal of the other battery and charges the battery, i.e. the one battery is in a discharged state. In other embodiments, the preset data is an electric quantity, and if overdischarge occurs, the parallel structure can be considered to have a circulation.

In some embodiments, referring to fig. 3, the loop test method further includes: step S14: and responding to the test result of the test group to generate circulation for the parallel structure where the at least two batteries are located, and performing health detection on the at least two batteries in the test group to obtain the health detection result of each battery. Step S15: based on the health detection result, a degree of influence of a state difference between at least two batteries in the test group on battery health after charging or discharging is determined.

The health detection mode may include: whether the insulation voltage resistance meets the requirement or not is detected, whether the BMS communication and sampling functions are normal or not, each module or module in the battery, high-voltage connection and the like are not worn and loosened, and whether the battery is subjected to lithium precipitation or copper precipitation or not is judged through CT and battery cell disassembly. If the state difference between the batteries in the test set is that the temperature difference exists between the two batteries, the temperature difference causes circulation of the parallel structure in the charge and discharge or standing process, and the circulation also causes abnormal functions or performances of the batteries, the influence degree of the temperature difference in the test on the health of the batteries is determined to be larger.

In an exemplary embodiment, if the state difference between the batteries in the test set is a temperature difference between at least two batteries, the temperature difference causes a circulation current in the parallel structure during the charging and discharging or standing process, and the circulation current also causes abnormal functions or performances of the batteries, it is determined that the tested temperature difference has a greater influence on the health of the batteries, and then the thermal management strategy of the batteries can be adjusted to stabilize the temperature difference between the batteries, and reduce the generation of the circulation current in the parallel structure, so as to realize the performance stabilization of the electric device. For example, if the state difference between at least two batteries in the test set is 10V, and the voltage difference causes a circulation current in the parallel structure during the charging and discharging or standing process, and the circulation current also causes abnormal functions or performances of the batteries, it is determined that the tested voltage difference has a large influence on the health of the batteries, and measures can be taken to reduce the voltage difference between the batteries so as to reduce the generation of the circulation current in the parallel structure, so as to realize the performance stability of the electric device. The specific voltage difference reducing mode is to disconnect the branch where the smaller voltage is located and charge and discharge the battery with the larger voltage to reduce the voltage, so as to realize the effect of reducing the voltage difference between the batteries.

In some embodiments, a typical market-end practical application working condition is found by combining forward application scene analysis and reverse failure cases, and a standard test method is formed by extracting a test key factor and a judgment standard by combining mechanism research.

By way of example, the full scene of the battery is analyzed, such as battery manufacturing, packaging transportation, whole vehicle manufacturing, customer usage, maintenance and repair, recycling, accident data in failure, etc., and it is determined that the application scene of the battery mainly includes a charging scene, a driving scene, a parking scene, etc., and the failure scene mainly includes charging overvoltage, driving overcurrent, etc., so that during testing, the charging scene is simulated by charging the parallel batteries, the discharging scene is simulated by discharging the batteries, and the parking scene is simulated by standing after charging or discharging.

In addition, by conducting a mechanism study on at least two cells of the parallel structure, since the occurrence mechanism i=u/R, the occurrence of the parallel structure circulation is directly due to the voltage difference occurring between the cells of the parallel mode. The voltage difference may occur due to a difference in internal resistance of the battery, a difference in resistance of a battery part, and a change in voltage of the battery, and the several factors that cause the voltage difference to occur may be a change in internal resistance or voltage due to an initial difference, a difference in aging process of the battery cells, or a difference in temperature of the battery. The difference in internal resistance of the batteries may be caused by different polarization degrees, and the SOH, capacity, voltage after full charge and standing, and/or current actually participating in electrochemical reaction of the batteries during the lifetime (during charge and discharge) may be caused by different polarization degrees.

Specifically, through mechanism research, the influence factors of the branch voltage difference can be caused, and the influence factors mainly comprise the voltage difference and the branch resistance difference. The static pressure difference and the dynamic pressure difference are subdivided under the voltage difference. The static pressure differential, in turn, mainly includes the inter-cell voltage difference, while the dynamic pressure differential, in turn, may include the DCR difference, the capacity difference, and the SOC difference. As described above, the SOC difference mainly includes the SOC difference between the individual battery cells within the single battery pack and the SOC difference between the batteries. The difference in the branch resistances can also include internal resistance meeting, SOH consistency difference, wire resistance difference, fastener internal resistance difference and branch temperature difference among the battery cells. The difference in the internal resistances of the battery cells may be due to the difference in the internal resistances of the polarization or the ohmic internal resistances, and the difference in the internal resistances of the polarization may be further divided into a difference in charge and discharge circuits, a difference in temperature, and a difference in SOC. The SOH consistency difference is mainly the temperature difference of the battery cells, the DOD interval difference and the charge and discharge working condition difference. The difference in wire resistance may be due to wire resistance and contact internal resistance, the difference in fastener internal resistance may be due to branch bolt internal resistance, the branch temperature difference may be due to initial temperature and process temperature difference between batteries, and the process temperature difference may be due to different battery placement positions or thermal management strategies.

And then, determining the upper limit and the lower limit of each influence factor through market-end big data and internal test data, namely the value interval of each influence factor. For example, initial voltage difference between cells: BMS control strategy is when there is a pressure difference between two batteries: the relay with lower total voltage is disconnected under the condition that the differential pressure is 5-10V. The limiting parameter between the two packets is selected to be 10V, but the SOC corresponding to the same pressure difference is different. For example, when the battery is charged, the voltage difference between the batteries is ensured to be 10V, the initial SOC of one of the batteries can be controlled to be 25%, when the battery is discharged, the initial SOC of one of the batteries is controlled to be 95%, and then the other battery is regulated, so that the voltage difference is regulated to be 10V, the initial SOCs of the batteries of different types are different, and the initial SOCs of the batteries can be determined according to experiments. The market-end data may be the number of occurrences of each voltage difference in the power consumption device, the range of the voltage difference where the occurrence occurs is taken as the upper limit and the lower limit of the initial voltage difference between the batteries, and the range of the voltage difference where the occurrence rate reaches 95% or other ratios can be selected as the upper limit and the lower limit of the initial voltage difference.

SOC difference-SOC difference between different cells within a single battery: the limit pressure difference in the package is between 1% and 3% through market-end big data collection. The SOC difference between different battery cells in a single battery with water cooling in the power utilization device is smaller than the SOC difference between different battery cells in a single battery without water cooling in the power utilization device.

SOC difference-difference between batteries: and determining the SOC difference between the batteries according to the interval of the platform area in the SOC-OCV interval. For example, in the battery of the product A, the first two platform areas are 25% -55% in the charging process, the second 60% -90% in the discharging process, the first two platform areas are 30% -50% in the discharging process, and the second two platform areas are 60% -95% in the discharging process, so that the initial SOC in the charging test can be determined to be 25%, and the initial SOC in the discharging process can be determined to be 95%.

Internal resistance of battery cell: factors affecting the internal polarization resistance: temperature, SOC, charge-discharge current. The research shows that the influence of low temperature and low SOC on the internal resistance is relatively large;

branch SOH consistency differences: the aging of the battery monomer brings about the difference of branch DCR, so as to cause the difference of branch internal resistances; the internal resistances of the battery cells corresponding to the battery cells in different aging paths are different, and factors affecting SOH include use temperature, charge and discharge working conditions and DOD intervals, and according to actual test data: the charge-discharge eol_dcr increase rate of 50% can cover > 95% of the demand, and specifically, sample data statistics attenuated to below 80% soh can be selected.

In addition, the proportion of the line resistance difference to the whole branch resistance difference is small and can be ignored.

Fastener internal resistance difference: the fastener is made of carbon steel, the wire harness is made of copper, the resistivity of the copper is 1.68x10 < -8Ω > m (20 ℃), the resistivity of the carbon steel is about 1.43x10 < -7Ω > m, the resistivity of the copper is far smaller than that of stainless steel, and when current passes through the locking position, the material with small resistivity is selected to pass through, so that the fastener does not participate in overcurrent parts in the charging and discharging processes of the branch, and the internal resistance of the fastener is not considered.

Branch temperature difference: according to market data, the limit temperature difference parameters of the battery pack are as follows: this temperature difference interval can cover 95% of the statistical data from 5 ℃ to 25 ℃.

Typical scenarios of the loop current obtained by the forward full scenario and historical failure scenario analysis described above include 5 large scenarios.

Scene one is driving full-discharge and standing, and the potential failure modes of scene one include: 1. the current flowing through the loop is discharged, the relay is disconnected, high voltage is applied, 2, the current flowing through the loop is prevented from separating copper, smoking, firing and explosion, potential failure results comprise that the whole vehicle cannot normally operate and the long-period reliability of a battery is affected, potential failure causes and mechanisms in a scene comprise shunt of parallel branches due to difference of internal resistances of the branches, the polarization degree of a battery core is affected by the current magnitude of discharge ends, voltages at two ends of the branches are inconsistent, the current flowing through the loop is generated, the risk of over-discharge exists in the branch with high total voltage, deposited metal copper can puncture a diaphragm when flowing through the loop to a certain degree, short circuit occurs between the deposited metal copper and a negative electrode, a local short circuit phenomenon occurs, and the temperature rising and valve opening of a battery monomer are triggered.

The second scenario is to charge by using the charging gun, and charge when the state difference exists between the batteries in the charging process (i.e. the branch line resistance difference, the ohmic internal resistance difference of the battery core, the branch temperature difference, the SOC consistency difference, the SOH difference between the batteries, etc., specifically, the state difference in step S11 may be referred to). The second potential failure mode comprises different charging capacity and energy, the recharging overcurrent relay is disconnected, high voltage is lowered, the recharging overcurrent is used for precipitating lithium, smoking, igniting explosion and the like, the second potential failure result comprises that the whole vehicle cannot normally run, aging is accelerated and the like, and the second potential failure cause and mechanism comprise: the branch DCR is inconsistent in the charging process, so that the branch charging current is inconsistent, a voltage difference is generated, and the circulation problem is caused, so that the branch overcurrent problem is caused.

The third potential failure mode comprises circulation overvoltage, relay disconnection, high-voltage descending, lithium precipitation, ignition, fire, explosion and the like, the third potential failure result comprises that the whole vehicle cannot normally operate and the long-period reliability of a battery is affected, the third potential failure cause and mechanism comprises that shunt branches are connected in parallel due to the difference of internal resistances of branches, the polarization degree of a battery core is affected by the current of the charging tail end, the voltages at two ends of the branches are inconsistent, circulation is generated, the total low branch has the risk of overcharge, and when the circulation is charged to a certain extent, the lithium is severely precipitated by the negative electrode to cause internal short-circuit fire.

The fourth scenario is a driving process, in which driving (branch line resistance difference, ohmic internal resistance difference of the battery core, branch temperature difference, SOC uniformity difference, SOH difference between batteries, etc.) is performed when the state difference between each battery is mainly controlled in the driving process, and the state difference in step S11 may be specifically referred to. The potential failure modes in the fourth scene comprise different discharge capacities and energies, the recharging overcurrent relay is disconnected, the recharging overcurrent relay is powered down to high voltage, the recharging overcurrent is used for precipitating lithium, smoking, igniting and exploding, and the potential failure results of the fourth scene comprise that the whole vehicle cannot normally run, aging is accelerated, and the like. The potential failure cause and mechanism of the fourth scenario comprise the risk of lithium precipitation of the battery core and the branch with large internal resistance due to the fact that the branch current with small resistance is large and the battery core is over-current, and the discharge depth is small, so that capacity and energy are insufficient.

The fifth scenario is a power conversion pairing, wherein, in the power conversion pairing process, the state difference includes that each battery cell voltage in a single battery is inconsistent and voltage between batteries is inconsistent, and the potential failure mode of the fifth scenario includes: the two sets of full charge Pack are matched, the pressure difference between packs is generated, and the circulation causes the risk of overvoltage of a single cell (the upper limit SOC is 98 percent required to be used by customers); pack circulation causes risk of overcurrent. The potential failure results of the fifth scene comprise that a new vehicle cannot be electrified, and the like, and the failure causes and mechanisms in the fifth scene comprise that the pressure difference is good, so that parallel circulation is caused.

In some embodiments, the loop test method provided by the present application may include the following test scenarios. The battery is a battery pack, the electricity utilization device is a vehicle, the charging and discharging depth is the actual depth of the whole vehicle, the charging strategy is the whole vehicle charging strategy, the thermal management is the whole vehicle or product actual strategy, the actual line resistance between the two branches is the whole vehicle actual line resistance, and the discharging working condition is the WLTC strategy.

Among them, the influence factors that may cause the generation of the circulation include the temperature difference between the battery packs, the SOC difference-between the battery packs (differential pressure), the SOC difference-within-single-pack, and the SOH difference (DCR, capacity difference). The limiting working condition parameters of each influence factor comprise: temperature difference: delta T is more than or equal to 5 ℃ and less than or equal to 20 ℃, the SOC difference is 10V or the maximum pressure difference allowed by the whole vehicle strategy is the SOC difference in a single package: the difference of the residual amounts of the battery cells in Pack1 is normal, the difference of 3% between a certain battery cell in Pack2 and the maximum value or the average value (the discharge is 3% different from the minimum value or the average value), the SOH difference (DCR, capacity difference): pack1 is the BOL and Pack2 is the EOL, BOL indicates that the battery is in a healthy state, EOL indicates that the battery is near a dead state, for example, pack1 is the dc impedance is the initial dc impedance, and Pack2 is about 1.5 times the dc impedance. The normal working conditions of the influence factors are that the temperature difference is less than 5 ℃, the pressure difference between parallel branches is 0V, the SOC difference/pressure difference in the bag is basically consistent, and the SOH is basically consistent (the DCR is not more than 1 percent different).

And carrying out DOE experiments according to the limit working condition and the normal working condition of each influence factor, wherein the total number of the DOE experiments is 16. The 16 scenes respectively comprise a first state difference (influencing factor) which is a temperature difference, namely the temperature difference between two batteries is in a limit working condition, and other factors are in a normal working condition; 2. the state difference is the voltage difference between the batteries, namely the pressure difference between the two batteries is the limit working condition, and the other factors are the normal working condition; 3. the state difference is that the residual capacity difference in the single battery pack is the limit working condition, and the other factors are the normal working condition; 4. the state difference is that the health state difference among the batteries is the limit working condition, and the other factors are the normal working condition; other scenarios also include any two influencing factors being extreme conditions, normal conditions of other factors, or any three influencing factors being extreme power, other factors being normal conditions, or all factors being extreme conditions, or all factors being normal conditions.

Taking two charge and discharge scenarios as examples:

scenario one: the influencing factors include the existence of branch voltage difference (voltage difference between batteries) between branches and the difference in SOC in the package (difference in residual charge between each battery cell in a single battery):

a: the batteries stand for 6 hours or reach 25+/-5 ℃ (the relays of the two batteries are in an off state, namely the parallel structure is in an off state);

b: double-packet split-modulation SOC: pack1 was adjusted to 25% soc and Pack2 was charged with 5A to 10±0.5V (static voltage) higher than Pack 1;

c: the balance instrument is used for adjusting the residual electric quantity of a certain battery monomer in the Pack2 to be 3% higher than the average value;

d:25 ℃ heat balance, and charging the double-package parallel connection to 100% SOC according to an actual whole vehicle charging strategy;

e: standing for 2h; (the relay is in a closed state, the data of the upper computers of the two batteries are recorded respectively, namely the output data of each battery is collected), the charging process of the scene is finished, and the situation of testing each influence factor in the discharging process is started from f;

f: standing for 6h or reaching 25+/-5 ℃ (the relay is in an off state);

g: double-packet split-modulation SOC: pack1 was adjusted to 95% soc and Pack2 was discharged with 5A to 10±0.5V (static voltage) lower than Pack 1; the balance instrument is used for adjusting the residual electric quantity of a certain battery monomer in the Pack2 to be 3% lower than the average value;

h:25 ℃ heat balance, discharging to 0% SOC under the working condition of double-package parallel operation WLTC;

i: standing for 2h (the relay is in a closed state, and respectively recording the data of the two battery upper computers);

In addition, the environmental temperature of each battery can be controlled to be minus 20 ℃ and the steps are repeated to finish the test at low temperature.

Scenario two: the influencing factors include: the branch pressure difference, the in-package SOC difference, the SOH difference and the temperature difference (5-20 ℃) exist among the branches:

pack1 is BOL state, pack2 is MOL/EOL state;

a: standing for 6 hours or reaching 25+/-5 ℃ (the relays of the two batteries are in an off state);

d: pack 10 + -2deg.C heat balance, pack 2-20+ -2deg.C heat balance (two battery relays in off state);

e: adjusting the ambient temperature of the two incubators to-20 ℃ (two battery relays are in an off state);

f: the double-pack parallel connection is charged to 100% SOC according to the whole vehicle charging strategy;

g: standing for 2h; (the relay is in a closed state, the data of the upper computers of the two batteries are recorded respectively, namely the output data of each battery is collected), the charging process of the scene is finished, and the situation of testing each influence factor in the discharging process is started from h;

h: standing for 6 hours or reaching 25+/-5 ℃;

i: double-packet split-modulation SOC: pack1 was adjusted to 95% soc and Pack2 was discharged with 5A to 10±0.5V (static voltage) lower than Pack 1;

j: the balance instrument is used for adjusting the residual electric quantity of a certain battery monomer in the Pack2 to be 3% lower than the average value;

k: heat balance of Pack 10 + -2deg.C and heat balance of Pack 2-20 + -2deg.C;

l: the ambient temperature of the two incubators is adjusted to-20 ℃;

m: discharging the WLTC working condition to 0% of SOC in the double-packet parallel operation;

n: standing for 2h (the relay is in a closed state, and recording upper computer data, namely collecting output data of each battery).

Testing of 16 scenarios is completed according to the steps.

Then after the test of each scene is completed, it is checked whether the battery satisfies the following conditions: the insulation voltage resistance meets the requirements, the BMS communication and sampling functions are normal, and the modules, the high-voltage connection and the like are free from abrasion and looseness; and judging whether the battery has lithium or copper precipitation through CT and battery cell disassembly.

In some embodiments, each cell may also be subjected to a battery capacity test and a dc impedance test prior to subjecting the cells to a loop test.

Before testing, detecting an initial state, checking the appearance and the label of a sample (battery), and photographing the sample; setting up a rack; checking voltage, pressure difference and temperature sampling functions; checking the communication function of the sample; and taking pictures by the bench.

Then, capacity tests were performed on the samples of the parallel structure, respectively (two samples were performed, respectively).

a: constant current charging: the flow of capacity test is 25 ℃ heat balance; charging at a current of 1/3C until either monomer reaches an upper limit voltage or a charge termination voltage specified in manufacturer specifications; standing for 5min; charging at a current of 0.05C to any monomer reaching a limit voltage or a charge termination voltage specified in manufacturer specifications; standing for 30min;

b: constant current discharge: discharging at 1/3C until either monomer reaches a lower voltage limit or a discharge termination voltage specified in manufacturer specifications; standing for 30min;

c: cycling a) to b) for 5 times, stopping testing if the discharge capacity of two continuous times is not higher than 3% of the rated capacity, and taking the average value of the last two times as the sample discharge capacity Cn;

the samples of the parallel structure were then separately subjected to direct current impedance (DCR) testing (both samples were separately performed).

a: adjust 50% soc: heat balance at 25 ℃, discharge to 50% soc at 1/3C for full charge sample;

b: the DCR value of the sample was calculated by thermal equilibration at 25℃and discharge at 1C for 30 s.

In the scheme, after the battery pack with the parallel structure passes the loop test, the risk points and the failure points caused by the product loop can be effectively and comprehensively identified, so that the weak points generated by the product loop can be effectively found by adopting the scheme, and the follow-up targeted optimization design is convenient.

Claims

1. A method of loop testing, the method comprising:

charging or discharging at least two batteries arranged in parallel in a plurality of test groups, wherein a state difference exists between the at least two batteries arranged in parallel in each group, and the state difference comprises one or more of a voltage difference between the batteries, a residual electric quantity difference between battery monomers in the interior of the batteries, a temperature difference between the batteries and a health state difference between the batteries;

acquiring output data of at least two batteries in each test group, wherein the output data comprises one or more of output current, output voltage and output electric quantity, and the output data of at least two batteries are output data of each battery or the sum of the output data of each battery;

and comparing the output data of at least two batteries in each group of test groups with preset data to obtain a test result, wherein the test result comprises that the parallel structure of at least two batteries in each group generates circulation or does not generate circulation.

2. The loop current testing method according to claim 1, characterized in that before said charging or discharging at least two batteries arranged in parallel in a number of test groups, the loop current testing method further comprises:

Respectively adjusting state differences of at least two batteries arranged in parallel in each group, wherein the state differences between at least two batteries arranged in parallel in at least part of the groups are different, and each state difference comprises a preset limit state difference;

and responding to the state difference between at least two batteries which are arranged in parallel in each group to reach the corresponding preset state difference of each group, and executing the step of charging or discharging the at least two batteries which are arranged in parallel in the plurality of test groups.

3. The loop current testing method according to claim 2, wherein the at least two batteries arranged in parallel in each test group include a first battery and a second battery, and the adjusting the state difference of the at least two batteries arranged in parallel in each group includes at least one of:

adjusting a voltage difference between the first battery and the second battery in at least one group to a preset limit voltage difference, the preset limit voltage difference being between 9.5V and 10.5V;

adjusting the difference value between the residual electric quantity of one or more battery cells in at least one group of the first battery and the first average residual electric quantity to be in a first difference value interval, adjusting the residual electric quantity difference value between each battery cell in the second battery to be in a second difference value interval, wherein the first average residual electric quantity is the average value of the residual electric quantity of each battery cell in the first battery, the maximum value in the first difference value interval is smaller than the minimum value in the second difference value interval, the first difference value interval is a preset limit difference value interval, and the preset limit difference value interval comprises 3 percent;

Adjusting the temperature difference between the first battery and the second battery in at least one group to a preset limit temperature difference interval, wherein the preset limit temperature difference interval comprises 5 ℃ to 20 ℃;

and adjusting the ratio between the direct current impedances of the first battery and the second battery in at least one group to a preset limit ratio interval, wherein the preset limit ratio interval comprises 1.5, and the health state difference comprises a direct current impedance difference.

4. The circulation test method according to claim 2, characterized in that before the respective adjustment of the difference in the states of the at least two batteries of each group disposed in parallel, the circulation test method further comprises:

obtaining detection data of a power utilization device at a parallel structure where at least two batteries in a normal use scene and a historical failure scene are located, wherein the power utilization device is equipment comprising at least two batteries which are arranged in parallel;

based on the detection data, counting the state differences between at least two batteries in each scene from each normal use scene and historical failure scene to obtain a plurality of candidate state differences;

the adjusting the state difference of at least two batteries arranged in parallel in each group comprises the following steps:

And respectively adjusting the state differences of at least two batteries arranged in parallel in each group to be candidate state differences.

5. The circulation test method according to any one of claims 1 to 4, characterized in that the step of acquiring output data of at least two of the batteries in each test group includes:

obtaining output data of the batteries in each group in a preset period of time after each battery is charged to 100% SOC;

or, obtaining output data of the batteries in each group after each battery is discharged to 0% SOC and then standing for a preset period of time.

6. The circulation test method according to any one of claims 1 to 4, characterized in that said step of charging or discharging at least two batteries arranged in parallel in several test groups comprises:

and charging at least two batteries which are arranged in parallel with the plurality of groups of test groups according to a preset whole vehicle charging strategy, or discharging at least two batteries which are arranged in parallel with the plurality of groups of test groups according to a WLTC strategy.

7. The circulation test method according to any one of claims 1 to 4, wherein the output data of at least two batteries in each test group is the sum of the output data of at least two batteries connected in parallel, and the step of comparing the output data of at least two batteries in each test group with preset data to obtain a test result includes:

For each test group:

determining that a parallel structure where at least two batteries in the test set are located generates a circulating current in response to the difference between the output data and preset data being greater than or equal to the preset difference;

or, in response to the difference between the output data and the preset data being smaller than the preset difference, determining that the parallel structure where at least two batteries in the test set are located does not generate circulation.

8. The loop flow test method of claim 7, wherein the loop flow test method further comprises:

responding to a test result of a test group to generate a circulating current for a parallel structure where at least two batteries are located, and performing health detection on the at least two batteries in the test group to obtain a health detection result of each battery;

based on the health detection result, determining the degree of influence of a state difference between at least two batteries in the test group on battery health after charging or discharging.

9. The circulation test method according to claim 8, characterized in that after said determining, based on the health detection result, the degree of influence of a state difference between at least two batteries in a test group on battery health after charging or discharging, the circulation test method further comprises:

And determining an improvement mode corresponding to the state difference with the influence degree larger than the preset influence degree.

10. The circulation testing method according to any one of claims 1 to 4, wherein the circulation testing method is applied to a battery testing system, the battery testing system comprises a charging and discharging machine, at least two incubators and at least two groups of charging channels, each of the incubators is used for placing a battery to be tested, the charging channels of each group are arranged in parallel, and each group of charging channels is connected with a battery in one of the incubators;

the step of charging or discharging at least two batteries arranged in parallel in the plurality of test groups comprises the following steps:

and controlling the charging and discharging motor to charge or discharge at least two batteries which are arranged in parallel in the plurality of test groups.

11. A battery testing system, comprising: the device comprises a controller, a charging and discharging machine, a data detection part, at least two incubators and at least two groups of charging channels, wherein each incubator is respectively used for placing a battery to be tested, the charging channels of each group are connected in parallel, and each group of charging channels is respectively connected with the charging and discharging machine and the battery in one incubator;

the controller is connected with the charge-discharge machine, and is configured to control the charge-discharge machine to charge or discharge at least two batteries arranged in parallel in a plurality of groups of test groups, wherein a state difference exists between the at least two batteries arranged in parallel in each group, and the state difference comprises one or more of a voltage difference between the batteries, a residual electric quantity difference between battery monomers in the batteries, a temperature difference between the batteries and a health state difference between the batteries;

The data detection part is respectively connected with the output end of each battery and the controller, the controller is configured to control the data detection part to acquire output data of at least two batteries in each test group, the output data comprises one or more of output current, output voltage and output electric quantity, the output data of at least two batteries are respectively output data of each battery or the sum of the output data of each battery, the controller is further used for respectively comparing the output data of at least two batteries in each test group with preset data to obtain a test result, and the test result comprises that the parallel structure of at least two batteries in each test group generates circulation or does not generate circulation.

12. The battery testing system of claim 11, further comprising a thermal management system coupled to the controller and the battery in the incubator, respectively, the controller configured to adjust a temperature of a thermal management medium in the thermal management system, the thermal management medium being configured to exchange heat with the battery.

13. The battery test system of claim 12, wherein the thermal management system includes a water chiller coupled to a thermal management circuit and to the thermal management circuit, the water chiller further coupled to the controller, the controller configured to control an output temperature of the water chiller, the thermal management circuit coupled to the battery, and a thermal management medium in the thermal management circuit in thermal communication with the battery.

14. The battery testing system of any one of claims 11 to 13, wherein the controller is coupled to the incubator, the controller configured to control the incubator to regulate the temperature within the incubator.