Method of predicting maximum cell voltage of a battery and battery management system

Abstract

The application discloses a method for predicting the maximum cell voltage of a battery and a battery management system. A method for predicting the maximum cell voltage of a battery during use is provided, comprising: obtaining the remaining capacity, temperature, and maximum cell voltage and actual current of the battery at a current sampling time; predicting the pressure rise of the maximum cell voltage caused by cumulative polarization at a future time according to the remaining capacity, temperature, and actual current of the battery at the current sampling time, and the maximum cell voltage at the current sampling time and N sampling times before the current sampling time, wherein two adjacent sampling times are separated by a fixed sampling period; and determining the predicted voltage of the maximum cell voltage at the future time according to the maximum cell voltage at the current sampling time and the pressure rise. The method can predict the maximum cell voltage of the battery during use in real time, simply and efficiently.

Description

Technical Field

[0001] This application relates to the field of batteries, and specifically to a method and a battery management system for predicting the maximum cell voltage of a battery during use. Background Technology

[0002] Power batteries are widely used in applications such as electric vehicles. For example, with the rapid popularization of electric vehicles, preventing overvoltage faults during power battery energy recovery has become a major concern for many automakers. In particular, during braking or coasting recharge, battery cell polarization is severe, making the voltage prone to rising inflection points or even overvoltage. To ensure vehicle safety, various properties of the power battery need to be monitored. One useful property is the battery terminal voltage. The battery terminal voltage can be used to define the permissible charging and discharging cutoff voltages, providing information to determine the battery's operating limits and prevent overcharging. Therefore, it is necessary to predict the voltage rise trend and, based on the voltage prediction results, estimate the state of power (SOP) of the battery management system (BMS) to address the overvoltage problem. Summary of the Invention

[0003] In view of the above problems, this application provides a method, a computer program product, and a battery management system for predicting the maximum cell voltage of a battery during use, which can predict the maximum cell voltage of a battery in real time, simply and efficiently.

[0004] According to a first aspect of this application, a method for predicting the maximum cell voltage of a battery during use is provided, characterized by comprising: acquiring the remaining charge, temperature, maximum cell voltage, and actual current of the battery at the current sampling moment; predicting the voltage rise of the maximum cell voltage at a future moment due to cumulative voltammetry based on the remaining charge, temperature, and actual current of the battery at the current sampling moment, and the maximum cell voltage at the current sampling moment and N sampling moments prior to the current sampling moment, wherein two adjacent sampling moments are spaced apart by a fixed sampling period; and determining the predicted voltage of the maximum cell voltage at the future moment based on the maximum cell voltage at the current sampling moment and the voltage rise.

[0005] According to a second aspect of this application, a computer program product is provided, including computer-executable instructions that, when executed by one or more processors, cause the one or more processors to perform the method described above for predicting the maximum cell voltage of a battery during use.

[0006] According to a third aspect of this application, a battery management system including a processor is provided for managing a battery, the processor being configured to: receive the remaining charge, temperature, maximum cell voltage, and actual current of the battery at a current sampling time; predict a voltage rise in the maximum cell voltage at a future time due to cumulative activating based on the remaining charge, temperature, and actual current of the battery at the current sampling time, and the maximum cell voltage at the current sampling time and N sampling times prior to the current sampling time, wherein two adjacent sampling times are spaced apart by a fixed sampling period; and determine a predicted voltage of the maximum cell voltage at the future time based on the maximum cell voltage at the current sampling time and the voltage rise.

[0007] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0008] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0009] Figure 1 A flowchart of the method disclosed herein for predicting the maximum cell voltage of a battery during use is shown;

[0010] Figure 2 An example of a trend in the rate of voltage rise that can be applied to one embodiment of this disclosure is shown.

[0011] Figure 3 An example of a trend in the rate of voltage rise that can be applied to one embodiment of this disclosure is shown.

[0012] Figure 4 An example of a trend in the rate of voltage rise that can be applied to one embodiment of this disclosure is shown.

[0013] Figure 5 A more detailed flowchart of the method disclosed herein for predicting the maximum cell voltage of a battery during use is shown.

[0014] Figure 6 A flowchart of a method for calculating more accurate ohmic impedance according to an embodiment of the present disclosure is shown. Detailed Implementation

[0015] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0017] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0018] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0019] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0020] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0021] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0022] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0023] During the use of power batteries, various properties need to be monitored to ensure battery safety. One useful property is the battery terminal voltage, i.e., the maximum cell voltage. The battery terminal voltage can be used to define the permissible charging and discharging cutoff voltages, providing information to determine the battery's operating limits and prevent overcharging. Predicting voltage rise trends and estimating the state of power based on these predictions helps address overvoltage issues in power batteries.

[0024] Batteries exhibit three polarization relationships: ohmic polarization, concentration polarization, and electrochemical polarization. Ohmic polarization is directly proportional to the battery current; while concentration polarization and electrochemical polarization are related to the electrochemical reactions within the battery. For example, during actual braking or coasting in an electric vehicle, battery polarization causes a voltage increase. Voltage prediction requires calculating the voltage rise caused by the three polarization relationships. The calculations for concentration polarization and electrochemical polarization are complex and require experimental parameter measurements, making real-time calculations impossible within a battery management system.

[0025] In order to predict the maximum cell voltage of a battery in real time, simply and efficiently during use, the inventors of this application propose to predict the maximum cell voltage at future moments based on the historical voltage rise of the maximum cell voltage.

[0026] In one embodiment, this disclosure provides a method 100 for predicting the maximum cell voltage of a battery during use. Figure 1 A flowchart of method 100 is shown. (See attached diagram.) Figure 1 As shown, method 100 includes the following steps: obtaining the remaining charge, temperature, maximum cell voltage, and actual current of the battery at the current sampling time (201); predicting the voltage rise of the maximum cell voltage at a future time due to accumulation optimization based on the remaining charge, temperature, and actual current of the battery at the current sampling time, as well as the maximum cell voltage at the current sampling time and N sampling times prior to the current sampling time (202), wherein two adjacent sampling times are separated by a fixed sampling period; and determining the predicted voltage of the maximum cell voltage at a future time based on the maximum cell voltage at the current sampling time and the voltage rise (203).

[0027] In this disclosure, every fixed (unchanging) sampling period t p Perform a single sampling of the battery's remaining charge, temperature, maximum cell voltage, and actual current. Sampling period t p The sampling time can be any suitable length, such as 100ms, 10ms, 1s, etc. The moment of sampling is called the sampling time. Typically, a battery contains several cells, and the maximum cell voltage refers to the highest voltage among all the individual cells in the battery. Voltage rise refers to the increase in the maximum cell voltage.

[0028] Using the above concept, the voltage rise at future times can be predicted based on the historical voltage rise of the maximum cell voltage at one or more previous sampling times. This allows for real-time, simple, and efficient prediction of the maximum cell voltage during battery use without the need to establish complex prediction models or continuously measure too many battery parameters.

[0029] In one embodiment, the voltage rise includes: a first voltage rise due to ohmic polarization, and a second voltage rise due to concentration polarization and electrochemical polarization. Step 202 includes: predicting the first voltage rise due to ohmic polarization at a future time based on the battery's remaining charge, temperature, and actual current at the current sampling moment; and predicting the second voltage rise due to concentration polarization and electrochemical polarization at a future time based on the maximum cell voltage at the current sampling moment and N sampling moments prior to the current sampling moment.

[0030] In one embodiment, predicting the first voltage rise caused by ohmic polarization at a future time based on the battery's remaining charge, temperature, and actual current at the current sampling time includes: determining the battery's allowable recharge current and ohmic impedance at the current sampling time based on the battery's remaining charge and temperature at the current sampling time; and predicting the first voltage rise caused by ohmic polarization at a future time based on the battery's actual current, allowable recharge current, and ohmic impedance at the current sampling time.

[0031] In one embodiment, the actual current of the battery is a current value with a positive or negative sign, and the first voltage rise ΔV1 is calculated using the following formula:

[0032] ΔV1=(Ip-I)*R0 (a)

[0033] Where "*" represents the multiplication symbol, Ip is the allowable recharge current, I is the actual current of the battery, and R0 is the ohmic impedance of the battery cell. When the actual current is the charging current, I is positive, and when the actual current is the discharging current, I is negative.

[0034] In one embodiment, the ohmic impedance R0 of the battery cell can be calculated by linear lookup table or interpolation based on the battery temperature and remaining charge at the current sampling time.

[0035] In one embodiment, a battery management system is pre-configured with a battery ohm impedance table, which includes the ohmic impedance of the smallest battery cell (e.g., a battery cell) measured at different temperatures and with different remaining charge levels. Based on the remaining charge and temperature of the smallest battery cell at the current sampling time, the ohmic impedance R0 of the smallest battery cell at the current sampling time can be looked up or calculated by linear interpolation or a lookup table.

[0036] In one embodiment, the allowable recharge current Ip can be the battery recharge capability boundary calculated by the battery management system based on the battery's current actual current I and the battery's state parameters.

[0037] In one embodiment, the allowable recharge current Ip can be calculated, looked up in a table, or interpolated from the battery temperature, remaining charge, and predicted voltage of the most recently predicted maximum cell voltage at the current sampling time.

[0038] When the battery is in a controlled current recharge state, the actual current I is less than or equal to the allowable recharge current Ip.

[0039] In one embodiment, predicting the second voltage rise caused by concentration polarization and electrochemical polarization at future times based on the maximum cell voltage at the current sampling time and N sampling times prior to the current sampling time includes: determining the weighted average historical voltage rise at the N sampling times prior to the current sampling time based on the maximum cell voltage at the current sampling time and N sampling times prior to the current sampling time; and predicting the second voltage rise caused by concentration polarization and electrochemical polarization at future times based on the weighted average historical voltage rise at the N sampling times prior to the current sampling time.

[0040] For example, in the scenario of electric vehicles using power batteries, the voltage rise caused by the cumulative polarization of the battery during actual braking or coasting can be predicted based on historical voltage rises. Specifically, the voltage rise is calculated every fixed sampling period (e.g., 100ms). For instance, the voltage rise at each sampling moment relative to the previous sampling moment can be calculated to determine the historical average voltage rise. The calculation method is as follows:

[0041] The voltage rise ΔV between two adjacent sampling times is equal to the maximum cell voltage Vt2 at the nth sampling time, which is the maximum cell voltage Vt1 at the (n-1)th sampling time.

[0042] Under battery recharge conditions, the voltage rise between two adjacent sampling times is greater than or equal to 0; under battery discharge conditions, the voltage rise between two adjacent sampling times is recorded as 0. Only the polarization accumulation effect of the voltage rise during sampling periods (sampling times) where the voltage rise is greater than 0 needs to be considered.

[0043] In various embodiments of this disclosure, the N sampling times preceding the current sampling time are considered historical sampling times. N can be an integer greater than or equal to 1. Therefore, in the above embodiments, method 100 can predict the voltage rise of the maximum cell voltage at future times due to cumulative voltage increases based on the maximum cell voltage at one or more sampling times preceding the current sampling time.

[0044] In different scenarios, battery usage conditions, or different execution states of method 100, N can be different values. That is, the number of previous sampling moments N to be used can be flexibly changed, rather than being fixed. For example, during the execution of method 100, if there is only one accumulated previous sampling moment, or the detection data of the previously accumulated previous sampling moments has been cleared, then N can be 1; if there are only two accumulated previous sampling moments, then N can be 2, and so on.

[0045] For example, when N is 1, the voltage rise between the maximum cell voltage at the current sampling time and the maximum cell voltage at the previous sampling time can be calculated, and it can be assumed that the second voltage rise of the maximum cell voltage in the time period after the current sampling time changes according to the voltage rise (the rate of rise), thereby determining the predicted voltage of the maximum cell voltage at future times.

[0046] For example, when N equals 2, the voltage rise between the maximum cell voltages at the two previous sampling times can be calculated, and it can be assumed that the second voltage rise of the maximum cell voltage in the time period after the current sampling time changes according to the voltage rise (the rate of rise), thereby determining the predicted voltage of the maximum cell voltage at future times.

[0047] Alternatively, for example, when N equals 2, the average or weighted average voltage rise between the voltage rise of the maximum cell voltage at two previous sampling times and between the voltage rise at the current sampling time and the sampling time before the current sampling time can be calculated, and it can be assumed that the second voltage rise of the maximum cell voltage in the time period after the current sampling time varies according to the rise rate of the average or weighted average voltage rise, thereby determining the predicted voltage of the maximum cell voltage at future times.

[0048] For example, when N is 3 or greater, the average voltage rise or weighted average voltage rise between the maximum cell voltages of the 3 or more previous sampling times can be calculated, and it can be assumed that the maximum cell voltage changes according to the rate of rise of the average voltage rise or weighted average voltage rise in the time period after the current sampling time, thereby determining the predicted voltage of the maximum cell voltage at future times.

[0049] In this disclosure, "weighted average voltage rise" can refer to assigning different weights to the average voltage rise at different sampling times under different recharge currents when calculating the average voltage rise.

[0050] For the sake of simplicity, the term "weighted average pressure rise" in this disclosure can encompass both unweighted and weighted average pressure rises. Therefore, "weighted average pressure rise" can encompass the calculation method of directly calculating the average of the N second pressure rises at the N sampling times, i.e.:

[0051] Weighted average pressure rise = Sum of N second pressure rises at N sampling times / N.

[0052] Since only historical pressure rises at sampling times where the pressure rise is greater than 0 need to be considered, the N sampling times do not need to be consecutive. For example, the N sampling times can be completely discontinuous or segmented consecutive.

[0053] In one embodiment, determining the weighted average historical voltage rise of the N sampling times prior to the current sampling time based on the maximum cell voltage at the current sampling time and the N sampling times prior to the current sampling time includes: determining the trend of the voltage rise rate of the maximum cell voltage at the N sampling times based on the maximum cell voltage at the current sampling time and the N sampling times prior to the current sampling time; and determining the weighted average historical voltage rise of the N sampling times prior to the current sampling time based on the trend of the voltage rise rate of the maximum cell voltage at the N sampling times and the calculation method of the weighted average historical voltage rise corresponding to the trend.

[0054] According to the above embodiment, when calculating the average voltage rise of the maximum cell voltage rise at N previous sampling times, the average voltage rise can be calculated in different ways based on the battery operating conditions at these previous sampling times (e.g., the magnitude of the recharge current change).

[0055] For example, in one embodiment, the rate of increase of the maximum cell voltage can reflect the change in the magnitude of the recharge current. For instance, a high rate of increase of the maximum cell voltage typically indicates a high recharge current, while a low rate of increase typically indicates a low recharge current.

[0056] In this disclosure, the magnitude of the rate of rise of the maximum cell voltage and the magnitude of the recharge current are relative concepts that are compared between different sampling times, rather than concepts that are compared with a certain rate threshold or current threshold.

[0057] For example, the scenarios for battery recharging can include: (1) continuous high current recharging; (2) continuous low current recharging; (3) high current recharging followed by low current recharging; (4) low current recharging followed by high current recharging; (5) high current recharging followed by high current recharging after the battery discharges; (6) low current recharging followed by low current recharging after the battery discharges; (7) high current recharging followed by low current recharging after the battery discharges; and (8) low current recharging followed by high current recharging after the battery discharges.

[0058] Because battery polarization is more severe in high-current recharge scenarios, if the battery is first recharged with a high current and then with a low current, the voltage rise generated during the high-current recharge phase must be considered when determining the weighted average historical voltage rise for this recharge scenario. However, if the battery is first recharged with a low current and then with a high current, the voltage rise generated during the low-current recharge phase can be ignored when determining the weighted average historical voltage rise for this discharge scenario. The weighted average historical voltage rise for this recharge scenario can be calculated directly based on the voltage rise generated during the high-current recharge phase (in this case, the average historical voltage rise is calculated only based on the voltage rise generated during the high-current recharge phase, and this calculation does not require assigning different weights to the average voltage rise of different phases). However, for simplicity, in this disclosure, the average voltage rise in this case is still referred to as the "weighted average historical voltage rise" or "weighted average voltage rise").

[0059] In the above embodiments, for example, the following can be defined:

[0060] The voltage rise rate at the nth sampling time = (voltage at the nth sampling time - voltage at the (n-1)th sampling time) / sampling period.

[0061] Based on the trend of this rate of increase, we can determine the current charging scenario of the battery, and then determine the corresponding weighted average historical voltage rise calculation method.

[0062] During the battery's discharge period, the voltage rise is 0, and the discharge process does not generate a second voltage rise due to concentration polarization and electrochemical polarization. Therefore, we only need to consider the second voltage rise caused by concentration polarization and electrochemical polarization during the recharge period (or sampling time, sampling period) when the voltage rise is >0.

[0063] In one embodiment, determining the weighted average historical voltage rise of the N sampling times prior to the current sampling time based on the changing trend of the voltage rise rate of the maximum cell voltage at the N sampling times and the calculation method of the average historical voltage rise corresponding to the changing trend includes:

[0064] If the trend is as follows: in the N sampling times, the voltage rise rate of the maximum cell voltage in consecutive p1 sampling times is greater than the voltage rise rate of the maximum cell voltage in consecutive q1 sampling times, where the sum of p1 and q1 is less than or equal to N, and the consecutive p1 sampling times are prior to the consecutive q1 sampling times, then the weighted average historical voltage rise dV of the N sampling times is expressed by the following formula (a):

[0065] dV=dV1*a+dV2*b (a)

[0066] Wherein, dV1 is the first average historical voltage rise over p1 consecutive sampling times, dV2 is the second average historical voltage rise over q1 consecutive sampling times, a is the weight value of the first average historical voltage rise, b is the weight value of the second average historical voltage rise, and the sum of a and b is 1, where dV1>dV2 and dV2>0.

[0067] For example, Figure 2 An example of the voltage rise rate variation trend to which the above embodiments can be applied is shown. For example... Figure 2 As shown, during battery use, the voltage rise rate initially becomes relatively large ( Figure 2 The left-hand broken line portion shows the average voltage rise at each sampling time as dV1, and then the voltage rise rate becomes smaller ( Figure 2 The right-hand broken line portion shows the average voltage rise at each sampling time as dV2), where dV1>dV2 and dV2>0.

[0068] The average pressure rise over n consecutive sampling times can be calculated using the following formula:

[0069] dV = the sum of the voltage rise at n consecutive sampling times / n.

[0070] Since each sampling period is a time interval of the same length, the larger the dV, the greater the voltage rise rate of the corresponding n consecutive sampling moments (corresponding to n consecutive sampling periods).

[0071] For example, Figure 3 Another example of the voltage rise rate variation trend to which the above embodiments can be applied is shown. For example... Figure 3 As shown, during battery use, the voltage rise rate initially becomes relatively large ( Figure 3 The leftmost broken line portion (average voltage rise at each sampling time is dV1) then the battery enters the discharge state (middle broken line portion), and finally the voltage rise rate becomes smaller ( Figure 3 The rightmost broken line in the diagram represents the average voltage rise at each sampling time (dV2), where dV1 > dV2 > 0. As mentioned above, when the battery enters the discharge state, the voltage rise is recorded as 0, and the cumulative effect of the discharge period on the second voltage rise can be ignored (i.e., concentration polarization and electrochemical polarization caused by the discharge process are not considered).

[0072] In special cases, one or both of p1 and q1 in the above embodiments can be integers 1. That is, a single sampling moment can also be considered as consecutive sampling moments.

[0073] Furthermore, the values ​​of weights a and b can be adjusted based on the values ​​of p1 and q1. For example, in... Figure 2 In the recharge scenario shown, p1 is much larger than q1, so weight a can be set to be much larger than weight b. In one embodiment, in the case of... Figure 2 In the scenario shown, a / b can be set to p1 / q1.

[0074] In one embodiment, determining the weighted average historical voltage rise of the N sampling times prior to the current sampling time based on the changing trend of the voltage rise rate of the maximum cell voltage at the N sampling times and the calculation method of the average historical voltage rise corresponding to the changing trend includes:

[0075] If the trend is as follows: in the N sampling times, the voltage rise rate of the maximum cell voltage in consecutive p2 sampling times is less than or equal to the voltage rise rate of the maximum cell voltage in consecutive q2 sampling times, where the sum of p2 and q2 is less than or equal to N, and the consecutive p2 sampling times are before the consecutive q2 sampling times, then the weighted average historical voltage rise dV of the N sampling times is expressed by the following formula (b):

[0076] dV=dV3 (b)

[0077] Where dV3 is the third average historical voltage rise over q2 consecutive sampling times. Where dV3>dV4>0, dV4 is the fourth average historical voltage rise over p2 consecutive sampling times.

[0078] For example, Figure 4 An example of the voltage rise rate variation trend to which the above embodiments can be applied is shown. For example... Figure 4As shown, the voltage rise rate is initially relatively small during battery use. Figure 4 The left-hand broken line portion shows the average voltage rise at each sampling time as dV4, then the voltage rise rate becomes larger ( Figure 4 The right-hand broken line represents the average voltage rise at each sampling time (dV3), where dV3 > dV4 > 0. In this case, we can consider only the voltage rise generated during the most recent high-current recharge phase.

[0079] Based on the above considerations, the voltage rise rate trends corresponding to the above 8 battery recharge scenarios can be divided into two cases, and the weighted average historical voltage rise dV can be calculated by using the above formulas (a) and (b) respectively.

[0080] In one embodiment, method 100 may further include: adjusting the allowable recharge current of the battery in real time based on a predicted voltage V of the maximum cell voltage at a future time.

[0081] For example, the second pressure rise t seconds after the current moment can be predicted using the following formula:

[0082] V2=dV*t / t p

[0083] Where V2 is the second pressure rise after t seconds, dV is the weighted average historical pressure rise dV of the second pressure rise, and t p It is the sampling period.

[0084] The predicted voltage V of the maximum cell voltage t seconds after the current moment can be predicted using the following formula:

[0085] V = Vmax + ΔV1 + V2

[0086] Where Vmax is the maximum cell voltage at the current sampling moment, ΔV1 is the first voltage rise, and V2 is the second voltage rise after t seconds.

[0087] In one embodiment, method 100 may further include: adjusting the allowable recharge power of the battery in real time based on a predicted voltage V of the maximum cell voltage at a future time.

[0088] Figure 5 A more complete flowchart of the method 100 described above is shown, in which V1 is the first pressure rise ΔV1 mentioned above.

[0089] According to the prediction method disclosed herein, the maximum cell voltage at future times can be predicted directly based on the historical voltage rise of the maximum cell voltage without relying on a battery model, without establishing a machine learning algorithm, and without training the machine learning model. Therefore, a real-time, simple, and efficient method for predicting the maximum cell voltage of a battery during use is provided.

[0090] In one embodiment, this disclosure provides a computer program product including computer-executable instructions that, when executed by one or more processors, cause one or more processors to perform the method 100 as described above.

[0091] In one embodiment, this disclosure provides a battery management system including a processor for managing a battery, the processor being configured to: receive the remaining charge, temperature, maximum cell voltage, and actual current of the battery at the current sampling time; predict the voltage rise of the maximum cell voltage at a future time due to cumulative activating based on the remaining charge, temperature, and actual current of the battery at the current sampling time, and the maximum cell voltage at the current sampling time and N sampling times prior to the current sampling time, wherein two adjacent sampling times are spaced apart by a fixed sampling period; and determine the predicted voltage of the maximum cell voltage at a future time based on the maximum cell voltage at the current sampling time and the voltage rise.

[0092] In one embodiment, the voltage rise includes: a first voltage rise due to ohmic polarization, and a second voltage rise due to concentration polarization and electrochemical polarization; the processor is further configured to: predict the first voltage rise due to ohmic polarization at a future time based on the remaining charge, temperature, and actual current of the battery at the current sampling time; and predict the second voltage rise due to concentration polarization and electrochemical polarization at a future time based on the maximum cell voltage at the current sampling time and N sampling times prior to the current sampling time.

[0093] In one embodiment, the processor is further configured to: determine the allowable recharge current and ohmic impedance of the battery at the current sampling time based on the remaining charge and temperature of the battery at the current sampling time; and predict the first voltage rise caused by ohmic polarization at a future time based on the actual current, allowable recharge current and ohmic impedance of the battery at the current sampling time.

[0094] In one embodiment, the actual current is a sign-positive current value, and the first voltage rise ΔV1 is calculated using the following formula (a):

[0095] ΔV1=(Ip-I)*R0 (a)

[0096] Where Ip is the allowable recharge current, I is the actual current of the battery, and R0 is the ohmic impedance. When the actual current is the charging current, I is positive, and when the actual current is the discharging current, I is negative.

[0097] In one embodiment, the processor is further configured to: determine the weighted average historical voltage rise of the N sampling times prior to the current sampling time based on the maximum cell voltage of the current sampling time and the N sampling times prior to the current sampling time; and predict a second voltage rise in the future caused by concentration polarization and electrochemical polarization based on the weighted average historical voltage rise of the N sampling times prior to the current sampling time.

[0098] In one embodiment, the processor is further configured to: determine the voltage rise rate trend of the maximum cell voltage at the N sampling times based on the current sampling time and the maximum cell voltage at the N sampling times prior to the current sampling time; and determine the weighted average historical voltage rise at the N sampling times prior to the current sampling time based on the voltage rise rate trend of the maximum cell voltage at the N sampling times and the calculation method of the weighted average historical voltage rise corresponding to the trend.

[0099] In one embodiment, the processor is further configured to: if the trend is that, in the N sampling times, the voltage rise rate of the maximum cell voltage for consecutive p1 sampling times is greater than the voltage rise rate of the maximum cell voltage for consecutive q1 sampling times, where the sum of p1 and q1 is less than or equal to N, and the consecutive p1 sampling times precede the consecutive q1 sampling times, then the weighted average historical voltage rise dV for the N sampling times is expressed by the following formula:

[0100] dV = dV1*a + dV2*b

[0101] Where dV1 is the first average historical voltage rise over p1 consecutive sampling times, dV2 is the second average historical voltage rise over q1 consecutive sampling times, a is the weight value of the first average historical voltage rise, b is the weight value of the second average historical voltage rise, and the sum of a and b is 1.

[0102] In one embodiment, the processor is further configured to: if the trend is: in the N sampling times, the voltage rise rate of the maximum cell voltage for a consecutive p2 sampling times is less than or equal to the voltage rise rate of the maximum cell voltage for a consecutive q2 sampling times, where the sum of p2 and q2 is less than or equal to N, and the consecutive p2 sampling times are prior to the consecutive q2 sampling times, then the weighted average historical voltage rise dV for the N sampling times is expressed by the following formula:

[0103] dV=dV3

[0104] Wherein, dV3 is the third average historical pressure rise over q2 consecutive sampling times.

[0105] In one embodiment, the processor is further configured to adjust the allowable recharge current of the battery in real time based on the predicted maximum cell voltage.

[0106] In one embodiment, the processor is further configured to adjust the allowable recharge power of the battery in real time based on the predicted maximum cell voltage.

[0107] This disclosure predicts the voltage rise caused by cumulative charging based on the historical upward trend of the maximum cell voltage, thereby obtaining the predicted maximum cell voltage of the battery. This provides an effective basis for the battery management system to adjust the current allowable recharge power and allowable recharge current, preventing the battery from continuously recharging at a power or current exceeding its actual capacity. Furthermore, real-time adjustment of output power by predicting the voltage can also avoid overvoltage problems that occur when the cumulative charging voltage of the battery is sufficiently large due to continuous low-current recharging.

[0108] In the methods and battery management systems described above, the cell ohmic impedance R0 is obtained by looking up and / or interpolating the ohmic impedance table based on the battery temperature and remaining charge at the current sampling time.

[0109] In another embodiment, in order to improve the accuracy of the ohmic impedance, a more accurate real-time updated ohmic impedance table can be calculated as follows, and the ohmic impedance R0 in formula (a) can be obtained by looking up the table and / or interpolating using the ohmic impedance table (hereinafter referred to as the updated ohmic impedance table).

[0110] In one embodiment, the method further includes: if, in the T sampling times prior to the current sampling time, the actual current of the battery has consistently been the charging current, and the absolute value of the actual current has consistently increased with the gradient of the increase within a predetermined range, then I is determined to be... T -I0 is greater than the first current threshold; and if I T If -I0 is greater than the first current threshold, then the updated ohmic impedance is determined based on a pre-determined conversion coefficient that varies with the product T*C, and this ohmic impedance is used to update the ohmic impedance value at the corresponding remaining charge and temperature in the ohmic impedance table in real time, where T is an integer greater than or equal to 2, I... T I0 represents the actual current at the current sampling moment, IT represents the actual current at the Tth sampling moment prior to the current sampling moment, and C is the sampling period (e.g., 100ms).

[0111] "The absolute value of the actual current is always increasing and the gradient of the increase is within a predetermined range" means that the value of the charging current is always increasing and is increasing in an approximately linear manner.

[0112] For example, if the following formula (b) is satisfied, then the increasing gradient is within a predetermined range:

[0113] 0.95*(I n-1 -I n-2 ) < (I n -I n-1 ) < 1.05*(I n-1 -I n-2 (b).

[0114] Among them, I n Let I represent the actual current at the nth sampling time, and so on. The actual current at the current sampling time can be expressed as I. T The actual current at the Tth sampling time prior to the current sampling time can be represented as I0.

[0115] As an example, the first current threshold could be 0.3C. 1C represents the current value when the battery is fully discharged in one hour. The first current threshold can be a current value smaller or larger than 0.3C. Note that C here is a different concept from the sampling period mentioned above.

[0116] Formula (b) above can also be rewritten as formula (c):

[0117] 0.95 < (I n -I n-1 ) / (I n-1 -I n-2 <1.05(c).

[0118] Among them, (I) n -I n-1 ) / (I n-1 -I n-2 This represents the increasing gradient of the actual current at the nth sampling time. If the increasing gradient remains within a predetermined range (e.g., 0.95 to 1.05), the actual current can be considered to increase linearly. Of course, the predetermined range is not limited to the example above, but can be any other suitable range.

[0119] In one embodiment, T can be 10, or a larger or smaller integer.

[0120] In one embodiment, I0 is less than a second current threshold, which is less than a first current threshold. In one embodiment, the first current threshold may be 0.1C, or a current value smaller or larger than 0.1C. In one embodiment, I0 is small enough that the actual current can be approximated as a zero current state, thereby providing a near-polarization pre-state.

[0121] In one embodiment, in the T sampling times preceding the current sampling time, the fluctuation rates of both the remaining battery charge and the battery temperature are less than a predetermined percentage. The fluctuation rate is a percentage change. This percentage is, for example, 1%, but can also be a smaller or larger percentage.

[0122] Figure 6 A flowchart illustrating a method for calculating more accurate ohmic impedance according to an embodiment of this disclosure is shown. It should be emphasized that... Figure 6 The examples shown are merely illustrative and many of the steps are not necessary and can be skipped.

[0123] First, the initial ohmic impedance R0 at different temperatures and different SOCs can be output based on the measured data of the battery cell. This initial ohmic impedance R0 is the R0 in formula (a) as described above, and the calculation method is also as described above.

[0124] Then, as an optional prerequisite (1), when the actual SOC and temperature of the battery are respectively at SOC±SOC a Interval sum Temp ± Temp a Within the interval (where SOC) a and Temp a (Values ​​entered to account for allowable deviations in SOC and temperature) will then proceed to the following calculation flow.

[0125] In one embodiment, SOC a =SOC * 1%, which means that the remaining power SOC fluctuates within a predetermined percentage of 1% (i.e., a volatility of 1%). Similarly, in one embodiment, Temp... a =Temp * 1%, which means that the temperature Temp fluctuates within a predetermined percentage of 1% (1% volatility). The predetermined percentage can be any other suitable percentage.

[0126] Then, as an optional prerequisite (2), if the absolute value of the current actual current is less than Ia (Ia is typically 0.1C, i.e., near-zero current state, to provide a near-polarization precondition), the following calculation process begins. Ia is the second current threshold, which can be other smaller or larger values.

[0127] Then, proceed to the process of calculating a more accurate ohmic impedance. At this point, let n = 0, the current be I0, and the voltage be V0. Note that the prerequisites (1) and (2) above are optional, so conditions (1) and (2) can be skipped and the process of calculating a more accurate ohmic impedance can be directly entered.

[0128] In this process, n is incremented by 1 after each sample (e.g., the sampling period C can be 100ms). The process continues until the absolute value of the current actual current is greater than the absolute value of the actual current at the previous sampling time (i.e., I0). n Greater than I n-1 (That is, the absolute value of the actual current is increasing), and the upward trend of the actual current approaches linearity (i.e., for example, 0.95*(I n-1 -I n-2 ) < (I n -I n-1 )<

[0129] 1.05*(I n-1 -I n-2 Given that the actual current is always the recharge current and n accumulates to T, calculate the DCR(T) at the current sampling time T (the Tth period):

[0130] DCR(T)=ΔU / ΔI①.

[0131] Where T is an integer greater than or equal to 2. In one embodiment, for example, T is 10. The range of 0.95 to 1.05 above is an example of a predetermined range for the increasing gradient; other suitable gradient ranges may be used. ΔU represents the increment of the battery's maximum cell voltage from the start sampling time (sampling time 0) T sampling times ago to the current sampling time (sampling time T).

[0132] ΔI represents the increment of the actual current from the start sampling time (sampling time 0) T sampling times ago to the current sampling time (sampling time T).

[0133] Based on experimental patterns, the following formula can be summarized.

[0134] DCR(1) / DCR0(1)=Conversion coefficient*DCR(T) / DCR0(T)②.

[0135] When C is 0.1s, the above ② can also be expressed as:

[0136] DCR(0.1s) / DCR0(0.1s)=Ratio*DCR(T) / DCR0(T)②.

[0137] That is, DCR(1) and DCR(0.1s) both represent the updated ohmic impedance at n=1 (i.e., the first sampling time); DCR0(1) and DCR0(0.1s) both represent the ohmic impedance R0 at n=1 (i.e., the first sampling time), and DCR0 is the R0 in formula (a) above. DCR0(T) represents the ohmic impedance R0 at n=T (the Tth sampling time), that is, the R0 in formula (a) above. That is, the values ​​of DCR0(1) and DCR0(T), as well as the values ​​of DCR0 at other sampling times, can be obtained by interpolation after looking up the table according to the method described above for R0.

[0138] In section ② above, "Ratio" represents the conversion coefficient. A one-dimensional table [Time, Conversion Coefficient Ratio] can be created based on experiments. The time in this table represents the recharge duration, which can be calculated using T*C (T multiplied by the sampling period (e.g., 100ms)). Based on this one-dimensional table, the conversion coefficient Ratio can be obtained by looking up T*C.

[0139] Based on ① and ② above, we can obtain DCR(1) when n=1.

[0140] Next, determine I T Is -I0 greater than Ib, when I T When -I0 is greater than Ib, then calculate DCR:

[0141] DCR = weighting coefficient w1 * DCR(1) + weighting coefficient w2 * DCR0(1)(d)

[0142] The actual current at the current sampling moment can be expressed as I. T The actual current at the Tth sampling time before the current sampling time (i.e., when n=0) can be represented as I0. Ib is the first current threshold, for example, Ib can be 0.3C, or other larger or smaller current values.

[0143] In one embodiment, the weighting coefficients w1 and w2 in the above formula can be determined based on the experimental results of experiments conducted on the battery. In one embodiment, the sum of w1 and w2 equals 1.

[0144] Finally, the DCR calculated above can be used as the ohmic impedance at the current SOC and temperature at the current sampling time T. That is, the DCR can be used to update the ohmic impedance values ​​at the corresponding SOC and temperature in the ohmic impedance table in real time, so as to obtain a more accurate and real-time ohmic impedance R0 based on the updated ohmic impedance table, thereby improving the calculation accuracy of the first voltage rise.

[0145] Notice, Figure 6The flowchart is drawn as an example with a sampling period of 100ms, so 0.1s represents the value in the first sampling period (i.e., n=1).

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for predicting the maximum cell voltage of a battery during use, characterized in that, include: Obtain the remaining battery charge, temperature, maximum cell voltage, and actual current at the current sampling time; Based on the remaining charge, temperature, and actual current of the battery at the current sampling time, and the maximum cell voltage at the current sampling time and N sampling times prior to the current sampling time, the voltage rise of the maximum cell voltage at future times due to cumulative accumulator optimization is predicted, wherein two adjacent sampling times are separated by a fixed sampling period. as well as Based on the maximum cell voltage and voltage rise at the current sampling time, the predicted voltage of the maximum cell voltage at the future time is determined.

2. The method as described in claim 1, characterized in that, The pressure rise includes: a first pressure rise due to ohmic polarization, and a second pressure rise due to concentration polarization and electrochemical polarization; The method of predicting the voltage rise caused by cumulative cell optimization in future moments based on the remaining charge, temperature, and actual current of the battery at the current sampling moment, and the maximum cell voltage at the current sampling moment and N sampling moments prior to the current sampling moment, includes: Based on the remaining charge, temperature, and actual current of the battery at the current sampling time, predict the first voltage rise caused by ohmic polarization at a future time; Based on the maximum cell voltage at the current sampling time and the N sampling times prior to the current sampling time, predict the second voltage rise caused by concentration polarization and electrochemical polarization at future times.

3. The method as described in claim 2, characterized in that, The step of predicting the first voltage rise caused by ohmic polarization at a future time based on the remaining charge, temperature, and actual current of the battery at the current sampling moment includes: Based on the remaining charge and temperature of the battery at the current sampling time, determine the allowable recharge current and ohmic impedance of the battery at the current sampling time; Based on the actual current of the battery at the current sampling time, the allowable recharge current, and the ohmic impedance, predict the first voltage rise caused by ohmic polarization at a future time.

4. The method as described in claim 3, characterized in that, The actual current is a current value with a positive or negative sign, and the first voltage rise is calculated using the following formula: ΔV1=(Ip-I)*R0 (a) Wherein, ΔV1 is the first voltage rise, Ip is the allowable recharge current, I is the actual current of the battery, and R0 is the ohmic impedance. R0 is obtained by looking up and / or interpolating the ohmic impedance table using the remaining charge and temperature of the battery. When the actual current is the charging current, I is positive, and when the actual current is the discharging current, I is negative.

5. The method as described in claim 4, characterized in that, Also includes: If, in the T sampling times preceding the current sampling time, the actual current has consistently been the charging current, and the absolute value of the actual current has consistently increased with the gradient of this increase within a predetermined range, then I is determined to be... T -I0 is greater than the first current threshold; as well as If I T If -I0 is greater than the first current threshold, then the updated ohmic impedance is determined based on a pre-determined conversion coefficient that varies with the product T*C, and this ohmic impedance is used to update the ohmic impedance value at the corresponding remaining charge and temperature in the ohmic impedance table in real time. Where T is an integer greater than or equal to 2, I T I0 represents the actual current at the current sampling moment, IT represents the actual current at the Tth sampling moment before the current sampling moment, and C is the sampling period.

6. The method as described in claim 5, characterized in that, I0 is less than the second current threshold, and the second current threshold is less than the first current threshold.

7. The method as described in claim 5, characterized in that, In the T sampling times prior to the current sampling time, the fluctuation rate of the remaining battery charge and the fluctuation rate of the battery temperature are both less than a predetermined percentage.

8. The method as described in claim 2, characterized in that, The step of predicting the second voltage rise caused by concentration polarization and electrochemical polarization at future times based on the maximum cell voltage at the current sampling time and N sampling times prior to the current sampling time includes: Based on the maximum cell voltage at the current sampling time and the N sampling times prior to the current sampling time, determine the weighted average historical voltage rise at the N sampling times prior to the current sampling time; Based on the weighted average historical pressure rise of N sampling times prior to the current sampling time, the second pressure rise caused by concentration polarization and electrochemical polarization at future times is predicted.

9. The method as described in claim 8, characterized in that, The step of determining the weighted average historical voltage rise of the N sampling times prior to the current sampling time based on the maximum cell voltage at the current sampling time and the N sampling times prior to the current sampling time includes: Based on the maximum cell voltage at the current sampling time and the N sampling times prior to the current sampling time, determine the trend of the voltage rise rate of the maximum cell voltage at the N sampling times; Based on the changing trend of the voltage rise rate of the maximum cell voltage at the N sampling times and the calculation method of the weighted average historical voltage rise corresponding to the changing trend, the weighted average historical voltage rise of the N sampling times before the current sampling time is determined.

10. The method as described in claim 9, characterized in that, The step of determining the weighted average historical voltage rise of the N sampling times prior to the current sampling time based on the changing trend of the voltage rise rate of the maximum cell voltage at the N sampling times and the calculation method of the weighted average historical voltage rise corresponding to the changing trend includes: If the trend is as follows: in the N sampling times, the voltage rise rate of the maximum cell voltage for p1 consecutive sampling times is greater than the voltage rise rate of the maximum cell voltage for q1 consecutive sampling times, where the sum of p1 and q1 is less than or equal to N, and the p1 consecutive sampling times are prior to the q1 consecutive sampling times, then the weighted average historical voltage rise dV for the N sampling times is expressed by the following formula: dV = dV1*a + dV2*b Wherein, dV1 is the first average historical voltage rise over p1 consecutive sampling times, dV2 is the second average historical voltage rise over q1 consecutive sampling times, a is the weight value of the first average historical voltage rise, b is the weight value of the second average historical voltage rise, and the sum of a and b is 1.

11. The method as described in claim 9, characterized in that, The step of determining the weighted average historical voltage rise of the N sampling times prior to the current sampling time based on the changing trend of the voltage rise rate of the maximum cell voltage at the N sampling times and the calculation method of the weighted average historical voltage rise corresponding to the changing trend includes: If the trend is as follows: in the N sampling times, the voltage rise rate of the maximum cell voltage for p2 consecutive sampling times is less than or equal to the voltage rise rate of the maximum cell voltage for q2 consecutive sampling times, where the sum of p2 and q2 is less than or equal to N, and the p2 consecutive sampling times are prior to the q2 consecutive sampling times, then the weighted average historical voltage rise dV for the N sampling times is expressed by the following formula: dV=dV3 Wherein, dV3 is the third average historical pressure rise over q2 consecutive sampling times.

12. The method according to claim 1 or 2, further comprising: The allowable recharge current of the battery is adjusted in real time based on the predicted voltage.

13. The method according to claim 1 or 2, further comprising: The allowable recharge power of the battery is adjusted in real time based on the predicted voltage.

14. A computer program product comprising computer-executable instructions, which, when executed by one or more processors, cause the one or more processors to perform the method according to any one of claims 1 to 13.

15. A battery management system including a processor for managing a battery, the processor being configured to: Receive the battery's remaining charge, temperature, maximum cell voltage, and actual current at the current sampling time; Based on the remaining battery capacity, temperature, and actual current at the current sampling time, and the maximum cell voltage at the current sampling time and N sampling times prior to the current sampling time, predict the voltage rise of the maximum cell voltage at future times due to cumulative voltammetry, wherein adjacent sampling times are separated by a fixed sampling period; and Based on the maximum cell voltage and voltage rise at the current sampling time, the predicted voltage of the maximum cell voltage at the future time is determined.

Images