Battery system

Abstract

To prevent a battery from being exposed to high temperature in a battery system having a cell balance means.SOLUTION: The battery system has a cell balance means for controlling charge and discharge of a plurality of battery cells to equalize the voltage of each battery cell. The battery system includes a control unit that charges and discharges each battery cell to equalize the voltages of the plurality of battery cells based on a voltage difference between the battery cells, a cooling unit that is provided in the vicinity of each battery cell and is connected to each battery cell, and a switch unit that switches between conduction and non-conduction between each battery cell and the cooling unit. When the voltages of the plurality of battery cells are equalized, the control unit switches the switch unit to the conductive state and operates the switch unit when the power discharged from each battery cell exceeds a predetermined value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This specification discloses a technology relating to a battery system. [Background technology]

[0002] Patent Document 1 discloses a battery system with multiple battery cells that has a cell balancing means for monitoring the voltage of each battery cell and equalizing the voltage of each battery cell. In Patent Document 1, switching elements are connected in parallel to each battery cell, and each battery cell is discharged based on the voltage difference between the battery cells to equalize the voltages of the multiple battery cells. In addition, the battery system in Patent Document 1 detects the temperature of a circuit board on which a circuit for detecting the voltage of each battery cell is mounted, and performs cell balancing control for each battery cell taking the circuit board temperature into consideration. This prevents damage to circuit elements, malfunction, etc. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-115100 Summary of the Invention [Problem to be solved by the invention]

[0004] As described in Patent Document 1, cell balancing control causes a battery system to generate heat as the battery cells discharge. Heat generated by a battery system not only has a negative effect on the circuit board, but also exposes the batteries themselves to high temperatures, which can cause a deterioration in their performance. Therefore, even in battery systems that perform cell balancing control, a technology is needed to prevent batteries from being exposed to high temperatures. The purpose of this specification is to provide a technology for preventing batteries from being exposed to high temperatures in a battery system having a cell balancing means. [Means for solving the problem]

[0005] A first technology disclosed in this specification is a battery system having a cell balancing means for controlling the charging and discharging of a plurality of battery cells to equalize the voltages of the battery cells, and may include: a control unit that charges and discharges each battery cell based on a voltage difference between the battery cells to equalize the voltages of the plurality of battery cells; a cooling unit that is provided near each battery cell and connected to each battery cell; and a switch unit that switches between conduction and non-conduction between each battery cell and the cooling unit. In this battery system, the control unit may switch the switch unit to a conductive state and operate the switch unit when the power discharged from each battery cell during equalization of the voltages of the plurality of battery cells exceeds a predetermined value.

[0006] The second technology disclosed in this specification is a battery system of the first technology, further comprising a temperature detection unit provided in the vicinity of each battery cell and detecting the temperature of each battery cell, and the control unit may switch the switch unit to a conductive state and activate the switch unit when the temperature detected by the temperature detection unit exceeds a predetermined temperature. [Effects of the Invention]

[0007] According to the first technique, the power discharged from the battery cells by cell balancing control can be utilized to cool the battery cells. As a result, the battery cells are prevented from being exposed to high temperatures, and deterioration of battery performance is suppressed. Specifically, by suppressing the battery cells from being exposed to high temperatures, deterioration of the electrodes, electrolyte, etc. is suppressed, and a decrease in battery capacity and battery cell output can be suppressed.

[0008] Furthermore, by preventing the battery cells from being exposed to high temperatures, it is possible to prevent an increase in self-discharge of the battery cells. By preventing self-discharge of the battery cells, it is possible to prevent the battery cells from wasting energy and extend their lifespan. Furthermore, by preventing the battery cells from being exposed to high temperatures, it is possible to prevent deterioration of the internal structure and materials of the battery cells, and to prevent deformation of the battery cell components and expansion of the battery cells. As a result, it is possible to prevent adverse effects on the operation and performance of the battery cells. Furthermore, in the first technology, the cooling unit is operated with the power consumed during cell balance control, so it is also possible to reduce the power consumption required to cool the battery cells.

[0009] The cooling unit can be a device (component) that can physically cool the battery cells, such as a Peltier element (thermoelectric conversion element), a fan, etc. In addition, if a battery pack made up of multiple battery cells has a circulation path for cooling, the entire battery pack can be cooled by attaching a cooling unit to the circulation path.

[0010] Note that "the cooling unit is provided near the battery cell" means that the cooling unit is in direct contact with the battery cell (exterior of the battery cell), that the cooling unit (the cooling surface of the cooling unit) faces the exterior surface of the battery cell, or that no other components exist between the cooling unit and the battery cell. In other words, the location of the cooling unit is not particularly limited as long as it is in a position where the battery cell can be efficiently cooled. Furthermore, when the cooling unit is in direct contact with the battery cell, the side of the cooling unit that is not in contact with the battery cell (the side opposite to the side in contact with the battery cell) may be open to the atmosphere. Alternatively, when the cooling unit is in direct contact with the battery cell, the side of the cooling unit that is not in contact with the battery cell may be coated with a material (e.g., metal) that promotes heat dissipation.

[0011] According to the second technology, even when cell balancing control is not being performed, it is possible to suppress deterioration of battery performance due to temperature rise of the battery cells. For example, when the current flow is constant, such as during charging, even if voltage equalization is not required, the cooling unit can be operated to cool the battery cells according to the temperature near the battery cells. Furthermore, when cell balancing control is being performed and the cooling unit is operating, it is also possible to determine whether an abnormality has occurred in the cooling unit. Note that "the temperature detection unit is provided near the battery cells" means that the temperature detection unit can be provided in a position similar to that described for the cooling unit above, as long as it is located in a position where the temperature of the battery cells can be accurately detected. [Brief explanation of the drawings]

[0012] [Figure 1] 1 shows a battery system according to a first embodiment. [Figure 2] 1 shows a battery system according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] (First Example) A battery system 10 will be described with reference to FIG. 1. The battery system 10 is used, for example, as a battery mounted on a vehicle. The battery system 10 includes a battery cell 6, a cooling unit 8 arranged near the battery cell 6, wiring 12 connecting the battery cell 6 and the cooling unit 8, a switch unit 2 provided on the wiring, and a control unit 4 that controls the operation of the switch unit 2. When the battery system 10 is actually used, it is mounted on a vehicle or the like as a battery pack including multiple battery cells 6 connected in series. The battery system 10 is used in a battery pack that performs cell balancing control to compensate for voltage differences between the multiple battery cells 6 and equalize the voltages of the battery cells 6.

[0014] The battery cells 6 are secondary batteries that can be repeatedly charged and discharged. The cooling unit 8 has a Peltier element and can cool the surface of the cooling unit 8 by supplying power. The cooling surface of the cooling unit 8 is arranged near the battery cells 6 so that it faces the exterior surface of the battery cells 6. In other words, the heating surface of the cooling unit 8 faces the opposite side (the atmosphere side) from the battery cells 6. The cooling unit 8 is also connected in parallel to the battery cells 6 via wiring 12 that has a switch unit 2. When the switch unit 2 is turned on, the battery cells 6 and the cooling unit 8 are electrically connected, and when the switch unit 2 is turned off, the battery cells 6 and the cooling unit 8 are not electrically connected. When the switch unit 2 is turned on, power is supplied from the battery cells 6 to the cooling unit 8, and the cooling unit 8 is activated. When the cooling unit 8 is activated, the battery cells 6 are cooled, reducing their temperature or suppressing a temperature rise in the battery cells 6. The control unit 4 switches the switch unit 2 on and off.

[0015] The control unit 4 detects the voltage of the battery cell 6 via the wiring 12, and when the voltage difference between the battery cell 6 and other battery cells is equal to or greater than a predetermined value, the control unit 4 charges or discharges the battery cell 6 to equalize the voltages among the battery cells (performs cell balance control). Furthermore, when the power discharged from the battery cell 6 exceeds a predetermined value, the control unit 4 turns on the switch unit 2 and activates the cooling unit 8. This cools the battery cell 6 as described above, and the temperature of the battery cell 6 decreases. That is, when the battery cell 6 discharges due to cell balance control, the battery system 10 can use the discharged power to activate the cooling unit 8 and cool the battery cell 6. This can prevent the battery cell 6 from generating heat and increasing its temperature due to discharge, thereby suppressing performance degradation of the battery cell 6.

[0016] Note that cell balance control is also performed, for example, when charging while the vehicle is running. In this case, suppressing heat generation in the battery cells 6 during charging can suppress deterioration of the battery cells 6. Also, suppressing heat generation in the battery cells 6 during charging can also enable charging to be completed earlier. Also, suppressing heat generation in the battery cells 6 during charging can also prevent current limiting (activation of the overcurrent limiting function). Note that cell balance control is also performed when the vehicle is parked. In this case, too, the battery cells 6 are prevented from becoming too hot after charging and discharging, and deterioration of the battery cells 6 can be suppressed.

[0017] (Second Example) The battery system 110 will be described with reference to Fig. 2. The battery system 110 is a modified example of the battery system 10, and differs from the battery system 10 in that it includes a temperature detection unit (temperature sensor) 20. In the following description, components that are substantially the same as those in the battery system 10 will be assigned the same reference numbers as those assigned to the battery system 10, and descriptions thereof may be omitted.

[0018] The temperature detection unit 20 is disposed near the battery cell 6 such that its temperature detection surface faces the exterior surface of the battery cell 6. Therefore, the temperature detection unit 20 can detect the temperature of the battery cell 6 (the surface temperature of the battery cell 6). The detection value of the temperature detection unit 20 is input to the control unit 4. Alternatively, the control unit 4 monitors the detection value of the temperature detection unit 20. When the temperature detected by the temperature detection unit 20 (detection value) exceeds a predetermined temperature, the control unit 4 turns on the switch unit 2 and activates the cooling unit 8. When the switch unit 2 is turned on, power is supplied from the battery cell 6 to the cooling unit 8, which activates the cooling unit 8 and cools the battery cell 6. Note that, like the battery system 10, when the battery cell 6 discharges due to cell balance control, the battery system 110 can also use the discharged power to activate the cooling unit 8 and cool the battery cell 6.

[0019] The battery system 110 can operate the cooling unit 8 based on the temperature of the battery cells 6, regardless of whether cell balance control is being performed. Therefore, when the temperature of the battery cells 6 rises while the battery cells 6 are being charged, the cooling unit 8 can be operated to cool the battery cells 6 even when cell balance control is not being performed. Furthermore, when cell balance control is being performed, if the temperature of the battery cells 6 does not decrease even though the control unit 4 has operated the cooling unit 8, it can be detected that a malfunction has occurred in the cooling unit 8. In other words, the temperature detection unit 20 can detect whether or not there is a malfunction in the cooling unit 8.

[0020] (Other embodiments) In the above-described embodiment, an example was described in which the cooling unit and the temperature detection unit were arranged near the battery cell so that the cooling surface of the cooling unit and the temperature detection surface of the temperature detection unit faced the exterior surface of the battery cell. However, the locations of the cooling unit and / or the temperature detection unit are not limited to the locations described in the embodiment. For example, the cooling unit and / or the temperature detection unit may be in direct contact with the battery cell, or may be arranged with no other components between them and the battery cell. In other words, the distance between the cooling unit and the temperature detection unit and the battery cell is arbitrary as long as the cooling unit is arranged so that it can cool the battery cell and the temperature detection unit is arranged so that it can detect the temperature of the battery cell.

[0021] Although the embodiments of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. Furthermore, the technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings simultaneously achieves multiple objectives, and achieving one of these objectives itself has technical utility. [Explanation of symbols]

[0022] 2: Switch section 4: Control unit 8: Cooling section 10: Battery system 20: Temperature detection unit 110: Battery system

Claims

1. A battery system having a cell balancing means for controlling the charging and discharging of a plurality of battery cells to equalize the voltages of the battery cells, a control unit that charges and discharges each battery cell based on a voltage difference between the battery cells to equalize the voltages of the plurality of battery cells; a cooling unit provided near each of the battery cells and connected to each of the battery cells; a switch unit that switches between electrical continuity and non-conduction between each of the battery cells and the cooling unit, The control unit switches the switch unit to a conductive state and activates the switch unit when the power discharged from each battery cell exceeds a predetermined value when equalizing the voltages of the plurality of battery cells.

2. The battery system according to claim 1, The battery pack further includes a temperature detector that is provided near each of the battery cells and detects the temperature of each of the battery cells, When the temperature detected by the temperature detection unit exceeds a predetermined temperature, the control unit switches the switch unit to a conductive state and activates the switch unit.

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