Cooling device for a battery and motor vehicle with a battery

Abstract

Method for cooling a battery (1) with a plurality of battery cells (9) by means of a cooling device with a cooling plate (7) through which a coolant can flow and which is thermally conductively connected to the battery cells (9), and with an air cooler which is used as needed to cool the battery (1) and has a cooling surface through which conditioned air and / or ambient air can flow, wherein separating elements and contact elements are provided for thermally coupling the cooling surface and the individual battery cells (9) as needed, wherein at low ambient temperatures the cooling surface is coupled in order to dissipate heat from the battery (1), and wherein at high ambient temperatures the cooling surface is decoupled in order to cool the battery (1) solely by means of the cooling plate (7).

Description

[0001] The invention relates to a method for cooling a battery with a plurality of battery cells and a motor vehicle with such a cooled battery.

[0002] Typically, a battery for use in motor vehicles, in particular in motor vehicles with a hybrid drive or fuel cell vehicles, comprises a cell block made up of several battery cells, for example lithium-ion cells, electrically connected in series and / or in parallel.

[0003] The battery cells must be cooled to dissipate the resulting heat loss. This is typically achieved by cooling them with a coolant circuit or by pre-cooled air that is directed between the cells.

[0004] With cooling via a coolant circuit, which is preferred for space reasons, a cooling plate with at least one cooling channel through which a coolant, such as a water-glycol mixture, flows is often arranged on the battery cell block. Along the battery cells, the heat is dissipated either through separate cooling rods or cooling plates or through the cell walls of the battery cells. When heat is dissipated through the cell walls, these walls are, for example, made of metal and thickened in one or more areas for better heat conduction.

[0005] Cost-effective cooling at low outside temperatures is unknown. Below approximately 5°C, the coolant in the cooling circuit no longer evaporates sufficiently. Therefore, an additional cooler is required for this temperature range. For example, a separate second coolant circuit can be used, which is connected to the first coolant circuit via a heat exchanger (a so-called chiller) and can be switched on as needed. However, this solution is complex and expensive.

[0006] DE 60 2005 003 395 T2 discloses an electric vehicle with a motor as the drive source and a battery for supplying power to the motor. The battery is mounted on a front frame of the body of the electric vehicle in such a way that a cooling surface of the battery is directly exposed to the airflow. A preferred embodiment of the battery provides cooling fins on the cooling surface.

[0007] JP 2008 059 950 A describes a battery with multiple battery cells. These are combined in a block and are in heat-conducting contact with a cooling plate. Cooling can also be achieved via air cooling, for which an air flow is driven by a fan. If the resulting noise emissions are too high, cooling is performed exclusively via the cooling plate.

[0008] US 2005 / 0 074 666 A1 discloses a cooling device for a battery. This device comprises an air cooler that can be brought into thermal contact with the individual battery cells as needed.

[0009] For further information on the state of the art, reference can also be made to DE 10 2007 017 018 A1.

[0010] The invention is based on the object of providing a cost-effective cooling method for a battery with a cooling plate through which a coolant can flow, which sufficiently cools the battery cells even at low ambient temperatures and is particularly suitable for use in a motor vehicle.

[0011] The object is achieved according to the invention by a method for cooling a battery having the features specified in claim 1 and a motor vehicle having the features specified in claim 4.

[0012] Advantageous embodiments of the invention are the subject of the subclaims.

[0013] The method according to the invention for cooling a battery with multiple battery cells utilizes a cooling plate through which a coolant can flow and which is thermally connected to the battery cells, and an air cooler that can be used as needed to cool the battery, with a cooling surface that can be exposed to conditioned air and / or ambient air. Separating elements and contact elements are provided for thermally coupling the cooling surface and the individual battery cells as needed. At low ambient temperatures, the cooling surface is coupled to dissipate heat from the battery, and at high ambient temperatures, the cooling surface is decoupled to cool the battery solely through the cooling plate.

[0014] This allows simple and cost-effective cooling of the battery cells by the air cooler at low ambient temperatures.

[0015] Furthermore, the installation space requirement is significantly reduced compared to additional cooling using a separate second coolant circuit.

[0016] The motor vehicle according to the invention comprises a battery with a plurality of battery cells and a cooling device for cooling the battery using the method according to the invention. The air cooler is arranged on an outer surface of the motor vehicle exposed to the airstream.

[0017] This has the advantage that the airflow can be used for air cooling. In vehicles where the coolant flowing through the cooling plate is controlled by the vehicle's air conditioning system, the additional advantage is that the air conditioning system is relieved of load during operating conditions in which the air cooler contributes to battery cooling.

[0018] Further advantages, features, and details of the invention are described below using exemplary embodiments with reference to the drawings. Fig. 1 a battery with a cooling device in a perspective view, Fig. 2 a battery with a cooling device in a perspective exploded view, Fig. 3 a sectional view of a battery with a cooling device at a low temperature, Fig. 4 a sectional view of a battery with a cooling device at a high temperature, Fig. 5 a sectional view of a portion of a battery with a cooling device at a high temperature, Fig. 6 schematically shows a motor vehicle with a battery in a bottom view, Fig. 7 schematically shows a motor vehicle with a battery in a side view, and Fig. 8 schematically shows a motor vehicle with a battery in a rear view,

[0019] Corresponding parts are provided with the same reference numerals in all figures.

[0020] Fig. 1 and Fig. 2 show a battery 1 with a cooling device. Fig. 1 the battery in a perspective view and Fig. 2 shows a perspective exploded view of the battery 1.

[0021] The battery 1 has a battery housing consisting of a lower housing part 2, a middle housing part 3, and a housing cover 4. The middle housing part 3 can be attached to the lower housing part 2 and the housing cover 4 by means of connecting elements 15, for example, screws or rivets. All three parts of the battery housing are made of aluminum, for example.

[0022] The electrical poles of the battery 1 are led out of the battery housing via an electrical connection unit 16.

[0023] A cell assembly comprising a plurality of battery cells 9 is arranged in the battery housing. Two battery cells 9 are electrically connected via a cell connector 17, which connects a first pole contact 18 of one of the battery cells 9, for example, its negative pole, to a second pole contact 19 of the other battery cell 9, for example, its positive pole.

[0024] An electronic unit 10 is arranged above the cell assembly, which is connected to the electrical connection unit 16 and encapsulates, for example, electronic components for cell voltage monitoring, battery control and / or fuse elements.

[0025] A cooling plate 7 is arranged beneath the cell assembly, which has a cooling channel (not shown) inside it, through which a coolant can flow. The cooling plate 7 is thermally connected to the battery cells 9. The cooling plate 7 has a coolant connection unit 8 for the introduction and removal of coolant into and from the cooling channel.

[0026] The base 5 of the lower housing part 2 is designed as an air cooler for the battery 1. For this purpose, it has cooling fins 6 on its outer side.

[0027] A heat conducting plate 11 is arranged between the cooling plate 7 and the inside of the base 5 of the housing base 2, by means of which the Fig. 3 to 5, a heat-conducting contact can be established between the base 5 of the lower housing part 2 and the cooling plate 7.

[0028] Fig. 3 and Fig. 4 show a sectional view of the battery 1, wherein the battery 1 in Fig. 3 at a low temperature and in Fig. 4 at a high temperature. Fig. 5 shows in greater detail a section of the Fig. 4 shown sectional view.

[0029] The heat-conducting plate 11 is attached centrally to the inside of the base 5 of the housing base 2. The heat-conducting plate 11 is bent upwards toward two opposite side surfaces of the housing base 2, so that its upwardly bent edge regions rest against the cooling plate 7 due to its inherent prestress.

[0030] U-shaped bimetallic elements 12 are arranged between the upwardly curved edge regions of the heat-conducting plate 11 and the base 5 of the housing base 2. A first leg 12.1 of each bimetallic element 12 is attached to the heat-conducting plate 11, and the second leg 12.2 is attached to the base 5 of the housing base 2.

[0031] The outer and inner sides of the bimetallic elements 12 are made of different metals, with the thermal expansion coefficient of the outer metal being greater than the thermal expansion coefficient of the inner metal. For example, the outer metal is aluminum and the inner metal is copper, or the outer metal is zinc and the inner metal is steel.

[0032] As a result, the bimetallic elements 12 contract as the temperature increases, so that their legs 12.1 and 12.2 move towards each other.

[0033] At sufficiently high temperatures, the force with which the bimetallic elements 12 contract exceeds the force with which the prestress of the heat-conducting plate 11 presses it against the cooling plate 7, so that the bimetallic elements 12 lift the heat-conducting plate 11 from the cooling plate 7. The heat-conducting plate 11 is elastically deformed. The temperature at which this occurs depends on the design of the bimetallic elements 12 and the prestress of the heat-conducting plate 11 and is therefore predeterminable.

[0034] The heat conducting plate 11 is preferably made of aluminum and / or copper and can be constructed from thin, superimposed individual plates to increase its flexibility.

[0035] Preferably, the bimetallic elements 12 are attached to the heat-conducting plate 11 by means of insulation mounts 13 with low thermal conductivity. For this purpose, the insulation mounts 13 are attached to the heat-conducting plate 11 and each have a pocket into which the first leg 12.1 of a bimetallic element 12 can be inserted.

[0036] In this way, the bimetallic elements 12 are thermally insulated from the heat conducting plate 11, so that their temperature is essentially determined by the temperature of the bottom 5 of the housing lower part 2 and thus by the temperature of an environment of the battery 1.

[0037] This advantageously ensures that the heat-conducting plate 11 rests against the cooling plate 7 at low ambient temperatures and conducts heat from the cooling plate to the base 5 of the lower housing part 2. Thus, at low ambient temperatures, the base 5 of the lower housing part 2 contributes to cooling the battery cells 9 via their heat-conducting contact with the cooling plate 7. At high ambient temperatures, the bimetallic elements 12 lift the heat-conducting plate 11 away from the cooling plate 7, thereby preventing thermal contact between the cooling plate and the base 5 of the lower housing part 2. At high ambient temperatures, the battery is thus cooled solely by the cooling plate 7.

[0038] Alternative embodiments of the battery 1 arise by replacing the bimetallic elements 12 with other separating elements, by means of which the heat-conducting plate 11 can be separated from the cooling plate 7 depending on the temperature. Such alternative separating elements can, for example, consist of so-called shape-memory materials or utilize the thermal expansion of liquids or gases.

[0039] The Fig. 6 to 8 schematically show a motor vehicle 14 with a battery 1 designed according to the above description. The motor vehicle 14 is in Fig. 6 in a soffit, in Fig. 7 in a side view and in Fig.8 in a rear view. The battery 1 is arranged in the rear area of ​​the motor vehicle 14 below the trunk, with the bottom 5 of the lower housing part 2 with the cooling fins 6 protruding downward from the floor of the motor vehicle, and the cooling fins 6 being oriented along a longitudinal axis of the motor vehicle 14.

[0040] As a result, the bottom 5 of the lower housing part 2 can advantageously be cooled by the wind while the motor vehicle 14 is traveling.

Claims

[1] Method for cooling a battery (1) with a plurality of battery cells (9) by means of a cooling device with a cooling plate (7) through which a coolant can flow and which is thermally conductively connected to the battery cells (9), and an air cooler which is used as needed to cool the battery (1) and has a cooling surface through which conditioned air and / or ambient air can flow, wherein separating elements and contact elements are provided for the thermal coupling of the cooling surface and the individual battery cells (9) as needed, wherein at low ambient temperatures the cooling surface is coupled in order to dissipate heat from the battery (1), and wherein at high ambient temperatures the cooling surface is decoupled in order to cool the battery (1) solely by means of the cooling plate (7). [2] Method according to claim 1, characterized by that a heat conducting plate (11) arranged between the cooling surface and the cooling plate (7) is used as at least one of the contact elements. [3] Method according to claim 2, characterized by that a bimetallic element (12) is used as at least one of the separating elements, which is fastened at a first end to the heat conducting plate (11) and at the second end to the cooling surface or cooling plate (7). [4] Motor vehicle (14) with a battery (1) with a plurality of battery cells (9) and a cooling device for cooling the battery (1) by means of a method according to one of claims 1 to 3, characterized by that the air cooler is arranged on an outer surface of the motor vehicle (14) exposed to the airstream. [5] Motor vehicle (14) according to claim 4, characterized by that the air cooler is arranged on the floor of the motor vehicle (14) in its rear area.

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