Battery Management System, Battery Pack, Electric Vehicle, and Battery Management Method

Abstract

A battery management system includes a battery monitor, a balancer and a control circuit to control the balancer. The control circuit determines a first voltage value indicating a no-load voltage of each battery, compensates the first voltage value of each battery using a balancing capacity of each battery by a balancing operation for a latest reference time, determines a voltage deviation or a difference between the compensated first voltage value of each battery and a reference voltage value, and detects an internal short circuit fault in each battery by comparing a change amount of the voltage deviation of each battery for the reference time with a threshold.

Claims

1. A battery management system, comprising: a battery monitor configured to detect a voltage of each of a plurality of batteries connected in series; a balancer configured to perform a balancing operation for each battery; and a control circuit configured to: control the balancer based on the voltage of each battery detected by the battery monitor, and for each battery of the plurality of batteries: determine a first voltage value indicating a no-load voltage of the battery, compensate the first voltage value of the battery using a balancing capacity of the battery by the balancing operation for performed at a latest reference time, determine a voltage difference between the compensated first voltage value of each the battery and a reference voltage value, and detect an internal short circuit fault in the battery based on a comparison of a magnitude of the voltage difference of the battery with a threshold.

2. The battery management system according to claim 1, wherein the control circuit is configured to, for each battery: increase a fault count of the battery by 1 in response to the magnitude of the voltage difference of the battery being equal to or larger than the threshold, detect the internal short circuit fault in the battery in response to the fault count of the battery being equal to or larger than a predetermined value.

3. The battery management system according to claim 1, wherein the reference voltage value is equal to an average or median of the compensated first voltage values of at least two of the plurality of batteries.

4. The battery management system according to claim 1, wherein the balancer includes a plurality of balancing circuits connected in parallel to the plurality of batteries in a one-to-one correspondence relationship, and wherein each balancing circuit includes a discharge resistor and a discharge switch connected in series.

5. The battery management system according to claim 1, wherein the control circuit is configured to determine, for each battery, the balancing capacity of the battery by accumulating a discharge capacity of the battery for each balancing operation within a predetermined period of time preceding the latest reference time.

6. The battery management system according to claim 5, wherein the control circuit is configured to determine the discharge capacity of the battery for a given balancing operation by applying a capacity estimation function to first balancing data associated with the given balancing operation, and wherein the first balancing data includes a second voltage value indicating the no-load voltage of the battery at a start of the given balancing operation and a duration of the given balancing operation.

7. The battery management system according to claim 5, wherein the control circuit is configured to determine the discharge capacity of the battery for a given balancing operation by applying a state of charge (SOC)-open circuit voltage (OCV) mapping to second balancing data of the given balancing operation, and wherein the second balancing data includes a second voltage value indicating the no-load voltage of the battery at a start of the given balancing operation and a third voltage value indicating the no-load voltage of the battery at an end of the given balancing operation.

8. The battery management system according to claim 1, wherein the control circuit is configured to, for each battery of the plurality of batteries: determine an estimated SOC of the battery by applying a SOC-OCV mapping to the first voltage value of the battery, compensate the estimated SOC of the battery by adding a SOC change amount to the estimated SOC of the battery, wherein the SOC change amount corresponds to the balancing capacity of the battery, and determine the compensated first voltage value by applying the SOC-OCV mapping to the compensated estimated SOC of the battery.

9. A battery pack comprising the battery management system according to claim 1.

10. An electric vehicle comprising the battery pack according to claim 9.

11. A battery management method, comprising: determining, by a control circuit, a first voltage value indicating a no-load voltage of a battery included among a plurality of batteries connected in series; compensating, by the control circuit, the first voltage value of the battery using a balancing capacity of the battery at a balancing operation for the plurality of batteries performed at a latest reference time; determining, by the control circuit, a voltage difference between the compensated first voltage value of the battery and a reference voltage value; and detecting, by the control circuit, an internal short circuit fault in the battery based on a comparison of a magnitude of the voltage difference of the battery with a threshold.

12. The battery management method according to claim 11, wherein detecting the internal short circuit fault in the battery comprises: increasing, by the control circuit, a fault count of the battery by 1 in response to the magnitude of the voltage difference of the battery being equal to or larger than the threshold; and detecting, by the control circuit, the internal short circuit fault in the battery in response to the fault count of the battery being equal to or larger than a predetermined value.

13. The battery management method according to claim 11, wherein the reference voltage value is an average or median of the compensated first voltage values of at least two of the plurality of batteries.

14. The battery management method according to claim 11, wherein compensating the first voltage value of the battery comprises: determining, by the control circuit, an estimated state of charge (SOC) of the battery by applying a SOC-open circuit voltage (OCV) mapping to the first voltage value of the battery; compensating, by the control circuit, the estimated SOC of the battery by adding a SOC change amount to the estimated SOC of the battery wherein the SOC change amount corresponds to the balancing capacity of the battery; and determining, by the control circuit, the compensated first voltage value by applying the SOC-OCV mapping to the compensated estimated SOC of the battery.

15. The battery management method according to claim 11, further comprising, for each battery of the plurality of batteries, determining a respective first voltage value, compensating the respective first voltage value of the battery, determining a respective voltage difference using the respective first voltage value, and detecting an internal short circuit fault based on a magnitude of the respective voltage difference.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings illustrate an exemplary embodiment of the present disclosure, and together with the detailed description of the present disclosure as described below, serve to provide a further understanding of the technical aspects of the present disclosure, and thus the present disclosure should not be construed as being limited to the drawings.

[0030] FIG. 1 is a diagram exemplarily showing an electric vehicle according to the present disclosure.

[0031] FIG. 2 is a diagram for reference in describing an exemplary equalization circuit of a battery.

[0032] FIGS. 3 to 6 are diagrams for reference in describing the principle of internal short circuit fault detection in a battery.

[0033] FIGS. 7 and 8 are flowcharts exemplarily showing a battery management method according to a first embodiment of the present disclosure.

[0034] FIG. 9 is a flowchart exemplarily showing a battery management method according to a second embodiment of the present disclosure.

DETAILED DESCRIPTION

[0035] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Prior to the description, it should be understood that the terms or words used in the specification and the appended claims should not be construed as being limited to general and dictionary meanings, but rather interpreted based on the meanings and concepts corresponding to the technical aspects of the present disclosure on the basis of the principle that the inventor is allowed to define the terms appropriately for the best explanation.

[0036] Therefore, the embodiments described herein and the illustrations shown in the drawings are just an exemplary embodiment of the present disclosure, but not intended to fully describe the technical aspects of the present disclosure, so it should be understood that a variety of other equivalents and modifications could have been made thereto at the time that the application was filed.

[0037] The terms including the ordinal number such as first, second and the like, are used to distinguish one element from another among various elements, but not intended to limit the elements.

[0038] Unless the context clearly indicates otherwise, it will be understood that the term comprises when used in this specification, specifies the presence of stated elements, but does not preclude the presence or addition of one or more other elements. Additionally, the term control unit as used herein refers to a processing unit of at least one function or operation, and may be implemented in hardware and software either alone or in combination.

[0039] In addition, throughout the specification, it will be further understood that when an element is referred to as being connected to another element, it can be directly connected to the other element or intervening elements may be present.

[0040] FIG. 1 is a diagram showing exemplarily an electric vehicle according to the present disclosure.

[0041] Referring to FIG. 1, the electric vehicle 1 includes a vehicle controller 2, a battery pack 10 and an electrical load 30. Charge/discharge terminals P+, P of the battery pack 10 may be electrically coupled to a charger 40 through a charging cable. The charger 40 may be included in the electric vehicle 1, or provided in a charging station outside of the electric vehicle 1.

[0042] The vehicle controller 2 (for example, an Electronic Control Unit (ECU)) is configured to transmit a key-on signal to the battery management system 100 in response to an ignition button (not shown) of 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 the ignition button being switched to an OFF-position by the user. The charger 40 may supply charge power (for example, constant current, constant voltage, constant power) through the charge/discharge terminals P+, P of the battery pack 10 in communication with the vehicle controller 2.

[0043] The battery pack 10 includes a battery group 11, a relay 20 and a battery management system 100.

[0044] The battery group 11 includes a series connection structure of batteries B.sub.1B.sub.N (N is a natural number of 2 or greater). That is, in the battery group 11, the batteries B.sub.1B.sub.N are connected in series. The batteries B.sub.1B.sub.N may include a unit cell having the same electrical and chemical specification or two or more units cells connected either in series or in parallel or both. The unit cell is a minimum unit of an energy storage element that can be independently charged and discharged. For example, the unit cell is not limited to a particular type and may include any type of cell that can be repeatedly charged and discharged, such as lithium ion cells.

[0045] Hereinafter, in the common description of the batteries B.sub.1B.sub.N, the symbol B is affixed to the battery.

[0046] The relay 20 is electrically connected in series to the battery group 11 through the power path connecting the battery group 11 and the electrical load 30. FIG. 1 shows that the relay 20 is connected between the positive terminal of the battery group 11 and one terminal P+ of the charge/discharge terminals. The on/off control of the relay 20 is performed 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 contactor that is turned on/off by the magnetic field of the coil or a semiconductor switch such as Metal Oxide Semiconductor Field Effect transistor (MOSFET).

[0047] The electrical load 30 includes an inverter 31 and an electric motor 32. The inverter 31 is provided to convert the direct current power from the battery group 11 included in the battery pack 10 to alternating current power in response to a command from the battery management system 100 or the vehicle controller 2. The electric motor 32 operates using the alternating current power from the inverter 31. The electric motor 32 may include, for example, a 3-phase alternating current motor.

[0048] When the relay 20 turns on and the battery B is charged/discharged, it is referred to as load condition (cycling condition).

[0049] When the relay 20 is switched from on to off, the battery B is in a no-load condition (rest, calendar), and a battery voltage of the battery B in the no-load condition may be referred to as a no-load voltage. The no-load voltage refers collectively to a relaxation voltage and an open circuit voltage (OCV). Specifically, when the battery B is changed from the load condition to the no-load condition, the no-load voltage of the battery B changes with reduced polarization in the battery B. The OCV indicates the no-load voltage when the voltage change of the battery B is less than a predetermined value as the battery B is kept in no-load condition for a predetermined time (for example, 2 hours) or more. That is, the OCV is the no-load voltage when the polarization of the battery B is negligible. The relaxation voltage indicates the no-load voltage with reduced polarization.

[0050] The battery management system 100 may include a battery monitor 110, a balancer 130 and a control circuit 140. The battery management system 100 may further include a communication circuit 150. Hereinafter, assume that the battery management system 100 includes the battery monitor 110, the control circuit 140 and the communication circuit 150.

[0051] The battery monitor 110 includes a voltage detection circuit 112. The battery monitor 110 may further include a current detector 114.

[0052] The voltage detection circuit 112 is connected to the positive and negative terminals of each of the batteries B.sub.1B.sub.N included in the battery group 11, and is configured to detect a voltage (referred to as a battery voltage) across the battery B and generate a voltage signal indicating the detected battery voltage.

[0053] The current detector 114 is connected in series to the battery group 11 through the current path between the battery group 11 and the inverter 31. The current detector 114 may include at least one of known current detection devices such as a shunt resistor and a hall effect device. Since the batteries B.sub.1B.sub.N are connected in series, the common charge/discharge current flows in the batteries B.sub.1B.sub.N.

[0054] FIG. 1 shows the shunt resistor used for the current detector 114. In this case, the voltage detection circuit 112 may output a current signal indicating the direction and magnitude of the charge/discharge current to the control circuit 140 based on the voltage across the shunt resistor. The current detector 114 may directly generate the current signal indicating the charge/discharge current flowing through the battery group 11 and output it to the control circuit 140.

[0055] The balancer 130 is configured to perform a balancing operation on the battery B that needs to be balanced among the batteries B.sub.1B.sub.N in response to a balancing command from the control circuit 140. Hereinafter, the battery B determined to be balanced is referred to as a target battery. The balancing command may include a target time for the target battery B among the batteries B.sub.1B.sub.N. The target time refers to a balancing duration required for the target battery B.

[0056] FIG. 1 shows an example of the balancer 130 including balancing circuits D.sub.1D.sub.N. The balancing circuits D.sub.1D.sub.N may be connected in parallel to the batteries B.sub.1B.sub.N in a one-to-one correspondence relationship. Hereinafter, in the common description of the balancing circuits D.sub.1D.sub.N, the symbol D is affixed to the battery.

[0057] 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 the balancing 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 MOSFET.

[0058] The control circuit 140 may be operably coupled to the relay 20, the battery monitor 110, the balancer 130 and the communication circuit 150. Operably coupled refers to connected directly/indirectly to transmit and receive a signal in one or two directions.

[0059] The control circuit 140 may be referred to as a battery controller, and may be implemented in hardware using at least one of digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), microprocessors or electrical units for performing the other functions.

[0060] The control circuit 140 may collect the voltage signal and/or the current signal from the battery monitor 110. In an example, the control circuit 140 may convert and record the analog signal collected from the battery monitor 110 to a digital value using an Analog to Digital Converter (ADC) provided therein. Alternatively, the battery monitor 110 itself may transmit the result of converting the analog signal to the digital value to the control circuit 140.

[0061] Memory 141 may include, for example, at least one type of storage medium of flash memory type, hard disk type, Solid State Disk (SSD) type, Silicon Disk Drive (SDD) type, multimedia card micro type, 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). The memory 141 may store data and programs required for the computational operation by the control circuit 140. The memory 141 may store data indicating the result of the computational operation by the control circuit 140. The memory 141 may store given functions, logics and algorithms to use them to detect an internal short circuit fault in the battery B. The memory 141 may be integrated into the control circuit 140.

[0062] The control circuit 140 may turn on the relay 20 in response to the key-on signal from the vehicle controller 2. The control circuit 140 may turn off the relay 20 in response to the key-off signal from the vehicle controller 2. The key-on signal is a signal that requests the switch from the no-load condition to the load condition. The key-off signal is a signal that requests the switch from the load condition to the no-load condition. Alternatively, instead of the control circuit 140, the vehicle controller 2 may be responsible for the on/off control of the relay 20.

[0063] 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.

[0064] The control circuit 140 may identify the maximum voltage and the minimum voltage of the batteries B.sub.1B.sub.N by monitoring the voltage of each battery B.sub.1B.sub.N. The maximum voltage is the highest one of the voltages of the batteries B.sub.1B.sub.N. The minimum voltage is the lowest one of the voltages of the batteries B.sub.1B.sub.N.

[0065] 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, controller area network (CAN) communication, and the wireless communication may be, for example, Zigbee or Bluetooth communication. The communication protocol is not limited to a particular type and may include any type of communication protocol that supports wired/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) to provide information received from the control circuit 140 and/or the vehicle controller 2 into a recognizable format for the user (a driver).

[0066] Hereinafter, the operations performed by the control circuit 140 to detect an internal short circuit fault in the battery will be described in detail.

[0067] The control circuit 140 determines a voltage value of the no-load voltage of the battery B.

[0068] When the battery B is in the no-load condition, the control circuit 140 may determine the voltage value of the no-load voltage of the battery B to be equal to the voltage value of the voltage of the battery B detected by the battery monitor 110.

[0069] When the battery B is in the load condition, the control circuit 140 may determine (estimate) the voltage value of the no-load voltage of the battery B based on the battery voltage of the battery B detected by the battery monitor 110 and the charge/discharge current of the battery B detected by the current detector 114 using a battery state estimation algorithm. In an example, according to the Ohm's law, the no-load voltage of the battery B may be estimated by subtracting the voltage corresponding to the multiplication of the charge/discharge current of the battery B by the internal resistance of the battery B from the battery voltage of the battery B detected by the battery monitor 110.

[0070] Alternatively, irrespective of whether the battery B is in the no-load condition or the load condition, the control circuit 140 may determine an estimated State Of Charge (SOC) of the battery B using the predetermined battery state estimation algorithm, and acquire a value of OCV associated with the estimated SOC of the battery B from a given SOC-OCV map (see FIG. 5). The battery state estimation algorithm may include the known algorithms (for example, the Kalman filter).

[0071] The control circuit 140 determines the target battery B among the batteries B.sub.1B.sub.N. When the battery group 11 is changed from the load condition to the no-load condition, the control circuit 140 may determine whether the balancing operation for at least one of batteries B.sub.1B.sub.N is necessary or not. The determination as to the presence or absence of the target battery B may be periodically performed while in the no-load condition from the time when the battery group 11 is changed from the load condition to the no-load condition, i.e., from the start of the no-load condition.

[0072] In an example, the control circuit 140 may set, as the target battery, the battery B of which the no-load voltage is higher than the minimum no-load voltage of the batteries B.sub.1B.sub.N by a reference value or more. In another example, the control circuit 140 may set, as the target battery, the battery B of which the estimated SOC is higher than the minimum SOC of the batteries B.sub.1B.sub.N by a reference value or more.

[0073] The control circuit 140 may determine a target capacity of the target battery B to be equal to capacity corresponding to a difference in voltage (or a difference in SOC) between the target battery (for example, B.sub.i) and a reference battery (for example, B.sub.j). The reference battery refers to a battery corresponding to the minimum no-load voltage (or the minimum SOC) among the batteries B.sub.1B.sub.N. The control circuit 140 may determine the target time for the target battery B using a given map as a correlation between the target capacity and the target time. The correlation between the target capacity and the target time may be determined through experiments performed on batteries having the same electrical and chemical performance as the battery B.

[0074] Alternatively, each time the balancing command is received, the balancer 130 may perform the balancing operation on the target battery B for a first time, and stop the balancing operation for a second time. Every time when the balancing operation of the balancer 130 is stopped, the control circuit 140 may identify the target battery B again among the batteries B.sub.1B.sub.N, and transmit the balancing command for the target battery B to the balancer 130.

[0075] The balancing command may be a high level voltage that is directly applied to the discharge switch 132 to induce the discharge switch 132 from off to on. The discharge switch 132 may be kept off while the balancing command is not received.

[0076] Meanwhile, when a switch from the no-load condition to load condition is requested during the balancing operation for the target battery B, the control circuit 140 may output a balancing stop command to the balancer 130. The balancer 130 may terminate the balancing operation for all the batteries B.sub.1B.sub.N in response to the balancing stop command.

[0077] FIG. 2 is a diagram for reference in describing an exemplary equalization circuit of the battery. In the specification, a normal battery refers to a battery free of an internal short circuit fault among the batteries B.sub.1B.sub.N, and a faulty battery refers to a battery in an internal short circuit fault among the batteries B.sub.1B.sub.N.

[0078] Referring to FIG. 2, the normal battery may be equalized as a series circuit of a direct current voltage source V.sub.DC, an internal resistor R.sub.0 and a RC pair R.sub.1, C. In contrast, the faulty battery may be equalized as a series circuit in which an additional resistor R.sub.ISC is connected between two terminals of the series circuit corresponding to the normal battery. The additional resistor R.sub.ISC acts as a path of a leakage current R.sub.ISC. For reference, the voltage of the direct current voltage source V.sub.DC is the OCV of the battery B, and the battery voltage is the total voltage of the series circuit of the direct current voltage source V.sub.DC, the internal resistor R.sub.0 and the RC pair R.sub.1, C. When the voltage of the RC pair R.sub.1, C is zero (0V), the relaxation voltage and the OCV are equal.

[0079] During the charging of the faulty battery, some of the charge power is not stored in the faulty battery and is consumed as the leakage current I.sub.ISC. Additionally, during the discharging of the faulty battery, some of the discharge power is not supplied to the electrical load 30 and is consumed as the leakage current I.sub.ISC. A reduction in resistance of the resistor R.sub.ISC indicates that the internal short circuit fault gets worse, and as the internal short circuit fault gets worse, the power consumption as the leakage current I.sub.ISC may increase.

[0080] As a result, in the charge, the voltage change (i.e., an increase in SOC) of the faulty battery is smaller than the normal battery. In contrast, in the discharge, the voltage change (i.e., a decrease in SOC) of the faulty battery is larger than the normal battery. Furthermore, even in the no-load condition, energy stored in the faulty battery is consumed as the leakage current I.sub.ISC.

[0081] FIGS. 3 to 6 are diagrams for reference in describing the principle of internal short circuit fault detection in the battery.

[0082] FIG. 3 shows the time-dependent changes of the no-load voltage of each of the battery B.sub.i and the battery B.sub.j over the period of time during which the battery group 11 is in the load condition (charge), the no-load condition, the load condition (discharge) and the no-load condition in a sequential order. In FIG. 3, assume that the battery B.sub.i is a normal battery, and the battery B.sub.j is a faulty battery.

[0083] Referring to FIG. 3, a curve 310 shows the no-load voltage of the battery B.sub.i, and a curve 320 shows the no-load voltage of the battery B.sub.j. The time tB is detection timing, i.e., the time at which the control circuit 140 detects a faulty battery among the batteries B.sub.1B.sub.N. The time tA is the past time that is earlier than the time tB by a referenced time t.sub.REF. The length of the reference time t.sub.REF may be preset. To help an understanding, assume that the no-load voltage of the battery B.sub.i and the no-load voltage of the battery B.sub.j are equal at the time tA.

[0084] The period of time from the time tA to the time t1 is a charging period, and the no-load voltages of the battery B.sub.i and the battery B.sub.j continuously rise. However, the no-load voltage of the battery B.sub.j rises more slowly than the battery B.sub.i and the voltage difference between the battery B.sub.i and the battery B.sub.j gradually increases over the charging period tAt1. That is, for the charging period tAt1, the voltage imbalances between the batteries B.sub.1B.sub.N gradually get worse.

[0085] The period of time from the time t1 to the time t4 is a no-load period, and the charge/discharge of the battery B.sub.i and the battery B.sub.j is stopped. The no-load voltage of the battery B.sub.j slowly drops for the no-load period t1t4 due to the leakage current (see FIG. 2). Meanwhile, the period from time t2 to time t3 is a period during which the balancing operation for the battery B.sub.i is performed, i.e., a balancing period of the battery B.sub.i. The control circuit 140 sets the battery B.sub.i among the batteries B.sub.1B.sub.N as the target battery between the time t1 and the time t2. In an example, when the no-load voltage of the battery B.sub.j is the minimum no-load voltage of the batteries B.sub.1B.sub.N at the time t1, the no-load voltage of the battery B.sub.i is higher than the no-load voltage of the battery B.sub.j, so the battery B.sub.i is set as the target battery. Among the remaining batteries, at least one battery of which the no-load voltage is at least lower than the no-load voltage may be additionally set as the target battery. As the balancing operation for the battery B.sub.i is performed, the no-load voltage of the battery B.sub.i continuously drops over the balancing period t243. That is, for the balancing period t2t3, the voltage imbalances between the batteries B.sub.1B.sub.N are gradually mitigated.

[0086] The period of time from the time t4 to the time t5 is a discharging period, and the no-load voltages of the battery B.sub.i and the battery B.sub.j continuously drop. The no-load voltage of the battery B.sub.j drops faster than the battery B.sub.i and the voltage difference between the battery B.sub.i and the battery B.sub.j gradually increases again over the discharging period t4t5. That is, for the discharging period t4t5, the voltage imbalances of the batteries B.sub.1B.sub.N gradually get worse.

[0087] The period of time from the time t5 to the time tB is a no-load period. The no-load voltage of the battery B.sub.j slowly drops over the no-load period t5-tB. The period of time from the time t6 to the time t7 is a balancing period of the battery W. The control circuit 140 sets the target battery among the batteries B.sub.1B.sub.N between the time t5 and the time t6. In an example, in the same way as the time t2, at the time t6, the battery B.sub.i is set as the target battery. As the balancing operation for the battery B.sub.i is performed, the no-load voltage of the battery B.sub.i continuously drops over the balancing period t6t7. That is, for the balancing period t6t7, the voltage imbalances between the batteries B.sub.1B.sub.N are mitigated again.

[0088] According to the above description made with reference to FIG. 3, each time the balancing operation for the battery B.sub.i is performed, a difference in no-load voltage between the battery B.sub.i and the battery B.sub.j reduces. Accordingly, it is impossible to identify whether the battery B.sub.j is faulty or not by comparing the no-load voltage of the batteries B.sub.1B.sub.N with a certain threshold at the time tB (the internal short circuit fault detection timing).

[0089] The present disclosure compensates the voltage value of the no-load voltage of each battery B.sub.1B.sub.N at the detection timing (time tB) using the balancing capacity of each battery B.sub.1B.sub.N for the period (i.e., tAtB) of the latest reference time t.sub.REF based on the internal short circuit fault detection timing (time tB). The compensated voltage value of the battery B indicates an estimated no-load voltage of the battery B at the detection timing (time tB) when the balancing operation for the battery B is not performed over the period of time tAtB. Accordingly, even though the voltage imbalances between the batteries B.sub.1B.sub.N at the detection timing (time tB) are insignificant, the battery B.sub.j may be detected as faulty.

[0090] The control circuit 140 may detect the faulty battery among the plurality of batteries B.sub.1B.sub.N at each detection timing of a predetermined time interval. In an example, the reference time t.sub.REF) may be 100 times larger than the time interval of two adjacent detection timings, and the period of time for the latest reference time t.sub.REF may be defined using a moving window. The control circuit 140 may detect the internal short circuit fault when the detection condition is satisfied. The detection condition may be, for example, the no-load condition in which the balancing for all the plurality of batteries B.sub.1B.sub.N is stopped.

[0091] The balancing capacity of the battery B for the period of time tAtB is the accumulated value of the discharge capacity of the battery B by the balancing operation for the period of time tAtB, i.e., the total discharge capacity over the period of time tAtB. The balancing capacity of the battery (for example, B.sub.j) in which the balancing operation has never been performed for the period of time tAtB is determined to be 0 Ah.

[0092] Hereinafter, the principle of determining the discharge capacity each time the balancing operation is performed once will be described.

[0093] FIG. 4 illustrates the balancing operation for the battery B.sub.i within the no-load period t1t4 in FIG. 3. A curve 410 and a curve 411 show the time-dependent changes of the no-load voltage and discharge capacity of the battery B.sub.i respectively. The voltage value of the no-load voltage of the battery B.sub.i is maintained at V2 from the time t1 to the time t2, continuously drops from the time t2 to the time t3 and reaches V3 at the time t3. The time t3 is the balancing end time of the battery B.sub.i.

[0094] The control circuit 140 may determine the discharge capacity of the battery B.sub.i by the balancing operation by applying a capacity estimation function to first balancing data of the balancing operation. The first balancing data includes a start voltage value and a duration of the balancing operation. The start voltage value indicates the no-load voltage of the battery B.sub.i at the start time t2 of the balancing operation, and in FIG. 4, the start voltage value is V2. The duration indicates a length of time from the balancing start time t2 to the balancing end time t3, and in FIG. 4, the duration is t.sub.BC=t3t2.

[0095] The capacity estimation function defines a correlation among the start voltage value, the duration and the discharge capacity, and may be determined through experiments performed on batteries having the same electrical and chemical performance as the battery B. The following Equation 1 is an example of the capacity estimation function.

[00001]$\begin{array}{cc}{Q}_{\mathrm{dis}}=\frac{V_{\mathrm{start}}}{R}{t}_{\mathrm{BC}}& <\mathrm{Equation}1>\end{array}$

[0096] In the above Equation 1, V.sub.start is the start voltage value, t.sub.BC is the duration, R is the preset resistance of the discharge resistor 131, and Q.sub.dis is the discharge capacity per balancing. V.sub.start/R indicates the balancing current flowing through the discharge resistor 131 at the start of the balancing operation.

[0097] The following Equation 2 is another example of the capacity estimation function.

[00002]$\begin{array}{cc}{Q}_{\mathrm{dis}}=\frac{V_{\mathrm{start}}+V_{\mathrm{end}}}{2R}{t}_{\mathrm{BC}}& <\mathrm{Equation}2>\end{array}$

[0098] In the above Equation 2, V.sub.end is the end voltage value, and the remaining factors are equal to Equation 1.

[0099] Alternatively, the control circuit 140 may determine the discharge capacity of the battery B.sub.i by the balancing operation by applying the SOC-OCV map to second balancing data of the balancing operation. The second balancing data includes the start voltage value and the end voltage value of the balancing operation. The end voltage value indicates the no-load voltage at the balancing end time t3, and in FIG. 4, the end voltage value is V3. FIG. 5 shows an example of the 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 may determine the discharge capacity of the battery B.sub.i by the balancing operation for the balancing period t2t3 by multiplying a difference between the two SOCs, i.e., Z2Z3 by the Full Charge Capacity (FCC) of the battery B.sub.i. The method for estimating the full charge capacity is well known and its detailed description is omitted.

[0100] Alternatively, from the start to the end of the balancing operation, the balancing capacity of the battery B may be directly calculated by finding the integral of the balancing current periodically calculated by applying the Ohm's law to the voltage and resistance of the discharge resistor 131.

[0101] The determination of the balancing capacity may be performed each time the balancing operation is performed once.

[0102] The balancing operation for the battery B.sub.i is performed twice for the period of time tAtB. Accordingly, the control circuit 140 may determine the balancing capacity of the battery B.sub.i or the total capacity consumed from the battery B.sub.i for the period of time tAtB by summing the discharge capacity for the balancing period t2t3 and the discharge capacity for the balancing period t6t7.

[0103] Referring to FIG. 5, the control circuit 140 may determine the estimated SOC of each battery B.sub.1B.sub.N at the detection timing (time tB). In an example, when the voltage value of the no-load voltage of the battery B.sub.i detected at the time tB is V.sub.i, the control circuit 140 may determine Z.sub.i corresponding to the voltage value V.sub.i as the estimated SOC of the battery B.sub.i by applying the SOC-OCV map to the voltage value V.sub.i.

[0104] The control circuit 140 may compensate the voltage value of the no-load voltage of each battery B.sub.1B.sub.N by applying a predetermined voltage compensation logic as described below to the balancing capacity of each battery B.sub.1B.sub.N for the latest reference time t.sub.REF on the basis of the detection timing (time tB). Specifically, the control circuit 140 may determine a SOC change amount Z.sub.i of the battery B.sub.i by dividing the balancing capacity of the battery B.sub.i by the full charge capacity of the battery B.sub.i. The control circuit 140 compensates the estimated SOC of the battery B.sub.i from Z.sub.i to Z.sub.i+ by adding the SOC change amount Z.sub.i to the estimated SOC 4. The control circuit 140 determines a voltage value V.sub.i+ corresponding to Z.sub.i+ by applying the SOC-OCV map to the compensated estimated SOC Z.sub.i+. The voltage value V.sub.i+ is the result of compensating the voltage value V.sub.i using the balancing capacity of the battery B.sub.i. In contrast, since the balancing operation has never been performed on the battery B.sub.j over the period of time tAtB, the compensated voltage value V.sub.j+ of the battery B.sub.j is equal to the voltage value V.sub.j detected at the time tB.

[0105] Referring back to FIG. 3, a curve 311 is the result of compensating the curve 310 by applying the time-dependent change of the balancing capacity of the battery B.sub.i to the curve 310. That is, the curve 311 shows the time-dependent change of the no-load voltage of the battery B.sub.i when the balancing operation for the battery B.sub.i has never been performed over the period of time tAtB. Since the balancing operation is not performed for the charging period tAt1, the curve 310 and the curve 320 completely overlap for the charging period tAt1. Additionally, since the balancing operation is not performed for the discharging period t4t5, a difference between the curve 310 and the curve 320 is equally maintained over the discharging period t4t5. As illustrated in FIG. 5, since the voltage value of the battery B.sub.i at the detection timing tB is compensated from V.sub.i to V.sub.i+, it can be seen that a difference with the voltage value V.sub.j of the battery B.sub.j is expanded.

[0106] The series of processes described above (the voltage compensate logic) is commonly applied to all the batteries B.sub.1B.sub.N at each detection timing. The control circuit 140 may determine a reference voltage value to be equal to the average or median of the compensated voltage values of two or more of the batteries B.sub.1B.sub.N at each detection timing. That is, the reference voltage value may be newly upgraded at each detection timing. In an example, the reference voltage value may be the average or median of (i) all the compensated voltage values or (ii) a predetermined number of compensated voltage values in the descending order among the compensated voltage values, determined for the batteries B.sub.1B.sub.N. Referring to FIG. 3, V.sub.R is the reference voltage value at the time tB. Alternatively, the reference voltage value may be a given value irrespective of the voltage change of the batteries B.sub.1B.sub.N.

[0107] The control circuit 140 may determine a voltage deviation or a difference between the reference voltage value and the compensated voltage value of the battery B at each detection timing. Additionally, the control circuit 140 may record, in the memory 141, a time-series indicating the time-dependent changes of the voltage deviation of the battery B determined multiple times in a sequential order over the period of time tAtB for the latest reference time t.sub.REF. When the voltage deviation of the battery B at some detection timings within the period of time tAtB is omitted, the omitted voltage deviation values may be added to the time-series by applying interpolation to the remaining voltage deviation values within the time-series. In FIG. 6, a curve 610 and a curve 620 show the time-dependent changes of the voltage deviation of the battery B.sub.i and the voltage deviation of the battery B.sub.j, respectively.

[0108] The control circuit 140 may determine a change amount of the voltage deviation of the battery B during the latest reference time t.sub.REF. In FIG. 6, V.sub.iA and V.sub.iB are the voltage deviation of the battery B.sub.i at time tA and tB, respectively, and the change amount of the voltage deviation of the battery B.sub.i is V.sub.iAV.sub.iB. Additionally, V.sub.iA and V.sub.iB are the voltage deviation of the battery B.sub.j at time tA and tB, respectively, and the change amount of the voltage deviation of the battery B.sub.j is V.sub.jAV.sub.jB. For reference, referring to FIG. 3, V.sub.iB=V.sub.i+V.sub.R, and V.sub.jB=V.sub.j+V.sub.R.

[0109] The control circuit 140 determines whether the battery B is in the internal short circuit fault or not by comparing the change amount of the voltage deviation of the battery B with the threshold at each detection timing. In an example, in case that (V.sub.iAV.sub.iB)< the threshold(V.sub.jAV.sub.jB) at the time tB, the battery B.sub.i is determined to be normal, and the battery B.sub.j is determined to be faulty.

[0110] The control circuit 140 may count the number of times the change amount of the voltage deviation of the battery B is equal to or larger than the threshold in succession by comparing the change amount of the voltage deviation of the battery B with the threshold at each detection timing, and determine that the battery B is in the internal short circuit fault when the counted number of times reaches a predetermined number of times.

[0111] FIGS. 7 and 8 are flowcharts exemplarily showing a battery management method according to a first embodiment of the present disclosure. The method of FIG. 7 may be repeatedly performed at a predetermined time interval. To help an understanding, the following description will be made under the assumption that the method of FIG. 7 is performed at the time tB.

[0112] Referring to FIGS. 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.sub.i and V.sub.j of FIG. 3 indicate the first voltage value of the battery B.sub.i and the first voltage value of the battery B.sub.j, respectively.

[0113] In step S710, the control circuit 140 compensates the first voltage value of the battery B using the balancing capacity of the battery B. The step S710 may include sub-routines S810, S820, S830 and S840 shown in FIG. 8.

[0114] In step S810, the control circuit 140 determines the estimated SOC of the battery B by applying the SOC-OCV map to the first voltage value of the battery B. Referring to FIG. 5, Z.sub.i is the estimated SOC of the battery B.sub.i corresponding to the first voltage value V.sub.i of the battery B.sub.i.

[0115] In step S820, the control circuit 140 determines the balancing capacity of the battery B. The balancing capacity of the battery B may be the accumulated value of the discharge capacity by the balancing operation performed on the battery B for the latest reference time t.sub.REF.

[0116] In step S830, the control circuit 140 compensates the estimated SOC of the battery B by adding the SOC change amount corresponding to the balancing capacity to the estimated SOC of the battery B. Referring to FIG. 5, the compensated estimated SOC Z.sub.i+ of the battery B.sub.i is acquired by adding Z.sub.i to Z.sub.i.

[0117] In step S840, the control circuit 140 determines the compensated first voltage value of the battery B by applying the SOC-OCV map to the compensated estimated SOC of the battery B. Referring to FIG. 5, the compensated first voltage value of the battery B is determined to be equal to V.sub.i+ corresponding to Z.sub.i+.

[0118] In step S720, the control circuit 140 determines the reference voltage value. V.sub.R in FIG. 3 is the reference voltage value at the time tB.

[0119] In step S730, the control circuit 140 determines the voltage deviation of the battery B to be equal to a difference between the compensated first voltage value of the battery B and the reference voltage value. Referring to FIG. 6, V.sub.iB and V.sub.jB are the voltage deviation of the battery B.sub.i and the voltage deviation of the battery B.sub.j, respectively.

[0120] In step S740, the control circuit 140 determines the change amount of the voltage deviation of the battery B for the latest reference time t.sub.REF. Referring to FIG. 6, (V.sub.iAV.sub.iB) is the change amount of the voltage deviation of the battery B.sub.i, and (V.sub.jAV.sub.jB) is the change amount of the voltage deviation of the battery B.sub.j.

[0121] In step S750, the control circuit 140 determines whether the change amount of the voltage deviation of the battery B is equal to or larger than the threshold. When a value of the step S750 is Yes, step S760 is performed.

[0122] In the step S760, the control circuit 140 detects the internal short circuit fault in the battery B. Additionally, the control circuit 140 may perform a predetermined protection operation. The protection operation may include outputting a diagnosis message notifying that the battery B is in the internal short circuit fault. The diagnosis message may be transmitted to the vehicle controller 2 through the communication circuit 150. The communication circuit 150 may output a warning signal to the user upon receiving the diagnosis message.

[0123] FIG. 9 is a flowchart exemplarily showing a battery management method according to a second embodiment of the present disclosure. The method of FIG. 9 may be repeatedly performed at a predetermined time interval. To help an understanding, the following description will be made under the assumption that the method of FIG. 9 is performed at the time tB.

[0124] Referring to FIG. 9, the process from the step S700 to the step S740 is the same as the first embodiment. After the step S740 is performed, step S910 is performed. In the step S910, the control circuit 140 determines whether the change amount of the voltage deviation of the battery B is equal to or larger than the threshold. When a value of the step S910 is Yes, step S920 is performed. When the value of the step S910 is No, step S922 is performed.

[0125] In the step S920, the control circuit 140 increases a fault count of the battery B by 1. In the step S922, the control circuit 140 resets the fault count of the battery B to be equal to an initial value (for example, 0).

[0126] In step S930, the control circuit 140 determines whether the fault count of the battery B is equal to or larger than a predetermined value. That is, the control circuit 140 determines if the number of times the change amount of the voltage deviation of the battery B is equal to or larger than the threshold is counted in succession the predetermined of times. When a value of the step S930 is Yes, step S940 is performed.

[0127] In the step S940, the control circuit 140 detects the internal short circuit fault in the battery B. In the same way as the first embodiment, the control circuit 140 may perform a predetermined protection operation.

[0128] The second embodiment as a variation of the first embodiment may prevent the incorrect fault detection.

[0129] The embodiments of the present disclosure described hereinabove are not implemented only through the apparatus and method, and may be implemented through programs that perform the functions corresponding to the configurations of the embodiments of the present disclosure or recording media having the programs recorded thereon, and such implementation may be easily achieved by those skilled in the art from the disclosure of the embodiments described above.

[0130] While the present disclosure has been hereinabove described with regard to a limited number of embodiments and drawings, the present disclosure is not limited thereto and it is obvious to those skilled in the art that various modifications and changes may be made thereto within the technical aspects of the present disclosure and the equivalent scope of the appended claims.

[0131] Additionally, as many substitutions, modifications and changes may be made to the present disclosure described hereinabove by those skilled in the art without departing from the technical aspects of the present disclosure, the present disclosure is not limited by the above-described embodiments and the accompanying drawings, and all or some of the embodiments may be selectively combined to allow various modifications.

TABLE-US-00001 (Description of Reference Numerals) 1: Electric vehicle 10: Battery pack B: Battery 100: Battery management system 110: Battery monitor 130: Balancer 140: Control circuit