KR102637310B1 - Battery cell deterioration diagnosis method and battery pack using the same - Google Patents

Abstract

The present invention relates to a method for diagnosing the deterioration state of a battery cell and a battery pack using the same. More specifically, the present invention relates to a method for diagnosing the deterioration state of a battery cell and a battery pack using the same. More specifically, the present invention relates to a method for diagnosing the deterioration state of a battery cell and a battery pack using the same. It relates to a method of diagnosing the deterioration state of a battery cell by forming a constant current flow and calculating the corresponding resistance value by measuring the voltage drop, and a battery pack using the same.

Description

Battery cell deterioration diagnosis method and battery pack using the same {Battery cell deterioration diagnosis method and battery pack using the same}

The present invention relates to a method for diagnosing the deterioration state of a battery cell and a battery pack using the same. More specifically, the present invention relates to a method for diagnosing the deterioration state of a battery cell using a cell balancing circuit without charge/discharging operation and a battery pack using the same. will be.

Rechargeable secondary batteries (hereinafter referred to as ‘batteries’) are used as an energy source in various fields, including portable electronic devices such as smartphones, laptops, and PDAs, as well as electric vehicles and energy storage systems (ESS). The longer the continuous use period is, the more the battery deteriorates with repeated charging/discharging, which causes the capacity/performance of the battery to gradually deteriorate. Deterioration in the capacity/performance of the battery due to these characteristics affects the stable operation of the system using the battery.

Therefore, accurately identifying the deterioration state of the battery makes it possible to estimate when the battery needs to be replaced and manages the battery more efficiently. Additionally, this can minimize negative impacts that may occur due to reduced battery capacity/performance.

Meanwhile, in the past, a method was used to measure battery capacity through fully charging and discharging the battery and compare this with the initial battery capacity to determine the degree of battery deterioration. However, this is not efficient because the battery must be fully charged and then fully discharged, and there is a problem in that it is difficult to determine the degree of deterioration of all cells of the battery. Additionally, there is a method to determine the degree of battery deterioration by measuring the impedance of the battery, but this method requires a separate circuit, so it is not efficient.

As such, conventional methods generally measure voltage and current when a battery is charged/discharged, and can determine the degree of battery deterioration using a resistance value calculated from the measured voltage and current values. However, since this method requires charging/discharging of the battery, there is a problem in that the charging/discharging of the battery also acts as a factor in deteriorating the battery.

(Patent Document 1) KR10-1558696 B1

The present invention is intended to solve the above-mentioned problems, and seeks to provide a method for diagnosing the deterioration state of a cell without charging/discharging the battery and a battery pack using the same.

The method for diagnosing the deterioration state of a battery cell according to the present invention includes a detection signal output step of detecting a state in which there is no charging or discharging operation of the battery cell and outputting a detection signal; A first voltage measurement step of measuring the first voltage of the battery cell as the detection signal is output through the detection signal output step; After the first voltage measurement step, a current flow forming step of flowing a balancing current to a cell balancing circuit connected to the battery cell; A second voltage measurement step of measuring a second voltage of the battery cell in a state in which a balancing current flows through the current flow forming step; A cell voltage deviation calculation step of calculating a difference between the first voltage and the second voltage of the measured battery cell; A cell resistance value calculation step of calculating a resistance value of the battery cell using the cell voltage difference calculated through the cell voltage difference calculation step; A cell deterioration state diagnosis step of diagnosing the deterioration state by calculating the degree of deterioration of the corresponding cell according to the cell resistance value calculated in the cell resistance value calculation step; It is composed including.

At this time, in the second voltage measurement step, measuring the second voltage is characterized by measuring the second voltage a predetermined time after the balancing current begins to flow in the battery cell through the current flow forming step. Do it as

Meanwhile, the current flow forming step includes a balancing FET turn-on control step of controlling the turn-on of the balancing FET of the cell balancing circuit corresponding to the battery cell; It is configured to include, and is characterized in that balancing current is formed through the turned-on balancing FET.

Meanwhile, the cell degradation state diagnosis step detects the resistance section to which the cell resistance value calculated in the cell resistance value calculation step belongs based on a pre-prepared cell degradation degree table, and the degradation degree corresponding to the detected resistance section. It is characterized by extracting and diagnosing the deterioration state of the corresponding battery cell.

Here, the cell deterioration table is characterized in that it includes deterioration data according to the cell resistance value, which is a standard for diagnosing the cell deterioration state.

A battery pack for diagnosing the deterioration state of a battery cell according to the present invention includes one or more battery cells; a voltage measuring unit that measures the voltage of the battery cell; A charging/discharging operation detection unit that detects a state in which there is no charging or discharging operation of the battery cell and outputs a detection signal; A cell balancing unit that generates balancing current in the battery cells; a control unit that controls the voltage measurement unit and the cell balancing unit depending on whether a detection signal is output from the charge/discharge operation detection unit; a cell resistance value calculation unit that calculates the resistance value of the battery cell using the voltage of the battery cell measured under the control of the control unit; a storage unit that stores degradation degree data according to the cell resistance value, which is a standard for diagnosing the cell degradation state; a deterioration state diagnosis unit that diagnoses the deterioration state of the cell using the resistance value of the battery cell calculated by the cell resistance value calculation unit, based on the deterioration degree data according to the cell resistance value stored in the storage unit; It is composed including.

Here, the cell balancing unit includes a balancing FET that controls current flow; and a balancing resistor that limits the amount of current flowing through the balancing FET. It is configured to include, and is characterized in that a balancing current having a certain size is formed in the corresponding battery cell through the balancing FET and the balancing resistor.

Meanwhile, the control unit includes a detection signal receiver that receives a detection signal output from the charging/discharging operation detection unit; a voltage measurement control unit that outputs a voltage measurement signal that controls a voltage measurement operation to the voltage measurement unit, depending on whether the detection signal is received by the detection signal receiver; A current formation control unit that outputs a balancing FET turn-on signal to the balancing FET of the cell balancing unit in accordance with the output of the voltage measurement signal from the voltage measurement control unit to control the formation of a balancing current in the corresponding battery cell; It is characterized by being composed of a.

Specifically, as the detection signal receiver receives the detection signal, the voltage measurement control unit outputs a first voltage measurement signal to the voltage measurement unit to measure the voltage in a state in which there is no charging or discharging operation of the corresponding battery cell. , As the current formation control unit outputs a balancing turn-on signal to the balancing FET of the corresponding cell balancing unit, a second voltage measurement signal is output to the voltage measuring unit to measure the voltage in a state in which a balancing current is formed in the corresponding battery cell. It is characterized by

Accordingly, the voltage measurement unit is characterized in that it measures the first voltage of the battery cell as it receives the first voltage measurement signal from the voltage measurement control unit of the control unit, and measures the second voltage from the voltage measurement control unit of the control unit. As the signal is received, the second voltage of the corresponding battery cell is measured.

Meanwhile, the cell resistance value calculation unit includes a cell voltage difference calculation unit that calculates a difference between the first voltage and the second voltage of the corresponding battery cell measured by the voltage measurement unit; Characterized in that it is configured to include, and the resistance value of the corresponding battery cell is calculated using the cell voltage deviation value calculated by the cell voltage deviation calculation unit and the value of the balancing current.

Accordingly, the deterioration state diagnosis unit detects a resistance section to which the resistance value of the battery cell calculated by the cell resistance value calculation unit belongs based on the deterioration degree data according to the cell resistance value stored in the storage unit, and the detected It is characterized by diagnosing the deterioration state of the corresponding battery cell by extracting the degree of deterioration corresponding to the resistance section.

Meanwhile, the output of the second voltage measurement signal from the voltage measurement unit is characterized in that it is performed a predetermined time after detecting the output of the balancing FET turn-on signal of the current formation control unit.

The present invention is more efficient because it can diagnose the deterioration state of a cell without charging/discharging the battery, and does not require a separate circuit in that it utilizes a cell balancing circuit pre-configured in the battery pack to make the diagnosis. Therefore, it is also cost-effective.

1 is a block diagram schematically showing a method for diagnosing a deterioration state of a battery cell according to an embodiment of the present invention.
Figure 2 is an example of a cell deterioration table prepared through experiment.
Figure 3 is a block diagram schematically showing the configuration of a battery pack for diagnosing a deterioration state of a battery cell according to an embodiment of the present invention.

Below, embodiments of the present invention will be described in detail with reference to the attached drawings. The present invention may be implemented in many different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts not related to the description are omitted, and similar parts are given similar reference numerals throughout the specification.

Terms containing ordinal numbers, such as first, second, etc., may be used to describe various components, but the components are not limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, a first component may be named a second component without departing from the scope of the present invention, and similarly, the second component may also be named a first component. The terms used in this application are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

Throughout the specification, when a part is said to be “connected” to another part, this includes not only cases where it is “directly connected,” but also cases where it is “electrically connected” with another element in between. . Additionally, when a part is said to “include” a certain component, this does not mean excluding other components, but may include other components, unless specifically stated to the contrary. The term “step of” or “step of” as used throughout the specification does not mean “step for.”

The terms used in the present invention are general terms that are currently widely used as much as possible while considering the function in the present invention, but this may vary depending on the intention or precedent of a person working in the art, the emergence of new technology, etc. In addition, in certain cases, there are terms arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the description of the relevant invention. Therefore, the terms used in the present invention should be defined based on the meaning of the term and the overall content of the present invention, rather than simply the name of the term.

Before explaining the present invention in detail, the terms used in the present invention will be explained.

1. Overview

1.1. 1st voltage / 2nd voltage

The first voltage is a term referring to the voltage of the battery cell measured in the absence of charging and discharging operations.

The second voltage is a term that refers to the voltage of the battery cell that is measured by temporarily forming a current flow in the battery cell using a cell balancing circuit in a state where there is no charging or discharging operation.

In other words, the first voltage and second voltage of the battery cell can be explained as voltages measured before and after forming a current flow in the battery cell using a cell balancing circuit in the absence of charging and discharging operations. there is.

The present invention provides a voltage between the voltage when there is no current flow in the battery cell using a cell balancing circuit (first voltage) and the voltage when there is current flow (second voltage) in a state in which there is no charging and discharging operation of the battery cell. Since the degree of deterioration is measured by calculating the resistance value of the corresponding cell using the degree of voltage drop, the first and second voltages for the battery cell are respectively measured and utilized as described above.

1.2. balancing current

In the present invention, balancing current refers to a current flow temporarily formed in a battery cell using the cell balancing circuit described above. In general, the current flowing in the cell balancing circuit always has a constant size because the balancing resistor included in the cell balancing circuit limits the current. The present invention takes advantage of this to form a constant current flow in the battery cell in a state where there is no charging or discharging operation of the battery cell, and uses the resistance value calculated by measuring the voltage drop of the battery cell accordingly to The purpose is to diagnose the deterioration state of .

Hereinafter, the present invention will be described in detail with reference to the drawings.

2. Cell deterioration diagnosis method according to the present invention

1 is a flowchart showing a method for diagnosing a deterioration state of a battery cell according to an embodiment of the present invention. Referring to Figure 1, the cell deterioration diagnosis method according to the present invention includes a detection signal output step (S100), a first voltage measurement step (S200), a current flow forming step (S300), a second voltage measurement step (S400), It includes a cell voltage deviation calculation step (S500), a cell resistance value calculation step (S600), and a cell deterioration degree calculation step (S700).

2.1 Detection signal output stage (S100)

The detection signal output step (S100) is a step of detecting a state in which there is no charging or discharging operation of the battery cell and outputting a detection signal. It is possible to determine whether the battery cell is in a state of charging by a charger or discharging by a load, and if there is neither charging nor discharging, this can be detected and a detection signal can be output.

The method of determining whether there is a charging or discharging operation can be determined, for example, through the direction of current in the battery cell, or by detecting the voltage between the (+) and (-) output terminals of the battery cell. there is. Determining whether a battery cell is in a charged or discharged state is determined using a known technique, through which it is possible to detect that there is no charging or discharging operation in the battery cell and output a detection signal.

The detection signal output step of detecting a state in which there is no charging or discharging operation of the battery cell and outputting a detection signal is performed by the charging and discharging operation detection unit 130, which will be described later.

2.2. First voltage measurement step (S200)

The first voltage measurement step is performed after a detection signal detecting a state in which there is no charging or discharging operation of the battery cell is output through the detection signal output step (S100). In this step, the charging/discharging operation detection unit 130, which will be described later, configured in the battery pack, detects a state in which there is no charging or discharging operation of the battery cell and outputs a detection signal, so that the voltage measurement control unit 154 of the control unit 150 This is a step of measuring the voltage of the battery cell in the voltage measurement unit 120 that receives the first voltage measurement signal output from ). In other words, the first voltage measurement step is performed when the voltage measurement unit 120 receives the first voltage measurement signal from the voltage measurement control unit 154 of the control unit 150, and is performed in a state in which there is no charging or discharging operation. This is the step of measuring the voltage of the battery cell.

The voltage of the battery cell in a state in which there is no charging or discharging operation measured in the first voltage measurement step is referred to as the first voltage.

2.3. Current flow formation step (S300)

In the current flow forming step, the voltage (first voltage) of the battery cell is measured in a state without charging and discharging operation through the first voltage measuring step (S200), and then the current flows to the battery cell through the cell balancing circuit. This is the stage that forms. Current flow can be created in battery cells that are not in charge or discharge operations using a cell balancing circuit that is generally included in a battery pack.

Specifically, the cell balancing circuit (cell balancing unit, 140), which is generally pre-configured in the battery pack, includes a balancing FET 142 and a balancing resistor 144. At this time, the balancing circuit configured in the cell balancing circuit As the FET 142 is turned on, the current of the corresponding cell flows through the balancing FET 142 and the balancing resistor 144 configured in the discharge path, and the current is limited by the balancing resistor and has a constant size. The current flow of a certain size formed in this way refers to the balancing current referred to in the present invention. Accordingly, a constant current flow can be formed in the battery cell in a state where there is no charging or discharging operation.

Accordingly, the current flow forming step includes a balancing FET turn-on control step (S310) for controlling the turn-on of the balancing FET 142 of the cell balancing unit 140 of the battery cell, through which balancing By turning on the FET 142, a constant current flow (ideal, balancing current) can be formed into the battery cell through the balancing resistor 144.

2.4. Second voltage measurement step (S400)

The second voltage measurement step is a step of measuring the voltage of the battery cell in a state in which a constant current flow is formed in the battery cell through the current flow forming step (S300).

This step is performed when the voltage measurement unit 120 receives the second voltage measurement signal output from the voltage measurement control unit 154 of the control unit 150. Specifically, when the current formation control unit 156, which will be described later, outputs a balancing FET turn-on signal to the balancing FET 152 of the cell balancing unit 140 to form a constant current flow in the battery cell, the voltage measurement control unit ( 154) may detect this and output a second voltage measurement signal to the voltage measurement unit 120 to measure the voltage of the battery cell in a state where a constant current flow is formed. Accordingly, the voltage measurement unit 120, which receives the second voltage signal from the voltage measurement control unit 154, performs a second voltage measurement step (S400) of measuring the voltage of the battery cell in a state in which a constant current flow is formed. do.

Here, in the second voltage measurement step (S400), after forming a constant current flow to the battery cell through the current flow forming step (S300), the current flow is formed to measure the voltage of the battery cell in that state. It may be configured to be performed a predetermined time after step S300. This detects that when the voltage measurement control unit 154 outputs the second voltage measurement signal to the voltage measurement unit 120, the current generation control unit 156 outputs a balancing FET turn-on signal to the balancing FET 142. By configuring the output to be output after a predetermined time, the second voltage measurement step (S400) can be performed a predetermined time after the current flow forming step (S300).

However, when a constant current flows through the battery cell, the voltage is stabilized, but the voltage of the battery cell continues to drop, which may affect the overall performance of the battery pack. It should be set at an appropriate time taking this into account. The appropriate time may be set differently depending on the specifications of the battery cell.

Meanwhile, as described above, the voltage of the battery cell measured in the second voltage measurement step (S400) is referred to as the second voltage, and the second voltage forms a constant current flow in the absence of charging and discharging operations. It means the voltage measured in the condition that is applied. The second voltage measurement step, like the first voltage measurement step (S200), is performed by the voltage measurement unit 120 under the control of the control unit 150, which will be described later.

2.5. Cell voltage deviation calculation step (S500)

The cell voltage deviation step is the difference between the first voltage (V1) of the battery cell measured in the first voltage measurement step (S200) and the second voltage (V2) of the battery cell measured in the second voltage measurement step (S400). This is the step of calculating the difference (V2-V1). Calculating the difference between the first voltage and the second voltage of the battery cell means measuring the degree of voltage drop when there is and when there is no constant current flow in the battery cell.

2.6. Cell resistance value calculation step (S600)

The cell resistance value calculation step is a step of calculating the resistance value of the battery cell using the voltage deviation value of the battery cell and a predetermined current value calculated in the cell voltage difference calculation step (S500). Here, the predetermined current value is a constant value formed into a battery cell through the balancing resistor 144 by turning on the balancing FET 142 of the cell balancing unit 140 in the current flow forming step (S300) described above. It is the flow of current, that is, the value of balancing current.

Since the size of the balancing current is set according to the value of the balancing resistor 144, it may be set differently depending on the balancing resistor 142 configured in the cell balancing unit 140. Therefore, the balancing current value used to calculate the resistance value of the battery cell at this stage can be set to a constant by the user.

The resistance value is calculated using a general resistance value calculation formula. In other words, the resistance value of the battery cell can be calculated by calculating the cell resistance value = cell voltage deviation / balancing current value.

2.7. Cell deterioration state diagnosis step (S700)

A step of diagnosing the deterioration state of a battery cell using the cell resistance value calculated through the cell resistance value calculation step (S600), wherein the resistance according to the cell deterioration state is prepared in advance through an experiment of measuring the resistance value according to the deterioration of the battery cell. The deterioration state of a cell can be diagnosed based on a table of values (hereinafter referred to as a cell deterioration table).

Through experiment, in the cell degradation table prepared as shown in FIG. 2, the resistance section to which the cell resistance value calculated in the cell resistance value calculation step (S600) belongs is detected, and the degree of degradation corresponding to the detected resistance section is calculated. The deterioration state of the cell can be diagnosed.

For example, if the resistance value of the battery cell calculated through the cell resistance value calculation step (S600) is 20.88mΩ, the resistance section to which the resistance value of the battery cell belongs in the cell deterioration table is Fresh Cell and 1Y. The range between aged cells is 20.42mΩ - 31.59mΩ, and the corresponding degree of deterioration is calculated as 1Y aged cell. Therefore, it can be diagnosed that the battery cell in question has been deteriorated for one year.

For reference, the resistance value depending on the deterioration state of the battery cell may be the same for cells with the same composition, but if the composition is different, the resistance value will vary depending on the deterioration state, so the resistance value depending on the deterioration state of all battery cells cannot be specified. Therefore, when a cell is changed (i.e., when the composition of the cell changes), a cell deterioration table must be prepared through an experiment to measure the resistance value according to the deterioration of the cell.

As such, the present invention forms a constant current flow in the battery cell using a cell balancing circuit in a state in which there is no charging/discharging operation of the battery cell, and measures the corresponding resistance value by measuring the voltage drop of the battery cell accordingly. Depending on the degree of increase, the state of cell deterioration can be diagnosed. Therefore, unlike the conventional method that required a charging/discharging operation to diagnose the deterioration state of the battery cell, this is possible without a charging/discharging operation, allowing the battery cell to be used more efficiently. In addition, it provides improved efficiency in terms of cost by utilizing a cell balancing circuit for cell balancing operation that is generally included in a battery pack without adding a separate circuit.

Hereinafter, a battery pack for diagnosing a cell deterioration state according to an embodiment of the present invention will be described.

3. Battery pack for diagnosing cell deterioration according to the present invention

Figure 3 is a block diagram briefly illustrating the configuration of a battery pack for diagnosing a battery cell deterioration state according to an embodiment of the present invention.

Referring to FIG. 3, the battery pack 100 according to the present invention includes one or more battery cells 110, a voltage measurement unit 120, a charging/discharging operation detection unit 130, a cell balancing unit 140, and a control unit 150. ), a cell resistance value calculation unit 160, a storage unit 170, and a deterioration state diagnosis unit 180.

3.1. Battery Cell(110)

The battery pack 100 of the present invention includes one or more battery cells 110 connected in series or parallel.

3.2. Voltage measurement unit (120)

The voltage measurement unit is a component that measures the voltage of the battery cell. The voltage measuring unit not only measures the voltage of the battery cell at regular periodic intervals, but also measures the voltage of the corresponding battery cell under the control of the control unit 150, which will be described later.

Specifically, the first voltage of the battery cell is measured as the first voltage measurement signal is received from the voltage measurement control unit 154 of the control unit 150, and the second voltage of the battery cell is measured as the second voltage measurement signal is received. can be measured. Here, the first voltage is the voltage of the battery cell measured in a state where there is no charging and discharging operation of the battery cell as described above, and the second voltage is the cell balancing circuit in a state in which there is no charging and discharging operation of the battery cell. This refers to the voltage of the battery cell measured when a constant current flow is formed in the battery cell using the (cell balancing unit, 140). Here, the flow of constant current formed in the battery cell using the cell balancing unit is referred to as balancing current.

In other words, the first voltage is the voltage of the battery cell measured in the absence of the balancing current, and the second voltage is the voltage of the battery cell measured in the presence of the balancing current.

3.3. Charge/discharge motion detection unit (130)

The charging/discharging operation detection unit detects a state in which there is no charging or discharging operation of the battery cell and outputs a detection signal accordingly.

The charging/discharging operation detection unit determines whether the battery cell is in a charging operation by a charger or a discharging operation by a load, and when it is confirmed that there is no charging or discharging operation through this, it detects this and detects the battery cell. A detection signal indicating that there is no charging or discharging operation can be output.

Determining whether a battery cell is in a charging or discharging state may be determined, for example, through the direction of the current in the battery cell, or by detecting the voltage between the (+) and (-) output terminals of the battery cell. You can also judge through it. In addition, in addition to the above-described method, it is possible to determine whether a battery cell is in a charged or discharged state by using a known technique for determining the charging and discharging state, and through this, it is possible to detect that there is no charging or discharging operation of the battery cell. Thus, a detection signal can be output. The charging/discharging motion detection unit performs the above-described detection signal output step (S100).

3.4. Cell balancing unit (140)

The cell balancing unit is generally a cell balancing circuit for compensating for voltage differences occurring between battery cells pre-configured in a battery pack, and in the present invention, it can be used to form a constant current flow (balancing current) in the battery cells. .

As explained in the current flow forming step (S300), the cell balancing unit 140 includes a balancing FET 142 that controls the current flow and a balancing resistor 144 that forms the current flowing through it to a constant size. It is composed by:

The balancing FET 142 of the cell balancing unit 140 is turned on and controlled by the current forming control unit 156 of the control unit 150, which will be described later, and the current flowing through it flows through the balancing resistor 144. Limitation is achieved and a balancing current, which is a current flow of a certain size to the battery cell, can be formed.

In this specification, the cell balancing circuit and cell balancing unit can be used interchangeably.

3.5. Control unit (150)

As the charging/discharging operation detection unit 130 detects that there is no charging or discharging operation of the battery cell, the control unit detects the voltage when there is no current flow in the battery cell and a constant current in order to diagnose the deterioration state of the battery cell. It is a configuration that controls the voltage to be measured when there is a flow, and may be configured to include the following configuration.

go. Detection signal receiver (152)

The detection signal receiver is configured to receive a detection signal output when the charging/discharging operation detecting unit 130 detects that there is no charging or discharging operation of the battery cell. As the detection signal is received by the detection signal receiver, the voltage measurement control unit 154 and the current formation control unit 156, which will be described later, operate to measure the voltage drop of the battery cell according to the current flow.

me. Voltage measurement control unit (154)

As the voltage measurement control unit receives the detection signal from the detection signal receiver 152, it sends a first voltage measurement signal to the voltage measurement unit 120 to measure the voltage of the battery cell in a state where there is no charging or discharging operation. Can be printed. Accordingly, the voltage measurement unit 120 that receives the first voltage measurement signal can measure the first voltage, which is the voltage of the battery cell in a state where there is no charging or discharging operation, as described above.

Meanwhile, the voltage measurement control unit performs balancing with the balancing FET 142 of the cell balancing unit 140 in order to form a constant current flow in the battery cell in a state where there is no charging or discharging operation in the current forming control unit 156, which will be described later. By outputting the FET turn-on signal, a second voltage measurement signal can be output to the voltage measurement unit 120 to measure the voltage of the battery cell in a state of constant current flow without charging or operation. . Accordingly, the voltage measurement unit 120 that receives the second voltage measurement signal can measure the second voltage, which is the voltage of the battery cell when a constant current flows in a state where there is no charging or discharging operation, as described above.

That is, the first voltage measurement signal is a signal that controls to measure the voltage of the battery cell (hereinafter referred to as first voltage) when there is no balancing current in a state where there is no charging and discharging operation, and the second voltage measurement signal is a signal used to measure the voltage of the battery cell when there is no balancing current. And it is a control signal to measure the voltage of the battery cell (hereinafter referred to as the second voltage) when there is a balancing current in a state without a discharge operation.

Here, the voltage measurement control unit detects that the balancing FET turn-on signal is output from the balancing current generator 156 and then outputs the second voltage measurement signal to the voltage measurement unit 120 a predetermined time later. can do. This is to consider the time until the balancing FET turn-on signal is output and the balancing FET 142 is turned on, thereby forming a constant current flow (balancing current) in the battery cell. However, at this time, if a constant current flows through the battery cell, the voltage is stabilized, but the voltage of the battery cell continues to drop, which may affect the overall performance of the battery pack, so the above predetermined time is It should be set at an appropriate time taking these factors into account. The appropriate time may be set differently depending on the specifications of the battery cell.

all. Current formation control unit 156

The current generation control unit is configured to generate a constant flow of current (hereinafter referred to as balancing current) in the battery cell using the cell balancing unit 140.

When the first voltage measurement signal is output from the voltage measurement control unit 154 to the voltage measurement unit 120, the current forming control unit detects this and then sends it to the balancing FET 142 of the cell balancing unit 140. A balancing FET turn-on signal can be output. Accordingly, the balancing FET 142 is turned on to generate balancing current, that is, a constant current flow in the battery cell.

3.6. Cell resistance value calculation unit (160)

The cell resistance value calculation unit calculates the resistance value of the battery cell using the voltage measured by the voltage measurement unit and the preset balancing current value, and includes a cell voltage deviation calculation unit 152.

go. Cell voltage deviation calculation unit 162

The cell voltage deviation calculation unit is configured to calculate the difference (V2-V1) between the first voltage (V1) and the second voltage (V2) of each battery cell measured by the voltage measurement unit, that is, the battery for the formed balancing current. It measures the voltage drop of the cell. In other words, the difference (V2-V1) between the voltage of the cell (V1) measured in the absence of balancing current and the voltage (V2) of the cell measured in the state of forming the balancing current is calculated. This corresponds to the cell voltage difference calculation step (S500) described above.

The cell resistance value calculation unit 160 calculates the corresponding resistance value of each battery cell using the voltage deviation value of each battery cell calculated through the cell voltage deviation calculation unit 162 and the preset balancing current value. You can.

Here, the preset balancing current value refers to the balancing current formed when the current flowing through the balancing FET 142 of the cell balancing unit 140 is limited by the balancing resistor 144, as described above. It means size.

As described in the cell resistance value calculation step (S600), the resistance value can be calculated as cell resistance value = cell voltage deviation (V2-V1) / balancing current value.

3.7. Storage unit (170)

The storage unit is configured to store deterioration data according to the cell resistance value, which is the standard for diagnosing the cell deterioration state. The deterioration data is prepared through an experiment measuring resistance values according to the deterioration of battery cells, and can be expressed in the form of a table, for example, as shown in FIG. 2, and is referred to as a cell deterioration table in the present invention.

3.8. Deterioration condition diagnosis unit (180)

The deterioration state diagnosis unit uses the resistance value of each battery cell calculated by the cell resistance value calculation unit 160 based on the deterioration degree data according to the cell resistance value included in the cell deterioration degree table stored in the storage unit. This is a configuration that diagnoses the deterioration state of each battery cell. From the cell degradation table, the resistance section to which the cell's resistance value calculated by the cell resistance value calculation unit 160 belongs is detected, and the degradation degree corresponding to the detected resistance section is calculated to determine the deterioration state of the cell. It can be diagnosed. The cell deterioration state diagnosis step (S700) described above is performed, and the deterioration state of all battery cells included in the battery pack can be diagnosed in this manner.

Meanwhile, the technical idea of the present invention has been described in detail according to the above embodiments, but it should be noted that the above embodiments are for explanation and not limitation. Additionally, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

100: Battery pack
110: battery cell
120: Voltage measurement unit
130: Charge/discharge motion detection unit
140: Cell balancing unit
142: Balancing FET
144: Balancing resistance
150: control unit
152: Detection signal receiver
154: Voltage measurement control unit
156: Current formation control unit
160: Cell resistance value calculation unit
170: storage unit
180: Deterioration state diagnosis unit

Claims (13)

A detection signal output step of detecting a state in which there is no charging or discharging operation of the battery cell and outputting a detection signal;
A first voltage measurement step of measuring the first voltage of the battery cell as the detection signal is output through the detection signal output step;
After the first voltage measurement step, a current flow forming step of flowing a balancing current to a cell balancing circuit connected to the battery cell and including a predetermined balancing resistor;
a second voltage measurement step of measuring a second voltage of the battery cell in a state in which a balancing current flows through the current flow forming step;
A cell voltage difference calculation step of calculating a difference between the first voltage and the second voltage of the measured battery cell;
A cell resistance value calculation step of calculating a resistance value of the battery cell by dividing the difference between the first voltage and the second voltage calculated through the cell voltage deviation calculation step by a balancing current set by the balancing resistor;
A cell deterioration state diagnosis step of diagnosing the deterioration state by calculating the degree of deterioration of the corresponding cell according to the cell resistance value calculated in the cell resistance value calculation step;
It consists of:
In the second voltage measurement step,
Measuring the second voltage includes measuring the second voltage after a predetermined time after the balancing current begins to flow in the battery cell through the current flow forming step, and the voltage of the battery cell decreases during the predetermined time. It is decided to the extent that it does not
The cell deterioration state diagnosis step is,
Based on a pre-prepared cell degradation table containing degradation degree data according to the cell resistance value, which is a standard for diagnosing the cell degradation state, the resistance section to which the cell resistance value calculated in the cell resistance value calculation step belongs is detected, A cell deterioration state diagnosis method that diagnoses the deterioration state of the relevant battery cell by extracting the degree of deterioration corresponding to the detected resistance section. delete According to paragraph 1,
The current flow forming step is,
A balancing FET turn-on control step of controlling the turn-on of the balancing FET of the cell balancing circuit corresponding to the battery cell;
It consists of:
A method for diagnosing a cell deterioration state, characterized in that a balancing current is formed through the turned-on balancing FET. delete delete One or more battery cells;
A charging/discharging operation detection unit that detects a state in which there is no charging or discharging operation of the battery cell and outputs a detection signal;
Balancing FETs to control current flow; and a balancing resistor that limits the size of the balancing current flowing through the balancing FET; A cell balancing unit comprising:
When there is no charging and discharging operation of the battery cell, the first voltage of the battery cell is measured in a state where there is no charging and discharging operation of the battery cell, and when the cell balancing unit operates and a balancing current is formed in the battery cell, the battery cell a voltage measuring unit that measures the second voltage;
a control unit that controls the voltage measurement unit and the cell balancing unit depending on whether a detection signal is output from the charge/discharge operation detection unit;
a cell resistance value calculation unit that calculates a resistance value of a corresponding battery cell by dividing the difference between the first voltage and the second voltage measured under the control of the control unit by a balancing current set by the balancing resistor;
a storage unit that stores degradation degree data according to the cell resistance value, which is a standard for diagnosing the cell degradation state;
Based on the deterioration degree data according to the cell resistance value stored in the storage unit, the resistance section to which the resistance value of the battery cell calculated by the cell resistance value calculation unit belongs is detected and the deterioration degree corresponding to the detected resistance section is extracted. a deterioration state diagnosis unit that diagnoses the deterioration state of the corresponding cell;
It is composed including,
The control unit,
A detection signal receiving unit that receives a detection signal output from the charging/discharging operation detection unit;
A current formation control unit that outputs a balancing FET turn-on signal to the balancing FET of the cell balancing unit to control balancing current to be formed in the corresponding battery cell;
As the detection signal receiver receives the detection signal, a first voltage measurement signal is output to the voltage measurement unit to measure the voltage in a state in which there is no charging or discharging operation of the corresponding battery cell, and the current forming control unit performs cell balancing. A voltage measurement control unit that outputs a second voltage measurement signal to the voltage measurement unit to measure voltage in a state in which a balancing current is formed in the corresponding battery cell, as the balancing FET turn-on signal is output to the negative balancing FET;
It is composed including,
The output of the second voltage measurement signal from the voltage measurement control unit is a battery pack that detects the output of the balancing FET turn-on signal of the current formation control unit and outputs it after a predetermined time within the range where the voltage of the battery cell does not drop. . delete delete delete According to clause 6,
The voltage measuring unit,
As the first voltage measurement signal is received from the voltage measurement control unit of the control unit, the first voltage of the corresponding battery cell is measured,
A battery pack characterized in that, upon receiving a second voltage measurement signal from the voltage measurement control unit of the control unit, the second voltage of the corresponding battery cell is measured. According to clause 10,
The cell resistance value calculation unit,
a cell voltage difference calculation unit that calculates a difference between the first voltage and the second voltage of the battery cell measured by the voltage measurement unit;
It is characterized by being composed of,
A battery pack, characterized in that the resistance value of the battery cell is calculated by dividing the difference between the first voltage and the second voltage calculated by the cell voltage deviation calculation unit by the balancing current set by the balancing resistor.




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