Electric vehicle battery pack

Abstract

The present invention relates to an electric vehicle battery pack, including a battery cell, an air intake duct assembly and an air intake cover, wherein the air intake duct assembly has a plurality of branch ventilation ducts, at least one of the plurality of branch ventilation ducts is bent and circuitous, and each branch ventilation duct is connected to a corresponding air intake cover; the air intake cover is internally divided into a plurality of extended-range ventilation ducts and a plurality of independent air intake areas, the front end of each extended-range ventilation duct is connected to the branch ventilation duct, and the end is connected to the corresponding air intake area, and at least one of the extended-range ventilation ducts is bent and circuitous, and the purpose of the bend and circuitous is to adjust the distance of gas flow. The beneficial effect of the present invention is that by setting the branch ventilation ducts and the extended-range ventilation ducts, the distance of each gas flow can be made very close, the time when the gas reaches each battery cell is synchronized, the temperature change of each battery cell is consistent, and the discharge depth and life of the battery pack are improved.

Description

Technical Field

[0001] The invention relates to the technical field of power batteries and energy storage batteries for electric vehicles, in particular to a battery pack for an electric vehicle. Background Art

[0002] Compared with traditional cars, electric cars can get rid of dependence on oil and have the advantages of no polluting gas emissions during use, thus protecting the urban environment. At present, China's electric cars are mainly lithium-ion battery cars, and fuel cells, metal lithium batteries and other forms of energy batteries are constantly developing. The battery pack is a key component of electric vehicles, and its quality directly affects the user experience of electric vehicles and the life of the entire vehicle. However, it also faces some development difficulties, such as insufficient safety, many fire accidents, the endurance mileage needs to be improved, the battery pack energy decays quickly, and the life is short. From the perspective of battery grouping technology, the reasons for this are:

[0003] 1. In the currently commonly used battery packs, if there is no liquid cooling or air cooling temperature control system, the temperature of the battery is difficult to control during the operation of the battery pack, and the safety is insufficient;

[0004] 2. If traditional air cooling or liquid cooling temperature control system technology is used, the temperature distribution in the battery pack is often uneven, and the temperature difference between battery cells is large, which affects the discharge depth and life of the battery pack. If liquid cooling is used, the liquid cooling pipe or liquid cooling plate often contains metal materials, which are easy to conduct electricity, and the insulation protection requirements are high. In addition, there is a risk of pipe rupture and coolant overflow or outflow, which will affect the safety of the battery pack.

[0005] 3. In the battery packs for electric vehicles with traditional air cooling solutions, due to different specific design methods and different uniformity of the battery cell surface, for most of such battery packs, the gas will be very concentrated on the surface of some battery cells, and the surface area of ​​battery cells with wind speeds above 0.01 m / s only accounts for 20% to 60% of the total surface area of ​​all battery cells. There will even be about 5% of the battery cells where the wind speed at any position is not greater than 0.01 m / s. In the current mainstream liquid cooling solution for electric vehicle battery packs, only 8% to 45% of the battery cell surface is in direct contact with the liquid cooling system. The battery cells that are not in contact with the liquid cooling system are mainly heated or cooled by conduction inside the battery cells, and the effect needs to be improved.

[0006] Therefore, it is necessary to solve the problems of difficult temperature control of electric vehicle battery packs and large temperature differences among battery cells in the battery pack. Summary of the invention

[0007] In view of the above-mentioned deficiencies in the prior art, the present invention provides an electric vehicle battery pack.

[0008] The electric vehicle battery pack provided by the present invention is realized by the following technical solutions:

[0009] An electric vehicle battery pack includes a battery cell, an air intake duct assembly and an air intake cover, wherein the air intake duct assembly has a plurality of branch ventilation ducts, at least one of the plurality of branch ventilation ducts is bent and circuitous, and each branch ventilation duct is connected to the corresponding air intake cover; the air intake cover is internally divided into a plurality of extended-range ventilation ducts and a plurality of independent air intake areas, the front end of each extended-range ventilation duct is connected to the branch ventilation duct, and the end is connected to the corresponding air intake area, and at least one of the extended-range ventilation ducts is bent and circuitous, and the purpose of the bend and circuitous is to adjust the distance of gas flow. For the gas entering each air intake area, the ratio of the minimum distance of the gas flow to the maximum distance of the gas flow from the air intake end of the air intake duct assembly to the end of the extended-range ventilation duct is not less than 80%. The air intake area of ​​the air intake cover is provided with an air hole at the bottom, through which the gas can flow to the battery cell; the air intake area has a gas guide side wall and an extended-range air hole.

[0010] The range-extending air hole is arranged at the bottom of the air intake area or the gas guide side wall, or both, and the number of the range-extending air hole is one or more; when the range-extending air hole is arranged at the bottom of the air intake area, the side surface of the hole is not completely perpendicular to the bottom surface of the air intake area.

[0011] Among the range-extending air holes, at least one range-extending air hole has a gas guide structure.

[0012] The gas guide structure is arranged at the bottom of the intake area or the gas guide side wall, or both. The structural methods include one or more of the following three structures: a gas guide protrusion, a cross-section of the intake end of the range-extending air hole being larger than the cross-section of the outlet end, and a groove in the wall.

[0013] When the gas flow guiding structure is a gas guiding protrusion, the minimum distance between the gas guiding protrusion and the range-increasing air hole is no more than 10 centimeters.

[0014] An air guide plate is arranged inside the air intake duct assembly to separate the air intake duct assembly into a plurality of branch air ducts.

[0015] It also includes an air outlet cover and a wind shield. The air inlet cover and the air outlet cover are respectively fixed on both ends of the wind shield to surround the battery cell. The air inlet cover and the air outlet cover have the same structure.

[0016] It also includes an air inlet adapter, an air outlet adapter, and an air outlet pipe assembly. The air inlet adapter is connected to the air inlet end of the air inlet pipe assembly, and the air outlet adapter is connected to the air outlet end of the air outlet pipe assembly.

[0017] It also includes an upper cover and a lower shell, and the upper cover and the lower shell are installed by bolts.

[0018] The beneficial effects of the present invention are:

[0019] 1. By setting up the extended-range ventilation ducts and branch ventilation ducts in a tortuous manner, the distance traveled by each gas flow can be made very similar, so that the gas can reach each battery cell at the same time. Through the design of air holes, extended-range air holes and gas diversion structures, the gas can flow very evenly through each battery cell, and each battery cell in the battery pack can be cooled or heated very evenly. Compared with traditional air cooling and the current mainstream liquid cooling solutions, the temperature difference between each battery cell can be greatly reduced, avoiding the problem of temperature changes at the near end first and the far end later, and can more fully release the energy of the battery pack and extend its life.

[0020] 2. In the battery pack for electric vehicles using the inventive solution, gas will pass through the surface of the battery cells very evenly. The surface area of ​​the battery cells with a wind speed above 0.01 m / s accounts for 80% to 90% of the total surface area of ​​all battery cells. 100% of the battery cells have surfaces with air flow speeds greater than 0.01 m / s. The air cooling system does not require additional metal parts around the battery cells, and the battery pack has high safety.

[0021] 3. In the liquid cooling scheme for electric vehicle battery packs, most of them adopt the liquid cooling plate scheme. The path from the liquid entering the inlet end of the liquid cooling channel that affects the battery cell to the outlet end of the liquid cooling channel that flows out is generally between 0.8 meters and 6 meters. In the invention scheme, the gas that has a direct impact on the battery cell flows from the outlet of the air inlet cover through the battery cell to the inlet of the air outlet cover. The path is generally between 0.1 meters and 0.3 meters, which greatly reduces the distance the fluid flows through each battery cell, reduces the impact of the temperature change of the fluid flowing around the battery cell on the battery cell, and reduces the temperature difference between the battery cells in the battery pack.

[0022] 4. Using the electric vehicle battery pack solution of the present invention, under the general conditions described in GB 38031-2020 "Safety Requirements for Power Batteries for Electric Vehicles" (temperature is 22°C ± 5°C), charge to cutoff with the standard charging current (1I3), and immediately discharge to cutoff with the standard discharge current (1I3), and cycle uninterruptedly for 10 times. The average temperature rise of the battery cells will be around 6°C, and the temperature difference between all battery cell surfaces will be around 3°C.

[0023] 5. The life of the electric vehicle battery pack using the solution of the present invention is expected to be 2-3 times the life of the battery pack for traditional air-cooled power vehicles, and 1.3-2 times the life of the battery pack for current mainstream liquid-cooled power vehicles.

[0024] 6. The air intake area has gas-guiding side walls and extended-range air holes, which have the following advantages: the gas-guiding side walls are arc-shaped surfaces, which can assist the gas in forming a vortex after entering the area. The gas flow velocity outside the vortex is greater than the velocity at the center, and the gas flow velocity near the side walls is greater than the velocity of the gas near the center of the area. The distance from the extended-range air holes on the side walls of the air intake area to the surface of the battery cell is greater than the distance from the air holes at other positions in the air intake area to the battery cell, thereby reducing the time difference between the air holes in the air intake area reaching the surface of the battery cell, and at the same time allowing the gas to flow through more battery cell surfaces, thereby reducing the temperature difference between the battery cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the structure of the present invention without the upper cover and the lower shell;

[0026] Figure 2 is a schematic diagram of the structure of the intake duct assembly;

[0027] Figure 3 is a cross-sectional view of an intake duct assembly;

[0028] Figure 4 It is a schematic diagram of the full section structure of the air intake cover without section lines;

[0029] Figure 5 It is a schematic diagram of the air intake cover structure;

[0030] Figure 6 It is a schematic diagram of the connection structure of the air inlet cover, the air outlet cover and the wind shield;

[0031] Figure 7 yes Figure 6 Split graph;

[0032] Figure 8 This is a schematic diagram of the entire battery pack with the upper cover opened;

[0033] Fig. 9 It is a schematic diagram of a stepped section of the air intake cover without a section line;

[0034] Fig.10 It is a full cross-section diagram of the bottom of the air intake cover without section lines. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be clearly and completely described below through embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0036] like Figures 1 to 10An electric vehicle battery pack shown includes a battery cell 1, an air intake duct assembly 2, and an air intake cover 3. The air intake duct assembly 2 has four branch ventilation ducts 21, three of which are bent and circuitous, and each branch ventilation duct is connected to the corresponding air intake cover 3; the air intake cover 3 is internally divided into six independent air intake areas A and six extended-range ventilation ducts B, each extended-range ventilation duct B is connected to the corresponding branch ventilation duct 21 at the front end, and connected to the corresponding air intake area A at the end. The extended-range ventilation duct is bent and circuitous, and the purpose of the bends and circuits is to adjust the distance of gas flow. The bottom of the air intake area of ​​the air intake cover 3 is provided with an air hole 31, and the gas can flow to the battery cell through the air hole 31. From the air intake end of the air intake duct assembly to the end of the extended-range ventilation duct, the distance of each gas flow is very similar.

[0037] like Figure 4 and Figure 5 As shown, a plurality of range-extending air holes A2 are arranged on the gas-guiding side wall A1 of the air intake area.

[0038] like Fig. 9 and Fig.10 As shown, among the range-extending air holes, a plurality of range-extending air holes have a gas guide structure. The gas guide structure is arranged at the bottom of the air intake area or the gas guide side wall, or both, and the structural methods include three structures: a gas guide boss A3, a structure A4 in which the cross section of the air intake end of the range-extending air hole is larger than the cross section of the air outlet end, and a groove A5 in the wall. The minimum distance between the gas guide boss and the range-extending air hole is not more than 10 cm. Purpose: To make the gas in the air intake area flow more evenly to the surface of the battery cell and reduce the temperature difference at different positions on the surface of the battery cell.

[0039] like Figure 3 As shown, an air guide plate 22 is provided in the air intake duct assembly 2 to separate the air intake duct assembly 2 into a plurality of branch air ducts 21 and evenly distribute the gas.

[0040] It also includes an air outlet cover 4 and a windshield guard 5. The air inlet cover 3 and the air outlet cover 4 are respectively fixed at both ends of the windshield guard 5 to surround the battery cell 1. The air inlet cover 3 and the air outlet cover 4 have the same structure. It also includes an air inlet adapter 6, an air outlet adapter 7, and an air outlet pipe assembly 8. The air inlet adapter 6 is connected to the air inlet end of the air inlet pipe assembly 2, and the air outlet adapter 7 is connected to the air outlet end of the air outlet pipe assembly 8. The air inlet adapter has the same structure as the air outlet adapter. It also includes an upper cover 9 and a lower shell 10, and the upper cover 9 and the lower shell 10 are installed by bolts 11.

[0041] In the battery packs for electric vehicles with traditional air cooling solutions, the surface uniformity of the battery cells is different due to different specific design methods. For most of these battery packs, the gas will be very concentrated on the surface of some battery cells. The surface area of ​​the battery cells with wind speeds above 0.01 m / s only accounts for 20% to 60% of the total surface area of ​​all battery cells. There will even be about 5% of the battery cells where the wind speed at any position is not greater than 0.01 m / s. In the battery packs for electric vehicles with the current mainstream liquid cooling solution, only 8% to 45% of the battery cell surfaces are in direct contact with the liquid cooling system. The battery cells that are not in contact with the liquid cooling system are mainly heated or cooled by conduction inside the battery cells. At the same time, the liquid cooling pipes or liquid cooling plates in the liquid cooling system often contain metal materials, which are easy to conduct electricity, and the insulation protection requirements are relatively high. In addition, there is a risk of pipeline rupture and coolant overflow or outflow, affecting the safety of the battery pack. In the battery pack for electric vehicles using the inventive solution, the gas will pass through the surface of the battery cells very evenly. The surface area of ​​the battery cells with a wind speed above 0.01 m / s accounts for 80% to 90% of the total surface area of ​​all battery cells. 100% of the battery cells have surfaces with air flow speeds greater than 0.01 m / s. The air cooling system does not require additional metal parts around the battery cells, and the battery pack is highly safe.

[0042] Under the general conditions described in GB 38031-2020 "Safety Requirements for Power Batteries for Electric Vehicles" (temperature is 22℃±5℃), charge to cutoff with the standard charging current (1I3), and immediately discharge to cutoff with the standard discharge current (1I3), and cycle uninterruptedly for 10 times. For a power vehicle battery pack designed with a traditional air cooling solution, the average temperature rise of the battery cells will be around 35℃, and the temperature difference between all battery cell surfaces will be around 30℃. For a power vehicle battery pack using the current mainstream liquid cooling solution, the same method is used for 10 cycles, and the average temperature rise of the battery cells will be around 16℃, and the temperature difference between all battery cell surfaces will be around 12℃. However, using the electric vehicle battery pack solution described in the present invention, the average temperature rise of the battery cells will be around 6℃, and the temperature difference between all battery cell surfaces will be around 3℃.

[0043] There is a consensus in the electric vehicle industry that the temperature difference of battery cells in an electric vehicle battery pack has a great impact on the life of the battery pack. The greater the temperature difference, the shorter the life. Since electric vehicles have not been around for very long, it is difficult to find authoritative quantitative analysis data. According to technical personnel's evaluation, the life of an electric vehicle battery pack using the solution of the present invention is expected to be 2-3 times the life of a battery pack for a vehicle powered by a traditional air-cooling solution, and 1.3-2 times the life of a battery pack for a vehicle powered by the current mainstream liquid-cooling solution.

[0044] The above-mentioned embodiments are only embodiments of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for those skilled in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Claims

1. An electric vehicle battery pack, characterized in that: It comprises a battery cell, an air intake duct assembly and an air intake cover, wherein the air intake duct assembly has a plurality of branch ventilation ducts, at least one of the plurality of branch ventilation ducts is bent and circuitous, and each branch ventilation duct is connected to the corresponding air intake cover; the air intake cover is internally divided into a plurality of extended-range ventilation ducts and a plurality of independent air intake areas, the front end of each extended-range ventilation duct is connected to the branch ventilation duct, and the end thereof is connected to the corresponding air intake area, and at least one of the extended-range ventilation ducts is bent and circuitous; an air hole is provided at the bottom of the air intake area of ​​the air intake cover, and gas can flow to the battery cell through the air hole; the air intake area has a gas guide side wall and an extended-range air hole; The range-increasing air hole is arranged at the bottom of the air intake area or the gas guide side wall, or both, and the number of the range-increasing air hole is one or more; when the range-increasing air hole is arranged at the bottom of the air intake area, the side surface of the hole is not completely perpendicular to the bottom surface of the air intake area; For the gas entering each air intake area, the ratio of the minimum distance the gas flows from the air intake end of the air intake duct assembly to the end of the extended-range ventilation duct to the maximum distance the gas flows is not less than 80%.

2. The electric vehicle battery pack according to claim 1, characterized in that: Among the range-extending air holes, at least one range-extending air hole has a gas guide structure.

3. The electric vehicle battery pack according to claim 2, characterized in that: The gas guide structure is arranged at the bottom of the intake area or the gas guide side wall, or both. The structural methods include one or more of the following three structures: a gas guide protrusion, a structure in which the inlet end cross-section of the range-extending air hole is larger than the outlet end cross-section, and a groove in the wall.

4. The electric vehicle battery pack according to claim 3, characterized in that: When the gas flow guiding structure is a gas guiding protrusion, the minimum distance between the gas guiding protrusion and the range-increasing air hole is no more than 10 centimeters.

5. The electric vehicle battery pack according to claim 1, characterized in that: An air guide plate is arranged inside the air intake duct assembly to separate the air intake duct assembly into a plurality of branch air ducts.

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