KR20230022012A - The degradation delay method for battery and battery management system providing the same - Google Patents

Abstract

The present invention relates to a battery degradation reduction method and a battery management system providing the method. The battery management system (BMS) of the present invention, which reduces the degradation of a battery including a plurality of battery cells, comprises: a bypass circuit which includes a plurality of branch switches connected to the plurality of battery cells, respectively, in parallel to electrically separate the battery cells connected in parallel from the battery by being turned on; a cell monitoring IC which is connected to both ends of each of the plurality of battery cells to measure a cell voltage of each of the plurality of battery cells; and a main control circuit which turns on the branch switches connected to a first charging battery cell in parallel when the first charging battery cell having reached a charging upper limit voltage first is detected in a charging cycle of charging the battery with power of an external device.

Description

Battery deterioration reduction method and battery management system providing the method

The present invention relates to a method for reducing deterioration of a battery and a battery management system providing the method.

An electric vehicle is a vehicle that operates with electrical energy output from a battery composed of a predetermined number, for example, 2 to 4 batteries (battery pack). A battery may include a plurality of battery cells capable of being charged/discharged and may change its state depending on the external environment and its own characteristics. Accordingly, a battery management system (BMS) monitors and manages a plurality of battery cells included in a battery.

When each of the plurality of battery cells has performance within a predetermined range (hereinafter referred to as a battery cell within a normal range), the cell voltage of each of the plurality of battery cells fluctuates similarly within a predetermined range during a charge cycle and a discharge cycle. Therefore, even if the BMS terminates the charging cycle when a battery cell whose cell voltage reaches the charge final voltage is first generated, the battery can use all of its available battery capacity.

On the other hand, when a battery is used for a long period of time, a battery cell may degrade (deteriorate) and result in a battery cell (hereinafter referred to as a defective battery cell) out of performance within a predetermined range. A cell voltage of a defective battery cell may exhibit characteristics of reaching a charge final voltage or a discharge final voltage faster than cell voltages of battery cells within other normal ranges.

In a charge cycle or discharge cycle, after the cell voltage of a defective battery cell reaches the charge final voltage or discharge final voltage, the cell voltage of a battery cell within the other normal range It may take a considerable amount of time T to reach the charge final voltage or discharge final voltage. At this time, the defective battery cell has a problem in that deterioration (degeneration) is accelerated as overcharging or overdischarging is repeatedly performed.

The present invention provides a method for reducing deterioration of a battery capable of slowing down the deterioration rate of a battery cell and a battery management system providing the method.

A battery management system according to one feature of the present invention is a battery management system (BMS) that reduces deterioration of a battery including a plurality of battery cells, is connected in parallel to each of the plurality of battery cells, and operates on A bypass circuit including a plurality of branch switches electrically separating battery cells connected in parallel from the battery, and a cell monitoring IC connected to both ends of each of the plurality of battery cells to measure the cell voltage of each of the plurality of battery cells. And, in a charging cycle in which the battery is charged with power from an external device, when a first rechargeable battery cell whose cell voltage first reaches the charging upper limit voltage is detected, a branch switch connected in parallel to the first rechargeable battery cell is turned on. It includes a main control circuit that turns on.

The main control circuit may terminate the charging cycle when a second rechargeable battery cell whose cell voltage reaches the charging upper limit voltage for the second time in the charging cycle is detected.

The main control circuit, when a first discharged battery cell whose cell voltage first reaches the discharge lower limit voltage is detected in a discharge cycle for supplying discharged power of the battery to the external device, the first discharged battery cell. A branch switch connected in parallel to can be turned on.

The main control circuit may terminate the discharge cycle when a second discharge battery cell whose cell voltage reaches the discharge lower limit voltage secondly in the discharge cycle is detected.

A method for reducing deterioration of a battery according to another feature of the present invention is a method for reducing deterioration of a battery including a plurality of battery cells in a battery management system (BMS), wherein the battery is charged with power from an external device. detecting a first rechargeable battery cell whose cell voltage first reaches the charging upper limit voltage among the plurality of battery cells when a charging cycle of performing a charging cycle starts, and when the first rechargeable battery cell is detected, the first charging step. and turning on a branch switch connected in parallel to the battery cell, wherein the branch switch connected in parallel to the first rechargeable battery cell electrically separates the first rechargeable battery cell from the battery through an on operation.

The method for reducing deterioration of the battery may include, after turning on the branch switch, detecting a second rechargeable battery cell whose cell voltage reaches the charging upper limit voltage a second time, and the second rechargeable battery cell If detected, the step of terminating the charging cycle may be further included.

A method for reducing deterioration of a battery according to another feature of the present invention is a method for reducing deterioration of a battery including a plurality of battery cells by a battery management system (BMS), and converting the discharged power of the battery to an external When a discharge cycle supplied to the device starts, detecting a first discharged battery cell whose cell voltage first reaches a discharge lower limit voltage among the plurality of battery cells, and when the first discharged battery cell is detected, and turning on a branch switch connected in parallel to the first discharge battery cell, wherein the branch switch connected in parallel to the first discharge battery cell electrically separates the first discharge battery cell from the battery in an on operation.

The method for reducing deterioration of the battery may include, after turning on a branch switch connected in parallel to the first discharge battery cell, detecting a second discharge battery cell whose cell voltage reaches the discharge lower limit voltage for the second time; The method may further include terminating the discharge cycle when the second discharged battery cell is detected.

A battery management system according to another feature of the present invention is a battery management system (BMS) that reduces deterioration of a battery including a plurality of battery cells, and is connected in parallel to each of the plurality of battery cells to turn on A bypass circuit including a plurality of branch switches electrically separating battery cells connected in parallel from the battery in operation, cell monitoring connected to both ends of each of the plurality of battery cells and measuring cell voltage of each of the plurality of battery cells In a charging cycle in which the battery is charged with the power of the IC and an external device, when a rechargeable battery cell whose cell voltage reaches the charging upper limit voltage is detected, a main control circuit for turning on a branch switch connected in parallel to the rechargeable battery cell. wherein the main control circuit includes a first detection time when the total number of the rechargeable battery cells is greater than or equal to a first threshold and a time between a detection time of the Nth rechargeable battery cell and a detection time of the N−1th rechargeable battery cell When the time is equal to or greater than the second threshold, the charging cycle may be terminated.

The main control circuit may maintain the charging cycle when the first detection time is less than the second threshold.

The main control circuit turns a branch switch connected in parallel to the discharged battery cell when a discharged battery cell whose cell voltage reaches the discharge lower limit voltage is detected in a discharge cycle for supplying discharged power of the battery to the external device. on, the total number of discharged battery cells is greater than or equal to the first threshold, and a second detection time, which is a time between a detection time of the Nth discharged battery cell and a detection time of the N−1th discharged battery cell, is set to the second detection time. If it is equal to or greater than the threshold value, the discharge cycle may be terminated.

The main control circuit may maintain the discharge cycle when the second detection time is less than the second threshold.

A method for reducing deterioration of a battery according to another feature of the present invention is a method for reducing deterioration of a battery including a plurality of battery cells in a battery management system (BMS), wherein the battery is powered by power from an external device. When a charging cycle for charging starts, detecting a rechargeable battery cell whose cell voltage has reached an upper charging limit voltage among the plurality of battery cells, turning on a branch switch connected in parallel to the rechargeable battery cell, the step of turning on the rechargeable battery cell. If the total number of is equal to or greater than a first threshold, determining whether a detection time, which is a time between the detection time of the Nth rechargeable battery cell and the detection time of the N−1th rechargeable battery cell, is greater than or equal to a second threshold, and the determination As a result, if the detection time is equal to or greater than the second threshold value, the charging cycle may be terminated, and the branch switch electrically separates the rechargeable battery cell from the battery through an on operation.

A method for reducing deterioration of a battery according to another feature of the present invention is a method for reducing deterioration of a battery including a plurality of battery cells by a battery management system (BMS), and converting the discharged power of the battery to an external When a discharge cycle supplied to the device starts, detecting a discharged battery cell whose cell voltage has reached a discharge lower limit voltage among the plurality of battery cells, turning on a branch switch connected in parallel to the discharged battery cell, If the total number of battery cells is equal to or greater than a first threshold, determining whether a detection time, which is a time between a detection time of the Nth discharge battery cell and a detection time of the N−1th discharge battery cell, is greater than or equal to a second threshold, and and terminating the discharging cycle when the detection time is equal to or greater than the second threshold as a result of the determination, wherein the branch switch electrically separates the discharged battery cells connected in parallel from the battery in an on operation.

According to the present invention, when a first charged battery cell whose cell voltage first reaches a charge final voltage is detected, the first battery cell is electrically separated from the battery until the charging cycle is completed, and the first battery cell is electrically separated from the battery. A deterioration rate of the first battery cell may be slowed down by controlling the rechargeable battery cell not to be overcharged.

According to the present invention, when a first discharged battery cell whose cell voltage first reaches a discharge final voltage is detected, the first discharged battery cell is electrically disconnected from the battery until the discharge cycle is terminated. A deterioration rate of the first discharge battery cell may be slowed down by controlling the first discharge battery cell not to be over-discharged.

1 is a diagram illustrating a battery system according to an exemplary embodiment.
2 is a flowchart illustrating a method of reducing deterioration of a battery in a charging cycle according to an exemplary embodiment.
3 is a flowchart illustrating a method of reducing deterioration of a battery in a charging cycle according to another embodiment.
4 is a flowchart illustrating a method of reducing deterioration of a battery in a discharge cycle according to an exemplary embodiment.
5 is a flowchart illustrating a method of reducing deterioration of a battery in a discharge cycle according to another embodiment.

Hereinafter, the embodiments disclosed in this specification will be described in detail with reference to the accompanying drawings, but the same or similar reference numerals are given to the same or similar components, and overlapping descriptions thereof will be omitted. The suffixes "module" and/or "unit" for components used in the following description are given or used interchangeably in consideration of ease of writing the specification, and do not themselves have a meaning or role distinct from each other. In addition, in describing the embodiments disclosed in this specification, if it is determined that a detailed description of a related known technology may obscure the gist of the embodiment disclosed in this specification, the detailed description thereof will be omitted. In addition, the accompanying drawings are only for easy understanding of the embodiments disclosed in this specification, the technical idea disclosed in this specification is not limited by the accompanying drawings, and all changes included in the spirit and technical scope of the present invention , it should be understood to include equivalents or substitutes.

Terms including ordinal numbers, such as first and second, may be used to describe various components, but the components are not limited by the terms. These terms are only used for the purpose of distinguishing one component from another.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle.

In this application, terms such as "comprise" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

1 is a diagram illustrating a battery system according to an exemplary embodiment.

Referring to FIG. 1, the battery system 1 includes a battery 10, a current sensor 20, a relay 30, and a battery management system (hereinafter referred to as 'BMS') 40. do.

The battery 10 may include a plurality of battery cells (Cell1-Celln) electrically connected in series and parallel. In some embodiments, the battery cell may be a rechargeable secondary battery. A predetermined number of battery cells are connected in series to form a battery module, a predetermined number of battery modules are connected in series to form a battery pack, and a predetermined number of batteries are connected in parallel to form a battery bank. ) to supply desired power. 1 shows a battery 10 in which a plurality of battery cells (Cell1-Celln) are connected in series, but is not limited thereto, and the battery 10 may be configured in units of battery modules, battery packs, or battery banks. .

Each of the plurality of battery cells (Cell1-Celln) is electrically connected to the BMS 40 through wires. The BMS 40 collects and analyzes various information about battery cells including information about a plurality of battery cells (Cell1-Celln) to control charging and discharging of the battery cells, protection operation, etc., and operation of the relay 30. can control.

1, the battery 10 includes a plurality of battery cells (Cell1-Celln) connected in series, and is connected between two output terminals OUT1 and OUT2 of the battery system 1, and the battery system 1 A relay 30 is connected between the anode of the battery system 1 and the output terminal OUT1, and a current sensor 20 is connected between the cathode of the battery system 1 and the output terminal OUT2. The configurations shown in FIG. 1 and the connection relationship between the configurations are examples, but the invention is not limited thereto.

The current sensor 20 is connected in series to a current path between the battery 10 and an external device. The current sensor 20 may measure the battery current flowing through the battery 10, that is, the charging current and the discharging current, and transmit the measurement result to the BMS 40.

The relay 30 controls electrical connection between the battery system 1 and an external device. When the relay 30 is turned on, the battery system 1 and the external device are electrically connected to charge or discharge, and when the relay 30 is turned off, the battery system 1 and the external device are electrically separated. In this case, the external device may be a charger in a charging cycle in which power is supplied to the battery 10 to charge it, and a load in a discharging cycle in which power is discharged from the battery 10 .

The BMS 40 includes a bypass circuit 41 , a cell monitoring IC 43 and a main control circuit 45 .

The bypass circuit 41 may include a plurality of branch switches connected in parallel to each of the plurality of battery cells and electrically separating the battery cells connected in parallel from the battery 10 in an on operation.

Referring to FIG. 1 , when a branch switch is turned on in a charging cycle, power supplied to battery cells connected in parallel may be bypassed to other adjacent battery cells. When the branch switch is turned on in the discharge cycle, power may not be discharged from the battery cells connected in parallel. That is, when the branch switch is turned on, battery cells connected in parallel may be electrically separated from the battery 10 .

The cell monitoring IC 43 is electrically connected to an anode and a cathode of each of the plurality of battery cells Cell1 to Celln, and measures a cell voltage of each of the plurality of battery cells Cell1 to Celln. The battery current value measured by the current sensor 20 may be transmitted to the cell monitoring IC 43 . The cell monitoring IC 43 transfers information about the measured cell voltage and battery current to the main control circuit 45 . Specifically, the cell monitoring IC 43 measures the cell voltage of each of the plurality of battery cells (Cell1-Celln) every predetermined cycle during a rest period in which charging and discharging does not occur, and based on the measured cell voltage The cell current can be calculated. The cell monitoring IC 43 may transfer the cell voltage and cell current of each of the plurality of battery cells Cell1 to Celln to the main control circuit 45 .

Referring to FIG. 1 , the cell monitoring IC 43 generates control signals (SC[1] -SC[n]) according to the control of the main control circuit 45 to generate a plurality of branches in the bypass circuit 41. It is possible to control the on/off of each switch (SW ₁ to SWn).

The main control circuit 45 checks the order in which the cell voltage of each of the plurality of battery cells (Cell1-Celln) reaches a charge final voltage or a discharge final voltage, and determines the order in which the cell voltage reaches a charge final voltage or a discharge final voltage. Accordingly, the control of the bypass circuit 41 and the charge/discharge cycle may be terminated.

2 is a flowchart illustrating a method of reducing deterioration of a battery in a charging cycle according to an exemplary embodiment.

Hereinafter, with reference to FIGS. 1 and 2 , a method for reducing deterioration of a battery in a charging cycle and a BMS providing the method will be described in detail.

First, when a charging cycle in which the battery 10 is charged with power from an external device starts, the BMS 40 determines that the cell voltage among the plurality of battery cells Cell1-Celln reaches the charge final voltage (Vmax) first. The first rechargeable battery cell that arrives first is detected (S110, S120).

The charging upper limit voltage (Vmax) may be a maximum voltage (Max Voltage) that can be charged in a range in which the battery cell is not dangerous. The capacity of the battery cell may increase as the charging upper limit voltage Vmax is higher, but overcharging may make the battery cell dangerous. Accordingly, the charging upper limit voltage Vmax may be appropriately set in consideration of battery cell capacity and stability. The first rechargeable battery cell may indicate a battery cell whose cell voltage first reaches the charging upper limit voltage Vmax.

Next, the BMS 40 turns on the branch switch connected in parallel to the first rechargeable battery cell (S130).

The branch switch connected in parallel to the first rechargeable battery cell may electrically separate the first rechargeable battery cell connected in parallel from the battery 10 in an on operation. Then, power supplied to the first rechargeable battery cell is bypassed to other adjacent battery cells, and the first rechargeable battery cell continues to be charged until the cell voltage of the battery cells other than the first rechargeable battery cell reaches the charging upper limit voltage. The overcharged state can be blocked. That is, acceleration of deterioration (deterioration) of the first rechargeable battery cell can be prevented.

Next, the BMS 40 detects the second rechargeable battery cell whose cell voltage reaches the charging upper limit voltage Vmax secondly (S140).

Assume that the battery 10 includes five battery cells Cell1, Cell2, Cell3, Cell4, and Ce115, and a third battery cell Cell3 is detected as a first rechargeable battery cell. Then, the BMS 40 monitors the cell voltage of each of the first, second, fourth, and fifth battery cells (Cell1, Cell2, Cell4, and Ce115) excluding the third battery cell (Cell3), and Among the cell voltages of each of the 5 battery cells (Cell1, Cell2, Cell4, and Ce115), a battery cell that first reaches the charging upper limit voltage (Vmax) may be detected as a second rechargeable battery cell.

Next, when the second rechargeable battery cell is detected, the BMS 40 ends the charging cycle (S150).

The third battery cell (Cell3) is a defective battery cell that does not have performance within a predetermined range due to deterioration (degeneration), etc., and the first, second, fourth, and fifth battery cells (Cell1, Cell2, Cell4, Ce115) have a predetermined Assume a battery cell within the normal range with performance within the range. Then, the cell voltage of each of the first, second, fourth, and fifth battery cells (Cell1, Cell2, Cell4, and Ce115) may be equally increased or decreased within a predetermined range.

According to an embodiment, when one of the first, second, fourth, and fifth battery cells Cell1, Cell2, Cell4, and Ce115 is detected as the second rechargeable battery cell, even if the BMS 40 terminates the charging cycle, the first, Each of the 2, 4, and 5 battery cells (Cell1, Cell2, Cell4, and Ce115) may be in a charged state close to a usable capacity range. Then, acceleration of deterioration (deterioration) of the first rechargeable battery cell may be prevented, and the remaining battery cells may be charged to a usable capacity.

3 is a flowchart illustrating a method of reducing deterioration of a battery in a charging cycle according to another embodiment.

Hereinafter, with reference to FIGS. 1 and 3 , a method for reducing deterioration of a battery in a charging cycle and a BMS providing the method will be described in detail.

Referring to FIG. 3 , when a charging cycle for charging the battery 10 with power from an external device starts, the BMS 40 determines that the cell voltage among the plurality of battery cells Cell1-Celln is the upper limit voltage. A charged battery cell reaching Vmax) is detected (S210, S220).

The rechargeable battery cell may be a battery cell whose cell voltage reaches the charging upper limit voltage Vmax. For example, the BMS 40 first reaches the upper charging limit voltage Vmax when the cell voltage

A first rechargeable battery cell may be detected. Thereafter, according to a first threshold value to be described below, the BMS 40 determines the second rechargeable battery cell whose cell voltage reaches the upper charging limit voltage Vmax for the second time, and the second battery cell whose cell voltage reaches the upper charging limit voltage Vmax for the second time. A third rechargeable battery cell or the like that has reached the third may be sequentially detected.

Next, the BMS (40) turns on the branch switch connected in parallel to the rechargeable battery cell (S230).

The branch switch connected in parallel to the rechargeable battery cell may electrically separate the rechargeable battery cell from the battery 10 through an on operation. For example, when a first rechargeable battery cell, a second rechargeable battery cell, and a third rechargeable battery cell are sequentially detected, a branch switch connected in parallel to the first rechargeable battery cell of the BMS 40 and a branch switch connected in parallel to the second rechargeable battery cell are sequentially detected. The branch switch and the branch switch connected in parallel to the third rechargeable battery cell may be sequentially turned on.

Next, the BMS 40 determines whether the detected number of rechargeable battery cells is greater than or equal to a first threshold value (S240).

Next, if the determination result is that the number of rechargeable battery cells is less than the first threshold value (S240, No), the BMS 40 repeats steps S220 and S230.

Next, as a result of the determination, if the number of rechargeable battery cells is greater than or equal to the first threshold (S240, Yes), the BMS 40 determines whether the detection time ΔT is greater than or equal to the second threshold (S250).

For example, assume that the first threshold is the natural number 3. According to steps S220 and S230, the BMS 40 detects the first rechargeable battery cell and turns on the branch switch connected in parallel to the first rechargeable battery cell, detects the second rechargeable battery cell and parallel to the second rechargeable battery cell. A turn-on step of the connected branch switch may be performed. Then, when the third rechargeable battery cell is detected (S240, Yes), the BMS 40 determines whether the detection time ΔT for the third rechargeable battery cell is greater than or equal to the second threshold.

Next, if the determination result detection time (ΔT) is less than the second threshold value (S250, No), the BMS 40 repeats steps S220, S230, and S240.

The detection time ΔT may be a time between the detection time T _N of the Nth rechargeable battery cell and the detection time T _N−1 of the N−1th rechargeable battery cell. For example, the first threshold value is the natural number 3, the second threshold value is 5 seconds, the current (N) detection time point (T _N ) of the detected second rechargeable battery cell is 20 seconds, and immediately before (N-1) ) Assume that the detection time point T _N−1 of the detected first rechargeable battery cell is 18 seconds. When the BMS 40 detects the second rechargeable battery cell (S240, Yes), the first rechargeable battery cell is detected (T _N-1 ) and the second rechargeable battery cell is detected (T _N ). The detection time (ΔT = T _N -T _N-1 = 20 seconds - 18 seconds = 2 seconds) is calculated, and it can be determined that the calculated detection time (ΔT = 2 seconds) is less than the second threshold value (5 seconds). there is.

When the current (N) detection time point (T _N ) of the second rechargeable battery cell is small ( _ΔT ≤ th 2 threshold), the first rechargeable battery cell and the second rechargeable battery cell may be defective battery cells exhibiting similar voltage behavior. Accordingly, the BMS 40 repeats steps S220, S230, and S240 to maintain the charging cycle until the cell voltage of the battery cell within the normal range reaches the charging upper limit voltage Vmax.

Next, if the detection time (ΔT) of the charged battery cell is equal to or greater than the second threshold (S250, Yes) as a result of the determination, the BMS 40 ends the charging cycle (S260).

For example, the first threshold value is a natural number of 3, the second threshold value is 5 seconds, the current (N) detected time point (T _N ) of the third rechargeable battery cell is 27 seconds, and the previous (N-1) ) Assume that the detection time point T _N−1 of the detected second rechargeable battery cell is 20 seconds. When the third rechargeable battery cell is detected (S240, Yes), the BMS 40 determines the time between the second rechargeable battery cell is detected (T _N-1 ) and the third rechargeable battery cell is detected (T _N ). The detection time (ΔT = T _N -T _N-1 = 27 seconds - 20 seconds = 7 seconds) is calculated, and the calculated detection time (ΔT = 7 seconds) can be determined to be greater than or equal to the second threshold value (5 seconds). there is.

When the current (N) detection time point of the third rechargeable battery cell is large (ΔT > second threshold value) and the detection time point (T _N-1 ) of the second rechargeable battery cell detected immediately before (N-1) , the first and second rechargeable battery cells may be defective battery cells, and the third rechargeable battery cell may be a battery cell within a normal range. For example, the cell voltage of each of the first and second rechargeable battery cells may reach the charging upper limit voltage Vmax in about 18 seconds and about 20 seconds. The cell voltage of the third rechargeable battery cell may reach the charging upper limit voltage Vmax in about 27 seconds with a large time difference (a time difference of about 7 seconds or more) compared to the cell voltages of the first and second rechargeable battery cells.

According to an embodiment, the third battery cell Cell3 and the fourth battery cell Cell4 are defective battery cells that do not have performance within a predetermined range due to deterioration (degeneration), and the first, second, and fifth battery cells ( It is assumed that Cell1, Cell2, and Ce115) are battery cells within a normal range having performance within a preset range. Then, the time for the cell voltage of each of the third battery cell Cell3 and the fourth battery cell Cell4 to reach the charging upper limit voltage Vmax and the time for each of the first, second, and fifth battery cells Cell1, Cell2, and Ce115 The time for the cell voltage to reach the charging upper limit voltage Vmax may show a significant time difference (ΔT > second threshold value).

4 is a flowchart illustrating a method of reducing deterioration of a battery in a discharge cycle according to an exemplary embodiment.

Hereinafter, with reference to FIGS. 1 and 4 , a method for reducing deterioration of a battery in a discharge cycle and a BMS providing the method will be described in detail.

Referring to FIG. 4 , first, when a discharge cycle for supplying discharged power of the battery 10 to an external device starts, the BMS 40 determines that the cell voltage among the plurality of battery cells Cell1-Celln is the discharge lower limit voltage ( A first discharged battery cell first reaching a discharge final voltage (Vmin) is detected (S310 and S320).

The discharge lower limit voltage (Vmin) may be the lowest voltage (Min Voltage) at which the battery cell can be discharged in a non-hazardous range. As the discharge lower limit voltage (Vmin) is lowered, the capacity of the battery cell may increase, but overdischarge may make the battery cell dangerous. Accordingly, the discharge lower limit voltage Vmin may be appropriately set in consideration of battery cell capacity and stability.

The first discharged battery cell may indicate a battery cell whose cell voltage first reaches the discharge lower limit voltage Vmin.

Next, the BMS 40 turns on the branch switch connected in parallel to the first discharged battery cell (S330).

The branch switch connected in parallel to the first discharged battery cell may electrically separate the first discharged battery cell connected in parallel from the battery 10 in an on operation. Then, power is not discharged from the first discharged battery cell until the cell voltage of the remaining battery cells other than the first discharged battery cell reaches the discharge lower limit voltage Vmin, resulting in overdischarge in which the first discharged battery cell continues to be discharged. status can be blocked. Accordingly, it is possible to prevent acceleration of deterioration (deterioration) of the first discharged battery cell.

Next, the BMS 40 detects the second discharge battery cell whose cell voltage reaches the discharge lower limit voltage Vmin for the second time (S340).

Assume that the battery 10 includes five battery cells Cell1, Cell2, Cell3, Cell4, and Ce115, and a third battery cell Cell3 is detected as a first discharged battery cell. Then, the BMS 40 monitors the cell voltage of each of the first, second, fourth, and fifth battery cells (Cell1, Cell2, Cell4, and Ce115) excluding the third battery cell (Cell3), and Among the cell voltages of each of the 5 battery cells (Cell1, Cell2, Cell4, and Ce115), a battery cell that first reaches the discharge lower limit voltage (Vmin) may be detected as a second discharged battery cell.

Next, when the second discharged battery cell is detected, the BMS 40 ends the discharge cycle (S350).

The third battery cell (Cell3) is a defective battery cell that does not have performance within a predetermined range due to deterioration (degeneration), etc., and the first, second, fourth, and fifth battery cells (Cell1, Cell2, Cell4, Ce115) have a predetermined Assume a battery cell within the normal range with performance within the range. Then, the cell voltage of each of the first, second, fourth, and fifth battery cells (Cell1, Cell2, Cell4, and Ce115) may increase or decrease equally within a predetermined range.

According to an embodiment, when one of the first, second, fourth, and fifth battery cells Cell1, Cell2, Cell4, and Ce115 is detected as the second discharged battery cell, even if the BMS 40 terminates the discharge cycle, the first, Each of the 2, 4, and 5 battery cells (Cell1, Cell2, Cell4, and Ce115) can be discharged to a usable capacity range. Then, acceleration of deterioration (deterioration) of the first discharged battery cell can be prevented, and the available capacity of the remaining battery cells can be fully used.

5 is a flowchart illustrating a method of reducing deterioration of a battery in a discharge cycle according to another embodiment.

Hereinafter, with reference to FIGS. 1 and 5 , a method for reducing deterioration of a battery in a discharge cycle and a BMS providing the method will be described in detail.

Referring to FIG. 5 , when a discharge cycle for supplying discharged power of the battery 10 to an external device starts, the BMS 40 determines that the cell voltage among the plurality of battery cells (Cell1-Celln) is the discharge lower limit voltage (discharge final). A discharged battery cell reaching voltage, Vmin) is detected (S410, S420).

A discharged battery cell may be a battery cell whose cell voltage reaches the discharge lower limit voltage Vmin. For example, the BMS 40 first reaches the discharge lower limit voltage Vmin when the cell voltage

A first discharged battery cell may be detected. Thereafter, according to a first threshold value to be described below, the BMS 40 determines the second discharge battery cell whose cell voltage reaches the discharge lower limit voltage Vmin for the second time, and the second discharge battery cell whose cell voltage reaches the discharge lower limit voltage Vmin for the third time. A third discharged battery cell or the like that has reached the third may be sequentially detected.

Next, the BMS 40 turns on a branch switch connected in parallel to the discharged battery cell (S430).

The branch switch connected in parallel to the discharged battery cell may electrically separate the discharged battery cell from the battery 10 through an on operation. For example, when a first discharge battery cell, a second discharge battery cell, and a third discharge battery cell are sequentially detected, a branch switch connected in parallel to the first discharge battery cell of the BMS 40 and a branch switch connected in parallel to the second discharge battery cell are detected in sequence. The branch switch and the branch switch connected in parallel to the third discharge battery cell may be sequentially turned on.

Next, the BMS 40 determines whether the detected number of discharged battery cells is greater than or equal to a first threshold value (S440).

Next, as a result of the determination, if the number of discharged battery cells is less than the first threshold value (S440, No), the BMS 40 repeats steps S420 and S430.

Next, as a result of the determination, if the number of charged battery cells is greater than or equal to the first threshold (S440, Yes), the BMS 40 determines whether the detection time ΔT of the discharged battery cells is greater than or equal to the second threshold (S440, Yes). S450).

For example, assume that the first threshold is the natural number 3. According to steps S420 and S430, the BMS 40 detects the first discharged battery cell and turns on the branch switch connected in parallel to the first discharged battery cell, detects the second discharged battery cell and parallel to the second discharged battery cell. A turn-on step of the connected branch switch may be performed. Thereafter, when the third discharged battery cell is detected (S440, Yes), the BMS 40 determines whether the detection time ΔT is greater than or equal to the second threshold.

Next, if the detection time (ΔT) of the charged battery cell is less than the second threshold (S450, No) as a result of the determination, the BMS 40 repeats steps S420, S430, and S440.

The detection time ΔT may be a time between the detection time T _N of the Nth discharge battery cell and the detection time T _N−1 of the N−1th discharge battery cell. For example, the first threshold is a natural number of 2, the second threshold is 5 seconds, the current (N) detection time point (T _N ) of the detected second discharged battery cell is 20 seconds, and just before (N-1) ) Assume that the detection time point T _N−1 of the first discharged battery cell is 18 seconds. When the second discharged battery cell is detected (S440, Yes), the BMS 40 calculates the detection time (ΔT=T _N -T _N-1 =20 sec-18 sec=2 sec), and calculates the calculated detection time ( ΔT) may be determined to be less than the second threshold value (5 seconds).

When the current (N) detection time point (T _N ) of the second discharge battery cell is small (ΔT _≤ th 2 threshold), the first discharged battery cell and the second full battery cell may be defective battery cells exhibiting similar voltage behavior. Accordingly, the BMS 40 repeats steps S420, S430, and S440 to maintain the discharge cycle until the cell voltage of the battery cell within the normal range reaches the discharge lower limit voltage Vmin.

Next, as a result of the determination, if the detection time ΔT of the discharged battery cell is equal to or greater than the second threshold (S450, Yes), the BMS 40 ends the discharge cycle (S460).

For example, the first threshold value is the natural number 3, the second threshold value is 5 seconds, the current (N) detection time point (T _N ) of the third discharged battery cell is 27 seconds, and immediately before (N-1) ) Assume that the detection time point T _N-1 of the detected second discharged battery cell is 20 seconds. When the third discharge battery cell is detected (S440, Yes), the BMS 40 calculates the detection time (ΔT=T _N -T _N-1 =27 sec-20 sec=7 sec), and calculates the calculated detection time ( ΔT = 7 seconds) may be determined to be greater than or equal to the second threshold value (5 seconds).

If the current (N) detection time point of the third discharge battery cell and the detection time point (T N-1) of the second discharge battery cell detected immediately before ( _N-1 ) are large (ΔT > second threshold value) , the first and second discharged battery cells may be defective battery cells, and the third discharged battery cell may be a battery cell within a normal range. For example, the first and second discharged battery cells are defective battery cells, and each cell voltage may reach the discharge lower limit voltage (Vmin) in about 18 seconds and about 20 seconds. The cell voltage of the third discharge battery cell may reach the discharge lower limit voltage Vmin in about 27 seconds with a large time difference (a time difference of about 7 seconds or more) compared to the cell voltages of the first and second discharge battery cells.

According to an embodiment, the third battery cell Cell3 and the fourth battery cell Cell4 are defective battery cells that do not have performance within a predetermined range due to deterioration (degeneration), and the first, second, and fifth battery cells ( It is assumed that Cell1, Cell2, and Ce115) are battery cells within a normal range having performance within a preset range. Then, the time for the cell voltage of each of the third battery cell Cell3 and the fourth battery cell Cell4 to reach the discharge lower limit voltage Vmin and the time for each of the first, second, and fifth battery cells Cell1, Cell2, and Ce115 The time for the cell voltage to reach the discharge lower limit voltage Vmin may show a considerable time difference (ΔT > second threshold value).

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art in the field to which the present invention belongs are also the rights of the present invention. belong to the range

Claims (14)

A battery management system (BMS) that reduces deterioration of a battery including a plurality of battery cells,
A bypass circuit including a plurality of branch switches connected in parallel to each of the plurality of battery cells and electrically separating the battery cells connected in parallel from the battery in an on operation;
A cell monitoring IC connected to both ends of each of the plurality of battery cells to measure a cell voltage of each of the plurality of battery cells; and
Turning on a branch switch connected in parallel to the first rechargeable battery cell when a first rechargeable battery cell whose cell voltage first reaches the charging upper limit voltage is detected in a charging cycle for charging the battery with power from an external device. A battery management system, including a main control circuit. According to claim 1,
The main control circuit,
When a second charged battery cell whose cell voltage reaches the charging upper limit voltage for the second time in the charging cycle is detected, the battery management system terminates the charging cycle. According to claim 1,
The main control circuit,
In a discharge cycle for supplying the discharged power of the battery to the external device, when a first discharged battery cell whose cell voltage first reaches the discharge lower limit voltage is detected, a branch switch connected in parallel to the first discharged battery cell is operated. The battery management system which turns on. According to claim 3,
The main control circuit,
When a second discharge battery cell whose cell voltage reaches the discharge lower limit voltage for the second time in the discharge cycle is detected, the battery management system terminates the discharge cycle. A method for reducing deterioration of a battery including a plurality of battery cells by a battery management system (BMS),
When a charging cycle for charging the battery with power from an external device starts, detecting a first charged battery cell whose cell voltage first reaches an upper charging limit voltage among the plurality of battery cells; and
When the first rechargeable battery cell is detected, turning on a branch switch connected in parallel to the first rechargeable battery cell,
A branch switch connected in parallel to the first rechargeable battery cell,
A method of reducing deterioration of a battery, wherein the first rechargeable battery cell is electrically separated from the battery by an on operation. According to claim 5,
After turning on the branch switch,
detecting a second rechargeable battery cell whose cell voltage reaches the charging upper limit voltage a second time; and
The method of reducing deterioration of a battery further comprising terminating the charging cycle when the second rechargeable battery cell is detected. A method for reducing deterioration of a battery including a plurality of battery cells by a battery management system (BMS),
When a discharge cycle for supplying discharged power of the battery to an external device starts, detecting a first discharged battery cell whose cell voltage first reaches a discharge lower limit voltage among the plurality of battery cells; and
When the first discharge battery cell is detected, turning on a branch switch connected in parallel to the first discharge battery cell,
A branch switch connected in parallel to the first discharged battery cell,
A method of reducing deterioration of a battery, wherein the first discharged battery cell is electrically separated from the battery by an on operation. According to claim 7,
After turning on the branch switch connected in parallel to the first discharged battery cell,
detecting a second discharged battery cell whose cell voltage reaches the discharge lower limit voltage a second time; and
The method of reducing deterioration of a battery further comprising terminating the discharge cycle when the second discharged battery cell is detected. A battery management system (BMS) that reduces deterioration of a battery including a plurality of battery cells,
A bypass circuit including a plurality of branch switches connected in parallel to each of the plurality of battery cells and electrically separating the battery cells connected in parallel from the battery in an on operation;
A cell monitoring IC connected to both ends of each of the plurality of battery cells to measure a cell voltage of each of the plurality of battery cells; and
In a charging cycle in which the battery is charged with power from an external device, a main control circuit turning on a branch switch connected in parallel to the rechargeable battery cell when a rechargeable battery cell whose cell voltage reaches an upper charging limit voltage is detected,
The main control circuit,
When the total number of rechargeable battery cells is greater than or equal to a first threshold and the first detection time, which is the time between the detection time of the Nth rechargeable battery cell and the detection time of the N−1th rechargeable battery cell, is greater than or equal to the second threshold, Ending the charge cycle, the battery management system. According to claim 9,
The main control circuit,
If the first detection time is less than the second threshold, the battery management system maintains the charge cycle. According to claim 10,
The main control circuit,
In a discharge cycle for supplying the discharged power of the battery to the external device, when a discharged battery cell whose cell voltage reaches the discharge lower limit voltage is detected, a branch switch connected in parallel to the discharged battery cell is turned on,
The total number of discharged battery cells is greater than or equal to the first threshold, and a second detection time, which is the time between the detection time of the Nth discharged battery cell and the detection time of the N−1th discharged battery cell, is greater than or equal to the second threshold. If , the battery management system terminates the discharge cycle. According to claim 11,
The main control circuit,
If the second detection time is less than the second threshold, the battery management system maintains the discharge cycle. A method for reducing deterioration of a battery including a plurality of battery cells by a battery management system (BMS),
When a charging cycle for charging the battery with power from an external device starts, detecting a charged battery cell whose cell voltage reaches an upper charging limit voltage among the plurality of battery cells;
Turning on a branch switch connected in parallel to the rechargeable battery cell;
If the total number of rechargeable battery cells is equal to or greater than a first threshold, determining whether a detection time, which is a time between the detection time of the Nth rechargeable battery cell and the detection time of the N−1th rechargeable battery cell, is greater than or equal to a second threshold. , and
When the detection time is greater than or equal to the second threshold as a result of the determination, terminating the charging cycle;
The branch switch, in an on operation, electrically separates the rechargeable battery cell from the battery. A method for reducing deterioration of a battery including a plurality of battery cells by a battery management system (BMS),
When a discharge cycle for supplying discharged power of the battery to an external device starts, detecting a discharged battery cell whose cell voltage reaches a discharge lower limit voltage among the plurality of battery cells;
Turning on a branch switch connected in parallel to the discharged battery cell;
If the total number of discharged battery cells is equal to or greater than a first threshold, determining whether a detection time, which is a time between detection of the Nth discharged battery cell and detection of the N−1th discharged battery cell, is greater than or equal to a second threshold. , and
terminating the discharge cycle when the detection time is greater than or equal to the second threshold as a result of the determination;
The branch switch electrically separates the discharged battery cells connected in parallel from the battery in an on operation, the method of reducing deterioration of a battery.

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