Patent Publication Number: US-2023163621-A1

Title: Battery management apparatus and method, and battery management system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2020-0142547 filed in the Korean Intellectual Property Office on Oct. 29, 2020, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     Embodiments disclosed in this document relate to a battery management apparatus and method, and a battery management system. 
     BACKGROUND ART 
     Recently, research and development of secondary batteries have been actively performed. Herein, the secondary batteries, which are chargeable/dischargeable batteries, may include all of conventional nickel (Ni)/cadmium (Cd) batteries, Ni/metal hydride (MH) batteries, etc., and recent lithium-ion batteries. Among the secondary batteries, a lithium-ion battery has a much higher energy density than those of the conventional Ni/Cd batteries, Ni/MH batteries, etc. Moreover, the lithium-ion battery may be manufactured to be small and lightweight, such that the lithium-ion battery has been used as a power source of mobile devices. In addition, the lithium-ion battery is attracting attention as a next-generation energy storage medium as a usage range thereof is expanded to a power source of electric vehicles. 
     Furthermore, the secondary battery is generally used as a battery pack including a battery module where a plurality of battery cells are connected to one another in series and/or in parallel. The battery pack may be managed and controlled by a battery management system in terms of a state and an operation. 
     For an electric vehicle using a battery including such battery cells, multiple battery cells are mounted, such that balancing for the battery cells is a key issue. However, when a cell balancing operation is performed while the power of the electric vehicle is turned off, the power of an auxiliary battery of the vehicle is consumed, which may shorten the lifespan of the auxiliary battery or cause discharge, and make the operation of the electric vehicle impossible. 
     DISCLOSURE 
     Technical Problem 
     Embodiments disclosed herein aim to provide a battery management apparatus and method, and a battery management system in which a battery cell balancing operation may be performed without power consumption of an auxiliary battery of a target device in a power-off state of the target device. 
     Technical problems of the embodiments disclosed herein are not limited to the above-described technical problems, and other unmentioned technical problems would be clearly understood by one of ordinary skill in the art from the following description. 
     Technical Solution 
     A battery management apparatus according to an embodiment disclosed herein includes a sensor sensing an operating state of a target device, a power manager managing power supply from an auxiliary battery based on the operating state of the target device, and a controller configured to perform a cell balancing operation for a plurality of battery cells according to an operating mode determined based on the operating state of the target device. 
     In an embodiment, the power manager may operate by using power originating from a battery module including the plurality of battery cells, when the target device is in a power-on state. 
     In an embodiment, the auxiliary battery may be charged by using the power originating from the battery module, when the power manager is supplied with power from the battery module. 
     In an embodiment, the power manager may be supplied with power from the auxiliary battery, when the target device is in a power-off state. 
     In an embodiment, when the target device is in a power-on state, the controller is configured to operate in a normal mode, calculate a cell balancing time for the plurality of battery cells, and perform the cell balancing operation based on the calculated cell balancing time. 
     In an embodiment, when the target device is switched to a power-off state before the cell balancing operation is terminated, the controller is configured to switch the operating mode to a low-power mode and perform the cell balancing operation for a remaining time of the calculated cell balancing time. 
     In an embodiment, the controller is configured to switch the operating mode to a normal mode every preset time and monitor a voltage of the plurality of battery cells in the normal mode to re-calculate the cell balancing time. 
     In an embodiment, the preset time may be determined based on at least one of specifications of the target device, characteristics of the plurality of battery cells, and a capacity of the auxiliary battery. 
     A battery management method according to an embodiment disclosed herein includes sensing, by a battery management apparatus, an operating state of a target device, managing, by a battery management apparatus, power supply from an auxiliary battery based on the operating state of the target device, and performing, by a battery management apparatus, a cell balancing operation for a plurality of battery cells according to an operating mode determined based on the operating state of the target device. 
     In an embodiment, the managing of the power supply from the auxiliary battery based on the operating state of the target device may include supplying the battery management apparatus with power from the auxiliary battery when the target device is in a power-off state. 
     In an embodiment, the performing of the cell balancing operation for the battery cells according to the operating mode determined based on the operating state of the target device may include operating in a normal mode, calculating a cell balancing time for the plurality of battery cells, and performing the cell balancing operation based on the calculated cell balancing time, when the target device is in a power-on state. 
     In an embodiment, the performing of the cell balancing operation for the plurality of battery cells according to the operating mode determined based on the operating state of the target device may include switching the operating mode to a low-power mode and performing the cell balancing operation for a remaining time of the calculated cell balancing time, when the target device is switched to a power-off state before the cell balancing operation is terminated. 
     In an embodiment, the battery management method may further include determining, by the battery management apparatus, whether a preset time has elapsed and monitoring, by the battery management apparatus, a voltage of the plurality of battery cells in the normal mode to re-calculate the cell balancing time, in a case where the preset time has elapsed. 
     A battery management system according to an embodiment disclosed herein includes a battery module including a plurality of battery cells and supplying power to a target device, a battery management apparatus configured to perform a cell balancing operation for a plurality of battery cells according to an operating mode determined based on an operating state of the target device, and generate at least one control command based on the operating state of the target device, a switch connecting or disconnecting a first auxiliary battery of the target device to or from the battery management apparatus in response to the control command, and a second auxiliary battery supplying power to the battery management apparatus. 
     In an embodiment, the at least one control command includes a first control command, and the battery management apparatus may generate the first control command for opening the switch to disconnect the first auxiliary battery from the battery management apparatus, when the target device is in a power-off state. 
     In an embodiment, the at least one control command further includes a second control command, and the battery management apparatus may generate the second control command for closing the switch when the target device is in the power-off state, and the second auxiliary battery is charged using power originating from the battery module when the switch is closed. 
     In an embodiment, when the target device is in a power-on state, the battery management apparatus may operate in a normal mode, calculate a cell balancing time for the plurality of battery cells, and perform the cell balancing operation based on the calculated time. 
     In an embodiment, when the target device is switched to a power-off state before the cell balancing operation is terminated, the battery management apparatus may switch the operating mode to the low-power mode and perform the cell balancing operation for a remaining time of the calculated time. 
     Advantageous Effects 
     A battery management apparatus and method and a battery management system according to an embodiment disclosed herein may perform a battery cell balancing operation without power consumption of an auxiliary battery of a target device in a power-off state of the target device. 
     The battery management apparatus and method and the battery management system according to an embodiment disclosed herein may charge the auxiliary battery of the battery management apparatus in the power-on state of the target device. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIGS.  1  and  2    are block diagrams of a battery management system according to an embodiment disclosed herein. 
         FIG.  3    is a view for describing in detail an operation of a battery management system, according to an embodiment disclosed herein. 
         FIG.  4    is a block diagram of a battery management apparatus according to an embodiment disclosed herein. 
         FIG.  5    is a view for describing an operation of a battery management apparatus, according to an embodiment disclosed herein. 
         FIG.  6    is a flowchart of a battery management method according to an embodiment disclosed herein. 
         FIG.  7    is a flowchart illustrating in more detail a battery management method according to an embodiment disclosed herein. 
         FIG.  8    illustrates a computing system that executes another battery management method, according to an embodiment disclosed herein. 
     
    
    
     MODE FOR INVENTION 
     Hereinafter, embodiments disclosed in this document will be described in detail with reference to the exemplary drawings. In adding reference numerals to components of each drawing, it should be noted that the same components are given the same reference numerals even though they are indicated in different drawings. In addition, in describing the embodiments disclosed in this document, when it is determined that a detailed description of a related known configuration or function interferes with the understanding of an embodiment disclosed in this document, the detailed description thereof will be omitted. 
     To describe a component of an embodiment disclosed herein, terms such as first, second, A, B, (a), (b), etc., may be used. These term is used merely for distinguishing one component from another component and does not limit the component to the essence, sequence, order, etc., of the component. The terms used herein, including technical and scientific terms, have the same meanings as terms that are generally understood by those skilled in the art, as long as the terms are not differently defined. Generally, the terms defined in a generally used dictionary should be interpreted as having the same meanings as the contextual meanings of the relevant technology and should not be interpreted as having ideal or exaggerated meanings unless they are clearly defined in the present application. 
     In the present specification, a ‘target device’ may include an electrical, electronic, or mechanical device that operates by receiving power from a battery pack including a plurality of battery cells, and herein, the ‘target device’ is described as an example of an electric vehicle (EV), but is not limited thereto. 
       FIGS.  1  and  2    are block diagrams of a battery management system according to an embodiment disclosed herein. 
     Referring to  FIG.  1   , a battery management system  100  according to an embodiment disclosed herein may include a battery module  110 , a battery management apparatus  120 , a first auxiliary battery  130 , a second auxiliary battery  140 , and a first switch  150 . 
     The battery module  110  may include a plurality of battery cells  111 ,  112 ,  113 , and  114 . Although the plurality of battery cells are illustrated as four in  FIG.  1   , the present invention is not limited thereto, and the battery module  110  may include n battery cells (n is a natural number greater than or equal to 2). The battery module  110  may supply power to a target device. To this end, the battery module  110  may be electrically connected to the target device (not shown). 
     The plurality of battery cells  111 ,  112 ,  113 , and  114  may be a lithium ion (Li-ion) battery, an Li-ion polymer battery, a nickel-cadmium (Ni—Cd) battery, a nickel hydrogen (Ni-MH) battery, etc., and may not be limited thereto. Meanwhile, although one battery module  110  is illustrated in  FIG.  1   , the battery module  110  may be configured in plural according to an embodiment. 
     The battery management apparatus  120  may manage and/or control a state and/or an operation of the battery module  110 . For example, the battery management apparatus  120  may manage and/or control the states and/or operations of the plurality of battery cells  111 ,  112 ,  113 , and  114  included in the battery module  110 . The battery management apparatus  120  may manage charging and/or discharging of the battery module  110 . 
     In addition, the battery management apparatus  120  may monitor a voltage, a current, a temperature, etc., of the battery module  110  and/or each of the plurality of battery cells  111 ,  112 ,  113 , and  114  included in the battery module  110 . A sensor or various measurement modules for monitoring performed by the battery management apparatus  120 , not shown, may be additionally installed in the battery module  110 , a charging/discharging path, any position of the battery module  110 , etc. The battery management apparatus  120  may calculate a parameter indicating a state of the battery module  110 , e.g., a state of charge (SOC), a state of health (SOH) etc., based on a measurement value such as monitored voltage, current, temperature, etc. 
     The battery management apparatus  120  may calculate a cell balancing time for the plurality of battery cells  111 ,  112 ,  113 , and  114 . For example, the battery management apparatus  120  may calculate a cell balancing time based on an SOC of each of the plurality of battery cells  111 ,  112 ,  113 , and  114 . The battery management apparatus  120  may determine a cell balancing target based on the SOC of each of the plurality of battery cells  111 ,  112 ,  113 , and  114 . The battery management apparatus  120  may perform a cell balancing operation based on the cell balancing time for a battery cell determined as the cell balancing target among the plurality of battery cells  111 ,  112 ,  113 , and  114 . 
     The battery management apparatus  120  may sense an operating state of a target device (not shown). For example, the battery management apparatus  120  may directly sense the operating state of the target device, or detect the operating state of the target device by receiving information about the operating state from the target device. The battery management apparatus  120  may manage power supply from the second auxiliary battery  140  based on the operating state of the target device. For example, the battery management apparatus  120  may operate by receiving power originating from the battery module  110  or by receiving power from the second auxiliary battery  140 , based on the operating state of the target device. To this end, the battery management apparatus  120  may generate a control command for controlling opening and closing of the first switch  150 , based on the operating state of the target device. 
     For example, when the target device is in a power-off state, the battery management apparatus  120  may be supplied with power from the second auxiliary battery  140  by opening the first switch  150 . That is, the battery management apparatus  120  may cut off power supply from the first auxiliary battery  130  when the target device is in the power-off state. Thus, the battery management apparatus  120  may perform the cell balancing operation without consuming the power of the first auxiliary battery  130  of the target device while the target device is in the power-off state. 
     Meanwhile, the battery management apparatus  120  may close the first switch  150  when the target device is in a power-on state, thereby operating using the power originating from the battery module  110  and/or the power supplied from the first auxiliary battery  130 . In this case, the first auxiliary battery  130  and the second auxiliary battery  140  may be charged using the power originating from the battery module  110 . This will be described in more detail with reference to  FIG.  3    below. 
     The battery management apparatus  120  may determine an operating mode based on the operating state of the target device. For example, the battery management apparatus  120  may determine the operating mode as a normal mode when the target device is in the power-on state, and determine the operating mode as a low-power mode when the target device is in the power-off state. Here, the low-power mode may be defined as an operating mode where power consumption of the battery management apparatus  120  is lower than in the normal mode, and in one aspect, the low-power mode may be defined as an operating mode in which the battery management device  120  performs contents or time of the operation restrictively compared to in the normal mode. 
     When operating in the normal mode, the battery management apparatus  120  may calculate the cell balancing time for the plurality of battery cells  111 ,  112 ,  113 , and  114  and perform the cell balancing operation based on the calculated cell balancing time. When operating in the low-power mode, the battery management apparatus  120  may perform the cell balancing operation based on the cell balancing time calculated in the normal mode. In addition, when the operating mode is switched from the normal mode to the low-power mode according to the operating state of the target device, the battery management apparatus  120  may perform the cell balancing operation for the remaining time of the cell balancing time calculated in the normal mode, except for a time in which the cell balancing operation is performed. Accordingly, when the battery management apparatus  120  operates in the low-power mode, power consumption of the second auxiliary battery  140  may be reduced. 
     In addition, the battery management apparatus  120  may switch the operating mode from the low-power mode to the normal mode every preset time. The battery management apparatus  120  may re-calculate a cell balancing time by monitoring a voltage of the plurality of battery cells  111 ,  112 ,  113 , and  114 . Here, the preset time may be determined based on at least some of the specifications of the target device, characteristics of the plurality of battery cells  111 ,  112 ,  113 , and  114 , and the capacity of the second auxiliary battery  140 . 
     Also, the battery management apparatus  120  may determine whether the cell balancing operation is completed. For example, the battery management apparatus  120  may determine that cell balancing is completed in a case where a reference time has elapsed, or determine whether cell balancing is completed based on the SOC of the plurality of battery cells  111 ,  112 ,  113 , and  114 . Here, the reference time may be determined based on at least some of the specifications of the target device, characteristics of the plurality of battery cells  111 ,  112 ,  113 , and  114 , and the capacity of the second auxiliary battery  140 . 
     As such, the battery management apparatus  120  may operate in the low-power mode and then be switch to the normal mode every preset time to re-calculate the cell balancing time, and may perform the cell balancing operation only for the remaining time when the battery management apparatus  120  is switched back to the low-power mode, thereby reducing power consumption of the secondary auxiliary battery  140 . 
     The first auxiliary battery  130  may basically supply power to the target device. For example, the first auxiliary battery  130  may be an auxiliary power provided for driving and/or an operation of the target device. Also, the first auxiliary battery  130  may supply power to the battery management apparatus  120  electrically connected through the first switch  150 . For example, the first auxiliary battery  130  may supply power to the battery management apparatus  120  when the first switch  150  is closed. Meanwhile, the first auxiliary battery  130  may be charged using the power originating from the battery module  110 , when the target device is in the power-on state. 
     The second auxiliary battery  140  may supply power to the battery management apparatus  120 . The second auxiliary battery  140  may be connected in parallel with the first auxiliary battery  130 , and may be electrically connected to the first auxiliary battery  130  through the first switch  150 . For example, the second auxiliary battery  140  may be an auxiliary power provided for driving and/or an operation of the battery management apparatus  120 . Meanwhile, the second auxiliary battery  140  may be charged using the power originating from the battery module  110  identically to the first auxiliary battery  130 , when the target device is in the power-on state. This may be possible by connecting the second auxiliary battery  140  to the first auxiliary battery  130  in parallel. 
     The first switch  150  may be electrically connected to the battery management apparatus  120 , the first auxiliary battery  130 , and the second auxiliary battery  140 . The first switch  150  may be opened or closed in response to a control command transmitted from the battery management apparatus  120 . For example, the battery management apparatus  120  may generate a control command for opening the first switch  150  when the target device is in the power-on state, and generate a control command for closing the first switch  150  when the target device is in the power-off state. 
     Referring to  FIG.  2   , the battery management system  100  according to an embodiment disclosed herein may be exemplarily divided into a target device area A 1  and a battery management system area A 2 . 
     For example, the target device area A 1  may be defined as an area including components provided in the target device and may be defined as an area including the first auxiliary battery  130 . 
     The battery management system area A 2  may be defined as an area including components related to a battery mounted in the target device, and may be defined as an area including the battery module  110 , the battery management apparatus  120 , the second auxiliary battery  140 , and the switch  150 . In one aspect, the battery management system area A 2  may be defined as being included in a battery pack. However, according to an embodiment, the first switch  150  may be included in the target device area A 1 . 
       FIG.  3    is a view for describing in detail an operation of a battery management system, according to an embodiment disclosed herein. 
     Referring to  FIG.  3   , when the target device (not shown) is in the power-on state, the first auxiliary battery  130  and the second auxiliary battery  140  may be charged using the power originating from the battery module  110 . More specifically, the first switch  150  and the second switch  170  may be controlled to be closed when the target device is in the power-on state. For example, the first switch  150  may be closed in response to a control command cmd transmitted from the battery management apparatus  120 . The second switch  170  may be controlled to be closed by the target device, but is not limited thereto, and may be controlled by the battery management apparatus  120  according to an embodiment. 
     When the first switch  150  and the second switch  170  are closed, the power transmitted from the battery module  110  may be converted through a converter  160 , and may be delivered to the battery management apparatus  120 , the first auxiliary battery  130 , and the second auxiliary battery  140 . Here, the converter  160  may include a direct current-to-direct current (DC-DC) converter. Thus, when the target device is in the power-on state, the first auxiliary battery  130  and the second auxiliary battery  140  may be charged using the power originating from the battery module  110 . 
     Meanwhile, the battery management apparatus  120  may control the first switch  150  to be opened when the target device is in the power-off state. When the first switch  150  is opened, the battery management apparatus  120  may operate using the power supplied from the second auxiliary battery  140 . Thus, power consumption of the first auxiliary battery  130  due to the battery management apparatus  120  may be prevented when the target device is in the power-off state. Meanwhile, the second switch  170  may be controlled to be opened by the target device when the target device is in the power-off state. 
     Hereinafter, a connection relationship among the battery module  110 , the battery management apparatus  120 , the first auxiliary battery  130 , the second auxiliary battery  140 , the first switch  150 , the converter  160 , and the second switch  170  will be described in detail. 
     The battery management apparatus  120 , the first auxiliary battery  130 , and the second auxiliary battery  140  may be connected in parallel with the battery module  110 . More specifically, the battery management apparatus  120 , the first auxiliary battery  130 , and the second auxiliary battery  140  may be connected in parallel with the battery module  110  with respect to a second node N 2  and a third node N 3 . 
     The first auxiliary battery  130  and the second auxiliary battery  140  may be connected in parallel with the battery management apparatus  120 . More specifically, the first auxiliary battery  130  and the second auxiliary battery  140  may be connected in parallel with the battery management apparatus  120  through a first node N 1  and the second node N 2 . 
     More specifically, the battery management apparatus  120  and positive (+) terminals of the second auxiliary battery  140  may be connected to each other through the first node N 1 . A negative (−) terminal of the first auxiliary battery  130  and a negative (−) terminal of the second auxiliary battery  140  may be connected to the converter  160  through the second node N 2 . The positive (+) terminal of the first auxiliary battery  130  may be connected to the first switch  150  and the second switch  170  through the third node N 3 . 
     Hereinafter, the battery management apparatus  120  according to an embodiment disclosed herein will be described in detail with reference to  FIGS.  4  and  5   . 
       FIG.  4    is a block diagram of a battery management apparatus according to an embodiment disclosed herein.  FIG.  5    is a view for describing an operation of a battery management apparatus, according to an embodiment disclosed herein. 
     Referring to  FIG.  4   , the battery management apparatus  120  according to an embodiment disclosed herein may include a sensing unit  121 , a power managing unit  122 , and a control unit  123 . 
     The sensing unit  121  may sense the operating state of the target device. The sensing unit  121  may transmit a sensing result to the power managing unit  122  and/or the control unit  123 . For example, the sensing unit  121  may directly sense the operating state of the target device, or detect the operating state of the target device by receiving information about the operating state from the target device. 
     The power managing unit  122  may manage power supply from the second auxiliary battery  140  based on the sensing result. For example, the power managing unit  122  may be supplied with the power originating from the battery module  110  or may be supplied with the power from the second auxiliary battery  140 , based on the operating state of the target device. To this end, the power managing unit  122  may generate a control command for controlling opening and closing of the first switch  150 , based on the operating state of the target device. 
     For example, when the target device is in the power-off state, the power managing unit  122  may be supplied with power from the second auxiliary battery  140  by opening the first switch  150 . Thus, the battery management apparatus  120  may perform the cell balancing operation without consuming the power of the first auxiliary battery  130  of the target device while the target device is in the power-off state. 
     Meanwhile, the power managing unit  122  may be supplied with the power originating from the battery module  110  and/or the power from the first auxiliary battery  130  by closing the first switch  150 , when the target device is in the power-on state. Thus, when the target device is in the power-on state, the first auxiliary battery  130  and the second auxiliary battery  140  may be charged using the power originating from the battery module  110  through the converter  160  (see  FIG.  3   ). This may be possible by connecting the second auxiliary battery  140  to the first auxiliary battery  130  in parallel. 
     The control unit  123  may determine the operating mode based on the sensing result of the sensing unit  121 . For example, the control unit  123  may determine the operating mode as the normal mode when the target device is in the power-on state, and determine the operating mode as the low-power mode when the target device is in the power-off state. Here, the low-power mode may be defined as an operating mode where power consumption of the battery management apparatus  120  is lower than in the normal mode, and in one aspect, the low-power mode may be defined as an operating mode in which the battery management apparatus  120  performs contents or time of the operation restrictively compared to in the normal mode. 
     Referring to  FIG.  5   , when operating in the normal mode, the control unit  123  may calculate a cell balancing time BT for the plurality of battery cells  111 ,  112 ,  113 , and  114  and perform the cell balancing operation based on the calculated cell balancing time BT. 
     When operating in the low-power mode, the control unit  123  may perform the cell balancing operation based on the cell balancing time BT calculated in the normal mode. In addition, when the operating mode is switched from the normal mode to the low-power mode at a predetermined time t 1  according to the operating state of the target device, the control unit  123  may perform the cell balancing operation for a remaining time BT 2  of the cell balancing time calculated in the normal mode, except for a cell balancing time BT 1  in which the cell balancing operation is performed. 
     In addition, the control unit  123  may switch the operating mode from the low-power mode to the normal mode every preset time. The control unit  123  may re-calculate the cell balancing time by monitoring a voltage of the plurality of battery cells  111 ,  112 ,  113 , and  114 , in the normal mode. As such, the control unit  123  may operate in the low-power mode and then be switched to the normal mode every preset time to re-calculate the cell balancing time, and may perform the cell balancing operation only for the remaining time when the battery management apparatus  120  is switched back to the low-power mode, thereby reducing power consumption of the secondary auxiliary battery  140 . Here, the preset time may be determined based on at least some of the specifications of the target device, characteristics of the plurality of battery cells  111 ,  112 ,  113 , and  114 , and the capacity of the second auxiliary battery  140 . 
     In addition, the control unit  123  may determine whether the cell balancing operation is completed. For example, the control unit  123  may determine that cell balancing is completed in a case where a reference time has elapsed, or determine whether cell balancing is completed based on the SOC of the plurality of battery cells  111 ,  112 ,  113 , and  114 . Here, the reference time may be determined based on at least some of the specifications of the target device, characteristics of the plurality of battery cells  111 ,  112 ,  113 , and  114 , and the capacity of the second auxiliary battery  140 . 
     Meanwhile, the power managing unit  122  and the control unit  123  are illustrated as separate components in  FIG.  4   , but may also be configured as one component (e.g., a processor) depending on an embodiment. 
       FIG.  6    is a flowchart of a battery management method according to an embodiment disclosed herein. 
     Referring to  FIG.  6   , a battery management method according to an embodiment disclosed herein may include operation S 110  of sensing an operating state of a target device, operation S 120  of managing power supply from an auxiliary battery based on the operating state of the target device, and operation S 130  of performing a cell balancing operation for a plurality of battery cells according to an operating mode determined based on the operating state of the target device. 
     Hereinbelow, operations S 110  through S 130  will be described in detail with reference to  FIG.  4   . 
     In operation S 110 , the sensing unit  121  may sense the operating state of the target device. The sensing unit  121  may transmit a sensing result to the power managing unit  122  and/or the control unit  123 . 
     In operation S 120 , the battery managing unit  122  may manage power supply from the second auxiliary battery  140  based on the sensing result. For example, when the target device is in the power-off state, the power managing unit  122  may be supplied with power from the second auxiliary battery  140  by opening the first switch  150 . Thus, the battery management apparatus  120  may perform the cell balancing operation without consuming the power of the first auxiliary battery  130  of the target device while the target device is in the power-off state. 
     In addition, the power managing unit  122  may be supplied with the power originating from the battery module  110  and/or the power from the first auxiliary battery  130  by closing the first switch  150 , when the target device is in the power-on state. 
     In operation S 130 , the control unit  123  may determine the operating mode based on the sensing result of the sensing unit  121 . For example, the control unit  123  may determine the operating mode as the normal mode when the target device is in the power-on state, and determine the operating mode as the low-power mode when the target device is in the power-off state. Here, the low-power mode may be defined as an operating mode where power consumption of the battery management apparatus  120  is lower than in the normal mode, and in one aspect, the low-power mode may be defined as an operating mode in which the battery management apparatus  120  performs contents or time of the operation restrictively compared to in the normal mode. 
     When operating in the normal mode, the control unit  123  may calculate the cell balancing time BT for the plurality of battery cells  111 ,  112 ,  113 , and  114  and perform the cell balancing operation based on the calculated cell balancing time BT. 
     When operating in the low-power mode, the control unit  123  may perform the cell balancing operation based on the cell balancing time BT calculated in the normal mode. In addition, when the operating mode is switched from the normal mode to the low-power mode at a predetermined time t 1  according to the operating state of the target device, the control unit  123  may perform the cell balancing operation for a remaining time BT 2  of the cell balancing time calculated in the normal mode, except for a cell balancing time BT 1  in which the cell balancing operation is performed. 
       FIG.  7    is a flowchart illustrating in more detail a battery management method according to an embodiment disclosed herein. 
     Referring to  FIG.  7   , the battery management method according to an embodiment disclosed herein may include operation S 210  of sensing an operating state of a target device, operation S 220  of receiving power originating from a battery module, operation S 230  of operating in the normal mode, operation S 240  of calculating a cell balancing time, operation S 250  of performing a cell balancing operation, operation S 260  of receiving power form a second auxiliary battery, operation S 270  of operating in the low-power mode, operation S 280  of performing the cell balancing operation for the remaining time of the cell balancing time calculated in the normal operation, operation S 290  of determining whether a preset time has elapsed, operation S 300  of switching to the normal mode, operation S 310  of re-calculating the cell balancing time, and operation S 320  of determining whether cell balancing is completed. 
     Hereinbelow, operations S 210  through S 320  will be described in detail with reference to  FIG.  4   . 
     As a result of sensing in operation S 210 , when the target device is in the power-on state, operations S 220  to S 250  may be performed. 
     In operation S 210 , the sensing unit  121  may sense the operating state of the target device. The sensing unit  121  may transmit a sensing result to the power managing unit  122  and/or the control unit  123 . 
     In operation S 220 , the power managing unit  122  may be supplied with the power originating from the battery module  110  and/or the power from the first auxiliary battery  130  by closing the first switch  150 , when the target device is in the power-on state. 
     In operation S 230 , the control unit  123  may determine the operating mode as the normal mode and operate the battery management apparatus  120  in the normal mode. 
     In operation S 240 , the control unit  123  may calculate a cell balancing time for each of the plurality of battery cells  111 ,  112 ,  113 , and  114 . 
     In operation S 250 , the control unit  123  may perform a cell balancing operation for the plurality of battery cells  111 ,  112 ,  113 , and  114 . 
     As a result of sensing in operation S 210 , when the target device is in the power-off state, operations S 260  to S 290  may be performed. 
     In operation S 260 , when the target device is in the power-off state, the power managing unit  122  may be supplied with power from the second auxiliary battery  140  by opening the first switch  150 . That is, the power managing unit  122  may cut off power supply from the first auxiliary battery  130  when the target device is in the power-off state. 
     In operation S 270 , the control unit  123  may determine the operating mode as the low-power mode and operate the battery management apparatus  120  in the low-power mode. 
     In operation S 280 , the control unit  123  may perform the cell balancing operation for the remaining time of the cell balancing time calculated in the normal mode, except for the time in which the cell balancing operation is performed. 
     In operation S 290 , the control unit  123  may determine whether the preset time has elapsed. In a case where the preset time has elapsed as a result of performing operation S 290 , operations S 300  to S 320  may be performed. 
     In operation S 300 , the control unit  123  may switch the operating mode to the normal mode. 
     In operation S 310 , the control unit  123  may monitor the plurality of battery cells  111 ,  112 ,  113 , and  114  to re-calculate a cell balancing time. 
     In operation S 320 , the control unit  123  may determine whether the cell balancing operation is completed. For example, the control unit  123  may determine that cell balancing is completed in a case where a reference time has elapsed, or determine whether cell balancing is completed based on the SOC of the plurality of battery cells  111 ,  112 ,  113 , and  114 . 
     When the cell balancing is not completed as a result of performing operation S 320 , operation S 280  may be performed. 
       FIG.  8    illustrates a computing system that executes another battery management method, according to an embodiment disclosed herein. 
     Referring to  FIG.  8   , a computing system  200  according to an embodiment disclosed herein may include a microcontroller unit (MCU)  210 , a memory  220 , an input/output interface (I/F)  230 , and a communication I/F  240 . 
     The MCU  210  may be a processor that executes various programs (e.g., an SOH calculation program, a cell balancing target determination program, etc.) stored in the memory  220 , processes various data including an SOC, an SOH, etc., of a plurality of battery cells through these programs, executes functions of the battery management apparatus  120  described above with reference to  FIGS.  1  to  5   , or executes the battery management method described with reference to  FIGS.  6  and  7   . 
     The memory  220  may store various programs regarding SOH calculation of the battery cell, cell balancing target determination, etc. Moreover, the memory  220  may store various data such as SOC data, SOH data, etc., of each battery cell. 
     The memory  220  may be provided in plural, depending on a need. The memory  220  may be a volatile memory or a nonvolatile memory. For the memory  220  as the volatile memory, random access memory (RAM), dynamic RAM (DRAM), static RAM (SRAM), etc., may be used. For the memory  220  as the nonvolatile memory, read only memory (ROM), programmable ROM (PROM), electrically alterable ROM (EAROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), flash memory, etc., may be used. The above-listed examples of the memory  220  are merely examples and are not limited thereto. 
     The input/output I/F  230  may provide an interface for transmitting and receiving data by connecting an input device (not shown) such as a keyboard, a mouse, a touch panel, etc., and an output device such as a display (not shown), etc., with the MCU  210 . 
     The communication I/F  230 , which is a component capable of transmitting and receiving various data to and from a server, may be various types of devices capable of supporting wired or wireless communication. For example, a program for SOH calculation of the battery cell or balancing target determination or various data, etc., may be transmitted and received to and from a separately provided external server through the communication I/F  230 . 
     As such, the battery management method according to an embodiment disclosed herein may be recorded in the memory  220  and executed by the MCU  210 . 
     The above description is merely illustrative of the technical idea of the present invention, and various modifications and variations will be possible without departing from the essential characteristics of embodiments of the present invention by those of ordinary skill in the art to which the embodiments disclosed herein pertains. 
     Therefore, the embodiments disclosed herein are intended for description rather than limitation of the technical spirit of the embodiments disclosed herein and the scope of the technical spirit of the present invention is not limited by these embodiments disclosed herein. The protection scope of the technical spirit disclosed herein should be interpreted by the following claims, and all technical spirits within the same range should be understood to be included in the range of the present invention.