Balancing mechanism for series-connected battery group

Abstract

To provide a balancing mechanism for a series-connected battery group to realize balancing of a plurality of batteries constituting a battery group in a manner that is logical, easy to control, and minimizes energy waste.SOLUTION: As an operation performed by a balancing mechanism that aligns voltages of individual cells forming a battery group to which a cell 11 is connected in series, (a) for each pair of adjacent cells (11a, 11b), the connection between the cells is switched from series to parallel so that the voltages of the two cells connected in parallel are equal, (b) the two cells (11a, 11b) whose voltages become equal in the previous stage are grouped together to form the next battery pair, and the adjacent next two battery pairs (11a and 11b, 11c and 11d) are connected in parallel so that the voltages of the two next battery pairs constituting each pair connected in parallel are equal, and (c) the above (b) is repeated until all the batteries constituting the battery group are connected in parallel and the voltages of each battery become the same.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a technology for voltage balancing in a battery group in which a plurality of cells are connected together. [Background technology]

[0002] Each cell has a voltage range of about 1V to 5V, and the voltage range is determined by the combination of the electrodes and electrolyte that make up the cell. When trying to drive large machinery such as automobiles, the voltage is insufficient if each individual cell is used as is, so the required voltage is obtained by connecting multiple cells in series. Cell combinations in which multiple cells are connected in series are further connected in series, or connected in parallel to ensure capacity.

[0003] However, the state of the cells is not constant as they are repeatedly charged and discharged, and gradually differences in the cell voltage occur. Differences occur between individual cells, and even between cells connected in series in the same number of cells. If this voltage difference is left unchecked and the battery is continued to be used, the battery capacity of the cell assembly may be underestimated due to the lower voltage of the cells, leading to a reduced range of use. There is also a risk that the rate at which each cell deteriorates may differ.

[0004] Patent Document 1 proposes a battery pack system that prevents further deterioration of already deteriorated battery cells in a battery pack by measuring the voltage of the cell with the maximum voltage and controlling the charging of other cells accordingly, thereby preventing overcharging and deterioration of the battery cells.

[0005] Furthermore, Patent Document 2 proposes a battery degradation equalization system that selects battery cells with a low level of degradation and allows the degradation to proceed evenly in each battery cell that makes up a battery block.

[0006] As such cell balancing, the methods of Patent Document 1 and Patent Document 2 are both control methods by charge / discharge operations that generate input / output of electrical energy between the battery group and the outside. Therefore, as a balancing method that does not require input / output of energy with the outside, a method is proposed in which individual cells connected in series are switched to be connected in parallel, and current flows from a high-voltage cell to a low-voltage cell to make the voltages uniform. Here, it is assumed that there are eight cells that exhibit voltages as shown in FIG. 20(a). The voltages of the individual cells 11a to 11h are, for example, 4.0V, 3.9V, 3.5V, 3.0V, 3.9V, 4.1V, 3.2V, and 3.7V. By switching this to a parallel connection as shown in FIG. 20(b), a current naturally flows from the high-voltage cell to the low-voltage cell, and after a certain time has passed, the current stops flowing, and after the circuit is disconnected, the voltages of the cells become uniform. By using this method, balancing can be performed without inputting or outputting electrical energy with the outside. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2008-220110 A [Patent Document 2] JP 2013-85315 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, when the cells are connected in parallel as shown in FIG. 20(b), if they are simply connected without controlling the current, the current is determined by the cell voltage difference at that time. If the cell voltage difference is large, a large current flows in a short time, and heat is generated by resistance. Also, if the connection method is not considered, the current flow becomes complicated and difficult to adjust. For example, when cell 11a (4.0V) and cell 11b (3.9V) are connected, cell 11a has a higher voltage, so current flows from cell 11a to cell 11b. However, if cell 11c (3.5V) is further connected in parallel to the parallel circuit, cell 11b has a higher voltage than cell 11b (3.9V) and cell 11c (3.5V), so cell 11b supplies current to cell 11c. In this way, if the parallel circuit is simply switched to as shown in FIG. 20(b) without considering the connection method, the direction and value of the current cannot be controlled, and there is a possibility of unexpected heat generation. Therefore, it becomes necessary to control the direction and value of the current.

[0009] Another method is to insert a capacitor between the batteries, but the circuit becomes complicated when trying to optimize the current value to suit various voltage differences.

[0010] Therefore, an object of the present invention is to achieve balancing of multiple batteries that make up a battery group using a method that minimizes waste of electrical energy, from the viewpoint of making it easy to control current and not requiring external input / output of energy for the sole purpose of aligning voltage. [Means for solving the problem]

[0011] As a first solution, the present invention provides: A battery group in which batteries, which are cells or cell combinations, are connected in series, has a balancing mechanism that equalizes the voltages of the individual batteries that make up the battery group, and the balancing mechanism performs the following operations: (a) switching the connection between the batteries from series to parallel for each pair of adjacent batteries so that the voltages of the two batteries connected in parallel are the same; (b) combining the two batteries or battery sets that have been made the same in voltage in the previous step into a next battery set, and connecting two adjacent next battery sets in parallel so that the voltages of the two next battery sets that make up each set connected in parallel are the same; (c) Repeating (b) above until all the batteries constituting the battery group are connected in parallel and the voltages of the individual batteries are the same. The battery group solved the above problems.

[0012] In addition to the first solving means, the battery group according to the present invention has the following features: The balancing mechanism may employ a second solution in which a switching regulator is provided between each of the batteries.

[0013] In addition to the second solving means, the battery group according to the present invention has the following features: A third solution can be adopted in which the switching regulator is a step-down type, the balancing mechanism includes an input / output changeover switch, and the battery or battery set having a higher voltage is connected to the input side of the switching regulator.

[0014] In addition, the present invention provides a battery pack according to any one of the first to third solving means, and a load mechanism driven by the battery pack, The load mechanism has an off timer that is set so that no current flows, Only during a certain period of time of the off timer, the battery group and the load mechanism are electrically separated, During a certain period of time of the off timer, the voltage of the higher of the two batteries or battery sets is controlled by pulse width to perform the operation of the balancing mechanism. A battery-powered system can be a fourth solution. Effect of the Invention

[0015] In the battery group according to the present invention, the balancing mechanism performs the task of making the voltages the same for each set of batteries or battery groups, so the current flow can be clearly controlled from the higher voltage to the lower voltage on a one-to-one basis. By repeating this task any number of times, balancing can be achieved with simple control in the same way for any battery group consisting of a power of two batteries.

[0016] Also, a simple method of adjusting cell voltage is to insert a resistor between batteries with a high cell voltage to match the voltage of the other cells, but this generates heat through the resistor, consuming energy, which is wasteful.By using a switching regulator as a solution, it becomes possible to set any voltage, which in turn allows any current value to be set, and by effectively utilizing the time gained by the off timer, it is possible to minimize the current, saving the heat generated by the resistor and the energy that was previously wasted as heat.

[0017] If a step-down switching regulator is adopted as a solution equipped with an input / output changeover switch, balancing can be achieved by transferring electrical energy from higher voltage cells to lower voltage cells through parallel connection, which can be achieved as simple control by switching only. [Brief description of the drawings]

[0018] [Figure 1] A diagram showing the configuration of an embodiment of a battery group according to the present invention, which is made up of eight cells connected in series. [Diagram 2] Configuration diagram of the embodiment of FIG. 1 switched as the first stage (quarterfinal) [Diagram 3] Configuration diagram of the embodiment of FIG. 1 in the second stage (semi-final) [Figure 4] A configuration diagram of the embodiment of FIG. 1 in the third stage (final) [Diagram 5] A wiring example diagram in which a switching relay is provided between cells to enable switching between series and parallel [Figure 6] (a) Configuration diagram of the switching relay, (b) Configuration diagram switched from (a) [Figure 7] (a) Schematic diagram of a disconnect relay, (b) Schematic diagram cut from (a) [Figure 8] Configuration diagram showing switching relays and disconnecting relays placed between cells [Figure 9] Wiring diagram for switching between series and parallel circuits using switching regulators between cells [Figure 10] Balancing wiring diagram when cell 11a has a higher voltage in Figure 9 [Figure 11] Balancing wiring diagram when cell 11b has a higher voltage in Figure 9 [Figure 12] Wiring diagram that remains parallel after Fig. 10 or Fig. 11 [Figure 13] A wiring diagram to realize Figure 9 by arranging a switching relay and a switching regulator between cells. [Figure 14] (a) Schematic diagram of input / output switching relay, (b) Schematic diagram switched from (a) [Figure 15] (a) Schematic diagram of a series-parallel changeover relay, (b) Schematic diagram switched from (a) [Figure 16] Balancing wiring diagram when cell 11a has a higher voltage in Figure 13 [Figure 17] Balancing wiring diagram when cell 11b has a higher voltage in Figure 13 [Figure 18] Wiring diagram of Fig. 16 or Fig. 16 after which the parallel connection remains [Figure 19] (a) Battery-powered system in normal mode, (b) state when switching from (a) to maintenance mode and separated from charging and discharging, (c) state when switching from (b) to mode 2, (d) state when switching from (c) to mode 3, (e) state when switching from (d) to mode 4. [Figure 20] (a) Example of the configuration of a battery group consisting of eight cells with a voltage difference using the conventional method, (b) Expected current direction when the eight cells in (a) are simply connected DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present invention relates to a battery group in which cells or cell combinations are connected in series, and has a balancing mechanism for equalizing the voltages of the individual batteries that make up the battery group. Here, a cell is the smallest unit of a battery having a positive electrode and a negative electrode with an electrolyte sandwiched therebetween, and is a rechargeable secondary battery. In particular, the present invention is suitable for use with lithium ion batteries that have high voltage and high output as a single cell and can be used in electric vehicles, etc. A cell combination is a combination in which the cells are connected in series or parallel and the connection state is fixed. A battery module or battery pack having multiple cells therein and having a pair of electrodes drawn out can be suitably used as a cell combination. Balancing refers to equalizing or attempting to equalize the voltages of multiple cells or cell combinations, and completion of balancing refers to the completion of equalizing the voltages. A balancing mechanism is a device including a circuit for performing balancing and its control.

[0020] The balancing mechanism can be suitably implemented in the battery group according to the present invention when the battery group has a number of the batteries that is a power of 2. If the number of the batteries is not a power of 2, it is preferable to implement the balancing mechanism as a battery group in units of a power of 2. For example, in the case of a battery group consisting of 24 cells, balancing is performed by dividing the battery group into a battery group consisting of 16 cells and a battery group consisting of 8 cells.

[0021] First, a specific procedure of the balancing mechanism will be described using an embodiment of a battery group consisting of eight cells. Although cells are taken as an example of the battery, the same procedure can be realized with a cell combination in which multiple cells are linked together and connected in a fixed state instead of cells. This embodiment is a battery group in which cells 11a to 11h are connected in series as shown in FIG. 1. The upper side of each cell is a positive pole and the lower side is a negative pole. When a difference may occur in the individual voltages of the cells 11a to 11h that constitute the battery group operated in this way, balancing is performed to smooth out the voltage difference and make it uniform.

[0022] As a first step, the connection between the cells is switched from series to parallel for each pair of adjacent cells. This connection relationship switched from the embodiment of FIG. 1 is shown in FIG. 2. Each pair is connected in parallel, and the connection between the pairs is cut off. The cells in the present invention are finally configured as shown in the tournament diagram, and the state in which two of the eight cells are connected together and are independent into four groups is called the "quarterfinal" form for convenience. The two cells connected in parallel to form a tournament battle state are connected with their + poles connected to each other and with their - poles connected to each other, so that a current flows from the high-voltage cell to the low-voltage cell, the voltage of the high-voltage cell decreases, and the voltage of the low-voltage cell increases, and finally the voltages of the two cells become the same.

[0023] In the second stage, the two cells whose voltages have become the same in the first stage are treated as one battery set (first battery set), and two adjacent battery sets are connected in parallel. This connection relationship, which has been switched from the embodiment in FIG. 2, is shown in FIG. 3. That is, the voltages of the cells 11a and 11b connected in parallel in the previous stage (first stage) become the same, and this is treated as one next battery set. This battery set is connected in parallel to the adjacent battery set, that is, the battery set of the cells 11c and 11d including the cell 11c that was connected to the cell 11b in the initial series connection. As a result, a current flows from the battery set with the higher voltage to the battery set with the lower voltage, the voltage of the battery set with the higher voltage decreases, and the voltage of the battery set with the lower voltage increases, and finally the voltages of the two battery sets become the same. That is, the voltages of the four cells constituting the two battery sets become the same. Meanwhile, at this stage, the cell 11d and the cell 11e that were connected in the initial series connection remain disconnected. Cells 11e to 11h are also connected in parallel in the same way as cells 11a to 11d, and the voltages of these four cells are the same. For convenience, this state in which four of the eight cells are connected in parallel and separated into two groups is called the "semi-final" configuration.

[0024] In the third stage, the two battery sets (four cells) whose voltages have become the same in the second stage are treated as one battery set (secondary battery set), and two adjacent battery sets (secondary battery sets) are connected in parallel. This connection relationship, which has been switched from the embodiment in FIG. 3, is shown in FIG. 4. That is, the voltages of the cells 11a to 11d connected in parallel in the previous stage (second stage) become the same, and this is treated as one next battery set (secondary battery set). The adjacent battery set (secondary battery set) of cells 11e to 11h including the cell 11e that was connected to the cell 11d in the initial series connection is connected in parallel. As a result, a current flows from the battery set with the higher voltage to the battery set with the lower voltage, the voltage of the battery set with the higher voltage decreases, and the voltage of the battery set with the lower voltage increases, and finally the voltages of the two battery sets become the same. That is, the voltages of the eight cells constituting the two battery sets become the same. In this way, the state in which all eight cells are connected in parallel and balancing is completed is called the "final" form for convenience.

[0025] In the above embodiment, balancing was performed for eight cells in the first to third stages, but if the number of cells is increased, balancing can be performed using a similar procedure, with only the number of steps from the second stage onwards increasing. If the number of cells is 16, balancing can be performed by connecting the cells in parallel for the "first round," connecting the resulting battery groups (first battery groups) in the "quarterfinals," connecting the resulting second battery groups in the "semifinals," and connecting the resulting third battery groups in the "finals." If the number of cells is 32, balancing can be performed by connecting the cells in parallel for the "first round," "second round," "quarterfinals," "semifinals," and "finals."

[0026] Although such connection and disconnection by switching can be realized by a manual switch, it is preferable to use a relay or a transistor that can be switched by an electric signal from the viewpoint of remote operation and automatic control. For example, a relay that can be switched by an excitation trigger is provided in the connection between each cell, and the excitation trigger is operated by an electric signal to the relay, so that the entire battery group can be switched at the same time. A form in which a relay is provided between each cell and switching is described with reference to FIG. 5. Of the embodiment shown in FIG. 1, the cells 11a to 11d on the left side are enlarged and explained due to the space in the drawing. Cells 11e to 11h, which are basically the same configuration, are formed on the right side of the drawing. The left side of each cell is a positive pole and the right side is a negative pole, and are indicated as 11a+ and 11b-, respectively. Switching relays 21a to 21g for switching between series and parallel are provided between each cell.

[0027] Enlarged views of the switching relay 21 are shown in Fig. 6(a) and (b). Let us suppose that the default state is shown in Fig. 6(a), and the switched state is shown in Fig. 6(b). The switching relay 21 has a switch 23 (23-1, 23-2) that can switch the internal connection relationship by an excitation trigger 22. Terminals 24, 25 whose connection relationship can be switched by the switch 23 are provided on the left and right, and there are three left terminals 24 (24-1, 24-2, 24-3) and two right terminals 25 (25-1, 25-2). In the default state (Fig. 6(a)), the left terminal 24-2 and the right terminal 25-1 are connected by the switch 23-1, and the left terminal 24-3 and the right terminal 25-2 are connected by the switch 23-2. In the switched state (FIG. 6(b)), the left terminal 24-1 and the right terminal 25-1 are connected by the switch 23-1, and the left terminal 24-2 and the right terminal 25-2 are connected by the switch 23-2.

[0028] The connection relationship between the cell 11 and the switching relay 21 is as follows. The positive pole of the cell 11 (for example, 11a) located on the left side of the switching relay 21 (for example, 21a) is connected to the left terminal 24-1, and the negative pole of the cell 11 is connected to the left terminal 24-2. The positive pole of the cell 11 (for example, 11b) located on the right side of the switching relay 21 (for example, 21a) is connected to the right terminal 25-1, and the negative pole of the cell 11 is connected to the right terminal 25-2. In this way, when the switching relay 21 is in the default state (FIG. 6(a)), the negative pole of the cell 11a is connected to the positive pole of the cell 11b via the left terminal 24-2, the switch 23-1, and the right terminal 25-1. On the other hand, the switch 23-2 is in a floating state. This realizes a series connection as shown in FIG. 1. On the other hand, when the switching relay 21 is in a switched state (FIG. 6(b)), the positive pole of the cell 11a is connected to the positive pole of the cell 11b via the left terminal 24-1, the switch 23-1, and the right terminal 25-1. On the other hand, the negative pole of the cell 11a is connected to the negative pole of the cell 11b via the left terminal 24-2, the switch 23-2, and the right terminal 25-2. This realizes switching to a parallel connection as shown in FIG. 2. Note that the terminals in the relay are referred to as the right and left here simply for the purpose of distinction in the description, and there is no particular problem even if the left and right are all reversed in implementation.

[0029] In addition to the switching relay 21, a disconnecting relay 26 is provided between the cells 11b and 11c, between the cells 11d and 11e, and between the cells 11f and 11g. That is, the disconnecting relay 26 is provided at the location that will be disconnected in the "first round" of the tournament (corresponding to the "quarterfinals" in the case of eight cells). Enlarged views of the disconnecting relay 26 are shown in Figs. 7(a) and (b). Fig. 7(a) shows the default connected state, and Fig. 7(b) shows the disconnected state. The disconnecting relay 26 has switchable switches 28 (28-1, 28-2) that can switch between connection and disconnection between the terminals at both ends by an excitation trigger 27. There are two left terminals 29 (29-1, 29-2) and two right terminals 30 (30-1, 30-2). In the default state, the switches 28-1 and 28-2 respectively connect the left terminal 29-1 to the right terminal 30-1 and the left terminal 29-2 to the right terminal 30-2. In the switched state (FIG. 7(b)), the switches 28-1 and 28-2 float and the terminals at both ends are no longer connected.

[0030] The connection relationship between the cell 11, the switching relay 21, and the disconnecting relay 26 is as follows. Hereinafter, the lowercase alphabets and sub-numbers of each terminal and switch are identified by adding the same letters as the lowercase alphabets and sub-numbers of the relays having the terminals and switches. The anteroposterior relationship of the switching relay 21b between the cells 11b and 11c and the disconnecting relay 26a arranged in parallel is shown in FIG. 8. The state shown is the default state in which they are connected in series. The left terminal 24-2b and the right terminal 25-1b of the switching relay 21b connected to the negative pole of the cell 11b are connected to the left terminal 29-1a of the disconnecting relay 26a. The left terminal 29-1a is connected to the right terminal 30-1a because the switch 28-1a is in a connected state, and is connected to the positive pole of the cell 11c. That is, in the default state, the negative pole of the cell 11b and the positive pole of the cell 11c are connected. On the other hand, the left terminal 29-2a of the disconnecting relay 26a is connected to the right terminal 25-2b of the switching relay 21b, and is not connected to the pole on the cell 11b side. On the other hand, the right terminal 30-2a of the disconnecting relay 26a is connected to the left terminal 24-2c of the next switching relay 21c and the negative pole of the cell 11c. However, when the switching relay 21b is in a switching state, the left terminal 24-1b is connected to the right terminal 25-1b, and the left terminal 24-2b is connected to the right terminal 25-2b, so that the disconnecting relay 26a connects between the positive pole of the cell 11b and the positive pole of the cell 11c, and between the negative pole of the cell 11b and the negative pole of the cell 11c. Furthermore, when the disconnecting relay 26 is switched to the disconnecting state, the cell 11b and the cell 11c are disconnected regardless of the state of the switching relay 21b.

[0031] The connection state of the cells can be switched by combining the switching relay 21 and disconnecting relay 26 configured in this way. An example will be described in which the eight cells 11a to 11h shown in Fig. 1 are configured with switching relays 21a to 21g installed between each cell 11, disconnecting relays 26a to 26c installed between cells 11b and 11c, between cells 11d and 11e, and between cells 11f and 11g, and the front and rear of each relay are connected as shown in Fig. 8. Table 1 shows this step-by-step transition state. The OFF state of the excitation trigger is the default state, and the ON state is the switching state or disconnected state.

[0032] [Table 1]

[0033] In the series state (mode 1) during normal use, all the switching relays 21 and the disconnecting relays 26 are OFF. When the balancing mechanism switches to the first stage (mode 2), all the disconnecting relays 26a to 26c are turned ON and disconnected, which divides the cells 11 into groups of two. At the same time, the switching relays 21a, 21c, 21e, and 21g among the switching relays 21, that is, the switching relays 21 connecting the two cells that make up the divided groups, are switched from series (OFF) to parallel (ON). This realizes switching to the wiring of the quarterfinals shown in FIG. 2. In this state, the voltage of each cell 11 is measured, and the current that starts to flow is continuously measured. In each primary battery group, the voltages of the constituent cells 11 try to become equal, so that a current flows from a cell with a higher voltage to a cell with a lower voltage, and the voltage difference between the cells that make up each primary battery group becomes smaller and the current stops flowing. After a certain time has passed, if the current becomes equal to or less than a predetermined value that is small enough to be considered to be zero, it is considered that the voltages have become equal.

[0034] When the voltages between the cells 11 become the same in each primary battery group, the system is switched to the second stage (mode 3). The disconnecting relays 26a and 26c are switched from ON (disconnected) to OFF (connected). This connects the cells 11b and 11c, and the cells 11f and 11g. At the same time, the switching relays 21b and 21f are switched from series (OFF) to parallel (ON). That is, the battery group of the cells 11a and 11b, which was in a disconnected state, and the battery group of the cells 11c and 11d are connected in parallel to form the secondary battery group. Similarly, the battery group of the cells 11e and 11f, which was in a disconnected state, and the battery group of the cells 11g and 11h are switched to parallel and connected to form the secondary battery group. This realizes switching to the wiring for the semi-finals shown in FIG. 3. In this state, the voltage of each cell 11 is measured, and the current that starts to flow is continuously measured. In each secondary battery group, the voltages of the constituent cells 11 attempt to become equal, so that current flows from the higher voltage cell to the lower voltage cell, and the voltage difference between the cells constituting each secondary battery group becomes smaller and the current stops flowing. After a certain time has passed, when the current falls below a certain value that is small enough to be considered zero, the voltages are considered to have become equal.

[0035] When the voltages between the cells 11 become the same in each secondary battery group, the system switches to the third stage (mode 4). The disconnection relay 26b switches from ON (disconnection) to OFF (connection). This connects the cells 11d and 11e, and all the cells are connected. At the same time, the switching relay 21d switches from series (OFF) to parallel (ON). That is, the battery group of the cells 11a to 11d, which was in a disconnected state, and the secondary battery group of the cells 11e to 11h are switched to parallel and connected to form the tertiary battery group. This realizes switching to the wiring to the final shown in FIG. 4. In this state, the voltage of each cell 11 is measured, and the current that starts to flow is continuously measured. In each tertiary battery group, the voltages of the constituent cells 11 try to become equal, so that a current flows from a cell with a higher voltage to a cell with a lower voltage, and the voltage difference between the cells that constitute each tertiary battery group becomes smaller, and the current stops flowing. After a certain time has elapsed, when the current falls below a certain value that is small enough to be considered zero, the voltages are considered to be equal. This completes balancing for the entire battery group.

[0036] The battery group according to the present invention can improve energy efficiency by suppressing heat generation by adjusting the current flowing during balancing. To achieve this, a switching regulator can be provided between the cells 11. The switching regulator divides the connection time by a switch and smoothes it out, thereby suppressing the overall current flow to a specified ratio. A step-down switching regulator can be suitably used as the switching regulator used in this invention. A switching relay 21 is used together with the switching regulator, and the voltage of the cell, cell assembly, or battery set is measured immediately before switching, and the input / output changeover switch is used to switch and connect the terminal of the cell, cell assembly, or battery set with the higher voltage to the input terminal of the step-down switching regulator.

[0037] A connection structure before and after the switching regulator having such an input / output changeover switch will be described below by taking a part of the connection structure as an example. For the battery group consisting of 8 cells shown in FIG. 1, a switching regulator is added to the structure shown in FIG. 5. An example of the structure is shown in FIG. 9. A switching regulator 31a is provided between the cell 11a and the cell 11b. The switching regulator 31a has a positive input terminal 32a+ and a negative input terminal 32a-, and a positive output terminal 33a+ and a negative output terminal 33a-. A switching relay unit 35a consisting of a plurality of relays is configured between the cell 11a and the switching regulator 31a. Also, a switching relay unit 36a consisting of a plurality of relays is configured between the cell 11b and the switching regulator 31a.

[0038] The state shown in FIG. 9 is the default state in which the cell 11a and the cell 11b are connected in series. At this time, the negative pole of the cell 11a and the positive pole of the cell 11b are at the same potential, and the shunt relay unit 35a is controlled so that they are at the same potential as the input terminal 32a+ of the switching regulator 31a. On the other hand, the shunt relay unit 36a is controlled so that the negative pole of the cell 11b is at the same potential as the output terminal 33a-. However, the input terminal 32a- and the output terminal 33a+ of the switching regulator 31a are not connected to any of the terminals of the cells 11, and are open circuits, so that the switching regulator 31a does not function in this state. The cell 11a and the cell 11b are simply connected in series via the shunt relay unit 35a and the shunt relay unit 36a.

[0039] Next, the connection relationship when balancing the cell 11a and the cell 11b in parallel is shown in the examples of Figs. 10 and 11. The step-down switching regulator 31a is operated so that the potential difference Vin on the input side is Vin>Vout with respect to the output side Vout. Here, Vin is the potential difference between the input terminal 32a+ and the input terminal 32a-, and Vout is the potential difference between the output terminal 33a+ and the output terminal 33a-. The connection relationship when the cell 11a has a higher voltage is as shown in Fig. 10, and the connection relationship when the cell 11b has a higher voltage is as shown in Fig. 11. In balancing in the state where the cell 11a has a higher voltage as shown in Fig. 10, the switching relay unit 35a is controlled so that the + pole and - pole of the cell 11a are connected to the input terminal 32a+ and the input terminal 32a- of the switching regulator 31a, respectively. Also, the switching relay unit 36a is controlled so that the positive and negative poles of the cell 11b are connected to the output terminal 33a+ and the output terminal 33a- of the switching regulator 31a, respectively. Conversely, in balancing in a state in which the cell 11b has a higher voltage as shown in FIG. 11, the switching relay unit 35a is controlled so that the positive and negative poles of the cell 11b are connected to the input terminal 32a+ and the input terminal 32a- of the switching regulator 31a, respectively. Also, the switching relay unit 36a is controlled so that the positive and negative poles of the cell 11a are connected to the output terminal 33a+ and the output terminal 33a- of the switching regulator 31a, respectively. In order to make it possible to reverse the connection between the cell 11a and the cell 11b as shown in FIG. 11, this can be realized by an input / output switching relay as described later.

[0040] The switching regulator 31 can control the current using, for example, a PWM method. In both cases of Fig. 10 and Fig. 11, a pulse voltage is applied from the high-voltage cell 11 to the low-voltage cell 11. By smoothing this pulse voltage, a controlled current can be made to flow. The current that flows can be reduced by the proportion of the time that the voltage is on per pulse cycle. By shortening the time that the voltage is applied as much as possible and balancing with a suppressed current, it is possible to suppress the energy that is wasted as heat.

[0041] When the voltages of the two cells 11 are made the same by the switching regulator 31, at the moment of parallel connection, a current flows in an attempt to make the voltages the same. After the circuit is opened, the cell voltage changes by the amount of electrical energy transferred by charging and discharging. Since the cell voltage of an open circuit changes according to the amount of charging and discharging, the voltages do not become the same instantly, but rather transition in stages, for example as shown in Table 2. Assume that at the start of balancing, cell 11a is 4.1V and cell 11b is 3.8V (state 1). The relay is switched to connect the + and - poles of cell 11a to input terminals 32a+ and 32a-. In addition, the + and - poles of cell 11b are connected to output terminals 33a+ and 33a-. At this time, the input (VIN) between the input terminals 32a+ and 32a- is 4.1V, and the switching regulator 31 controls the pulse width so that the output (VOUT) between the output terminals 33a+ and 33a- is slightly higher than the voltage of cell 11b, thereby suppressing the current value (state 2). Eventually, the voltage of cell 11a drops, the voltage of cell 11b rises, and the two voltages approach each other (state 3). In this state, the pulse width is further controlled to adjust VOUT to be slightly higher than that of cell 11b, allowing current to flow while suppressing heat generation. When it is deemed that no current is flowing, or when the voltages of cells 11a and 11b being monitored when the circuit is open become the same, balancing between cells 11a and 11b is completed (state 4).

[0042] [Table 2]

[0043] FIG. 12 shows an example of the connection relationship when the balancing between the cells 11a and 11b (quarter-final) is completed and the cells 11a and 11b are connected in parallel as the first battery group after the semi-final. At this stage, the switching relay unit 35a and the switching relay unit 36a are controlled to connect the cells 11a and 11b without the switching regulator 31a. The positive poles of the cells 11a and 11b are at the same potential as the input terminal 32a+, and the negative poles of the cells 11a and 11b are at the same potential as the output terminal 33a-. Meanwhile, the input terminal 32a- and the output terminal 33a+ are open circuits, as in the case of the series connection (FIG. 9).

[0044] An example of a configuration for realizing the switching relay unit 35a and switching relay unit 36a that realize such switching is shown in Fig. 13. The configurations of the cells 11a and 11b, the switching relay 21a, and the switching regulator 31a are similar to those of the embodiment shown in Fig. 5 and Fig. 9. Furthermore, in this embodiment, four input / output switching relays 41 (41-1a to 41-4a) are attached that correspond to both + side terminals (32a+, 33a+) and both - side terminals (32a-, 33a-) of the input and output of the switching regulator 31a, respectively. The input / output switching relay 41 (41-1a to 41-4a) has an individual terminal 45 (not shown individually, but the corresponding reference numerals are "45-1a to 45-4a". The same applies below) that connects to the cell 11 side, and selection terminals 46 ("46-1a to 46-4a"), 47 ("47-1a to 47-4a") that selectively connect to any of the terminals of the switching regulator 31. Enlarged views of this input / output switching relay 41 are shown in Figs. 14(a) and 14(b). An internal switch 43 is switched by an excitation trigger 42, and the state is switched between a state in which the individual terminal 45 and the selection terminal 46 are connected (Fig. 14(a)) and a state in which the individual terminal 45 and the selection terminal 47 are connected (Fig. 14(b)). In the example shown here, the default is the state shown in Fig. 14(a), and the excitation trigger 42 is in the ON state. Note that the ON / OFF and default may be configured inversely.

[0045] In addition, between the cell 11b and each of the input / output switching relays 41, series-parallel switching relays 51-1a and 51-2a are provided. Enlarged views of the series-parallel switching relays are shown in Figs. 15(a) and 15(b). The series-parallel switching relay 51 also has an independent terminal 55 and selection terminals 56 and 57, similar to the input / output switching relay 41, and is switched by an internal switch 53 that is switched by an excitation trigger 52 between a state in which the independent terminal 55 and the selection terminal 56 are connected (Fig. 15(a)) and a state in which the independent terminal 55 and the selection terminal 57 are connected (Fig. 15(b)). The independent terminal 55-1a of the series-parallel switching relay 51-1a is connected to the positive pole of the cell 11b, and the independent terminal 55-2a of the series-parallel switching relay 51-2a is connected to the negative pole of the cell 11b. In the example shown here, the default is the state shown in Fig. 15(a), and the excitation trigger 42 is in the ON state. The ON / OFF and default may be reversed.

[0046] The part surrounded by a bold dashed line in FIG. 13 realizes the switching of the switching relay unit 35a and the switching relay unit 36a in the examples of FIGS. 9 to 12 between cell 11a and cell 11b. This step-by-step transition state is shown in Table 3. The ON state of the excitation trigger is the default state, and the OFF state is the switching state. However, as in Table 1, the default for the switching relay 21a is OFF, which connects cell 11a and cell 11b in series.

[0047] [Table 3]

[0048] In the series state (mode 1) during normal use shown in FIG. 13, all the switching relays 21 are OFF, while the input / output switching relays 41-1a to 41-4a and the series-parallel switching relays 51-1a and 51-2a are all ON. In this state, the negative pole of the cell 11a is connected to the input / output switching relay 41-1a and the input / output switching relay 41-3a via the switching relays 21a (24-2a to 25-1a), but the part (45-1a, 43-1a, 46-1a, 47-3a) connected from the input / output switching relay 41-1a is connected to the input terminal 32a+ of the switching regulator 31a. These are at the same potential as the negative pole of the cell 11a. On the other hand, it is also connected to the selection terminal 56-1a of the series-parallel switching relay 51-1a, and is connected to the positive pole of the cell 11b via the switch 53-1a and the independent terminal 55-1a. On the other hand, the output terminal 33a+ of the switching regulator 31a is connected to the selection terminal 47-1a of the input / output switching relay 41-1a and the selection terminal 46-3a of the input / output switching relay 41-3a, and the selection terminal 46-3a is connected to the independent terminal 45-3a via the switch 43-3a and to the selection terminal 57-1a of the series / parallel switching relay 51-1a, but these are electrically floating. Symmetrically, the negative pole of the cell 11b is connected to the independent terminal 55-2a of the series / parallel switching relay 51-2a and to the selection terminal 56-2a via the switch 53-2a, and the part (45-4a, 43-4a, 46-4a, 47-2a) connected from there to the input / output switching relay 41-4a is connected to the output terminal 33a- of the switching regulator 31a. On the other hand, the input terminal 32a- of the switching regulator 31a is connected to a selection terminal 47-4a of an input / output switching relay 41-4a and a selection terminal 46-2a of an input / output switching relay 41-2a, which is connected from the selection terminal 46-2a to an independent terminal 45-2a via a switch 43-2a, to a selection terminal 57-2a of a series-parallel switching relay 51-2a, and also to a right-side terminal 25-2a of the switching relay 21a, which are electrically floating.

[0049] In this configuration, the connection when balancing cells 11a and 11b in parallel changes depending on whether the voltages of cells 11a and 11b are high or low, so as to selectively realize the configurations shown in Figures 10 and 11.

[0050] When cell 11a has a higher voltage than cell 11b, the excitation trigger of each relay switches as shown in FIG. 16 (mode 2A). Specifically, from mode 1, the switching relay 21a and the series-parallel switching relay 51-1a switch. This results in the wiring as shown in FIG. 10. The + and - poles of cell 11a, which is the high voltage, are connected to input terminals 32a+ and 32a- of the switching regulator 31a.

[0051] On the other hand, when cell 11b has a higher voltage than cell 11a, the excitation trigger of each relay switches as shown in FIG. 17 (mode 2B). Specifically, from mode 1, in addition to switching relay 21a and series-parallel switching relay 51-1a switching, all input / output switching relays 41-1a to 41-4a are turned OFF. This realizes the wiring as shown in FIG. 11. The + and - poles of cell 11b, which is the high voltage, are connected to input terminals 32a+ and 32a- of switching regulator 31a.

[0052] In the state of FIG. 16 or FIG. 17, the current suppressed by the switching regulator 31a gradually flows, and balancing is performed, so that the voltages of the cells 11a and 11b become equal. In the subsequent balancing between the semi-final (mode 3) and the final (mode 4), the switching regulator 31a is not operated, and the cells 11a and 11b are simply switched to a parallel connection. This state is shown in FIG. 18. The input terminal 32a- and the output terminal 33a+ of the switching regulator 31a are in an electrically floating state. In addition, the input terminal 32a+ is at the same potential as the positive poles of both the cells 11a and 11b, and the output terminal 33a- is at the same potential as the negative poles of both the cells 11a and 11b.

[0053] In proceeding with the balancing, switching similar to that of the switching regulator 31a is also performed in the switching regulators 31c, 31e, and 31g provided between the cells 11 that will form the battery pairs in the quarter-finals.

[0054] In the semi-final (mode 3), the switching regulator 31a does not operate, but balancing is performed in the same manner between the battery set of cells 11a and 11b and the battery set of cells 11c and 11d. Therefore, before and after the switching regulator 31b, which is provided with similar wiring between cells 11b and 11c, the switching regulator is in a disconnected state in the quarter-final (mode 2), and in the semi-final (mode 3), the relay is switched depending on the voltage of the battery set as in modes 2A and 2B in Table 3 above. The same applies to the switching regulator 31f between cells 11f and 11g.

[0055] In the final (mode 4), the switching regulators 31b and 31f are connected in a simple parallel state, similar to mode 4 in Table 3. Balancing is then performed between the battery set of cells 11a-11d and the battery set of cells 11e-11h in a similar manner. Therefore, the switching regulator 31d, which is provided with similar wiring between cells 11d and 11e, is in a disconnected state in the quarter-final (mode 2) and semi-final (mode 3), and in the final (mode 4), the relay is switched according to the voltage of the secondary battery set, as in modes 2A and 2B in Table 3 above.

[0056] The above embodiment has been described as an example of eight cells, but when the number of cells is a power of two, balancing is possible by providing a similar configuration consisting of a relay and a switching regulator 31 between each cell and switching the relay in the same manner. That is, in the normal state of the battery group, the switching regulator 31 is electrically floating, and the switching regulator 31 is not operating and connected in series (mode 1 in Table 3). When balancing is started, each cell is electrically disconnected, and the relays before and after the switching regulator 31 at the boundary between the cells or battery sets where the voltage is to be made uniform are connected as shown in mode 2A or mode 2B in Table 3. In the new battery sets where the voltages are now uniform, the switching regulators 31 in those battery sets are connected as shown in modes 3 and 4 in Table 3.

[0057] The task of making the voltages of the batteries uniform by implementing the balancing mechanism in the battery group 10 according to the present invention is desirably performed in a maintenance mode in which no current flows through the load mechanism 6 driven by the battery group 10. In Tables 1 and 3 above, mode 1 is the normal mode, and the maintenance mode corresponds to modes 2 to 4.

[0058] FIG. 19 shows an example of the relationship between the battery group 10 in the normal mode, the charging system 5 that charges the battery group 10, and the load mechanism 6 that uses the power of the battery group 10. In the normal mode, the cells 11a to 11N that make up the battery group 10 are connected in series, and charging from the charging system 5 and discharging to the load mechanism 6 are performed collectively (FIG. 19(a)). When transitioning to the maintenance mode, these charging system 5 and load mechanism 6 are temporarily separated (FIG. 19(b)). In this state of being separated from the charging system 5 and load mechanism 6, the connection relationship of the cells 11 that make up the battery group 10 is controlled as shown in the above-mentioned FIG. 10 to FIG. 16 to FIG. 19(c)→(d)→(e), mode 2→mode 3→mode 4), and balancing is performed to make the voltages of the cells 11 uniform. During this time, the charging system 5 and the load mechanism 6 remain separated. Once the voltages of all the cells have been equalized in mode 4 in Figure 19(e), the connection is returned from parallel to series as shown in Figure 19(b), and then the charging system 5 and load mechanism 6 are connected as shown in Figure 19(a), the maintenance mode is terminated, and the mode is returned to normal.

[0059] It is desirable to switch to the maintenance mode as described above during the off timer period set in advance in the battery-powered system including the battery group, so that no current flows through the load mechanism 6. The off timer should be set to a time period when the battery-powered system can be stopped without causing any problems in the environment in which the battery-powered system is used, such as non-operational hours in a factory or quiet hours for a server. For example, it can be set to two hours from 1:00 am to 3:00 am in a day, or ten hours during the day on a regular holiday in a week. During the off timer period, the battery group 10 and the load mechanism 6 are separated as shown in FIG. 19(b), and then the above-mentioned balancing is performed.

[0060] Balancing uses the off-timer's available time as long as possible and controls to suppress the current value flowing in each mode. In the battery group 10, the control device (not shown) stores a map of the time required to transfer 1 Ah in advance. A map is also stored to estimate the amount of electrical energy (Ah) stored at that time from the voltage of each cell 11. Then, the voltage of each cell 11 is monitored, and the minimum time required to transfer the amount of electrical energy (Ah) that must be transferred to make the voltages the same is determined from the voltage and voltage difference. On the other hand, the pulse width of the switching regulator is controlled so that the current flowing is small so that it takes as long as possible to transfer the amount of electrical energy from the off-timer's available time.

[0061] The battery group implementing the balancing mechanism according to the present invention can be applied to, for example, a plug-in hybrid vehicle (PHEV) that can be externally charged or externally powered. The charging system 5 can be an external power source or can generate electricity using an engine. The load mechanism 6 can be the overall mechanism of the vehicle, including driving. It is possible to reduce the load on the battery, which is a battery group that has many cells and is operated for a long period of time, and this can also contribute to extending the battery life. [Explanation of symbols]

[0062] 5 Charging system 6 Load mechanism 10 battery group 11, 11a, 11b, 11c, 11d, 11e, 11f, 11g, 11h cells 21, 21a, 21b, 21c, 21d, 21e, 21f, 21g Switching relays 22 Excitation Trigger 23, 23-1, 23-2 Switch 24, 24-1, 24-2, 24-3 Left terminal 25, 25-1, 25-2 Right side terminal 26, 26a, 26b, 26c Disconnect relays 27 Excitation Trigger 28, 28-1, 28-2 Switch 29, 29-1, 29-2 Left side terminal 30, 30-1, 30-2 Right side terminal 31, 31a, 31b, 31c, 31d, 31e, 31f, 31g Switching regulator 32+, 32-, 32a+, 32a- Input terminals 33+, 33-, 33a+, 33a- output terminal 35, 35a, 36, 36a Replacement Relay Section 41, 41-1a, 41-2a, 41-3a, 41-4a Input / Output switching relay 42 Excitation Trigger 43, 43-1a, 43-2a, 43-3a, 43-4a Switch 45, 45-1a, 45-2a, 45-3a, 45-4a Single terminal 46, 46-1a, 46-2a, 46-3a, 46-4a, 47, 47-1a, 47-2a, 47-3a, 47-4a selection terminal 51, 51-1a, 51-2a Series / parallel changeover relay 52 Excitation Trigger 53, 53-1a, 53-2a Switch 55, 55-1a, 55-2a, 55-3a, 55-4a Single terminal 56, 56-1a, 56-2a, 56-3a, 56-4a, 57, 57-1a, 57-2a, 57-3a, 57-4a selection terminal

Claims

1. A battery group in which batteries, which are cells or cell combinations, are connected in series, the battery group has a balancing mechanism for equalizing the voltages of the individual batteries constituting the battery group, The balancing mechanism performs the following operations: (a) switching the connection between the batteries from series to parallel for each pair of adjacent batteries so that the voltages of the two batteries connected in parallel are the same; (b) combining two batteries or battery sets whose voltages have been made the same in the previous step into a next battery set, and connecting two adjacent next battery sets in parallel so that the voltages of the two next battery sets constituting each set connected in parallel are the same; (c) Repeating (b) above until all of the batteries constituting the battery group are connected in parallel and the voltages of the batteries are the same. battery group.

2. The battery pack according to claim 1 , wherein the balancing mechanism comprises a switching regulator between each of the batteries.

3. 3. The battery group according to claim 2, wherein the switching regulator is a step-down type, and the balancing mechanism includes an input / output changeover switch for connecting the battery or battery set having a higher voltage to an input side of the switching regulator.

4. A battery pack according to any one of claims 1 to 3, and a load mechanism driven by the battery pack, The load mechanism has an off timer that is set so that no current flows, Only during a certain period of time of the off timer, the battery group and the load mechanism are electrically separated, During a certain period of time of the off timer, the voltage of the higher of the two batteries or battery sets is controlled by pulse width to perform the operation of the balancing mechanism. Battery powered system.

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