METHOD FOR COOLING A TRACTION BATTERY OF AN ELECTRICALLY DRIVE VEHICLE

Description

[0001] The invention relates to a cooling arrangement with a traction battery comprising a plurality of battery modules having the features of patent claim 1. The invention also relates to a method for operating a cooling arrangement according to the features of patent claim 3.

[0002] A cooling arrangement with the features of the preamble of patent claim 1 is known from DE 10 2013 225 521 A1. Specifically, two cooling lines containing a coolant are routed beneath several battery modules and absorb heat from the cells of the battery modules. The cooling lines run perpendicular to the cells of the battery modules, with the flow direction of the coolant in the first line running opposite to a flow direction of the coolant in the second line. The coolant transported in the cooling lines dissipates the heat generated in the traction battery. For this purpose, the cooling lines are routed in a heat-conducting manner past the cells of the battery module to be cooled. It is also proposed to connect several battery modules in series.This can be achieved by a parallel route of the cooling lines connecting the battery modules or by a meandering route of the cooling lines connecting the battery modules. A parallel connection of the cooling lines is also disclosed.

[0003] DE 10 2008 027 293 A1 discloses a device for cooling electrical storage elements (cells) of a vehicle battery. The device comprises a heat sink designed as an extruded profile with channels through which a fluid (refrigerant, coolant) flows. The cells are in thermal contact with the heat sink and transfer heat to the fluid. It is also described that the heat sink can be designed with a so-called dual-flow design, in which a first fluid (e.g. the refrigerant) flows through first channels and a second fluid (e.g. the coolant) flows through second channels of the heat sink. On the inlet and outlet sides, the channels can be connected to collectors that distribute the respective fluid flow across multiple channels. If a refrigerant circuit in the vehicle (which belongs to an air conditioning system) cannot be operated or fails, the cells can still be cooled by the coolant in the coolant circuit.

[0004] DE 10 2009 029 629 A1 discloses a heat exchanger for temperature control of vehicle batteries. Rectangular, circumferential flat tubes form chambers for accommodating battery units. A refrigerant is conveyed through the flat tubes, which are distributed via a distribution pipe and collected again via a manifold. The refrigerant flows parallel through the flat tubes in one direction. Countercurrent flow through adjacent flat tubes is also proposed.

[0005] Finally, EP 2 924 797 A1 also discloses a device for cooling a battery module. The battery module has several cells, with the temperature of each cell being controlled by a temperature sensor. Additionally, a cooling line, through which a coolant is conveyed, passes through the battery module. The cooling line can be fluidically segmented by several valves. A control unit receives signals from the temperature sensors. Depending on these signals, a drive unit for the coolant and the valves are controlled in such a way that the coolant flows through the battery module in different ways, cooling it differently depending on the temperature state.

[0006] A disadvantage of the current state of these known refrigerant evaporative cooling systems is that an insufficient supply of refrigerant leads to temperature inhomogeneity within the refrigerant transport devices, which can be designed as lines, pipes, or the like. Specifically, local overheating of the refrigerant due to complete evaporation can occur, leading to inhomogeneity in the temperature of the battery cells. The resulting temperature spread has a negative impact on the performance and service life of the battery cells. Therefore, refrigerant evaporative cooling of battery modules is generally only used when the overall thermal output from the traction battery is comparatively low. In this case, the required cooling capacity to cool the traction battery is usually available.

[0007] Future electric vehicles will have significantly higher electrical power outputs and / or require fast-charging capabilities. Without countermeasures, it is expected that operating points with insufficient cooling capacity will become more frequent, and the strain on the traction battery will increase due to temperature differences.

[0008] The present invention is therefore based on the object of providing a cooling arrangement that enables the basic prerequisite for practical and application-appropriate gradation of cooling into discrete, cooling power levels. The aim is to achieve the most uniform cooling of the traction battery possible, with a ratio of the cooling power delivered in the cooling power levels of 1:3 or 2:3 to each other, without complete evaporation of the coolant and / or local overheating occurring below or between the battery modules of the traction battery to be cooled.

[0009] Furthermore, the present invention is based on the object of providing a suitable method for operating the cooling arrangement, in which a uniform temperature control of the traction battery can be ensured even if there is insufficient cooling capacity available for cooling the traction battery.

[0010] The present objects are achieved with regard to the method by the features of patent claim 3 and with regard to the cooling arrangement by the features of patent claim 1.

[0011] Advantageous further developments or embodiments of the cooling arrangement can be found in the respective dependent claims.

[0012] In terms of process technology, the invention is based on a method for cooling a traction battery of an electrically powered vehicle, wherein a coolant is used as the cooling medium and is guided along the traction battery in a mass flow of a specific size through at least one channel. The at least one channel can be designed, for example, as a tube, flat tube, or the like. It is in thermally conductive connection with the traction battery or with individual cells of the traction battery.

[0013] It is proposed that the available cooling capacity for cooling the traction battery be determined first. The available cooling capacity for cooling the traction battery depends on the total available cooling capacity and the required cooling capacity for cooling the passenger compartment. Specifically, the available cooling capacity for cooling the traction battery is calculated from the difference between the total available cooling capacity and the required cooling capacity for the passenger compartment.

[0014] Depending on the determined available cooling capacity for cooling the traction battery, the size of the mass flow of the coolant is then regulated in such a way that either no cooling capacity is delivered to the traction battery or the cooling capacity delivered for battery cooling assumes one of several cooling power levels depending on the available cooling capacity for battery cooling.

[0015] In other words, the traction battery is either not cooled at all or only cooled at fixed or discrete power levels to be determined.

[0016] Such a process approach creates the prerequisite for controlling the location of overheating or complete evaporation of the coolant in the event of insufficient available cooling capacity for battery cooling, thus preventing temperature inhomogeneities within the battery module or within the battery cells.

[0017] The procedure can be such that the available cooling capacity for battery cooling is (control-wise) divided into several power ranges. Each power range is assigned a lower limit, with each of the predetermined power levels corresponding to the lower limit of a specific power range.

[0018] In this way, with a suitable design of the cooling arrangement for carrying out the process (see below), it can be ensured that complete evaporation and the associated overheating of the coolant only occurs in places where it can be accepted and does not lead to a temperature spread within the battery module.

[0019] In order to simplify the control process, it is proposed that only three predetermined power levels can be assumed.

[0020] It is proposed to determine the cooling capacity to be delivered in each cooling power level depending on the temperature of the traction battery. Specifically, as the battery temperature increases, the values ​​for the cooling capacity to be delivered in each cooling power level are increased. However, this is done in such a way that the ratio of the cooling capacity to be delivered in the cooling power levels always remains the same, for example, at 1:2, 1:3, or 2:3. In other words, the lower limits of the cooling power ranges are determined depending on the temperature of the traction battery and increased as the battery temperature increases.

[0021] This eliminates the need to maintain a fixed temperature difference between the traction battery cells and the coolant. This can also help simplify the process.

[0022] In particular, it is expedient if, according to a further development of the inventive concept, the available cooling capacity for battery cooling is divided into three performance ranges as follows: Performance range 1: available cooling capacity < 1 kW, Performance range 2: 1 kW < available cooling capacity < 3 kW and Performance range 3: available cooling capacity > 3 kW

[0023] The first power level does not cool the traction battery at all, the second power level with a cooling capacity of 1 kW and the third power level cools the traction battery with a cooling capacity of 3 kW.

[0024] By using such a procedure, different operating points of a traction battery can be adequately covered, while the control engineering effort can be kept within limits.

[0025] As initially mentioned, the invention is intended to provide a cooling arrangement according to claim 1.

[0026] This comprises a traction battery having a plurality of battery modules. Channels are provided through which a coolant is guided along the battery modules perpendicular to a longitudinal alignment of the battery modules. The channels are in thermally conductive connection with the battery modules or with battery cells within the battery modules. Furthermore, there is at least one first channel in which the coolant can be guided in a first direction along the battery modules to at least one connecting element and at least one second channel in which the coolant can be returned in a second direction along the battery modules. The directions or the channels are aligned parallel to one another, with the said connecting element fluidly connecting the channels to one another.

[0027] According to the method according to the invention, the cooling arrangement is operated at least in one operating mode in which the traction battery is cooled exclusively in predetermined, discrete (i.e., separate) power levels. Thus, there is no continuous or steady change in the cooling capacity; rather, cooling occurs in stages at a specific power level. In each cooling power level, the coolant is either completely evaporated after passing through the at least one first channel in the region of the connecting element, or is completely evaporated there, or only after being completely recirculated through the at least one second channel.

[0028] In this way, the cooling arrangement is optimally tailored to the process, and the advantages of the process, namely the ability to induce locally controlled overheating of the coolant and thus prevent temperature spread, are achieved. According to features of the invention, it is proposed that the channels each be thermally connected to the battery modules of the traction battery via a thermally conductive contact surface such that the area ratio of the total contact surface of the at least one incoming channel to the total contact surface of the at least one return channel is 1:2 or 2:1.

[0029] This enables a practical and application-appropriate gradation of cooling.

[0030] This is achieved in a simple manner with further features of the invention in that the dimensions of each channel and each battery module are the same and the number of incoming channels and the number of returning channels are selected such that a ratio of the incoming channels to the returning channels of 1:2 or 2:1 results.

[0031] This enables a practical and application-appropriate gradation of the cooling with a maximum of common parts.

[0032] For example, it is conceivable to have one incoming duct and two return ducts, or two incoming ducts and four return ducts, etc. In this way, a cooling capacity ratio of the effective power levels of 1 to 3 can be achieved.

[0033] Alternatively, it is conceivable to have two incoming ducts and one return duct. This design achieves a cooling capacity ratio of 2 to 3 in the effective power stages.

[0034] If a cooling capacity ratio of 1 to 2 between the effective power levels is appropriate, it is advisable to have the same number of incoming and return channels. The implementation of other cooling capacity ratios is conceivable.

[0035] To minimize the control effort for the cooling device, it is proposed that the traction battery be cooled exclusively in two power levels in this operating mode. For example, a first cooling power level can cool the traction battery with a cooling capacity of 1 kilowatt, while a second power level can cool the traction battery with a cooling capacity of 3 kilowatts. Other power level gradations are possible, as described above.

[0036] Finally, the present invention also aims to protect an electrically driven vehicle which has a cooling arrangement according to the invention.

[0037] Preferred embodiments of the invention are illustrated in the figures and explained in more detail in the following description with reference to the figures. This also makes further advantages of the invention clear. The same reference numerals, even in different figures, refer to the same, comparable, or functionally identical components. Corresponding or comparable properties and advantages are achieved even if a repeated description or reference to them is not made. The figures are not always to scale. In some figures, proportions may be exaggerated in order to more clearly emphasize features of an embodiment.

[0038] They show, schematically Fig. 1 shows a refrigerant circuit in a motor vehicle for carrying out the method according to the invention, Fig. 2 shows a flow diagram to illustrate the basic idea of ​​the method, Fig. 3 shows a further diagram to illustrate the method according to the invention, Fig. 4 shows a cooling arrangement according to the invention for carrying out the method, in a first embodiment, Fig. 5 shows an exemplary cooling arrangement, Fig. 6 shows a sectional view according to section VI from Fig. 4 and Fig. 7 an electrically driven motor vehicle with a cooling arrangement for carrying out the method.

[0039] In Fig. 1 is a refrigerant circuit 1 of a not shown, electrically driven motor vehicle K (compare Fig. 7 ) is shown.

[0040] The refrigerant circuit 1 comprises a compressor 2, which drives and compresses a refrigerant, and a condenser 3 downstream of the compressor 2, in which the compressed refrigerant is cooled. The refrigerant flows via high-pressure cooling lines 7a to a first node 8a, where the refrigerant is expanded via an expansion valve 9 and reaches an air conditioning unit 5 of the motor vehicle K. The air conditioning unit 5 serves to air-condition a vehicle cabin 6, indicated by a dashed line. The refrigerant then reaches a second node 8b via a low-pressure cooling line 7b, where it is fed back to the compressor 2. An air conditioning circuit A is formed by the aforementioned refrigerant stations.

[0041] The refrigerant that does not enter the air conditioning circuit A at junction 8a is passed via the high-pressure cooling line 7a to a second expansion valve 9, which is located upstream of an evaporator 4, where it expands. The evaporator 4 absorbs heat from a traction battery T, which causes the refrigerant to evaporate. The refrigerant is then fed via a low-pressure cooling line 7b to junction 8b and thus back to the compressor 2.

[0042] A battery cooling circuit B is formed by node 8a, evaporator 4, and node 8b. An evaluation and control device (not shown in detail) serves to control the aforementioned components of the refrigerant circuit 1 or the air conditioning circuits A and B as needed.

[0043] Based on the Fig. 2A flow chart is now used to show how a suitable evaluation and control device can control the refrigerant circuit 1, in particular the battery cooling circuit B.

[0044] In step S1, a total cooling capacity PG is first determined. The total cooling capacity PG depends, among other things, on the outside temperature, the amount of air available for the front end of the vehicle K, and the permissible speed of compressor 2.

[0045] In a step S2, an air conditioning cooling capacity PK is determined, which is necessary for air conditioning the vehicle cabin 6. The air conditioning cooling capacity PK is, among other things, a function of the air humidity and air temperature present upstream of an air conditioning evaporator, a target outlet temperature, and a target air volume for the vehicle cabin.

[0046] In a step S3, an available cooling capacity PV for battery cooling is calculated from the difference between the total cooling capacity PG and the air conditioning cooling capacity PK.

[0047] If it is determined in a step S4 that the available cooling capacity PV is within a lowest power range LB1, it is determined in a step S5 that a cooling capacity P Ist , with which the traction battery T is to be cooled, is equal to zero kilowatts.

[0048] However, if it is determined in step S4 that the available cooling capacity PV is not in the lowest power range LB1, then in a step S6 it is determined in which power range LBX the available cooling capacity PV lies.

[0049] After determining the corresponding power range LBX, in a step S7 the cooling power P Actual for cooling the traction battery T is set equal to a lower limit value P XU of the power in the power range LBX.

[0050] Fig. 3 This procedure is illustrated in a different way. In the diagram shown, the available cooling capacity PV for battery cooling and the cooling capacity P Actual with which the traction battery T is to be cooled are plotted on the vertical axis. Time t is shown on the longitudinal axis.

[0051] In a specific embodiment of the process, the control system distinguishes between three power ranges: LB1, LB2, and LB3. The first, lowest power range, LB1, covers a range of available cooling capacity PV from 0 kW to 1 kW. The second power range, LB2, covers a range of available cooling capacity PV from 1 kW to 3 kW, and the highest power range, LB3, assumes power values ​​above 3 kW.

[0052] It can be seen that up to a point in time t1, the available cooling capacity PV is within the power range LB1. This means that up to this point in time, the cooling capacity P actual is set to 0 kW ("power level" 0), which corresponds to a lower limit of the power within the power range LB1. The traction battery T is therefore not cooled at all in this operating state.

[0053] From time t1, the available cooling capacity PV enters the power range LB2, so that from time t1, the traction battery T is cooled in a cooling power level I with a cooling capacity P actual of 1 kW. This corresponds to the lower limit of the available cooling capacity PV in the power range LB2.

[0054] This continues until the determined available cooling capacity PV reaches the power range LB3 at time t2. At this point, the cooling capacity P actual for battery cooling is set to the lower limit of the available cooling capacity PV in the power range LB3. The traction battery T is then cooled in cooling power level II with a power of 3 kW.

[0055] At time t3, the available cooling capacity PV falls back to the power range LB2. The control then causes the traction battery T to be cooled again at the lower limit of the available cooling capacity PV in the power range LB2, i.e., at 1 kW.

[0056] Deviating from the specific limit values ​​and the number of performance ranges, other values ​​and numbers are of course also conceivable.

[0057] In particular, it is also conceivable, deviating from the exemplary embodiment, to determine the cooling capacity P Actual to be delivered in cooling power levels I and II depending on the temperature of the traction battery. Specifically, as the battery temperature increases, the values ​​for the cooling capacity P Actual to be delivered in a cooling power level I or II are increased. However, this is done in such a way that the ratio of the cooling capacity P Actual to be delivered in cooling power levels I or II always remains the same, for example, at 1:2, 1:3, or 2:3.

[0058] In other words, the lower limits of the cooling power ranges LB2 and LB3 are set depending on the temperature of the traction battery and are increased as the battery temperature increases.

[0059] Based on the Fig. 4A first cooling arrangement is now presented, which is adapted to the method according to the invention. The cooling arrangement comprises an evaporator 4, which is formed from channels 11, 12 for a coolant. The channels 11, 12 are held in heat-conducting contact with battery modules B1 to B4 of a traction battery T.

[0060] The battery modules B1 to B4 are cuboid-shaped in a known manner, each with the same dimensions and a longitudinal orientation I1. Each of the battery modules B1 to B4 has several battery cells (not shown in detail), which can preferably be Ni / MeH or Li-ion cells. Such cells are particularly well suited as electrochemical energy storage devices.

[0061] In the exemplary embodiment, channels 11, 12 are components of so-called flat tubes FR with a longitudinal orientation I2. Each flat tube FR is thus traversed by a channel 11 or 12 transporting the coolant. The flat tubes FR are constructed identically and run parallel beneath the battery modules B1 to B4. Each flat tube FR has a heat-conducting contact surface F1 or F2 with the battery modules B1 to B4 (see Fig. 6 ). Due to the aforementioned structural similarity of both the flat tubes FR and the battery modules B1 to B4, the contact surfaces F1 and F2 are identical. Furthermore, the longitudinal alignment I1 of the battery modules B1 to B4 is perpendicular to the longitudinal alignment I2 of the flat tubes.

[0062] The Figures 4 and 6The central flat tube FR, visible in the drawing, has a channel 11 leading to a connecting element 13. Furthermore, there are two outer flat tubes FR, each with a channel 12, which carries a refrigerant, which is guided via channel 11 to the connecting element 13, back in the opposite direction. The connecting element 13, which in the exemplary embodiment is designed as a collecting pipe, thus connects the channel 11 carrying the refrigerant with the channels 12 carrying the refrigerant back.

[0063] To carry out the method according to the invention with the Fig. 3 Given the specific performance limits, the cooling arrangement is now designed as follows: If an available cooling capacity PV is available that is within the power range LB1, no mass flow of refrigerant is directed into channel 11 via an unspecified inlet. Therefore, the traction battery T is not cooled.

[0064] If an available cooling capacity PV is available in the power range LB2, the mass flow of the coolant is regulated such that the traction battery T is cooled with a cooling capacity P actual of 1 kW. In the exemplary design of the cooling arrangement, this means that the coolant entering the incoming channel 11 is dimensioned such that it is only completely evaporated in channel 11 in a first evaporation region V1, which lies downstream of the battery modules B1 to B4 in the direction of flow of the coolant. In this way, homogeneous heat dissipation between the traction battery T and the channel 11 can be ensured over the entire length of the channel 11 thanks to a sufficient amount of available, not yet evaporated coolant. Temperature differences between the battery modules B1 to B4 or between their individual cells do not occur.

[0065] The refrigerant evaporated in the evaporation zone V1 then enters the connecting element 13 and is transported back to unspecified outlets via the return channels 12. During the return process, the refrigerant no longer absorbs heat due to its already gaseous state and thus no longer changes the temperature state of the traction battery T, or at least not significantly.

[0066] However, if the available cooling capacity PV reaches the third power range LB3, the mass flow of the refrigerant increases abruptly such that the cooling capacity P Actual for battery cooling is increased to 3 kW. The refrigerant flow is then so high that the refrigerant does not completely evaporate in the first evaporation zone V1, but rather, liquid refrigerant enters the connecting element 13, from there enters the return channels 12, and is transported back through the channels 12. The refrigerant continues to absorb heat from the traction battery T until it has completely evaporated in the channels 12 in a second evaporation zone V2.

[0067] The cooling arrangement is therefore designed in such a way that when the method according to the invention is carried out, complete evaporation of the coolant and thus local overheating, which can lead to inadmissible or harmful temperature differences, does not occur at any point below or between the battery modules B1 to B4.

[0068] In the embodiment shown, the cooling arrangement is further designed such that a cooling capacity ratio of the first effective power level I in the power range LB2 to the second effective power level II in the power range LB3 of 1:3 results.

[0069] The distribution of the cooling capacity P Actual in such a ratio meets the expected requirements while allowing for a simple and therefore cost-effective design of the cooling arrangement, since only one flat tube FR outward and two flat tubes FR inward need to be implemented. Furthermore, such a cooling arrangement avoids the need for complex temperature sensors.

[0070] Alternatively, other ratios of the cooling capacity P Ist are also conceivable. For example, it is conceivable to provide two incoming channels 11' and only one return channel 12' (compare also Fig. 4 ). Such a design results in a cooling capacity ratio P Actual in the aforementioned capacity ranges LB2 and LB3 of 2:3. Such a gradation can be quite useful for certain applications.

[0071] Based on the Fig. 5 A cooling arrangement is shown in which, in contrast to the Fig. 4only one flat tube FR with an incoming channel 11 and one flat tube FR with a return channel 12 are present. With this design, a cooling capacity ratio P Actual of 1:2 can be achieved.

[0072] For example, it is conceivable that in connection with the interpretation according to Fig. 5 the method is designed in such a way that, with regard to the available cooling capacity PV, a first power range LB 1 from 0 kW to 1.5 kW, a second power range LB2 from 1.5 kW to 3 kW and a third power range LB3 above 3 kW are implemented in terms of control technology.

[0073] If the available cooling capacity PV falls into the first, lower power range LB1, the refrigerant mass flow is again regulated to 0 and the traction battery T is not cooled at all. If the available cooling capacity PV is in the power range LB2, the traction battery T is cooled in a first cooling power stage with a cooling capacity P actual of 1.5 kW. If the available cooling capacity PV is in the third power range LB3, the traction battery T is cooled in a second cooling power stage with a cooling capacity P actual of 3 kW.

[0074] Here too, the coordinated design of the cooling arrangement contributes to the fact that with a cooling capacity P Ist of 1.5 kW, the refrigerant in channel 11 is only completely evaporated in the evaporation area V1 and with a cooling capacity P Ist of 3 kW, only in channel 12, specifically in the evaporation area V2.

[0075] Finally, the Fig. 7 an electrically driven motor vehicle K (electric vehicle), which has an evaporator 4 with a Fig. 4 The traction battery T of the motor vehicle K can therefore be cooled using the method according to the invention. LIST OF REFERENCE SYMBOLS

[0076] 1Refrigerant circuit 2Compressor 3Condenser 4Evaporator 5Air conditioning unit 6Vehicle cabin 7a, 7bCooling lines 8a, 8bNodes 9Expansion valves 11, 11'Incoming channel 12, 12'Return channel 13Connecting element; collecting pipe AClimatization circuit BBattery cooling circuit B1-B4Battery modules F1, F2Heat-conducting contact surfaces FRFlat tubes KElectrically powered motor vehicle I1, I2Longitudinal alignment LB1-LB3Power ranges LBXPower range PG Total cooling capacity P Actual cooling capacity used to cool the battery PK Air conditioning cooling capacity PV Available cooling capacity for battery cooling P XU Lower limit of the power in the power range LBX S1-S7Steps tTime t1-t3Time points TTraction battery V1First evaporation area V2Second evaporation area 0Non-cooling power level ICooling power level IICooling power level

Claims

1. Cooling arrangement, comprising a traction battery (T) having a plurality of battery modules (B1-B4), wherein a refrigerant is guided along said modules through channels (11, 12; 11', 12') perpendicularly to a longitudinal orientation (11) of the battery modules (B1-B4) and the channels (11, 12; 11', 12') are thermally conductively connected to the battery modules (B1-B4), wherein at least one first channel (11; 11') is present in which the refrigerant can be guided in a first direction along the battery modules (B1-B4) to at least one connecting element (13) and at least one second channel (12; 12') in which the refrigerant can be guided back again in a second, opposite direction along the battery modules (B1-B4), the directions being oriented in parallel with one another and the connecting element (13) fluidically interconnecting the channels (11, 12; 11', 12'), characterized in that an evaporator (4) for the refrigerant is formed from the channels (11, 12; 11', 12'), the channels (11, 12; 11', 12') being part of identical flat tubes (FR) having a longitudinal orientation (I2), the flat tubes (FR) each having a thermally conductive contact surface (F1, F2) and being guided along in parallel under the battery modules (B1-B4), the battery modules (B1-B4) being cuboid-shaped with the same dimensions and a longitudinal orientation (11) of the battery modules (B1-B4) being perpendicular to the longitudinal orientation (I2) of the flat tubes (FR), the flat tubes (FR) each being thermally conductively connected to the battery modules (B1-B4) of the traction battery (T) via the thermally conductive contact surface (F1, F2) such that an area ratio of the total contact surface (F1) of the at least one supply channel (11, 11') to the total contact surface (F2) of the at least one return channel (12; 12') is 1:2 or 2:1, wherein exactly three flat tubes (FR) are present of which a middle flat tube (FR) has at least one supply channel (11) and of which two outer flat tubes (FR) each have at least one return channel (12), or of which two outer flat tubes (FR) each have at least one supply channel (11') and of which a middle flat tube (FR) has at least one return channel (12').

2. Electrically drivable vehicle (K), characterized by at least one cooling arrangement according to claim 1.

3. Method for operating a cooling arrangement according to claim 1, characterized in that the cooling arrangement is operated at least in such an operating mode in which the traction battery (T) is cooled exclusively in predetermined, discrete power levels (I, II), wherein there is no continuous or constant change in the cooling power (Pist), but rather the cooling takes place in stages with a specific power level (I, II), wherein in each cooling power level (I, II) the refrigerant has either already completely evaporated in the region of the connecting element (13) after being guided through the at least one first channel (11; 11') or is completely evaporated there or is evaporated only after being completely returned through the at least one second channel (12; 12').