Detection method and detection device of DCR and energy storage system

Abstract

The invention provides a DCR detection method and device and an energy storage system, and can effectively detect the DCR of a battery pack, and the detection method comprises the steps: determining the first DCR of the battery pack; and according to a preset calibration coefficient, calibrating the first DCR to obtain a calibrated second DCR of the battery pack. After the DCR of the battery pack is obtained, the DCR of the battery pack is calibrated through a proper calibration coefficient, and the calibration coefficient can improve the inconsistency between the initial DCRs of different battery monomers in the battery pack, so that the accuracy of the DCR is improved.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular, to a method for detecting direct current resistance (DCR), a detection device, and an energy storage system. Background Art

[0002] Energy storage systems usually have requirements such as high voltage and large capacity. For this reason, a large number of batteries are required in the energy storage system to be connected in series and parallel to form products such as electrical cabinets or containers, and energy interaction with the power grid is carried out through a power conversion system (PCS). The battery packs in the energy storage system can be connected in parallel. In the case where the consistency between multiple battery packs is poor, the DCR difference between the battery packs will cause a current difference between the battery packs, resulting in uneven current distribution between the battery packs. On the one hand, the problem of uneven current distribution will cause the entire energy storage system to cut off charge and discharge prematurely, affecting the capacity and power of the entire energy storage system; on the other hand, the battery pack with too large current may exceed the charging capacity window of the battery cell, affecting the safety performance and service life of the battery cell. For this reason, how to effectively detect the DCR of the battery has become an urgent problem to be solved. Summary of the Invention

[0003] Embodiments of the present application provide a method for detecting DCR, a detection device, and an energy storage system, which can effectively detect the DCR of the battery.

[0004] In a first aspect, a method for detecting DCR is provided. The detection method includes: determining a first DCR of a battery pack; calibrating the first DCR according to a preset calibration coefficient to obtain a second DCR of the calibrated battery pack.

[0005] In the embodiments of the present application, after obtaining the DCR of the battery pack, the DCR of the battery pack is calibrated by a suitable calibration coefficient, and this calibration coefficient can improve the inconsistency between the initial DCRs of different battery cells in the battery pack, thus improving the accuracy of the DCR.

[0006] In some possible implementation manners, determining the first DCR of the battery pack includes: obtaining a state parameter group of the battery pack, where the state parameter group includes at least one state parameter of the battery pack; determining the first DCR of the battery pack according to the state parameter group of the battery pack and a corresponding relationship between a plurality of preset state parameter groups and a plurality of DCRs.

[0007] Among them, the state parameter group includes, for example, at least one of the following state parameters: the SOC of the battery pack, the temperature of the battery pack, the current of the battery pack, the charge and discharge direction of the battery pack, the charge and discharge time of the battery pack, and the SOH of the battery pack.

[0008] In this implementation, by establishing a database including the correspondence between the state parameter group of the battery pack and the DCR, the DCR of the battery pack under the current state parameters is determined using this database. The state parameter group includes various state parameters that may affect the DCR of the battery pack. Since the influence of different state parameters on the DCR of the battery pack is comprehensively considered, the accuracy of the DCR can be improved.

[0009] In some possible implementations, determining the first DCR of the battery pack according to the state parameter group of the battery pack and the preset correspondence between multiple state parameter groups and multiple DCRs includes: determining the DCR corresponding to the state parameter group of the battery pack among the multiple DCRs as the first DCR.

[0010] In this implementation, according to the correspondence between multiple state parameter groups and multiple DCRs, the DCR corresponding to the current state parameter group of the battery pack can be selected from the multiple state parameter groups as the first DCR of the battery pack, so as to simply and quickly obtain the first DCR of the battery pack.

[0011] In some possible implementations, the state parameter group includes a first state parameter, and the correspondence includes multiple values of the first state parameter corresponding to the multiple DCRs. Determining the first DCR of the battery pack according to the state parameter group of the battery pack and the preset correspondence between multiple state parameter groups and multiple DCRs includes: determining the first value and the second value that are closest to the parameter value of the first state parameter of the battery pack among the multiple values; determining the DCR corresponding to the first value and the DCR corresponding to the second value according to the first value, the second value, and the correspondence; determining the DCR corresponding to the parameter value of the first state parameter of the battery pack based on the interpolation algorithm according to the DCR corresponding to the first value and the DCR corresponding to the second value; determining the DCR corresponding to the parameter value of the first state parameter of the battery pack as the first DCR.

[0012] In this implementation manner, in the correspondence relationship between multiple state parameter groups and multiple DCRs, if the parameter values of the multiple state parameter groups in this correspondence relationship do not include the parameter value of a certain state parameter in the current state parameter group of the battery pack. For example, the parameter value of the first state parameter in the state parameter group of the battery pack is not equal to the value of the first state parameter in any state parameter group in this correspondence relationship. Then, among the multiple values of the first state parameter in this correspondence relationship, the first value and the second value that are closest to the parameter value of the first state parameter of the battery pack can be found, and the DCRs corresponding to the first value and the second value are determined. Thus, through an interpolation algorithm, the first DCR corresponding to the parameter value of the first state parameter of the battery pack is obtained.

[0013] In some possible implementation manners, the detection method further includes: obtaining the initial DCRs of multiple battery cells in the battery pack; obtaining the initial DCR of a standard battery cell, where the initial DCR of the standard battery cell is tested under the same state parameters as the initial DCRs of the multiple battery cells in the battery pack, and the standard battery cell is the battery cell used to establish this correspondence relationship; determining the calibration coefficient according to the initial DCR of the standard battery cell and the initial DCRs of the multiple battery cells in the battery pack.

[0014] Due to the influence of factors such as the material of the battery cell and the test environment, the initial DCRs of the battery cells have a certain distribution law. Therefore, a DCR test scheme established based on some standard battery cells, such as a DCR database used to establish the above-mentioned correspondence relationship between multiple state parameter groups and multiple DCRs, cannot be accurately applied to the DCR detection of other battery packs. And by using the initial DCR of the standard battery cell and the initial DCRs of the multiple battery cells in the battery pack to determine the calibration coefficient, the calibration coefficient can effectively improve the inconsistency between the initial DCRs of different battery cells in the battery pack, and obtain the second DCR of the calibrated battery pack.

[0015] For example, the calibration coefficient may be equal to the ratio between the mean value of the initial DCRs of the multiple battery cells in the battery pack and the initial DCR of the standard battery cell.

[0016] At this time, in some possible implementation manners, the step of determining the second DCR of the battery pack according to the first DCR and a preset calibration coefficient includes: determining the product of the first DCR and the calibration coefficient as the second DCR. Thus, the first DCR of the battery pack can be simply and quickly calibrated to obtain the calibrated second DCR.

[0017] In some possible implementation manners, the detection method further includes: determining whether there is uneven current sharing among the multiple battery packs according to the second DCR of the multiple parallel-connected battery packs.

[0018] In this implementation manner, when multiple battery packs are connected in parallel to the power grid, since the voltages of the multiple battery packs are the same, based on Ohm's law, the DCR difference among the multiple battery packs will cause a current difference among the battery packs, thus resulting in uneven current sharing among the multiple battery packs, which affects the capacity and power of the battery cluster. Therefore, it is possible to determine whether there is uneven current sharing among the multiple battery packs by detecting the difference between the DCRs of the multiple parallel-connected battery packs, so as to timely discover and prevent uneven current sharing among the parallel-connected battery packs.

[0019] For example, the determining whether there is uneven current sharing among the multiple battery packs according to the second DCR of the multiple parallel-connected battery packs includes: determining that there is uneven current sharing among the multiple battery packs when the ratio between the second DCR of the first battery pack and the second DCR of the second battery pack among the multiple battery packs is greater than a preset DCR threshold, where the first battery pack is the battery pack with the largest second DCR among the multiple battery packs, and the second battery pack is the battery pack with the smallest second DCR among the multiple battery packs.

[0020] In this way, according to the DCR difference between the battery pack with the largest DCR and the battery pack with the smallest DCR among the multiple parallel-connected battery packs, it is possible to timely discover the uneven current sharing situation among the multiple battery packs.

[0021] In some possible implementation manners, the battery pack is a battery cluster or an electric cabinet, the battery cluster or the electric cabinet includes multiple electric boxes connected in series and / or in parallel, and the electric box includes multiple battery cells connected in series and / or in parallel.

[0022] The above-mentioned battery pack may be a battery cluster or an electric cabinet. The battery cluster or the electric cabinet includes multiple electric boxes connected in series and / or in parallel, and each electric box includes multiple battery cells connected in series and / or in parallel. Uneven current sharing may occur among other parallel units in the energy storage system, and the DCRs of these parallel units can also be determined by the DCR detection method of the embodiments of the present application, so as to timely discover and prevent uneven current sharing among these parallel units.

[0023] In a second aspect, a DCR detection device is provided. The detection device includes: a detection module for determining the first DCR of a battery pack; and a calibration module for calibrating the first DCR according to a preset calibration coefficient to obtain the second DCR of the calibrated battery pack.

[0024] In some possible implementation manners, the detection module is specifically configured to obtain a state parameter group of the battery pack, where the state parameter group includes at least one state parameter of the battery pack; and determine a first DCR of the battery pack according to the state parameter group of the battery pack and a preset corresponding relationship between a plurality of state parameter groups and a plurality of DCRs.

[0025] In some possible implementation manners, the state parameter group includes at least one of the following state parameters: the SOC of the battery pack, the temperature of the battery pack, the current of the battery pack, the charge and discharge direction of the battery pack, the charge and discharge time of the battery pack, and the SOH of the battery pack.

[0026] In some possible implementation manners, the detection module is specifically configured to determine the DCR corresponding to the state parameter group of the battery pack among the plurality of DCRs as the first DCR.

[0027] In some possible implementation manners, the state parameter group includes a first state parameter, and the corresponding relationship includes a plurality of values of the first state parameter corresponding to the plurality of DCRs. The detection module is specifically configured to determine, among the plurality of values, a first value and a second value that are closest to the parameter value of the first state parameter of the battery pack; determine the DCR corresponding to the first value and the DCR corresponding to the second value according to the first value, the second value, and the corresponding relationship; determine the DCR corresponding to the parameter value of the first state parameter of the battery pack based on an interpolation algorithm according to the DCR corresponding to the first value and the DCR corresponding to the second value; and determine the DCR corresponding to the parameter value of the first state parameter of the battery pack as the first DCR.

[0028] In some possible implementation manners, the detection module is further configured to obtain initial DCRs of a plurality of battery cells in the battery pack; obtain an initial DCR of a standard battery cell, where the initial DCR of the standard battery cell is obtained by testing under the same state parameters as the initial DCRs of the plurality of battery cells in the battery pack, and the standard battery cell is the battery cell used to establish the corresponding relationship; and determine the calibration coefficient according to the initial DCR of the standard battery cell and the initial DCRs of the plurality of battery cells in the battery pack.

[0029] In some possible implementation manners, the calibration coefficient is equal to the ratio between the average value of the initial DCRs of the plurality of battery cells in the battery pack and the initial DCR of the standard battery cell.

[0030] In some possible implementation manners, the calibration module is specifically configured to determine the product of the first DCR and the calibration coefficient as the second DCR.

[0031] In some possible implementations, the detection device further includes a judgment module, and the judgment module is configured to determine whether there is uneven current sharing among the multiple battery packs according to the second DCR of the multiple parallel-connected battery packs.

[0032] In some possible implementations, the judgment module is specifically configured to determine that there is uneven current sharing among the multiple battery packs when the ratio between the second DCR of the first battery pack and the second DCR of the second battery pack among the multiple battery packs is greater than a preset DCR threshold, where the first battery pack is the battery pack with the largest second DCR among the multiple battery packs, and the second battery pack is the battery pack with the smallest second DCR among the multiple battery packs.

[0033] In some possible implementations, the battery pack is a battery cluster or an electric cabinet, the battery cluster or the electric cabinet includes multiple electric boxes connected in series and / or in parallel, and the electric box includes multiple battery cells connected in series and / or in parallel.

[0034] In a third aspect, a energy storage system is provided, including: multiple battery packs connected in parallel; and the DCR detection device according to the second aspect or any one of the possible implementations of the second aspect, where the detection device is configured to detect the DCR of the battery packs. Description of the Drawings

[0035] To more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained according to the drawings without creative efforts.

[0036] Figure 1 is a schematic diagram of a possible energy storage system according to an embodiment of the present application.

[0037] Figure 2 is a schematic diagram of a possible battery cluster according to an embodiment of the present application.

[0038] Figure 3 is a schematic diagram of a possible electric box according to an embodiment of the present application.

[0039] Figure 4 is a schematic flowchart of the DCR detection method according to an embodiment of the present application.

[0040] Figure 5 is a schematic flowchart of determining the first DCR of a battery pack according to an embodiment of the present application.

[0041] Figure 6 is a schematic diagram of the DCR calculation principle.

[0042] Figure 7 It is a schematic flowchart of a possible test method for the initial DCR of a battery cell.

[0043] Figure 8 It is a schematic flowchart for calibrating the first DCR according to an embodiment of the present application.

[0044] Figure 9 is Figure 4 A flowchart of a possible implementation manner of the detection method for the DCR shown.

[0045] Figure 10 It is a schematic block diagram of a DCR detection device according to an embodiment of the present application.

[0046] Figure 11 It is a schematic block diagram of a DCR detection device according to an embodiment of the present application. Detailed implementation manners

[0047] The following further describes the implementation manners of the present application in detail with reference to the drawings and embodiments. The detailed descriptions and drawings of the following embodiments are used to exemplarily illustrate the principle of the present application, but cannot be used to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0048] Since energy storage systems usually have requirements such as high voltage and large capacity, a large number of batteries are required in the energy storage system to be connected in series and parallel to form products such as electrical cabinets or containers, and energy interaction is carried out with the power grid through the PCS. Among them, the PCS is used to realize the conversion between the AC signal of the power grid and the DC signal of the energy storage system.

[0049] As an example, as Figure 1 shown, the energy storage system 1 includes N battery clusters, namely battery clusters R1 to battery cluster R N , where N is a positive integer. The battery clusters R1 to battery cluster R N are connected in parallel with each other and perform charging or discharging with the power grid through the PCS. Among them, each battery cluster includes a plurality of electrical boxes. For example, as Figure 2 shown, each of the battery clusters R1 to battery cluster R N includes M electrical boxes, namely electrical boxes B1 to electrical box B M , where M is a positive integer. The M electrical boxes are connected in series; or, some of the M electrical boxes are first connected in parallel to form a parallel unit, and then multiple parallel units are connected in series to form a battery cluster. Among them, each electrical box is assembled by K battery cells. For example, as Figure 3 shown, each of the electrical boxes B1 to electrical box B M includes K battery cells connected in series and / or in parallel, namely battery cells C1 to battery cell C K .

[0050] When the consistency among multiple battery clusters in an energy storage system is poor, the DCR difference between the battery clusters may lead to a current difference between the battery clusters, resulting in uneven current distribution between the battery clusters and affecting the capacity and power of the battery clusters. Therefore, it is necessary to detect the DCR of the battery clusters.

[0051] However, in practical applications, due to the influence of factors such as the materials of battery cells and the test environment, the initial DCR of battery cells has a certain distribution pattern. Therefore, the DCR test scheme established based on some of these battery cells cannot be accurately applied to the DCR detection of other battery packs.

[0052] For this reason, the present application provides a DCR detection scheme. After obtaining the DCR of a battery pack, the DCR of the battery pack is calibrated through an appropriate calibration coefficient, thereby improving the accuracy of the DCR.

[0053] Figure 4 FIG. shows the DCR detection method of the embodiment of the present application. This method can be executed by a battery management system (BMS), such as including a master battery management unit (MBMU) and / or a sub-battery management unit (SBMU). As Figure 4 shown, the DCR detection method 100 of the embodiment of the present application includes some or all of the following steps.

[0054] In step 110, determine the first DCR of the battery pack.

[0055] In step 120, calibrate the first DCR according to a preset calibration coefficient to obtain the second DCR of the calibrated battery pack.

[0056] After obtaining the DCR of the battery pack, the DCR of the battery pack is calibrated through an appropriate calibration coefficient. This calibration coefficient can improve the inconsistency between the initial DCRs of different battery cells in the battery pack, thereby improving the accuracy of the DCR.

[0057] Here, the battery pack can be, for example, a battery cluster or an electric cabinet. Among them, the battery cluster or the electric cabinet includes a plurality of electric boxes connected in series and / or in parallel, and each electric box includes a plurality of battery cells connected in series and / or in parallel. Among them, the electric cabinet can be regarded as a battery product formed by battery clusters. Therefore, the battery cluster in the embodiment of the present application can also be replaced by an electric cabinet. A plurality of electric cabinets can be assembled to form a container. Hereinafter, taking the battery pack as Figures 1 to 3Taking the battery cluster shown as an example, the DCR detection method 100 of the embodiments of the present application will be described in detail. Of course, in addition to the uneven current sharing that may occur between multiple parallel-connected battery clusters, uneven current sharing may also occur between other units that need to be connected in parallel in the energy storage system. The DCR of these parallel-connected units can also be determined by method 100 to facilitate the timely discovery and prevention of uneven current sharing between these parallel-connected units.

[0058] The embodiments of the present application can determine the first DCR of the battery pack in various ways. For example, as Figure 5 shown, step 110 may include step 111 and step 112.

[0059] Among them, in step 111, a set of state parameters of the battery pack is obtained, and the set of state parameters includes at least one state parameter of the battery pack.

[0060] In step 112, according to the set of state parameters of the battery pack and the corresponding relationship between a plurality of preset sets of state parameters and a plurality of DCRs, the first DCR of the battery pack is determined.

[0061] The set of state parameters includes at least one state parameter of the battery pack. For example, it includes at least one of the following state parameters: the SOC of the battery pack, the temperature of the battery pack, the current of the battery pack, the charge and discharge direction of the battery pack, the charge and discharge time of the battery pack, and the SOH of the battery pack, etc., which are various state parameters that may affect the DCR of the battery pack.

[0062] Among them, the SOC can, for example, represent the percentage of the remaining capacity of the battery; the SOH can, for example, represent the percentage between the current capacity of the battery and the factory capacity, which is used to measure the aging state of the battery; the charge and discharge direction of the battery pack includes charging and discharging, that is, the positive or negative of the current; the charge and discharge time can, for example, refer to the time duration of the charge and discharge current.

[0063] Due to its electrochemical characteristics, the internal resistance of the battery may be affected by multiple factors. In order to more accurately detect the DCR of the battery pack, first, it is necessary to identify the influencing factors associated with the DCR of the battery pack. The embodiments of the present application provide multiple influencing factors that may affect the DCR of the battery pack, including the SOC of the battery pack, the temperature T of the battery pack, the current I of the battery pack, the charge and discharge direction of the battery pack, the charge and discharge time Time of the battery pack, and the SOH of the battery pack mentioned above. Among them, for the charging state or the discharging state, the DCR of the battery pack = f(SOC, SOH, I, Time, T, charge and discharge direction), where f is the relationship between these state parameters and the DCR, that is, the corresponding relationship between the above-mentioned multiple sets of state parameters and multiple DCRs.

[0064] By establishing a DCR database that includes the correspondence between the state parameter group of the battery pack and the DCR, and using this DCR database to determine the first DCR of the battery pack under the current state parameters, it comprehensively considers the influence of different influencing factors on the DCR of the battery pack and can improve the accuracy of the first DCR.

[0065] The following details the process of establishing the correspondence between multiple state parameter groups and multiple DCRs.

[0066] After determining various state parameters that may affect the DCR of the battery, the value of each state parameter during the DCR test can be designed. For example, as shown in Table 1, for various state parameters that may affect the DCR, including SOC, temperature, current, charge / discharge direction, charge / discharge time, and SOH, a reasonable value range matching the actual operating conditions of the battery is set. Here, only taking the charging time in the range of 5s - 60s and the charging current in the range of 120A - 180A as an example, in actual applications, a longer charging time range and / or a larger current range can be set.

[0067] Table 1

[0068] Number Status parameter Value of the status parameter 1 SOC Value taken every 5% SOC 2 Temperature T Value taken every 5% within the operating temperature range of the battery 3 Current I Value taken every 5 A within the range of 120 A - 180 A 4 Charge and discharge time T Value taken every 5 s within the range of 5 s - 60 s 5 Charge and discharge direction Charge or discharge 6 Aging state Value taken every 5% SOH

[0069] During the test process, the method of controlling variables is adopted. According to the value requirements described in Table 1, the value of each of the 6 state parameters in Table 1 is changed individually, and a series of DCR tests are carried out for the values of this state parameter.

[0070] For example, taking a fresh battery cell as the test object, 100% SOH, the test environment temperature is 25°C, and the charging current is constant at 140A under the charging state. Under this condition, the DCR of the battery cell at different SOCs is tested, and the values of SOC include 0%, 5%, 10%, 15%, ……, 95%, 100%.

[0071] First, for the DCR test when SOC is 0%, adjust the SOC of the battery cell to 0%, fully static for a period of time such as 2 hours, charge the battery cell at a current of 140A for 60s, and record the voltage of the battery cell at multiple moments. For example, as shown in Table 2, when SOC is 0%, record the voltage of the battery cell within the charging time of 5s - 60s at 5s time intervals.

[0072] Table 2

[0073] Charge and discharge time T / s 0 5 10 15 20 …… 55 60 Voltage / V <![CDATA[U0]]> <![CDATA[U5]]> <![CDATA[U 10 > <![CDATA[U 15 > <![CDATA[U 20 > …… <![CDATA[U 55 > <![CDATA[U 60 >

[0074] According to Table 2, the DCR of the battery cell can be calculated for different charging durations. As an example, the following formula can be used Figure 6The DCR test principle shown calculates the DCR of a battery cell. As Figure 6 shown, after charging a battery cell with a constant current I for a certain duration △T, the DCR of the battery cell can be determined based on the voltage U, current I, and the initial voltage U0 of the battery cell at the moment after this duration △T. Among them, DCR = (U - U0) / I.

[0075] In Table II, U0 is the initial voltage, that is, the static voltage. Then, the DCR of the battery cell at 0 s of charging is DCR 01 , the DCR of the battery cell at 5 s of charging 02 = (U5 - U0) / I, the DCR of the battery cell at 10 s of charging 03 = (U 10 - U0) / I, the DCR of the battery cell at 15 s of charging 04 = (U 15 - U0) / I, the DCR of the battery cell at 20 s of charging 05 = (U 20 - U0) / I, ……, the DCR of the battery cell at 55 s of charging 06 = (U 55 - U0) / I, the DCR of the battery cell at 60 s of charging 07 = (U 60 - U0) / I, where I = 140 A.

[0076] In this way, the corresponding relationship between the charging time and DCR can be obtained as shown in Table III under the conditions of meeting 100% SOH, a test environment temperature of 25°C, a constant charging current of 140 A in the charging state, and an SOC of 0%.

[0077] Table III

[0078] Charge and discharge time T / s 0 5 10 15 20 …… 55 60 DCR <![CDATA[DCR 01 > <![CDATA[DCR 02 > <![CDATA[DCR 03 > <![CDATA[DCR 04 > <![CDATA[DCR 05 > …… <![CDATA[DCR 06 > <![CDATA[DCR 07 >

[0079] Secondly, adjust the SOC of the battery cell to 5%, and perform the test according to the above operations. Similarly, the corresponding relationship between the charging time and DCR can be obtained as shown in Table III under the conditions of meeting 100% SOH, a test environment temperature of 25°C, a constant charging current of 140 A in the charging state, and an SOC of 5%.

[0080] In sequence, adjust the SOC of each battery cell at intervals of 5% SOC, and conduct DCR tests according to the above operations. A DCR mapping table can be obtained under the conditions of 100% SOH, a test environment temperature of 25°C, a constant charging current of 140A in the charging state, SOC values of 0%, 5%, 10%, 15%, …, 95%, 100%, and charging times of 0s, 5s, 15s, …, 60s. For example, the corresponding relationship between the state parameter group composed of charging time and SOC and DCR as shown in Table 4.

[0081] Table 4

[0082]

[0083] In the same way, sequentially change the values of the remaining state parameters such as temperature, current, and SOH, and complete a series of DCR tests for a series of values under other state parameters through the single-factor control variable method. Summarize the DCR data for all state parameters at different values to obtain the corresponding relationship between the state parameter group composed of SOC, temperature, current, charge-discharge direction, charge-discharge time, and SOH and DCR, thereby establishing a multi-dimensional full-life cycle DCR database for the battery.

[0084] This DCR database includes the corresponding relationships between multiple state parameter groups and DCR. This DCR database can be written into the BMS software, for example. During the actual application process, the state parameter group of the battery pack can be collected, including the SOC, temperature, current, charge-discharge direction, charge-discharge time, and SOH of the battery pack, and the DCR corresponding to the parameter values of each state parameter in the state parameter group of the battery pack can be found from the DCR database stored in the BMS.

[0085] The corresponding relationships between each state parameter in the state parameter group and DCR can be implemented in various forms. For example, the corresponding relationship between each state parameter in the state parameter group and DCR can be a table of the mapping relationship between the values of each state parameter and DCR; it can also be a curve or formula for representing the corresponding relationship between each state parameter in the state parameter group and DCR, such as DCR = f(SOC, SOH, I, Time, T, charge-discharge direction); or other forms that can represent the corresponding relationship between each state parameter in the state parameter group and DCR. Among them, Tables 1 to 4 are used as examples in the form of a mapping table, and the mapping relationship between each state parameter in the state parameter group and DCR is stored in the BMS in the form of a mapping table.

[0086] In one implementation, in step 122, the DCRs in the DCR database corresponding to the state parameter group of the battery system can be directly determined as the first DCR of the battery pack, so as to simply and quickly obtain the DCR of the battery pack.

[0087] In another implementation, in step 122, for the parameter values between adjacent values in the DCR database, the DCR corresponding to the parameter value can be calculated by an interpolation algorithm, such as a linear interpolation algorithm. Assume that the state parameter group includes a first state parameter, and the DCR database includes multiple values of the first state parameter corresponding to multiple DCRs. If the parameter value of the first state parameter in the current state parameter group of the battery pack is not equal to any of the multiple values of the first state parameter in the DCR database, then, among the multiple values of the first state parameter in the corresponding relationship, the first value and the second value closest to the parameter value of the first state parameter of the battery pack can be found, and the DCRs corresponding to the first value and the second value can be determined, so as to obtain the DCR corresponding to the parameter value of the first state parameter of the battery pack through the interpolation algorithm.

[0088] Specifically, in step 122, the first value and the second value closest to the parameter value of the first state parameter of the battery pack can be determined among the multiple values of the first state parameter in the DRC database; according to the first value, the second value, and the corresponding relationship between the first parameter value and the DCR in the DCR database, the DCR corresponding to the first value and the DCR corresponding to the second value can be determined; according to the DCR corresponding to the first value and the DCR corresponding to the second value, based on the interpolation algorithm, the DCR corresponding to the parameter value of the first state parameter of the battery pack can be determined; and the DCR corresponding to the parameter value of the first state parameter of the battery pack can be determined as the first DCR of the battery pack.

[0089] Taking SOC as an example, assume that the parameter values of each state parameter in the current state parameter group of the battery pack are as follows: SOH is 100%, the test environment temperature is 25°C, the charging current is constant at 140A under the charging state, the charging duration is 60s, and the SOC is 8%. If the SOC in the DCR database includes the DCRs corresponding to SOCs of 0%, 5%, 10%, 15%, ……, 95%, 100% at an interval of 5%. Then, the SOC values closest to 8% SOC are 5% and 10%, and the DCRs under the conditions of SOH being 100%, the test environment temperature being 25°C, the charging current being constant at 140A under the charging state, the charging duration being 60s, and the SOC being 5%, and the DCRs under the conditions of SOH being 100%, the test environment temperature being 25°C, the charging current being constant at 140A under the charging state, the charging duration being 60s, and the SOC being 10% can be found respectively.

[0090] Assume that the DCR values corresponding to 5% SOC and 10% SOC are DCR 16 and DCR 26 respectively. Then, according to the linear interpolation algorithm, the DCR under the conditions of 100% SOH, a test environment temperature of 25°C, a constant charging current of 140 A during charging, a charging duration of 60 s, and an SOC of 8% can be obtained as DCR 16 +(DCR 26 -DCR 16 )*(8% - 5%) / (10% - 5%) = DCR 16 +3(DCR 26 -DCR 16 ) / 5.

[0091] It can be understood that the DCR of the battery pack determined in the above manner is the DCR of the battery pack before calibration, that is, the first DCR. However, since the DCR database is established based on the DCR test results of a few standard battery cells, and in fact, there is a certain distribution law among the initial DCRs of different battery cells, the DCR database established based on some of these battery cells cannot be accurately applied to the DCR detection of other battery packs.

[0092] As an example, as Figure 7 shown, a possible test method for the initial DCR of a battery cell. The initial DCR of a battery cell usually refers to the DCR obtained by testing the battery cell on the production line. As Figure 7 shown, the battery cells on the production line usually need to go through processes such as formation, aging, measuring the coefficient K at room temperature, DCR testing and capacity testing, and DCR grouping. Among them, in the DCR testing process, a battery cell with a certain SOC can be charged for a certain duration. For example, the battery cell can be charged at a constant current for 30 s when the SOC of the battery cell is 20%, and based on the DCR test principle such as Figure 6 shown, the DCR of the battery cell is calculated, and this DCR can be used as the initial DCR of the battery cell.

[0093] Of course, the environmental temperature is different when performing the DCR testing process shown in Figure 7 . Therefore, optionally, the DCR of the battery cell can be temperature-corrected according to the current temperature of the battery cell to the DCR of the battery cell at 25°C. For example, the relationship between temperature and DCR such as f(T)=0.007T 2 -0.0627T + 1.8401 can be used to correct the initial DCR of the battery cell, and the corrected initial DCR = [f(25) / f(T)] * the DCR before correction.

[0094] In the embodiments of the present application, the initial DCR of the battery cell may refer to the initial DCR after temperature correction. The initial DCR of the battery cell can be stored, for example, by uploading the initial DCR of the battery cell to a manufacturing execution system (MES).

[0095] Due to the differences between the initial DCRs of different battery cells, the initial DCRs of different battery cells are not the same, and it is impossible to directly call the data in the DCR standard library obtained by testing only some of the battery cells. Therefore, it is necessary to set appropriate calibration coefficients to reduce or eliminate the differences between the initial DCRs of different battery cells to a certain extent.

[0096] In some embodiments, as Figure 8 shown, method 100 may further include step 121, step 122, and step 123.

[0097] Among them, in step 121, the initial DCRs of multiple battery cells in the battery pack are obtained.

[0098] In step 122, the initial DCR of the standard battery cell is obtained.

[0099] Among them, the standard battery cell is the battery cell used to establish the corresponding relationship, and the initial DCR of the standard battery cell is tested under the same state parameters as the initial DCRs of multiple battery cells in the battery pack.

[0100] The same state parameters refer to the state parameters used when testing the initial DCR of the battery cell on the production line, such as constant current charging for 30 s under the above-mentioned 20% SOC condition.

[0101] In step 123, the calibration coefficient is determined according to the initial DCR of the standard battery cell and the initial DCRs of multiple battery cells in the battery pack.

[0102] The calibration coefficient can be the calibration coefficient for this battery pack, and the calibration coefficients corresponding to different battery packs can be the same or different.

[0103] Using the initial DCR of the standard battery cell and the initial DCRs of multiple battery cells in the battery pack to determine the calibration coefficient enables the calibration coefficient to effectively improve the inconsistency between the initial DCRs of different battery cells in the battery pack.

[0104] Optionally, the calibration coefficient can be equal to the ratio between the mean value of the initial DCRs of multiple battery cells in the battery pack and the initial DCR of the standard battery cell.

[0105] At this time, in some embodiments, in step 120, the product of the first DCR and the calibration coefficient can be determined as the second DCR, so that the first DCR of the battery pack can be simply and quickly calibrated to obtain the calibrated second DCR.

[0106] Take Figures 1 to 3 as an example. N battery clusters are assembled to form battery products such as electric cabinets or containers. Each battery cluster among the N battery clusters includes M electric boxes, and each electric box among the M electric boxes includes K battery cells. Then, each battery cluster includes M * K battery cells. When determining the calibration coefficient corresponding to the battery cluster, it is necessary to obtain the average value R of the initial DCRs of the M * K battery cells in the battery cluster mean and the initial DCR of a standard battery cell. For example, if the initial DCR of the standard battery cell used to establish the DCR database is 0.7 mΩ, then the calibration coefficient corresponding to the battery cluster can be set to be equal to R mean / 0.7 mΩ.

[0107] During the actual production process, the DCRs at different levels, such as the battery cell level, the electric box level, the battery cluster or electric cabinet level, and the container level, can all be recorded for production control. By using, for example, Figure 7 the DCR test process shown to obtain the initial DCR of the battery cell, the identification information corresponding to the battery cell, such as a barcode, can be used as its identity label, and the corresponding initial DCR can be entered into the MES system. When multiple battery cells are assembled to form an electric box, if the electric box is not an object of DCR testing, then when generating the barcode corresponding to the electric box, the DCR of the electric box can be calculated based on the initial DCRs of the multiple battery cells in the electric box. Similarly, the DCR at the battery cluster or electric cabinet level can be calculated based on the DCRs of the multiple electric boxes included in the battery cluster or electric cabinet, and the calculated DCR of the electric cabinet can be implanted into the SBMU corresponding to the electric cabinet; the DCR at the container level can be calculated based on the DCRs of the multiple electric cabinets included in the container, and the calculated DCR of the container can be implanted into the MBMU corresponding to the container. The DCR values of the electric cabinet or container can be stored in a local database or uploaded to a cloud server. After the DCR of the electric cabinet or container is detected online subsequently, the DCR data in the local database or cloud server can be updated.

[0108] When multiple electric boxes are assembled to form a battery cluster, the barcode scanning device can automatically identify the barcodes of the multiple electric boxes in the battery cluster. Through the MES system, the barcodes of the battery cells in each electric box and the initial DCRs obtained after the battery cells are tested for DCR on the production line can be traced, and the average value of the initial DCRs of the battery cells in the battery cluster can be calculated.

[0109] According to the mean value of the initial DCR of each battery cell in the battery cluster and the initial DCR of the standard battery cell used to establish the DCR database, the calibration coefficient corresponding to the battery cluster can be determined. For example, the mean value R of the initial DCR of each battery cell in the battery cluster max The ratio to the initial DCR of the standard battery cell can be used as the calibration coefficient. The calibration coefficient corresponding to the battery cluster can be stored in the BMS software of the battery cluster. When the calibration coefficient needs to be used subsequently, the calibration coefficient is read, and the first DCR corresponding to the state parameter group of the battery cluster found from the DCR database is multiplied by the calibration coefficient to obtain the calibrated second DCR, and the second DCR is used as the actual DCR of the battery cluster under the state parameter group for subsequent operations such as unbalanced current judgment.

[0110] When multiple battery packs are connected in parallel to the power grid, since the voltages of the multiple battery packs are the same, based on Ohm's law, the DCR difference between the multiple battery packs will cause a current difference between the battery packs, resulting in an unbalanced current situation between the multiple battery packs, affecting the capacity and power of the entire battery system. Therefore, in some embodiments, the detection method 100 may further include: determining whether there is an unbalanced current between the multiple battery packs according to the second DCR of the multiple parallel-connected battery packs. That is, by detecting the second DCR of the multiple parallel-connected battery packs, it is determined whether there is an unbalanced current between the multiple battery packs, so as to timely discover and prevent the unbalanced current between the parallel-connected battery packs.

[0111] Optionally, it is possible to determine whether there is an unbalanced current between the multiple battery packs according to the difference between the second DCRs of the multiple parallel-connected battery packs. For example, the difference between the second DCR of the first battery pack and the second DCR of the second battery pack in the battery pack, where the first battery pack is the battery pack with the largest second DCR among the multiple battery packs, and the second battery pack is the battery pack with the smallest second DCR among the multiple battery packs.

[0112] For example, it can be determined that there is an unbalanced current between the multiple battery packs when the ratio of the second DCR of the first battery pack to the second DCR of the second battery pack among the multiple battery packs is greater than the corresponding DCR threshold; or for another example, it can be determined that there is an unbalanced current between the multiple battery packs when the difference between the second DCR of the first battery pack and the second DCR of the second battery pack is greater than the corresponding DCR threshold.

[0113] In this way, according to the DCR difference between the battery pack with the largest DCR and the battery pack with the smallest DCR among the multiple battery packs, the unbalanced current situation between the multiple battery packs can be timely discovered.

[0114] As an example, such as Figure 9The detection process of the DCR shown, taking the battery pack as an example of a battery cluster. Among them, the SBMU of each battery cluster is responsible for the management of the corresponding battery cluster and uploads relevant data to the MBMU. The MBMU is responsible for the operation management of the entire system formed by multiple battery clusters and can interact with external devices.

[0115] As Figure 9 shown, in step 101, it is determined that the battery cluster is in an operating condition, that is, the battery cluster is currently charging or discharging.

[0116] In step 102, the parameter values of multiple state parameters in the state parameter group of the battery cluster are obtained.

[0117] For example, the state parameter group includes parameters such as SOC, temperature, current, charge and discharge direction, charge and discharge time, and SOH.

[0118] In step 103, the SBMU determines the first DCR of the battery cluster according to the current state parameter group of the battery cluster and the corresponding relationship between multiple state parameter groups and multiple DCRs in the DCR database.

[0119] In step 104, the SBMU obtains the calibration coefficient corresponding to the battery cluster.

[0120] In step 105, the SBMU calibrates the first DCR according to the calibration coefficient to obtain the second DCR.

[0121] Among them, the SBMU can report the second DCR of the corresponding battery cluster to the MBMU.

[0122] In step 106, the MBMU calculates the inter-cluster internal resistance difference according to the DCRs of multiple parallel-connected battery clusters.

[0123] For example, the internal resistance difference can be expressed by DCRmax / DCRmin, where DCRmax and DCRmin respectively represent the largest second DCR and the smallest second DCR among the second DCRs of multiple battery clusters.

[0124] In step 107, the MBMU determines whether the inter-cluster internal resistance difference DCRmax / DCRmin is greater than a preset DCR threshold, and this DCR threshold is denoted as x%, where x is a preset value.

[0125] When the inter-cluster internal resistance difference DCRmax / DCRmin is greater than the DCR threshold x%, that is, when DCRmax / DCRmin > x%, step 108 is executed; when the inter-cluster internal resistance difference DCRmax / DCRmin is less than or equal to the DCR threshold x%, that is, when DCRmax / DCRmin ≤ x%, the DCR of the battery cluster continues to be detected.

[0126] In step 108, an uneven current sharing strategy is executed.

[0127] This uneven current sharing strategy can be built into the BMS software, for example, to reduce the degree of uneven current sharing between multiple parallel-connected battery clusters. For example, the current of some or all of the battery clusters can be reduced based on a certain strategy.

[0128] The method for detecting the DCR of the embodiments of the present application is described in detail above. Next, in combination with Figure 10 and Figure 11 the detection device for the DCR of the embodiments of the present application is described in detail. The technical features described in the method embodiments are applicable to the following device embodiments.

[0129] Figure 10 is a schematic block diagram of the detection device for the DCR of the embodiments of the present application. As Figure 10 shown, the detection device 200 includes a detection module 210 and a calibration module 220.

[0130] Among them, the detection module 210 is used to determine the first DCR of the battery pack; the calibration module 220 is used to calibrate the first DCR according to a preset calibration coefficient to obtain the second DCR of the calibrated battery pack.

[0131] This battery pack can be a battery cluster or an electric cabinet, for example. The battery cluster or the electric cabinet includes a plurality of electric boxes connected in series and / or in parallel, and the electric box includes a plurality of battery cells connected in series and / or in parallel.

[0132] In some embodiments, the detection module 210 is specifically configured to obtain a set of state parameters of the battery pack, where the set of state parameters includes at least one state parameter of the battery pack; and determine the first DCR of the battery pack according to the set of state parameters of the battery pack and the corresponding relationship between a plurality of preset sets of state parameters and a plurality of DCRs.

[0133] This set of state parameters includes, for example, at least one of the following state parameters: the state of charge SOC of the battery pack, the temperature of the battery pack, the current of the battery pack, the charge and discharge direction of the battery pack, the charge and discharge time of the battery pack, and the state of health SOH of the battery pack.

[0134] In some embodiments, the detection module 210 is specifically configured to determine the DCR corresponding to the set of state parameters of the battery pack among a plurality of DCRs as the first DCR.

[0135] In some embodiments, the set of state parameters includes a first state parameter, and the corresponding relationship includes multiple values of the first state parameter corresponding to multiple DCRs. The detection module is specifically configured to determine, among the multiple values, a first value and a second value that are closest to the parameter value of the first state parameter of the battery pack; determine the DCR corresponding to the first value and the DCR corresponding to the second value according to the first value, the second value, and the corresponding relationship; determine the DCR corresponding to the parameter value of the first state parameter of the battery pack based on the interpolation algorithm according to the DCR corresponding to the first value and the DCR corresponding to the second value; and determine the DCR corresponding to the parameter value of the first state parameter of the battery pack as the first DCR.

[0136] In some embodiments, the detection module 210 is further configured to obtain the initial DCRs of multiple battery cells in the battery pack; obtain the initial DCR of a standard battery cell, where the initial DCR of the standard battery cell is tested under the same state parameters as the initial DCRs of the multiple battery cells in the battery pack, and the standard battery cell is the battery cell used to establish the corresponding relationship; and determine a calibration coefficient according to the initial DCR of the standard battery cell and the initial DCRs of the multiple battery cells in the battery pack.

[0137] The calibration coefficient may, for example, be equal to the ratio between the average value of the initial DCRs of the multiple battery cells in the battery pack and the initial DCR of the standard battery cell.

[0138] At this time, in some embodiments, the calibration module 220 is specifically configured to determine the product of the first DCR and the calibration coefficient as the second DCR.

[0139] In some embodiments, the detection device 200 further includes a judgment module, and the judgment module is configured to determine whether there is uneven current sharing among multiple battery packs according to the second DCRs of the multiple parallel-connected battery packs.

[0140] In some embodiments, the judgment module is specifically configured to determine that there is uneven current sharing among the multiple battery packs when the ratio between the second DCR of the first battery pack and the second DCR of the second battery pack among the multiple battery packs is greater than a preset DCR threshold, where the first battery pack is the battery pack with the largest second DCR among the multiple battery packs, and the second battery pack is the battery pack with the smallest second DCR among the multiple battery packs.

[0141] It should be understood that for the specific manner of DCR detection by the detection device 200 and the beneficial effects generated, reference may be made to the relevant descriptions in the method embodiments. For simplicity, they are not elaborated here.

[0142] The present application further provides an energy storage system, for example Figures 1 to 3The energy storage system 1 shown in []. The energy storage system 1 includes a plurality of battery packs connected in parallel, and the DCR detection device 200 described in any of the above embodiments. The detection device 200 is used to detect the DCR of the battery pack.

[0143] This application also provides a computer-readable storage medium for storing a computer program. When the computer program is executed by a computing device, the computing device is enabled to implement the DCR detection method 100 described in any of the above embodiments. Optionally, the computer program may be a computer program in the BMS.

[0144] This application also provides a DCR detection device 300. The detection device 300 may be, for example, a BMS, such as including an SBMU and / or an MBMU. As Figure 11 shown, the detection device 300 includes a processor 310 and a memory 320. Among them, the memory 320 is used to store instructions, and the processor 310 is used to read the instructions and execute the method 100 of various embodiments of the present application based on the instructions. Among them, the memory 320 may be a separate device independent of the processor 310, or may be integrated in the processor 310.

[0145] Optionally, as Figure 11 shown, the detection device 300 may further include a transceiver 330. The processor 310 may control the transceiver 330 to communicate with other devices. For example, information or data may be sent to other devices, or information or data sent by other devices may be received.

[0146] It should be understood that the processor in the embodiments of the present application may be an integrated circuit chip with the ability to process signals. In the implementation process, each step of the above method embodiments can be completed by the integrated logic circuit in the hardware of the processor or the instructions in the form of software. The above-mentioned processor may be a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components. It can implement or execute the various methods, steps and logic block diagrams disclosed in the embodiments of the present application. The general-purpose processor may be a microprocessor or any conventional processor, etc. The steps of the method disclosed in combination with the embodiments of the present application can be directly embodied as being executed and completed by the hardware decoding processor, or executed and completed by the combination of the hardware and software modules in the decoding processor. The software module may be located in a mature storage medium in the art such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, etc. This storage medium is located in the memory, and the processor reads the information in the memory and combines its hardware to complete the steps of the above method.

[0147] The memory in the embodiments of the present application may be a volatile memory or a non-volatile memory, or include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example but not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchlink dynamic random access memory (SLDRAM), and direct rambus random access memory (DR RAM). It should be noted that the memory of the systems and methods described herein is intended to include but not be limited to these and any other suitable types of memory.

[0148] It should be noted that, on the premise of no conflict, the various embodiments described in the present application and / or the technical features in the various embodiments can be arbitrarily combined with each other, and the technical solutions obtained after the combination should also fall within the protection scope of the present application.

[0149] In the embodiments of the present application, the magnitudes of the sequence numbers of the respective steps do not mean the order of execution. The order of execution of the respective steps should be determined according to their functions and internal logics, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0150] Those of ordinary skill in the art can realize that the units and algorithm steps of the examples described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or by a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Skilled professionals can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present application.

[0151] In several embodiments provided by the present application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces. The indirect couplings or communication connections of the devices or units can be in electrical, mechanical, or other forms.

[0152] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiments of the present application.

[0153] Although the present application has been described with reference to the preferred embodiments, various improvements can be made to it and components therein can be replaced with equivalents without departing from the scope of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for detecting direct current resistance, characterized in that, The detection method includes: Determining a first DC resistance of the battery pack; Calibrating the first DC resistance according to a preset calibration coefficient to obtain a second DC resistance of the calibrated battery pack.

2. The detection method according to claim 1, wherein The determining of the first DC resistance of the battery pack includes: Obtaining a set of state parameters of the battery pack, where the set of state parameters includes at least one state parameter of the battery pack; Determining the first DC resistance of the battery pack according to the set of state parameters of the battery pack and a preset correspondence between a plurality of sets of state parameters and a plurality of DC resistances.

3. The detection method according to claim 2, characterized in that, The set of state parameters includes at least one of the following state parameters: State of charge of the battery pack, temperature of the battery pack, current of the battery pack, charge and discharge direction of the battery pack, charge and discharge time of the battery pack, and health state of the battery pack.

4. The detection method according to claim 2 or 3, characterized in that The determining of the first DC resistance of the battery pack according to the set of state parameters of the battery pack and a preset correspondence between a plurality of sets of state parameters and a plurality of DC resistances includes: Determining the DC resistance corresponding to the set of state parameters of the battery pack among the plurality of DC resistances as the first DC resistance.

5. The detection method according to claim 2 or 3, characterized in that, The set of state parameters includes a first state parameter, and the correspondence includes a plurality of values of the first state parameter corresponding to the plurality of DC resistances. The determining of the first DC resistance of the battery pack according to the set of state parameters of the battery pack and a preset correspondence between a plurality of sets of state parameters and a plurality of DC resistances includes: Determining a first value and a second value that are closest to the parameter value of the first state parameter of the battery pack among the plurality of values; Determining the DC resistance corresponding to the first value and the DC resistance corresponding to the second value according to the first value, the second value, and the correspondence; Determining the DC resistance corresponding to the parameter value of the first state parameter of the battery pack based on an interpolation algorithm according to the DC resistance corresponding to the first value and the DC resistance corresponding to the second value; Determining the DC resistance corresponding to the parameter value of the first state parameter of the battery pack as the first DC resistance.

6. The detection method according to any one of claims 2 to 5, characterized in that, The detection method further includes: Obtaining initial DC resistances of a plurality of battery cells in the battery pack; Obtaining an initial DC resistance of a standard battery cell, where the initial DC resistance of the standard battery cell is tested under the same state parameters as the initial DC resistances of the plurality of battery cells in the battery pack, and the standard battery cell is the battery cell used to establish the correspondence; Determining the calibration coefficient according to the initial DC resistance of the standard battery cell and the initial DC resistances of the plurality of battery cells in the battery pack.

7. The detection method according to claim 6, wherein The calibration coefficient is equal to the ratio between the average value of the initial DC resistances of the plurality of battery cells in the battery pack and the initial DC resistance of the standard battery cell.

8. The detection method according to any one of claims 1 to 7, characterized in that, The determining of the second DC resistance of the battery pack according to the first DC resistance and a preset calibration coefficient includes: Determining the product of the first DC resistance and the calibration coefficient as the second DC resistance.

9. The detection method according to any one of claims 1 to 8, characterized in that, The detection method further includes: Determine whether there is uneven current sharing among the multiple battery packs according to the second DC resistance of the multiple parallel-connected battery packs.

10. The detection method according to claim 9, characterized in that, The determining whether there is uneven current sharing among the multiple battery packs according to the second DC resistance of the multiple parallel-connected battery packs includes: When the ratio between the second DC resistance of the first battery pack and the second DC resistance of the second battery pack among the multiple battery packs is greater than a preset DC resistance threshold, determine that there is uneven current sharing among the multiple battery packs, where the first battery pack is the battery pack with the largest second DC resistance among the multiple battery packs, and the second battery pack is the battery pack with the smallest second DC resistance among the multiple battery packs.

11. The detection method according to any one of claims 1 to 10, characterized in that, The battery pack is a battery cluster or an electric cabinet, and the battery cluster or the electric cabinet includes multiple electrical boxes connected in series and / or in parallel, and the electrical box includes multiple battery cells connected in series and / or in parallel.

12. A detection device for DC resistance, characterized in that, The detection device includes: A detection module for determining the first DC resistance of the battery pack; A calibration module for calibrating the first DC resistance according to a preset calibration coefficient to obtain the second DC resistance of the calibrated battery pack.

13. The detection device according to claim 12, characterized in that Specifically, the detection module is used to: Obtain a state parameter group of the battery pack, where the state parameter group includes at least one state parameter of the battery pack; Determine the first DC resistance of the battery pack according to the state parameter group of the battery pack and a preset corresponding relationship between multiple state parameter groups and multiple DC resistances.

14. The detection device according to claim 13, wherein The state parameter group includes at least one of the following state parameters: The state of charge of the battery pack, the temperature of the battery pack, the current of the battery pack, the charge and discharge direction of the battery pack, the charge and discharge time of the battery pack, and the health state of the battery pack.

15. The detection device according to claim 13 or 14, characterized in that, Specifically, the detection module is used to: Determine the DC resistance corresponding to the state parameter group of the battery pack among the multiple DC resistances as the first DC resistance.

16. The detection device according to claim 13 or 14, characterized in that, The state parameter group includes a first state parameter, and the corresponding relationship includes multiple values of the first state parameter corresponding to the multiple DC resistances. Specifically, the detection module is used to: Among the multiple values, determine a first value and a second value that are closest to the parameter value of the first state parameter of the battery pack; According to the first value, the second value, and the corresponding relationship, determine the DC resistance corresponding to the first value and the DC resistance corresponding to the second value; Based on an interpolation algorithm, determine the DC resistance corresponding to the parameter value of the first state parameter of the battery pack according to the DC resistance corresponding to the first value and the DC resistance corresponding to the second value; Determine the DC resistance corresponding to the parameter value of the first state parameter of the battery pack as the first DC resistance.

17. The detection device according to any one of claims 13 to 16, characterized in that The detection module is further used to: Obtain the initial DC resistances of multiple battery cells in the battery pack; Obtain the initial DC resistance of a standard battery cell, where the initial DC resistance of the standard battery cell is tested under the same state parameters as the initial DC resistances of the multiple battery cells in the battery pack, and the standard battery cell is the battery cell used to establish the corresponding relationship. Determine the calibration coefficient according to the initial DC resistance of the battery cell according to the standard and the initial DC resistances of a plurality of battery cells in the battery pack.

18. The detection device according to claim 17, characterized in that, The calibration coefficient is equal to the ratio between the average value of the initial DC resistances of a plurality of battery cells in the battery pack and the initial DC resistance of the battery cell according to the standard.

19. The detection device according to any one of claims 12 to 18, characterized in that, Specifically, the calibration module is configured to Determine the second DC resistance as the product of the first DC resistance and the calibration coefficient.

20. The detection device according to any one of claims 12 to 19, characterized in that, The detection device further includes a judgment module, and the judgment module is configured to Determine whether there is non-uniform current sharing among the plurality of battery packs according to the second DC resistances of the plurality of parallel-connected battery packs.

21. The detection device according to claim 20, characterized in that, Specifically, the judgment module is configured to Determine that there is non-uniform current sharing among the plurality of battery packs when the ratio between the second DC resistance of the first battery pack and the second DC resistance of the second battery pack among the plurality of battery packs is greater than a preset DC resistance threshold, where the first battery pack is the battery pack with the largest second DC resistance among the plurality of battery packs, and the second battery pack is the battery pack with the smallest second DC resistance among the plurality of battery packs.

22. The detection device according to any one of claims 12 to 21, characterized in that, The battery pack is a battery cluster or an electric cabinet, and the battery cluster or the electric cabinet includes a plurality of electric boxes connected in series and / or in parallel, and each electric box includes a plurality of battery cells connected in series and / or in parallel.

23. An energy storage system, characterized in that, Comprising: A plurality of parallel-connected battery packs; And The DC resistance detection device according to any one of claims 12 to 22, and the detection device is configured to detect the DC resistance of the battery pack.

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