KR20120077482A - Balance charging apparatus for battery module - Google Patents

Abstract

The present invention relates to an even charging device for a battery module composed of a plurality of cells and a control method thereof.
The equal charging device of the battery module of the present invention includes n cells connected in series with each other; A power supply unit connected to the n cells in series to provide a constant current; A charge amount measuring unit measuring a charge amount of each cell; N first switching elements connected in series to each cell to supply and cut off current provided from the power supply unit to each cell; N second switching elements connected in parallel to each of the cells and the first switching elements connected in series to the cells; And a switching controller configured to control switching operations of the n first and second switching elements, respectively. Wherein the switching controller is configured to independently and simultaneously perform switching operations of the n first and second switching devices so that the cells are equally charged according to the charge amount of each cell measured by the charge amount measuring unit. To control.

Description

BALANCE CHARGING APPARATUS FOR BATTERY MODULE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery management system (BMS), and more particularly, to an even charging device of a battery module that allows a plurality of cells to be equally charged in each cell in a battery module connected in series. .

Due to the limits of energy reserves and environmental pollution, international movements to use new energy resources are emerging. Electric vehicles (EVs) and hybrid electrical vehicles (HEVs) are representative green technologies that best represent this movement.

In these new energy sources, the importance of secondary batteries is emphasized. A secondary battery is a device that converts external electrical energy into chemical energy and stores it and generates electricity when needed. Secondary batteries are widely used not only in vehicles but also in portable electronic devices such as mobile phones and laptops.

As the power consumption of a system using a secondary battery increases, and as a result, a high voltage progresses, an application of a battery module using a plurality of cells connected in series in a single cell is increasing. In this case, the use of multiple cells causes variation in capacity and charging between individual cells, and the charging deviation between the multiple cells serves to reduce capacity and shorten the lifespan.

In order to overcome this problem, a balancing technique of a battery module is conventionally proposed. For example, Korean Patent Publication No. 2005-0003852 discloses a battery balancing method of a battery pack having a plurality of batteries, and Korean Patent No. 0680901 discloses a battery in a battery management system including a master module and a plurality of slave modules. A technique for performing cell balancing of a pack is disclosed, and Korean Patent Laid-Open Publication No. 2005-055358 discloses a method of homogenizing a series connected battery.

However, in the related art, when the circuit is complicated and the cell is increased or the rapid charging is performed, energy loss occurs and the charging time is delayed. In addition, it is difficult to control the electromotive force of the battery to exactly the desired level with the cell balancing logic based on the charging voltage.

Accordingly, an object of the present invention is to provide an equal charging device for a battery module having a simple structure and minimizing energy loss.

Equal charging device of the battery module of the present invention for achieving the above object,

N cells connected in series with each other; A power supply unit connected to the n cells in series to provide a constant current; A charge amount measuring unit measuring a charge amount of each cell; N first switching elements connected in series to each cell to supply and cut off current provided from the power supply unit to each cell; N second switching elements connected in parallel to each of the cells and the first switching elements connected in series to the cells; And a switching controller configured to control switching operations of the n first and second switching elements, respectively. Wherein the switching controller is configured to independently and simultaneously perform switching operations of the n first and second switching devices so that the cells are equally charged according to the charge amount of each cell measured by the charge amount measuring unit. To control.

In one embodiment of the present invention, the switching control unit simultaneously performs the switching operation of the corresponding first and second switching elements so that a current is not supplied to a cell fully charged according to the charge amount of each cell measured by the charge amount measuring unit. Control box is preferred.

In this case, the switching controller is configured to operate the switching operation of the first and second switching elements such that the first switching element connected in series to the fully charged cell is opened and the second switching element connected in parallel is closed. Control at the same time.

In an embodiment of the present disclosure, the switching controller simultaneously controls the switching operation of the corresponding first and second switching elements to supply current to the cells that are not fully charged according to the charge amount of each cell measured by the charge amount charging unit. It is preferable to.

In this case, the switching control unit is configured to close the first switching element connected in series to the cell that is not fully charged, and to open the second switching element connected in parallel to the switching of the first and second switching elements. Control the operation at the same time.

In an embodiment of the present invention, it is determined whether the charge amount of each cell measured by the charge amount measuring unit is out of or exceeds a preset charge amount range, and when the charge amount is out of or exceeds the charge range, an overcharge / overflow outputting a signal to the switching controller. The apparatus may further include a pre-protection unit, wherein the switching control unit controls the switching operation of the connected first and second switching elements of the corresponding cell in response to a signal output from the overcharge / over-discharge prevention unit. It is preferable to be in a range.

In an embodiment of the invention, the cell comprises a LiFePO ₄ anode material.

The equal charging device of the battery module according to the present invention has the following effects.

First, the present invention has the effect that the circuit and the structure are simple and almost no energy loss occurs.

In addition, the present invention can be applied to the rapid charging of the large capacity battery module without difficulty, and it is possible to realize the miniaturization of the uniform charging device because no resistance is used.

Furthermore, the present invention can be used universally regardless of the capacity or charging time of the battery module.

1 is a block diagram of an equal charging device of a battery module according to an embodiment of the present invention.
2 is an operation example according to the overcharge and overdischarge of the battery module according to an embodiment of the present invention.
Figure 3 is a structural diagram of the material of the cell according to an embodiment of the present invention.
Figure 4 is a graph of the results of the experimental example and the test example not applied to the equalizing device of the battery module of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

1 is a block diagram of an equal charging device of a battery module according to an embodiment of the present invention.

As shown in FIG. 1, an equal charging device for a battery module according to the present invention includes a plurality of cells 110, a power supply unit 120, a charge amount measuring unit 130, a first switching device 140, and a second switching device ( 150, the switching control unit 160 is configured. Meanwhile, in another embodiment, the equalizing device of the battery module may further include an overcharge / over-discharge prevention unit 170.

The cell 110 is provided with n (n ≧ 2, natural numbers), each of which charges electricity. These n cells 110 are connected in series with each other to form a battery module.

The power supply unit 120 is connected in series to the n cells 110 and provides a constant current to each cell 110. Each cell 110 may be charged by this current.

The filling amount measuring unit 130 measures the filling amount of each cell 110. The charge amount measuring unit 130 may measure the charge amount by detecting the magnitude of the voltage charged for each cell, for example. Here, the charging amount measuring unit 130 may be preferably configured to n pieces to measure the charging amount corresponding to each cell 110 or may measure the charging amount for each of the n cells 110 in one device. The design of the charge amount measuring unit 130 can be changed by those skilled in the art.

The first switching device 140 is provided with n pieces and is connected in series to each cell 110 to supply and cut off the current provided from the power supply unit 120 to each cell 110. For example, when a specific first switching element 140 is opened, the current supply is cut off to the corresponding cell 110 connected in series, and when the specific first switching device 140 is closed, the current is supplied to the corresponding cell 110.

N second switching elements 150 are provided and connected in parallel to each of the cells 110 and the first switching elements 140 connected in series to the respective cells 110. The n second switching elements 150 form different current paths for each cell 110 to supply and cut off current to each cell 110 as shown in the drawing.

The switching controller 160 simultaneously and independently controls the switching operations of the n first and second switching devices. The switching controller 160 controls the number of the n first and second switching elements 140 and 150 to perform equal charging of each cell 110 according to the charge amount information of each cell 110 measured by the charge amount measuring unit 130. The switching operations are controlled independently of each other at the same time.

The overcharge / over-discharge prevention unit 170 determines whether the charge amount of each cell 110 measured by the charge amount measurement unit 130 is out of or exceeds the preset charge amount range, and when it is out of or exceeds the range, the switching controller ( 160) to output a signal. This is to operate the switching control unit 160 to control the switching of the first and second switching elements (140, 150) when overcharge or over discharge occurs. Accordingly, the switching controller 160 simultaneously controls the switching operations of the first and second switching devices 140 and 150 connected to the corresponding cell 110 independently of each other by a signal output from the overcharge / over-discharge prevention unit 170. This should be within the set range.

Hereinafter, with reference to Figure 1 will be described the operation of the equal charging device of the battery module according to the present invention through a specific example.

As described above, in the battery module, n cells 111, 112,..., And 11n are connected in series, and n first switching elements 141, 142,. 11n) are connected in series. In addition, n second switching elements 151, 152, ..., 15n are connected in series with the n first switching elements 141, 142, ..., 14n and the cells 111, 112, ..., 11n. Each is connected in parallel. Of course, these first and second switching elements are each independently controlled simultaneously by the switching control unit 160.

When charging is started, the n first switching elements 141 to 14n are closed and the n second switching elements 151 to 15n are opened to charge each cell 111 to 11n. As a result, current is supplied from the power supply unit 120 to the cells 111 to 11n through the first switching elements 141 to 14n to start charging. At this time, the amount of charge charged in each of the cells (111 ~ 11n) is measured by the charge amount measuring unit 130.

As such, the charge amount information for each cell 111 to 11n is inputted to the switching controller 160 and the first and second switching elements 141 to 14n and 151 to 15n associated with each other so that a current is no longer supplied to the fully charged cell. Switching is controlled simultaneously. In addition, switching of the associated first and second switching elements 141 to 14n and 151 to 15n is simultaneously controlled so that a current is continuously supplied to the cell that is not fully charged. For example, in the example of the drawing, when the first cell 141 is fully charged and the second cell 142 is not fully charged, the current is blocked to the first cell 141 and the current is supplied to the second cell 142. To do this, the first first switching element 141 is opened and the second first switching element 142 is closed, and at the same time, the first second switching element 151 is closed and the second second The switching element 152 is open.

As can be seen from this example, in the case of the third cell, the fourth cell, and the n-th cell, charging can be performed by simultaneously controlling the opening and closing of the first and second switching elements associated with the cell.

In addition, the switching of the first and second switching elements as described above in order to prevent overcharge or overdischarge when it is out of the preset charge amount range by the charge amount information of each of the cells 111-11n measured by the charge amount measurer 170. You can also control the operation at the same time.

2 is an example of operation according to the overcharge and overdischarge of the battery module according to an embodiment of the present invention.

Referring to FIG. 2, in the battery module according to the present invention, for example, the normal charge range of each cell is set to 2.0 to 3.6 V. When the battery module exceeds 3.6 V, it is determined that the battery is overcharged. Judging by the former, the discharge is cut off. This charging range may be changed in consideration of the type, characteristics, capacity, and the like of the cell.

3 is a structural diagram of the material of the cell according to an embodiment of the present invention.

Referring to FIG. 3, a cell according to an embodiment of the present invention includes a LiFePO ₄ anode material. Since LiFePO ₄ has an olivine structure, it has high stability. In the present invention, for example, ANR26650M1 cells using LiFePO ₄ cathode material commercially available from A123systems are applied. This cell is a product that greatly compensates for the low conductivity problem of existing lithium-based cells through the particle micronization and surface carbon coating of LiFePO ₄ powder, and its characteristics can maintain safety even at high charge of 10A (4.3C). Therefore, LiCoO ₂ and Ni-Mg cells, which are used in HEV and EV, are expected to be replaced. Lithium-based secondary batteries used in the prior art because of the low structural stability is not possible fast charging within 1 hour, whereas the LiFePO ₄ cells of the present invention has the advantage that the fast charging is possible.

Experimental Example

In this experiment, charging is performed when the equalizing device of the present invention is not applied (Experiment 1) and when the equalizing device is applied (Experiment 2, Experiment 3, Experiment 4) and the results are shown in FIG. 4.

When the equal charging device of the battery module according to the present invention is not applied as shown in Figure 4 it can be seen that the equal charging of each cell is not made at all. In this experiment, the most stable LiFePO ₄ cell among the lithium-based secondary batteries has been used so far, so there is no particular problem even when overcharging occurs. However, if the experiment was performed using LiCoO ₂ series lithium batteries, there is a possibility of explosion. Therefore, in this experiment, charging was started by connecting four A123systems ANR26650M1 cells made of LiFePO ₄ anode material in series, and a current source supplying a constant current of 8A was used and the charging time was set to 20 minutes. Specifically, four digital multimeters for cell voltage measurement, one digital power meter for power measurement used for charging, a power supply for supplying current for charging (35V 4A 2 channels), and a halogen for cell discharge Four bulbs (12V 100W) were used.

One) Experiment 1

4 (a) is a graph showing the results of charging four cells in series with different charges in series, as an experimental example without applying the equalizing device of the present invention. Since the remaining charge of each cell is different, the cell voltage at the beginning of charging is different. As shown in the graph, after about 13 minutes of charging time, the voltages of the third and fourth cells exceeded 3.62V and are fully charged, but the first and second cells are less charged. The cell that initially had the highest charge eventually moved beyond the charge range and stopped the experiment because of the risk of explosion. At this time, the voltage of the overcharged cell was about 3.82V. As such, when the equal charge control is not performed, it was confirmed that problems of overcharge and undercharge occur according to the remaining charge of each cell.

2) Experiment 2

Figure 4 (b) is an experimental example of applying the equalizing device of the present invention, a graph of the result of applying the equal charging device under the same conditions as in Experiment 1. The first cell, the second cell, and the third cell were fully charged sequentially after 4 minutes, 10 minutes, and 15 minutes, respectively, and the first to third cells, which were fully charged, were all in the middle of the charging of the other fourth cell. It was kept fully charged (3.62V). This means that even charging is performed well when the equal charging device of the present invention is applied.

3) Experiment 3

Figure 4 (c) is another experimental example of applying the equalizing device of the present invention, a graph showing the result of recharging after the first cell completely discharged in the experiment 2 (the other 2-4 cells are fully charged). . As shown in the graph, after about 16 minutes after the start of charging, the first cell was fully charged again and the other second to fourth cells also maintained the initial state of being fully charged.

4) Experiment 4

Figure 4 (d) is another experimental example applying the equalizing device of the present invention, a graph showing the results of fully charged after the full discharge in the experiment 2 again. As shown in the graph, about 16 minutes after the start of charging, all the cells remained fully charged. As the charging progresses, even if there is a slight deviation between cells, it can be seen that they are all equalized.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments. Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope of the appended claims, The genius will be so self-evident. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Recently, a secondary battery used in a hybrid vehicle (HEV), an electric vehicle (EV), a portable device, etc. is composed of a battery module in which a plurality of cells are connected in series. These battery modules require a battery management system (BMS) for safe use. The BMS system allows battery modules to operate within a safe range of use and performs charge equalization of each individual cell.

If the battery module is charged in a general manner, a problem of undercharging or overcharging may occur in a specific cell. This problem affects the capacity, life, etc. of the battery, so the battery module needs to be charged evenly.

In view of this aspect, the present invention will be very usefully applied to various industrial fields applying secondary batteries in that the battery module can be safely and quickly charged evenly regardless of the capacity or the charging time of the battery.

110: cell 120: power supply
130: charge amount measuring unit 140: first switching element
150: second switching element 160: switching control unit
170: overcharge / over discharge prevention unit

Claims (7)

N cells connected in series with each other;
A power supply unit connected to the n cells in series to provide a constant current;
A charge amount measuring unit measuring a charge amount of each cell;
N first switching elements connected in series to each cell to supply and cut off current provided from the power supply unit to each cell;
N second switching elements connected in parallel to each of the cells and the first switching elements connected in series to the cells; And
A switching controller which controls switching operations of the n first and second switching elements, respectively; Including;
The switching controller controls the switching operations of the n first and second switching elements independently and simultaneously simultaneously so that the cells are equally charged according to the charge amount of each cell measured by the charge amount measuring unit. Equal charging device for battery modules. The method of claim 1, wherein the switching control unit,
Equal charging device for a battery module, characterized in that for controlling the switching operation of the corresponding first and second switching elements at the same time so that the current is not supplied to the cell fully charged according to the charge amount of each cell measured by the charge amount measuring unit . The method of claim 2, wherein the switching control unit,
And simultaneously controlling the switching operations of the first and second switching elements such that the first switching element connected in series to the fully charged cell is open and the second switching elements connected in parallel close. Even charging unit for battery module. The method of claim 1, wherein the switching control unit,
Equal charging device for the battery module, characterized in that for controlling the switching operation of the first and second switching elements corresponding to supply the current to the cell that is not fully charged according to the charge amount of each cell measured by the charging unit. The method of claim 4, wherein the switching control unit,
Simultaneously controlling the switching operation of the first and second switching elements such that the first switching element connected in series to the cell that is not fully charged is closed and the second switching element connected in parallel to open. Equal charging device for battery modules. The method of claim 1,
It further includes an overcharge / over-discharge prevention unit for determining whether the charge amount of each cell measured by the charge amount measuring unit is out of or exceeds a preset charge amount range and outputs a signal to the switching controller when it is out of or exceeds the charge amount range, The switching controller controls the switching operation of the connected first and second switching elements of the cell in accordance with the signal output from the overcharge / over-discharge prevention unit so that the charge amount is within the range of the Even charging device. The method according to any one of claims 1 to 6,
And said cell comprises a LiFePO ₄ positive electrode material.

Images