Starting battery driving system and external system off-state recognition method using same

The present invention relates to a voltage recognition system of a starting battery and a method of recognizing an off state of an external system using the same, and more particularly, to a driving system of a starting battery and a method of recognizing an off state of an external system using the same, which make it possible to start an engine next time by recognizing the off state of the external system in an overvoltage state according to whether there occurs a difference between values of voltages measured by two ADCs having different positions of ground GND without requiring a current sensor.

TECHNICAL FIELD

The present invention relates to a driving system of a starting battery and a method of recognizing an off state of an external system using the same, and more particularly, to a driving system of a starting battery, which makes it possible to recognize an off state of an external system without providing a current sensor to a battery management system (BMS) of the starting battery, and a method of recognizing an off state of an external system using the same.

BACKGROUND ART

Recently, with increased concern about environmental issues such as global warming, the necessity and request for reducing carbon dioxide emission, which is one of the main causes of environmental issues, have increased. Therefore, the demand for electric vehicles or electric two-wheeled vehicles which are driven with electricity is increasing.

Meanwhile, a starting battery is a battery for starting an engine, and is configured to be charged by an engine after the engine is started. Such a starting battery is mounted in an electric vehicle or electric two-wheeled vehicle to enable engine start, and is charged by an engine after the engine is started.

Here, when an engine is in an unregulated status, the problem of charging a starting battery up to a safety voltage or higher occurs. When a starting battery including lithium ion cells is charged to a safety voltage or higher, a dangerous situation such as explosion may occur. Thus, it is necessary to control so as to prevent a starting battery from being charged to a safety voltage or higher using a battery management system (BMS).

To this end, in general, the BMS is provided with a current sensor, and accurately recognizes a charging/discharging state through the magnitude and direction of a current using the current sensor to control a starting battery so as to prevent the starting battery from being charged to a safety voltage or higher. However, providing the current sensor to the BMS increases the cost, and thus such BMS may degrade price competitiveness.

DISCLOSURE OF THE INVENTION

Technical Problem

The present invention, which is intended to solve the above-described problem, provides a driving system of a starting battery and a method of recognizing an off state of an external system using the same, which are capable of improving price competitiveness by enabling execution of a function of a battery management system (BMS) without requiring a current sensor.

Technical Solution

A driving system of a starting battery according to the present invention includes: one or more battery cells; a voltage measurement unit, which measures a voltage of the battery cells; an overvoltage determination unit, which compares the voltage measured by the voltage measurement unit with a preset reference voltage to determine whether the battery cells are in an overvoltage state according to a result of comparison; a charging FET, which is configured in a first path that is a main path through which a charging current flow between the battery cells and an external system to control a flow of the charging current; first and second current limiting units, which are configured in a second path through which the charging current flows from the external system to the battery cells and which is formed in parallel with the first path to consume the charging current of the battery cells; a system off determination unit, which determines an off state of the external system to which the battery cells are connected on the basis of a change in a value of the voltage measured by the voltage measurement unit; and a charging FET control unit, which controls on/off of the charging FET configured in the first path according to determination results from the overvoltage determination unit and the system off determination unit.

Here, the voltage measurement unit includes a first voltage measurement unit and a second voltage measurement unit, and grounds GND of the first voltage measurement unit and the second voltage measurement unit are set in different positions.

In detail, the ground GND of the first voltage measurement unit is positioned in the first path, and the ground GND of the second voltage measurement unit is positioned between the first and second current limiting units configured in the second path.

Meanwhile, the overvoltage determination unit determines that the battery cells are in the overvoltage state when a voltage measured by the first voltage measurement unit exceeds the preset reference voltage, and outputs an overvoltage determination signal to the charging FET control unit, and the charging FET control unit turns off the charging FET upon receiving the overvoltage determination signal from the overvoltage determination unit.

Accordingly, when the charging FET is turned off by the charging FET control unit, the charging current that was flowing to the battery cells through the first path flows through the second path.

Meanwhile, the first and second current limiting units configured in the second path consume the charging current flowing through the second path to prevent the battery cells from being overcharged.

Accordingly, when the charging current of the battery cells flows through the second path, the first and second current limiting units cause occurrence of a difference between values of voltages respectively measured by the first and second voltage measurement units.

Meanwhile, the system off determination unit includes: an overvoltage state recognition unit, which recognizes the overvoltage state of the battery cells by detecting that the overvoltage determination signal is output from the overvoltage determination unit, and outputs an overvoltage state signal; and a voltage difference detection unit, which detects, when it is recognized that the battery cells are in the overvoltage state on the basis of the overvoltage state signal output from the overvoltage state recognition unit, whether a difference occurs between the values of the voltages respectively measured by the first and second voltage measurement units to determine an off state of the external system.

In detail, the voltage difference detection unit determines that the external system is in an off state when it is detected that the voltages respectively measured by the first and second voltage measurement units have changed to a state in which there occurs no difference between the voltages, and outputs a system off signal to the charging FET control unit.

Accordingly, the charging FET control unit turns on the charging FET upon receiving the system off signal from the voltage difference detection unit.

Meanwhile, each of the first and second current limiting units is configured with a bypass resistor.

A method of recognizing an off state of an external system in an overvoltage state of battery cells in a driving system of a starting battery as described above includes: a voltage measurement step in which the first and second voltage measurement units measure a voltage of each of the battery cells; an overvoltage determination step in which the overvoltage determination unit compares the voltage measured by the first voltage measurement unit through the voltage measurement step with a preset reference voltage to determine whether the measured voltage exceeds the preset reference voltage to determine whether the battery cells are in the overvoltage state according to a result of comparison; a charging FET off control step in which, when the battery cells are determined to be in the overvoltage state through the overvoltage determination step, the charging FET control unit turns off the charging FET configured in the first path to control the charging current flowing from the external system to the battery cells; a voltage value sameness detection step in which the system off determination unit detects whether the voltages respectively measured by the first and second voltage measurement units have the same value when the charging FET configured in the first path is turned off through the charging FET off control step; a system off determination step in which, when it is detected that the voltages respectively measured by the first and second voltage measurement units have the same value in the voltage value sameness detection step, it is determined that the external system is in the off state; and a charging FET on control step in which, when it is determined that the external system is in the off state in the system off determination step, the charging FET control unit turns on the charging FET configured in the first path.

Here, in the charging FET off control step, when the charging current flows through the second path since the charging FET configured in the first path is turned off, the values of the voltages respectively measured by the first and second voltage measurement units are different from each other due to the first and second current limiting units provided in the second path.

Advantageous Effects

According to the present invention, an off state of a system can be recognized in an overvoltage state of a battery without providing a current sensor to a battery management system (BMS), and thus the price competitiveness of a battery can be improved.

Furthermore, a battery can be stably operated since a control can be performed so as to enable next start by recognizing an off state of system in an overvoltage state of the battery.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily carry out the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. Some parts of the embodiments, which are not related to the description, are not illustrated in the drawings in order to clearly describe the embodiments of the present invention. Like reference numerals refer to like elements throughout the description.

The term “first”, “second” or the like may be used for describing various elements but does not limit the elements. Such terms are only used for distinguishing one element from other elements. For example, without departing the scope of the present invention, a first element may be referred to as a second element, and likewise, a second element may be referred to as a first element. The terminology used herein is not for delimiting the present invention but for describing specific embodiments. The terms of a singular form may include plural forms unless otherwise specified.

In the entire description, when one part is referred to as being “connected” to another part, the former may be “directly connected” to the latter or “electrically connected” thereto via an intervening other part. When it is mentioned that a certain part “includes” or “comprises” certain elements, the part may further include other elements, unless otherwise specified. The term “step (ing) . . . ” or “step of . . . ” used herein does not represent “step for . . . ”.

The terms used herein have been selected from among general terms that are widely used at the present time in consideration of the functions of the present invention, but may be changed depending on intentions of those skilled in the art, judicial precedents, or the advent of new technology. Furthermore, specific terms have been arbitrarily selected by the applicant, and the meanings of such terms will be described in detail in relevant sections of the description. Therefore, it should be understood that the terms used herein should not be simply defined literally but should be defined on the basis of the meanings of the terms and the overall contents of the present disclosure.

1. Driving System of a Starting Battery According to the Present Invention

The present invention includes one or more battery cells100connected in series or in parallel. The battery cells100supply a charging current for starting an engine of an electric vehicle or an electric two-wheeled vehicle, and are charged by the engine after the starting.

The voltage measurement unit, which measures voltage of the battery cells100, may include a first voltage measurement unit200aand a second voltage measurement unit200b. Here, as shown inFIG. 2, the first voltage measurement unit200aand the second voltage measurement unit200bmay measure the same voltage, but grounds GND thereof may be connected to different positions.

Here, each of the first and second voltage measurement units200aand200bmay be an analog-to-digital converter (ADC).

In detail, the ground GND of the first voltage measurement unit200amay be connected to a cell ground GND, and the ground GND of the second voltage measurement unit200bmay be connected between first and second current limiting units500aand500bincluding bypass resistors described below. The grounds GND of the first voltage measurement unit200aand the second voltage measurement unit200bare connected to different positions in order to recognize an off state of an external system in an overvoltage state of the battery cells100according to whether a voltage difference between the first and second voltage measurement units200aand200boccurs through this connection. Relevant detailed description will be provided when describing the system off determination unit700described below.

The overvoltage determination unit compares the voltage of the battery cells100measured by the voltage measurement unit200with a preset reference voltage to determine whether the battery cells100are in an overvoltage state according to a result of the comparison.

When the voltage measured by the voltage measurement unit200exceeds the reference voltage as a result of the comparison, the overvoltage determination unit may determine that the battery cells100are in an overvoltage state, and may output a determination result to a charging FET control unit600and an overvoltage state recognition unit710described below.

Here, it may be preferable that the overvoltage determination unit uses a voltage measured by the first voltage measurement unit200ato determine an overvoltage state of the battery cells100. Values of the voltages respectively measured by the first and second voltage measurement units200aand200bhaving different positions of ground GND are different when a charging current flows through a second path since the charging FET400is turned off due to overvoltage determination. Thus, it may be preferable that the voltage measured by the first voltage measurement unit200ais used to determine a voltage state of the battery cells100considering that a normal state is determined after determining an overvoltage state although the values of the voltages respectively measured by the first and second voltage measurement units200aand200bare the same before determining an overvoltage state.

The charging FET controls a flow of charging current from an engine of an external system such as an electric vehicle or an electric two-wheeled vehicle to the battery cells100or from the battery cells100to the external system, and may be controlled to be turned on/off by a charging FET control unit600described below.

The present invention is a starting battery for supplying power for starting an engine of an external system such as an electric vehicle or an electric two-wheeled vehicle. Thus, a charging current flows from the battery cells100to the external system so that the charging current for starting the engine flows as illustrated inFIG. 3when starting the engine, and, after starting the engine, the charging current flows from the external system to the battery cells100as illustrated inFIG. 4so that the battery cells100may be charged by the engine.

Here, the charging FET may be configured in a first path that is a main charging path as shown inFIG. 2, and may be turned on/off by the charging FET control unit600described below so as to control a flow of the charging current.

The current limiting unit may include first and second current limiting units500aand500b. As shown inFIG. 2, the current limiting unit may be configured in the second path that is different from the first path in which the charging FET400is configured, so as to consume a charging current of the battery cells100to thereby prevent the battery cells100from being overcharged.

In detail, the second path in which the first and second current limiting units500aand500bare configured is formed in parallel with the first path that is the main path through which a charging current flows from an external system to the battery cells100, so as to allow the charging current to flow when the charging FET400configured in the first path is turned off. When the overvoltage determination unit300determines that the battery cells100have an overvoltage, the charging current flows through the second path when the charging FET400is turned off by the charging FET control unit600described below. Here, the charging current flowing through the battery cells100are consumed by the first and second current limiting units500aand500bconfigured in the second path so that the battery cells100may be prevented from being overcharged. Here, the first and second current limiting units500aand500bare configured with bypass resistors. That is, since the first and second current limiting units500aand500bincluding bypass resistors consume the charging current of the battery cells100by as much as corresponding resistor values, the battery cells100may be prevented from being overcharged.

In brief, the first path is the main path through which a charging current flows, and the second path is a path through which the charging current flows when the charging FET400configured in the first path is turned off, wherein the first and second current limiting units500aand500bincluding bypass resistors are configured in the second path to consume the charging current of the battery cells100to thereby prevent the battery cells100from being overcharged.

Here, the ground GND of the second voltage measurement unit200aof the voltage measurement unit200described above may be described as being positioned between the first and second current limiting units500aand500bincluding bypass resistors.

As described above, the charging FET control unit may control on/off of the charging FET400according to a determination result from the overvoltage determination unit300.

As described above, when an overvoltage determination signal is output from the overvoltage determination unit300, the charging FET control unit may recognize that the battery cells100are in an overvoltage state, and may turn off the charging FET400in order to block the charging current flowing from an external system to the first path.

On the contrary, in a state in which the overvoltage determination signal is not output from the overvoltage determination unit300, i.e., in a normal state, the charging FET400may be turned on so as to allow the charging current from an external system to flow through the first path that is the main path.

Furthermore, when a system off signal is output from the system off determination unit700described below, the charging FET control unit may turn on the charging FET400.

The system off signal output from the system off determination unit700indicates that an external system is turned off in a state in which the charging FET400is turned off due to determination of an overcharge state of the battery cells100, and thus the charging FET400may be turned on again. Accordingly, the charging current may be allowed to flow from the battery cells100to an engine of an external system to enable engine start when starting the engine next time.

Relevant detailed description will be provided in relation to the system off determination unit700described below.

1.7. System Off Determination Unit700

In a state in which the overvoltage determination unit300has determined that the battery cells100are in an overvoltage state, the system off determination unit detects whether there is a difference between the voltages respectively measured by the first and second voltage measurement units200aand200bof the voltage measurement unit200, and determines that an external system is in an off state according to a result of the detection. The system off determination unit may include specific elements as below.

The overvoltage state recognition unit may recognize an output of the overvoltage determination signal from the overvoltage determination unit300to recognize an overvoltage state of the battery cells100. When the overvoltage determination signal is output from the overvoltage determination unit300, the overvoltage state recognition unit may determine that the battery cells100are in an overvoltage state, and may output an overvoltage state signal.

In a state in which the overvoltage state recognition unit710has recognized that the battery cells100are in an overvoltage state, the voltage difference detection unit detects whether there occurs a difference between the voltages respectively measured by the first and second voltage measurement units200aand200bof the voltage measurement unit200.

In detail, the voltage difference detection unit may receive the overvoltage state signal output from the overvoltage state recognition unit710. Upon receiving the overvoltage state signal, the voltage difference detection unit compares the values of the voltages respectively measured by the first and second voltage measurement units200aand200bof the voltage measurement unit200after elapse of a predetermined time from the time of the input of the overvoltage state signal so as to detect whether there occurs a difference between the two voltages. When no difference is detected between the voltages of the first and second voltage measurement units200aand200bas a result of the comparison, the voltage difference detection unit may determine that an external system is turned off in an overvoltage state of the battery cells100, and may output the system off signal to the charging FET control unit600. Accordingly, the charging FET control unit600that has received the system off signal turns on the charging FET400so as to enable engine start by allowing a charging current to flow from the battery cells100to an engine when turning on power of an external system next time.

Here, the voltage difference detection unit detects whether there occurs a difference between the voltages of the first and second voltage measurement units200aand200bafter elapse of the predetermined time from the time of the input of the overvoltage state signal, considering the time taken for the values of the voltages respectively measured by the first and second voltage measurement units200aand200bto become different since the charging current that was flowing through the first path flows through the second path when the charging FET400is turned off due to determination of an overcharge state. Accordingly, the voltage difference detection unit may more accurately detect a state in which the values of the voltages of the first and second voltage measurement units200aand200bbecome equal, i.e., there occurs no difference therebetween, and thus may accurately determine that a system has been turned off in an overvoltage state.

Here, the fact that the external system has been turned off may indicate that an electric vehicle or an electric two-wheeled vehicle is in a turned off state, and enabling the power of the external system to be turned on may indicate that next start is enabled in a turned off state.

That is, the present invention relates to a starting battery, which is mounted in an external system such as an electric vehicle or an electric two-wheeled vehicle to supply power for starting an engine, and is charged by the engine after the engine is started. Here, when the external system is turned off (ignition off) in a state in which the charging FET400is turned off, it is necessary to turn on the FET400again to enable engine start next time. Therefore, when no difference is detected between the values of the voltages measured by the first and second voltage measurement units200aand200bof the voltage measurement unit200in an overvoltage state of the battery cells100, i.e., in a state in which the charging FET400is turned off, the system off determination unit700determines that an external system is turned off, and outputs the system off signal to the charging FET control unit600to turn on the charging FET400so as to enable next start.

The principle of determining, as a turned off state of an external system, the state in which the first and second voltage measurement units200aand200bmeasure the same voltage value in an overvoltage state of the battery cells100, as described above, will be described.

First, after an engine of an external system is started by supplying a charging current from the battery cells100to the engine via the charging FET400that is turned on in the first path as illustrated inFIG. 3, the charging current may be supplied from the engine to the battery cells100so that the battery cells100may be charged as illustrated inFIG. 4. In the states ofFIGS. 3 and 4, the charging current flows through the first path that is the main path, and thus the flowing charging current is hardly limited by resistor, and the first and second voltage measurement units200aand200bmeasure the same voltage value. In this state, when the charging FET400is turned off since the overvoltage determination unit300determines that an overvoltage state has occurred, the charging current that was flowing through the first path flows through the second path in which the first and second current limiting units500aand500bincluding bypass resistors are configured as illustrated inFIG. 5in order to prevent the battery cells100from being overcharged. When the charging current flows through only the second path as described above, a voltage is loaded on the first and second current limiting units500aand500bwhile the charging current is flowing therethrough, and is reversed to +, −, causing a floating phenomenon of the ground GND, since the ground GND of the first voltage measurement unit200ais the cell ground GND, but the ground GND of the second voltage measurement unit200bis positioned between the first and second current limiting units500aand500b. Accordingly, as illustrated inFIG. 6, although the first ADC200aand the second ADC200bactually measure the same voltage, the ground GND of the second ADC200bis floated, and a reference changes as much as the degree to which the second ADC200bis floated, thus causing a difference from the value of the voltage read by the first voltage measurement unit200a. As a result, there occurs a difference between the values of the voltages of the first and second voltage measurement units200aand200b.

Therefore, in a state in which the charging current flows through the first path as illustrated inFIGS. 3 and 4, the values of the voltages measured by the first and second voltage measurement units200aand200bare the same, and in a state in which the charging current flows through the second path since the charging FET400is turned off as illustrated inFIG. 5, i.e., in an overvoltage state, the ground GND of the second voltage measurement unit200bis floated by the first and second current limiting units500aand500bconfigured in the second path, and thus there occurs a difference between the values of the voltages measured by the first and second voltage measurement units200aand200b.

Here, since a current changes according to an output of the external system, the voltage loaded on the first and second current limiting units500aand500balso changes, and thus the degree to which the ground GND of the second voltage measurement unit200bis floated may vary.

When the external system is turned off in the state illustrated inFIG. 5, there occurs no difference between the values of the voltages measured by the first and second voltage measurement units200aand200bsince no current flows.

Therefore, the present invention may use the above-described principle to determine that the external system is turned off by detecting that the voltages of the first and second voltage measurement units200aand200bare equal without having a difference in an overvoltage state.

Here, the state in which the external system is turned off may represent a state in which an engine is turned off.

In this manner, the present invention may recognize, without having a current sensor, the state in which the external system is turned off in an overvoltage state according to whether there occurs a difference between the values of the voltages measured by the first and second voltage measurement units200aand200bby providing a path in which the first and second current limiting units500aand500bincluding bypass resistors are configured and by connecting the grounds GND of the first and second voltage measurement units200aand200bto different positions, and thus enables a following control that enables next engine start, thereby improving price competitiveness and efficiency.

Here, it may be necessary to design such that distributed resistance (a, b, c, d) values of the first and second voltage measurement units200aand200band resistance values of the first and second current limiting units500aand500bhave a sufficiently large difference. The reason is that the voltages measured by the first and second voltage measurement units200aand200bare required to have almost the same value to use the above-described principle, but the unit of distributed resistance of each voltage measurement unit is 10 to the power of 6 ohms, and the first and second current limiting units500aand500b, which are bypass resistors, have the unit of 10 to the power of 0 ohms, and thus there is a ten thousand times difference therebetween. Therefore, in order to make it possible to recognize a system off state in an overvoltage state using the above-described principle, it is necessary to design, in consideration of the above issue, such that the distributed resistance (a, b, c, d) values of the voltage measurement units, each of which is configured with an ADC, and the resistance values of the first and second current limiting units500aand500bhave a sufficiently large difference.

2. Method of Recognizing an Off State of an External System Using a Driving System of a Starting Battery According to the Present Invention

Referring toFIG. 7, the method of recognizing an off state of an external system according to the present invention may include the following steps.

The voltage measurement step, which is a step of measuring the voltage of the battery cells100, may be performed by the first and second voltage measurement units200aand200b, each of which is configured with an ADC.

The overvoltage determination step is a step of comparing the voltage measured in the voltage measurement step S100with a preset reference voltage to determine whether the battery cells100are in an overvoltage state according to a result of the comparison. When the voltage measured in the voltage measurement step S100exceeds the preset reference voltage, the battery cells100may be determined to be in an overvoltage state, and an overvoltage state signal may be output.

This overvoltage determination step may be performed by the above-described overvoltage determination unit300.

2.3. Charging FET Off Control Step S300

In this step, the charging FET400configured in a first path that is a main charging path is controlled to be turned off in order to block a charging current flowing from an external system such as an electric vehicle or an electric two-wheeled vehicle to the battery cells100via the first path when the overvoltage determination signal is output since the battery cells100are determined to be in an overvoltage state in the overvoltage determination step S200. Overcharging may be prevented through this step since the charging current that was flowing from the external system to the battery cells100via the first path as illustrated inFIG. 4flows through a second path in which the first and second current limiting units500aand500bincluding bypass resistors are configured as illustrated inFIG. 5so that the current is limited by the first and second current limiting units500aand500b, thus reducing the charging current of the battery cells100.

This charging FET off control step may be performed by the charging FET control unit600that has received the overvoltage determination signal from the overvoltage determination unit300.

2.4. Voltage Value Sameness Detection Step S400

In the voltage value sameness detection step, when the charging current flowing from the external system to the battery cells100flows through the second path in which the first and second current limiting units500aand500bare configured through the charging FET off control step S300, the values of the voltages respectively measured by the first and second voltage measurement units200aand200bthrough the voltage measurement step S100are compared to detect whether the two voltages are in the same state.

As described above, when the charging FET400configured in the first path is blocked through the charging FET off control step S300, the charging current flows through the second path in which the first and second current limiting units500aand500bare configured as illustrated inFIG. 5. Here, since the first voltage measurement unit200ahas the cell ground GND, and the ground GND of the second voltage measurement unit200bis positioned between the first and second current limiting units500aand500b, when the charging current flows through the second path as illustrated inFIG. 5, the ground GND of the second voltage measurement unit200bis floated by the first and second current limiting units500aand500b, causing occurrence of a difference between the values of the voltages respectively measured by the first and second voltage measurement units200aand200b. When the external system is turned off in this state, i.e., when an engine is turned off, no current flows, and thus the values of the voltages of the first and second voltage measurement units200aand200bbecome the same.

Therefore, the values of the voltages measured by the first and second voltage measurement units200aand200bare different in the charging FET off control step S300, and in this state, it is detected that no difference occurs between the two voltages through the voltage difference detection step. Since this principle has been described in relation to a system configuration, detailed description is omitted.

This voltage sameness detection step may be performed by the above-described system off determination unit700.

2.5. System Off Determination Step S500

In this step, a state in which the system is turned off is determined according to a result of the voltage difference detection in the voltage value sameness detection step S400. When it is detected that the voltages measured by the first and second voltage measurement units200aand200bhave the same value through the voltage value sameness detection step S400, it may be determined that the system is in a turned off state. Since this state indicates that the system is turned off in an overvoltage state in which the charging FET400configured in the first path is turned off through the charging FET off control step S300, it is necessary to turn on the turned-off charging FET400in order to supply the charging current from the battery cells100to the external system for starting the engine next time. Therefore, in the system off determination step performed by the above-described system off determination unit700, when it is determined that the system is turned off, a system off signal may be output to the charging FET control unit600so that the charging FET on control step S600described below may be performed.

2.6. Charging FET on Control Step S600

In the charging FET on control step, the charging FET control unit600that has received the system off signal from the system off determination unit700since the system was determined to be turned off in the system off determination step S500turns on the turned-off charging FET400configured in the first path.

Since the charging FET400is turned on through the charging FET on control step, the charging current may be supplied from the battery cells100to the external system via the first path to enable engine start when starting the engine next time.

Through the steps as described above, the present invention may recognize a state in which the external system is turned off in an overvoltage state of a battery, i.e., may recognize a state in which the engine is turned off without having a current sensor as in the prior art, thereby enabling a control that enables next engine start. Thus, the effect of reducing the cost caused by providing a current sensor may be bring about, thereby improving the price competitiveness.

Although the technical concept of the present invention has been specifically described according to the above-mentioned embodiment, it should be noted that the above-mentioned embodiment is not for limiting the present invention but for describing the present invention. Furthermore, those skilled in the art could understand that various embodiments can be made within the scope of the technical concept of the present invention.