Method for charging a power battery and battery management system

Abstract

This application provides a method for charging a power battery and a battery management system, which can effectively improve the charging speed of the power battery while ensuring its safety performance. The method for charging a power battery, applied to a battery management system, includes: determining a negative electrode potential safety threshold based on battery state parameters, wherein the battery state parameters include at least one of the power battery's state of charge (SOC), temperature, and state of health (SOH); and adjusting the charging request current of the power battery based on the negative electrode potential and the negative electrode potential safety threshold during the charging process.

Description

Technical Field

[0001] This application relates to the field of power batteries, and in particular to a method for charging a power battery and a battery management system. Background Technology

[0002] With the development of the times, electric vehicles have huge market prospects due to their advantages such as high environmental friendliness, low noise, and low operating costs. They can also effectively promote energy conservation and emission reduction, which is beneficial to social development and progress.

[0003] Currently, consumers have increasingly higher demands for the charging speed of electric vehicles. However, as charging speeds increase, the safety performance of electric vehicle batteries may be affected. Battery technology, especially battery safety, is a crucial factor in the development of electric vehicles and related fields, influencing the development and application of battery-related products and public acceptance of electric vehicles. Therefore, balancing battery charging speed and safety performance is a pressing issue that needs to be addressed. Summary of the Invention

[0004] This application provides a method for charging a power battery and a battery management system, which can effectively improve the charging speed of the power battery while ensuring its safety performance.

[0005] In a first aspect, a method for charging a power battery is provided, applied to a battery management system (BMS) of the power battery. The method includes: determining a negative electrode potential safety threshold based on battery state parameters of the power battery, wherein the battery state parameters include at least one of the power battery's state of charge (SOC), temperature, and state of health (SOH); and adjusting the charging request current of the power battery based on the negative electrode potential of the power battery and the negative electrode potential safety threshold during the charging process.

[0006] Since the risk of lithium plating in a power battery is closely related to its own battery state parameters, the above-mentioned technical solution determines the negative electrode potential safety threshold based on the battery state parameters. This makes the determined negative electrode potential safety threshold more accurate and closer to the critical potential for lithium plating in the power battery. Thus, adjusting the charging request current of the power battery based on the determined negative electrode potential safety threshold and the negative electrode potential not only ensures the safety performance of the power battery but also improves its charging speed.

[0007] In some possible implementations, adjusting the charging request current of the power battery based on the negative electrode potential and the negative electrode potential safety threshold includes: if the negative electrode potential drops to the negative electrode potential safety threshold, adjusting the charging request current from a first charging request current to a second charging request current, wherein the second charging request current is less than the first charging request current.

[0008] The above technical solution indicates that when the negative electrode potential of the power battery drops to the safe threshold of the negative electrode potential, it means that the power battery may be about to experience lithium plating. In this case, reducing the charging request current of the power battery can avoid safety problems caused by lithium ion accumulation, such as battery combustion or explosion, thereby ensuring the safety performance of the power battery.

[0009] In some possible implementations, adjusting the charging request current of the power battery based on the negative electrode potential and the negative electrode potential safety threshold includes: if the negative electrode potential has not dropped to the negative electrode potential safety threshold and the charging duration of the power battery is greater than the time threshold, adjusting the charging request current from a first charging request current to a third charging request current, wherein the third charging request current is greater than the first charging request current.

[0010] If the negative electrode potential of the power battery fails to drop to the safe threshold for an extended period, it indicates that the current charging current of the power battery is too low. In this case, increasing the charging request current of the power battery can improve the charging speed, significantly reduce the charging time, and thus improve the user experience.

[0011] In some possible implementations, when the SOC of the power battery is in a first SOC range, the negative electrode potential safety threshold is a first preset negative electrode potential safety threshold; when the SOC of the power battery is in a second SOC range, the negative electrode potential safety threshold is a second preset negative electrode potential safety threshold; wherein, the SOC in the first SOC range is less than the SOC in the second SOC range, and the first preset negative electrode potential safety threshold is less than the second preset negative electrode potential safety threshold.

[0012] The higher the state of charge (SOC) of a power battery, the higher the risk of lithium plating. On one hand, the aforementioned technical solution sets a relatively high safety threshold for the negative electrode potential of power batteries with high lithium plating risk, effectively suppressing this risk and improving battery safety. On the other hand, the aforementioned technical solution sets a relatively low safety threshold for the negative electrode potential of power batteries with low lithium plating risk, ensuring charging speed without compromising battery safety.

[0013] In some possible implementations, when the temperature of the power battery is in a first temperature range, the negative electrode potential safety threshold is a third preset negative electrode potential safety threshold; when the temperature of the power battery is in a second temperature range, the negative electrode potential safety threshold is a fourth preset negative electrode potential safety threshold; wherein, the temperature in the first temperature range is lower than the temperature in the second temperature range, and the third preset negative electrode potential safety threshold is greater than the fourth preset negative electrode potential safety threshold.

[0014] Since the lower the temperature of a power battery, the higher the risk of lithium plating, the above-mentioned technical solution sets a relatively high safety threshold for the negative electrode potential of power batteries with high lithium plating risk. This effectively suppresses the risk of lithium plating and improves the safety performance of the power battery. On the other hand, the above-mentioned technical solution sets a relatively low safety threshold for the negative electrode potential of power batteries with low lithium plating risk, ensuring the charging speed of the power battery without affecting its safety performance.

[0015] In some possible implementations, when the SOH of the power battery is in the first SOH range, the negative electrode potential safety threshold is a fifth preset negative electrode potential safety threshold; when the SOH of the power battery is in the second SOH range, the negative electrode potential safety threshold is a sixth preset negative electrode potential safety threshold; wherein, the SOH in the first SOH range is less than the SOH in the second SOH range, and the fifth preset negative electrode potential safety threshold is greater than the sixth preset negative electrode potential safety threshold.

[0016] Since a lower state of equilibrium (SOH) of a power battery increases the risk of lithium plating, the aforementioned technical solution sets a relatively high safety threshold for the negative electrode potential of power batteries with high lithium plating risk. This effectively suppresses the risk of lithium plating and improves the safety performance of the power battery. Conversely, the solution sets a relatively low safety threshold for the negative electrode potential of power batteries with low lithium plating risk, ensuring the charging speed of the power battery without compromising its safety performance.

[0017] In some possible implementations, the battery state parameters of the power battery are the same as the battery state parameters before charging.

[0018] The above technical solution allows the Battery Management System (BMS) to determine the battery state parameters before charging, meaning the BMS can determine the negative electrode potential safety threshold before charging begins. Thus, from the moment charging starts, the BMS can adjust the charging request current based on the negative electrode potential safety threshold, enabling it to adjust the charging request current throughout the entire charging process. This further ensures battery safety and improves charging speed.

[0019] In some possible implementations, the battery state parameters of the power battery are the battery state parameters during the charging process of the power battery.

[0020] In the above technical solution, the BMS determines the battery state parameters of the power battery during the charging process. Since the battery state parameters of the power battery may change continuously during the charging process, the determined battery state parameters may be the parameters that are closest to the actual battery state parameters of the power battery at the current moment, so that the negative electrode potential safety threshold determined by the BMS based on the latest battery state parameters of the power battery is more accurate.

[0021] Secondly, a battery management system for a power battery is provided, comprising: a determining unit, configured to determine a negative electrode potential safety threshold based on battery state parameters of the power battery, wherein the battery state parameters include at least one of the power battery's state of charge (SOC), temperature, and state of health (SOH); and an adjusting unit, configured to adjust the charging request current of the power battery during charging, based on the negative electrode potential of the power battery and the negative electrode potential safety threshold.

[0022] In some possible implementations, the adjustment unit is specifically used to: if the negative electrode potential drops to the negative electrode potential safety threshold, adjust the charging request current from the first charging request current to the second charging request current, wherein the second charging request current is less than the first charging request current.

[0023] In some possible implementations, the adjustment unit is specifically used to: if the negative electrode potential does not drop to the negative electrode potential safety threshold and the charging time of the power battery is greater than the time threshold, adjust the charging request current from the first charging request current to the third charging request current, wherein the third charging request current is greater than the first charging request current.

[0024] In some possible implementations, the characteristic is that when the SOC of the power battery is in a first SOC range, the negative electrode potential safety threshold is a first preset negative electrode potential safety threshold; when the SOC of the power battery is in a second SOC range, the negative electrode potential safety threshold is a second preset negative electrode potential safety threshold; wherein, the SOC in the first SOC range is less than the SOC in the second SOC range, and the first preset negative electrode potential safety threshold is less than the second preset negative electrode potential safety threshold.

[0025] In some possible implementations, when the temperature of the power battery is in a first temperature range, the negative electrode potential safety threshold is a third preset negative electrode potential safety threshold; when the temperature of the power battery is in a second temperature range, the negative electrode potential safety threshold is a fourth preset negative electrode potential safety threshold; wherein, the temperature in the first temperature range is lower than the temperature in the second temperature range, and the third preset negative electrode potential safety threshold is greater than the fourth preset negative electrode potential safety threshold.

[0026] In some possible implementations, when the SOH of the power battery is in the first SOH range, the negative electrode potential safety threshold is a fifth preset negative electrode potential safety threshold; when the SOH of the power battery is in the second SOH range, the negative electrode potential safety threshold is a sixth preset negative electrode potential safety threshold; wherein, the SOH in the first SOH range is less than the SOH in the second SOH range, and the fifth preset negative electrode potential safety threshold is greater than the sixth preset negative electrode potential safety threshold.

[0027] In some possible implementations, the battery state parameters of the power battery are the same as the battery state parameters before charging.

[0028] In some possible implementations, the battery state parameters of the power battery are the battery state parameters during the charging process of the power battery.

[0029] Thirdly, a battery management system (BMS) for a power battery is provided, comprising: a memory for storing a program; and a processor for executing the program stored in the memory. When the program stored in the memory is executed, the processor is used to execute the methods described in the first aspect or its various implementations. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0031] Figure 1 This is an architectural diagram of a charging system applicable to an embodiment of this application.

[0032] Figure 2 This is a schematic diagram of a power battery charging method according to an embodiment of this application.

[0033] Figure 3 This is a schematic diagram of a hierarchical first-order RC equivalent circuit model according to an embodiment of this application.

[0034] Figure 4 This is a schematic flowchart of a method for charging a power battery according to an embodiment of this application.

[0035] Figure 5 This is a schematic block diagram of the BMS according to an embodiment of this application.

[0036] Figure 6 This is a schematic block diagram of the BMS according to an embodiment of this application. Detailed Implementation

[0037] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0038] In the description of this application, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," etc., indicating orientation or positional relationships are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0039] In the field of new energy, power batteries serve as the primary power source for electrical devices (such as vehicles, ships, or spacecraft). Currently, most power batteries on the market are rechargeable batteries, the most common being lithium batteries, such as lithium-ion batteries or lithium-ion polymer batteries. During charging, power batteries are generally charged using a continuous charging method. However, continuous charging can cause phenomena such as lithium plating and overheating in the power battery. These phenomena not only degrade the performance of the power battery and significantly shorten its cycle life, but also limit its fast-charging capacity and may potentially lead to catastrophic consequences such as combustion and explosion, causing serious safety problems.

[0040] Reducing the charging current during the charging process is a highly effective way to ensure the safety performance of power batteries. However, consumers now have increasingly higher demands for the charging speed of power batteries. Simply reducing the charging current to ensure battery safety would result in slower charging speeds and negatively impact the user experience.

[0041] In view of this, this application proposes a new method for charging power batteries that can balance the charging speed and safety performance of power batteries, that is, it can effectively improve the charging speed of power batteries while ensuring the safety performance of power batteries.

[0042] Figure 1 An architecture diagram of a charging system applicable to an embodiment of this application is shown.

[0043] like Figure 1 As shown, the charging system 100 may include a charging device 110 and a battery system 120. Optionally, the battery system 120 may be a battery system in an electric vehicle (including pure electric vehicles and plug-in hybrid electric vehicles) or a battery system in other application scenarios.

[0044] Optionally, the battery system 120 may include at least one battery pack, which can be collectively referred to as the power battery 121. In terms of battery type, the power battery 121 can be any type of battery, including but not limited to: lithium-ion batteries, lithium metal batteries, lithium-sulfur batteries, lead-acid batteries, nickel-metal hydride batteries, or lithium-air batteries, etc. In terms of battery size, the power battery 121 in this embodiment can be a cell, a battery module, or a battery pack. A battery module or battery pack can be formed by connecting multiple batteries in series and parallel. In this embodiment, the specific type and size of the power battery 121 are not specifically limited.

[0045] In addition, to intelligently manage and maintain the power battery 121, prevent overcharging and over-discharging, and extend its service life, the battery system 120 generally includes a battery management system (BMS) 122 for functions such as charge / discharge management, high-voltage control, battery protection, battery data acquisition, and battery status assessment. Optionally, the BMS 122 can be integrated with the power battery 121 in the same device or apparatus, or it can be a separate device or apparatus located outside the power battery 121.

[0046] The charging device 110 can output charging power according to the charging requirements of the BMS 122 to charge the power battery 121. For example, the charging device 110 can output voltage and current according to the required voltage and current sent by the BMS 122. Optionally, the charging device 110 in this embodiment can be a charging pile, also known as a charger. The charging pile here can be, for example, a regular charging pile, a supercharging pile, or a charging pile that supports vehicle-to-grid (V2G) mode.

[0047] like Figure 1 As shown, the charging device 110 can be connected to the power battery 121 via a wire 130 and to the BMS 122 via a communication line 140. The communication line 140 is used to realize information interaction between the charging device 110 and the BMS. As an example, the communication line 140 includes, but is not limited to, a controller area network (CAN) communication bus or a daisy chain communication bus.

[0048] In addition to communicating with the BMS 122 via the communication line 140, the charging device 110 can also communicate with the BMS 122 via a wireless network. This application embodiment does not specifically limit the wired or wireless communication type between the charging device 110 and the BMS 122.

[0049] Figure 2 A schematic diagram of a charging method 200 for a power battery according to an embodiment of this application is shown. Method 200 can be executed by a BMS, such as a battery management system (BMS). Figure 1 BMS 122 in the example. Method 200 may include at least some of the following.

[0050] In step S210, the negative electrode potential safety threshold is determined based on the battery state parameters of the power battery.

[0051] In step S220, during the charging process of the power battery, the charging request current of the power battery is adjusted based on the negative electrode potential (or anode potential) and the negative electrode potential safety threshold of the power battery.

[0052] The battery state parameters of a power battery may include, but are not limited to, its state of charge (SOC), temperature, and state of health (SOH). SOC represents the remaining capacity of the power battery, numerically defined as the ratio of its current remaining capacity to its total usable capacity, usually expressed as a percentage. Specifically, SOC = 100% indicates the power battery is fully charged; conversely, SOC = 0% indicates the power battery is fully discharged. SOH represents the aging state of the power battery, and can also be understood as its remaining lifespan. After long-term operation, the performance of a power battery will continuously degrade; therefore, the remaining lifespan will be shorter, i.e., the SOH value will be smaller. A smaller SOH indicates a higher risk of lithium plating in the power battery.

[0053] Optionally, method 200 may further include: the BMS acquiring the battery state parameters of the power battery.

[0054] The battery state parameters of a power battery can be those before charging. That is, before charging, the BMS acquires the battery state parameters and determines the negative electrode potential safety threshold based on these parameters. Afterward, during the entire charging process, the BMS no longer acquires the battery state, and the negative electrode potential safety threshold remains unchanged.

[0055] In this way, from the moment the power battery starts charging, the BMS can adjust the charging request current of the power battery according to the negative electrode potential safety threshold. This allows the BMS to adjust the charging request current throughout the entire charging process, thereby further ensuring the safety performance of the power battery and further improving the charging speed of the power battery.

[0056] Alternatively, the battery state parameters of the power battery can be the battery state parameters during the power battery charging process. That is, during the charging process of the power battery, the BMS can acquire the battery state parameters of the power battery in real time.

[0057] Among them, the BMS can periodically acquire the battery state parameters during the charging process of the power battery. For example, during the charging process, the BMS can acquire the battery state parameters every 5 seconds.

[0058] Alternatively, during the charging process of the power battery, the BMS can acquire the battery state parameters once each time the battery state parameters change.

[0059] Since the state parameters of the power battery may change continuously during charging, the above technical solution allows the BMS to determine the state parameters of the power battery during charging. In this way, the determined state parameters are likely to be the closest to the actual state parameters of the power battery at the current moment. This makes the negative electrode potential safety threshold determined by the BMS based on the latest state parameters of the power battery more accurate, thereby further improving the charging speed of the battery while ensuring battery safety performance.

[0060] Normally, during the charging process of a power battery, the negative electrode potential gradually decreases. When the negative electrode potential drops to a certain level, lithium plating occurs. Taking a lithium-ion battery with a graphite negative electrode system as an example, during charging, the electrodes become polarized, meaning the negative electrode potential decreases while the positive electrode potential increases. When the negative electrode potential drops to 0V (vs Li / Li),... + When lithium metal is deposited on the surface of the negative electrode, it can damage the battery performance and, in severe cases, may even cause safety accidents such as thermal runaway.

[0061] In view of this problem, in the embodiments of this application, the higher the risk of lithium plating in the power battery, the greater the safety threshold of the negative electrode potential.

[0062] As an example, when the SOC of the power battery is in the first SOC range, the negative electrode potential safety threshold is a first preset negative electrode potential safety threshold; when the SOC of the power battery is in the second SOC range, the negative electrode potential safety threshold is a second preset negative electrode potential safety threshold. Wherein, the SOC in the first SOC range is less than the SOC in the second SOC range, and the first preset negative electrode potential safety threshold is less than the second preset negative electrode potential safety threshold.

[0063] As another example, when the temperature of the power battery is in the first temperature range, the negative electrode potential safety threshold is the third preset negative electrode potential safety threshold; when the temperature of the power battery is in the second temperature range, the negative electrode potential safety threshold is the fourth preset negative electrode potential safety threshold. The temperature in the first temperature range is lower than the temperature in the second temperature range, and the third preset negative electrode potential safety threshold is higher than the fourth preset negative electrode potential safety threshold.

[0064] As another example, when the SOH of the power battery is in the first SOH range, the negative electrode potential safety threshold is the fifth preset negative electrode potential safety threshold; when the SOH of the power battery is in the second SOH range, the negative electrode potential safety threshold is the sixth preset potential safety threshold. Specifically, the SOH in the first SOH range is less than the SOH in the second SOH range, and the fifth preset negative electrode potential safety threshold is greater than the sixth preset negative electrode potential safety threshold.

[0065] Tables 1-4 show examples of several negative electrode potential safety thresholds. The unit for the negative electrode potential safety threshold is millivolts (mV). In Table 1, the SOH of the power battery is 95%–100%; in Table 2, it is 90%–95%; in Table 3, it is 85%–90%; and in Table 4, it is less than 85%.

[0066] Table 1

[0067]

[0068] Table 2

[0069]

[0070] Table 3

[0071]

[0072]

[0073] Table 4

[0074]

[0075] As can be seen from Tables 1-4, under the condition that other factors remain unchanged, the higher the SOC of the power battery, the higher the safety threshold of the negative electrode potential. For example, when the temperature of the power battery is within the range of [-10℃, 0℃) and the SOH is 95% to 100%, the safety threshold of the negative electrode potential is 10mV when the SOC of the power battery is within the range of [0%, 40%); and 15mV when the SOC of the power battery is within the range of [40%, 80%).

[0076] Tables 1-4 also show that, all other things being equal, the lower the temperature of the power battery, the higher the safety threshold of the negative electrode potential. For example, when the state of charge (SOC) of the power battery is in the range of [80%, 100%] and the state of oxygen (SOH) is 85%–95%, and the temperature of the power battery is in the range of [-10℃, 0℃), the safety threshold of the negative electrode potential is 35mV; when the temperature of the power battery is in the range of [0℃, 10℃), the safety threshold of the negative electrode potential is 30mV.

[0077] Tables 1-4 also show that, all other things being equal, the lower the SOH of the power battery, the higher the safety threshold of the negative electrode potential. For example, when the SOC of the power battery is in the range of [0%, 40%) and the temperature is in the range of [-10℃, 0℃), the safety threshold of the negative electrode potential is 18mV when the SOH of the power battery is 85% to 90%; and 15mV when the SOH of the power battery is 90% to 95%.

[0078] It should be understood that the specific examples in this document are only intended to help those skilled in the art better understand the embodiments of this application, and are not intended to limit the scope of the embodiments of this application.

[0079] The above technical solution sets a safe threshold for the negative electrode potential based on the degree of lithium plating risk of the power battery. On the one hand, setting a relatively large safe threshold for the negative electrode potential corresponding to power batteries with high lithium plating risk can effectively suppress the lithium plating risk and improve the safety performance of the power battery. On the other hand, setting a relatively small safe threshold for the negative electrode potential corresponding to power batteries with low lithium plating risk can ensure the charging speed of the power battery without affecting its safety performance.

[0080] Optionally, before determining the negative electrode potential safety threshold, method 200 may further include: the BMS determining a first charging request current and sending the first charging request current to the charging pile. Specifically, the BMS can determine the first charging request current based on parameters such as the temperature, SOC, SOH, and voltage of the power battery.

[0081] After receiving the first charging request current, the charging pile can charge the power battery based on the first charging request current.

[0082] Optionally, the first charging request current can be carried in, but is not limited to, the battery charging demand (BCL) message.

[0083] After determining the negative electrode potential safety threshold, the BMS can adjust the charging request current of the power battery based on the negative electrode potential and the negative electrode potential safety threshold during the charging process of the power battery.

[0084] Specifically, during the charging process, if the negative electrode potential of the power battery drops to the negative electrode potential safety threshold, the BMS can reduce the charging request current of the power battery, that is, adjust the charging request current from the first charging request current to the second charging request current, which is less than the first charging request current.

[0085] After adjusting the first charging request current to the second charging request current, the BMS can send the second charging request current to the charging pile so that the charging pile can charge the power battery based on the second charging request current.

[0086] The above technical solution indicates that when the negative electrode potential of the power battery drops to the safe threshold of the negative electrode potential, it means that the power battery may be about to experience lithium plating. In this case, reducing the charging request current of the power battery can avoid safety problems caused by lithium ion accumulation, such as battery combustion or explosion, thereby ensuring the safety performance of the power battery.

[0087] Alternatively, if the negative electrode potential of the power battery has not dropped to the negative electrode potential safety threshold, and the charging time of the power battery is greater than the time threshold, it indicates that the charging request current at the current moment is small. In this case, the BMS can increase the charging request current of the power battery, that is, adjust the charging request current from the first charging request current to the third charging request current, and the third charging request current is greater than the first charging request current.

[0088] Optionally, when the BMS sends the first charging request current to the charging pile, the BMS can start a timer, the duration of which is a time threshold. After the timer expires, it indicates that the charging time of the power battery has exceeded the time threshold.

[0089] Optionally, the time threshold can be, but is not limited to, 30 seconds.

[0090] After adjusting the first charging request current to the third charging request current, the BMS can send the third charging request current to the charging pile so that the charging pile can charge the power battery based on the third charging request current.

[0091] If the negative electrode potential of the power battery fails to drop to the safe threshold for an extended period, it indicates that the current charging current of the power battery is too low. In this case, increasing the charging request current of the power battery can improve the charging speed, significantly reduce the charging time, and thus improve the user experience.

[0092] It should be understood that in the embodiments of this application, "first", "second" and "third" are only used to distinguish different objects, but do not constitute a limitation on the scope of the embodiments of this application.

[0093] This application does not specifically limit the implementation method of the BMS obtaining the negative electrode potential of the power battery. For example, the BMS can predict the negative electrode potential of the power battery through a negative electrode potential prediction model, or the BMS can obtain the negative electrode potential of the power battery through actual measurement of a three-electrode battery with a reference electrode.

[0094] In one embodiment, for a two-electrode battery, the BMS can separate the positive and negative electrodes of the battery using a negative electrode potential prediction model, thereby obtaining the negative electrode potential. The negative electrode potential prediction model can be, for example, an equivalent circuit model, an electrochemical model, or an equivalent circuit and electrochemical coupling model.

[0095] In another embodiment, the BMS can also obtain the negative electrode potential of the power battery by collecting the negative electrode potential of the three-electrode battery with a reference electrode and the potential of the reference electrode. The three-electrode battery refers to a battery that includes a positive electrode and a negative electrode in addition to the traditional two-electrode battery. The reference electrode is, for example, a lithium metal reference electrode, a lithium alloy reference electrode, or a copper wire in-situ lithium-plated reference electrode.

[0096] Specifically, a polarity equivalent model of the three-electrode battery can be established first. This polarity equivalent model can include positive electrode parameters and negative electrode parameters to reflect the external and internal characteristics of the three-electrode battery, so as to accurately predict the negative electrode potential. Among them, the polarity equivalent model can include the Rint model, the first-order RC equivalent circuit model of the polarity, the second-order RC equivalent circuit model of the polarity, etc.

[0097] Figure 3 A schematic diagram of the first-order RC equivalent circuit model of an embodiment of this application is shown. Figure 3 As shown, Ut is the full cell terminal voltage; Uca and Uan are the potentials of the positive and negative electrodes relative to the reference electrode, respectively. OCVca and OCVan represent the open-circuit voltages of the positive and negative electrodes, respectively; Rca_0 and Ran_0 represent the ohmic internal resistances of the positive and negative electrodes, respectively; Uca_p and Uan_p represent the polarization voltages of the positive and negative electrodes, respectively; Rca_p and Ran_p represent the polarization resistances of the positive and negative electrodes, respectively; Cca_p and Can_p represent the polarization capacitances of the positive and negative electrodes, respectively; and I represents the current. Uca_p' and Uan_p' represent the derivatives of Uca_p and Uan_p, respectively.

[0098] First, the open-circuit voltage OCVca of the positive electrode and the open-circuit voltage OCVan of the negative electrode can be obtained by actual measurement. Then, according to formulas (1) to (5), combined with optimization algorithms such as least squares method and genetic algorithm, the model parameters Rca_0, Ran_0, Rca_p, Ran_p, Cca_p and Can_p are calibrated. Finally, the potential of the negative electrode is estimated by using extended Kalman filter algorithm, proportional-integral-differential (PID) algorithm or Romberg observer.

[0099] Ut=Uca–Uan (1)

[0100] Uca=OCVca+I*Rca_0+Uca_p (2)

[0101] Uan=OCVan+I*Ran_0+Uan_p (3)

[0102] Uca_p'=I / Cca_p-Uca_p / (Rca_p*Cca_p) (4)

[0103] Uan_p'=I / Can_p-Uan_p / (Ran_p*Can_p) (5)

[0104] The following is a brief introduction to an example of using the extended Kalman filter algorithm to predict the negative electrode potential. The extended Kalman filter algorithm mainly consists of a state equation (6) and an observation equation (7), and then combines the recursive equations (8)-(12) to iteratively update the time and state to achieve state estimation.

[0105] X k+1 =A k X k +B k U k +Q k (6)

[0106] Y k =C k X k +R k (7)

[0107]

[0108]

[0109]

[0110]

[0111]

[0112] Where X is the state variable to be estimated, U is the controllable input, Y is the output, Q and R represent the system error and measurement error, respectively, P is the covariance matrix of the estimation error, the subscript k represents the variable at time k, the subscript k-1 represents the variable at time k-1, the subscript k+1 represents the variable at time k+1, and the superscript " ∧ "" represents the estimated value, and the superscript T indicates that the matrix is ​​transposed. P is the covariance matrix of the estimation error, for example, Let P represent the prior estimate covariance matrix at time k. k Let K denote the posterior estimated covariance matrix at time k. A, B, C, and D are coefficient matrices, and K... k For Kalman gain.

[0113] Substitute the values ​​of X, A, B, C, Q, and R into the above equation:

[0114]

[0115]

[0116]

[0117]

[0118]

[0119] R k =0.01

[0120] The negative electrode potential can then be obtained through the negative electrode potential prediction equation:

[0121]

[0122] In some embodiments, the BMS can determine the adjusted current (such as a second charging request current or a third charging request current) using a predictive control algorithm. For example, the BMS can determine the adjusted current using a proportional-integral-differential (PID) control algorithm.

[0123] The following example illustrates how the BMS adjusts the first charging request current to the second charging request current. Specifically, the BMS can obtain the adjusted current using the following formula:

[0124] I0 k+1 =I0 k +ΔI k

[0125]

[0126] Among them, I0 k+1 The charging request current at time k+1 is also known as the second charging request current, I0. k Let ΔUan be the charging request current at time k, i.e., the first charging request current. k Let ΔUan be the negative electrode potential safety threshold at time k, or the negative electrode potential of the power battery at time k. k-1 This refers to the safe threshold of the negative electrode potential at time k-1, or the negative electrode potential of the power battery at time k-1. p k i k d The proportional, integral, and derivative parameters of the PID control algorithm are given separately. For example, k... p It can be 20, k i It can be 5, k d It can be 70.

[0127] To better understand the power battery charging method 200 of this application embodiment, the following is combined with... Figure 4 This application describes a method for charging a power battery according to one possible embodiment.

[0128] In step 401, the BMS determines whether the power battery is in a charging state.

[0129] If the power battery is charging, proceed to step 402; if the power battery is not charging, proceed to step 409.

[0130] In step 402, the BMS determines the charging request current I0 of the power battery.

[0131] Specifically, the BMS can first obtain parameters such as the SOC, SOH, temperature and voltage of the power battery, and then determine I0 based on these parameters.

[0132] In step 403, the BMS sends a charging request current I0 to the charging pile to request charging and starts timing.

[0133] In step 404, the BMS obtains the negative electrode potential of the power battery.

[0134] In step 405, the BMS compares the negative electrode potential of the power battery with the negative electrode potential safety threshold to determine whether the negative electrode potential of the power battery has dropped to the negative electrode potential safety threshold.

[0135] If the negative electrode potential of the power battery drops to the negative electrode potential safety threshold, then proceed to step 406; if the negative electrode potential safety threshold of the power battery does not drop to the negative electrode potential safety threshold, then proceed to step 407.

[0136] In step 406, the BMS adjusts the charging request current I0 to the charging request current I1 and sends the adjusted charging request current I1 to the charging pile so that the charging pile charges the power battery based on I1.

[0137] In step 407, the BMS determines whether the charging time of the power battery exceeds a time threshold.

[0138] If the charging time is greater than the time threshold, the BMS executes step 408; if the charging time is less than the time threshold, the BMS executes step 404.

[0139] In step 408, the BMS adjusts the charging request current I0 to the charging request current I2 and sends the adjusted charging request current I2 to the charging pile so that the charging pile charges the power battery based on I2.

[0140] In step 409, the BMS determines whether the power battery is in a fully charged state or in a disconnected state.

[0141] If the power battery is fully charged or the charging gun is disconnected, the charging process ends; if the power battery is not fully charged or the charging gun is disconnected, the BMS continues to execute step 404.

[0142] In this embodiment, since the risk of lithium plating in a power battery is closely related to its own battery state parameters, the above technical solution determines the negative electrode potential safety threshold based on the battery state parameters. This makes the determined negative electrode potential safety threshold more accurate and closer to the critical potential for lithium plating in the power battery. Thus, adjusting the charging request current of the power battery based on the determined negative electrode potential safety threshold and the negative electrode potential not only ensures the safety performance of the power battery but also improves its charging speed.

[0143] The method embodiments of this application have been described in detail above. The device embodiments of this application are described below. The device embodiments correspond to the method embodiments. Therefore, for any parts not described in detail, please refer to the previous method embodiments. The device can implement any possible implementation of the above methods.

[0144] Figure 5 A schematic block diagram of a BMS 500 according to one embodiment of this application is shown. This BMS 500 can perform the power battery charging method 200 described in the embodiments of this application. Figure 5 As shown, the BMS 500 may include:

[0145] The determining unit 510 is used to determine the negative electrode potential safety threshold based on the battery state parameters of the power battery, wherein the battery state parameters include at least one of the state of charge (SOC), temperature, and state of health (SOH) of the power battery.

[0146] The adjustment unit 520 is used to adjust the charging request current of the power battery based on the negative electrode potential of the power battery and the negative electrode potential safety threshold during the charging process of the power battery.

[0147] Optionally, in one embodiment of this application, the adjustment unit 520 is specifically used to: if the negative electrode potential drops to the negative electrode potential safety threshold, adjust the charging request current from the first charging request current to the second charging request current, wherein the second charging request current is less than the first charging request current.

[0148] Optionally, in one embodiment of this application, the adjustment unit 520 is specifically used to: if the negative electrode potential does not drop to the negative electrode potential safety threshold and the charging time of the power battery is greater than the time threshold, adjust the charging request current from the first charging request current to the third charging request current, wherein the third charging request current is greater than the first charging request current.

[0149] Optionally, in one embodiment of this application, when the SOC of the power battery is in the first SOC range, the negative electrode potential safety threshold is a first preset negative electrode potential safety threshold.

[0150] When the SOC of the power battery is in the second SOC range, the negative electrode potential safety threshold is the second preset negative electrode potential safety threshold; wherein, the SOC in the first SOC range is less than the SOC in the second SOC range, and the first preset negative electrode potential safety threshold is less than the second preset negative electrode potential safety threshold.

[0151] Optionally, in one embodiment of this application, when the temperature of the power battery is in a first temperature range, the negative electrode potential safety threshold is a third preset negative electrode potential safety threshold; when the temperature of the power battery is in a second temperature range, the negative electrode potential safety threshold is a fourth preset negative electrode potential safety threshold; wherein, the temperature in the first temperature range is lower than the temperature in the second temperature range, and the third preset negative electrode potential safety threshold is greater than the fourth preset negative electrode potential safety threshold.

[0152] Optionally, in one embodiment of this application, when the SOH of the power battery is in the first SOH range, the negative electrode potential safety threshold is a fifth preset negative electrode potential safety threshold; when the SOH of the power battery is in the second SOH range, the negative electrode potential safety threshold is a sixth preset negative electrode potential safety threshold; wherein, the SOH in the first SOH range is less than the SOH in the second SOH range, and the fifth preset negative electrode potential safety threshold is greater than the sixth preset negative electrode potential safety threshold.

[0153] Optionally, in one embodiment of this application, the battery state parameters of the power battery are the battery state parameters before the power battery is charged.

[0154] Optionally, in one embodiment of this application, the battery state parameters of the power battery are the battery state parameters during the charging process of the power battery.

[0155] It should be understood that the BMS 500 can perform the corresponding operations of the BMS in method 200, which will not be elaborated here for the sake of brevity. Correspondingly, the BMS 500 can achieve the same technical effect as the aforementioned method 200, which will not be described here for the sake of brevity.

[0156] Figure 6 This is a schematic diagram of the hardware structure of a BMS according to an embodiment of this application. The BMS 600 includes a memory 601, a processor 602, a communication interface 603, and a bus 604. The memory 601, processor 602, and communication interface 603 are interconnected via the bus 604.

[0157] The memory 601 may be a read-only memory (ROM), a static storage device, or a random access memory (RAM). The memory 601 may store a program. When the program stored in the memory 601 is executed by the processor 602, the processor 602 and the communication interface 603 are used to execute the various steps of the power battery charging method of the embodiments of this application.

[0158] The processor 602 may be a general-purpose central processing unit (CPU), microprocessor, application-specific integrated circuit (ASIC), graphics processing unit (GPU), or one or more integrated circuits, used to execute relevant programs to achieve the functions required by the units in the apparatus of this application embodiment, or to execute the power battery charging method of this application embodiment.

[0159] The processor 602 can also be an integrated circuit chip with signal processing capabilities. In implementation, each step of the power battery charging method of this application embodiment can be completed by the integrated logic circuitry in the processor 602 or by software instructions.

[0160] The processor 602 described above can also be a general-purpose processor, a digital signal processor (DSP), an ASIC, a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of this application can be directly implemented by the hardware processor, or implemented by a combination of hardware and software modules in the processor. The software modules can be located in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. This storage medium is located in memory 601. The processor 602 reads the information in memory 601 and, in conjunction with its hardware, completes the functions required by the units included in the BMS of this application embodiment, or executes the power battery charging method of this application embodiment.

[0161] The communication interface 603 uses a transceiver device, such as, but not limited to, a transceiver, to enable communication between the BMS 600 and other devices or communication networks. For example, the BMS 600 can send charging request information to a charging station through the communication interface 603.

[0162] Bus 604 may include a pathway for transmitting information between various components of device 600 (e.g., memory 601, processor 602, communication interface 603).

[0163] It should be noted that although the BMS 600 described above only shows the memory, processor, and communication interface, those skilled in the art should understand that in specific implementations, the BMS 600 may also include other devices necessary for normal operation. Furthermore, depending on specific needs, those skilled in the art should understand that the BMS 600 may also include hardware devices to implement other additional functions. Moreover, those skilled in the art should understand that the BMS 600 may only include the devices necessary for implementing the embodiments of this application, and may not necessarily include... Figure 6 All the devices shown.

[0164] This application also provides a computer-readable storage medium storing program code for execution by a device, the program code including instructions for performing the steps in the above-described method for charging a power battery.

[0165] This application also provides a computer program product, which includes a computer program stored on a computer-readable storage medium. The computer program includes program instructions that, when executed by a computer, cause the computer to perform the above-described method for charging a power battery.

[0166] The aforementioned computer-readable storage medium may be a transient computer-readable storage medium or a non-transitory computer-readable storage medium.

[0167] It should be understood that in the various embodiments of this application, the sequence number of each process does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0168] It should also be understood that the various implementation methods described in this specification can be implemented individually or in combination, and the embodiments of this application are not limited in this respect.

[0169] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. 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 charging a power battery, characterized in that, The method, applied to the battery management system (BMS) of the power battery, includes: Based on the battery state parameters of the power battery, a negative electrode potential safety threshold is determined. The battery state parameters include at least one of the power battery's state of charge (SOC), temperature, and state of health (SOH). During the charging process of the power battery, the charging request current of the power battery is adjusted based on the negative electrode potential of the power battery and the negative electrode potential safety threshold. The step of adjusting the charging request current of the power battery based on the negative electrode potential and the negative electrode potential safety threshold includes: If the negative electrode potential drops to the negative electrode potential safety threshold, the charging request current is adjusted from the first charging request current to the second charging request current, where the second charging request current is less than the first charging request current; or... If the negative electrode potential does not drop to the negative electrode potential safety threshold and the charging time of the power battery is greater than the time threshold, the charging request current is adjusted from the first charging request current to the third charging request current, and the third charging request current is greater than the first charging request current.

2. The method according to claim 1, characterized in that, When the SOC of the power battery is in the first SOC range, the negative electrode potential safety threshold is the first preset negative electrode potential safety threshold. When the SOC of the power battery is in the second SOC range, the negative electrode potential safety threshold is the second preset negative electrode potential safety threshold. Wherein, the SOC in the first SOC interval is less than the SOC in the second SOC interval, and the first preset negative electrode potential safety threshold is less than the second preset negative electrode potential safety threshold.

3. The method according to claim 1, characterized in that, When the temperature of the power battery is in the first temperature range, the negative electrode potential safety threshold is the third preset negative electrode potential safety threshold. When the temperature of the power battery is in the second temperature range, the negative electrode potential safety threshold is the fourth preset negative electrode potential safety threshold. Wherein, the temperature in the first temperature range is lower than the temperature in the second temperature range, and the third preset negative electrode potential safety threshold is greater than the fourth preset negative electrode potential safety threshold.

4. The method according to any one of claims 1 to 3, characterized in that, When the SOH of the power battery is in the first SOH range, the negative electrode potential safety threshold is the fifth preset negative electrode potential safety threshold. When the SOH of the power battery is in the second SOH range, the negative electrode potential safety threshold is the sixth preset negative electrode potential safety threshold. Wherein, the SOH in the first SOH interval is less than the SOH in the second SOH interval, and the fifth preset negative electrode potential safety threshold is greater than the sixth preset negative electrode potential safety threshold.

5. The method according to any one of claims 1 to 3, characterized in that, The battery state parameters of the power battery are the battery state parameters before the power battery is charged.

6. The method according to any one of claims 1 to 3, characterized in that, The battery state parameters of the power battery are the battery state parameters during the charging process of the power battery.

7. A battery management system for a power battery, characterized in that, include: The determining unit is used to determine the negative electrode potential safety threshold based on the battery state parameters of the power battery, wherein the battery state parameters include at least one of the state of charge (SOC), temperature, and state of health (SOH) of the power battery. An adjustment unit is used to adjust the charging request current of the power battery based on the negative electrode potential of the power battery and the negative electrode potential safety threshold during the charging process of the power battery. The adjustment unit is specifically used for: If the negative electrode potential drops to the negative electrode potential safety threshold, the charging request current is adjusted from the first charging request current to the second charging request current, where the second charging request current is less than the first charging request current. or, If the negative electrode potential does not drop to the negative electrode potential safety threshold and the charging time of the power battery is greater than the time threshold, the charging request current is adjusted from the first charging request current to the third charging request current, and the third charging request current is greater than the first charging request current.

8. The battery management system according to claim 7, characterized in that, When the SOC of the power battery is in the first SOC range, the negative electrode potential safety threshold is the first preset negative electrode potential safety threshold. When the SOC of the power battery is in the second SOC range, the negative electrode potential safety threshold is the second preset negative electrode potential safety threshold. Wherein, the SOC in the first SOC interval is less than the SOC in the second SOC interval, and the first preset negative electrode potential safety threshold is less than the second preset negative electrode potential safety threshold.

9. The battery management system according to claim 7, characterized in that, When the temperature of the power battery is in the first temperature range, the negative electrode potential safety threshold is the third preset negative electrode potential safety threshold. When the temperature of the power battery is in the second temperature range, the negative electrode potential safety threshold is the fourth preset negative electrode potential safety threshold. Wherein, the temperature in the first temperature range is lower than the temperature in the second temperature range, and the third preset negative electrode potential safety threshold is greater than the fourth preset negative electrode potential safety threshold.

10. The battery management system according to any one of claims 7 to 9, characterized in that, When the SOH of the power battery is in the first SOH range, the negative electrode potential safety threshold is the fifth preset negative electrode potential safety threshold. When the SOH of the power battery is in the second SOH range, the negative electrode potential safety threshold is the sixth preset negative electrode potential safety threshold. Wherein, the SOH in the first SOH interval is less than the SOH in the second SOH interval, and the fifth preset negative electrode potential safety threshold is greater than the sixth preset negative electrode potential safety threshold.

11. The battery management system according to any one of claims 7 to 9, characterized in that, The battery state parameters of the power battery are the battery state parameters before the power battery is charged.

12. The battery management system according to any one of claims 7 to 9, characterized in that, The battery state parameters of the power battery are the battery state parameters during the charging process of the power battery.

13. A battery management system for a power battery, characterized in that, It includes a processor and a memory, the memory being used to store a computer program, and the processor being used to invoke the computer program to execute the method for charging a power battery as described in any one of claims 1 to 6.

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