KR102646533B1 - Battery cell charging/discharging device using SoH information and the method thereof - Google Patents

Abstract

The present invention proposes a battery cell charging and discharging device and method that bypasses the charging current supplied to a specific battery cell using SoH (State of Health) information of series-connected battery cells. The charging and discharging device of the present invention is configured to bypass the supplied charging current by selecting a battery cell exceeding its previous SoH capacity for each battery cell while charging a plurality of battery cells connected in series. Accordingly, there is an advantage in preventing problems that conventionally caused fire due to overheating when charging battery cells only considering the charging voltage.

Description

Battery cell charging/discharging device using SoH information and the method thereof}

The present invention is a battery cell charging and discharging device that prevents battery fires caused by overcharging by bypassing the charging current supplied to a specific battery cell using SoH (State of Health) information of series-connected battery cells; and It's about method.

Battery packs are manufactured by combining dozens to hundreds of battery cells into one to perform a specific role or function. And because battery cells can be reused through repeated charging/discharging processes, the battery pack can be used continuously until performance is maintained above a certain level.

However, when battery cells are connected in series, unbalance between battery cells occurs. Since this unbalance between battery cells is directly related to battery life, it is very important to minimize or prevent it. For example, if charging/discharging is repeated while the lifespan of a specific battery cell is shortened, problems such as overcharging and overdischarging may occur depending on the situation. And if you charge without considering the lifespan of the battery cell, a fire accident may occur due to overcharging.

Conventionally, the balancing method of battery cells is a method of controlling charging and discharging operations considering only the state of charge (SoC). The charging and discharging method using the SoC passively discharges (or bypasses) the battery cell with the higher cell voltage when the voltage of a specific battery cell is higher than that of the surrounding battery cells among the battery cells connected in series. This is a method of performing cell balancing.

However, this balancing method could not effectively prevent fire accidents in battery cells. For example, as a result of clinical trials of battery cells, if the SoC and SoH of the battery cell were less than 5%, fire may occur if charging continued at a cell voltage of 1.5V. In another example, there was a case where the battery cell voltage was 3.9V and the charging current flowed, but the voltage did not rise any further, so charging was not possible and only heat exceeding 100℃ was generated, leading to a fire. This is because the conventional battery cell balancing method uses the SoC concept to perform charging and discharging considering only voltage.

On the other hand, a fire in a battery cell is not simply caused by overvoltage, but may be caused by exceeding the allowable capacity (limit) of the battery cell, that is, SoH. Therefore, in order to prevent battery cell fires, it is absolutely necessary to have a way to bypass a sufficient value even below a certain voltage depending on the SoH of the battery cell.

Korean Patent No. 10-1028019 (Battery charge balancing method for hybrid vehicles) Korean Patent No. 10-1755911 (Device and method for estimating the state of charge of a vehicle battery)

The purpose of the present invention is to solve the above problems, by bypassing specific battery cells that exceed or have the possibility of exceeding their allowable capacity based on the SoH information of each battery cell connected in series. The object is to provide a charging and discharging device and method for controlling charging and discharging operations.

The technical problem of the present invention is not limited to the technical problem mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below.

To achieve this purpose, a battery cell charging and discharging device using SoH information according to an embodiment of the present invention includes a plurality of battery cells connected in series; During a charging operation, it is configured to include a control unit that calculates the previous SoH capacity for each battery cell and controls to bypass the charging current for battery cells exceeding the calculated previous SoH capacity.

The previous SoH capacity is calculated based on the previous charge/discharge cycle of the battery cells, and the SoH capacity is a value obtained by integrating voltage and current over time.

The charge/discharge cycle is performed at least once to charge the battery cells to a state of charge (SoC) of 80% and then obtain SoH capacity information of the battery cells.

It further includes pattern information on conditions in which bypass has previously been performed during the charging operation, and the control unit previously bypasses the battery cell in which the pattern information has occurred.

The control unit charges the battery cells whose SoH capacity is lowered by lowering the charge amount by the lowered SoH capacity.

The control unit may bypass the charging current by selecting a battery cell with the lowest SoH capacity or a battery cell with a relatively low SoH compared to other surrounding battery cells among the battery cells.

A battery cell charging and discharging device using SoH information according to another embodiment of the present invention includes a controller that controls the charging current supplied to one battery cell to be bypassed according to the SoH capacity of the battery cells connected in series. It is a device, and the controller includes: an individual BMS provided for each battery cell; a determination unit that determines whether the previous SoH capacity is exceeded during a charging operation using charge/discharge cycle information of the battery cell managed by the individual BMS; It is configured to include a control unit that bypasses battery cells that exceed the previous SoH capacity according to the determination result.

The SoH capacity is a value obtained by integrating voltage and current over time.

A method of charging and discharging a battery cell using SoH information according to another embodiment of the present invention includes a device for charging and discharging a battery cell to determine whether the previous SoH capacity of each battery cell is exceeded while charging battery cells connected in series. step; selecting a battery cell exceeding the previous SoH capacity according to the determination result; and bypassing the charging current supplied to the selected battery cell.

The previous SoH capacity is calculated based on the previous charge/discharge cycle of the battery cells.

The bypassed battery cell may be a battery cell with the lowest SoH capacity among battery cells connected in series or a battery cell with a relatively low SoH compared to other battery cells.

Further comprising storing pattern information for conditions under which the bypass has been performed, and performing an operation of bypassing charging current in advance for a battery cell in which the pattern information occurs during a charging operation of the battery cell. do.

According to the present invention, since the charging and discharging operation of the battery cell is controlled using the SoH information of the battery cells connected in series, it is possible to fundamentally prevent fires that occur when charging by considering only the charging voltage of the existing battery cell. There is a possible effect. In other words, if the previous SoH capacity of the battery cell is exceeded during the charging operation, the charging current is bypassed so that it is no longer supplied, so that charging is always performed within the allowable capacity range of the battery cell.

Therefore, fires due to overheating of battery cells can be prevented, and products equipped with battery cells can be used safely, which can be expected to improve product competitiveness.

1 is a block diagram of a battery cell charging and discharging device using SoH information according to an embodiment of the present invention.
Figure 2 is an overall flowchart explaining a charging and discharging method using a battery cell charging and discharging device using SoH information of the present invention.
3 to 6 are flowcharts explaining the charging and discharging operation of the battery cell of the present invention.

Since the present invention can be modified in various ways and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all transformations, equivalents, and substitutes included in the spirit and technical scope of the present invention. In describing the present invention, if it is determined that a detailed description of related known technologies may obscure the gist of the present invention, the detailed description will be omitted.

Terms such as first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another.

The terms used in the present invention are only used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

Spatially relative terms such as below, beneath, lower, above, upper, etc. facilitate the correlation between one element or component and other elements or components as shown in the drawing. It can be used to describe. Spatially relative terms should be understood as terms that include different directions of the element during use or operation in addition to the direction shown in the drawings. For example, when an element shown in a drawing is turned over, an element described as below (below, beneath) another element may be placed above (upper) the other element. Accordingly, the illustrative term below may include both downward and upward directions. Elements can also be oriented in other directions, so spatially relative terms can be interpreted according to orientation.

As used in the present invention, expressions indicating a part such as “part” or “part” mean that the corresponding component is a device that can include a specific function, software that can include a specific function, or a device that can include a specific function. It means that it can represent a combination of and software, but it cannot be said that it is necessarily limited to the expressed functions. This is only provided to help a more general understanding of the present invention, and is provided to those with ordinary knowledge in the field to which the present invention pertains. Various modifications and variations are possible from this description.

In addition, it should be noted that all electrical signals used in the present invention are examples, and if an inverter or the like is additionally provided in the circuit of the present invention, the signs of all electrical signals to be described below may be reversed. Therefore, the scope of the present invention is not limited to the direction of the signal.

Accordingly, the spirit of the present invention should not be limited to the described embodiments, and the scope of the patent claims described below as well as all things that are equivalent or equivalent to the scope of this patent claim shall fall within the scope of the spirit of the present invention. .

Hereinafter, the present invention will be described in more detail based on the embodiments shown in the drawings.

The present invention proposes a charging and discharging device that determines in real time which battery cells exceed the previous SoH capacity while charging series-connected battery cells and then bypasses the charging current. In addition, this specification will explain the SoH information of the battery cell by expressing it in various ways, such as the SoH capacity of the battery cell, allowable capacity, remaining life, etc. In other words, SoH information, SoH capacity, allowable capacity, remaining life, etc. are all used with the same meaning, and this becomes standard information for safely charging battery cells.

1 is a configuration diagram of a battery cell charging and discharging device using SoH information according to an embodiment of the present invention.

As shown in FIG. 1, the charging and discharging device 100 of this embodiment includes a battery pack 110 that has a plurality of battery cells 110a to 110n connected in series to store electrical energy supplied from the outside. An appropriate number of battery cells 110a to 110n will be provided depending on the load capacity using battery power. Here, the battery cells 110a to 110n may be batteries made of various materials (eg, lead, iron phosphate, all-solid, etc.). Of course, it is not limited to battery cells made of the above-mentioned materials and may include all battery cells made of other materials. In other words, the present invention is designed to prevent the risk of fire that may occur when charging only considering the existing charging voltage, and is designed to be applicable to all reusable battery cells.

This embodiment may include an individual BMS (Battery Management System) (120a to 120n) that manages charge/discharge information of each individual battery cell (110a to 110n). In general, individual BMS (120a ~ 120n) can be said to be a unit that manages charging and discharging operations of battery cells (110a ~ 110n). Accordingly, each BMS (120a ~ 120n) basically has basic information of the capacity, upper/lower limit voltage, maximum current limit value, and temperature limit value of the battery cell (110a ~ 110n). And the individual BMS (120a ~ 120n) also provides data necessary to evaluate the SoH of the battery cell according to the operation of the battery cell (110a ~ 110n). For example, provided data may include charge/discharge number (previous and cumulative number of cycles), maximum/minimum voltage, total usage time, etc.

This embodiment includes determination units 130a to 130n that determine whether the previous SoH capacity is exceeded using information provided by the individual BMSs 120a to 120n. The determination units 130a to 130n may determine the current SoH capacity information by comparing the previous SoH capacity information of each battery cell 110a to 110n. And the SoH capacity can be calculated using charge/discharge cycle information of the battery cells 110a to 110n. The SoH capacity uses Watt/Hour information of battery cells 110a to 110n. In other words, voltage and current are integrated over time and the integrated value is used, which is different from conventional charging and discharging operations that only consider the charging voltage. In FIG. 1, the determination units 130a to 130n are described as being provided for each battery cell 110a to 110n, but only one determination unit connected to all battery cells 110a to 110n is provided to determine whether the SoH capacity is exceeded. It is also possible to configure it to make a judgment.

This embodiment includes a control unit 140 that targets battery cells that exceed their current SoH capacity and bypasses the charging current supplied to the battery cells according to the determination result. Here, the control unit 140 may be a controller that controls the overall operation of the charging and discharging device 100 of the present invention.

Additionally, the control unit 140 can control bypass execution using pattern information of conditions under which bypass has previously been performed. Here, the fact that bypass has been previously performed means that there is a case where the battery cell exceeds its SoH capacity. This embodiment can be applied to other battery cells by using the conditions that allowed bypass to be performed in a specific battery cell. Therefore, when the pattern information occurs, the corresponding battery cell is expected to exceed its SoH capacity, and the charging current supplied to the battery cell is bypassed in advance.

Meanwhile, in the description of the above embodiment, the determination unit 130 and the control unit 140 are described as separate configurations, but in the present invention, the control unit 140 receives information necessary for SoH calculation from the individual BMSs 120a to 10n. It is also possible to configure it to have the function of calculating and comparing and determining whether to perform bypass. In addition, although it is explained as a hardware configuration, it is not necessarily limited to this, and it is also possible to configure it to determine and control whether the SoH capacity is exceeded using various methods such as programs, software, or algorithms.

Meanwhile, in the present invention, the determination unit 130 and the control unit 140 may be designed as a balance module that balances battery cells. Furthermore, it is possible to design the balance module to include a BMS 120 in addition to the determination unit 130 and the control unit 140. That is, the present invention is basically a device that performs charging and discharging operations including battery cells 110 and a balance module for balancing the battery cells 110.

Figure 2 is an overall flowchart explaining a charging and discharging method using a battery cell charging and discharging device using SoH information of the present invention.

The battery pack 110, which includes battery cells 110a to 110n connected in series, is mounted on various devices such as electric vehicles or drones and supplies driving power to the devices. These battery cells (110a to 110n) have a reusable battery cell structure and initially have the same SoH capacity (%), but the SoH capacity of the battery cells (110a to 110n) changes with continued use, and other battery cells Deviations from . At this time, the deviation may increase in proportion to the usage time.

In addition, the battery cells (110a ~ 110n) must be charged periodically. In this way, all battery cells (110a ~ 110n) connected in series will be charged while there is a difference in SoH capacity between the battery cells (110a ~ 110n). In this case, there is a possibility of fire occurring. In other words, in the past, the charging operation was performed considering only the charging voltage, and therefore, the charging current could continue to be supplied in excess of the SoH capacity of the battery cell itself, resulting in a fire due to overheating of the battery cell.

In order to solve this problem, as shown in FIG. 2, the present embodiment is a first process (S100) of charging the battery cells 110a to 110n connected in series, and during the charging operation, each battery cell 110a to 110n stores its previous SoH capacity. A second process of determining whether the capacity exceeds the previous SoH (S200), a third process of confirming and selecting the existence of a battery cell exceeding the previous SoH capacity (S300), and a fourth process of bypassing the charging current supplied to the selected battery cell (S400) ) and is designed to perform. The first to fourth processes (S100 to S400) are repeatedly performed until a separate command to stop the charging operation is issued.

Let’s look at the above process in detail.

The charging process of the first process (S100) is a process of charging battery cells 110a to 110n connected in series by supplying external power.

In the process of determining whether the previous SoH capacity of the second process (S200) is exceeded, the determination unit 130 determines whether the battery cell currently being charged is based on the previous charge/discharge cycle information stored in the individual BMS (120a ~ 120n). This is the process of determining whether the previous SoH capacity has been exceeded. In other words, in the case of battery cells that are continuously reused, SoH capacity has the characteristic of continuously changing. Therefore, it is determined when the current SoH capacity exceeds the previous SoH capacity, and this becomes the standard point at which bypass will be implemented. The reason for doing this is that it is only safe to charge by supplying a charging current within the currently given allowable capacity of the battery cells 110a to 110n. As previously explained, if the charging current continues to be supplied in excess of the constantly changing SoH capacity of the battery cells (110a to 110n), a fire may occur due to overheating.

Here, in order to determine whether the SoH capacity is exceeded, SoH information of the battery cells 110a to 110n must be known. However, for new or used battery cells, SoH information is not known. Therefore, in the present invention, when a battery cell is connected to a balance module (e.g., BBM: Battery Balancing Module), 2 to 4 charge/discharge cycle operations are performed (this embodiment performs 3 charge/discharge cycles) so that the SoC of the battery cells Perform the process of acquiring SoH information of the battery cell while charging it to about 80%. SoH information acquisition uses basic specification information such as voltage and current information of battery cells that the balance module has already received.

The reason for performing the charge/discharge cycle operation multiple times is to improve the accuracy of SoH information. Therefore, in some cases, it may be possible to obtain SoH information with just one cycle operation and perform the process of determining whether the SoH capacity is exceeded. Also, the reason why the SoC of the battery cell is charged to about 80% is because the most stable operating range may be when the battery cell is charged to about 80%. Of course, this amount of charge may vary depending on the battery cell.

And the balance module (i.e. BBM) of the present invention initializes all currently stored data when a new battery cell is connected or when a currently connected battery cell is disconnected and reconnected. This is because when a new battery cell is connected to the balance module, if it contains information from previous battery cells, incorrect SoH capacity information may cause the connected battery cell to overheat and cause a fire.

The third process (S300) and the fourth process (S400) are processes in which the control unit 140 bypasses the charging current supplied to battery cells that exceed the previous SoH capacity information. By bypassing the charging current, the battery cells 110a to 110n are charged only within their current allowable capacity range.

As described above, the battery cell charging and discharging control method of FIG. 2 continuously monitors the previous and current SoH capacity information of each battery cell (110a ~ 110n) connected in series, and detects the occurrence of a battery cell exceeding its allowable capacity. In this case, you can see that the process of bypassing this is repeated. Therefore, since a battery cell with a lowered SoH capacity is charged only within its SoH capacity, overheating of the battery cell can be prevented compared to conventional charging using only the SoC information of the battery cell.

In addition, it can be seen that the above-described embodiment bypasses any one battery cell that exceeds its SoH capacity among the battery cells 110a to 110n connected in series. This is because the SoH characteristics of only one of the battery cells 110a to 110n connected in series deteriorate and the SoH of the remaining battery cells remain the same.

Next, various embodiments of the charging and discharging control method of the present invention will be examined with reference to FIGS. 3 to 6.

First embodiment

This will be explained with reference to Figure 3. As shown in FIG. 3, it is assumed that there are four first to fourth battery cells connected in series and that these battery cells are charged (S500). And, as a result of SoH capacity calculation during the charging operation (S510), it is assumed that the SoH capacity of the first to third battery cells is 90%, and the SoH capacity of the fourth battery cell is less than 85% (S520).

In this case, the control unit 140 selects the fourth battery cell with the lowest SoH capacity among the first to fourth battery cells and controls the charging current to be bypassed (S530). In other words, the charge amount of the fourth battery cell with lower SoH capacity is lowered. If charging current is continuously supplied to the fourth battery cell with lower SoH capacity, a fire may occur due to overheating.

Second embodiment

Referring to FIG. 4, it is assumed that there are four first to fourth battery cells connected in series, similar to the first embodiment, and that these battery cells are charged (S600).

While charging a battery cell, previous SoH capacity information and current SoH capacity information of the first to fourth battery cells are calculated and transmitted to the control unit 140 in real time (S610).

Then, the control unit 140 determines whether there is a battery cell whose current SoH capacity is greater than or equal to the previous SoH capacity based on the previous and current SoH capacity information of the first to fourth battery cells (S620). Here, the SoH capacity becoming the same can refer to a case where the SoH capacity becomes the same as the previous SoH capacity as the battery cells continue to charge. As a result of this determination, if there is a battery cell whose current SoH capacity is greater than or equal to the previous SoH capacity (for example, assuming it is the first battery cell), the control unit 140 causes the charging current to be bypassed for the first battery cell. control, and the second to fourth battery cells normally supply charging current to perform the charging process (S630). For example, this may be the case where the previous SoH capacity of the first battery cell was 90%, but the current SoH capacity is higher than this. In reality, the SoH capacity continues to decrease, and the fact that the current SoH capacity is higher means that it has exceeded the SoH capacity of the battery cell itself.

On the other hand, if there is no battery cell with a current SoH capacity greater than the previous SoH capacity in the above determination step, the charging process for all first to fourth battery cells continues normally (S640).

Third embodiment

Referring to FIG. 5, it is assumed that there are four first to fourth battery cells connected in series, similar to the above embodiments, and that these battery cells are charged (S700).

And during charging of the battery cell, a process of selecting one battery cell is performed by comparing the SoH capacities of the first to fourth battery cells. Specifically, the above-mentioned process will be said to select a battery cell with a SoH capacity that has a low average deviation compared to the SoH capacity of the first to fourth battery cells. For example, it may be a battery cell with an average deviation as low as 1 to 2% (S710). Through this, you can also check which battery cells exceed your SoH capacity.

And, when a battery cell with excess capacity is identified, the charging process is performed by controlling the charging current to bypass only that battery cell and supplying charging current to other battery cells normally (S720).

Fourth embodiment

Referring to FIG. 6, it is assumed that there are four first to fourth battery cells connected in series, similar to the above embodiments, and that these battery cells are charged (S800). Also, if a specific battery cell has a history of being bypassed due to exceeding the SoH capacity during the charging operation, the conditions for exceeding the SoH capacity are processed into a series of pattern information and stored (S801). For example, the pattern information can be a specific point in graph information showing the charging and discharging cycle of a battery cell, and the pattern information can be a standard for bypassing.

While charging the first to fourth battery cells with the pattern information provided, the control unit 140 monitors whether the above pattern occurs in any one battery cell (S810). And when a pattern occurs in a specific battery cell (S820), the control unit 140 preliminarily determines that the battery cell may exceed its SoH capacity and controls the charging current to be bypassed in advance (S830). .

Of course, if the above pattern does not occur, the charging operation for the first to fourth battery cells continues to be performed (S840).

As described above, the present invention targets battery cells that exceed or are likely to exceed their SoH capacity by using SoH information calculated by Watt/hour of the battery cell, regardless of the charging voltage of the battery cell. It can be seen that the charging current is bypassed.

As described above, the present invention is described with reference to the illustrated embodiments, but these are merely illustrative examples, and those of ordinary skill in the art to which the present invention pertains can make various modifications without departing from the gist and scope of the present invention. It will be apparent that variations, modifications, and equivalent other embodiments are possible. Therefore, the true scope of technical protection of the present invention should be determined by the technical spirit of the appended claims.

100: Charging and discharging device for battery cells of the present invention
110a ~ 110n: Battery cells
110: battery pack
120: BMS
130: Judgment unit
140: control unit

Claims (12)

A plurality of battery cells connected in series; and
During the charging operation of the battery cells, referring to the previous SoH capacity that has changed for each battery cell, if the current SoH capacity of the battery cell being charged exceeds the previous SoH capacity, the battery cell voltage of the battery cell is even below a certain voltage. It includes a control unit that controls to bypass the charging current supplied to the battery cell,
The previous SoH capacity represents a power amount value obtained by integrating the product of voltage and current over time in the previous charge/discharge cycle of the battery cells. delete According to claim 1,
The charge/discharge cycle is performed at least once to charge the battery cells to a state of charge (SoC) of 80% and then obtain SoH capacity information of the battery cells. According to claim 1,
Further comprising pattern information about conditions in which bypass has previously been performed during the charging operation,
A device for charging and discharging a battery cell, wherein the control unit bypasses the battery cell in which the pattern information is generated in advance. According to claim 1,
The control unit charges a battery cell whose SoH capacity is lowered by lowering the charge amount of the battery cell by the lowered SoH capacity. According to claim 1,
The control unit selects a battery cell with the lowest SoH capacity among the battery cells or a battery cell with a relatively low SoH compared to other surrounding battery cells and bypasses the charging current. It is a charging and discharging device that includes a controller module that controls the charging current supplied to one battery cell to be bypassed according to the SoH capacity of the battery cells connected in series,
The controller module is,
Individual BMS provided for each battery cell;
a determination unit that determines whether the SoH capacity of the current charging operation exceeds the changed SoH capacity of the previous charging operation during a charging operation using charge/discharge cycle information of the battery cell managed by the individual BMS; and
It is configured to include a control unit that selects a battery cell whose SoH capacity of the current charging operation exceeds the SoH capacity of the previous charging operation according to the determination result and bypasses the charging current,
The previous SoH capacity represents a power amount value obtained by integrating the product of voltage and current over time in the previous charge/discharge cycle of the battery cells. delete A device that charges and discharges battery cells,
While charging battery cells connected in series, determining whether the current SoH capacity of each battery cell exceeds the previous changed SoH capacity;
selecting a battery cell whose current SoH capacity exceeds the previous SoH capacity according to a determination result; and bypassing the charging current supplied to the selected battery cell,
The previous SoH capacity represents a power amount value obtained by integrating the product of voltage and current over time in the previous charge/discharge cycle of the battery cells. delete According to clause 9,
The bypassed battery cell is a battery cell with the lowest SoH capacity among battery cells connected in series or a battery cell with a relatively low SoH compared to other battery cells. According to clause 9,
Further comprising the step of storing pattern information for conditions under which the bypass has been performed,
A method of charging and discharging a battery cell, wherein an operation is performed to bypass charging current in advance for a battery cell in which the pattern information is generated during a charging operation of the battery cell.

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