Battery management system, battery pack, energy storage system, and battery management method

Abstract

A battery management system according to the present disclosure includes a battery monitoring device that detects a voltage of each of a reference battery cell and a plurality of battery cells having a common flat region, and detects a current of a battery pack, and a control circuit that, during discharging of the battery pack, stops charging the battery pack when the voltage of the reference battery cell reaches a reference voltage, initializes a cumulative current value, and determines a state of charge (SOC) of a cell group as equal to a sum of an SOC of the reference battery cell and a predetermined value.

Description

Technical Field

[0001] This application claims priority to Korean Patent Application No. 10-2021-0020649, filed with the Korean Intellectual Property Office on February 16, 2021, the entire disclosure of which is incorporated herein by reference.

[0002] This disclosure relates to techniques for determining the state of charge (SOC) of a battery. Background Technology

[0003] In recent years, the demand for portable electronic products such as laptops, cameras and mobile phones has grown rapidly, and with the widespread development of electric vehicles, energy storage batteries, robots and satellites, much research has been conducted on high-performance batteries that can be recharged.

[0004] Currently, commercial batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium batteries. Among them, lithium batteries have little or no memory effect, and therefore, they are more popular than nickel-based batteries because they can be charged at any time, have a very low self-discharge rate, and have high energy density.

[0005] Battery packs used in high-capacity and high-voltage applications such as electric vehicles or energy storage systems consist of dozens to hundreds of battery cells connected in series. A battery management system is set up to acquire battery parameters (such as voltage, current, state of charge (SOC)) for each battery cell and perform various functions (such as balancing, cooling) to ensure the reliability and safety of each battery.

[0006] Currently, various types of rechargeable battery cells are widely used, some of which exhibit plateau characteristics within a certain range of total state of charge (SOC) (e.g., SOC 10–90%). These plateau characteristics exhibit a small change in open-circuit voltage (OCV) with varying SOC and can be observed from SOC-OCV curves, which are datasets that record the SOC-open-circuit voltage (OCV) relationship. Lithium iron phosphate (LFP) batteries are lithium-ion batteries that use lithium iron phosphate as the positive electrode material (cathode material), and LFP batteries are known to exhibit plateau characteristics.

[0007] When a battery cell has a plateau-characteristic SOC range, the SOC-OCV curve is effective for SOC estimation outside this range. However, within the corresponding SOC range, even a tiny error in the OCV measurement can lead to a large difference between the estimated and actual SOC, making it difficult to accurately determine the SOC of a battery cell during charging and discharging using the SOC-OCV curve. Therefore, when the SOC of a battery cell falls within a flat region (a plateau-characteristic SOC range), the SOC of the battery cell can be determined based on the cumulative current of the battery cell instead of the SOC-OCV curve.

[0008] However, when the SOC of a battery cell remains in a flat region for a long time, the error between the actual current value and the detected current value of the battery cell continues to accumulate in the cumulative current, causing the accuracy of SOC estimation to gradually decrease.

[0009] One solution to this problem is to intentionally charge or discharge individual battery cells to bring their State of Charge (SOC) outside the flat region, and then use an SOC-OCV curve to determine the SOC based on the cell's OCV. However, this method has some drawbacks when applied to cell banks containing multiple cells connected in series. The first drawback is the need to supply or consume significant amounts of power to intentionally charge or discharge multiple cells connected in series. The second drawback is that when discharging all cells connected in series to a common cell bank below the lower limit of the flat region or charging them above the lower limit of the flat region, the voltage across the cell bank drops or rises sharply. Summary of the Invention

[0010] Technical issues

[0011] This disclosure is designed to solve the above-mentioned problems, and therefore aims to provide a battery management system, battery pack, energy storage system and battery management method for determining the state of charge (SOC) of a group of cells in which multiple battery cells are connected in series and configured to have a common flat region, without intentionally charging or discharging the group of cells to place the SOC of each battery cell outside the flat region.

[0012] These and other objects and advantages of this disclosure will become apparent from the following description and from embodiments thereof. Furthermore, it will be readily understood that the objects and advantages of this disclosure can be achieved by the means set forth in the appended claims and combinations thereof.

[0013] Technical solutions

[0014] The battery management system according to aspects of this disclosure is configured for a battery pack, the battery pack including a cell group and a reference cell connected in series with the cell group, the cell group including a plurality of cell groups connected in series. The reference cell and each cell in the cell group are configured to have a flat region, wherein the flat region is a predetermined SOC range in which the open-circuit voltage (OCV) remains below a predetermined reference value as the state of charge (SOC) changes. Under initial conditions immediately following the manufacture of the battery pack, the SOC of the reference cell is lower than the SOC of each cell in the cell group by a predetermined value. The battery management system includes: a battery monitoring device configured to detect the voltage of the reference cell and each of the plurality of cell groups, and to detect the current of the battery pack; and a control circuit operatively coupled to the battery monitoring device and configured to determine a cumulative current value of the battery pack current. The control circuit is configured to: during the discharge of the battery pack, when the voltage of the reference battery cell reaches a reference voltage that is lower than the lower limit of a predetermined safe voltage range, stop discharging the battery pack, determine the SOC of the reference battery cell based on the reference voltage and the current of the battery pack, initialize the accumulated current value, and determine the SOC of the battery pack as equal to the sum of the SOC of the reference battery cell and a predetermined value.

[0015] The control circuit can be configured to determine the state of charge (SOC) of the cell group and the SOC of the reference cell based on the accumulated current value when the voltage of the reference cell is higher than the reference voltage.

[0016] The lower limit of the safe voltage range can be equal to or less than the OCV corresponding to the lower limit of the SOC range in the flat region. The upper limit of the safe voltage range can be equal to or greater than the OCV corresponding to the upper limit of the SOC range in the flat region.

[0017] The control circuit can be configured to determine that a fault exists in each of the multiple battery cells included in a cell group, which has a voltage lower than that of a reference battery cell.

[0018] The battery management system according to aspects of this disclosure is configured for a battery pack, the battery pack including a cell group and a reference cell connected in series with the cell group, the cell group including a plurality of cell groups connected in series. The reference cell and each cell in the cell group are configured to have a flat region, wherein the flat region is a predetermined SOC range in which the open-circuit voltage (OCV) remains below a predetermined reference value as the state of charge (SOC) changes. Under initial conditions immediately following the manufacture of the battery pack, the SOC of the reference cell is higher than the SOC of each cell in the cell group by a predetermined value. The battery management system includes: a battery monitoring device configured to detect the voltage of the reference cell and each of the plurality of cell groups, and to detect the current of the battery pack; and a control circuit operatively coupled to the battery monitoring device and configured to determine a cumulative current value of the battery pack current. The control circuit can be configured to: during the charging of the battery pack, when the voltage of the reference battery cell reaches a reference voltage that is higher than the upper limit of a predetermined safe voltage range, stop charging the battery pack, determine the SOC of the reference battery cell based on the reference voltage and the current of the battery pack, initialize the accumulated current value, and determine the SOC of the battery pack as equal to the difference between the SOC of the reference battery cell and a predetermined value.

[0019] The control circuit can be configured to determine the SOC of the cell group and the SOC of the reference cell based on the accumulated current value when the voltage of the reference cell is lower than the reference voltage.

[0020] According to another aspect of this disclosure, the battery pack includes a battery management system.

[0021] According to another aspect of this disclosure, the energy storage system includes a battery pack.

[0022] A battery management method according to another aspect of this disclosure can be executed by a battery management system. The battery management method includes determining a cumulative current value of the battery pack's current. The battery management method further includes: during the discharge of the battery pack, when the voltage of a reference battery cell reaches a reference voltage below the lower limit of a safe voltage range, stopping the discharge of the battery pack, and determining the state of charge (SOC) of the reference battery cell based on the reference voltage and the current of the battery pack; and initializing the cumulative current value, and determining the SOC of the battery pack to be equal to the sum of the SOC of the reference battery cell and a predetermined value.

[0023] A battery management method according to another aspect of this disclosure can be executed by a battery management system. The battery management method includes determining a cumulative current value of the battery pack's current. The battery management method further includes: during charging of the battery pack, when the voltage of a reference battery cell reaches a reference voltage higher than the upper limit of a safe voltage range, stopping charging of the battery pack, and determining the state of charge (SOC) of the reference battery cell based on the reference voltage and the battery pack's current; and initializing the cumulative current value and determining the SOC of the battery pack as equal to the difference between the SOC of the reference battery cell and a predetermined value.

[0024] Beneficial effects

[0025] According to at least one embodiment of the present disclosure, when multiple battery cells having a common flat region are connected in series within a cell group, the state of charge (SOC) of the cell group can be accurately, safely, and efficiently determined without intentionally charging or discharging the cell group to place the SOC of each battery cell outside the flat region.

[0026] The effects of this disclosure are not limited to those described above, and those skilled in the art will clearly understand these and other effects based on the appended claims. Attached Figure Description

[0027] The accompanying drawings illustrate exemplary embodiments of the present disclosure and, together with the following detailed description of the present disclosure, are intended to provide a further understanding of the technical solutions of the present disclosure, and therefore should not be construed as being limited to the drawings.

[0028] Figure 1 This is a schematic diagram illustrating, by way of example, the architecture of an energy storage system according to the present disclosure.

[0029] Figure 2 This is an exemplary schematic diagram showing the adjusted state of charge (SOC) of multiple battery cells, a reference battery cell, and a reference battery cell immediately following the manufacture of the battery pack.

[0030] Figure 3 This is an example of a graph showing the SOC-open circuit voltage (OCV) curve that reflects the plateau characteristics of a single battery cell.

[0031] Figure 4 This is an exemplary flowchart illustrating a battery management method according to a first embodiment of the present disclosure.

[0032] Figure 5 This is an exemplary flowchart illustrating a battery management method according to a second embodiment of the present disclosure.

[0033] Figure 6 This is an example showing the relationship with Figure 4The flowchart shown is a balancing method associated with the battery management method according to the first embodiment of this disclosure.

[0034] Figure 7 This is an example showing the relationship with Figure 5 The flowchart shown is a balancing method associated with the battery management method according to the second embodiment of this disclosure. Detailed Implementation

[0035] Exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms or words used in the specification and appended claims should not be construed as limited to their general or dictionary meanings, but rather are interpreted based on their meanings and concepts corresponding to the technical solutions of the present disclosure, on the basis of allowing the inventors to appropriately define the terms to obtain the best interpretation.

[0036] Therefore, the embodiments described herein and the accompanying drawings are merely preferred embodiments of this disclosure, but are not intended to completely describe the technical solutions of this disclosure. It should be understood that various other equivalents and modifications can be made to it when submitting this application.

[0037] Ordinal terms such as “first” and “second” are used to distinguish one element from another among various elements, but are not intended to limit the elements.

[0038] Unless the context clearly indicates otherwise, it should be understood that, when used in this specification, the term "comprising" specifies the presence of the stated element, but does not exclude the presence or addition of one or more other elements. Furthermore, as used herein, the term "control unit" refers to a processing unit having at least one function or operation, and can be implemented by hardware and software, alone or in combination.

[0039] Furthermore, throughout the specification, it should be understood that when an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intermediate element.

[0040] In the instruction manual, the state of charge (SOC) is the ratio of the remaining capacity of the minimum energy storage unit (e.g., a single battery cell or a group of cells) to the fully charged capacity of the minimum energy storage unit, indicated in terms of 0 to 100%.

[0041] Figure 1 This is a schematic diagram illustrating, by way of example, the architecture of an energy storage system according to this disclosure. Figure 2 This example illustrates multiple battery cells C1 to C1 immediately following the manufacture of the battery pack. m Reference cell C L and reference cell C U A schematic diagram of the adjusted SOC. Figure 3This is an example of a graph showing the SOC-open circuit voltage (OCV) curve that reflects the plateau characteristics of a single battery cell.

[0042] Reference Figure 1 The energy storage system 1 includes a battery pack 10, a relay 20, and a power conversion system 30.

[0043] The battery pack 10 includes a cell group 11, a current sensing device 12, and a battery management system 100. The battery pack 10 also includes a reference cell C. L Or refer to cell C U At least one of them. The battery pack 10 includes a reference battery cell C. L and reference cell C U The following description is based on the assumptions of both parties. It should be understood that the reference battery cell C can be considered... L Or refer to cell C U Remove from battery pack 10.

[0044] The single cell group 11 includes multiple battery cells C1 to C1 connected in series. m Where m is a natural number greater than 2. Refer to cell C. L and reference cell C U Connected in series to unit group 11. Although Figure 1 Reference cell C is shown L and reference cell C U Each of the cells is connected in series via the negative terminal of cell group 11, but this arrangement is for illustrative purposes. For example, refer to cell C. L Or refer to cell C U It can be connected in series to the positive terminal of the cell group 11, or it can be connected between any two cell groups (e.g., C1, C2) in the cell group 11.

[0045] In cell group 11, multiple battery cells C1 to C2 are included. m Each of the cells has a positive electrode lead and a negative electrode lead, and the positive electrode lead of one (e.g., C1) and the negative electrode lead of the other (e.g., C2) of two adjacent cell groups (e.g., C1, C2) are joined by welding. Therefore, in cell group 11, a connection is provided from the negative electrode lead of cell C1 to the negative electrode lead of cell C2. m The positive lead of the battery cell is connected in series. In the following text, note that the positive lead and negative lead of the battery cell C can be referred to as the "positive electrode" and "negative electrode", respectively.

[0046] Multiple battery cells C1 to C1 can be manufactured according to the same electrical and chemical specifications and charge / discharge characteristics. m Reference cell C L and reference cell C UIn the following text, multiple battery cells C1 to C1 are discussed. m Reference cell C L and reference cell C U In the common description, the reference numeral "C" is used to indicate a single battery cell. The battery cell C is not limited to a specific type and can include any type of battery cell that is rechargeable and has plateau characteristics, such as a lithium phosphate (LFP) battery.

[0047] Provide reference cell C L This is to reset the SOC of the cell pack 11 and prevent over-discharge / under-voltage during the discharge of the battery pack 10. Under the initial conditions immediately following the manufacture of the battery pack 10, all the multiple battery cells C1 to C2 of the cell pack 11 are... m Adjusted to have the same SOC, referencing the cell C L The SOC is adjusted to match the multiple battery cells C1 to C1 of the single-cell group 11. m Compared to the lower first predetermined value ΔZ L .

[0048] Provide reference cell C U This is to reset the SOC of the cell pack 11 and prevent overcharging / overvoltage during the charging of the battery pack 10. Under the initial conditions immediately following the manufacture of the battery pack 10, all the multiple battery cells C1 to C2 of the cell pack 11 are... m Adjusted to have the same SOC, referencing the cell C U The SOC is adjusted to match the multiple battery cells C1 to C1 of the single-cell group 11. m Compared to the second predetermined value ΔZ U .

[0049] Reference Figure 2 When the first predetermined value ΔZ L The second predetermined value is 2%, ΔZ. U When the percentage is 3%, immediately after manufacturing the battery pack 10, all the multiple battery cells C1 to C2 are... m The SOC is adjusted to 25%, referencing the C of the battery cell. L The SOC was adjusted to 23%, and the reference cell C was adjusted. U The SOC is adjusted to 28%. In this case, under initial conditions, the battery management system can determine that the SOC of cell group 11 is equal to that of multiple battery cells C1 to C1. m SOC 25%.

[0050] Cell group 11, reference cell C L and reference cell C U The series circuit can be electrically connected to the power conversion system 30 via relay 20.

[0051] Relay 20 is mounted on power line PL, which serves as the current path for charging / discharging battery pack 10. When relay 20 is turned on, power can be transferred from either battery pack 10 to the other power conversion system 30. Relay 20 can be implemented as at least one of known switching devices, such as a mechanical contactor and a field-effect transistor (FET). Control circuit 130 can control relay 20 to switch from one state to the other, either on or off.

[0052] The power conversion system 30 is operatively coupled to the battery management system 100 via the upper-level controller 2. The power conversion system 30 can generate direct current (DC) power for charging the battery pack 10 from alternating current (AC) power supplied by the power grid 40. The power conversion system 30 can also generate AC power from the DC power supplied by the battery pack 10.

[0053] The battery management system 100 is configured to monitor multiple battery cells C1 to C2. m Reference cell C L and reference cell C U The condition of each of them.

[0054] The battery management system 100 includes a battery monitoring circuit 110 and a control circuit 130. The battery management system 100 may also include at least one of a cell balancer 120 or a communication circuit 140.

[0055] The battery monitoring circuit 110 is configured to sense voltages from multiple battery cells C1 to C2 via a voltage sensing channel that includes multiple sensing lines. m Reference cell C L and reference cell C U The positive and negative terminals of each of them are electrically connected.

[0056] Battery monitoring circuit 110 uses the potential difference between a pair of sensing lines connected to the positive and negative terminals of battery cell C to detect the voltage across battery cell C. Battery monitoring circuit 100 can transmit a voltage signal indicating the detected voltage of battery cell C to control circuit 130 via analog-to-digital conversion.

[0057] Battery monitoring circuit 110 is operatively coupled to current sensing device 12 via a pair of additional sensing lines. Current sensing device 12 is mounted on power line PL and may include, for example, a shunt resistor and a Hall effect device. When the shunt resistor is used as current sensing device 12, battery monitoring circuit 110 can detect the current flowing through battery pack 10 based on the potential difference across current sensing device 12. Battery monitoring circuit 110 can transmit a current signal indicating the amplitude and direction of the detected current to control circuit 130 via analog-to-digital conversion.

[0058] The control circuit 130 is operatively coupled to the relay 20, the battery monitoring circuit 110, the cell balancer 120, and / or the communication circuit 140. Operable coupling refers to a direct / indirect connection for transmitting and receiving signals in one or both directions.

[0059] The control circuit 130 may be implemented in hardware using at least one of a digital signal processor (DSP), a digital signal processing device (DSPD), a programmable logic device (PLD), a field-programmable gate array (FPGA), a microprocessor, or an electrical unit for performing other functions.

[0060] The control circuit 130 may have embedded memory. The memory may store programs and data required to execute the battery management method according to the embodiments described below. The memory may include at least one type of storage medium, such as flash memory, hard disk, solid-state drive (SSD), silicon disk drive (SDD), multimedia card micro, random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), or programmable read-only memory (PROM).

[0061] The control circuit 130 can collect voltage and current signals from the battery monitoring circuit 110 at set time intervals (e.g., 1 second) and record them in a memory. Because the current signal includes current direction information, the control circuit 130 can determine whether the battery pack 10 is being charged or discharged, or whether the battery pack 10 is in a resting state, based on the current signal. Resting (or resting state) refers to the state in which charging and discharging of the battery pack 10 has stopped.

[0062] The control circuit 130 can use an ampere counter to determine the cumulative current based on the current signal. The cumulative current at any time is the total current accumulated from the time of the last initialization of the cumulative current before the corresponding time to the corresponding time.

[0063] Communication circuitry 140 can be coupled to an upper-level controller 2 of energy storage system 1 to enable communication between them. Communication circuitry 140 can transmit messages from upper-level controller 2 to control circuitry 130, and vice versa. Messages from control circuitry 130 may include information for notifying the status of individual battery cells C (e.g., voltage, SOC, over-discharge, under-voltage, overcharge, overvoltage). For communication between communication circuitry 140 and upper-level controller 2, wired networks such as local area networks (LAN), controller area networks (CAN), and daisy-chaining, and / or near-field wireless networks such as Bluetooth, Zigbee, and WiFi, can be used. Communication circuitry 140 may include output devices (e.g., displays, speakers) to provide information received from control circuitry 130 and / or upper-level controller 2 in a recognizable format. Upper-level controller 2 can control power conversion system 30 based on information collected via communication with battery management system 100.

[0064] Reference Figure 3 The memory of control circuit 130 pre-records indications for the flat region Z. A ~Z B 1. Safe voltage range V1~V2; 2. Reference voltage V for over-discharge / under-voltage prevention. L and the reference voltage V used for overcharge / overvoltage prevention U And data from the SOC-OCV curve 300.

[0065] The OCV of the battery cell C in the flat region Z A ~Z B It remains almost uniformly consistent over the flat region Z. A ~Z B In the mean region Z, the OCV remains below a predetermined reference value as the SOC changes (e.g., the derivative). Conversely, in the flat region Z... A ~Z B The remaining range (0 to Z) A %, Z B Within the range of ~100%, the change of OCV with SOC is greater than the predetermined reference value, so the SOC corresponding to OCV can be determined within the predetermined error range.

[0066] It is known that most rechargeable batteries, including individual cells C, degrade faster when continuously used outside the optimal range at SOC of 0% or near SOC of 100%. Considering the relationship between SOC and the degradation rate of individual cell C, a preset safe voltage range V1 to V2 is established. The SOC (Z1) corresponding to the lower limit V1 of the safe voltage range V1 to V2 is equal to or lower than the lower limit Z of the flat region. AThe corresponding OCV. The SOC(Z2) corresponding to the upper limit V2 of the safe voltage range V1~V2 is equal to or higher than the upper limit Z of the flat region. B The range between Z1 and Z2, corresponding to the safe voltage range V1 to V2, can be called the safe SOC range, and the safe SOC region Z1 to Z2 can be equal to or wider than the flat region Z. A ~Z B .

[0067] Reference voltage V L The voltage is equal to or lower than the lower limit V1 of the safe voltage range V1 to V2. The control circuit 130 can determine the voltage relative to the reference voltage V based on the SOC-OCV curve 300. L Corresponding SOC(Z) L ).

[0068] Reference voltage V U It is equal to or higher than the upper limit V2 of the safe voltage range V1 to V2. The control circuit 130 can determine the voltage relative to the reference voltage V based on the SOC-OCV curve 300. U Corresponding SOC(Z) U ).

[0069] First predetermined value ΔZ L It can be equal to SOC(Z) L The difference between Z1 and SOC(Z1). Second predetermined value ΔZ U It can be equal to SOC(Z) U The difference between SOC(Z2) and SOC(Z2).

[0070] The battery balancer 120 is configured to balance multiple battery cells C1 to C2 in response to a command from the control circuit 130. m Reference cell C L and reference cell C U Each of the cells undergoes selective discharge. The battery balancer 120 includes multiple battery cells C1 to C2 arranged in a one-to-one relationship. m Multiple discharge circuits D1 to D2 are configured. m The battery balancer 120 may also include a reference battery cell C. U The discharge circuit D is set U And for reference battery cell C L The discharge circuit D is set L When the reference cell C is omitted from the battery pack L Or refer to cell C U When, it can be omitted as the reference battery cell C L Or refer to cell C U The discharge circuit D is set L Or discharge circuit D U .

[0071] The battery monitoring circuit 110 and the battery balancer 120 can be integrated into a single integrated circuit. For example, the battery monitoring circuit 110 and the battery balancer 120 can be implemented using an application-specific integrated circuit (ASIC) such as the BQ76940, which is capable of voltage monitoring, current monitoring, and cell balancing.

[0072] Multiple discharge circuits D1 to D m D L D U Each of these circuits is a series circuit of a discharge resistor R and a switch SW, and is connected in parallel with the corresponding battery cell C. Multiple discharge circuits D1 to D2... m D L D U Each of the switches SW in the circuit responds to a command from the control circuit 130 to switch from the off state to the on state. When the switch SW of the discharge circuit (e.g., D1) is in the on state, the SOC and voltage of the battery cell (e.g., C1) gradually decrease by consuming the energy stored in the corresponding battery cell (e.g., C1) through the discharge resistor R of the discharge circuit (e.g., D1).

[0073] Control circuit 130 can determine that during the charging, discharging, or resting periods of battery pack 10, multiple battery cells C1 to C2 are in operation. m Among them, the voltage is equal to or lower than the reference cell C L Each cell C in the battery cell has a faulty voltage.

[0074] Control circuit 130 can determine that during the charging, discharging, or resting periods of battery pack 10, multiple battery cells C1 to C2 are in operation. m Among them, the voltage is equal to or higher than that of the reference cell C. U Each cell C in the battery cell has a faulty voltage.

[0075] Figure 4 This is an exemplary flowchart illustrating a battery management method according to a first embodiment of the present disclosure. When the battery pack 10 is charged / discharged during its period or the battery pack 10 is in a resting state for less than the time including the reference battery cell C... L When the battery pack 10 is stored for a predetermined period after its manufacturing time, the battery management system can periodically execute the following actions at set time intervals. Figure 4 The method.

[0076] Reference Figures 1 to 4 In step S410, the control circuit 130 determines the reference battery cell C. L and multiple battery cells C1~C mThe voltage of each of the components is measured, and the current of the battery pack 10 is determined based on the voltage and current signals collected from the battery monitoring circuit.

[0077] In step S420, the control circuit 130 determines the cumulative current value of the battery pack 10. The control circuit 130 determines the cumulative current value of the current cycle by adding the value obtained by multiplying the current of the battery pack 10 determined in the current cycle by a set time to the cumulative current value of the previous cycle. For example, if the cumulative current value of the previous cycle is 10 Ah, the current of the battery pack 10 in the current cycle is -1 A, and the set time is 1 second = 1 / 3600 hours, the cumulative current value of the current cycle is determined to be (10 - 1 / 3600) Ah.

[0078] In step S430, control circuit 130 determines whether the battery pack is being discharged. If the value of step S430 is "yes", step S440 is executed. If the value of step S430 is "no", step S470 is executed.

[0079] In step S440, the control circuit 130 determines the reference battery cell C. L Whether the voltage reaches the reference voltage V1 below the lower limit of the safe voltage range. L For reference, when all multiple battery cells C1~C m Under normal conditions, refer to cell C. L The voltage is lower than that of multiple battery cells C1 to C2. m The voltage of multiple battery cells C1 to C m The voltage is higher than the reference voltage V. L If the value of step S440 is "Yes", proceed to step S450. If the value of step S440 is "No", proceed to step S470.

[0080] In step S450, the control circuit 130 stops discharging the battery pack 10 (e.g., turns off the relay 20) and based on the reference voltage V L The current of battery pack 10 is determined by reference battery cell C. L The SOC. This is determined by comparing the current of battery pack 10 with the reference cell C. L The voltage drop corresponding to the product of the internal resistances and the reference voltage V L By adding them together, control circuit 130 can determine the reference battery cell C. L The OCV, and based on the reference cell C L The OCV is determined based on the SOC-OCV curve 300, which serves as the reference cell C. L The SOC. For example, when the reference cell C L When the internal resistance is 0.001Ω, the reference voltage V LThe voltage is 3.0V, the current of battery pack 10 is 10A, the voltage drop can be determined to be 0.01V, and reference is made to the cell C. L The OCV can be determined to be 3.01V. Reference cell C L The internal resistance value can be a preset value recorded in the memory of the control circuit 130. Alternatively, the control circuit 130 can adjust the internal resistance value based on Ohm's law and a set time interval, according to the reference battery cell C. L The ratio between the voltage change and the current change of battery pack 10 is used to determine the reference battery cell C. L The internal resistance.

[0081] In step S460, the control circuit 130 initializes the accumulated current value (e.g., accumulated current value = 0Ah) and determines the SOC of the cell group 11 to be equal to the SOC of the reference cell plus a first predetermined value ΔZ. L sum.

[0082] Steps S450 and S460 are the “SOC reset” process for the cell group 11 being discharged. That is, step S460 removes most of the current error included in the accumulated current value from the latest reset time when the SOC of the last cell group 11 was reset to the current cycle.

[0083] In step S470, control circuit 130 determines the SOC of individual unit group 11 based on the accumulated current value. For example, by adding the SOC change corresponding to the accumulated current value from the latest reset time when the SOC of individual unit group 11 was last reset to the current cycle, control circuit 130 can determine the SOC of individual unit group 11 in the current cycle.

[0084] Figure 5 This is an exemplary flowchart illustrating a battery management method according to a second embodiment of the present disclosure. The battery pack 10 is charged / discharged or remains in a dormant state for a period less than the time including the reference battery cell C. U When the battery pack 10 is stored for a predetermined period after its manufacturing time, the battery management system can periodically execute the following actions at set time intervals. Figure 5 The method.

[0085] Reference Figures 1 to 5 In step S510, the control circuit 130 determines the reference battery cell C. U and multiple battery cells C1~C m The voltage of each of the components is measured, and the current of the battery pack 10 is determined based on the voltage and current signals collected from the battery monitoring circuit.

[0086] In step S520, the control circuit 130 determines the cumulative current value of the battery pack 10. The control circuit 130 determines the cumulative current value of the current cycle by adding the value obtained by multiplying the current of the battery pack 10 determined in the current cycle by a set time to the cumulative current value of the previous cycle. For example, if the cumulative current value of the previous cycle is 20 Ah, the current of the battery pack 10 in the current cycle is 10 A, and the set time is 1 second = 1 / 3600 hours, the cumulative current value of the current cycle is determined to be (20 + 10 / 3600) Ah.

[0087] In step S530, the control circuit 130 determines whether the battery pack is being charged. If the value of step S530 is "yes", step S540 is executed. If the value of step S530 is "no", step S570 is executed.

[0088] In step S540, the control circuit 130 determines the reference battery cell C. U Does the voltage reach the upper limit of the safe voltage range, V2, or the reference voltage V? U For reference, when all multiple battery cells C1~C m Under normal conditions, refer to cell C. U The voltage is higher than that of multiple battery cells C1 to C2. m The voltage, and therefore multiple battery cells C1 to C m The voltage is lower than the reference voltage V. U If the value of step S540 is "Yes", proceed to step S550. If the value of step S540 is "No", proceed to step S570.

[0089] In step S550, the control circuit 130 stops charging the battery pack 10 (e.g., turns off the relay 20), and based on the reference voltage V U The current of battery pack 10 is determined by reference battery cell C. U SOC. (Based on reference voltage V) U Subtract the current of battery pack 10 and the reference cell C U The voltage rises corresponding to the product of the internal resistances, and the control circuit 130 can determine the reference battery cell C. U The OCV, and based on the reference cell C U The OCV is determined based on the SOC-OCV curve 300, which serves as the reference cell C. U The SOC. For example, when the reference cell C U Its internal resistance is 0.001Ω, and the reference voltage is V. U At a voltage of 3.6V, and with a current of 10A for battery pack 10, the voltage rise can be determined to be 0.01V, and reference can be made to the cell C. UThe OCV can be determined to be 3.59V. Reference cell C U The internal resistance value can be a preset value recorded in the memory of the control circuit 130. Alternatively, the control circuit 130 can adjust the internal resistance value based on Ohm's law and a set time interval, according to the reference battery cell C. U The ratio between the voltage change and the current change of battery pack 10 is used to determine the reference battery cell C. U The internal resistance.

[0090] In step S560, the control circuit 130 initializes the accumulated current value (e.g., accumulated current value = 0Ah) and determines the SOC of the cell group 11 to be equal to that of the reference cell C. U SOC and the second predetermined value ΔZ U The difference between them.

[0091] Steps S550 and S560 are the "SOC reset" process for the cell group 11 being charged. That is, step S560 removes most of the current error included in the accumulated current value from the latest reset time when the SOC of the last cell group 11 was reset to the current cycle.

[0092] In step S570, control circuit 130 determines the SOC of individual unit group 11 based on the accumulated current value. For example, by adding the SOC change corresponding to the accumulated current value from the latest reset time when the SOC of individual unit group 11 was last reset to the current cycle, control circuit 130 can determine the SOC of individual unit group 11 in the current cycle.

[0093] Figure 6 This is an example showing the relationship with Figure 4 A flowchart of a balancing method associated with the battery management method according to the first embodiment. When the battery pack 10 remains in a resting state for a predetermined storage time or longer after manufacturing, the battery management system 100 can perform... Figure 6 The method. Storage time is the time required to resolve the polarization voltage of the battery cell C caused by charging / discharging of the battery pack 10. When the battery pack 10 remains in a resting state for a predetermined storage time or longer, the voltage detected from the battery cell C can be regarded as OCV.

[0094] Reference Figure 1 , Figure 3 and Figure 6 In step S610, the control circuit 130 determines the reference battery cell C. L voltage ( Figure 3 V in P Is it within the lower limit of the safe voltage range V1 and the reference voltage V? LBetween. When the value of step S610 is "Yes", proceed to step S620.

[0095] In step S620, the control circuit 130 will compare the reference battery cell C with the reference battery cell C. L voltage ( Figure 3 V in Q The corresponding SOC high first predetermined value ΔZ L The corresponding OCV of SOC ( Figure 3 V in P Set the target voltage.

[0096] In step S630, the control circuit 130 determines the multiple battery cells C1 to C2 of the cell group 11. m Is the voltage of at least one of them lower than the target voltage? Figure 3 V in P The value of step S630 is "Yes", indicating that multiple battery cells C1 to C2 are "Yes". m At least one of them is related to the reference battery cell C L The SOC difference between them is less than the first predetermined value ΔZ L If the value of step S630 is "Yes", proceed to step 640. If the value of step S630 is "No", proceed to step 650.

[0097] In step S640, the control circuit 130 controls the single-cell balancer 120 to balance the reference battery cell C. L Discharge until the reference cell C is reached. L The voltage reaches the reference voltage V L In other words, the single-cell balancer 120, in response to the command from the control circuit 130, connects to the reference battery cell C. L Parallel discharge circuit D L The switch SW.

[0098] In step S650, the control circuit 130 controls the single-cell balancer 120 to balance multiple battery cells C1 to C2. m Discharge continues until multiple battery cells C1 to C1 in cell group 11 are discharged. m The voltage of each battery cell in the system reaches the target voltage. Figure 3 V in P Through step S650, multiple battery cells C1 to C2 can be... m Each of them is related to the reference cell C L The SOC difference between them is adjusted to be equal to the first predetermined value ΔZ. L .

[0099] Figure 7 This is an example showing the relationship with Figure 5A flowchart of a balancing method associated with the battery management method according to the second embodiment. When the resting state of the battery pack 10 remains in a predetermined storage time or longer after the manufacturing time of the battery pack 10, it can be performed by the battery management system 100. Figure 7 The method.

[0100] Reference Figure 1 , Figure 3 and Figure 7 In step S710, the control circuit 130 determines the reference battery cell C. U voltage ( Figure 3 V in X Is it within the upper limit of the safe voltage range V2 and the reference voltage V? U Between. When the value of step S710 is "Yes", step S720 is executed.

[0101] In step S720, the control circuit 130 will compare the reference battery cell C with the reference battery cell C. U voltage ( Figure 3 V in X The corresponding SOC lower second predetermined value ΔZ U The corresponding OCV of SOC ( Figure 3 V in Y Set the target voltage.

[0102] In step S730, the control circuit 130 determines the multiple battery cells C1 to C2 of the cell group 11. m Is the voltage of at least one of them higher than the target voltage? Figure 3 V in Y When the value of step S730 is "Yes", proceed to step 740.

[0103] In step S740, the control circuit 130 controls the cell balancer 120 to discharge each battery cell (e.g., C1) until multiple battery cells C1 to C1 in the cell group 11 are discharged. m Among them, the voltage of each battery cell (e.g., C1) with a voltage higher than the target voltage reaches the target voltage. Figure 3 V in Y Through step S740, multiple battery cells C1 to C2 can be... m Each of them is related to the reference cell C U The SOC difference between them is adjusted to be equal to the second predetermined value ΔZ. U .

[0104] The first and second embodiments described above are not merely alternatives, but the battery management system 100 can be configured to perform both the battery management function according to the first embodiment and the battery management function according to the second embodiment.

[0105] The embodiments of the present disclosure described above can be implemented not only by apparatus and methods, but also by a program that performs functions corresponding to the configuration of the embodiments of the present disclosure, or by a recording medium on which a program is recorded. Furthermore, those skilled in the art can easily implement these implementation methods based on the disclosure of the above embodiments.

[0106] While this disclosure has been described above with respect to a limited number of embodiments and accompanying drawings, this disclosure is not limited thereto, and it will be apparent to those skilled in the art that various modifications and variations can be made to it within the equivalent scope of the technical solutions of this disclosure and the appended claims.

[0107] Furthermore, since those skilled in the art can make many substitutions, modifications and changes to the present disclosure without departing from the technical solution of the present disclosure, the present disclosure is not limited to the above embodiments and drawings, and some or all of the embodiments can be selectively combined to allow for various modifications.

[0108] (Description of reference numerals in the attached diagram)

[0109] 1: Energy storage system

[0110] 10: Battery pack 11: Individual cell pack C1~C m Battery cell

[0111] C L C U Reference battery cell

[0112] 20: Relay

[0113] 30: Power conversion system

[0114] 100: Battery Management System

[0115] 110: Battery monitoring circuit

[0116] 120: Individual Balancer

[0117] 130: Control circuit

[0118] 140: Communication circuits

Claims

1. A battery management system for a battery pack, the battery pack comprising a cell group and a reference battery cell connected in series with the cell group, the cell group comprising a plurality of battery cells connected in series, wherein, The reference battery cell and each battery cell in the cell group are configured to have a flat region, wherein the flat region is a predetermined SOC range in which the open-circuit voltage (OCV) remains below a predetermined reference value as the state of charge (SOC) changes. Specifically, under the initial conditions immediately following the manufacture of the battery pack, the SOC of the reference battery cell is lower than the SOC of each battery cell in the battery pack by a predetermined value. The battery management system includes: A battery monitoring device configured to detect the voltage of the reference battery cell and each of the plurality of battery cells, and to detect the current of the battery pack; and A control circuit, operatively coupled to the battery monitoring device and configured to determine a cumulative current value of the battery pack's current, and The control circuit is configured to: during the discharge of the battery pack, when the voltage of the reference battery cell reaches a reference voltage lower than the lower limit of a predetermined safe voltage range, stop discharging the battery pack; determine the state of charge (SOC) of the reference battery cell based on the reference voltage and the current of the battery pack; initialize the accumulated current value; and determine the SOC of the battery pack as equal to the sum of the SOC of the reference battery cell and the predetermined value. Wherein, the lower limit of the safe voltage range is equal to or less than the OCV corresponding to the lower limit of the SOC range of the flat region, and the upper limit of the safe voltage range is equal to or greater than the OCV corresponding to the upper limit of the SOC range of the flat region.

2. The battery management system according to claim 1, wherein, The control circuit is configured to determine the state of charge (SOC) of the cell group and the SOC of the reference cell based on the accumulated current value when the voltage of the reference cell is higher than the reference voltage.

3. The battery management system according to claim 1, wherein, The control circuit is configured to determine that each of the plurality of battery cells included in the cell group has a voltage lower than that of the reference battery cell, and that a fault exists in each of the battery cells.

4. A battery management system for a battery pack, the battery pack comprising a cell group and a reference battery cell connected in series with the cell group, the cell group comprising a plurality of battery cells connected in series, wherein, The reference battery cell and each battery cell in the cell group are configured to have a flat region, wherein the flat region is a predetermined SOC range in which the open-circuit voltage (OCV) remains below a predetermined reference value as the state of charge (SOC) changes. Specifically, under the initial conditions immediately following the manufacture of the battery pack, the state of charge (SOC) of the reference battery cell is higher by a predetermined value than the SOC of each battery cell in the battery pack. The battery management system includes: A battery monitoring device configured to detect the voltage of the reference battery cell and each of the plurality of battery cells, and to detect the current of the battery pack; and A control circuit, operatively coupled to the battery monitoring device and configured to determine a cumulative current value of the battery pack's current, and The control circuit is configured to: during the charging of the battery pack, when the voltage of the reference battery cell reaches a reference voltage higher than the upper limit of a predetermined safe voltage range, stop charging the battery pack; determine the state of charge (SOC) of the reference battery cell based on the reference voltage and the current of the battery pack; initialize the accumulated current value; and determine the SOC of the battery pack as equal to the difference between the SOC of the reference battery cell and the predetermined value. Wherein, the lower limit of the safe voltage range is equal to or less than the OCV corresponding to the lower limit of the SOC range of the flat region, and the upper limit of the safe voltage range is equal to or greater than the OCV corresponding to the upper limit of the SOC range of the flat region.

5. The battery management system according to claim 4, wherein, The control circuit is configured to determine the state of charge (SOC) of the cell group and the SOC of the reference cell based on the accumulated current value when the voltage of the reference cell is lower than the reference voltage.

6. A battery pack comprising a battery management system according to any one of claims 1 to 5.

7. An energy storage system comprising a battery pack according to claim 6.

8. A battery management method executable by a battery management system according to any one of claims 1 to 3, the battery management method comprising: Determine the cumulative current value of the battery pack. The battery management method further includes: During the discharge of the battery pack, when the voltage of the reference battery cell reaches a reference voltage that is below the lower limit of the safe voltage range, Stop discharging the battery pack and determine the SOC of the reference cell based on the reference voltage and the current of the battery pack; and The accumulated current value is initialized, and the SOC of the cell group is determined to be equal to the sum of the SOC of the reference cell and the predetermined value.

9. A battery management method executable by a battery management system according to claim 4 or 5, the battery management method comprising: Determine the cumulative current value of the battery pack. The battery management method further includes: During the charging of the battery pack, when the voltage of the reference battery cell reaches a reference voltage that is higher than the upper limit of the safe voltage range, Stop charging the battery pack and determine the SOC of the reference battery cell based on the reference voltage and the current of the battery pack; and The accumulated current value is initialized, and the SOC of the cell group is determined to be equal to the difference between the SOC of the reference cell and the predetermined value.

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