Patent Publication Number: US-2023144351-A1

Title: Battery pack, battery system and precharge method

Description:
TECHNICAL FIELD 
     The present application claims priority to Korean Patent Application No. 10-2020-0128999 filed on Oct. 6, 2020 in the Republic of Korea, the disclosures of which are incorporated herein by reference. 
     The present disclosure relates to a battery pack, a battery system and a precharge method, and more particularly, to a battery pack, a battery system and a precharge method, which may accurately perform precharging by obtaining a capacitance of a capacitor at a load. 
     BACKGROUND ART 
     Recently, the demand for portable electronic products such as notebook computers, video cameras and portable telephones has increased sharply, and electric vehicles, energy storage batteries, robots, satellites and the like have been developed in earnest. Accordingly, high-performance batteries allowing repeated charging and discharging are being actively studied. 
     Batteries commercially available at present include nickel-cadmium batteries, nickel hydrogen batteries, nickel-zinc batteries, lithium batteries and the like. Among them, the lithium batteries are in the limelight since they have almost no memory effect compared to nickel-based batteries and also have very low self-charging rate and high energy density. 
     Conventionally, a precharge circuit is configured in parallel inside the battery pack, and before the capacitor of the battery and the load is connected to a main relay, the voltage is charged to the capacitor through the precharge circuit, and then the main relay is connected to prevent an excessive current caused by a voltage difference, thereby preventing an arc from occurring. 
     However, in order to perform the precharge, it is required to acquire the capacitance of the capacitor. Conventionally, the specifications of the load that can be connected to the battery pack are set in advance, so the capacitance of the capacitor could be known in advance. Alternatively, conventionally, the battery pack or the load directly measures the capacitance of the capacitor, thereby checking the capacitance at the battery pack. 
     That is, conventionally, there is a problem that it is compatible only with a load whose capacitance is known in advance, and there is a problem that a measurement module for directly measuring the capacitance must be provided. 
     DISCLOSURE 
     Technical Problem 
     The present disclosure is designed to solve the problems of the related art, and therefore the present disclosure is directed to providing a battery pack, a battery system and a precharge method, which receives a capacitance of a capacitor from a load before performing the precharge to obtain the capacitance and performs the precharge according to a duty ratio calculated based on the obtained capacitance. 
     These and other objects and advantages of the present disclosure may be understood from the following detailed description and will become more fully apparent from the exemplary embodiments of the present disclosure. Also, it will be easily understood that the objects and advantages of the present disclosure may be realized by the means shown in the appended claims and combinations thereof. 
     Technical Solution 
     A battery pack according to one aspect of the present disclosure is a battery pack, which includes at least one battery cell, a main relay provided on a charging and discharging path of the battery cell, and a precharge relay and a precharge resistor connected in parallel to the main relay on the charging and discharging path, and the battery pack may comprise: a connector configured such that a load including a capacitor is connected thereto; a communication part configured to receive a capacitance of the capacitor from the load through the connector, when the load is connected to the connector; and a controller configured to obtain the capacitance from the communication part, calculate a duty ratio corresponding to the capacitance, and precharge the capacitor by controlling an operation state of the precharge relay according to the calculated duty ratio. 
     A battery pack according to another aspect of the present disclosure may further comprise a storage part configured to map and store identification information of the load and the capacitance. 
     The communication part may be configured to further receive the identification information together with the capacitance from the load. 
     The controller may be configured to obtain the identification information and the capacitance received by the communication part, and determine whether to store the identification information and the obtained capacitance by comparing the obtained identification information with the identification information stored in the storage part. 
     The controller may be configured to map and store the obtained identification information and the obtained capacitance in the storage part, when the obtained identification information is not stored in the storage part. 
     When the obtained identification information is stored in the storage part but the obtained capacitance is different from the capacitance stored in the storage part, the controller may be configured to update the stored capacitance to the obtained capacitance to correspond to the stored identification information. 
     The main relay may be configured to have one end connected to one end of the battery cell and the other end connected to the connector. 
     The precharge relay may be configured to have one end connected between one end of the battery cell and one end of the main relay on the charging and discharging path and the other end connected to one end of the precharge resistor. 
     The precharge resistor may be configured to have one end connected to the other end of the precharge relay and the other end connected between the other end of the main relay and the connector on the charging and discharging path. 
     A battery system according to still another aspect of the present disclosure may comprise the battery pack according to one aspect of the present disclosure; and the load. 
     The load may be configured to include: a capacitor configured to have one end connected to a positive electrode terminal of the battery pack and the other end connected to a negative electrode terminal of the battery pack; a communication unit communicatively connected to the communication part; and a control unit configured to control the communication unit to output the capacitance of the capacitor and the identification information of the load to the communication part. 
     A battery pack according to still another aspect of the present disclosure may further include a connection detector configured to detect a connection between the load and the connector and output a connection detection signal when the connection between the load and the connector is detected. 
     The controller may be configured to output a request signal for requesting the capacitance of the capacitor and the identification information of the load to the communication unit through the communication part, when the connection detection signal is received from the connection detector. 
     The control unit may be configured to receive the request signal through the communication unit, generate a response signal including the identification information and the capacitance in response to the request signal, and control the communication unit to output the response signal to the communication part. 
     The load may further include a connection detection unit configured to detect a connection to the connector and output a connection signal to the control unit when the connection to the connector is detected. 
     The control unit may be configured to control the communication unit to output the capacitance and the identification information to the communication part, when the connection signal is received from the connection detection unit. 
     A precharge method according to still another aspect of the present disclosure is a precharge method of a battery pack that includes at least one battery cell, a main relay provided on a charging and discharging path of the battery cell, and a precharge relay and a precharge resistor connected in parallel to the main relay on the charging and discharging path and is configured to be connected to a load including a capacitor, and the precharge method may comprise: a capacitance receiving step of receiving a capacitance of the capacitor from the load, when the battery pack and the load are connected; a duty ratio calculating step of calculating a duty ratio corresponding to the capacitance; and a precharging step of precharging the capacitor by controlling an operation state of the precharge relay according to the calculated duty ratio. 
     Advantageous Effects 
     According to one aspect of the present disclosure, there is an advantage in that capacitance information of the capacitor is received and obtained from the load in advance before performing the precharge, and then the precharge may be performed based on the obtained capacitance. 
     The effects of the present disclosure are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       The accompanying drawings illustrate a preferred embodiment of the present disclosure and together with the foregoing disclosure, serve to provide further understanding of the technical features of the present disclosure, and thus, the present disclosure is not construed as being limited to the drawing. 
         FIG.  1    is a diagram schematically showing a battery pack according to an embodiment of the present disclosure. 
         FIG.  2    is a diagram schematically showing an exemplary configuration of the battery pack according to an embodiment of the present disclosure and a load. 
         FIG.  3    is a diagram schematically showing a battery system according to another embodiment of the present disclosure. 
         FIG.  4    is a diagram schematically showing a precharge method according to still another embodiment of the present disclosure. 
     
    
    
     BEST MODE 
     It should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present disclosure on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. 
     Therefore, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the disclosure, so it should be understood that other equivalents and modifications could be made thereto without departing from the scope of the disclosure. 
     Additionally, in describing the present disclosure, when it is deemed that a detailed description of relevant known elements or functions renders the key subject matter of the present disclosure ambiguous, the detailed description is omitted herein. 
     The terms including the ordinal number such as “first”, “second” and the like, may be used to distinguish one element from another among various elements, but not intended to limit the elements by the terms. 
     Throughout the specification, when a portion is referred to as “comprising” or “including” any element, it means that the portion may include other elements further, without excluding other elements, unless specifically stated otherwise. 
     Furthermore, the term “controller” described in the specification refers to a unit that processes at least one function or operation, and may be implemented by hardware, software, or a combination of hardware and software. 
     In addition, throughout the specification, when a portion is referred to as being “connected” to another portion, it is not limited to the case that they are “directly connected”, but it also includes the case where they are “indirectly connected” with another element being interposed between them. 
     Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. 
       FIG.  1    is a diagram schematically showing a battery pack  100  according to an embodiment of the present disclosure.  FIG.  2    is a diagram schematically showing an exemplary configuration of the battery pack  100  according to an embodiment of the present disclosure and a load  200 . 
     Referring to  FIG.  1   , the battery pack  100  according to an embodiment of the present disclosure may include a battery cell  110 , a main relay  120 , a precharge relay  130 , a precharge resistor  140 , a connector  150 , a communication part  160 , and a controller  170 . 
     Here, the battery cell  110  refers to one physically separable independent cell including a negative electrode terminal and a positive electrode terminal. For example, one pouch-type lithium polymer cell may be regarded as the battery cell  110 . 
     Specifically, the battery pack  100  includes at least one battery cell  110 , a main relay  120  provided on a charging and discharging path L of the battery cell  110 , and a precharge relay  130  and a precharge resistor  140  connected in parallel to the main relay  120  on the charging and discharging path L. 
     The main relay  120  may be configured to have one end connected to one end of the battery cell  110  and the other end connected to the connector  150 . 
     For example, in the embodiment of  FIG.  2   , the main relay  120  may be provided on the charging and discharging path L. Here, the charging and discharging path L is a current path provided inside the battery pack  100 , and may be a high current path that connects a positive electrode terminal P+ of the battery pack  100 , the battery cell  110 , and a negative electrode terminal P− of the battery pack  100 . One end of the main relay  120  may be connected to the positive electrode of the battery cell  110 , and the other end of the main relay  120  may be connected to the positive electrode terminal P+ of the battery pack  100 . 
     In addition, in the embodiment of  FIG.  2   , a second main relay  121  may be provided between the negative electrode of the battery cell  110  and the negative electrode terminal P− of the battery pack  100 . That is, the main relay  120  may be provided at the positive electrode of the battery cell  110 , and the second main relay  121  may be provided at the negative electrode of the battery cell  110 . 
     The precharge relay  130  may be configured to have one end connected between one end of the battery cell  110  and one end of the main relay  120  on the charging and discharging path L and the other end connected to one end of the precharge resistor  140 . 
     The precharge resistor  140  is configured to have one end connected to the other end of the precharge relay  130  and the other end connected between the other end of the main relay  120  and the connector  150  on the charging and discharging path L. 
     That is, the precharge relay  130  and the precharge resistor  140  may be connected in series with each other, and may be connected in parallel with the main relay  120  on the charging and discharging path L. 
     The connector  150  may be configured to allow a load  200  including a capacitor  210  to be connected thereto. Specifically, the connector  150  may include a positive electrode terminal P+ of the battery pack  100  and a negative electrode terminal P− of the battery pack  100 . 
     For example, in the embodiment of  FIG.  2   , the positive electrode terminal P+ and the negative electrode terminal P− of the battery pack  100  may be included in the connector  150 . In addition, since the load  200  is connected to the connector  150 , the battery pack  100  and the load  200  may be connected to each other. 
     The communication part  160  may be configured to receive a capacitance of the capacitor  210  from the load  200  through the connector  150 , when the load  200  is connected to the connector  150 . 
     For example, the communication part  160  may communicate with the load  200  by wire and/or wirelessly. The embodiment of  FIG.  2    may be an embodiment in which the communication part  160  communicates with the load  200  through a wired line. That is, in the embodiment of  FIG.  2   , the communication part  160  may be connected to the connector  150  and connected to the load  200  through the connector  150  by wire. Through the wired line, the communication part  160  may receive the capacitance from the load  200 . 
     The controller  170  may be configured to obtain the capacitance from the communication part  160 . 
     Preferably, the controller  170  and the communication part  160  may be connected to communicate with each other. When the communication part  160  receives the capacitance from the load  200 , the controller  170  may obtain the capacitance from the communication part  160 . 
     Also, the controller  170  may be configured to calculate a duty ratio corresponding to the capacitance. In addition, the controller  170  may be configured to precharge the capacitor  210  by controlling the operation state of the precharge relay  130  according to the calculated duty ratio. 
     Here, the duty ratio may be an ON/OFF ratio for controlling the operation state of the precharge relay  130 . Specifically, the controller  170  may alternately control the operation state of the precharge relay  130  to a turn-on state or a turn-off state according to the calculated duty ratio. Through this process, the capacitor  210  included in the load  200  is charged, thereby completing the precharge. 
     Meanwhile, in the embodiment of  FIG.  2   , while the precharge is in progress, the operation state of the main relay  120  may be a turn-off state, and the operation state of the second main relay  121  may be a turn-on state. In addition, the operation state of the precharge relay  130  may be controlled according to the duty ratio calculated by the controller  170 . 
     In general, for the precharge, the capacitance of the capacitor  210  included in the load  200  may be known in advance or may be checked by directly measuring the capacitance. In other words, since the capacitor  210  may be charged as much as the voltage corresponding to the capacitance only when the capacitance of the capacitor  210  of the load  200  is checked, it is most important to check the capacitance before performing the precharge in order to accurately perform the precharge. 
     However, it is practically impossible to know the capacitance of various types of loads  200  that can be connected to the battery pack  100  in advance. Also, it can be inefficient to measure the capacitance of the load  200  every time for the precharge in that the capacitance measurement module is forced. 
     For example, when the battery pack  100  is used for home use, various products may be connected to the battery pack  100 . In addition, these various products may include capacitors  210  having different capacitances according to specifications. In this case, the capacitance of some of the various products may not be set in advance in the controller  170 , and the controller  170  may precharge the product by setting an incorrect duty ratio. If the precharge is insufficiently performed, a ripple current may be generated to damage an element included in the battery pack  100  and/or an internal element of the load  200 . 
     Therefore, the battery pack  100  according to an embodiment of the present disclosure has an advantage of receiving and obtaining capacitance information of the capacitor  210  from the load  200  in advance before performing the precharge, and then performing the precharge based on the obtained capacitance. 
     In other words, since the battery pack  100  according to an embodiment of the present disclosure may perform accurate precharge to correspond to the capacity of the capacitor  210  after receiving and obtaining the capacitance from the load  200  in advance, there is an advantage of having excellent versatility and compatibility for various products that can be charged with the battery pack  100 . 
     Meanwhile, the controller  170  provided to the battery pack  100  according to an embodiment of the present disclosure may selectively include processors known in the art, application-specific integrated circuit (ASIC), other chipsets, logic circuits, registers, communication modems, data processing devices, and the like to execute various control logic performed in the present disclosure. Also, when the control logic is implemented in software, the controller  170  may be implemented as a set of program modules. At this time, the program module may be stored in a memory and executed by the controller  170 . The memory may be located inside or out of the controller  170  and may be connected to the controller  170  by various well-known means. 
     Referring to  FIGS.  1  and  2   , the battery pack  100  according to an embodiment of the present disclosure may further include a storage part  180 . 
     The storage part  180  may be configured to map and store identification information of the load  200  and the capacitance. 
     That is, in the storage part  180 , the identification information of the load  200  and the capacitance of the load  200  may be mapped and stored. For example, the capacitance of the load  200  may be checked through the identification information of the load  200  stored in the storage part  180 . 
     The communication part  160  may be configured to further receive the identification information together with the capacitance from the load  200 . That is, the identification information of the load  200  stored in the storage part  180  may be received by the communication part  160  from the load  200 . 
     For example, when the communication part  160  receives the identification information and the capacitance from the load  200 , the storage part  180  may map and store the identification information and the capacitance received by the communication part  160 . 
     In addition, the storage part  180  may store programs and data required for the controller  170 . That is, the storage part  180  may store data necessary for operation and function of each component of the battery pack  100 , data generated in the process of performing the operation or function, or the like. The storage part  130  is not particularly limited in its kind as long as it is a known information storage means that can record, erase, update and read data. As an example, the information storage means may include RAM, flash memory, ROM, EEPROM, registers, and the like. In addition, the storage part  180  may store program codes in which processes executable by the controller  170  are defined. 
     Meanwhile, the controller  170  may be configured to control the output power according to the battery cell  110  based on the capacitance received by the communication part  160  after the precharge of the capacitor  210  is completed. 
     Preferably, a power profile representing a correspondence between the capacitance of the capacitor  210  that may be included in the load  200  and the output power of the battery pack  100  may be preset. This power profile is configured to be used to determine the optimal output power corresponding to the capacitance of the capacitor  210  included in the load, and may be stored in advance in the storage part  180 . 
     If the capacitance of the capacitor  210  included in the load  200  is not preset in the controller  170 , the optimal output power for the load  200  may not be determined. That is, since the capacitance of the capacitor  210  included in the load  200  is not accurately recognized, the optimal output power for the load  200  may not be determined even when the power profile is considered. In this case, since the output power of the battery pack  100  is not controlled to the optimum output power, when the load  200  is charged by the battery pack  100 , a ripple current or a reverse voltage may be applied. 
     For example, when various products can be connected to the battery pack  100 , charging by the battery pack  100  may be unstable because the optimal output power is not determined even if the power profile is considered for a product whose capacitance is not preset. 
     Therefore, the battery pack  100  according to an embodiment of the present disclosure has an advantage of outputting power optimized to the load  200  based on the capacitance as well as performing precharge based on the capacitance directly received from the load  200 . That is, the battery pack  100  according to an embodiment of the present disclosure has an advantage of charging the load  200  stably. 
     The controller  170  may be configured to obtain the identification information and the capacitance received by the communication part  160 . 
     For example, in the embodiment of  FIG.  2   , the controller  170  may obtain both the identification information and the capacitance received by the communication part  160  from the load  200 . 
     In addition, the controller  170  may be configured to compare the obtained identification information with the identification information stored in the storage part  180  to determine whether to store the identification information and the obtained capacitance. 
     Specifically, when the obtained identification information is not stored in the storage part  180 , the controller  170  may be configured to map the obtained identification information and the obtained capacitance and store the same in the storage part  180 . 
     For example, when a new product (hereinafter, a first load) is connected to the battery pack  100 , identification information and capacitance for the first load may not be stored in the storage part  180 . The communication part  160  may receive the identification information of the first load and the capacitance of the capacitor  210  included in the first load from the first load. The controller  170  may map and store the first identification information of the first load and the first capacitance received by the communication part  160  in the storage part  180 . Thereafter, the controller  170  may set a first duty ratio corresponding to the first load based on the first capacitance of the first load. In addition, the controller  170  may precharge the capacitor  210  included in the first load by controlling the operation state of the precharge relay  130  according to the set first duty ratio. 
     Also, when the obtained identification information is stored in the storage part  180  but the obtained capacitance is different from the capacitance stored in the storage part  180 , the controller  170  may be configured to update the stored capacitance to the obtained capacitance to correspond to the stored identification information. 
     For example, although the same product (hereinafter referred to as a second load) as a product that has already been connected to the battery pack  100  is connected again, the capacitor  210  may be changed because the second load is repaired or changed. Alternatively, although the product is the same as a product that has already been connected to the battery pack  100 , the second load whose capacitor  210  is changed may be connected to the battery pack  100  as the manufacturing specifications are changed. 
     In this case, the storage part  180  may store identification information and capacitance for a product that has already been connected. That is, even though second identification information of the second load received by the communication part  160  from the second load is the same as the identification information already stored in the storage part  180 , the second capacitance of the second load received by the communication part  160  may be different from the capacitance already stored in the storage part  180 . Accordingly, the controller  170  may obtain the second identification information and the second capacitance of the second load from the communication part  160 , and update the capacitance corresponding to the identification information of the second load stored in the storage part  180  to the newly obtained second capacitance. Thereafter, the controller  170  may set a second duty ratio corresponding to the second load based on the updated second capacitance of the second load. In addition, the controller  170  may precharge the capacitor  210  included in the second load by controlling the operation state of the precharge relay  130  according to the set second duty ratio. 
       FIG.  3    is a diagram schematically showing a battery system  10  according to another embodiment of the present disclosure. 
     Referring to  FIG.  3   , the battery system  10  according to another embodiment of the present disclosure may include the battery pack  100  according to an embodiment of the present disclosure and a load  200 . 
     In addition, the load  200  may include a capacitor  210 , a communication unit  220 , and a control unit  230 . 
     The capacitor  210  may be configured to have one end connected to the positive electrode terminal P+ of the battery pack  100  and the other end connected to the negative electrode terminal P− of the battery pack  100 . 
     For example, in the embodiment of  FIG.  2   , one end of the capacitor  210  may be connected to the positive electrode terminal P+ of the battery pack  100  by being connected to the connector  150 . Also, the other end of the capacitor  210  may be connected to the negative electrode terminal P− of the battery pack  100  by being connected to the connector  150 . Accordingly, when the capacitor  210  is connected to the connector, a closed circuit connecting the positive electrode terminal P+ of the battery pack  100 , the battery cell  110 , the negative electrode terminal P− of the battery pack  100 , and the capacitor  210  may be formed. 
     The communication unit  220  may be configured to be communicatively connected to the communication part  160 . 
     The communication unit  220  may be configured to communicate with the communication part  160  by wire and/or wirelessly. 
     For example, in the embodiment of  FIG.  2   , the communication unit  220  may be communicatively connected to the communication part  160  through a wired line. The communication unit  220  may be connected to the connector  150  and may be connected to the communication part  160  by wire through the connector  150 . 
     The control unit  230  may be configured to control the communication unit  220  to output the capacitance of the capacitor  210  and the identification information of the load  200  to the communication part  160 . 
     Referring to  FIGS.  1  and  2   , the battery pack  100  may further include a connection detector  190 . 
     The connection detector  190  may be configured to detect a connection between the load  200  and the connector  150 , and output a connection detection signal when the connection between the load  200  and the connector  150  is detected. 
     Preferably, the connection detector  190  may detect whether the positive electrode terminal P+ and the negative electrode terminal P− of the battery pack  100  are connected to the capacitor  210 . In addition, the connection detection signal output by the connection detector  190  may be output to the controller  170 . 
     Upon receiving the connection detection signal from the connection detector  190 , the controller  170  may be configured to output a request signal for requesting the capacitance of the capacitor  210  and the identification information of the load  200  to the communication unit  220  through the communication part  160 . 
     Specifically, when receiving the connection detection signal from the connection detector  190 , the controller  170  may determine that the battery pack  100  and the load  200  are connected. In addition, when the battery pack  100  and the load  200  are connected, the communication part  160  of the battery pack  100  and the communication unit  220  of the load  200  may be connected to communicate with each other. Accordingly, the controller  170  may control the communication part  160  to output a request signal for requesting the identification information and the capacitance to the communication unit  220 . 
     That is, the controller  170  may obtain the capacitance by outputting the request signal to the load  200  before performing the precharge (when the battery pack  100  and the load  200  are connected) in order to accurately perform the precharge. In addition, the controller  170  may set a duty ratio corresponding to the obtained capacitance and perform precharge according to the set duty ratio. 
     Therefore, the battery system  10  according to another embodiment of the present disclosure has an advantage of preventing unexpected problems that may occur due to incompletely performed precharge in advance by obtaining the capacitance information first and then performing precharge to correspond to the obtained capacitance. 
     The control unit  230  may be configured to receive the request signal through the communication unit  220 . 
     For example, in the previous embodiment, when the controller  170  of the battery pack  100  receives the connection detection signal from the connection detector  190 , it may output a request signal for requesting the identification information of the load  200  and the capacitance. In addition, the control unit  230  of the load  200  may receive the request signal through the communication unit  220 . 
     The control unit  230  may be configured to generate a response signal including the identification information and the capacitance in response to the request signal, and to control the communication unit  220  to output the response signal to the communication part  160 . 
     Specifically, the control unit  230  may generate a response signal including the identification information of the load  200  and the capacitance of the capacitor  210  included in the load  200 . That is, the response signal generated by the control unit  230  may correspond to the request signal generated by the controller  170 . The control unit  230  may output the generated response signal through the communication unit  220 . The response signal output through the communication unit  220  may be received by the controller  170  through the communication part  160 . 
     Referring to  FIGS.  2  and  3   , the load  200  may further include a connection detection unit  240 . 
     The connection detection unit  240  may be configured to detect a connection to the connector  150 , and to output a connection signal to the control unit  230  when the connection to the connector  150  is detected. 
     That is, the connection detection unit  240  provided in the load  200  may have a configuration corresponding to the connection detector  190  provided in the battery pack  100 . 
     The control unit  230  may be configured to control the communication unit  220  to output the capacitance and the identification information to the communication part  160 , when receiving the connection signal from the connection detection unit  240 . 
     That is, the control unit  230  may output the capacitance and the identification information not only when the response signal is received through the communication unit  220  but also when the connection signal is received from the connection detection unit  240 . 
     For example, the connection detector  190  may not determine whether the battery pack  100  and the load  200  are connected since a defect occurs in the connection detector  190  provided in the battery pack  100 . In this case, if the control unit  230  can output the response signal only when receiving the request signal, precharge may not proceed or may be performed incorrectly. Accordingly, the load  200  may further include the connection detection unit  240  to determine whether the battery pack  100  and the load  200  are connected, and the control unit  230  may output the capacitance and the identification information through the communication unit  220  based on the connection signal. 
     Preferably, when both the connection detector  190  and the connection detection unit  240  operate normally, in order to prevent interference between the request signal output by the communication part  160  and the signal output by the communication unit  220 , the control unit  230  may output the capacitance and the identification information through the communication unit  220  after a predetermined time elapses from receiving the connection signal. That is, after receiving the connection signal, the control unit  230  may wait for a time (a predetermined time) for receiving the request signal if the state of the connection detector  190  is normal. In addition, the control unit  230  may output the capacitance and the identification information through the communication unit  220  when the request signal is not received for a predetermined time. 
     At least some of the components of the battery pack  100  according to an embodiment of the present disclosure may be implemented by supplementing or adding functions of components included in a conventional BMS. For example, the communication part  160 , the controller  170 , the storage part  180 , and the connection detector  190  of the battery pack  100  may be implemented as components of the BMS. In addition, such a BMS may be provided in the battery pack  100 . 
       FIG.  4    is a diagram schematically showing a precharge method according to still another embodiment of the present disclosure. 
     The precharge method may be applied to the battery pack  100  or the battery system  10  according to an embodiment of the present disclosure. Preferably, each step of the precharge method may be performed by the battery pack  100 . 
     Referring to  FIG.  4   , the precharge method may include a receiving step (S 100 ), a duty ratio calculating step (S 200 ), and a precharging step (S 300 ). 
     The receiving step (S 100 ) is a step of receiving the capacitance of the capacitor  210  from the load  200  when the battery pack  100  and the load  200  are connected, and may be performed by communication part  160 . 
     Preferably, when the battery pack  100  and the load  200  are connected, the communication part  160  may receive the identification information of the load  200  along with the capacitance from the load  200 . 
     The duty ratio calculating step (S 200 ) is a step of calculating a duty ratio corresponding to the capacitance, and may be performed by the controller  170 . 
     The controller  170  may obtain the capacitance of the capacitor  210  provided in the load  200  through the communication part  160 , and may calculate the duty ratio corresponding to the obtained capacitance. That is, the controller  170  may improve the accuracy of the precharge by directly calculating the duty ratio optimized for the load  200  before performing the precharge. 
     The precharging step (S 300 ) is a step of precharging the capacitor  210  by controlling the operation state of the precharge relay  130  according to the calculated duty ratio, and may be performed by the controller  170 . 
     For example, in the embodiment of  FIG.  2   , the controller  170  may control the operation state of the precharge relay  130  according to the calculated duty ratio. Through this, the capacitor  210  may be precharged. 
     The embodiments of the present disclosure described above may not be implemented only through an apparatus and a method, but may be implemented through a program that realizes a function corresponding to the configuration of the embodiments of the present disclosure or a recording medium on which the program is recorded. The program or recording medium may be easily implemented by those skilled in the art from the above description of the embodiments. 
     The present disclosure has been described in detail. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the disclosure, are given by way of illustration only, since various changes and modifications within the scope of the disclosure will become apparent to those skilled in the art from this detailed description. 
     Additionally, 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, and the present disclosure is not limited to the above-described embodiments and the accompanying drawings, and each embodiment may be selectively combined in part or in whole to allow various modifications. 
     REFERENCE SIGNS 
     
         
         
           
               10 : battery system 
               100 : battery pack 
               110 : battery cell 
               120 : main relay 
               121 : second main relay 
               130 : precharge relay 
               140 : precharge resistor 
               150 : connector 
               160 : communication part 
               170 : controller 
               180 : storage part 
               190 : connection detector 
               200 : load 
               210 : capacitor 
               220 : communication unit 
               230 : control unit 
               240 : connection detection unit