Battery module, battery cell, and converter device

Abstract

The battery module of the present application has: a battery pack composed of battery cells with a series number s and a parallel number p (s is an integer of 1 or more, and p is an integer of 1 or more); and a bidirectional DC / DC converter capable of flowing current in either direction, which generates a voltage nV (n is -1 or 2) with respect to the voltage V of the battery pack.

Description

Technical Field

[0001] The present invention relates to a battery module formed by connecting multiple battery cells in series and / or in parallel, a battery cell formed by connecting multiple battery modules, and a converter device for balancing. Background Technology

[0002] In recent years, the applications of secondary batteries such as lithium-ion batteries have rapidly expanded to include energy storage devices combined with new energy systems such as solar cells and wind power generation, as well as automotive batteries. When multiple energy storage elements, such as cell units (hereinafter appropriately referred to as battery cells), are used to generate high output power, a structure is adopted in which multiple battery modules are connected in series. In the case of cylindrical batteries, one cylinder is the battery cell; in the case of laminated batteries, one laminated pack is the battery cell. A battery module includes a battery pack, which is formed by connecting multiple, for example, four battery cells in parallel to form a battery block, and connecting multiple battery blocks in series as a whole, having positive and negative terminals. Furthermore, there may also be a structure with one parallel connection and one series connection, i.e., a battery module with only one battery cell.

[0003] Furthermore, a battery cell is formed by connecting multiple battery modules in series. Within a battery cell, if voltage deviations occur between battery modules, it can lead to problems such as the battery modules not being able to fully utilize their capabilities or having shorter lifespans.

[0004] Currently, active balancing circuits for controlling the balance between battery cells have been proposed. For example, Patent Document 1 describes a power supply system in which multiple voltages are output through the connection points of multiple battery cells constituting a battery module, and a balancing circuit is provided to correct for deviations in the charging and discharging states of each battery cell. This balancing circuit is described as a switched-capacitor structure consisting of multiple capacitors and multiple switches.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2009-247145 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] Patent Document 1 describes the correction of deviations in the charging and discharging states of battery cells within a battery module, not the correction of deviations between battery modules. Furthermore, when the battery cells described in Patent Document 1 are replaced with battery modules, there are difficulties in handling and flexibly applying the active balancing adjustment circuit when the number of battery modules is changed to connect the active balancing adjustment circuit between modules.

[0010] Therefore, the object of the present invention is to provide a flexible battery module, battery cell, and converter device that can easily adapt to changes in the number of connected battery modules.

[0011] Technical solutions for solving the problem

[0012] This invention relates to a battery module, comprising:

[0013] The battery pack consists of battery cells connected in series with a number of 's' and in parallel with a number of 'p' (where 's' is an integer greater than or equal to 1, and 'p' is an integer greater than or equal to 1); and

[0014] A converter enables current to flow in any direction and performs bidirectional DC / DC conversion.

[0015] The converter generates a voltage nV relative to the battery pack voltage V (n is -1 or 2).

[0016] This invention relates to a battery cell that connects multiple battery modules with converters that generate -V voltage in series, as described above.

[0017] The -V voltage generated by one battery module is supplied to the negative terminal of another battery module connected to the negative terminal side of that battery module.

[0018] This invention relates to a battery cell that connects multiple battery modules, each having a converter that generates a 2V voltage, in series.

[0019] A 2V voltage generated by one battery module is supplied to the positive terminal of another battery module connected to the positive terminal of that battery module.

[0020] This invention relates to a converter device comprising: a positive terminal and a negative terminal, which are connected to the positive and negative terminals of a battery module; and

[0021] The converter enables current to flow in any direction and generates a voltage nV (n is -1 or 2) relative to the battery pack voltage V of the battery module.

[0022] Invention Effects

[0023] According to at least one embodiment, the invention can flexibly accommodate changes in the number of battery modules connected in series. Furthermore, the invention is not necessarily limited to the effects described herein, but may include any effect described in this specification or effects of a different nature. Additionally, the effects illustrated in the following description do not limit the interpretation of the invention. Attached Figure Description

[0024] Figure 1 A and Figure 1 B is a connection diagram and a waveform diagram of the driving waveform for an example of an existing balanced circuit.

[0025] Figure 2 This is a block diagram of the first embodiment of the present invention.

[0026] Figure 3 This is a connection diagram of an example of a converter that can be used in this invention.

[0027] Figure 4 This is a connection diagram of the circuit structure used in the simulation of this invention.

[0028] Figure 5 It is a graph representing the results of the simulation.

[0029] Figure 6 This is a block diagram of the second embodiment of the present invention.

[0030] Figure 7 This is a block diagram of the third embodiment of the present invention.

[0031] Figure 8 This is a block diagram of the fourth embodiment of the present invention.

[0032] Figure 9 This is a block diagram of the fifth embodiment of the present invention.

[0033] Figure 10 This is a block diagram of the sixth embodiment of the present invention.

[0034] Figure 11 This is a block diagram of the seventh embodiment of the present invention. Detailed Implementation

[0035] The embodiments described below are preferred examples of the present invention, with various technically preferred limitations added. However, unless otherwise specified in the following description, the scope of the present invention is not limited to these embodiments.

[0036] Before describing the present invention, refer to Figure 1 A and Figure 1 B illustrates an example of an existing active balancing circuit. Figure 1 A is a connection diagram showing the structure of an active balancing circuit using a switched capacitor method. Figure 1 B is an example of a driving waveform.

[0037] For example, four battery cells B1, B2, B3, and B4 are connected in series to form a battery module. The positive side of battery cell B1 is connected to the upper terminal of switch SW1, and the negative side of battery cell B1 is connected to the lower terminal of switch SW1 and the upper terminal of switch SW2. Similarly, the positive and negative sides of battery cell B2 are connected to the upper and lower terminals of switch SW2, respectively; the positive and negative sides of battery cell B3 are connected to the upper and lower terminals of switch SW3, respectively; and the positive and negative sides of battery cell B4 are connected to the upper and lower terminals of switch SW4, respectively.

[0038] The terminals selectively connected to the upper and lower terminals of switch SW1 (appropriately referred to as movable terminals) are connected to one electrode of capacitor C1. Capacitors C2 and C3 are connected in series with capacitor C1. The movable terminal of switch SW2 is connected to the midpoint of the connection between capacitors C1 and C2, the movable terminal of switch SW3 is connected to the midpoint of the connection between capacitors C2 and C3, and the movable terminal of switch SW4 is connected to the other electrode of capacitor C3.

[0039] The driving waveform generated by the oscillator OSC ( Figure 1 B) Control switches SW1-SW3. In the negative-side interval of the drive waveform, the movable terminals of switches SW1-SW4 are connected to the lower terminal; in the positive-side interval of the drive waveform, the movable terminals of switches SW1-SW4 are connected to the upper terminal. In the interval where the movable terminals of switches SW1-SW4 are connected to the lower terminal, the voltage of battery cells B2, B3, and B4 is supplied to capacitors C1, C2, and C3. In the negative-side interval of the next drive waveform, the movable terminals of switches SW1-SW4 are connected to the upper terminal; in this interval, the voltage of battery cells B1, B2, and B3 is supplied to capacitors C1, C2, and C3.

[0040] Therefore, in one cycle of the driving waveform, current flows through capacitor C1 to make the voltages of battery cells B1 and B2 equal, through capacitor C2 to make the voltages of battery cells B2 and B3 equal, and through capacitor C3 to make the voltages of battery cells B3 and B4 equal. After a specified period, the voltages of B1 to B4 become equal.

[0041] The existing active balancing circuit using switched capacitors is used to equalize the voltage of the battery cells within a battery module, but not to equalize the voltage between the battery modules themselves. Furthermore, changing the number of battery cells requires a complete overhaul of the switching and capacitor connections, resulting in a lack of flexibility. The present invention, as described below, solves these problems.

[0042] Reference Figure 2 and Figure 3 The first embodiment of the present invention will be described. A battery module M is constituted by a battery pack BT and a converter CNV. Multiple battery cells (e.g., lithium-ion secondary batteries) in the battery pack BT are connected in series and / or in parallel. The battery pack BT has a positive terminal ta (voltage V) and a negative terminal tb. The converter CNV is connected to the positive terminal ta of the battery pack BT and outputs a voltage of nV (n is -1 or 2) to the converter terminal tc. The number of battery cells in the battery pack BT connected in series is s (s is an integer greater than or equal to 1), and the number of cells connected in parallel is p (p is an integer greater than or equal to 1). The converter CNV is a bidirectional DC / DC converter capable of allowing current to flow in any direction.

[0043] As an example, the battery pack (BT) and converter (CNV) are housed in a common outer casing. Thus, a battery cell is formed by connecting battery modules, which are integrally composed of the battery pack (BT) and converter (CNV), in series. This invention allows for flexible adaptation to changes in the number of battery modules when actively balancing multiple battery modules within the battery cell.

[0044] Reference Figure 3 An example of converter CNV (an example of output V) is described. Switches SW11 and SW21 are connected in series between terminal V+ and ground, and switches SW12 and SW22 are connected in series between terminal GND and converter terminal tc (VOUT). A capacitor Cp is connected between connection point t1 of switches SW11 and SW21 and connection point t2 of switches SW12 and SW22.

[0045] Control signals for switches SW11 and SW12 are generated by the oscillator OSC. These control signals, inverted by the inverter INV, control switches SW21 and SW22. During the period when the OSC output is high, the linked switches SW11 and SW12 are turned on, and the linked switches SW21 and SW22 are turned off. Therefore, terminal t1 is connected to terminal V+, and terminal t2 is connected to terminal GND. As a result, the voltage V from terminal V+ is stored in capacitor Cp.

[0046] Next, when the output of the oscillator OSC goes low, the linked switches SW11 and SW12 open, and the linked switches SW21 and SW22 close. Therefore, terminal t1 is grounded, and terminal t2 is connected to terminal tc. As a result, the voltage stored in capacitor Cp is inverted and output from terminal tc as -V. Therefore, both V and -V can be generated as output voltages by the converter CNV.

[0047] Simulations using LTspice (a registered trademark) confirmed that active balancing adjustments can be performed using the CNV converter. Figure 4 It is the circuit structure used in the simulation, using four battery cells (or battery modules) B1, B2, B3, B4 connected in series and three converters CNV1, CNV2, CNV3.

[0048] A positive terminal ta is led out from the positive side of battery cell B1, and a negative terminal tb is led out from the negative side of battery cell B4. The positive side of battery cell B1 is connected to terminal V+ of converter CNV1, and the negative side of battery cell B1 is connected to terminal GND of converter CNV1. The negative side of battery cell B2 is connected to terminal tc (VOUT) of converter CNV1. In the same relationship, battery cells B2 and B3 are connected to converter CNV2, and battery cells B3 and B4 are connected to converter CNV3.

[0049] When a voltage V is applied to terminal V+, the voltage difference between terminal GND and terminal tc (VOUT) of each converter is V. When there is a voltage difference between the battery cell directly below the current cell and the voltage of the current cell, since the converter is bidirectional, the current flows in a manner that results in the same voltage. Furthermore, in the case where the converter generates 2V, the voltage difference between terminal tc (VOUT) and terminal V+ is V. When there is a voltage difference between this voltage and the voltage of the battery cell directly above it, since the converter is bidirectional, the current flows in a manner that results in the same voltage.

[0050] As an example, with the initial voltage of battery cell B1 at 4.0V and the voltages of battery cells B2, B3, and B4 at 4.0V, 3.8V, and 4.0V respectively, the simulation results are as follows: Figure 5 The voltage change over time is shown. Battery cells B1-B4 are denoted as 0.5F capacitors (equivalent to approximately 0.5mAh), simulating the internal resistance of the capacitors in the battery cells as 50mΩ and the parallel capacitance as 1mF. A reverse charge pump IC (LTC660) from Linear Technology Corporation was used as a converter capable of generating -V. In this converter, the capacitance of capacitor Cp was set to 150μF. A time-varying simulation was performed under these conditions to calculate how the voltage of each battery cell changed up to 12 minutes later.

[0051] As shown by curve P1, the voltage of battery cell B1 exhibits the following behavior: after a temporary decrease, it increases again after approximately 2 minutes. Then, it converges to its original value of 4.0V. As shown by curve P2, the voltage of battery cell B2 exhibits the following behavior: it monotonically increases and converges to 4.0V. As shown by curve P3, the voltage of battery cell B3 exhibits the following behavior: it monotonically decreases and converges to 4.0V. As shown by curve P4, the voltage of battery cell B4 exhibits the following behavior: after a temporary increase, it decreases again after approximately 2 minutes. Then, it converges to its original value of 4.0V. Although the initial voltage of battery cells B1 and B4 is 4.0V, they converge to 4.0V after the temporary decrease and increase. This is because... Figure 4 The structure can only be homogenized with the nearest battery cell.

[0052] The results show that the voltage of all battery cells converges to 4.0V. In this simulation, considering that all battery cells have equal capacity, the charge stored in the capacitor is proportional to the voltage, and the average initial voltage of each battery cell is 4.0V, the convergence of the voltage of all battery cells to 4.0V implies that charge equalization has been performed.

[0053] According to a first embodiment of the present invention, since it has a converter terminal for outputting -V or 2V, it is possible to flexibly add or remove a battery module. Furthermore, it has the advantage of not requiring a separate balancing circuit to connect to all battery modules.

[0054] Figure 6 The structure of a second embodiment of the present invention is shown. The second embodiment differs from the first embodiment in that the converter CNV has an ON / OFF control terminal. The switching on / off of the converter CNV is performed by controlling the switching on / off of the oscillator OSC within the converter CNV. A balancing operation is performed when the converter CNV is on, and no balancing operation is performed when the converter CNV is off. According to the second embodiment, power consumption can be suppressed by disconnecting the converter CNV.

[0055] Figure 7 The structure of the third embodiment of the present invention is shown. In the third embodiment, the converter CNV outputs a -V structure. Additionally, voltage measuring devices DT1 and DT2 are provided. Voltage measuring device DT1 measures the voltage between the positive and negative terminals of the battery module, and voltage measuring device DT2 measures the voltage between the converter terminal of the converter CNV and the negative terminal of the battery module. A voltage comparator CMP is provided to compare the voltages measured by voltage measuring devices DT1 and DT2. The output of voltage comparator CMP is supplied to the on / off control terminal of the converter CNV.

[0056] The voltage comparator CMP controls the converter CNV in such a way that it turns on the converter CNV when the ratio ΔV of the voltages measured by voltage measuring instruments DT1 and DT2 is above a threshold, and turns off the converter CNV when the ratio ΔV is below the threshold. For example, a value of about 2% is used as the threshold. This third embodiment turns on the converter CNV only when balancing is required, thus suppressing power consumption compared to a structure that always turns on the converter CNV.

[0057] Figure 8 The structure of the fourth embodiment of the present invention is shown. In the fourth embodiment, the converter CNV outputs 2V. Additionally, voltage measuring devices DT1 and DT3 are provided. Voltage measuring device DT1 measures the voltage between the positive and negative terminals of the battery module, and voltage measuring device DT3 measures the voltage between the converter terminal of the converter CNV and the positive terminal of the battery module. A voltage comparator CMP is provided to compare the voltages measured by voltage measuring devices DT1 and DT3. The output of voltage comparator CMP is supplied to the on / off control terminal of the converter CNV.

[0058] The voltage comparator CMP controls the converter CNV by turning it on when the ratio ΔV of the voltages measured by voltage measuring devices DT1 and DT3 is above a threshold, and turning it off when the ratio ΔV is below the threshold. This fourth embodiment, like the third embodiment, only turns on the converter CNV when balancing is required, thus reducing power consumption compared to a structure where the converter CNV is always on.

[0059] Figure 9 The structure of the fifth embodiment of the present invention is shown. For example... Figure 9 As shown, a battery unit U is constructed by connecting m (m is an integer of 2 or more), for example, three battery modules (equipped with a converter CNV that generates -V) of the third embodiment described above in series. Battery modules M1, M2, and M3 are respectively connected to... Figure 7 The battery modules shown have the same structure, therefore the corresponding structural elements are labeled with the same reference figures. Additionally, ta1, ta2, and ta3 represent the positive terminals of each battery module, tb1, tb2, and tb3 represent the negative terminals, and tc1, tc2, and tc3 represent the converter terminals.

[0060] The positive terminal ta1 of battery module M1 is led out as the positive terminal of battery unit U, and the negative terminal tb3 of battery module M3 is led out as the negative terminal of battery unit U. The negative terminal tb1 is connected to the positive terminal ta2, and the negative terminal tb2 is connected to the positive terminal ta3. Battery modules M1 to M3 are connected in series.

[0061] Furthermore, the converter terminal tc1 (voltage of -V) of battery module M1 is connected to the negative terminal tb2 of another battery module M2, which is connected to the negative terminal tb1 side of battery module M1. Through this connection, when the converter CNV is turned on, the current corresponding to the voltage difference between battery modules M1 and M2 flows from the converter CNV to the battery pack BT of battery module M1.

[0062] Furthermore, the converter terminal tc2 (voltage -V) of battery module M2 is connected to the negative terminal tb3 of another battery module M3, which is connected to the negative terminal tb2 side of battery module M2. Through this connection, when the converter CNV is turned on, the current corresponding to the voltage difference between battery modules M2 and M3 flows from the converter CNV to the battery pack BT of battery module M2. This fifth embodiment can make the voltages of the three battery modules M1 to M3 approximately equal over time.

[0063] Figure 10 The structure of the sixth embodiment of the present invention is shown. For example... Figure 10 As shown, a battery unit U is constructed by connecting m (m is an integer of 2 or more), for example, three battery modules (equipped with a converter CNV that generates 2V) of the fourth embodiment described above in series. Battery modules M1, M2, and M3 are respectively connected to... Figure 8 The battery modules shown have the same structure, therefore the corresponding structural elements are labeled with the same reference figures. Additionally, ta1, ta2, ta3 represent the positive terminals of each battery module, tb1, tb2, tb3 represent the negative terminals, and tc1, tc2, tc3 represent the converter terminals (output 2V).

[0064] The positive terminal ta of battery module M1 is led out as the positive terminal of battery unit U, and the negative terminal tb3 of battery module M3 is led out as the negative terminal of battery unit U. The negative terminal tb1 is connected to the positive terminal ta2, and the negative terminal tb2 is connected to the positive terminal ta3. Battery modules M1 to M3 are connected in series.

[0065] Furthermore, the converter terminal tc2 (2V voltage) of battery module M2 is connected to the positive terminal ta1 of another battery module M1, which is connected to the positive terminal ta2 side of battery module M2. Through this connection, when the converter CNV is turned on, the current corresponding to the voltage difference between battery modules M1 and M2 flows from the converter CNV to the battery pack BT of battery module M2.

[0066] Furthermore, the converter terminal tc3 (2V voltage) of battery module M3 is connected to the positive terminal ta2 of another battery module M2, which is connected to the positive terminal ta3 side of battery module M3. Through this connection, when the converter CNV is turned on, the current corresponding to the voltage difference between battery modules M2 and M3 flows from the converter CNV to the battery pack BT of battery module M3. This sixth embodiment can make the voltages of the three battery modules M1 to M3 approximately equal over time.

[0067] Figure 11 The structure of the seventh embodiment of the present invention is shown. In the above embodiment, the battery module respectively includes a converter CNV, a voltage comparator CMP, and voltage measuring devices DT1 and DT2; however, as Figure 11 As shown, the battery module and converter device can also be structured independently. With such a structure, the converter device can be connected to an existing module later.

[0068] The embodiments of the present invention have been described in detail above, but are not limited to the above embodiments. Various modifications can be made according to the technical concept of the present invention. In addition, one or more of the modifications can be appropriately combined. Furthermore, the structure, method, process, shape, material, and numerical values ​​of the above embodiments can be combined with each other as long as they do not depart from the spirit of the present invention.

[0069] Explanation of reference numerals in the attached figures

[0070] M…battery module, BT…battery pack, CNV…converter, ta…positive terminal, tb…negative terminal, tc…converter terminal.

Claims

1. A battery unit comprising multiple battery modules connected in series, wherein the battery modules include: The battery pack consists of battery cells connected in series with a number of 's' and in parallel with a number of 'p', where 's' is an integer greater than or equal to 1, and 'p' is an integer greater than or equal to 1; and A bidirectional DC / DC converter enables current to flow in any direction. The converter generates a voltage of -V relative to the voltage V of the battery pack. The -V voltage generated by one battery module is supplied to the negative terminal of another battery module connected to the negative terminal side of that battery module.

2. The battery cell according to claim 1, wherein, The converters of each battery module are switched on / off.

3. The battery cell according to claim 2, wherein, The battery module has the following features: The first voltage measuring unit measures the voltage between the negative terminal and the positive terminal; The second voltage measuring unit measures the voltage between the converter terminal and the negative terminal; and A voltage comparator compares the voltage measured by the first voltage measuring unit with the voltage measured by the second voltage measuring unit. The battery module is controlled as follows: when the voltage ratio detected by the voltage comparator is above a threshold, the converter is turned on to generate voltage -V; when the voltage ratio detected by the voltage comparator is less than the threshold, the converter is turned off to stop generating voltage -V.

4. A battery unit comprising multiple battery modules connected in series, wherein the battery modules include: The battery pack consists of battery cells connected in series with a number of 's' and in parallel with a number of 'p', where 's' is an integer greater than or equal to 1, and 'p' is an integer greater than or equal to 1; and A bidirectional DC / DC converter enables current to flow in any direction. The converter generates a voltage of 2V relative to the voltage V of the battery pack. A 2V voltage generated by one battery module is supplied to the positive terminal of another battery module connected to the positive terminal of that battery module.

5. The battery cell according to claim 4, wherein, The converters of each battery module are switched on / off.

6. The battery cell according to claim 5, wherein, The battery module has the following features: The first voltage measuring unit measures the voltage between the negative terminal and the positive terminal; The third voltage measuring unit measures the voltage between the converter terminal and the positive terminal; and A voltage comparator compares the voltage measured by the first voltage measuring unit with the voltage measured by the third voltage measuring unit. The battery module is controlled as follows: when the voltage ratio detected by the voltage comparator is above a threshold, the converter is turned on to generate a voltage of 2V; when the voltage ratio detected by the voltage comparator is less than the threshold, the converter is turned off to stop generating a voltage of 2V.

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