JP7749431B2 - Battery System - Google Patents

Description

This disclosure relates to a battery system.

Battery packs equipped with multiple battery cells have been known for some time. For example, the battery pack described in claims 1 and 7, Figure 2, etc. of Patent Document 1 listed below has multiple battery cells housed in a case. The battery cells are formed in a rectangular parallelepiped shape. The case is filled with hydrofluoroether as an insulating coolant. The battery cells are also arranged so that the electrode side is located at the bottom of the case.

Cooling systems for lithium secondary batteries that rapidly cool the lithium secondary batteries are also known. For example, the cooling system for lithium secondary batteries described in claims 5 and 6 and figures 1 to 3 of Patent Document 2 listed below includes a conductive connector that is fixed to the electrode terminal of the lithium secondary battery, and a refrigerant pipe that is connected to the connector and through which a refrigerant flows. The conductive connector includes a body, a fixing portion formed on one side of the body and connected to the electrode terminal, and a connecting portion formed on the other side of the body and to which the refrigerant pipe is connected.

JP 2013-062023 A Special Publication No. 2014-501024

The conventional battery pack described in Patent Document 1 above arranges the electrodes of multiple battery cells so that they are located at the bottom of the case, so that the electrodes of each battery cell are immersed in hydrofluoroether, an insulating coolant filled in the case. As a result, there is a risk that unexpected side reactions may occur when the insulating coolant comes into contact with the components around the battery cell electrodes.

The conventional cooling system for lithium secondary batteries described in Patent Document 2 can dissipate heat from the electrode terminals of each lithium secondary battery to the refrigerant pipe via the body of a conductive connector. However, because the body of the conductive connector is a long, thin rod-shaped member that is connected to a portion of the side of the rectangular parallelepiped electrode terminal of each lithium secondary battery and to the lower end of the outer periphery of the refrigerant pipe and extends radially from the refrigerant pipe, its cross-sectional area is small, posing a problem with heat dissipation.

Furthermore, in the above-mentioned conventional lithium secondary battery cooling system, the conductive connector does not electrically connect the electrode terminals of adjacent lithium secondary batteries, and the configuration of the bus bar that electrically connects the electrode terminals is unknown. Therefore, depending on the configuration of the fixing part formed on one side of the body of the conductive connector and connected to the electrode terminal of each lithium secondary battery, it may be difficult to electrically connect the electrode terminals of adjacent lithium secondary batteries.

This disclosure provides a battery system that can improve heat dissipation through the external terminals of the battery cells while avoiding contact between the refrigerant and components around the electrode terminals of the battery cells, and can facilitate electrical connection between the external terminals of adjacent battery cells.

One aspect of the present disclosure is a battery system comprising: a plurality of battery cells; a plurality of hollow, electrically conductive bus bars that connect the external terminals of adjacent battery cells; a plurality of electrically insulating insulating tubes that are provided between the bus bars; and refrigerant passages that are formed inside the bus bars and inside the insulating tubes and that circulate an electrically insulating refrigerant that cools the bus bars.

According to the above aspect of the present disclosure, a battery system can be provided that can improve heat dissipation through the external terminals of the battery cells while avoiding contact between the refrigerant and components around the external terminals of the battery cells, and can facilitate electrical connection between the external terminals of adjacent battery cells.

1 is a partially cutaway side view of a first embodiment of a battery system according to the present disclosure. FIG. 2 is a partially cutaway plan view of the battery system shown in FIG. 1 . FIG. 2 is a perspective view of one battery cell of the battery system shown in FIG. 1 . FIG. 10 is a partially cutaway side view of a second embodiment of a battery system according to the present disclosure. FIG. 5 is a partially cutaway plan view of the battery system shown in FIG. 4 . FIG. 5 is a block diagram of the battery system shown in FIG. 4 . FIG. 10 is a partially cutaway side view of a battery system according to a third embodiment of the present disclosure. FIG. 8 is a block diagram of the battery system shown in FIG. 7 .

Embodiments of the battery system according to the present disclosure will be described below with reference to the drawings.

[Embodiment 1]
Fig. 1 is a partially cut-away side view of a first embodiment of a battery system according to the present disclosure. Fig. 2 is a partially cut-away plan view of the battery system 100 shown in Fig. 1. Fig. 3 is a perspective view of one battery cell 1 of the battery system 100 shown in Fig. 1. The cross section of Fig. 1 is taken along line I-I in Fig. 2, and the cross section of Fig. 2 is taken along line II-II in Fig. 1. Each figure shows an orthogonal coordinate system consisting of an X-axis, a Y-axis, and a Z-axis that are parallel to the thickness, width, and height directions, respectively, of the flattened rectangular parallelepiped battery cell 1.

The battery system 100 of this embodiment includes a plurality of battery cells 1, a plurality of conductive bus bars 2 that connect the external terminals 14 of adjacent battery cells 1, and a refrigerant passage 3 that circulates an electrically insulating refrigerant R that cools the plurality of bus bars 2. The battery system 100 of this embodiment also includes, for example, a heat exchanger 4 connected to the refrigerant passage 3.

Although details will be described later, the battery system 100 of this embodiment is primarily characterized by the following configuration. The refrigerant passage 3 includes a busbar passage 21 that passes through each of the multiple busbars 2, and an insulating passage 51 that is formed inside an electrically insulating insulating tube 5 and connects the busbar passages 21 of adjacent busbars 2 of the multiple busbars 2. Each part of the battery system 100 of this embodiment will be described in detail below.

The battery cell 1 is, for example, a rectangular lithium-ion secondary battery. Note that the type of battery cell 1 is not limited to a lithium-ion secondary battery, and may be, for example, a lead-acid battery, a nickel-metal hydride battery, or a nickel-cadmium battery. The battery cell 1 has, for example, a flat, rectangular battery container 10, as shown in FIG. 3.

The battery container 10 is made of a metal such as an aluminum alloy and is composed of a battery can 11 in the shape of a rectangular cylinder with a bottom, and a battery lid 12 that seals the opening at the top of the battery can 11. Although not shown, the interior of the battery container 10 contains an electrode group formed by stacking and winding a strip-shaped positive electrode and a strip-shaped negative electrode with a strip-shaped separator in between, a pair of current collector plates connected to the positive and negative electrodes at both ends of the electrode group, electrical insulating members, an electrolyte, and other items.

The battery container 10 has a pair of wide side surfaces 10w on both sides in the thickness direction (X-axis direction), a pair of narrow side surfaces 10n on both sides in the width direction (Y-axis direction), a bottom surface 10b at the lower end in the height direction (Z-axis direction), and a top surface 10t at the upper end in the height direction. Of these surfaces of the battery container 10, the wide side surfaces 10w have the largest area. A pair of external terminals 14 are arranged on the top surface 10t of the battery container 10 at both ends in the width direction of the battery container 10, with a pair of insulating members 13 between them, and a split valve 15 and a liquid inlet 16 are provided between the pair of external terminals 14.

Of the pair of external terminals 14, one external terminal 14 is a positive electrode external terminal 14P connected to the positive electrode via a current collector, and the other external terminal 14 is a negative electrode external terminal 14N connected to the negative electrode via a current collector. The split valve 15 splits open when the pressure inside the battery container 10 rises abnormally, ensuring the safety of the battery cell 1. The liquid filling port 16 is used to inject electrolyte into the battery container 10 and is sealed by a liquid filling plug 17.

As shown in FIG. 2, the multiple battery cells 1 are arranged in an alternately inverted manner so that the positive electrode external terminal 14P of one adjacent battery cell 1 and the negative electrode external terminal 14N of the other adjacent battery cell 1 are adjacent in the thickness direction (X-axis direction) of the battery cell 1. Furthermore, the positive electrode external terminal 14P of one adjacent battery cell 1 and the negative electrode external terminal 14N of the other adjacent battery cell 1 are sequentially connected by bus bars 2, thereby connecting the multiple battery cells 1 in series.

In multiple battery cells 1 connected in series, an end bus bar 2E is connected to the positive external terminal 14P of the battery cell 1 at one end in the arrangement direction (X-axis direction) and the negative external terminal 14N of the battery cell 1 at the other end in the arrangement direction. These end bus bars 2E function as external terminals for the battery group, which is made up of multiple battery cells 1 connected in series by multiple bus bars 2.

As mentioned above, the busbar 2 is a hollow, electrically conductive member that connects the external terminals 14 of adjacent battery cells 1 among a plurality of battery cells 1. More specifically, the busbar 2 and the end busbar 2E are tubular metal members with good electrical and thermal conductivity. Materials that can be used for the busbar 2 and the end busbar 2E include copper, aluminum, and nickel, for example.

In this embodiment, the cross-sectional shape of the busbar 2 and the end busbar 2E is, for example, rectangular. The width of the busbar 2 and the end busbar 2E is, for example, approximately equal to the width of the external terminal 14 of the battery cell 1. The busbar 2 and the end busbar 2E are joined to the upper surface of the external terminal 14 of the battery cell 1 by, for example, laser welding, and connected to the external terminal 14.

The busbar passages 21 are hollow portions provided in the busbar 2 and the end busbar 2E. The busbar passages 21 have openings at one and the other longitudinal ends of the busbar 2 and the end busbar 2E, respectively, and penetrate the busbar 2 and the end busbar 2E, respectively. In this embodiment, the cross-sectional shape of the busbar passages 21 is rectangular, similar to the busbar 2 and the end busbar 2E.

The insulating tube 5 is an electrically insulating tube made, for example, of an electrically insulating resin material. The insulating passage 51 is a hollow portion provided in the insulating tube 5, has openings at one end and the other end, and passes through the insulating tube 5. In this embodiment, the cross-sectional shape of the insulating tube 5 and the insulating passage 51 is rectangular, similar to the cross-sectional shape of the bus bar 2 and the bus bar passage 21.

The insulating tubes 5 are arranged between adjacent bus bars 2 in the battery cell 1 arrangement direction (X-axis direction), and connect the bus bar passages 21 of those bus bars 2 via insulating passages 51. Furthermore, the insulating tubes 5 connect, for example, one of the pair of refrigerant outlets 43 of the heat exchanger 4 to the bus bar passage 21 of the bus bar 2 closest to the heat exchanger 4. Furthermore, the insulating tube 5 connects, for example, the other of the pair of refrigerant outlets 43 of the heat exchanger 4 to the bus bar passage 21 of the end bus bar 2E closest to the heat exchanger 4.

The insulating tube 5 also connects, for example, one of the pair of refrigerant inlets 41 of the heat exchanger 4 to the busbar passage 21 of the busbar 2 that is farthest from the heat exchanger 4. The insulating tube 5 also connects, for example, the other of the pair of refrigerant inlets 41 of the heat exchanger 4 to the busbar passage 21 of the end busbar 2E that is farthest from the heat exchanger 4.

The refrigerant passage 3 is a passage for circulating an electrically insulating refrigerant R that cools the multiple bus bars 2 and the end bus bars 2E. The boiling point of the refrigerant R at atmospheric pressure is, for example, in the range of 0°C to 55°C. For example, a fluorine-based solvent such as hydrofluoroether can be used as the refrigerant R. The internal pressure of the refrigerant passage 3 can also be reduced to a pressure lower than atmospheric pressure.

The refrigerant passage 3 is composed of, for example, multiple busbar passages 21 for the multiple busbars 2 and end busbars 2E, and multiple insulating passages 51 for the multiple insulating tubes 5. A refrigerant R that cools the multiple busbars 2 and end busbars 2E is sealed inside the refrigerant passage 3. The refrigerant passage 3 is connected, for example, to a heat exchanger 4, and circulates the refrigerant R between the heat exchanger 4 and the multiple busbars 2 and end busbars 2E.

The refrigerant passage 3 includes, for example, a first refrigerant passage 31, a second refrigerant passage 32, and a third refrigerant passage 33. The first refrigerant passage 31 is connected to the refrigerant outlet 43 of the heat exchanger 4 and extends horizontally. The second refrigerant passage 32 extends vertically upward from the first refrigerant passage 31. The third refrigerant passage 33 is connected to the upper end of the second refrigerant passage 32, extends horizontally, and is connected to the refrigerant inlet 41 of the heat exchanger 4.

For example, the refrigerant R fills the entire first refrigerant passage 31, with its liquid level below the upper end of the second refrigerant passage 32. Note that the refrigerant R may also partially fill the first refrigerant passage 31, with its liquid level within the first refrigerant passage 31.

The heat exchanger 4 is disposed, for example, above the first refrigerant passage 31, which includes the bus bar passage 21. The heat exchanger 4 has, for example, a refrigerant inlet 41, a heat dissipation section 42, and a refrigerant outlet 43.

As shown in FIG. 2, the heat exchanger 4 has a pair of refrigerant inlets 41 spaced apart in the width direction (Y-axis direction) of the battery cell 1 at the upper end of the heat dissipation section 42. The heat exchanger 4 also has a pair of refrigerant outlets 43 spaced apart in the width direction of the battery cell 1 at the lower end of the heat dissipation section 42. The pair of refrigerant outlets 43 are connected to the starting ends of the pair of refrigerant passages 3, and the pair of refrigerant inlets 41 are connected to the ending ends of the pair of refrigerant passages 3.

The heat dissipation unit 42 dissipates heat from the refrigerant R introduced through the refrigerant inlet 41 to the outside air while passing the refrigerant R downward. More specifically, the heat dissipation unit 42 has a serpentine flow path 42a that guides the refrigerant R downward in the vertical direction while snaking back and forth along the horizontal direction. The heat dissipation unit 42 also has a heat sink 42b that includes, for example, multiple heat dissipation fins.

The operation of the battery system 100 of this embodiment is described below.

The battery system 100 of this embodiment can supply power from an external generator or the like to a battery group including multiple battery cells 1 connected in series by multiple bus bars 2, via a pair of end bus bars 2E that function as the external terminals of the battery group. This allows the multiple battery cells 1 of the battery system 100 to be charged.

The battery system 100 can also supply power from multiple charged battery cells 1 to external devices such as motors via a pair of end bus bars 2E. In the battery system 100, it is important to uniformly cool each battery cell 1 in order to maintain the temperature of the multiple battery cells 1, which rise during charging and discharging, within an appropriate temperature range and prevent deterioration of each battery cell 1.

As described above, the battery system 100 of this embodiment includes a plurality of battery cells 1, a plurality of bus bars 2, a plurality of insulating tubes 5, and a refrigerant passage 3. Each of the plurality of bus bars 2 connects the external terminals 14 of adjacent battery cells 1 of the plurality of battery cells 1 and is a conductive member with a hollow structure. Each of the plurality of insulating tubes 5 is disposed between adjacent bus bars 2 of the plurality of bus bars 2 and has electrical insulation properties. The refrigerant passage 3 is formed inside the plurality of bus bars 2 and the plurality of insulating tubes 5 and circulates an electrically insulating refrigerant R that cools the plurality of bus bars 2. More specifically, the refrigerant passage 3 includes a bus bar passage 21 that penetrates each of the plurality of bus bars 2 of the plurality of bus bars 2 and an insulating passage 51 that is formed inside the electrically insulating insulating tube 5 and connects the bus bar passages 21 of adjacent bus bars 2 of the plurality of bus bars 2.

With this configuration, the battery system 100 of this embodiment differs from the battery pack described in Patent Document 1 in that the refrigerant R is sealed in the refrigerant passage 3, preventing contact between the refrigerant R and components surrounding the external terminals 14 of each battery cell 1. Therefore, the battery system 100 of this embodiment can prevent unexpected side reactions from occurring due to contact between the refrigerant R and components surrounding the external terminals 14 of each battery cell 1. Furthermore, by circulating the refrigerant R through the refrigerant passage 3, the battery system 100 of this embodiment can reduce the amount of refrigerant R required to cool multiple battery cells 1 compared to the conventional battery pack described above, thereby enabling cost savings on refrigerant R.

Furthermore, with the above-described configuration, the battery system 100 of this embodiment can cool each bus bar 2 using the refrigerant R circulating through the bus bar passage 21 inside each bus bar 2, and can cool the external terminal 14 of each battery cell 1 using each bus bar 2. Furthermore, each bus bar 2 can have a larger bonding area with the external terminal 14 of the battery cell 1 compared to the conductive connectors in the conventional cooling system for lithium secondary batteries described in Patent Document 2. Therefore, the battery system 100 of this embodiment can improve heat dissipation via the external terminal 14 of each battery cell 1 compared to the above-described conventional cooling system.

Furthermore, in the conventional cooling system described above, the electrode terminals of the lithium secondary battery are not directly cooled by refrigerant pipes cooled by a refrigerant, but rather the electrode terminals are indirectly cooled via conductive connectors cooled by the refrigerant pipes. In contrast, in the battery system 100 of this embodiment, due to the above configuration, the busbars 2, cooled by refrigerant R in the busbar passages 21 that penetrate the busbars 2, directly cool the external terminals 14 of the battery cells 1. Therefore, the battery system 100 of this embodiment improves heat dissipation through the external terminals 14 of each battery cell 1 compared to the conventional cooling system described above, suppresses deterioration of each external terminal 14, and extends the service life of the external terminals 14.

In addition, in the conventional cooling system described above, it is necessary to join bus bars to the electrode terminals of the lithium secondary battery in addition to the conductive connectors and refrigerant pipes that cool the electrode terminals. In contrast, in the battery system 100 of this embodiment, the above-described configuration allows the refrigerant passage 3, which circulates the refrigerant that cools each bus bar 2, to include bus bar passages 21 that penetrate each bus bar 2. Therefore, the refrigerant passage 3 is formed by the bus bar passages 21 of the multiple bus bars 2 and the insulating passages 51 of the multiple insulating pipes 5, and at the same time, the external terminals 14 of adjacent battery cells 1 of the multiple battery cells 1 can be electrically connected by the bus bars 2. Therefore, the battery system 100 of this embodiment makes it easier to electrically connect the external terminals 14 of adjacent battery cells 1 than in the conventional cooling system described above.

The battery system 100 of this embodiment also includes a heat exchanger 4 connected to the refrigerant passage 3. The heat exchanger 4 has a refrigerant inlet 41, a heat dissipation section 42, and a refrigerant outlet 43. The refrigerant inlet 41 is connected to the end of the refrigerant passage 3. The heat dissipation section 42 dissipates heat from the refrigerant R to the outside air while allowing the refrigerant R introduced from the refrigerant inlet 41 to pass downward. The refrigerant outlet 43 is provided at the lower end of the heat dissipation section 42 and is connected to the beginning of the refrigerant passage 3.

With this configuration, in the battery system 100 of this embodiment, the refrigerant R, whose temperature has increased after cooling the battery cells 1 via the multiple bus bars 2, is introduced from the end of the refrigerant passage 3 to the refrigerant inlet 41 of the heat exchanger 4. The refrigerant R introduced into the refrigerant inlet 41 passes downward through the heat dissipation section 42, where it dissipates heat into the outside air, thereby lowering its temperature. The cooled refrigerant R is then introduced by gravity from the lower end of the heat dissipation section 42 to the beginning of the refrigerant passage 3, where it cools each battery cell 1 via each bus bar 2. Therefore, the battery system 100 of this embodiment does not require a pump to circulate the refrigerant R through the refrigerant passage 3, thereby improving reliability and reducing power consumption.

In addition, in the battery system 100 of this embodiment, the refrigerant passage 3 has a first refrigerant passage 31, a second refrigerant passage 32, and a third refrigerant passage 33. The first refrigerant passage 31 is connected to the refrigerant outlet 43 of the heat exchanger 4 and extends horizontally. The second refrigerant passage 32 extends vertically upward from the first refrigerant passage 31. The third refrigerant passage 33 is connected to the upper end of the second refrigerant passage 32, extends horizontally, and is connected to the refrigerant inlet 41 of the heat exchanger 4.

With this configuration, the battery system 100 of this embodiment can efficiently cool multiple battery cells 1 simultaneously via multiple bus bars 2 using the refrigerant R in the first refrigerant passage 31. Furthermore, refrigerant R whose temperature has risen in the first refrigerant passage 31 moves from the first refrigerant passage 31 to the second refrigerant passage 32, which extends vertically upward. This prevents backflow and abnormal temperature increases of the refrigerant R due to bumping of the refrigerant R in the first refrigerant passage 31, and prevents a decrease in the cooling efficiency of the battery cells 1.

Furthermore, in the battery system 100 of this embodiment, the heat exchanger 4 is positioned above the first refrigerant passage 31 of the refrigerant passage 3. With this configuration, the battery system 100 of this embodiment can more efficiently circulate the refrigerant R between the refrigerant passage 3 and the heat exchanger 4 by the action of gravity.

In addition, in the battery system 100 of this embodiment, the boiling point of the refrigerant R at atmospheric pressure is within the range of 0°C to 55°C. With this configuration, at least a portion of the liquid refrigerant R in the refrigerant passage 3 that cools the external terminals 14 of the battery cells 1 via the busbar 2 boils and evaporates. This heat of vaporization of the refrigerant R can further improve the cooling efficiency of the battery cells 1. Furthermore, battery cells 1 with temperatures higher than the boiling point of the refrigerant R can be preferentially cooled, making it possible to uniform the temperature of multiple battery cells 1. Furthermore, by adopting a boiling cooling method using the refrigerant R, the cooling efficiency of the battery cells 1 can be improved compared to air-cooling and water-cooling methods.

Furthermore, the refrigerant R that evaporates after cooling the battery cells 1 in the refrigerant passage 3 is cooled in the heat dissipation section 42, where it condenses and returns to liquid. The refrigerant R that returns to liquid in the heat dissipation section 42 is cooled as it flows downward within the heat dissipation section 42 due to the action of gravity, and is then introduced into the refrigerant passage 3 from the refrigerant outlet 43. This allows the refrigerant R to circulate more efficiently between the refrigerant passage 3 and the heat exchanger 4.

Furthermore, in the battery system 100 of this embodiment, the refrigerant R is a hydrofluoroether. This allows the boiling point of the refrigerant R at atmospheric pressure to be within the range of 0°C to 55°C, more specifically, approximately 54°C. It also makes it possible to fully ensure the electrical insulation properties required for the refrigerant R.

Furthermore, in the battery system 100 of this embodiment, when the internal pressure of the refrigerant passage 3 is lower than atmospheric pressure, the boiling point of the refrigerant R can be further lowered. Therefore, the boiling point of the refrigerant R can be optimized according to the characteristics of the battery cell 1, and the cooling efficiency of the battery cell 1 by the refrigerant R via the bus bar 2 can be further improved.

As described above, this embodiment can provide a battery system 100 that can improve heat dissipation through the external terminals 14 of the battery cells 1 while avoiding contact between the refrigerant R and components around the external terminals 14 of the battery cells 1, and can facilitate electrical connection between the external terminals 14 of adjacent battery cells 1.

[Embodiment 2]
A second embodiment of a battery system according to the present disclosure will be described below with reference to Fig. 4 to Fig. 6. Fig. 4 is a partially cut-away side view of the second embodiment of a battery system according to the present disclosure. Fig. 5 is a partially cut-away plan view of the battery system 100A shown in Fig. 4. Fig. 6 is a block diagram of the battery system 100A shown in Fig. 4.

The cross section in FIG. 4 is taken along line IV-IV in FIG. 5, and the cross section in FIG. 5 is taken along line V-V in FIG. 4. Also, FIG. 4 shows the cross section of the first refrigerant passage 31, including the bus bar 2A located on the negative Y-axis side, the second refrigerant passage 32, and the third refrigerant passage 33, and omits the illustration of these components located on the positive Y-axis side.

The battery system 100A of this embodiment differs from the battery system 100 of the first embodiment in the following configuration, for example. The battery system 100A of this embodiment further includes a flow rate sensor 7, a temperature sensor 8, and a control device 9. In addition, in the battery system 100A of this embodiment, the cross-sectional shape of the refrigerant passage 3A is circular. Furthermore, the bus bar 2A has a branch portion 22 and is connected to the external terminal 14 of the battery cell 1 via a plate-shaped member 6.

Furthermore, in the battery system 100A of this embodiment, for example, the first refrigerant passages 31 on both sides of the width direction (Y-axis direction) of the battery cells 1 that make up the refrigerant passage 3A are connected by insulating tubes 5 at the ends opposite the heat exchanger 4 in the arrangement direction (X-axis direction) of the battery cells 1. The other configuration of the battery system 100A of this embodiment is similar to that of the battery system 100 of the first embodiment described above, and therefore similar parts are designated by the same reference numerals and description thereof will be omitted.

In the battery system 100A of this embodiment, as described above, the cross-sectional shape of the refrigerant passage 3A is circular, and therefore the cross-sectional shapes of the bus bar 2A and insulating tube 5 are also circular, and the shapes of the refrigerant inlet 41 and refrigerant outlet 43 of the heat exchanger 4 are also circular. The materials of the bus bar 2A and plate-shaped member 6 are the same as those of the bus bar 2 and end bus bar 2E of embodiment 1.

The busbar 2A has, for example, a T-shape with branch sections 22 that branch off at right angles from the center of the straight pipe section. The branch sections 22 of each busbar 2A are arranged, for example, facing upward, in the direction opposite the external terminals 14 of the battery cells 1. The upper end of each branch section 22 is connected to the lower end of an insulating tube 5 that extends vertically.

The upper ends of the insulating tubes 5, which are connected to the branching portions 22 of each bus bar 2A and extend vertically, are connected to insulating tubes 5 extending horizontally. The bus bar passages 21 that pass through the branching portions 22 of these multiple bus bars 2A and the insulating passages 51 of the multiple insulating tubes 5 form multiple second refrigerant passages 32 that extend vertically upward from the first refrigerant passage 31.

That is, the refrigerant passage 3A has a first refrigerant passage 31 that is connected to the refrigerant outlet 43 of the heat exchanger 4 and extends horizontally, and a third refrigerant passage 33 that is connected to the refrigerant inlet 41 of the heat exchanger 4 and extends horizontally, and a plurality of second refrigerant passages 32 that extend vertically between them.

The flow rate sensor 7 detects the flow rate of refrigerant R flowing through the third refrigerant passage 33 of the refrigerant passage 3A. More specifically, the flow rate sensor 7 is attached to the third refrigerant passage 33 between the multiple second refrigerant passages 32 and the refrigerant inlet 41 of the heat exchanger 4, for example, and detects the flow rate of refrigerant R vapor that evaporates as its temperature rises by cooling the battery cells 1. The flow rate sensor 7 outputs the detected flow rate of refrigerant R to the control device 9.

The temperature sensor 8 detects the temperature of at least one of the multiple battery cells 1. For example, as shown in FIG. 5, the temperature sensor 8 is attached to the top surface 10t of one battery cell 1 located in the center of the multiple battery cells 1 arranged in the thickness direction. Note that the temperature sensor 8 may also be attached to each battery cell 1. The temperature sensor 8 outputs the detected temperature of the battery cell 1 to the control device 9.

The control device 9 is, for example, configured with one or more microcontrollers, and controls the battery pack, which is made up of multiple electrically connected battery cells 1. As shown in FIG. 6, the control device 9 has, for example, a boiling detection unit 91, a load limiting unit 92, and a charge/discharge control unit 93. Each of these units of the control device 9 represents a function of the control device 9 that is realized, for example, by the central processing unit (CPU) of the control device 9 executing a program stored in the memory of the control device 9.

The boiling detection unit 91 detects transition boiling of the refrigerant R based on the flow rate of the refrigerant R detected by the flow rate sensor 7 and the temperature of at least one battery cell 1 detected by the temperature sensor 8. More specifically, the boiling detection unit 91 detects transition boiling of the refrigerant R, for example, when the detected flow rate of the refrigerant R and the temperature of the battery cell 1 satisfy transition boiling conditions stored in advance in memory. Note that the boiling detection unit 91 may also detect transition boiling of the refrigerant R using either the detected flow rate of the refrigerant R or the temperature of the battery cell 1.

When transition boiling of the refrigerant R is detected by the boiling detection unit 91, the load limiting unit 92 calculates an upper limit power for limiting the power load of the battery pack including multiple battery cells 1. The charge/discharge control unit 93 controls the charging and discharging of the multiple battery cells 1 based on the upper limit power calculated by the load limiting unit 92.

The operation of the battery system 100A of this embodiment will be described below.

In the battery system 100A of this embodiment, the refrigerant passage 3A has a first refrigerant passage 31 that is connected to the refrigerant outlet 43 of the heat exchanger 4 and extends horizontally, and a plurality of second refrigerant passages 32 that extend vertically upward. Furthermore, the upper ends of each of the plurality of second refrigerant passages 32 are connected to a third refrigerant passage 33 that is connected to the refrigerant inlet 41 of the heat exchanger 4 and extends horizontally.

With this configuration, the refrigerant R that boils and vaporizes in the first refrigerant passage 31 can escape through the multiple second refrigerant passages 32 to the third refrigerant passage 33, where it can be introduced into the refrigerant inlet 41 of the heat exchanger 4 and condensed in the heat dissipation section 42 of the heat exchanger 4. Therefore, with the battery system 100A of this embodiment, the circulation of the refrigerant R in the refrigerant passage 3A can be promoted, improving heat dissipation via the external terminals 14 of the battery cells 1.

Furthermore, in the battery system 100A of this embodiment, each bus bar 2A is connected to the external terminal 14 of the battery cell 1 via a plate-shaped member 6. With this configuration, the battery system 100A of this embodiment can easily join the bus bar 2A to the external terminal 14 of the battery cell 1, making it possible to easily establish electrical connection between the external terminals 14 of adjacent battery cells 1.

The battery system 100A of this embodiment also includes a flow sensor 7 that detects the flow rate of refrigerant R flowing through the third refrigerant passage 33, a temperature sensor 8 that detects the temperature of at least one of the multiple battery cells 1, and a control device 9 that controls the multiple battery cells 1. The control device 9 includes a boiling detection unit 91, a load limiting unit 92, and a charge/discharge control unit 93. The boiling detection unit 91 detects transition boiling of refrigerant R based on the flow rate of refrigerant R detected by the flow sensor 7 and the temperature of at least one battery cell 1 detected by the temperature sensor 8. The load limiting unit 92 calculates an upper limit power for limiting the power load of the multiple battery cells 1 when transition boiling of refrigerant R is detected by the boiling detection unit 91. The charge/discharge control unit 93 controls the charge/discharge of the multiple battery cells 1 based on the upper limit power calculated by the load limiting unit 92.

With this configuration, the battery system 100A of this embodiment can maintain nucleate boiling of the refrigerant R by limiting the power load of the multiple battery cells 1 when transition boiling of the refrigerant R is detected by the boiling detection unit 91 of the control device 9. Therefore, the battery system 100A of this embodiment can improve heat dissipation via the external terminals 14 of the battery cells 1 due to boiling of the refrigerant R.

As described above, this embodiment provides a battery system 100A that can improve heat dissipation through the battery cells 1 while avoiding contact between the refrigerant R and components surrounding the external terminals 14 of the battery cells 1, and can facilitate electrical connection between the external terminals 14 of adjacent battery cells 1.

[Embodiment 3]
A third embodiment of a battery system according to the present disclosure will be described below with reference to Fig. 7 and Fig. 8. Fig. 7 is a side view in which a portion of the third embodiment of a battery system according to the present disclosure is cut away. Fig. 8 is a block diagram of the battery system 100B shown in Fig. 7.

The battery system 100B of this embodiment differs from the battery system 100A of the aforementioned embodiment 2 in the following configuration, for example. The battery system 100B includes a coolant passage T1 that supplies coolant L to the outer surface of the heat dissipation section 42 of the heat exchanger 4, and a solenoid valve V that opens and closes the coolant passage T1. In addition, the battery system 100B of this embodiment includes a control device 9 that includes a solenoid valve control unit 94. The battery system 100B of this embodiment also includes a housing C. The other configuration of the battery system 100B of this embodiment is similar to that of the battery system 100A of the aforementioned embodiment 2, so similar parts are designated by the same reference numerals and description thereof will be omitted.

The coolant passage T1 is, for example, a coolant supply pipe connected to a coolant tank T that stores coolant L, and supplies coolant L from the coolant tank T to the outer surface of the heat dissipation section 42 of the heat exchanger 4. The coolant passage T1 is, for example, located above the heat sink 42b of the heat dissipation section 42, extending vertically downward from the coolant tank T, with its opening located near the heat sink 42b. The coolant L can be, for example, water.

The solenoid valve V is provided, for example, midway along the coolant passage T1 between the coolant tank T and the heat exchanger 4. The solenoid valve V includes, for example, a valve element that opens and closes the coolant passage T1, and a drive unit that drives the valve element. The solenoid valve V opens and closes the coolant passage T1 when the drive unit, controlled by the control device 9, drives the valve element.

The control device 9 has a boiling detection unit 91 and a solenoid valve control unit 94 that opens the solenoid valve V when the boiling detection unit 91 detects transition boiling of the refrigerant R. Note that the control device 9 may also have a load limiting unit 92 and a charge/discharge control unit 93, similar to the battery system 100A of embodiment 2 shown in FIG. 6, and may control a battery pack including multiple battery cells 1.

The housing C houses multiple battery cells 1, multiple bus bars 2A, and refrigerant passages 3A. More specifically, the housing C is shaped like a rectangular parallelepiped and houses multiple insulating tubes 5 and a heat exchanger 4, as well as multiple battery cells 1, multiple bus bars 2A, and refrigerant passages 3A, and includes a thermal insulator. More specifically, the housing C has a thermal insulator bonded to at least one of the inner and outer surfaces of a main body made of metal or resin, for example. The housing C also has an opening C1 that exposes the heat sink 42b of the heat dissipation unit 42 to the outside, for example.

The operation of the battery system 100B of this embodiment will be described below.

As described above, the battery system 100B of this embodiment includes a flow sensor 7, a temperature sensor 8, a coolant passage T1, a solenoid valve V, and a control device 9. The flow sensor 7 detects the flow rate of the refrigerant R flowing through the third refrigerant passage 33 of the refrigerant passage 3A. The temperature sensor 8 detects the temperature of at least one of the multiple battery cells 1. The coolant passage T1 supplies coolant L to the outer surface of the heat dissipation section 42 of the heat exchanger 4. The solenoid valve V opens and closes the coolant passage T1. The control device 9, which controls the solenoid valve V, includes a boiling detection unit 91 and a solenoid valve control unit 94. The boiling detection unit 91 detects transition boiling of the refrigerant R based on the flow rate of the refrigerant R detected by the flow sensor 7 and the temperature of at least one battery cell 1 detected by the temperature sensor 8. The solenoid valve control unit 94 opens the solenoid valve V when transition boiling of the refrigerant R is detected by the boiling detection unit 91.

With this configuration, when the boiling detection unit 91 of the control device 9 detects transition boiling of the refrigerant R, the battery system 100B of this embodiment can open the solenoid valve V to supply the coolant L from the coolant passage T1 to the outer surface of the heat dissipation unit 42 of the heat exchanger 4. As a result, the cooling performance of the refrigerant R by the heat dissipation unit 42 is improved, and nucleate boiling of the refrigerant R can be maintained. Therefore, with the battery system 100B of this embodiment, similar to the battery system 100A of the second embodiment described above, heat dissipation through the external terminals 14 of the battery cells 1 due to boiling of the refrigerant R can be improved. Furthermore, by using water as the coolant L, the environmental impact of evaporated coolant L can be eliminated.

The battery system 100B of this embodiment also includes a housing C. The housing C contains a thermal insulator and houses multiple battery cells 1, multiple bus bars 2A, and refrigerant passages 3A. With this configuration, for example, when the battery system 100B is mounted on a vehicle, even at night when the vehicle is parked and the battery system 100B is idle, it is possible to prevent the temperature of the refrigerant R from dropping too low, thereby preventing lithium deposition in each battery cell 1. It also makes it unnecessary to warm up the vehicle.

As described above, this embodiment provides a battery system 100B that can improve heat dissipation through the external terminals 14 of the battery cells 1 while avoiding contact between the refrigerant R and components surrounding the external terminals 14 of the battery cells 1, and can facilitate electrical connection between the external terminals 14 of adjacent battery cells 1.

The above detailed description of an embodiment of the battery system according to the present disclosure has been provided using the drawings, but the specific configuration is not limited to this embodiment, and any design changes that do not deviate from the gist of the present disclosure are also included in the present disclosure.

1 Battery cell 14 External terminal 2 Bus bar 2A Bus bar 2E End bus bar (bus bar)
21 Bus bar passage 3 Refrigerant passage 3A Refrigerant passage 31 First refrigerant passage 32 Second refrigerant passage 33 Third refrigerant passage 4 Heat exchanger 41 Refrigerant inlet 42 Heat dissipation section 43 Refrigerant outlet 5 Insulating tube 51 Insulating passage 7 Flow rate sensor 8 Temperature sensor 9 Control device 91 Boiling detection section 92 Load limiting section 93 Charging/discharging control section 94 Solenoid valve control section 100 Battery system 100A Battery system 100B Battery system C Housing R Refrigerant T1 Cooling liquid passage V Solenoid valve

Claims (7)

A plurality of battery cells;
a plurality of conductive bus bars having hollow structures that connect the external terminals of adjacent battery cells of the plurality of battery cells;
a plurality of insulating tubes provided between the plurality of bus bars and having electrical insulation properties;
a refrigerant passage formed inside the plurality of bus bars and inside the plurality of insulating pipes, the refrigerant passage circulating an electrically insulating refrigerant for cooling the plurality of bus bars;
a heat exchanger connected to the refrigerant passage, the heat exchanger including: a refrigerant inlet connected to an end of the refrigerant passage; a heat radiating section that radiates heat of the refrigerant to outside air while passing the refrigerant introduced from the refrigerant inlet downward; and a refrigerant outlet provided at a lower end of the heat radiating section and connected to a starting end of the refrigerant passage;
Equipped with
The refrigerant passage includes a first refrigerant passage connected to the refrigerant outlet and extending horizontally, a second refrigerant passage extending vertically upward from the first refrigerant passage, and a third refrigerant passage connected to an upper end of the second refrigerant passage, extending horizontally, and connected to the refrigerant inlet.
and
moreover,
a flow rate sensor for detecting a flow rate of the refrigerant flowing through the third refrigerant passage;
a temperature sensor for detecting a temperature of at least one of the plurality of battery cells;
a control device that controls the plurality of battery cells;
Equipped with
The control device
a boiling detection unit that detects transition boiling of the refrigerant based on the flow rate of the refrigerant detected by the flow rate sensor and the temperature of the at least one battery cell detected by the temperature sensor;
a load limiting unit that calculates an upper limit power for limiting the power load of the plurality of battery cells when transition boiling of the refrigerant is detected by the boiling detection unit;
a charge/discharge control unit that controls charging/discharging of the plurality of battery cells based on the upper limit power calculated by the load limiting unit;
A battery system comprising : A plurality of battery cells;
a plurality of conductive bus bars having hollow structures that connect the external terminals of adjacent battery cells of the plurality of battery cells;
a plurality of insulating tubes provided between the plurality of bus bars and having electrical insulation properties;
a refrigerant passage formed inside the plurality of bus bars and inside the plurality of insulating pipes, the refrigerant passage circulating an electrically insulating refrigerant for cooling the plurality of bus bars;
a heat exchanger connected to the refrigerant passage, the heat exchanger including: a refrigerant inlet connected to an end of the refrigerant passage; a heat radiating section that radiates heat of the refrigerant to outside air while passing the refrigerant introduced from the refrigerant inlet downward; and a refrigerant outlet provided at a lower end of the heat radiating section and connected to a starting end of the refrigerant passage;
Equipped with
The refrigerant passage includes a first refrigerant passage connected to the refrigerant outlet and extending horizontally, a second refrigerant passage extending vertically upward from the first refrigerant passage, and a third refrigerant passage connected to an upper end of the second refrigerant passage, extending horizontally, and connected to the refrigerant inlet.
and
moreover,
a flow rate sensor for detecting a flow rate of the refrigerant flowing through the third refrigerant passage;
a temperature sensor for detecting a temperature of at least one of the plurality of battery cells;
a coolant passage for supplying a coolant to an outer surface of the heat radiating portion of the heat exchanger;
an electromagnetic valve that opens and closes the coolant passage;
a control device for controlling the solenoid valve;
Equipped with
The control device
a boiling detection unit that detects transition boiling of the refrigerant based on the flow rate of the refrigerant detected by the flow rate sensor and the temperature of the at least one battery cell detected by the temperature sensor;
a solenoid valve control unit that opens the solenoid valve when transition boiling of the refrigerant is detected by the boiling detection unit;
A battery system comprising : 3. The battery system according to claim 1 , wherein the heat exchanger is disposed above the first refrigerant passage. 3. The battery system according to claim 1 , wherein the boiling point of the refrigerant at atmospheric pressure is in the range of 0°C to 55°C. 3. The battery system according to claim 1 , wherein the refrigerant is a hydrofluoroether. 3. The battery system according to claim 1 , wherein the internal pressure of the refrigerant passage is lower than atmospheric pressure. 3. The battery system according to claim 1 , further comprising a housing containing a heat insulating material and accommodating the plurality of battery cells, the plurality of bus bars, and the coolant passage.