Method and device for estimating state of health of battery

Abstract

The invention provides a battery health state estimation method and apparatus. The method comprises the steps of determining a working state of a to-be-tested battery pack; for each battery cell in the battery pack to be detected, determining a relation curve which corresponds to the battery cell and is used for representing the open-circuit voltage of the battery cell and the residual electric quantity of the battery cell according to the working state and the current battery cell temperature of the battery cell, and determining a first electric quantity change value and a first accumulated capacity change value which correspond to the battery cell according to the relation curve, determining a first health state estimation value of the battery cell; and determining a first electric quantity value and a second electric quantity value corresponding to the to-be-tested battery pack according to the relation curves corresponding to all the battery cells, determining a second electric quantity change value and a second accumulated capacity change value corresponding to the to-be-tested battery pack according to the first electric quantity value and the second electric quantity value, and determining a second health state estimation value of the to-be-tested battery pack. According to the invention, the accuracy of the health state of the battery is improved.

Description

Technical Field

[0001] The present application relates to the technical field of battery health status assessment, and in particular, to a battery health status estimation method and device. Background Art

[0002] At present, the estimation of the power battery state of health (SOH) is one of the core algorithms of the battery management system. Accurate SOH estimation can provide support for accurate power battery state of charge estimation, battery allowable charge and discharge power estimation, battery charging control, battery balancing and other functions. It is of great significance to improving the energy utilization efficiency of power batteries, reducing the risk of battery thermal runaway, and the maintenance and residual value evaluation of power batteries.

[0003] The SOH estimation methods mainly include the empirical model method based on test data, the online estimation method based on the battery model and various filtering algorithms, the online estimation based on the battery SOC definition and the data-driven SOH estimation method. Regardless of the method, the current SOH estimation mainly focuses on evaluating the health status of the battery from the perspective of the entire pack, while ignoring the impact of the aging of each single cell on the aging of the entire pack, thereby affecting the accuracy of the battery assembly SOH estimation. Summary of the invention

[0004] In view of this, the purpose of the present application is to provide a method and device for estimating the health status of a battery to overcome at least one of the above-mentioned defects.

[0005] In a first aspect, an embodiment of the present application provides a method for estimating a battery health state, which is applied to a vehicle, and the method includes: when the current battery performance of the battery pack to be tested meets the estimation trigger condition, determining the working state of the battery pack to be tested; for each battery cell in the battery pack to be tested, determining the relationship curve between the open-circuit voltage of the battery cell and the remaining power of the battery cell corresponding to the battery cell according to the working state and the current battery cell temperature of the battery cell, and determining the first power change value and the first cumulative capacity change value corresponding to the battery cell according to the relationship curve, so as to determine the first health state estimation value of the battery cell; determining the first power value and the second power value corresponding to the battery pack to be tested according to the relationship curves corresponding to all the battery cells, and determining the second power change value and the second cumulative capacity change value corresponding to the battery pack to be tested according to the first power value and the second power value, so as to determine the second health state estimation value of the battery pack to be tested.

[0006] In an optional embodiment of the present application, whether the current battery performance of the battery pack to be tested meets the estimated trigger condition is determined in the following manner: in response to the vehicle being powered on, the current battery capacity and the historical battery capacity of the battery pack to be tested of the vehicle are obtained, and the historical battery capacity is the battery capacity stored at the time when the vehicle is powered off; it is determined whether the difference between the current battery capacity and the historical battery capacity is greater than a capacity threshold; if the difference between the current battery capacity and the historical battery capacity is greater than the capacity threshold, it is determined that the current battery performance of the battery pack to be tested does not meet the estimated trigger condition; if the difference between the current battery capacity and the historical battery capacity is not greater than the capacity threshold, the current battery pack temperature and the sleep time of the battery pack to be tested are detected, and the sleep time is the time when the battery pack to be tested stops working; it is determined whether the current battery pack temperature and the sleep time meet the estimated trigger correspondence relationship; if the current battery pack temperature and the sleep time meet the estimated trigger correspondence relationship, it is determined that the current battery performance of the battery pack to be tested meets the estimated trigger condition; if the current battery pack temperature and the sleep time do not meet the estimated trigger correspondence relationship, it is determined that the current battery performance of the battery pack to be tested does not meet the estimated trigger condition.

[0007] In an optional embodiment of the present application, the method also includes: filtering out the minimum first health status estimation value from the first health status estimation values ​​of all battery cells; and displaying the minimum first health status estimation value and the second health status estimation value on the central control screen of the vehicle.

[0008] In an optional embodiment of the present application, the working state of the battery pack to be tested is determined in the following manner: when the current battery performance of the battery pack to be tested meets the estimated trigger condition, the current battery power and the historical battery power of the battery pack to be tested are detected; it is determined whether the difference between the current battery power and the historical battery power is greater than zero; if the difference between the current battery power and the historical battery power is greater than zero, it is determined that the working state of the battery pack to be tested is a charging state; if the difference between the current battery power and the historical battery power is not greater than zero, it is determined that the working state of the battery pack to be tested is a discharging state.

[0009] In an optional embodiment of the present application, the relationship curve between the open-circuit voltage of each battery cell and the remaining power of the battery cell is determined in the following manner: according to the working state of the battery pack to be tested, multiple first curves between the open-circuit voltage of the battery cell and the remaining power of the battery cell in the working state corresponding to each battery cell in the battery pack to be tested are determined; for each battery cell, according to the current battery cell temperature of the battery cell, a target first curve corresponding to the current battery cell temperature is filtered out from the multiple first curves, and the target first curve is determined as the relationship curve corresponding to the battery cell.

[0010] In an optional embodiment of the present application, the first health status estimation value of each battery cell is determined in the following manner: for each battery cell, the first estimation point and the second estimation point corresponding to the battery cell are screened out from the relationship curve corresponding to the battery cell; for each battery cell, the third power value corresponding to the first estimation point and the fourth power value corresponding to the second estimation point are determined based on the first estimation point and the second estimation point, and the first power change value is determined based on the third power value and the fourth power value; for each battery cell, the first current value collected when the battery cell is at the third power value is obtained, the first capacity value is determined based on the first current value, the second current value collected when the battery cell is at the fourth power value is obtained, the second capacity value is determined based on the second current value, and the first cumulative capacity change value is determined based on the first capacity value and the second capacity value; for each battery cell, the first health status estimation value of the battery cell is determined based on the ratio of the first power change value to the first cumulative capacity change value.

[0011] In an optional embodiment of the present application, the first cumulative capacity change value of each battery cell is determined in the following manner: for each battery cell, the first current value and a first sum of all current values ​​of the battery cell collected before the first current value are calculated, and the first sum is determined as the first capacity value of the battery cell; the second current value and a second sum of all current values ​​of the battery cell collected before the second current value are calculated, and the second sum is determined as the second capacity value of the battery cell; for each battery cell, the first cumulative capacity change value of the battery cell is determined based on the difference between the first capacity value and the second capacity value.

[0012] In an optional embodiment of the present application, the second health state estimation value of the battery pack to be tested is determined in the following manner: a third estimation point and a fourth estimation point of the battery pack to be tested are screened out from the relationship curves corresponding to all battery cells; a first power value corresponding to the third estimation point and a second power value corresponding to the fourth estimation point are determined based on the third estimation point and the fourth estimation point, and a second power change value is determined based on the first power value and the second power value; a third current value collected when the battery pack to be tested is at the first power value is obtained, a third capacity value is determined based on the third current value, a fourth current value collected when the battery pack to be tested is at the second power value is obtained, a fourth capacity value is determined based on the fourth current value, and a second cumulative capacity change value is determined based on the third capacity value and the fourth capacity value; and a second health state estimation value of the battery pack to be tested is determined based on the ratio of the second power change value to the second cumulative capacity change value.

[0013] In an optional embodiment of the present application, the second cumulative capacity change value of the battery pack to be tested is determined in the following manner: calculating the third current value and a third sum of all current values ​​of the battery pack to be tested collected before the third current value, and determining the third sum as the third capacity value of the battery pack to be tested; calculating the fourth current value and a fourth sum of all current values ​​of the battery pack to be tested collected before the fourth current value, and determining the fourth sum as the fourth capacity value of the battery pack to be tested; and determining the second cumulative capacity change value of the battery pack to be tested based on the difference between the third capacity value and the fourth capacity value.

[0014] In a second aspect, an embodiment of the present application also provides a device for estimating a battery health state, the device comprising: a working state determination module, used to determine the working state of the battery pack to be tested when the current battery performance of the battery pack to be tested meets the estimation trigger condition; a first health state estimation value determination module, used to determine, for each battery cell in the battery pack to be tested, a relationship curve between the open circuit voltage of the battery cell and the remaining power of the battery cell corresponding to the battery cell according to the working state and the current battery cell temperature of the battery cell, and determine the first power change value and the first cumulative capacity change value corresponding to the battery cell according to the relationship curve, so as to determine the first health state estimation value of the battery cell; a second health state estimation value determination module, used to determine the first power value and the second power value corresponding to the battery pack to be tested according to the relationship curves corresponding to all battery cells, and determine the second power change value and the second cumulative capacity change value corresponding to the battery pack to be tested according to the first power value and the second power value, so as to determine the second health state estimation value of the battery pack to be tested.

[0015] In a third aspect, an embodiment of the present application further provides an electronic device, comprising: a processor, a memory and a bus, wherein the memory stores machine-readable instructions executable by the processor, and when the electronic device is running, the processor and the memory communicate via the bus, and when the machine-readable instructions are executed by the processor, the steps of the method described above are performed.

[0016] In a fourth aspect, an embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the method described above are executed.

[0017] The battery health state estimation method and device provided in the embodiment of the present application, when the current battery performance of the battery pack to be tested meets the estimation trigger condition, determines the working state of the battery pack to be tested; for each battery cell in the battery pack to be tested, according to the working state and the current battery cell temperature of the battery cell, determines the relationship curve corresponding to the battery cell for characterizing the open circuit voltage of the battery cell and the remaining battery capacity of the battery cell, and determines the first charge change value and the first cumulative capacity change value corresponding to the battery cell according to the relationship curve, and determines the first health state estimation value of the battery cell; according to the relationship curves corresponding to all the batteries, determines the first charge value and the second charge value corresponding to the battery pack to be tested, and determines the second charge change value and the second cumulative capacity change value corresponding to the battery pack to be tested according to the first charge value and the second charge value, and determines the second health state estimation value of the battery pack to be tested. Through this application, the accuracy of predicting the battery health state is improved, and support is provided for the precise control of the battery, so as to achieve full utilization of battery performance while ensuring the battery life, reduce user usage costs, and improve user usage experience.

[0018] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are specifically cited below and described in detail with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 One of the flow charts of the method for estimating the battery health status provided in the embodiment of the present application;

[0021] Figure 2 The second flowchart of the method for estimating the battery health status provided in the embodiment of the present application;

[0022] Figure 3 A schematic diagram of the structure of a battery health status estimation device provided in an embodiment of the present application;

[0023] Figure 4 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0024] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application usually described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, each other embodiment obtained by those skilled in the art without making creative work belongs to the scope of protection of the present application.

[0025] First, the application scenarios to which the present application is applicable are introduced. The present application can be applied to the technical field of battery health status assessment.

[0026] Research has found that the estimation methods of the power battery state of health (SOH) mainly include empirical model methods based on test data, online estimation methods based on battery models and various filtering algorithms, online estimation based on battery SOC definition, and data-driven SOH estimation methods. Regardless of the method, the current SOH estimation mainly focuses on evaluating the health status of the battery from the perspective of the entire pack, while ignoring the impact of the aging of each single cell on the aging of the entire pack, thereby affecting the accuracy of the battery assembly SOH estimation.

[0027] Based on this, the embodiment of the present application provides a method and device for estimating the health status of a battery. When the current battery performance of the battery pack to be tested meets the estimation trigger condition, the working state of the battery pack to be tested is determined; for each battery cell in the battery pack to be tested, according to the working state and the current battery cell temperature of the battery cell, the relationship curve corresponding to the battery cell for characterizing the open circuit voltage of the battery cell and the remaining power of the battery cell is determined, and according to the relationship curve, the first power change value and the first cumulative capacity change value corresponding to the battery cell are determined to determine the first health status estimation value of the battery cell; according to the relationship curves corresponding to all the batteries, the first power value and the second power value corresponding to the battery pack to be tested are determined, and according to the first power value and the second power value, the second power change value and the second cumulative capacity change value corresponding to the battery pack to be tested are determined to determine the second health status estimation value of the battery pack to be tested. Through this application, the accuracy of predicting the health status of the battery is improved, and support is provided for the precise control of the battery, so that the battery performance can be fully utilized under the premise of ensuring the battery life, reducing the user's use cost and improving the user's use experience.

[0028] This application is applied to vehicles, and the execution subject may be an on-board processor or a battery management system (BMS). When the execution subject is a battery management system, the battery management system sends the estimated SOH value to the on-board processor for display and storage.

[0029] See also Figure 1 , Figure 1 This is one of the flow charts of the method for estimating the battery health status provided in the embodiment of the present application. Figure 1 As shown in , the method for estimating the battery health status provided in the embodiment of the present application includes:

[0030] S101. When the current battery performance of the battery pack to be tested meets an estimation trigger condition, determine the working state of the battery pack to be tested.

[0031] Specifically, whether the current battery performance of the battery pack to be tested meets the estimation trigger condition is determined in the following manner:

[0032] In response to the vehicle being powered on, a current battery capacity and a historical battery capacity of a battery pack to be tested of the vehicle are obtained.

[0033] Here, the historical battery capacity is the battery capacity stored when the vehicle is powered off.

[0034] Determine whether the difference between the current battery capacity and the historical battery capacity is greater than the capacity threshold;

[0035] In this step, the capacity threshold is a pre-set determination condition.

[0036] In order to improve the accuracy of capacity estimation, please set the capacity threshold and limit the capacity change, so as to reduce the large error introduced by the cumulative capacity due to the error of the current sensor, thereby causing errors in capacity estimation. When the cumulative capacity change of charge and discharge is less than the capacity threshold, SOH estimation can be performed after judging other conditions. If the cumulative capacity change of charge and discharge is greater than the capacity threshold, SOH estimation is not performed.

[0037] If the difference between the current battery capacity and the historical battery capacity is greater than the capacity threshold, it is determined that the current battery performance of the battery pack to be tested does not meet the estimation trigger condition;

[0038] If the difference between the current battery capacity and the historical battery capacity is not greater than the capacity threshold, the current battery pack temperature and sleep time of the battery pack to be tested are detected.

[0039] Here, the sleep time is the time when the battery pack to be tested stops working;

[0040] Determine whether the current battery pack temperature and sleep time meet the estimated trigger correspondence relationship;

[0041] If the current battery pack temperature and sleep time meet the estimated trigger correspondence relationship, it is determined that the current battery performance of the battery pack to be tested meets the estimated trigger condition;

[0042] If the current battery pack temperature and sleep time do not meet the estimation trigger correspondence relationship, it is determined that the current battery performance of the battery pack to be tested does not meet the estimation trigger condition.

[0043] Here, due to the influence of temperature on electrochemical reactions, battery parameters at different temperatures are different. The battery health status estimation in this application uses battery parameters at different temperatures to obtain more accurate battery cell parameters. The premise for correcting battery cell parameters based on battery parameters is that the battery needs sufficient standing time to eliminate the voltage changes caused by polarization reactions. The battery management system determines whether to perform parameter correction each time it is powered on based on the battery temperature and sleep time during power-on.

[0044] If the current battery pack temperature is low, a longer standing time is required to eliminate the influence of the polarization voltage. The sum of the standing time corresponding to the current battery pack temperature and the current power-on time is the sleep time, which means that the current battery performance of the battery pack to be tested meets the estimated trigger conditions. If the sleep time satisfies the estimated trigger correspondence, it is determined that the current battery performance of the battery pack to be tested meets the estimated trigger conditions.

[0045] In this step, the working state of the battery pack to be tested is determined by:

[0046] When the current battery performance of the battery pack to be tested meets the estimated trigger condition, detecting the current battery power and the historical battery power of the battery pack to be tested;

[0047] Here, the historical battery power refers to the battery power remaining in the vehicle when the vehicle was powered off last time, and the current battery power refers to the battery power currently remaining in the vehicle.

[0048] Determine whether the difference between the current battery power and the historical battery power is greater than zero;

[0049] If the difference between the current battery power and the historical battery power is greater than zero, it is determined that the working state of the battery pack to be tested is the charging state; if the difference between the current battery power and the historical battery power is not greater than zero, it is determined that the working state of the battery pack to be tested is the discharging state.

[0050] Due to the hysteresis effect of the battery, there are differences in the OCV-SOC curves during the battery charging and discharging process, which leads to large errors in the single cell SOC value obtained using one OCV curve.

[0051] In order to obtain a more accurate SOC value of the battery cell, the battery health status estimation method based on the OCV-SOC curve in the present application distinguishes whether to use the charging or discharging OCV curve through strategy identification. The battery management system needs to record the SOC value at the initial power-on each time it is powered on and started, and needs to store the SOC value at the initial power-on and the SOC value during power-off and hibernation each time the power is turned off and hibernated. When the battery management system is powered on again after hibernation, the changes in these two SOC values ​​are used to identify whether the last vehicle operation process was a charging process or a discharging process, thereby determining whether to use the charging OCV curve or the discharging OCV curve for the SOC estimation based on the OCV-SOC curve this time, thereby improving the SOC estimation accuracy.

[0052] In an optional embodiment, the SOC value may be recorded by a battery management system or an onboard processor. The battery management system sends the required recorded data to the onboard processor, which records it in the NVM memory (NodeVersion Manager).

[0053] S102. For each battery cell in the battery pack to be tested, determine the relationship curve between the open circuit voltage of the battery cell and the remaining power of the battery cell according to the working status and the current battery cell temperature of the battery cell, and determine the first power change value and the first cumulative capacity change value corresponding to the battery cell according to the relationship curve to determine the first health status estimation value of the battery cell.

[0054] In this step, the relationship curve between the open circuit voltage of each battery cell and the remaining power of the battery cell is determined by the following method:

[0055] Here, the relationship curve between the open circuit voltage (OCV) of the battery cell and the state of charge (SOC) of the battery cell is referred to as an OCV-SOC curve.

[0056] Determine, according to the working state of the battery pack to be tested, a plurality of first curves between the open circuit voltage of the battery cell and the remaining power of the battery cell in the working state corresponding to each battery cell in the battery pack to be tested;

[0057] For each battery cell, if the working state of the battery pack to be tested is a charging state, multiple first curves corresponding to the charging state of the battery cell are selected; if the working state of the battery pack to be tested is a discharging state, multiple first curves corresponding to the discharging state of the battery cell are selected.

[0058] For each battery cell, according to the current battery cell temperature of the battery cell, a target first curve corresponding to the current battery cell temperature is screened out from the multiple first curves, and the target first curve is determined as the relationship curve corresponding to the battery cell.

[0059] According to the current battery cell temperature, a target first curve corresponding to the current battery cell temperature is selected from the plurality of first curves and determined as the relationship curve of the battery cell.

[0060] Since there are differences in OCV-SOC curves under different aging states, the battery health state estimation method in the present application adopts the OCV-SOC curves under different aging states to obtain a more accurate battery cell charge value. The OCV-SOC curves under different aging states can be obtained by performing OCV-SOC curve tests on monomers under different aging states. After obtaining the aged OCV-SOC curve, preliminary analysis and identification can be performed. If the difference between the OCV-SOC curve in the early aging stage and the initial unaged OCV-SOC curve is small and the impact on the accuracy can be ignored, the initial unaged OCV-SOC curve is directly used. If the difference is large, the OCV-SOC curve of the corresponding stage is used according to the aging state identification.

[0061] The first health status estimation value of each battery cell is determined in the following manner:

[0062] See also Figure 2 , Figure 2 This is a second flow chart of a method for estimating the battery health status provided in an embodiment of the present application. Figure 2 As shown in , the method for estimating the battery health status provided in the embodiment of the present application includes:

[0063] S201 . For each battery cell, select a first estimation point and a second estimation point corresponding to the battery cell from a relationship curve corresponding to the battery cell.

[0064] S202. For each battery cell, determine, according to the first estimation point and the second estimation point, a third power value corresponding to the first estimation point and a fourth power value corresponding to the second estimation point, and determine a first power change value according to the third power value and the fourth power value.

[0065] According to the curve of the first estimated point, the corresponding horizontal coordinate and vertical coordinate are found from the position corresponding to the first estimated point. The horizontal coordinate is the open circuit voltage value and the vertical coordinate is the power value. The second estimated point is the same and will not be repeated here.

[0066] S203. For each battery cell, obtain a first current value collected when the battery cell is at a third power value, determine a first capacity value based on the first current value, obtain a second current value collected when the battery cell is at a fourth power value, determine a second capacity value based on the second current value, and determine a first cumulative capacity change value based on the first capacity value and the second capacity value.

[0067] Specifically, the first accumulated capacity change value of each battery cell is determined in the following manner:

[0068] For each battery cell, a first current value and a first sum of all current values ​​of the battery cell collected before the first current value are calculated, and the first sum is determined as a first capacity value of the battery cell; a second current value and a second sum of all currents of the battery cell collected before the second current value are calculated, and the second sum is determined as a second capacity value of the battery cell;

[0069] For each battery cell, a first accumulated capacity change value of the battery cell is determined according to a difference between the first capacity value and the second capacity value.

[0070] In an optional embodiment, the current of the battery during the charging and discharging process can be measured in real time. According to the time point when the battery cell is at the third power value, the current value at this time point is recorded and determined as the first current value, and all current values ​​collected before the first current value are accumulated, and the first sum after accumulation is the first capacity value; according to the time point when the battery cell is at the fourth power value, the current value at this time point is recorded and determined as the second current value, and all current values ​​collected before the second current value are accumulated, and the second sum after accumulation is the second capacity value.

[0071] Here, the current values ​​are collected in real time by the current sensor and transmitted to the on-board processor or battery management system.

[0072] S204 . For each battery cell, determine a first health status estimation value of the battery cell according to a ratio of the first power change value to the first accumulated capacity change value.

[0073] Specifically, the first health status estimation value of each battery cell is calculated by the following formula:

[0074]

[0075] Among them, CellSOH i Represents the first health status estimation value corresponding to the i-th battery cell, CellCap available It represents the available capacity of the ith battery cell under the current operating conditions. CellCapRare represents the rated capacity of the ith battery cell, which is a fixed constant.

[0076] The available capacity of each battery cell is calculated using the following formula:

[0077]

[0078] Among them, CellCap available It represents the available capacity of the ith battery cell under the current working condition, Cap1 represents the first capacity value of the ith battery cell under the current working condition, Cap2 represents the second capacity value of the ith battery cell under the current working condition, SOC1 represents the third capacity value of the ith battery cell under the current working condition, and SOC2 represents the fourth capacity value of the ith battery cell under the current working condition.

[0079] In the present application, the charge change of each battery cell from SOC1 point to SOC2 point, that is, the first charge change value, is calculated. The result of Cap1-Cap2 in the formula is the first cumulative capacity change value of the battery cell from SOC1 point to SOC2 point. The cumulative capacity change value is mainly obtained by accumulating the current of the battery assembly. If only the change of the assembly current is considered, the cumulative capacity change of each single cell is consistent. In the present application, a refined design is made for the cumulative capacity change, and the influence of the balanced charging and discharging process of the single battery cell on the cumulative capacity change is considered to obtain a more accurate cumulative capacity change of the battery cell.

[0080] In an optional embodiment, during the discharge process from SOC1 to SOC2, the first cumulative capacity change value is 100 Ah (ampere hour). If the SOC of some single cells needs to start the discharge process due to the need for balanced discharge, the cumulative balanced discharge capacity of the single cells that are balanced discharged is calculated. Assuming that the balanced discharge is started for single cell No. 1, the SOC corresponding to SOC1 is 97%, the SOC corresponding to SOC2 is 6%, and the discharge capacity of the balanced process is 1 Ah. The balanced discharge is not started for single cell No. 2, the SOC corresponding to SOC1 is 95%, and the SOC corresponding to SOC2 is 5%. Then the available capacity of single cell No. 1 is:

[0081] CellCap available1 =(100+1)÷(97-6)=110.98Ah

[0082] The available capacity of the No. 2 single cell is:

[0083] CellCap available2 =100÷(95-5)=105.26Ah

[0084] Here, in order to reduce the impact of the errors in the cumulative capacity change value and the charge change value on the estimated value of the battery health state, the requirement for the two estimation points is that the difference in the remaining charge (SOC) of the battery cells at the two points needs to be greater than a certain threshold, and the third charge value (SOC1) of the first estimation point is set as a high-end SOC value, and the fourth charge value (SOC2) of the second estimation point is set as a low-end SOC value. Then, SOC1 is required to be greater than the first set threshold, and SOC2 is required to be less than the second set threshold, thereby widening the range between SOC1 and SOC2, thereby reducing the impact of the SOC and cumulative capacity change value errors on the estimated value of the battery health state, and the first set threshold is greater than the second set threshold. For example, SOC1 is required to be greater than 90%, and SOC2 is required to be less than 10%.

[0085] In order to improve the accuracy of the health status estimation value, the requirement that SOC1 is greater than the first set threshold and that SOC2 is less than the second set threshold will reduce the frequency of capacity estimation. Therefore, it is necessary to find a balance between estimation accuracy and estimation frequency. The frequency of capacity estimation can be increased by appropriately lowering the threshold requirements for SOC1 and SOC2 while meeting the accuracy requirements.

[0086] Each time the conditions for triggering capacity estimation are met, the corresponding weight is determined based on the difference between SOC1 and SOC2. The larger the difference, the larger the weight. If the difference between SOC1 and SOC2 is greater than threshold 1, it is considered that the accuracy of the health status estimate is higher, and the health status estimate of this estimate is directly used. If the difference between SOC1 and SOC2 is greater than threshold 2 but less than threshold 1, it is considered that the accuracy of the health status estimate of this estimate is slightly lower, and the health status estimate calculated this time and the corresponding weight are stored and not used directly, and threshold 1 is greater than threshold 2.

[0087] Furthermore, when a health status estimate with a higher weight appears, the health status estimate with the higher weight is used to replace the health status estimate with the new weight. If the newly calculated health status estimate has a low weight but the time since the last health status estimate was calculated is long, the new health status estimate is used to replace the old health status estimate for storage.

[0088] If the newly calculated health status estimate has a low weight and is short from the last health status estimate calculation, the health status estimate calculated this time will be discarded. When the time interval from the last SOH update to the current time is greater than time threshold 1, but the capacity estimation that satisfies the difference between SOC1 and SOC2 greater than threshold 1 has not been triggered, and the time difference from the health status estimate calculated to satisfy the SOC difference greater than threshold 2 to the current time is less than time threshold 2, the health status estimate calculated to satisfy the SOC difference threshold 2 is used to proportionally update the SOH, and the duration of time threshold 1 is greater than the duration of time threshold 2.

[0089] For example, through calculation, it is considered that SOC1 is greater than 95%, and SOC2 is required to be less than 10% or the difference range between SOC1 and SOC2 is greater than or equal to 85%. The calculated health status estimate has a higher accuracy. At the same time, SOC1 is set to 90% and SOC2 is set to 20% as the acceptable minimum SOC difference range, which is the threshold 2 mentioned above.

[0090] If SOC1 is detected to be 95% and SOC2 is 10%, the weight of this health status estimation value is considered to be 1-(100-(95-10))÷(100-(90-20)=0.5; if SOC1 is detected to be 93% and SOC2 is 17%, the weight of this health status estimation value is considered to be 1-(100-(93-17))÷(100-(90-20)=0.2. The health status estimation value with a weight greater than or equal to 0.5 can be used directly as the target value. The health status estimation value with a weight of 0.2 determines whether it needs to be stored based on the time from the last health status estimation value. If it needs to be stored, when the SOH reaches the predetermined time and no health status estimation value with a higher weight is triggered, the SOH is updated proportionally with this health status estimation value.

[0091] Since there are errors in the estimation of the first health state estimation value of the battery cell in the above steps, usually the SOH of a battery management system changes very little in a power-on cycle. From the perspective of improving user experience, the SOH should not change significantly in a power-on cycle, so it is necessary to control the output change of SOH. After the first health state estimation value of the battery cell is calculated, this first health state estimation value cannot be used directly. Instead, the SOH obtained based on the first health state estimation value is used as the target value for SOH estimation. After a certain number of charge and discharge cycles or a certain period of time, the SOH is allowed to track a certain threshold to the target value. When the final output SOH has tracked to the target SOH and has not triggered the estimation of the first health state estimation value, the battery management system can change with the offline test data based on the empirical model.

[0092] For example, the output of the first health status estimation value of the battery cell was 90% before, and now the output is 85%. Through charging and discharging and other operations, it changes towards the current calculated 85%. The battery management system will reach 85% after a certain number of cycles. If it is not triggered in the future, the SOH can still be calculated based on the data in the offline table. The offline table is a summary table of changing data that accumulates with use and aging.

[0093] S103. Determine the first charge value and the second charge value corresponding to the battery pack to be tested according to the relationship curves corresponding to all battery cells, and determine the second charge change value and the second accumulated capacity change value corresponding to the battery pack to be tested according to the first charge value and the second charge value, so as to determine the second health status estimation value of the battery pack to be tested.

[0094] In this step, the second health status estimation value of the battery pack to be tested is determined by:

[0095] Filter out the third estimation point and the fourth estimation point of the battery pack to be tested from the relationship curves corresponding to all the battery cells;

[0096] Determine, according to the third estimation point and the fourth estimation point, a first power value corresponding to the third estimation point and a second power value corresponding to the fourth estimation point, and determine, according to the first power value and the second power value, a second power change value;

[0097] Here, the first power value corresponding to the third estimation point is the maximum power value in the relationship curves corresponding to all battery cells. Similarly, the second power value corresponding to the fourth estimation point is the minimum power value in the relationship curves corresponding to all battery cells.

[0098] Obtain a third current value collected when the battery pack to be tested is at a first power value, determine a third capacity value according to the third current value, obtain a fourth current value collected when the battery pack to be tested is at a second power value, determine a fourth capacity value according to the fourth current value, and determine a second accumulated capacity change value according to the third capacity value and the fourth capacity value;

[0099] Specifically, the second accumulated capacity change value of the battery pack to be tested is determined in the following manner:

[0100] Calculating the third current value and a third sum of all current values ​​of the battery pack to be tested collected before the third current value, and determining the third sum as a third capacity value of the battery pack to be tested;

[0101] Calculating a fourth current value and a fourth sum of all current values ​​of the battery pack to be tested collected before the fourth current value, and determining the fourth sum as a fourth capacity value of the battery pack to be tested;

[0102] In another optional embodiment, the current of the battery during the charging and discharging process can be measured in real time, and according to the time point when the battery cell is at the first power value, the current value at this time point is recorded and determined as a third current value, and all current values ​​collected before the third current value are accumulated, and the third total after accumulation is the third capacity value; according to the time point when the battery cell is at the second power value, the current value at this time point is recorded and determined as a fourth current value, and all current values ​​collected before the fourth current value are accumulated, and the fourth total after accumulation is the fourth capacity value.

[0103] A second accumulated capacity change value of the battery pack to be tested is determined according to the difference between the third capacity value and the fourth capacity value.

[0104] A second health state estimation value of the battery pack to be tested is determined according to the ratio of the second power change value to the second accumulated capacity change value.

[0105] Specifically, the second health status estimation value of the battery pack to be tested is calculated by the following formula:

[0106]

[0107] Among them, PackSOH1 represents the estimated value of the second health state corresponding to the battery pack to be tested, and PackCap available The available capacity of the battery pack under test under the current operating conditions. CellCapRare represents the rated capacity of the battery pack under test, and the rated capacity is a fixed constant.

[0108] Here, considering the impact of the inconsistency of the SOC of the single cells in the battery assembly on the available capacity of the assembly, it can be used to evaluate the second health state estimate of the battery pack to be tested due to the inconsistent SOC in the current state. This second health state estimate may be smaller than the first health state estimate in PackSOH2.

[0109] The available capacity of the battery pack under test under the current working conditions is calculated using the following formula:

[0110]

[0111] Among them, PackCap available It represents the available capacity of the battery pack under the current working condition, Cap3 represents the third capacity value of the battery pack under the current working condition, Cap4 represents the fourth capacity value of the battery pack under the current working condition, SOC3 represents the first charge value of the battery pack under the current working condition, and SOC4 represents the second charge value of the battery pack under the current working condition.

[0112] In an optional embodiment, the minimum first health state estimation value is screened out from the first health state estimation values ​​of all battery cells;

[0113] The minimum first health status estimate corresponding to all cells is determined by the following formula:

[0114] PackSOH2 = Min(CellSOH i )

[0115] PackSOH2 represents the minimum first health status estimate corresponding to the battery cell in the battery pack to be tested, CellSOH i Represents the first health status estimation value corresponding to the i-th battery cell.

[0116] The minimum value of the SOH of all single cells. This assembly SOH is defined as only considering the aging of the battery capacity, without considering the impact of the inconsistent battery SOC on the available capacity of the assembly. It can be used for BMS internal control strategies such as charge and discharge control.

[0117] The minimum first health status estimate value and the second health status estimate value are displayed on the central control screen of the vehicle.

[0118] For example, the minimum first health state estimation value and the second health state estimation value may also be displayed on a dashboard of the vehicle.

[0119] The battery health state estimation method and device provided in the embodiment of the present application determine the working state of the battery pack to be tested when the current battery performance of the battery pack to be tested meets the estimation trigger condition; for each battery cell in the battery pack to be tested, determine the relationship curve corresponding to the battery cell for characterizing the open circuit voltage of the battery cell and the remaining battery capacity of the battery cell according to the working state and the current battery cell temperature of the battery cell, and determine the first charge change value and the first cumulative capacity change value corresponding to the battery cell according to the relationship curve, and determine the first health state estimation value of the battery cell; determine the first charge value and the second charge value corresponding to the battery pack to be tested according to the relationship curves corresponding to all the battery cells, and determine the second charge change value and the second cumulative capacity change value corresponding to the battery pack to be tested according to the first charge value and the second charge value, and determine the second health state estimation value of the battery pack to be tested. Through the present application, the accuracy of predicting the battery health state is improved, and support is provided for the precise control of the battery, so as to fully exert the battery performance while ensuring the battery life, reduce the user's use cost, and improve the user's use experience.

[0120] The present application mainly addresses the problem that the current estimation based on the estimated battery health status value mainly focuses on evaluating the battery health status from the perspective of the entire pack, while ignoring the working status of the battery pack and the impact of the temperature and aging of each single cell on the aging of the battery pack, thereby affecting the estimation accuracy of the second battery health status estimate of the battery pack. The present application estimates the health status of the single cells in the power battery pack to achieve a more accurate estimation of the health status of the battery pack, provide support for the precise control of the battery, and can fully exert the battery performance while ensuring the battery life, reduce user usage costs, and improve user usage experience.

[0121] This application can provide users with information on the current health status of the power battery from a capacity perspective, so that users can promptly understand the battery aging status. This application improves the trigger frequency and accuracy of online estimation by identifying the working status of the battery pack to be tested and obtaining the OCV-SOC relationship curves under different working conditions and temperatures. This application can also be used to estimate the SOC of battery packs and cells.

[0122] Based on the same inventive concept, an embodiment of the present application also provides a battery health status estimation device corresponding to the battery health status estimation method. Since the principle of solving the problem by the device in the embodiment of the present application is similar to the above-mentioned battery health status estimation method in the embodiment of the present application, the implementation of the device can refer to the implementation of the method, and the repeated parts will not be repeated.

[0123] See also Figure 3 , Figure 3 This is a schematic diagram of the structure of the battery health status estimation device provided in the embodiment of the present application. Figure 3 As shown in FIG. , the battery health status estimation device 300 includes:

[0124] A working state determination module 301, configured to determine the working state of the battery pack to be tested when the current battery performance of the battery pack to be tested meets the estimation trigger condition;

[0125] A first health state estimation value determination module 302 is used to determine, for each battery cell in the battery pack to be tested, a relationship curve between the battery cell open circuit voltage corresponding to the battery cell and the battery cell remaining power according to the working state and the current battery cell temperature of the battery cell, and determine the first power change value and the first accumulated capacity change value corresponding to the battery cell according to the relationship curve, so as to determine the first health state estimation value of the battery cell;

[0126] The second health status estimation value determination module 303 is used to determine the first power value and the second power value corresponding to the battery pack to be tested, and determine the second power change value and the second cumulative capacity change value corresponding to the battery pack to be tested based on the first power value and the second power value, so as to determine the second health status estimation value of the battery pack to be tested.

[0127] See also Figure 4 , Figure 4 This is a schematic diagram of the structure of the electronic device provided in the embodiment of the present application. Figure 4 As shown in , the electronic device 400 includes a processor 410 , a memory 420 and a bus 430 .

[0128] The memory 420 stores machine-readable instructions executable by the processor 410. When the electronic device 400 is running, the processor 410 communicates with the memory 420 via the bus 430. When the machine-readable instructions are executed by the processor 410, the above-mentioned Figure 1 The steps of the method for estimating the battery health status in the method embodiment shown, the specific implementation method can be found in the method embodiment, and will not be repeated here.

[0129] The present application also provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the computer program can execute the above-mentioned Figure 1 The steps of the method for estimating the battery health status in the method embodiment shown, the specific implementation method can be found in the method embodiment, and will not be repeated here.

[0130] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0131] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. 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 mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interfaces, and the indirect coupling or communication connection of devices or units can be electrical, mechanical or other forms.

[0132] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0133] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0134] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a non-volatile computer-readable storage medium that is executable by a processor. Based on this understanding, the technical solution of the present application can essentially be embodied in the form of a software product, or in other words, the part that contributes to the prior art or the part of the technical solution. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0135] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present application, which are used to illustrate the technical solutions of the present application, rather than to limit them. The protection scope of the present application is not limited thereto. Although the present application is described in detail with reference to the above-mentioned embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-mentioned embodiments within the technical scope disclosed in the present application, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for estimating a battery health state, characterized in that: Applied to vehicles, including: When the current battery performance of the battery pack to be tested meets the estimation trigger condition, determining the working state of the battery pack to be tested; For each battery cell in the battery pack to be tested, determine a relationship curve between the open-circuit voltage of the battery cell corresponding to the battery cell and the remaining power of the battery cell according to the working state and the current battery cell temperature of the battery cell, and determine a first power change value and a first power change value corresponding to the battery cell according to the relationship curve, and obtain a first cumulative capacity change value to determine a first health state estimation value of the battery cell; According to the relationship curves corresponding to all battery cells, the first charge value and the second charge value corresponding to the battery pack to be tested are determined, and according to the first charge value and the second charge value, the second charge change value and the second cumulative capacity change value corresponding to the battery pack to be tested are determined to determine the second health status estimation value of the battery pack to be tested.

2. The method according to claim 1, characterized in that Determine whether the current battery performance of the battery pack to be tested meets the estimated trigger conditions in the following ways: In response to the vehicle being powered on, obtaining a current battery capacity and a historical battery capacity of the battery pack to be tested of the vehicle, wherein the historical battery capacity is a battery capacity stored when the vehicle is powered off; Determine whether the difference between the current battery capacity and the historical battery capacity is greater than a capacity threshold; If the difference between the current battery capacity and the historical battery capacity is greater than the capacity threshold, determining that the current battery performance of the battery pack to be tested does not meet the estimation trigger condition; If the difference between the current battery capacity and the historical battery capacity is not greater than the capacity threshold, detecting the current battery pack temperature and sleep time of the battery pack to be tested, where the sleep time is the time when the battery pack to be tested stops working; Determining whether the current battery pack temperature and the sleep time meet an estimated trigger correspondence relationship; If the current battery pack temperature and the sleep time meet the estimation trigger correspondence relationship, determining that the current battery performance of the battery pack to be tested meets the estimation trigger condition; If the current battery pack temperature and the sleep time do not conform to the estimation trigger correspondence relationship, it is determined that the current battery performance of the battery pack to be tested does not meet the estimation trigger condition.

3. The method according to claim 1, characterized in that The method further comprises: Filter out the minimum first health state estimation value from the first health state estimation values ​​of all the battery cells; The minimum first health status estimation value and the second health status estimation value are displayed on the central control screen of the vehicle.

4. The method according to claim 1, characterized in that The working state of the battery pack to be tested is determined by: When the current battery performance of the battery pack to be tested meets the estimation trigger condition, detecting the current battery power and the historical battery power of the battery pack to be tested; Determine whether the difference between the current battery power and the historical battery power is greater than zero; If the difference between the current battery power and the historical battery power is greater than zero, determining that the working state of the battery pack to be tested is a charging state; If the difference between the current battery power and the historical battery power is not greater than zero, it is determined that the working state of the battery pack to be tested is a discharging state.

5. The method according to claim 4, characterized in that The relationship curve between the open circuit voltage of each cell and the remaining capacity of the cell is determined by the following method: According to the working state of the battery pack to be tested, determining a plurality of first curves between the open circuit voltage of the battery cell and the remaining power of the battery cell in the working state corresponding to each battery cell in the battery pack to be tested; For each battery cell, according to the current battery cell temperature of the battery cell, a target first curve corresponding to the current battery cell temperature is screened out from the multiple first curves, and the target first curve is determined as the relationship curve corresponding to the battery cell.

6. The method according to claim 5, characterized in that The first health status estimate of each battery cell is determined by: For each battery cell, selecting a first estimation point and a second estimation point corresponding to the battery cell from the relationship curve corresponding to the battery cell; For each battery cell, determine, according to the first estimation point and the second estimation point, a third power value corresponding to the first estimation point and a fourth power value corresponding to the second estimation point, and determine a first power change value according to the third power value and the fourth power value; For each battery cell, obtain a first current value collected when the battery cell is at a third power value, determine a first capacity value according to the first current value, obtain a second current value collected when the battery cell is at a fourth power value, determine a second capacity value according to the second current value, and determine a first cumulative capacity change value according to the first capacity value and the second capacity value; For each battery cell, a first health state estimation value of the battery cell is determined according to a ratio of the first power change value to the first accumulated capacity change value.

7. The method according to claim 6, characterized in that The first accumulated capacity change value of each battery cell is determined by: For each battery cell, calculating the first current value and a first sum of all current values ​​of the battery cell collected before the first current value, determining the first sum as a first capacity value of the battery cell, calculating the second current value and a second sum of all current values ​​of the battery cell collected before the second current value, and determining the second sum as a second capacity value of the battery cell; For each battery cell, a first accumulated capacity change value of the battery cell is determined according to a difference between the first capacity value and the second capacity value.

8. The method according to claim 1, characterized in that: The second health status estimation value of the battery pack to be tested is determined by: Filter out the third estimation point and the fourth estimation point of the battery pack to be tested from the relationship curves corresponding to all the battery cells; Determine, according to the third estimation point and the fourth estimation point, a first power value corresponding to the third estimation point and a second power value corresponding to the fourth estimation point, and determine, according to the first power value and the second power value, a second power change value; Obtaining a third current value collected when the battery pack to be tested is at a first power value, determining a third capacity value according to the third current value, obtaining a fourth current value collected when the battery pack to be tested is at a second power value, determining a fourth capacity value according to the fourth current value, and determining a second accumulated capacity change value according to the third capacity value and the fourth capacity value; A second health state estimation value of the battery pack to be tested is determined according to a ratio of the second power change value to the second accumulated capacity change value.

9. The method according to claim 8, characterized in that The second accumulated capacity change value of the battery pack to be tested is determined by: Calculating the third current value and a third sum of all current values ​​of the battery pack to be tested collected before the third current value, and determining the third sum as a third capacity value of the battery pack to be tested; Calculating the fourth current value and a fourth sum of all current values ​​of the battery pack to be tested collected before the fourth current value, and determining the fourth sum as a fourth capacity value of the battery pack to be tested; A second accumulated capacity change value of the battery pack to be tested is determined according to a difference between the third capacity value and the fourth capacity value.

10. A battery health status estimation device, characterized in that: include: A working state determination module, used to determine the working state of the battery pack to be tested when the current battery performance of the battery pack to be tested meets the estimation trigger condition; A first health state estimation value determination module is used to determine, for each battery cell in the battery pack to be tested, a relationship curve between the battery cell open circuit voltage corresponding to the battery cell and the battery cell remaining power according to the working state and the current battery cell temperature of the battery cell, and determine a first power change value and a first accumulated capacity change value corresponding to the battery cell according to the relationship curve, so as to determine a first health state estimation value of the battery cell; The second health state estimation value determination module is used to determine the first power value and the second power value corresponding to the battery pack to be tested based on the relationship curves corresponding to all battery cells, and determine the second power change value and the second cumulative capacity change value corresponding to the battery pack to be tested based on the first power value and the second power value, so as to determine the second health state estimation value of the battery pack to be tested.

11. An electronic device, characterized in that: include: A processor, a memory and a bus, wherein the memory stores machine-readable instructions executable by the processor, and when the electronic device is running, the processor communicates with the memory via the bus, and the processor executes the machine-readable instructions to perform the steps of any method as claimed in claims 1 to 9.

12. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 9 are executed.

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