Battery management system, battery device, and balancing method

Abstract

A battery management system calculates an SOC of each battery cell, calculates a cell balancing time of a corresponding battery cell based on information including a self-discharge rate of each battery cell and the SOC of the corresponding battery cell, and performs cell balancing of the corresponding battery cell based on the cell balancing time of each battery cell.

Description

Technical Field

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2025-0009278, filed on January 22, 2025, the entire contents of which are incorporated herein by reference.

[0003] This disclosure relates to a battery management system, a battery device, and a balancing method. Background Technology

[0004] Electric or hybrid vehicles are automobiles that are powered primarily by batteries driving electric motors, and are being actively researched because they represent a potential alternative to the pollution and energy problems associated with internal combustion engine vehicles. Furthermore, batteries are being used in a variety of external devices beyond electric vehicles.

[0005] Inside a battery, multiple individual cells are connected in series. Voltage deviations between these cells can lead to over-discharge or over-charge, and also reduce their lifespan. To mitigate voltage deviations, a cell balancing circuit is designed within the battery management system (BMS). The BMS calculates the state of charge (SOC) of each cell and, based on the SOC, calculates the discharge rate (i.e., balancing time) of each cell to reduce deviations between cells. However, due to differences in self-discharge rates between cells, deviations may still exist even after balancing is complete. Summary of the Invention

[0006] Technical issues

[0007] Some embodiments may provide a battery management system, battery device, and balancing method that can perform cell balancing by taking into account the self-discharge rate.

[0008] Technical solution

[0009] According to some embodiments, a method for balancing multiple battery cells in a battery management system may include: calculating the state of charge (SOC) of each battery cell; calculating the cell balancing time of a corresponding battery cell based on information including the self-discharge rate of each battery cell and the SOC of the corresponding battery cell; and performing cell balancing of the corresponding battery cell based on the cell balancing time of each battery cell.

[0010] According to some embodiments, a battery device may include a plurality of battery cells and a battery management system configured to manage the plurality of battery cells. The battery management system may be configured to calculate the state of charge (SOC) of the plurality of battery cells, calculate the cell balancing time of a target battery cell based on information including the self-discharge rate and SOC of the target battery cell, and perform cell balancing of the target battery cell based on the cell balancing time of the target battery cell.

[0011] According to some embodiments, a program stored on a computer-readable recording medium and executed by a processor of a battery device can be provided. The program can be configured to cause the processor to calculate the state of charge (SOC) of each battery cell, calculate the cell balancing time of the corresponding battery cell based on information including the self-discharge rate and the SOC of each battery cell, and perform cell balancing of the corresponding battery cell based on the cell balancing time of each battery cell. Attached Figure Description

[0012] Figure 1 This is a block diagram illustrating a battery device according to some embodiments.

[0013] Figure 2 This is a flowchart illustrating a balancing method for a battery management system according to some embodiments.

[0014] Figure 3 This is a flowchart illustrating a method for calculating the self-discharge rate in a battery management system according to some embodiments.

[0015] Figure 4 This is a diagram used to explain a method for calculating the self-discharge rate in a battery management system according to some embodiments. Detailed Implementation

[0016] In the following detailed description, certain embodiments of the invention are shown and described by way of illustration only. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and descriptions should be considered illustrative in nature and not restrictive. Throughout the specification, the same reference numerals denote the same elements.

[0017] When describing an element as "connected" to another element, it should be understood that the element can be directly connected to the other element or connected to the other element through a third element. On the other hand, when describing an element as "directly connected" to another element, it should be understood that the element is not connected to the other element through a third element.

[0018] As used in this article, the singular form may be intended to include the plural form as well, unless an explicit expression such as “a” or “single” is used.

[0019] In the flowchart described with reference to the accompanying drawings, the order of operations or steps can be changed, several operations or steps can be combined, a certain operation or step can be divided, and a specific operation or step can be omitted.

[0020] Figure 1 This is a block diagram illustrating a battery device according to some embodiments.

[0021] refer to Figure 1 The battery device 100 may include a battery module 110, a battery management system (BMS) 120, and switches 131 and 132.

[0022] The battery device 100 may have a structure that allows it to be electrically connected to an external device via a positive connection terminal P+ and a negative connection terminal P-. In some embodiments, when the external device is a load, the battery device 100 can discharge by operating as a power source supplying power to the load. When the external device is a charger, the battery device 100 can be charged by receiving external power from the charger. In some embodiments, the external device operating as a load may be, for example, an electronic device, a mobile device, or an energy storage system (ESS), and the mobile device may be, for example, a vehicle, such as an electric vehicle, a hybrid vehicle, or a smart mobility tool. The battery device 100 may be referred to as a battery pack.

[0023] Battery module 110 may include a plurality of battery cells 111. In some embodiments, the plurality of battery cells 111 may be connected in series. In some embodiments, battery device 100 may include a plurality of battery modules 110. The plurality of battery cells 111 of battery module 110 may each be connected to battery management system 120 via wiring.

[0024] Switch 131 can be connected between the positive terminal and the positive connection terminal P+ of battery module 110, and switch 132 can be connected between the negative terminal and the negative connection terminal P of battery module 110. Switches 131 and 132 can be controlled by battery management system 120 to control the connection between battery device 100 and external devices. In some embodiments, switches 131 and 132 may each include a contactor, which includes a relay. In some embodiments, switches 131 and 132 may each include an electrical switch such as a transistor. In some embodiments, battery device 100 may also include a drive circuit (not shown) that drives each of switches 131 and 132 in response to a control signal from battery management system 120.

[0025] The battery management system 120 can collect and analyze information about individual battery cells 111 to control operations such as charging and discharging of individual battery cells 111, cell balancing, and protection operations. The battery management system 120 may include a balancing circuit 121, a battery monitoring circuit 122, and a processor 123. In some embodiments, the battery monitoring circuit 122 and the processor 123 may operate as control circuits for controlling the balancing circuit 121.

[0026] The battery monitoring circuit 122 can be connected via wiring to each of the plurality of battery cells 111 included in the battery module 110, and can monitor the state of the battery cells 111 (e.g., cell voltage). In some embodiments, the battery monitoring circuit 122 may include a plurality of battery monitoring circuits 122 respectively corresponding to the plurality of battery modules 110. In some embodiments, one battery monitoring circuit 122 may correspond to two or more battery modules 110, or two or more battery monitoring circuits 122 may correspond to one battery module 110. In some embodiments, the battery monitoring circuit 122 may be configured as an integrated circuit (IC), and the battery monitoring circuit 122 configured as an IC is referred to as a battery monitoring IC (BMIC).

[0027] Processor 123 can receive monitoring information from battery monitoring circuit 122 and can control the operation of battery monitoring circuit 122. Processor 123 can control the operation of switches 131 and 132. Processor 123 can be a processing circuit and can be, for example, a microcontroller unit (MCU).

[0028] The processor 123 can obtain the state of charge (SOC) of each battery cell 111 based on information provided from the battery monitoring circuit 122. The processor 123 can calculate the self-discharge rate of each battery cell 111 and, based on the self-discharge rate and SOC of each battery cell 111, calculate the cell balancing time for that battery cell 111. The balancing circuit 121 can balance the corresponding battery cell 111 during its cell balancing time.

[0029] Figure 2 This is a flowchart illustrating a balancing method for a battery management system according to some embodiments.

[0030] refer to Figure 2The battery management system can calculate the SOC of each battery cell (S220). In some embodiments, the battery management system can calculate the SOC of each battery cell when it wakes up from sleep mode (S210) (S220). In some embodiments, the battery management system can calculate the SOC of the corresponding battery cell based on the voltage of each battery cell provided from the battery monitoring circuit 122. In this case, the voltage of each battery cell can be the open-circuit voltage (OCV). For example, the battery management system can calculate the SOC of the corresponding battery cell by applying the voltage of each battery cell to the relationship between OCV and SOC.

[0031] The battery management system can obtain the self-discharge rate of each battery cell (S230). The self-discharge rate can indicate the change in SOC per hour [%] due to the self-discharge of the battery cell, and its unit can be % / s, % / m or % / h.

[0032] The battery management system can calculate the cell balance time of a corresponding cell based on the SOC and self-discharge rate of each cell (S240). In some embodiments, the battery management system can determine the minimum SOC among multiple cell SOCs and can calculate the cell balance time of a target cell based on the difference between the target cell SOC and the minimum SOC, the balance discharge rate, and the target cell self-discharge rate (S240). In some embodiments, the balance discharge rate can be a value set for cell balance in the battery management system and can indicate the amount of SOC reduction per hour [%].

[0033] In some embodiments, the battery management system can determine the cell equilibrium time of a corresponding cell by dividing the difference between the SOC of each cell and the minimum SOC by the sum of the equilibrium discharge rate and the self-discharge rate of the corresponding cell (S240).

[0034] The battery management system can perform balancing of the corresponding battery cell during the cell balancing time of each battery cell (S250).

[0035] As described above, since the battery management system can balance the corresponding battery cells during the cell balancing time determined by taking into account the self-discharge rate of each battery cell, the deviation between battery cells can be minimized after balancing.

[0036] Figure 3 This is a flowchart illustrating a method for calculating the self-discharge rate in a battery management system according to some embodiments, and Figure 4 This is a diagram used to explain a method for calculating the self-discharge rate in a battery management system according to some embodiments.

[0037] refer to Figure 3 When the output of the battery device is not needed, the battery management system can enter sleep mode (S310). For example, when a vehicle equipped with a battery device is parked, the battery management system can enter sleep mode.

[0038] The battery management system can wake up at time point t1 (hereinafter referred to as the "first time point") after a first predetermined time T1 has elapsed since the battery management system entered sleep mode (S320), and can measure the voltage V1 of each battery cell at the wake-up time point (S330). Therefore, the time point for measuring the voltage V1 of each battery cell can be approximately the same as the first time point t1. After measuring the voltage V1 of each battery cell (S330), the battery management system can re-enter sleep mode (S340). In some embodiments, the first time point t1 can be a time point after the battery management system has entered sleep mode and then the battery cells have stabilized.

[0039] The battery management system can wake up again at time point t2 (hereinafter referred to as the "second time point") when a second predetermined time T2 has elapsed since the wake-up time point (first time point) t1 (S350), and can measure the voltage V2 of each battery cell at the wake-up time point (S360). Therefore, the time point for measuring the voltage V2 of each battery cell can be approximately the same as the second time point t2. In some embodiments, the battery management system can periodically wake up after entering sleep mode, and the first time point and the second time point can be the time points for periodic wake-up.

[0040] The battery management system can calculate the self-discharge rate of a corresponding battery cell based on the voltage V1 of each battery cell measured at a first time point t1, the voltage V2 of the corresponding battery cell measured at a second time point t2, and a second predetermined time T2 (S370). In some embodiments, the battery management system can obtain the SOC of the target battery cell at the first time point t1 based on the voltage V1 of the target battery cell measured at the first time point t1, and can obtain the SOC of the target battery cell at the second time point t2 based on the voltage V2 of the target battery cell measured at the second time point t2. Since the voltage of the battery cell measured at the wake-up time point corresponds to the OCV, the battery management system can obtain the SOC of the target battery cell by applying the voltage of the target battery cell to the relationship between OCV and SOC. In some embodiments, as in Equation 1, the battery management system can calculate the self-discharge rate of each battery cell as a value obtained by dividing the difference between the SOC of the corresponding battery cell at the first time point t1 and the SOC at the second time point t2 by the time difference (t2-t1) between the first time point t1 and the second time point t2 (i.e., the second predetermined time T2). In other words, the battery management system can calculate the self-discharge rate as the hourly SOC change while the battery management system is in sleep mode—that is, while there is no output from individual battery cells.

[0041] Equation 1

[0042] In Equation 1, SDR represents the self-discharge rate, SOC(t1) represents the SOC at the first time point t1, and SOC(t2) represents the SOC at the second time point t2.

[0043] In some embodiments, the battery management system may store the calculated self-discharge rate of each individual battery cell and provide the stored self-discharge rate when the cells are balanced. In some embodiments, the battery management system may periodically calculate the self-discharge rate of each individual battery cell.

[0044] As mentioned above, since the battery management system can calculate the self-discharge rate as the hourly SOC change while the battery cell is in an idle state and reflect the self-discharge rate during the cell balancing time, it can minimize the deviation between battery cells after balancing.

[0045] In some embodiments, the processor of the battery management system (e.g., Figure 1Processor 123 can operate on a program (i.e., instructions) used to perform the above-described balancing method or self-discharge rate calculation method. The program for performing the balancing method or self-discharge rate calculation method can be loaded into memory for operation of processor 123. The memory can be embedded in processor 123 or located externally to processor 123. The program may include instructions that, when loaded into memory, cause processor 123 to perform the balancing method or self-discharge rate calculation method. That is, the processor can perform the operation of the balancing method or self-discharge rate calculation method by executing the instructions of the program. In some embodiments, the program may be stored on a computer-readable storage medium.

[0046] While the invention has been described in conjunction with what is now considered to be actual embodiments, it should be understood that the invention is not limited to the disclosed embodiments. Rather, it is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A method for balancing multiple battery cells in a battery management system, the method comprising: Calculate the SOC of each battery cell; The cell equilibrium time of the corresponding cell is calculated based on information including the self-discharge rate of each cell and the state of charge (SOC) of the corresponding cell. as well as The cell balancing is performed based on the cell balancing time of each individual cell.

2. The method according to claim 1, further comprising calculating the self-discharge rate of the corresponding battery cell based on the hourly SOC change of each battery cell while the battery management system is in sleep mode.

3. The method according to claim 1, further comprising: The battery management system, which has entered sleep mode, is awakened at the first time point, and then the first voltage of each battery cell is measured. After measuring the first voltage of each battery cell, the battery management system is made to re-enter the sleep mode; The battery management system is woken up at a second time point after the first time point, and then the second voltage of each battery cell is measured; as well as The self-discharge rate of a corresponding battery cell is calculated based on the state of charge (SOC) of the first voltage of each battery cell and the state of charge (SOC) of the second voltage of the corresponding battery cell.

4. The method according to claim 3, wherein, Calculating the self-discharge rate includes calculating the self-discharge rate as a value obtained by dividing the difference between the SOC based on the first voltage and the SOC based on the second voltage by the time difference between the second time point and the first time point.

5. The method according to claim 1, wherein, The information also includes the balanced discharge rate, and The calculation of the single-cell equilibrium time includes calculating the single-cell equilibrium time of each battery cell as a value obtained by dividing the value obtained by subtracting the minimum SOC among the SOCs of the plurality of battery cells from the SOC of the corresponding battery cell by the sum of the equilibrium discharge rate and the self-discharge rate of the corresponding battery cell.

6. A battery device, comprising: Multiple battery cells; as well as A battery management system configured to manage the plurality of individual battery cells. The battery management system is configured as follows: Calculate the SOC of the plurality of battery cells; The cell equilibrium time of the target battery cell is calculated based on information including the self-discharge rate and the state of charge (SOC) of the target battery cell among the plurality of battery cells; and The target battery cell is balanced based on its cell balancing time.

7. The battery device according to claim 6, wherein, The battery management system is configured as follows: Calculate the hourly SOC change of the target battery cell while the battery management system is in sleep mode; and The self-discharge rate of the target battery cell is calculated based on the hourly SOC change.

8. The battery device according to claim 6, wherein, The battery management system is configured as follows: At the first time point, a wake-up from sleep mode is performed, and then the first voltage of the target battery cell is measured; After measuring the first voltage of the target battery cell, the system enters the sleep mode. A wake-up from the sleep mode is performed at a second time point after the first time point, and then the second voltage of the target battery cell is measured; as well as The self-discharge rate of the target battery cell is calculated based on the SOC based on the first voltage and the SOC based on the second voltage.

9. The battery device according to claim 8, wherein, The battery management system is configured to calculate the self-discharge rate as a value obtained by dividing the difference between the SOC based on the first voltage and the SOC based on the second voltage by the time difference between the second time point and the first time point.

10. The battery device according to claim 6, wherein, The information also includes the balanced discharge rate, and The battery management system is configured to calculate the balance time of the target battery cell as a value obtained by dividing the value obtained by subtracting the minimum SOC among the SOCs of the plurality of battery cells from the SOC of the target battery cell by the sum of the balance discharge rate and the self-discharge rate.

11. A program stored on a computer-readable recording medium and executed by a processor of a battery device, wherein, The program is configured to cause the processor to execute: Calculate the SOC of each battery cell; The cell equilibrium time of the corresponding cell is calculated based on information including the self-discharge rate of each cell and the state of charge (SOC) of the corresponding cell. as well as The cell balancing is performed based on the cell balancing time of each individual cell.

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