Battery cooling device

Abstract

To provide a battery cooling device that can suppress the occurrence of temperature unevenness inside a single cell. [Solution] The battery cooling device according to the present disclosure is a battery cooling device comprising a cooling channel for cooling a plurality of battery packs from upstream to downstream, wherein the cooling channel comprises a first branch channel and a second branch channel for cooling the battery packs, the first branch channel cooling the upstream battery packs at a position higher than the second branch channel and the downstream battery packs at a position lower than the second branch channel.

Description

Technical Field

[0001] The present disclosure relates to a battery cooling device.

Background Art

[0002] In recent years, technologies related to cooling methods for assembled batteries composed of a plurality of single cells have been disclosed. Here, a single cell is also referred to as a battery cell. Further, an assembled battery may also be referred to as a battery module or a battery pack. For example, the power storage device disclosed in Patent Document 1 provides a cooler on the opposing side surfaces of an assembled battery, and provides a standing wall portion of a frame body outside the cooler. The cooler includes a plurality of cooling pipes, and a liquid refrigerant or the like flows through the cooling pipes. The standing wall portion is composed of an opposing portion and a back portion that face the cooler, and the opposing portion and the back portion are formed of materials having different coefficients of thermal expansion. When the cooler is activated, the cooler cools not only the single cells but also the standing wall portion of the frame body. As a result, the standing wall portion is curved and deformed so as to press the cooler against the single cells. As a result, the cooler can cool the single cells well.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The cooler described in Patent Document 1 has equivalent cooling performance for a battery pack if the flow rate of the cooling refrigerant in each cooler is the same. Now, consider the case where the coolers are positioned at different heights, for example, when the coolers are positioned on the upper and lower surfaces in the vertical direction (direction of gravity) of the battery pack. If the cooling channels, which are separated into upper and lower sections, share a flow path in a certain section, a difference in the flow rate of the cooling refrigerant occurs between the upper and lower surfaces during the process of the cooling channels branching into upper and lower sections. This phenomenon can occur, for example, when the cooler pump is controlled to have a constant discharge pressure, due to the change in flow velocity on the upper and lower surfaces caused by gravity. When there is a difference in the flow rate of the cooling refrigerant on the upper and lower surfaces, a difference in the heat dissipation effect occurs on the upper and lower surfaces. As a result, temperature unevenness occurs inside each individual cell within the battery pack. Temperature unevenness refers to a state in which a temperature difference occurs inside an individual cell.

[0005] This disclosure is made to solve these problems and aims to provide a battery cooling device that can suppress the occurrence of temperature unevenness inside a single cell. [Means for solving the problem]

[0006] The battery cooling device according to this disclosure is a battery cooling device equipped with a cooling channel for cooling a plurality of battery packs from upstream to downstream, wherein the cooling channel comprises a first branch channel and a second branch channel for cooling the battery packs, and the first branch channel cools the upstream battery packs at a higher position than the second branch channel and the downstream battery packs at a lower position than the second branch channel. As a result, the vertical positional relationship between the cooling position of the first branch channel and the cooling position of the second branch channel is reversed between the upstream and downstream battery packs, thereby suppressing the flow rate difference between the branch channels in the downstream battery packs and suppressing the difference in cooling performance between the branch channels. Therefore, the battery cooling device according to this disclosure can suppress the occurrence of temperature unevenness inside a single cell. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a battery cooling device that can suppress the occurrence of temperature unevenness inside a single cell. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram of the battery system 1 relating to this disclosure. [Figure 2] Figure 2 shows an example of a conventional battery cooling device. [Figure 3] Figure 3 is a schematic diagram showing how a conventional battery cooling device cools four battery packs. [Figure 4] Figure 4 is a schematic diagram showing the battery cooling device 3 according to this disclosure when it cools four battery packs. [Figure 5] Figure 5 is an illustrative diagram showing the pressure loss generated by a conventional battery cooling device and the battery cooling device 3 according to this disclosure. [Modes for carrying out the invention]

[0009] Embodiments of the present disclosure will be described below with reference to the drawings. Figure 1 is a schematic diagram of the battery system 1 according to the present disclosure. The battery system 1 comprises a plurality of battery cases 2 and a battery cooling device 3. The battery system 1 is mainly mounted on a vehicle. A vehicle equipped with the battery system 1 is a vehicle that runs on electricity as part of its power source. Specifically, this refers to HEV (Hybrid Electric Vehicle), BEV (Battery Electric Vehicle), PHEV (Plug-in Hybrid Electric Vehicle), FCEV (Fuel Cell Electric Vehicle), etc. The various components of the battery system 1 will be described in detail below.

[0010] <Battery case> Battery case 2 is an enclosure for housing a battery pack (not shown). The battery pack is a rechargeable secondary battery composed of multiple single cells electrically connected in series and arranged inside. The battery pack may be a lithium-ion battery, a nickel-metal hydride battery, or another type of secondary battery. The battery pack is typically rectangular in shape.

[0011] The shape of a single cell may be rectangular, cylindrical, elliptical, or laminated. Furthermore, if a single cell has electrode terminals, the battery pack may arrange the cells so that the electrode terminals are horizontal or vertical. For example, if a single cell normally has its electrode terminals oriented vertically, the battery pack may arrange the single cell horizontally. In this case, the electrode terminals are positioned horizontally.

[0012] When individual cells are stacked in a predetermined direction, the stacking direction of the cells may be horizontal or vertical. That is, in this case, the cells in Figure 1 may be arranged in the X-axis direction, the Y-axis direction, or the Z-axis direction. The stacked cells are also called a battery stack.

[0013] Multiple battery packs are arranged in any direction. They may be arranged horizontally or vertically. If a battery pack is rectangular and its longitudinal direction is horizontal, multiple battery packs may be arranged at regular intervals along its longitudinal direction. Alternatively, multiple battery packs may be arranged at regular intervals along their short-sides in the horizontal plane. Furthermore, multiple battery packs may be arranged at regular intervals vertically. In Figure 1, multiple battery packs are arranged in the X-axis direction.

[0014] At least a portion of the battery case 2 is made of a material with high thermal conductivity. In other words, the battery case 2 has surfaces that allow heat exchange between the heat generated by the battery pack it houses and the outside of the battery case 2. That is, all surfaces of the battery case 2 may be made of a material with high thermal conductivity. Specifically, a portion of the battery case 2 may be made of a metal such as aluminum or copper, or the entire battery case 2 may be made of a metal such as aluminum or copper.

[0015] The battery case 2 may be formed to house the entire battery pack, or it may be formed to cover only a part of the battery pack. For example, the battery case 2 may be formed to cover only the vertically opposing surfaces of the battery pack, or it may be formed to cover only the horizontally opposing surfaces. Alternatively, the battery case 2 may be formed to cover two non-opposing surfaces of the battery pack. Furthermore, the battery case 2 may be formed so that one battery case 2 covers multiple battery packs as a whole. For example, the battery case 2 may be formed to cover two battery packs as a whole, or it may be formed to cover three or more battery packs as a whole. In Figure 1, the battery case 2 houses the entirety of one battery pack.

[0016] The battery case 2 is formed such that a surface made of a highly thermally conductive material conforms to the battery pack. This is to exchange heat generated by the individual cells within the battery pack with the external mechanism of the battery case 2. That is, the surface on the battery case 2 may be in contact with the battery pack, or it may be formed with a small gap between it and the battery pack. On the other hand, if there is a surface on the battery case 2 that is not made of a highly thermally conductive material, that surface does not have to conform to the battery pack, and there may be sufficient space between that surface and the opposite surface of the battery pack. For example, if the battery pack is rectangular, the battery case 2 may be formed in a rectangular parallelepiped shape to cover the shape of the battery pack. In Figure 1, the entire battery case 2 is made of a highly thermally conductive material.

[0017] <Battery cooling device> Next, the battery cooling device 3 will be described. The battery cooling device 3 is a device that removes heat generated in the individual cells within the battery pack housed in the battery case 2 by exchanging heat with them, thereby lowering the temperature of the individual cells. The battery cooling device 3 cools the battery pack using a cooling refrigerant. The cooling refrigerant mainly used is a coolant such as water, but air can also be used. From here on, the explanation will focus on the case where a coolant is used as the cooling refrigerant in the battery cooling device 3.

[0018] The battery cooling device 3 includes a cooling flow path 30 and a coolant pump. The cooling flow path 30 is a pipe through which the coolant flows. That is, the cooling flow path 30 is a location in the battery cooling device 3 where direct heat exchange occurs with the single cells in the battery pack. The cooling of the battery pack by the battery cooling device 3 means that the coolant passing through the cooling flow path 30 exchanges heat with the single cells in the battery pack.

[0019] The cooling flow path 30 is formed of a material with high thermal conductivity. For example, the cooling flow path 30 is formed of a metal such as copper.

[0020] The entire inside of the pipe of the cooling flow path 30 may be filled with the coolant, or only a part of the pipe may be filled with the coolant. Also, the cooling flow path 30 may be formed in a cylindrical shape or may be formed in a rectangular parallelepiped shape. In FIG. 1, the cooling flow path 30 is formed in a rectangular parallelepiped shape.

[0021] The coolant pump sends the coolant onto the cooling flow path 30 and sends it to the battery case 2. Thereby, the coolant exchanges heat with the single cells in the battery case 2 and cools the single cells. In FIG. 1, the coolant pump is not shown.

[0022] The coolant pump is controlled, for example, so that the discharge pressure is constant. That is, the coolant pump compensates for the pressure loss (pressure drop) caused by the generation of vortices in the coolant due to the friction between the coolant and the wall surface of the cooling flow path 30 and the refraction of the path, etc., and performs control to increase the pressure of the coolant to a predetermined value and discharge it.

[0023] The battery cooling device 3 may be configured so that one device cools multiple battery packs, or two or more devices cool multiple battery packs. Specifically, the battery cooling device 3 may consist of only one cooling channel 30 and one coolant pump for each of the multiple battery packs, or it may have two or more cooling channels for each of the multiple battery packs. Alternatively, the battery cooling device 3 may have one coolant pump for each of the multiple battery packs and have cooling channels 30 corresponding to the number of battery packs. In this case, the number of cooling channels 30 may be less than or more than the number of battery packs.

[0024] The cooling channel 30 is designed so that one channel cools two or more battery packs. In other words, two or more battery packs are connected in series in the cooling channel 30. When one battery case 2 houses one battery pack, the cooling channel 30 is designed so that one channel passes through two or more battery cases 2. When one battery case 2 houses two or more battery packs, one cooling channel 30 may be designed to cool two or more battery packs housed in one battery case 2. In Figure 1, the cooling channel 30 is designed to cool two battery cases 2, each housing one battery pack.

[0025] The coolant discharged from the coolant pump is routed through a cooling channel 30 to cool two or more battery packs and then returns to the pump. Here, among two battery packs cooled by one cooling channel 30, the battery pack cooled first by the cooling channel 30 is called the upstream battery pack, and the battery pack cooled later is called the downstream battery pack. The upstream and downstream battery packs may or may not be adjacent. In Figure 1, battery case 2a houses the upstream battery pack, and battery case 2b houses the downstream battery pack.

[0026] <Cooling channel configuration> The cooling channel 30 includes a branching point 31, an upstream upper branch channel 32, an upstream lower branch channel 33, a descending channel 34, an ascending channel 35, a downstream upper branch channel 36, a downstream lower branch channel 37, and a confluence point 38. Each of these components will be described below.

[0027] First, let's explain the branching point 31. The branching point 31 is the point in the cooling channel 30 where one channel is branched into an upstream upper branch channel 32 and an upstream lower branch channel 33. The branching point 31 is located further upstream from the upstream battery pack, that is, on the discharge side of the coolant pump. The branching point 31 branches the upstream upper branch channel 32 to a position higher than the upstream lower branch channel 33.

[0028] The branching point 31 does not have to branch the upstream upper branch channel 32 to a position higher than the height at the branching point 31. Also, the branching point 31 does not have to branch the upstream lower branch channel 33 to a position lower than the height at the branching point 31. In other words, the branching point 31 and the upstream upper branch channel 32 may be at the same height, and the branching point 31 and the upstream lower branch channel 33 may be at the same height. The branching point 31 may have a T-shape or a Y-shape. In Figure 1, the branching point 31 has a T-shape, branching the upstream upper branch channel 32 to a position higher than the branching point 31, and branching the upstream lower branch channel 33 to a position lower than the branching point 31.

[0029] Next, the upstream upper branch channel 32 and the upstream lower branch channel 33 will be described. The upstream upper branch channel 32 and the upstream lower branch channel 33 are branch channels that branch off via the branching point 31. The upstream upper branch channel 32 is also called the first branch channel. The upstream lower branch channel 33 is also called the second branch channel. Hereafter, the upstream upper branch channel 32 and the upstream lower branch channel 33 will be collectively referred to as the upstream branch channel.

[0030] The upstream branch channel is positioned along the battery case 2 to cool the upstream battery pack. Specifically, the upstream branch channel is positioned close to a surface of the battery case 2 containing the upstream battery pack that is made of a material with high thermal conductivity. Here, the upstream branch channel may be in contact with the surface of the battery case 2, or it may be positioned with a small gap between it and the battery case 2. Furthermore, the upstream branch channel may have the same width as the width of the surface of the battery case 2 in the direction of the flow of the coolant, or it may be wider or narrower than the width of the surface. In addition, the upstream branch channel may be straight or bent. In Figure 1, the upstream branch channel is designed to be narrower than the width of the opposing battery case 2a.

[0031] The upstream upper branch channel 32 cools the upstream battery pack from a higher position than the upstream lower branch channel 33. Therefore, the upstream upper branch channel 32 is positioned higher than the upstream lower branch channel 33. The upstream upper branch channel 32 and the upstream lower branch channel 33 may be positioned close to opposing surfaces of the battery case 2, or close to non-opposing surfaces, or both may be positioned close to one surface of the battery case 2.

[0032] For example, if the battery case 2 has a rectangular parallelepiped shape, the upstream upper branch channel 32 and the upstream lower branch channel 33 may be arranged on the vertical upper and lower surfaces, respectively. Alternatively, the upstream branch channel may be arranged on the side opposite to the direction of travel. Furthermore, the upstream upper branch channel 32 may be arranged on the upper surface in the vertical direction, and the upstream lower branch channel 33 may be arranged on the side in the direction of travel. Furthermore, both the upstream upper branch channel 32 and the upstream lower branch channel 33 may be arranged on one side in the direction of travel. In Figure 1, the upstream upper branch channel 32 is arranged on the vertical upper surface of the battery case 2a, and the upstream lower branch channel 33 is arranged on the vertical lower surface of the battery case 2a.

[0033] The upstream upper branch channel 32 and the upstream lower branch channel 33 may be arranged so as to face two or more surfaces of the battery case 2. For example, if the battery case 2 is rectangular and both the upstream upper branch channel 32 and the upstream lower branch channel 33 have a U-shaped cross-section, the upstream upper branch channel 32 may be arranged on the upper side of the rectangular parallelepiped of the battery case 2, and the upstream lower branch channel 33 may be arranged on the lower side of the rectangular parallelepiped of the battery case 2. In this case, the upstream upper branch channel 32 faces the vertical upper surface and both sides in the direction of travel. The upstream lower branch channel 33 faces the vertical lower surface and both sides in the direction of travel.

[0034] Next, the descending channel 34 and the ascending channel 35 will be described. The descending channel 34 is part of the cooling channel 30 through which the cooling liquid flowing in the upstream upper branch channel 32 in the upstream battery pack flows towards the downstream battery pack. In other words, the descending channel 34 is a channel that connects the upstream upper branch channel 32 and the downstream lower branch channel 37.

[0035] The upward channel 35 is part of the cooling channel 30 through which the cooling liquid flowing in the upstream lower branch channel 33 of the upstream battery pack flows towards the downstream battery pack. In other words, the upward channel 35 is a channel that connects the upstream lower branch channel 33 and the downstream upper branch channel 36. Hereafter, the downward channel 34 and the upward channel 35 will be collectively referred to as the connecting channel.

[0036] As the coolant flowing through the upstream upper branch channel 32 and the coolant flowing through the upstream lower branch channel 33 pass through the descending channel 34 and the ascending channel 35, respectively, the coolant flowing through the upstream upper branch channel 32 flows at a lower position than the coolant flowing through the upstream lower branch channel 33. In other words, the vertical positional relationship between the coolant flowing through the upstream upper branch channel 32 and the coolant flowing through the upstream lower branch channel 33 is reversed by the connecting channel.

[0037] For example, suppose that adjacent upstream and downstream battery packs have a rectangular parallelepiped shape, and that the upstream upper branch channel 32 and the upstream lower branch channel 33 are arranged so as to be close to the upper and lower surfaces of the battery packs in the vertical direction. In this case, the descending channel 34 is arranged so that the coolant flowing through the upstream upper branch channel 32 is directed towards the vertical lower surface of the downstream battery pack via the descending channel 34. Also, the ascending channel 35 is arranged so that the coolant flowing through the upstream lower branch channel 33 is directed towards the vertical upper surface of the downstream battery pack via the ascending channel 35.

[0038] The connecting channel may or may not be arranged such that the coolant flowing in close proximity to one side of the upstream battery pack flows in close proximity to the corresponding side of the downstream battery pack. For example, if the battery pack is rectangular in shape and the upstream upper branch channel 32 is arranged in close proximity to one side with respect to the direction of travel, the descending channel 34 may be arranged so that the coolant flowing in the upstream upper branch channel 32 flows along the other side of the downstream battery pack that is opposite to that side, or it may be arranged so that it flows along the same side as the upstream battery pack.

[0039] Furthermore, the connecting channels may be straight or S-shaped. For example, the descending channel 34 may be designed so that the coolant flowing through the upstream upper branch channel 32 flows diagonally downward in the vertical direction, or it may be designed so that it flows vertically downward. Similarly, the ascending channel 35 may be designed so that the coolant flowing through the upstream lower branch channel 33 flows diagonally upward in the vertical direction, or it may be designed so that it flows vertically upward.

[0040] The descending channel 34 does not necessarily have to be designed for the coolant to descend. For example, if the upstream battery pack is positioned lower than the downstream battery pack, the descending channel 34 may be designed for the coolant to rise. Similarly, the ascending channel 35 does not necessarily have to be designed for the coolant to rise. For example, if the upstream battery pack is positioned higher than the downstream battery pack, the ascending channel 35 may be designed for the coolant to descend.

[0041] The descending channel 34 and the ascending channel 35 are independent of each other. In other words, the descending channel 34 and the ascending channel 35 are designed so that the coolant flowing through them flows independently without intermingling. If the descending channel 34 and the ascending channel 35 are arranged to intersect, the connecting channel is designed to avoid contact between the channels.

[0042] For example, consider a case where the coolant flowing vertically upwards in the upstream battery pack flows vertically downwards in the downstream battery pack, and the coolant flowing vertically downwards in the upstream battery pack flows vertically upwards in the downstream battery pack. If the connecting channel is formed in a straight line, the descending channel 34 and the ascending channel 35 will come into contact when they intersect. To avoid this, either the descending channel 34 or the ascending channel 35 may be formed to curve relative to the direction of travel at the intersection of the channels. Alternatively, the descending channel 34 and the ascending channel 35 may be formed to curve in opposite directions at the intersection.

[0043] In Figure 1, the descending channel 34 is designed to be linear so that the coolant flowing through the upstream upper branch channel 32 flows diagonally downward in the vertical direction through the descending channel 34 and along the vertical lower surface of the downstream battery pack. Similarly, the ascending channel 35 is designed to be linear so that the coolant flowing through the upstream lower branch channel 33 flows diagonally upward in the vertical direction through the ascending channel 35 and along the vertical upper surface of the downstream battery pack. To avoid contact between the descending channel 34 and the ascending channel 35 along their paths, at least one or both of the connecting channels are designed to be curved in the Y-axis direction.

[0044] Next, the downstream upper branch channel 36 and the downstream lower branch channel 37 will be described. The downstream upper branch channel 36 and the downstream lower branch channel 37 are channels for cooling the downstream battery pack. Hereafter, the downstream upper branch channel 36 and the downstream lower branch channel 37 will be collectively referred to as the downstream branch channel. Explanations that overlap with those for the upstream branch channel will be omitted as appropriate.

[0045] The downstream upper branch channel 36 carries the coolant flowing through the upstream lower branch channel 33 and the upward channel 35. In other words, the upstream lower branch channel 33, the upward channel 35, and the downstream upper branch channel 36 constitute a single channel. Similarly, the downstream lower branch channel 37 carries the coolant flowing through the upstream upper branch channel 32 and the downward channel 34. In other words, the upstream upper branch channel 32, the downward channel 34, and the downstream lower branch channel 37 constitute a single channel. To put it another way, the upstream upper branch channel 32, the downward channel 34, and the downstream lower branch channel 37 constitute a first branch channel, and the upstream lower branch channel 33, the upward channel 35, and the downstream upper branch channel 36 constitute a first branch channel.

[0046] The downstream branch channel is positioned along the battery case 2 to cool the downstream battery pack. Specifically, the downstream branch channel is positioned in close proximity to a surface of the battery case 2 containing the downstream battery pack that is made of a material with high thermal conductivity. Here, the downstream branch channel may be in contact with the surface of the battery case 2, or it may be positioned at a slight gap away from the battery case 2.

[0047] The downstream upper branch channel 36 cools the downstream battery pack from a higher position than the downstream lower branch channel 37. Therefore, the downstream upper branch channel 36 is positioned higher than the downstream lower branch channel 37. In Figure 1, the downstream upper branch channel 36 is located on the vertical upper surface of the battery case 2b and cools the downstream battery pack from above. The downstream lower branch channel 37 is located on the vertical lower surface of the battery case 2b and cools the downstream battery pack from below.

[0048] In the downstream battery pack, the location where the downstream upper branch channel 36 is adjacent may or may not be the same as the location where the upstream lower branch channel 33 is adjacent in the upstream battery pack. Similarly, in the downstream battery pack, the location where the downstream lower branch channel 37 is adjacent may or may not be the same as the location where the upstream upper branch channel 32 is adjacent in the upstream battery pack.

[0049] Finally, let's explain the confluence point 38. The confluence point 38 is the point in the cooling channel 30 where the downstream upper branch channel 36 and the downstream lower branch channel 37 merge to form a single channel. The confluence point 38 is located further downstream from the downstream battery pack, that is, on the side of the coolant pump's suction port.

[0050] The confluence point 38 does not have to be located at a lower position than the downstream upper branch channel 36. Also, the confluence point 38 does not have to be located at a higher position than the downstream lower branch channel 37. In other words, the confluence point 38 and the downstream upper branch channel 36 may be at the same height. Alternatively, the confluence point 38 and the downstream lower branch channel 37 may be at the same height. The confluence point 38 may have a T-shape or a Y-shape. In Figure 1, the confluence point 38 has a T-shape and is located lower than the downstream upper branch channel 36 and higher than the downstream lower branch channel 37, where the downstream upper branch channel 36 and the downstream lower branch channel 37 are merged.

[0051] <Effects of the invention> Thus, in the battery cooling device 3 according to this disclosure, the cooling position by the upstream upper branch channel 32 in the upstream battery pack is designed to be higher than the cooling position by the upstream lower branch channel 33, and the cooling position by the downstream lower branch channel 37 in the downstream battery pack is designed to be lower than the downstream upper branch channel 36. In other words, in the upstream battery pack, the first branch channel (upstream upper branch channel 32) cools the upstream battery pack at a higher position than the second branch channel (upstream lower branch channel 33). Also, in the downstream battery pack, the first branch channel (downstream lower branch channel 37) cools the downstream battery pack at a lower position than the second branch channel (downstream upper branch channel 36). The vertical positional relationship between the first branch channel and the second branch channel is reversed via the connecting channel, i.e., the descending channel 34 and the ascending channel 35.

[0052] The effects of the battery cooling device 3 according to this disclosure will be explained using Figures 1 and 2. Figure 2 shows an example of a conventional battery cooling device. The battery cooling device according to Figure 2 differs from that according to Figure 1 in that the cooling liquid merges into a single cooling channel as it moves from the upstream battery pack to the downstream battery pack, and then branches again vertically when cooling the downstream battery pack. The other components of the battery cooling device according to Figure 2 are the same as those in Figure 1. Hereafter, components in the conventional battery cooling device according to Figure 2 that are the same as those in the battery cooling device 3 according to this disclosure will be described using the same names.

[0053] In Figure 2, for example, if the coolant pump (not shown) is operated with constant discharge pressure control, the pressure of the coolant flowing through the upstream upper branch channel and the upstream lower branch channel in the upstream battery pack will be close. Because the branching point branches the upstream upper branch channel at a higher position than the upstream lower branch channel, the flow velocity of the coolant flowing through the upstream lower branch channel becomes faster than the flow velocity of the coolant flowing through the upstream upper branch channel. Therefore, the flow rate of the coolant flowing through the upstream lower branch channel becomes greater than the flow rate of the coolant flowing through the upstream upper branch channel.

[0054] In the battery cooling device shown in Figure 2, the cooling channels between the upstream and downstream battery packs are merged into one and then branched again. Therefore, similar to the upstream side, the flow rate of the coolant flowing through the downstream lower branch channel is greater than the flow rate of the coolant flowing through the downstream upper branch channel.

[0055] If the cooling flow rate of the upper branch channel is less than that of the lower branch channel, the heat dissipation effect of the upper branch channel is lower than that of the lower branch channel, resulting in temperature unevenness within the cell. In conventional structures, the heat dissipation effect of the upper branch channel is lower than that of the lower branch channel, both upstream and downstream. Furthermore, as a result of the difference in cooling flow rates, the pressure loss caused by the lower branch channel is greater than the pressure loss caused by the upper branch channel, resulting in a difference in path pressure loss between the upper and lower branch channels.

[0056] In Figure 2, the thickness of the arrows along the upstream branch channel and the arrows along the downstream branch channel represents the number of cooling channels, and the thickness of the arrows extending above and below the battery cell (single cell) represents the magnitude of the heat dissipation effect.

[0057] On the other hand, the battery cooling device 3 shown in Figure 1 reverses the vertical positional relationship between the cooling position by the first cooling channel and the cooling position by the second cooling channel using a connecting channel. As a result, in the downstream battery pack, the difference in flow velocity and, consequently, the variation in cooling flow rate between the downstream upper branch channel 36 and the downstream lower branch channel 37 is reduced. This also suppresses variations in cooling performance between the downstream upper branch channel 36 and the downstream lower branch channel 37, thereby suppressing temperature unevenness inside the individual cells. Furthermore, by improving the flow velocity difference, the difference in path pressure loss between the first and second cooling channels can also be suppressed.

[0058] Furthermore, the battery cooling device 3 according to this disclosure can improve battery cooling performance. The battery cooling device 3 has independent downward flow channels 34 and upward flow channels 35, which increases the surface area compared to the connected flow channels in conventional battery cooling devices. This improves heat dissipation from the cooling channels. As a result, the temperature of the coolant flowing through the cooling channels decreases, improving the cooling performance of downstream battery packs.

[0059] Furthermore, the battery cooling device 3 according to this disclosure makes it possible to reduce the mounting space of the battery system 1. In conventional battery cooling devices, the connection channel between the upstream and downstream battery packs merges the upstream branch channel and then branches again into the downstream branch channel. Therefore, conventional battery cooling devices require space to consolidate and distribute the cooling channels. The battery cooling device 3 according to this disclosure does not require such space, thus making it possible to reduce the mounting space of the battery system 1.

[0060] Furthermore, the battery cooling device 3 according to this disclosure can reduce pressure loss. In conventional battery cooling devices, the connecting channel merges the upstream branch channel and then branches again into the downstream branch channel, resulting in points where pressure loss occurs due to the expansion, contraction, and bending of the cooling channel. In the battery cooling device 3 according to this disclosure, the connecting channel is composed of an independent descending channel 34 and an ascending channel 35, so there are fewer points where pressure loss occurs compared to conventional devices. Therefore, the battery cooling device 3 can reduce pressure loss.

[0061] The pressure loss reduction effect when using the battery cooling device 3 according to this disclosure can be increased as the number of battery packs cooled by a single cooling channel increases. Figure 3 is a schematic diagram of a conventional battery cooling device cooling four battery packs. Figure 4 is a schematic diagram of the battery cooling device 3 according to this disclosure cooling four battery packs. Figure 5 is an illustrative diagram of the pressure loss generated by a conventional battery cooling device and the battery cooling device 3 according to this disclosure.

[0062] When the number of battery packs cooled using a conventional battery cooling device is increased, the flow of the coolant is disturbed each time because the cooling channels must repeatedly merge and re-branch for each battery pack. As a result, the pressure loss of the entire cooling channel increases. When the number of battery packs cooled by the cooling channel 30 according to this disclosure is increased, branching and merging of the cooling channels occur between the upstream and downstream battery packs, but merging and re-branching of the cooling channels do not occur between battery packs. Therefore, as shown in Figure 5, the pressure loss reduction effect when using the battery cooling device 3 according to this disclosure can be increased as the number of battery packs cooled by a single cooling channel increases.

[0063] This disclosure is not limited to the embodiments described above, and may be modified as appropriate without departing from its intent. [Explanation of Symbols]

[0064] 1 Battery system, 2 Battery case, 3 Battery cooling device, 30 Cooling channel, 31 Branch point, 32 Upstream upper branch channel, 33 Upstream lower branch channel, 34 Downward channel, 35 Upward channel, 36 Downstream upper branch channel, 37 Downstream lower branch channel, 38 Confluence point

Claims

1. A battery cooling device equipped with a cooling channel for cooling multiple battery packs from upstream to downstream, The cooling channel comprises a first branch channel and a second branch channel for cooling the battery pack. The first branch channel cools the upstream battery pack at a higher position than the second branch channel, and cools the downstream battery pack at a lower position than the second branch channel. Battery cooling device.

2. The first branching channel flows diagonally downward in the direction of gravity from the upstream battery pack to the downstream battery pack. The second branch channel flows diagonally upward in the direction of gravity from the upstream battery pack to the downstream battery pack. The battery cooling device according to claim 1.

3. The first branch channel cools the upstream battery pack from the upper surface in the direction of gravity, and cools the downstream battery pack from the lower surface in the direction of gravity. The second branch channel cools the upstream battery pack from the bottom surface in the direction of gravity, and cools the downstream battery pack from the top surface in the direction of gravity. The battery cooling device according to claim 1.

4. The first branch channel cools the upstream battery pack at a higher position than the second branch channel, and cools the downstream battery pack adjacent to the upstream battery pack at a lower position than the second branch channel. The battery cooling device according to claim 1.

5. At least one or both of the first branch channel and the second branch channel are curved with respect to the direction of travel of the branch channel between the upstream battery pack and the downstream battery pack. The battery cooling device according to claim 3.

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