Battery management system. battery pack, electric vehicle and battery management method

Abstract

To provide a battery management system capable of accurately detecting a defect battery due to an internal short circuit among a plurality of batteries even in a state where a voltage uneven state among the plurality of batteries has been dissolved by balancing processing.SOLUTION: A battery management system 100 includes: a battery monitor 110 that acquires respective voltages of a plurality of batteries B1-BN; and a processor that uses balancing capacity of each battery by balancing processing performed in the past to compensate a no-load voltage value of each battery in a state where the balancing processing is not performed for the plurality of batteries, determines a voltage difference as a difference between the compensated no-load voltage value and a reference voltage value for each battery, and detects whether or not each battery has an abnormality on the basis of a change amount of the voltage difference for each battery.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a technique for detecting an internal short circuit fault in a battery.

[0002] This application claims priority to Korean Patent Application No. 10-2021-0098141, filed on July 26, 2021, the entire contents of which are incorporated herein by reference in their entirety in the specification and drawings of that application. [Background technology]

[0003] Recently, as the demand for portable electronic products such as notebook PCs, video cameras, and mobile phones has increased sharply and the development of electric vehicles, energy storage batteries, robots, satellites, etc. has progressed in earnest, research into high-performance batteries that can be repeatedly charged and discharged is progressing actively.

[0004] Currently, commercial batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium batteries. Of these, lithium batteries are in the spotlight due to their advantages over nickel-based batteries, such as almost no memory effect, freedom to charge and discharge, a very low self-discharge rate, and high energy density.

[0005] 2. Description of the Related Art In order to meet the high voltage and large capacity requirements of applications such as electric vehicles, battery systems (e.g., battery packs) including at least one battery group (i.e., a series connection of a plurality of batteries) have become widespread.

[0006] In such a battery system, the failure of some batteries is likely to adversely affect the overall performance and safety of the battery system, so it is important to properly detect the failure of individual batteries when operating the battery system.

[0007] Batteries have characteristic differences due to internal and external factors during the manufacturing process and / or use. The characteristic differences between batteries cause voltage unevenness. Balancers are widely used to balance (e.g., discharge) each of the batteries and eliminate voltage unevenness between the batteries.

[0008] Among the various types of battery failures, an internal short circuit is the main failure that directly or indirectly affects fires. An internal short circuit is a condition in which a leakage current path is created due to side reactions within the battery and / or the penetration of foreign matter into the battery. Conventionally, batteries with internal short circuit failures were detected among multiple batteries using the voltage unevenness of multiple batteries.

[0009] However, when the balancing process is performed, the voltage unevenness of the multiple batteries, which is important information for detecting an internal short circuit fault, is eliminated. In other words, when detecting a battery with an internal short circuit fault from multiple batteries, the balancing process that was previously performed acts as an interference factor. Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made in consideration of the above problems, and has an object to provide a battery management system, a battery pack, an electric vehicle, and a battery management method that can accurately detect a battery having an internal short circuit fault among multiple batteries even when the voltage unevenness among multiple batteries has been eliminated by a balancing process.

[0011] Other objects and advantages of the present invention will become apparent from the following description and the accompanying drawings, in which: FIG. 1 is a block diagram of a method for manufacturing a semiconductor device according to the present invention; [Means for solving the problem]

[0012] According to one aspect of the present invention, a battery management system includes a battery monitor that acquires a voltage of each of a plurality of batteries, and a processor that, when a balancing process for the plurality of batteries has not been performed, compensates for a no-load voltage value of each of the batteries using a balancing capacity of each battery resulting from a previously performed balancing process, determines a voltage difference between the compensated no-load voltage value of each of the batteries and a reference voltage value, and detects whether or not each of the batteries is abnormal based on an amount of change in the voltage difference of each of the batteries.

[0013] The processor may be configured to increase a fault count of each battery by one if the change in the voltage difference of each battery is equal to or greater than a critical value, and to detect each battery as having an internal short circuit fault if the fault count of each battery is equal to or greater than a predetermined value.

[0014] The reference voltage value may be an average or median of the compensated no-load voltage values ​​of at least two batteries among the plurality of batteries.

[0015] The processor may compensate the no-load voltage value using a balancing capacity obtained by a balancing process performed during a reference time, the reference time being longer than a time for performing the balancing process.

[0016] The processor may be configured to accumulate discharge capacities of each of the batteries due to each balancing process performed within a reference time period to determine the balancing capacity of each of the batteries.

[0017] The processor may be configured to apply a capacity estimation function to first balancing data associated with each balancing process to determine the discharge capacity of each of the batteries due to each balancing process. The first balancing data may include a no-load voltage value of each of the batteries at the start of the balancing process and a duration of the balancing process.

[0018] The processor may be configured to apply a SOC-OCV map to second balancing data for each balancing process to determine the discharge capacity of each battery due to each balancing process. The second balancing data may include a no-load voltage value for each battery at a start of the balancing process and a no-load voltage value for each battery at an end of the balancing process.

[0019] The processor may be configured to apply a SOC-OCV map to the no-load voltage value of each of the batteries to determine an estimated SOC for each of the batteries, compensate the estimated SOC for each of the batteries by combining the estimated SOC value of each of the batteries with an amount of SOC change corresponding to the balancing capacity, and apply the SOC-OCV map to the compensated estimated SOC value of each of the batteries to determine the compensated no-load voltage value.

[0020] A battery pack according to another aspect of the present invention includes the battery management system.

[0021] According to yet another aspect of the present invention, an electric vehicle includes the battery pack described above.

[0022] According to yet another aspect of the present invention, a battery management method includes the steps of: acquiring a no-load voltage value of each of a plurality of batteries; compensating for the no-load voltage value of each of the batteries using a balancing capacity of each battery obtained by a balancing process performed in the past when a balancing process has not been performed on the plurality of batteries; determining a voltage difference between the compensated no-load voltage value of each of the batteries and a reference voltage value; and detecting whether or not each of the batteries has an abnormality based on an amount of change in the voltage difference of each of the batteries.

[0023] The step of detecting whether or not each battery has an abnormality may include the steps of: increasing a fault count of each battery by 1 when the amount of change in the voltage difference of each battery is equal to or greater than a critical value; and detecting each battery as having an internal short fault when the fault count of each battery is equal to or greater than a predetermined value.

[0024] The reference voltage value is an average or median of the compensated no-load voltage values ​​of at least two batteries among the plurality of batteries.

[0025] The step of compensating the no-load voltage value of each battery may include the steps of: applying an SOC-OCV map to the no-load voltage value of each battery to determine an estimated SOC value of each battery; compensating the estimated SOC value of each battery by adding an SOC change amount corresponding to the balancing capacity to the estimated SOC value of each battery; and applying the SOC-OCV map to the compensated estimated SOC value of each battery to determine the compensated no-load voltage value. Effect of the Invention

[0026] According to at least one of the embodiments of the present invention, even in a state in which the voltage unevenness among the plurality of batteries is eliminated by the balancing process, it is possible to accurately detect a battery having an internal short circuit fault among the plurality of batteries.

[0027] The effects of the present invention are not limited to the effects described above, and other effects of the present invention not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0028] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention, serve to further understand the technical ideas of the present invention. Therefore, the present invention should not be interpreted as being limited to only the matters described in the drawings. [Brief description of the drawings]

[0029] [Figure 1] 1 is a diagram showing the configuration of an electric vehicle according to the present invention; [Diagram 2] FIG. 2 is a reference diagram for explaining an exemplary equivalent circuit of a battery. [Diagram 3] FIG. 2 is a reference diagram for explaining the principle of detecting an internal short circuit fault in a battery. [Figure 4] FIG. 2 is a reference diagram for explaining the principle of detecting an internal short circuit fault in a battery. [Diagram 5] FIG. 2 is a reference diagram for explaining the principle of detecting an internal short circuit fault in a battery. [Figure 6] FIG. 2 is a reference diagram for explaining the principle of detecting an internal short circuit fault in a battery. [Figure 7] 2 is a flowchart illustrating a battery management method according to a first embodiment of the present invention. [Figure 8] 2 is a flowchart illustrating a battery management method according to a first embodiment of the present invention. [Figure 9] 5 is a flowchart illustrating a battery management method according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings. Prior to this, the terms and words used in the specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as having meanings and concepts corresponding to the technical ideas of the present invention, in accordance with the principle that the inventor himself can appropriately define the concepts of terms in order to best describe the invention.

[0031] Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiment of the present invention and do not represent the entire technical idea of ​​the present invention, and that there may be various equivalents and modifications that can be substituted for them at the time of this application.

[0032] Terms including ordinal numbers such as "first", "second", etc. are used for the purpose of distinguishing one of various components from the rest, and are not intended to limit the components.

[0033] In addition, throughout the specification, when a part "includes" a certain element, this does not mean excluding other elements, but means that other elements may be further included, unless otherwise specified. Furthermore, terms such as "controller" in the specification refer to a unit that processes at least one function or operation, which may be embodied by hardware, software, or a combination of hardware and software.

[0034] Furthermore, throughout this specification, when a part is said to be "connected" to another part, this includes not only when it is "directly connected" to another part, but also when it is "indirectly connected" through another element in between.

[0035] FIG. 1 is a diagram showing the configuration of an electric vehicle according to the present invention.

[0036] 1, an electric vehicle 1 includes a vehicle controller 2, a battery pack 10, and an electric load 30. Charging and discharging terminals P+, P- of the battery pack 10 may be electrically coupled to a charger 40 by a charging cable or the like. The charger 40 may be included in the electric vehicle 1 or may be provided in a charging station external to the electric vehicle 1.

[0037] The vehicle controller 2 (e.g., ECU: Electronic Control Unit) is configured to transmit a key-on signal to the battery management system 100 in response to a start button (not shown) provided on the electric vehicle 1 being switched to an on position by a user. The vehicle controller 2 is configured to transmit a key-off signal to the battery management system 100 in response to a start button being switched to an off position by a user. The charger 40 can communicate with the vehicle controller 2 to supply charging power (e.g., constant current, constant voltage, constant power) via the charging and discharging terminals P+, P- of the battery pack 10.

[0038] The battery pack 10 includes a group of batteries 11 , a relay 20 and a battery management system 100 .

[0039] The battery group 11 includes a plurality of batteries B1 to B N (N is a natural number of 2 or more) in series connection. That is, in the battery group 11, a plurality of batteries B1 to B N are connected in series to each other. N may include one unit cell or two or more unit cells connected in series, parallel, or series-parallel, which are manufactured to have the same electrochemical specifications. A unit cell is the smallest unit of a storage element that can be charged and discharged independently. For example, the type of unit cell is not particularly limited as long as it can be repeatedly charged and discharged, such as a lithium-ion cell.

[0040] In the following, multiple batteries B1 to B N When explaining the contents common to both, the letter "B" will be used to refer to the battery.

[0041] The relay 20 is electrically connected in series to the battery group 11 through a power path connecting the battery group 11 and the electric load 30. In FIG. 1, the relay 20 is shown connected between the positive terminal of the battery group 11 and a charge / discharge terminal P+. The relay 20 is controlled to be turned on and off in response to a switching signal from the battery management system 100 and / or the vehicle controller 2. The relay 20 may be a mechanical con- tect that is turned on and off by the magnetic force of a coil, or may be a semiconductor switch such as a metal oxide semiconductor field effect transistor (MOSFET).

[0042] The electric load 30 includes an inverter 31 and an electric motor 32. The inverter 31 is provided to convert a direct current from the batteries 11 included in the battery pack 10 into an alternating current in response to a command from the battery management system 100 or the vehicle controller 2. The electric motor 32 is driven using the AC power from the inverter 31. As the electric motor 32, for example, a three-phase AC motor may be used.

[0043] The state in which the relay 20 is turned on and the battery B is being charged or discharged can be called a load state (cycle state).

[0044] When the relay 20 is switched from on to off, the battery B is in a no-load state (rest state, calendar state), and the battery voltage of the battery B in the no-load state may be called the no-load voltage. The no-load voltage is a general term for the relaxation voltage and the open circuit voltage (OCV). Specifically, when the battery B is switched from a loaded state to a no-load state, the no-load voltage of the battery B changes as the polarization generated in the battery B is naturally eliminated. The OCV indicates the no-load voltage when the battery B is maintained in the no-load state for a predetermined time (e.g., 2 hours) or more and the voltage change rate of the battery B becomes less than a certain value. In other words, the OCV is the no-load voltage in a state in which the polarization of the battery B is negligibly small. The relaxation voltage indicates the no-load voltage while the polarization is naturally eliminated.

[0045] The battery management system 100 includes a battery monitor 110, a balancer 130, and a control circuit 140. The battery management system 100 may further include a communication circuit 150. In the following, the battery management system 100 may include the battery monitor 110, the control circuit 140, and the communication circuit 150.

[0046] The battery monitor 110 includes a voltage detection circuit 112. The battery monitor 110 may further include a current detector 114.

[0047] The voltage detection circuit 112 detects the voltage of the batteries B1 to B N and configured to detect the voltage applied across both ends of battery B (sometimes referred to as the battery voltage) and generate a voltage signal indicative of the detected battery voltage.

[0048] The current detector 114 is connected in series to the battery group 11 through a current path between the battery group 11 and the inverter 30. The current detector 114 may be implemented by one or a combination of two or more known current detection elements such as a shunt resistor, a Hall effect element, etc. N Since multiple batteries B1 to B are connected in series, N A common charge / discharge current flows through both.

[0049] 1 shows that a shunt resistor is used as the current detector 114. In this case, the voltage detection circuit 112 can output a current signal indicating the direction and magnitude of the charge / discharge current to the control circuit 140 based on the voltage applied across the shunt resistor. Of course, the current detector 114 can also directly generate a current signal indicating the charge / discharge current flowing through the battery group 11 and output it to the control circuit 140.

[0050] The balancer 130 balances the batteries B1 to B2 in response to a balancing command from the control circuit 140. N The balancing execution command is configured to execute a balancing process for a battery B that needs balancing among the batteries B1 to B2. Hereinafter, the battery B that is determined to need balancing is referred to as a "target battery." N may include a target time for the target battery B. The target time means the duration of the balancing process required for the target battery B.

[0051] In FIG. 1, as an example of the balancer 130, the balancer 130 includes a plurality of balancing circuits D1 to D N The present embodiment shows a case where the balancing circuits D1 to D N Multiple batteries B1~B N In the following, a plurality of balancing circuits D1 to D N When explaining the contents common to all of the above, the letter "D" will be added to the battery.

[0052] The balancing circuit D is a series circuit of a discharge resistor 131 and a discharge switch 132. The discharge switch 132 is turned on in response to a balancing execution command. While the discharge switch 132 is turned on, the battery B is discharged by the discharge resistor 131. The discharge switch 132 may be a semiconductor switch such as a MOSFET.

[0053] The control circuit 140 may be operatively coupled to the relay 20, the battery monitor 110, the balancer 130, and the communication circuit 150. The fact that two components are operatively coupled means that the two components are directly or indirectly connected to each other so that signals can be transmitted and received unidirectionally or bidirectionally.

[0054] The control circuit 140 may be referred to as a "battery controller" and may be implemented in hardware using at least one of an ASIC (application specific integrated circuit), a DSP (digital signal processor), a DSPD (digital signal processing device), a PLD (programmable logic device), an FPGA (field programmable gate array), a microprocessor, or other electrical unit for performing a function.

[0055] The control circuit 140 may collect a voltage signal and / or a current signal from the battery monitor 110. In one example, the control circuit 140 may convert the analog signal collected from the battery monitor 110 into a digital value and record it using an internal ADC (Analog to Digital Converter). Alternatively, the battery monitor 110 may transmit the result of converting the analog signal into a digital value by itself to the control circuit 140.

[0056] The memory 141 may include at least one type of storage medium, for example, a flash memory type, a hard disk type, a solid state disk type (SSD type), a silicon disk drive type (SDD type), a multimedia card micro type, a random access memory (RAM), a static random access memory (SRAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), and a programmable read-only memory (PROM). The memory unit 141 may store data and programs required for the arithmetic operation by the control circuit 140. The memory unit 141 may store data indicating the result of the arithmetic operation by the control circuit 140. The memory 141 may store predefined functions, logic, and algorithms to be used for detecting an internal short circuit fault in the battery B. The memory 141 may be integrated in the control unit 140.

[0057] The control circuit 140 can turn on the relay 20 in response to a key-on signal from the vehicle controller 2. The control circuit 140 can turn off the relay 20 in response to a key-off signal from the vehicle controller 2. The key-on signal is a signal requesting switching from an unloaded state to a loaded state. The key-off signal is a signal requesting switching from a loaded state to an unloaded state. Alternatively, the on / off control of the relay 20 can be handled by the vehicle controller 2 instead of the control circuit 140.

[0058] The control circuit 140 is configured to control the balancer 130 based on the voltage of the battery B detected by the battery monitor 110 .

[0059] The control circuit 140 controls a plurality of batteries B1 to B N By monitoring the voltage of each of the batteries B1 to B N The maximum voltage and the minimum voltage of the batteries B1 to B2 can be identified. N The minimum voltage is the maximum voltage of the batteries B1 to B N This refers to the smallest voltage among the above.

[0060] The communication circuit 150 is configured to support wired or wireless communication between the control circuit 140 and the vehicle controller 2. The wired communication may be, for example, CAN (controller area network) communication, and the wireless communication may be, for example, ZigBee (registered trademark) or Bluetooth (registered trademark) communication. Of course, the type of communication protocol is not particularly limited as long as it supports wired or wireless communication between the control circuit 140 and the vehicle controller 2. The communication circuit 150 may include an output device (for example, a display, a speaker) that provides information received from the control circuit 140 and / or the vehicle controller 2 in a form that can be recognized by a user (driver).

[0061] The operation of the control circuit 140 to detect an internal short circuit fault in a battery will now be described in detail.

[0062] The control circuit 140 determines the voltage value of the no-load voltage of the battery B.

[0063] The control circuit 140 may determine the voltage value of the no-load voltage of battery B to be the same as the voltage value of the voltage of battery B detected by the battery monitor 110 when battery B is in an unloaded state.

[0064] When battery B is in a loaded state, the control circuit 140 may use a battery state estimation algorithm to determine (estimate) a voltage value of the no-load voltage of battery B based on the battery voltage of battery B detected by the battery monitor 110 and the charge / discharge current of battery B detected by the current detector 114. In one example, the no-load voltage of battery B may be estimated by subtracting a voltage corresponding to the product of the charge / discharge current of battery B and the internal resistance of battery B from the battery voltage of battery B detected by the battery monitor 110 according to Ohm's law.

[0065] Alternatively, the control circuit 140 may determine an estimated value of the state of charge (SOC) of battery B using a predetermined battery state estimation algorithm, regardless of whether battery B is in an unloaded state or a loaded state, and then obtain an OCV value related to the estimated value of the SOC of battery B from a predefined SOC-OCV map (see FIG. 5). As the battery state estimation algorithm, a known algorithm (e.g., a Kalman filter, etc.) may be adopted.

[0066] The control circuit 140 controls a plurality of batteries B1 to B N When the battery group 11 is switched from a loaded state to an unloaded state, the control circuit 140 selects a target battery B from among the batteries B1 to B N It may be determined whether or not a balancing process is required for at least one battery B among the batteries 11. The determination of the presence or absence of the target battery B may be performed when the battery group 11 is switched from a loaded state to an unloaded state, i.e., from the start of the unloaded state and periodically while the unloaded state continues.

[0067] In one example, the control circuit 140 controls a plurality of batteries B1 to B N In another example, the control circuit 140 may set the battery B having the estimated SOC of the plurality of batteries B1 to B2 having the minimum no-load voltage higher than the reference value by the reference value or more as the target battery. NBattery B, which has a minimum SOC higher than the reference value, may be set as the target battery.

[0068] The control circuit 140 controls the target battery (e.g., B i ) and a reference battery (e.g., B j The target capacity of the target battery B may be determined based on the capacity corresponding to the voltage difference (or SOC difference) between the reference battery and the target battery B. N The control circuit 140 may determine the target time for the target battery B by using a map given in advance as a correlation between the target capacity and the target time. The correlation between the target capacity and the target time may be determined by an experiment for a battery manufactured to have the same electrochemical performance as battery B.

[0069] Alternatively, the balancer 130 may perform the balancing process on the target battery B for a first time period and then stop the balancing process for a second time period each time a balancing execution command is received. The control circuit 140 may control the balancing process of the plurality of batteries B1 to B2 for each period during which the balancing process of the balancer 130 is stopped. N The target battery B may be further identified from among the battery B and a balancing execution command for the target battery B may be transmitted to the balancer 130.

[0070] The balancing command may be a high level voltage applied directly to the discharge switch 132 to induce the discharge switch 132 from an OFF state to an ON state. The discharge switch 132 may be maintained in an OFF state while a balancing command is not received.

[0071] Meanwhile, when a switch from an unloaded state to a loaded state is requested while the balancing process for the target battery B is being performed, the control circuit 140 may output a balancing stop command from the balancer 130. In response to the balancing stop command, the balancer 130 may NThe overall balancing process may then be completed.

[0072] FIG. 2 is a reference diagram for explaining an exemplary equivalent circuit of a battery. In this specification, a normal battery is a battery B1 to B N The defective battery refers to the battery that has no internal short circuit failure. N This refers to batteries that have an internal short circuit.

[0073] Referring to FIG. 2, a normal battery is connected to a DC voltage source V DC , and an RC pair R1, C. In contrast, the faulty battery can be equivalent to a series circuit with an additional resistor R ISC can be equivalent to the additional resistor R ISC is the leakage current I ISC For reference, the DC voltage source V DC The voltage of is the OCV of battery B, and the battery voltage is the DC voltage source V DC , the internal resistance component R0 and the total voltage of the series circuit of the RC pair R1, C. When the voltage of the RC pair R1, C is zero (0V), the relaxation voltage and OCV are the same.

[0074] When charging a faulty battery, a portion of the charging power remains unstored in the faulty battery and flows as a leakage current I ISC In addition, when the faulty battery is discharged, a part of the discharged power is not supplied to the electric load 30 and becomes a leakage current I ISC Resistance R ISC The decrease in the resistance value of means that the internal short circuit fault becomes severe, and the more severe the internal short circuit fault becomes, the greater the leakage current I ISC As a result, the amount of power consumed may increase.

[0075] As a result, the voltage change (i.e., the increase in SOC) of the faulty battery is smaller than that of the normal battery during charging. On the other hand, the voltage change (i.e., the decrease in SOC) of the faulty battery is larger than that of the normal battery during discharging. Furthermore, even in a no-load state, the energy stored in the faulty battery is leaked through the leakage current I ISC It will be wasted as.

[0076] 3 to 6 are reference diagrams for explaining the principle of detecting an internal short circuit fault in a battery.

[0077] FIG. 3 shows the battery B over a period of time in which the battery group 11 is sequentially subjected to a loaded (charging), unloaded, loaded (discharging) and unloaded conditions. i and Battery B j The no-load voltage of each of the batteries is shown in Fig. 3. i is a normal battery, and battery B j It is assumed that this is a faulty battery.

[0078] Referring to FIG. 3, curve 310 represents the i The no-load voltage of battery B is shown in curve 320. j The time point tB indicates the no-load voltage of the batteries B1 to B2. N The time tA is the time when a faulty battery is detected. REF The reference time Δt is the time in the past. REF The length of time can be predetermined. To facilitate understanding, at time tA, the battery B i and Battery B j It is assumed that the no-load voltages of the two are the same.

[0079] The period from time tA to time t1 is the charging period, and battery B i and Battery B j The no-load voltage of battery B continues to rise. j Battery B iThe no-load voltage rises slower than battery B during the charging period tA to t1. i and Battery B j That is, during the charging period tA to t1, the voltage difference between the batteries B1 to B N The voltage imbalance condition becomes increasingly severe.

[0080] The period from time t1 to time t4 is a no-load period, and battery B i and Battery B j Charging and discharging of battery B is interrupted. j The no-load voltage of battery B gradually drops during the no-load period t1 to t4 due to leakage current (see FIG. 2). On the other hand, from time t2 to time t3, i The period during which the balancing process for battery B is performed. i The control circuit 140 performs balancing on the multiple batteries B1 to B2 between time t1 and time t2. N Of these, battery B i For example, at time t1, battery B j The no-load voltage of multiple batteries B1~B N If the minimum no-load voltage of battery B is i The no-load voltage of battery B j Since the no-load voltage of battery B is higher than that of battery B, i Of course, at least one battery having a no-load voltage lower than the minimum no-load voltage among the remaining batteries may be further set as the target battery. i By balancing the battery B i The no-load voltage of the batteries B1 to B2 continues to decrease during the balancing period t2 to t3. N The voltage imbalance condition is gradually eliminated.

[0081] The period from time t4 to time t5 is the discharging period, and battery B i and Battery B jThe no-load voltage of battery B continues to decrease. j Battery B i The no-load voltage drops faster than battery B during the discharge period t4 to t5. i and Battery B j That is, during the discharge period t4 to t5, the voltage difference between the batteries B1 to B N The voltage imbalance condition becomes increasingly severe.

[0082] The period from time t5 to time tB is a no-load period. j The no-load voltage of battery B gradually drops during the no-load period t5 to tB. On the other hand, from time t6 to time t7, i The control circuit 140 performs balancing on the multiple batteries B1 to B2 between time t5 and time t6. N In one example, at time t6, similarly to time t2, the target battery is set to B. i is set as the target battery. Battery B i By balancing the battery B i The no-load voltage of the batteries B1 to B2 continues to decrease during the balancing period t6 to t7. N The voltage imbalance condition is further reduced.

[0083] According to the description above with reference to FIG. i Each time a balancing process is performed on battery B, i and Battery B j As a result, the difference in the no-load voltage between the multiple batteries B1 to B2 at time tB (the timing of detecting the internal short circuit fault) decreases. N Simply comparing the no-load voltage of battery B to a certain critical value j However, there is a problem in that it is not possible to distinguish whether a battery is faulty or not.

[0084] In the present invention, the most recent reference time Δt is calculated based on the detection timing (time tB) of the internal short circuit fault.REF A plurality of batteries B1 to B in a period (i.e., tA to tB) N Using the balancing capacity of each of the batteries B1 to B2 at the detection timing (time tB), N The compensated voltage value of battery B indicates an estimated value of the no-load voltage of battery B at the detection timing (time tB) in the case where no balancing process is performed on battery B over the period tA to tB. As a result, N Even if the voltage imbalance between battery B is very weak, j may be detected as a faulty battery.

[0085] The control circuit 140 detects the charge of the batteries B1 to B2 at each detection timing at a predetermined time interval. N In one example, a faulty battery can be detected by the reference time Δt REF may be 100 times the time interval between two adjacent detection timings, and the most recent reference time Δt REF The period can be specified by using a moving window. The control circuit 140 can detect an internal short circuit failure when a detection execution condition is satisfied. The detection execution condition is, for example, N There may be a no-load condition where the balancing process is stopped for all.

[0086] The balancing capacity of battery B during the period tA to tB is the cumulative value of the discharge capacity of battery B due to the balancing process performed during the period tA to tB, that is, the total discharge capacity during the period tA to tB. j ) balancing capacity is determined to be 0 Ah.

[0087] The principle of determining the discharge capacity each time the balancing process is performed will be described below.

[0088] Figure 4 shows the load of battery B during the no-load period t1 to t4 in Figure 3. iCurve 410 and curve 411 are diagrams for explaining the balancing process performed on battery B. i The no-load voltage and discharge capacity of Battery B change over time. i The voltage value of the no-load voltage of battery B is constant as V2 from time t1 to time t2, and continues to decrease from time t2 to time t3, reaching V3 at time t3. i This is the point at which the balancing process for is completed.

[0089] The control circuit 150 applies a capacity estimation function to the first balancing data of the balancing process to estimate the capacity of the battery B i The first balancing data includes a starting voltage value and a duration of the balancing process. The starting voltage value is a discharge capacity of battery B at a starting time t2 of the balancing process. i The no-load voltage of the load t1 is V2 in FIG. 4. The duration is the time interval from the start time t2 to the end time t3 of the balancing process, and is Δt BC =t3-t2.

[0090] The capacity estimation function specifies the correlation between the starting voltage value, duration, and discharge capacity, and can be determined by experiments on a battery manufactured to have the same electrochemical performance as battery B. The following equation 1 is an example of the capacity estimation function.

[0091]

number

[0092] In the formula 1, V start is the starting voltage value, Δt BC is the duration, R is the predetermined resistance of the discharge resistor 131, and Q dis is the discharge capacity per balancing process. V start / R denotes the balancing current that flows through the discharge resistor 131 at the start of the balancing process.

[0093] Equation 2 below is another example of a capacity estimation function.

number

[0094] In the formula 2, V end is the end voltage value, and the remaining factors are the same as in equation (1).

[0095] Alternatively, the control circuit 150 applies the SOC-OCV map to the second balancing data of the balancing process to obtain the SOC-OCV of the battery B i The second balancing data includes a start voltage value and an end voltage value of the balancing process. The end voltage value indicates the no-load voltage at the end time t3 of the balancing process, which is V3 in FIG. 4. FIG. 5 is an example of an SOC-OCV map. Referring to FIG. 5, Z2 is the SOC corresponding to the start voltage value V2, and Z3 is the SOC corresponding to the end voltage value V3. The control circuit 140 calculates the discharge capacity of the battery B by the difference between the two SOCs, i.e., Z2-Z3. i The full charge capacity (FCC) of battery B is multiplied by the full charge capacity (FCC) of battery B during the balancing process performed during the balancing period t2 to t3. i The discharge capacity of the battery can be determined. The method for estimating the full charge capacity is well known, so a detailed description thereof will be omitted.

[0096] Alternatively, the balancing capacity of battery B can be directly calculated by accumulating the balancing current, which is calculated periodically by applying Ohm's law to the voltage and resistance value of discharge resistor 131 from the start to the end of the balancing process.

[0097] The above-mentioned determination of the balancing capacity can be performed each time the balancing process is performed.

[0098] During the period tA to tB, battery B iThe balancing process for battery B was performed twice. As a result, the control circuit 140 calculates the total discharge capacity of battery B during the period tA to tB by combining the discharge capacity during the balancing period t2 to t3 and the discharge capacity during the balancing period t6 to t7. i The total capacity consumed from battery B i The balancing capacity of the spool may be determined.

[0099] 5, the control circuit 140 detects the charge of the batteries B1 to B2 at the detection timing (time tB). N An estimate of the SOC of each battery may be determined. i The no-load voltage is V i If so, the control circuit 140 sets the voltage value V i Apply the SOC-OCV map to the voltage value V i Z corresponds to i Battery B i can be determined as an estimate of the SOC.

[0100] The control circuit 140 calculates the most recent reference time Δt REF Multiple batteries between B1 and B N A predetermined voltage compensation logic, which will be described later, is applied to each balancing capacity of the plurality of batteries B1 to B N Specifically, the control circuit 140 can compensate the voltage value of the no-load voltage of each of the batteries B i Balancing capacity of battery B i Divide it into the full charge capacity of battery B i SOC change amount ΔZ i The control circuit 140 may determine the estimated SOC Z i SOC change amount ΔZ i Battery B i The estimated SOC of Z i From Z i+ The control circuit 140 calculates the compensated SOC estimate Z i+ Apply the SOC-OCV map to Z i+ The voltage value V i+ Determine the voltage value V i+Battery B i Using the balancing capacitance of i On the other hand, battery B j For battery B, no balancing process has been performed during the period tA to tB. j The compensated voltage value V j+ is the voltage value V detected at time tB j is equivalent to.

[0101] With further reference to FIG. 3 , curve 311 corresponds to curve 310 plus battery B i That is, curve 311 is the result of compensating curve 310 by applying the change in the balancing capacity of battery B during the period tA to tB. i When no balancing process is performed on battery B, i 5 shows the change over time in the no-load voltage of battery B at detection timing tB. During the charging period tA to t1, no balancing process is performed, so curves 310 and 320 are completely overlapped during the charging period tA to t1. Furthermore, during the discharging period t4 to t5, no balancing process is performed, so the difference between curves 310 and 320 remains the same throughout the discharging period t4 to t5. As explained in FIG. 5, the no-load voltage of battery B at detection timing tB is i The voltage value is V i From V i+ By compensating for battery B j Voltage value V j It can be seen that the difference between

[0102] The above-mentioned series of processes (voltage compensation logic) is performed for each detection timing of multiple batteries B1 to B N The control circuit 140 controls the multiple batteries B1 to B N The reference voltage value may be determined to be equal to the average or median of the compensated voltage values ​​of two or more batteries among the batteries B1 to B2. That is, the reference voltage value may be updated every detection timing. NThe compensation voltage may be determined based on (i) all of the plurality of compensated voltage values ​​or (ii) an average or median of a predetermined number of the plurality of compensated voltage values ​​in descending order. R is a reference voltage value at time tB. Or, the reference voltage value is N may be a pre-given value regardless of voltage changes.

[0103] The control circuit 140 may determine a voltage difference, which is the difference between the reference voltage value and the compensated voltage value of the battery B, for each detection timing. The control circuit 140 may also determine a voltage difference, which is the difference between the reference voltage value and the compensated voltage value of the battery B, for each detection timing. REF A time series showing the change over time of the voltage difference of battery B determined sequentially multiple times over a period tA to tB may be recorded in memory 141. If the voltage difference of battery B at some detection timings within the period tA to tB is missing, the missing voltage difference value may be added to the time series by applying interpolation to the remaining voltage difference values ​​in the time series. In FIG. 6, curves 610 and 620 are respectively the voltage difference of battery B. i Voltage difference between battery B and battery B j The graph shows the change in voltage difference over time.

[0104] The control circuit 140 calculates the most recent reference time Δt REF The amount of change in the voltage difference of battery B between ΔV iA and ΔV iB are the currents of battery B at time tA and tB, respectively. i is the voltage difference between battery B and battery C. i The change in voltage difference is ΔV iA -ΔV iB Also, ΔV jA and ΔV jB are the currents of battery B at time tA and tB, respectively. j is the voltage difference between battery B and battery C. j The change in voltage difference is ΔV jA -ΔV jB Incidentally, referring to FIG. 3, ΔV iB =V i+ -V R and ΔV jB =Vj+ -V R It is.

[0105] The control circuit 140 compares the change in the voltage difference of the battery B with a critical value at each detection timing to determine whether the battery B has an internal short circuit failure. iA -ΔV iB < Critical value ≦ ΔV jA -ΔV jB If so, battery B i is judged as a normal battery, and battery B j is determined to be a faulty battery.

[0106] The control circuit 140 compares the amount of change in the voltage difference of battery B with a critical value at each detection timing, counts the number of consecutive times that the amount of change in the voltage difference of battery B is equal to or greater than the critical value, and when the counted number reaches a predetermined number, it can determine that battery B has an internal short circuit fault.

[0107] 7 and 8 are flowcharts showing a battery management method according to a first embodiment of the present invention. The method of FIG. 7 may be repeatedly performed at predetermined time intervals. For ease of understanding, the method of FIG. 7 will be described assuming that it is performed at time tB.

[0108] 1 to 7, in step S700, the control circuit 140 determines a first voltage value indicating the no-load voltage of the battery B. For example, V i and V j are battery B i and Battery B j 1 shows a first voltage value.

[0109] In step S710, the control circuit 140 compensates for the first voltage value of the battery B using the balancing capacity of the battery B. Step S710 may include steps S810, S820, S830, and S840 shown in FIG. 8 as a subroutine.

[0110] In step S810, the control circuit 140 applies the SOC-OCV map to the first voltage value of the battery B to determine an estimate of the SOC of the battery B. Referring to FIG. i Battery B i The first voltage value V i Compatible battery B i This is an estimate of the SOC.

[0111] In step S820, the control circuit 140 determines the balancing capacity of the battery B. The balancing capacity of the battery B is calculated based on the most recent reference time Δt REF It may be an accumulated value of the discharge capacity due to the balancing process performed on battery B during the period.

[0112] In step S830, the control circuit 140 compensates the estimated value of the SOC of the battery B by adjusting the SOC change amount corresponding to the balancing capacity to the estimated value of the SOC of the battery B. Referring to FIG. i to ΔZ i is added, and battery B i The compensated SOC estimate Z i+ is obtained.

[0113] In step S840, the control circuit 140 applies the SOC-OCV map to the compensated SOC estimate of Battery B to determine a compensated first voltage value of Battery B. Referring to FIG. 5, the compensated first voltage value of Battery B is Z i+ V corresponding to i+ is determined identically.

[0114] In step S720, the control circuit 140 determines a reference voltage value. R is the reference voltage value at time tB.

[0115] In step S730, the control circuit 140 determines a voltage difference of the battery B to be equal to the difference between the compensated first voltage value of the battery B and the reference voltage value. Referring to FIG. 6, ΔV iB and ΔV jB are battery B i Voltage difference between battery B and battery Bj is the voltage difference.

[0116] In step S740, the control circuit 140 calculates the most recent reference time Δt REF Determine the change in the voltage difference of battery B between ΔV iA -ΔV iB Battery B i is the change in the voltage difference, ΔV jA -ΔV jB Battery B j is the change in the voltage difference.

[0117] In step S750, the control circuit 140 determines whether the change in the voltage difference of the battery B is equal to or greater than a critical value. If the value of step S750 is 'YES', the control circuit 140 proceeds to step S760.

[0118] In step S760, the control circuit 140 detects the battery B as having an internal short circuit fault. Furthermore, the control circuit 140 may perform a predetermined protective action. The protective action may be outputting a diagnostic message indicating that the battery B has an internal short circuit fault. The diagnostic message may be transmitted to the vehicle controller 2 by the communication circuit 150. When the communication circuit 150 receives the diagnostic message, it may output a warning signal to a user.

[0119] 9 is a flowchart showing a battery management method according to a second embodiment of the present invention. The method of FIG. 9 may be repeatedly performed at a predetermined time interval. For ease of understanding, the method of FIG. 9 will be described assuming that it is performed at time tB.

[0120] 9, the process from step S700 to step S740 is the same as in the first embodiment. After step S740 is performed, the process proceeds to step S910. In step S910, the control circuit 140 determines whether the amount of change in the voltage difference of battery B is equal to or greater than a critical value. If the value of step S910 is "yes", the process proceeds to step S920. If the value of step S910 is "no", the process proceeds to step S922.

[0121] In step S920, the control circuit 140 increments the failure count of battery B by 1. In step S922, the control circuit 140 resets the failure count of battery B to an initial value (eg, 0).

[0122] In step S930, the control circuit 140 determines whether the failure count of battery B is equal to or greater than a predetermined value. That is, it determines whether the change in the voltage difference of battery B is equal to or greater than a critical value and has been counted a predetermined number of times in succession. If the value of step S930 is 'YES', the process proceeds to step S940.

[0123] In step S940, the control circuit 140 detects an internal short-circuit fault in the battery B. As in the first embodiment, the control circuit 140 can perform a predetermined protective operation.

[0124] The second embodiment is a modification of the first embodiment, which can prevent detection of a faulty battery.

[0125] The embodiments of the present invention described above may not necessarily be embodied through an apparatus and method, but may be embodied through a program that realizes functions corresponding to the configuration of the embodiments of the present invention or a recording medium on which the program is recorded, and such implementation should be easily embodied by a person skilled in the art to which the present invention pertains from the description of the above-mentioned embodiments.

[0126] Although the present invention has been described above with reference to limited embodiments and drawings, it goes without saying that the present invention is not limited thereto, and various modifications and variations can be made by those having ordinary skill in the art to which the present invention pertains within the scope of the technical spirit of the present invention and the scope of the claims.

[0127] Furthermore, since the above-mentioned invention can be variously replaced, modified, and altered by a person having ordinary knowledge in the technical field to which the invention belongs without departing from the technical concept of the invention, it is not limited to the above-mentioned embodiments and the attached drawings, and can be configured by selectively combining all or part of each embodiment to make various modifications. [Item 1] a battery monitor for detecting the voltage of each of the plurality of batteries connected in series; A balancer that performs balancing for each battery; a control circuit that controls the balancer based on the voltage of each battery detected by the battery monitor; The control circuit includes: determining a first voltage value indicative of a no-load voltage of each of the batteries; Compensating the first voltage value of each of the batteries using a balancing capacity of each of the batteries according to the balancing process performed during a recent reference time; determining a voltage difference between the compensated first voltage value and a reference voltage value for each of the batteries; a battery management system that detects an internal short circuit fault in each of the batteries by comparing a change in the voltage difference of each of the batteries during the reference time with a critical value. [Item 2] The control circuit includes: if the change in the voltage difference of each of the batteries is equal to or greater than the critical value, incrementing a failure count of each of the batteries by one; 2. The battery management system of item 1, wherein if a fault count of each battery is equal to or greater than a predetermined value, the battery management system detects each battery as having an internal short circuit fault. [Item 3] The control circuit includes: 2. The battery management system of claim 1, further comprising: determining the reference voltage value to be equal to an average or median of the compensated first voltage values ​​of at least two or more batteries among the plurality of batteries. [Item 4] the balancer includes a plurality of balancing circuits connected in parallel to the plurality of batteries in a one-to-one relationship; 2. The battery management system of claim 1, wherein each balancing circuit includes a discharge resistor and a discharge switch connected in series. [Item 5] The control circuit includes: 2. The battery management system according to item 1, further comprising: accumulating a discharge capacity of each battery cell by each balancing process performed within the reference time period to determine the balancing capacity of each battery cell. [Item 6] The control circuit includes: applying a capacity estimation function to first balancing data associated with each balancing process to determine the discharge capacity of each of the batteries for each balancing process; 6. The battery management system of claim 5, wherein the first balancing data includes a second voltage value indicative of a no-load voltage of each of the batteries at the start of the balancing process and a duration of the balancing process. [Item 7] The control circuit includes: applying a SOC-OCV map to the second balancing data for each balancing process to determine the discharge capacity for each battery for each balancing process; 6. The battery management system of claim 5, wherein the second balancing data includes a second voltage value indicating a no-load voltage of each of the batteries at a start of the balancing process and a third voltage value indicating a no-load voltage of each of the batteries at an end of the balancing process. [Item 8] The control circuit includes: applying a SOC-OCV map to the first voltage values ​​for each of the batteries to determine an estimate of a SOC for each of the batteries; Compensating the estimated SOC of each of the batteries by adjusting the SOC change amount corresponding to the balancing capacity to the estimated SOC of each of the batteries; 2. The battery management system of claim 1, further comprising: applying the SOC-OCV map to the compensated SOC estimate for each battery to determine the compensated first voltage value. [Item 9] 9. A battery pack comprising the battery management system according to any one of items 1 to 8. [Item 10] 10. An electric vehicle comprising the battery pack according to item 9. [Item 11] determining a first voltage value indicative of a no-load voltage of each of the plurality of series connected batteries; compensating the first voltage value of each battery using a balancing capacity of each battery according to a balancing process performed during a recent reference time; determining a voltage difference between the compensated first voltage value and a reference voltage value for each of the batteries; and comparing a change in the voltage difference of each of the batteries during the reference time with a critical value to detect an internal short circuit fault of each of the batteries. [Item 12] The step of detecting an internal short circuit fault of each battery comprises: incrementing a failure count of each of the batteries by 1 if the change in the voltage difference of each of the batteries is equal to or greater than the critical value; 12. The battery management method according to claim 11, further comprising: detecting each battery as having an internal short circuit fault if the fault count of each battery is equal to or greater than a predetermined value. [Item 13] 13. The battery management method according to claim 11 or 12, further comprising determining the reference voltage value to be equal to an average or median of the compensated first voltage values ​​of at least two or more batteries among the plurality of batteries. [Item 14] The step of compensating the first voltage value of each battery includes: applying a SOC-OCV map to the first voltage values ​​for each battery to determine an estimate of SOC for each battery; compensating the estimated SOC of each battery by adding an SOC change amount corresponding to the balancing capacity to the estimated SOC of each battery; and applying the SOC-OCV map to the compensated SOC estimate for each battery to determine the compensated first voltage value.

Claims

1. a battery monitor that acquires the voltage of each of the plurality of batteries; In a state where a balancing process has not been performed on the plurality of batteries, a no-load voltage value of each of the batteries is compensated for using a balancing capacity of each of the batteries obtained by a balancing process performed in the past; determining a voltage difference between the compensated no-load voltage value and a reference voltage value for each battery; a processor that detects whether or not there is an abnormality in each of the batteries based on an amount of change in the voltage difference of each of the batteries.

2. The processor, if the change in the voltage difference of each battery is equal to or greater than a critical value, increasing a failure count of each battery by one; The battery management system according to claim 1 , wherein when the fault count of each battery is equal to or greater than a predetermined value, each battery is detected as having an internal short circuit fault.

3. The reference voltage value is The battery management system of claim 1 , wherein the compensated no-load voltage value is an average or median value of the compensated no-load voltage values ​​of at least two or more batteries of the plurality of batteries.

4. The processor, Compensating the no-load voltage value using a balancing capacitance obtained by a balancing process performed during a reference time; The reference time is The battery management system of claim 1 , wherein the time to perform the balancing process is longer than the time to perform the balancing process.

5. The processor, 2. The battery management system according to claim 1, further comprising: accumulating a discharge capacity of each of the batteries due to each balancing process performed within a reference time period to determine the balancing capacity of each of the batteries.

6. The processor, applying a capacity estimation function to first balancing data associated with each balancing process to determine the discharge capacity of each of the batteries associated with each balancing process; The battery management system of claim 5 , wherein the first balancing data includes a no-load voltage value of each of the batteries at the start of the balancing process and a duration of the balancing process.

7. The processor, applying an SOC-OCV map to the second balancing data for each balancing process to determine the discharge capacity of each battery for each balancing process; The battery management system of claim 5 , wherein the second balancing data includes a no-load voltage value for each of the batteries at a start of the balancing process and a no-load voltage value for each of the batteries at an end of the balancing process.

8. The processor, applying an SOC-OCV map to the no-load voltage value of each of the batteries to determine an estimate of SOC for each of the batteries; Compensating the estimated value of SOC of each of the batteries by adjusting an amount of SOC change corresponding to the balancing capacity to the estimated value of SOC of each of the batteries; The battery management system of claim 1 , further comprising: applying the SOC-OCV map to the compensated SOC estimate of each battery to determine the compensated no-load voltage value.

9. A battery pack comprising a battery management system according to any one of claims 1 to 8.

10. 10. An electric vehicle comprising the battery pack of claim 9.

11. obtaining a no-load voltage value for each of a plurality of batteries; compensating the no-load voltage value of each of the batteries using a balancing capacity of each of the batteries obtained by a previous balancing process when a balancing process has not been performed on the plurality of batteries; determining a voltage difference between the compensated no-load voltage value and a reference voltage value for each battery; detecting whether or not each of the batteries is abnormal based on an amount of change in the voltage difference of each of the batteries.

12. The step of detecting whether or not each battery has an abnormality comprises: if the change in the voltage difference of each of the batteries is equal to or greater than a critical value, increasing a failure count of each of the batteries by one; 12. The battery management method of claim 11, further comprising: detecting each of the batteries as having an internal short circuit fault if the fault count of each of the batteries is equal to or greater than a predetermined value.

13. The reference voltage value is The battery management method according to claim 11 or 12, wherein the compensated no-load voltage values ​​of at least two or more batteries among the plurality of batteries are an average value or a median value.

14. The step of compensating the no-load voltage value of each of the batteries includes: applying a SOC-OCV map to the no-load voltage value of each of the batteries to determine an estimated SOC for each of the batteries; compensating the estimated value of SOC of each of the batteries by adding an SOC change amount corresponding to the balancing capacity to the estimated value of SOC of each of the batteries; and applying the SOC-OCV map to the compensated SOC estimate for each battery to determine the compensated no-load voltage value.

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