COOLING DEVICE FOR A VEHICLE BATTERY

Description

[0001] The invention relates to a cooling device for a vehicle battery, in particular for a battery in which electrical energy can be stored to supply a traction device of a rail vehicle.

[0002] Vehicles of various types can be electrically powered and often require energy storage unless they are permanently connected to an external electrical supply. Such energy storage devices are typically referred to as vehicle batteries, although this term also includes accumulators. For example, rail vehicles that travel entirely or partially on routes that are not electrified via an overhead line or a third rail are increasingly being equipped with energy storage devices, known as traction batteries. The electrical energy stored in these traction batteries is used to supply drive components and, if necessary, the rail vehicle's auxiliary systems while traveling on a non-electrified section of track.The traction batteries are charged, for example, while driving on an electrified section of track, at special charging stations or via another energy device on board, such as a fuel cell.

[0003] A traction battery typically consists of a large number of electrically interconnected battery cells or battery cell modules with high performance and energy density. To achieve a long battery cell service life, which is particularly important for rail vehicles with a target service life of up to 30 years, the battery cells must be operated within a defined temperature range. This temperature range depends, among other things, on the battery cell materials and can, in particular, be below the ambient temperature. For example, if the preferred battery cell temperature is 25 °C, at ambient temperatures well below 25 °C the battery can be cooled directly with ambient air or indirectly via a heat transfer medium and a heat exchanger with ambient air.At higher ambient temperatures, direct or indirect cooling with ambient air is not sufficient to maintain the temperature range. For adequate cooling, a refrigeration system based on the compression refrigeration principle, for example, must be used, which can cool the battery cells to temperatures below ambient temperatures.

[0004] However, operating the chiller is very energy-intensive. Furthermore, low ambient temperatures can force the chiller's refrigerant compressor to operate in an operating range that is very unfavorable for its service life.

[0005] From EP 1 266 779B1, it is known to provide (indirect) cooling with ambient air in addition to a refrigeration unit. This additional cooling requires an additional cooler in the system. The described vehicle cooling circuit comprises a refrigerant circuit and a cooling circuit with a component to be cooled and a cooler. At sufficiently low ambient temperatures, the cooling of the component to be cooled, for example a traction battery, can be achieved solely via the cooler in the cooling circuit. At high ambient temperatures, the refrigeration unit is activated, which can then additionally cool the coolant in the cooling circuit. A disadvantage is that an additional cooler is required for cooling without operating the refrigeration unit, as disclosed in patent application DE102008057305 A1 (Behr GmbH & CO KG).

[0006] On a vehicle, it increases manufacturing costs, weight, and space requirements. Furthermore, the radiator must be constantly circulated by air, which requires a powerful fan.

[0007] The magazine Kälte Klima Aktuell, issue 04 / 2016, presents a cooling system for stationary cooling, e.g., of IT equipment. This system essentially consists of a refrigeration machine with CO2 as the refrigerant, enhanced with additional components. During conventional operation of the refrigeration machine, the refrigerant compressor is in operation, and the system operates like a conventional compression refrigeration machine. At sufficiently low ambient temperatures, the refrigerant compressor can be switched off, and the additional components are required instead; in particular, a pump is switched on and a valve is opened. This pump must generate a relatively high pressure difference between the suction and discharge sides, and a minimum volume flow must be ensured.

[0008] However, such a solution is not suitable for the special requirements of battery cooling in a vehicle. Especially for use in rail vehicles, the required pressure of the CO2 refrigerant is typically up to 150 bar. Since the CO2 refrigerant would have to be passed through the batteries to evaporate there, very high pressure resistance and tightness would be necessary in the extensive system of battery cells and the cooling channels in between. This would be technically impossible or only possible with great effort. Furthermore, the battery and battery cooling system are often located at different locations on a vehicle, meaning that the connecting lines would also have to meet these high requirements. CO2 is also not very effective in applications with high ambient temperatures.

[0009] The object of the invention is to provide a cooling device which is suitable for cooling a battery of a vehicle, in particular a rail vehicle, which can be operated in an energy-efficient manner and which can be implemented with little technical effort.

[0010] This object is achieved by a cooling device according to claim 1 and by a method having the features of claim 19.

[0011] Advantageous embodiments of the invention are specified in the subclaims.

[0012] The cooling device according to the invention has a refrigerant circuit and a coolant circuit, which are coupled via a heat exchanger. The vehicle battery is in thermal contact with the cooling circuit and is therefore cooled by it. The refrigerant circuit comprises a condenser, a refrigerant pump arranged downstream thereof, an expansion valve arranged further downstream or parallel to the refrigerant pump, an evaporator arranged even further downstream, which is designed as a heat exchanger with the coolant circuit, and a compressor arranged even further downstream. The refrigerant circuit further comprises a sensor, which is used to control the refrigerant flow. A bypass to the refrigerant pump is provided. Furthermore, a bypass to the compressor is provided.The solution with an expansion valve and refrigerant pump connected in series is referred to below as the first variant, and the solution with an expansion valve and refrigerant pump connected in parallel is referred to as the second variant.

[0013] With the cooling device according to the invention, a vehicle battery can be cooled efficiently, whereby the compressor does not have to be operated at low ambient temperatures.

[0014] At high ambient temperatures, the cooling system operates like a conventional compression refrigeration machine, with the compressor operating. The compressor pumps the gaseous refrigerant to the condenser, increasing the refrigerant's pressure and temperature.

[0015] The refrigerant condenses in the condenser. The liquid refrigerant is fed via the refrigerant pump's bypass and the expansion valve to the evaporator, where it evaporates, thereby cooling the coolant in the coolant circuit. The expansion valve is adjusted so that the refrigerant evaporates completely in the evaporator, possibly resulting in slight overheating (depending on the refrigerant and compressor type). The cooled refrigerant is then pumped to cool the vehicle battery.

[0016] At low ambient temperatures, the compressor can be shut down. The refrigerant pump is switched on, and the bypass to the refrigerant pump is closed. The refrigerant pump then pumps the liquid refrigerant—in a solution according to the first variant, also via the expansion valve—to the evaporator, where it cools the coolant circulated by the refrigerant pump. The gaseous refrigerant is fed from the evaporator outlet via the compressor bypass to the condenser. There, due to the low ambient air temperature, it condenses without the pressure increase generated by the compressor in conventional operation.

[0017] The refrigerant flow through the refrigerant pump can be controlled using a sensor by controlling a valve in the refrigerant flow and / or the refrigerant pump.

[0018] If the maximum possible cooling capacity is to be achieved, the control is carried out using the sensor in such a way that the refrigerant is completely evaporated at the outlet from the evaporator but is preferably not yet overheated, or in such a way that there is sufficient liquid in every operating situation so that no gaseous refrigerant reaches the pump.

[0019] Examples of ensuring complete evaporation: In one embodiment, a sensor is used which is also used to control the expansion valve. Advantageously, this eliminates the need for an additional sensor to control the refrigerant flow. Such sensors measure pressure and temperature and have corresponding sensor components; it is also possible for a sensor component to be arranged at the inlet of the evaporator. Using the sensor measurements, the expansion valve is adjusted accordingly, thereby controlling the refrigerant flow; preferably, an electronic expansion valve is used. However, another controllable valve can also be provided, which is arranged upstream or downstream of the refrigerant pump. Using the sensor measurements, the refrigerant pump, i.e. its delivery rate, can also be controlled or regulated.

[0020] Examples of ensuring sufficient liquid refrigerant at the inlet of the refrigerant pump: In one embodiment, a level sensor upstream of the refrigerant pump, preferably on a receiver, can be used for control. Using the sensor readings, the refrigerant pump can be adjusted accordingly, thereby controlling or regulating the refrigerant flow. Liquid refrigerant may still be present at the evaporator outlet. However, this is harmless because the refrigerant compressor is not running and therefore cannot be damaged by the liquid refrigerant. On the other hand, flooding the evaporator can increase the cooling capacity. In one embodiment, the sensor readings are used to adjust a controllable valve located upstream or downstream of the refrigerant pump.

[0021] According to one embodiment, the control or regulation can also be carried out in such a way that a slight superheat (e.g. +7 Kelvin) is present at the outlet from the evaporator.

[0022] During partial load operation, the pump's flow rate or the controllable valve can be further throttled, causing the refrigerant in the evaporator to overheat and providing correspondingly less cooling capacity. To control the pump accordingly, a speed control, for example, or active throttling or active recirculation can be used.

[0023] In all cases, a processing unit can be provided between the sensor and the valve or pump to control valves or the refrigerant pump, generating appropriate control commands from the sensor readings. A closed-loop control system can also be provided, for which the processing unit is appropriately designed.

[0024] In typical applications for traction batteries for rail vehicles, with R134a as the refrigerant and water or a water-glycol mixture as the coolant, low ambient temperatures are understood to mean a temperature below 15°C and preferably below 10°C. For other applications, the temperature ranges may be higher or lower.

[0025] Preferably, at least one fan is provided which conveys ambient air to the condenser and thus supports the condensation.

[0026] According to another embodiment, the refrigerant pump bypass is designed as a refrigerant line with a first valve, in particular a shut-off valve. However, a refrigerant pump can also be used that is permeable to the refrigerant even when not in operation (i.e., the refrigerant line can be omitted); this is referred to below as an "integrated bypass." This term also includes a solution in which the refrigerant's path through the pump is the same as that of the pump in operation.

[0027] The refrigerant pump is preferably dimensioned so that the minimum flow rate of the pump is not undercut, even at low cooling capacities and with the correspondingly strong throttling of the refrigerant flow rate by the expansion valve. Partial recirculation of the liquid refrigerant via a throttle, as in the prior art, can be omitted. Alternatively or additionally, a refrigerant pump with variable speed control can be used.

[0028] The bypass to the compressor can be designed as a refrigerant line with a second valve. However, a compressor can also be used that allows the refrigerant to flow even when the compressor is not running (i.e., the refrigerant line can be omitted). This is referred to below as an "integrated bypass." This term also includes a solution in which the refrigerant's path through the compressor is the same as that of the operating compressor.

[0029] In solutions according to the second variant, it is advantageous to provide a valve upstream or downstream of the refrigerant pump if the pump is permeable to the refrigerant when not in operation and a parallel refrigerant line is to be used as a bypass. If the pump is impermeable to the refrigerant when not in operation, this valve can be omitted. If the valve is designed as a controllable reducing valve, it can be used for the inventive control or regulation of the refrigerant flow.

[0030] It is advantageous to include a receiver for the condensed refrigerant in the refrigerant circuit, especially one with a level sensor if the additional weight is acceptable. This allows for better process optimization.

[0031] In a further embodiment, an internal heat exchanger is provided in the refrigerant circuit. This heat exchanger couples two sections of the refrigerant circuit together, namely a first section downstream of the condenser with a second section upstream of the compressor, thereby cooling the liquid refrigerant and heating the gaseous refrigerant.

[0032] According to further embodiments, multiple refrigeration circuits can be provided. These can be nested, i.e., the condensers are arranged in series on the air side, so that the cooling air passes through the condensers one after the other, and the evaporators are arranged in series on the coolant side in reverse order.

[0033] Other embodiments provide for the arrangement of several refrigeration circuits in parallel. In this case, only one condenser is used, through which a cooling air stream and several materially separated refrigerant streams of the individual refrigeration circuits flow. The numerous channels into which the refrigerant streams of the respective refrigeration circuits are distributed are preferably distributed evenly across the volume of the condenser. This has the advantage that the full heat exchanger surface is provided on the air side for each individual refrigeration circuit, thus increasing the efficiency of the refrigeration circuits remaining in operation when one or more refrigeration circuits are shut down.

[0034] The coolant circuit may comprise several vehicle batteries to be cooled, which are connected in series and / or parallel.

[0035] Depending on the spatial conditions, the refrigerant pump may be omitted if the necessary pressure can be generated by other means. For example, in a rail vehicle, the condenser, compressor, and compressor bypass—and, if applicable, the compressor bypass—can be connected to the same system.

[0036] The fan and receiver can be mounted higher, for example, on the roof of the rail vehicle. The evaporator and expansion valve, as well as any third valve, can be mounted lower, for example, directly on or below the car body floor. The coolant pump and the vehicle battery to be cooled are also preferably located on or below the car body floor. The refrigerant pump and, if applicable, the first valve in the refrigerant pump bypass can be omitted.

[0037] Common refrigerants can be used, especially natural or synthetic refrigerants suitable for normal cooling (cooling temperatures above 0 °C) on vehicles. For example, the refrigerants R134a, R407c, or the more environmentally friendly variant R290, commonly used in rail vehicles, can be used.

[0038] The modifications mentioned can be combined with each other and, in particular, are generally applicable to both variants. Depending on the operating conditions (vehicle type with specified installation space, ambient temperature, refrigerant, battery type, etc.), an optimal design can be found. Advantages:

[0039] The cooling device according to the invention enables energy-efficient cooling of a vehicle battery, particularly in rail vehicles, with minimal equipment complexity. Only a small refrigerant pump is used, and in typical applications, a drive power of less than 1W per 1000W of cooling capacity is sufficient.

[0040] By controlling the refrigerant flow through the refrigerant pump, both variants enable optimal utilization of the evaporator and condenser, even under varying ambient conditions. This increases cooling capacity. Furthermore, cooling capacity can be reduced at partial load using the pump's flow rate. The refrigerant pump requires only a small amount of space and is lightweight compared to the other components.

[0041] The coolant pump is also small and, like the refrigerant pump, can be integrated into the existing cooling system's free space, eliminating the need for additional installation space. An additional cooler in the coolant circuit is also unnecessary.

[0042] By using the cooling circuit separate from the refrigerant circuit, the coolant circuit can be adapted to a wide range of boundary conditions, in particular spatial conditions or the number of vehicle batteries.

[0043] A further advantage is that there is generally no restriction to a specific refrigerant. The invention can be used with refrigerants known from vehicle cooling, particularly rail vehicles.

[0044] The invention is explained in more detail below using exemplary embodiments.

[0045] They show: Fig.1 the cooling device according to the invention according to the first variant Fig.2 the cooling device according to the invention according to the second variant Fig. 3 - 9 further embodiments of the invention

[0046] In the Figure 1In the illustrated embodiment according to the first variant, the cooling device has a refrigerant circuit 20 and a coolant circuit 21, which are coupled via a heat exchanger 8. The refrigerant circuit 20 comprises a condenser 3 and an optional collector 4 arranged downstream thereof. The refrigerant circuit further has, viewed in the direction of flow, a refrigerant pump 6 with a bypass, which is designed as a refrigerant line 15 running parallel to the pump 6 and having a first valve 5, preferably a shut-off valve; the refrigerant line 15 and the first valve 5 can be omitted if the refrigerant pump is permeable to the refrigerant even when at a standstill (integrated bypass). Downstream of the refrigerant pump 6, an expansion valve 7 is arranged, which is connected to a sensor 13 and is controlled by it; a processing unit not shown in the figure can also be present for this purpose.

[0047] An evaporator 8 is arranged between expansion valve 7 and sensor 13, which functions as a heat exchanger with the coolant circuit 21. Downstream of the evaporator 8 are a compressor 2 and a bypass to the compressor, which is designed as a refrigerant line 16 running parallel to the compressor 2 and has a second valve 10, in particular a shut-off valve. The sensor 13 and the expansion valve 7 control the refrigerant flow at high and low ambient temperatures.

[0048] The coolant circuit 21 has a coolant pump 11 and runs through a vehicle battery 12 so that it can cool it.

[0049] At high ambient temperatures, the compressor 2 is in operation and the system works like a conventional compression refrigeration machine. The compressor 2 conveys the gaseous refrigerant to the condenser 3 and increases the pressure and temperature of the refrigerant. The condenser 3 is cooled by the ambient air flow 9 conveyed by a fan 1 and thus condenses the refrigerant. The condensed refrigerant flows into the receiver 4, from where it is led via the open first valve 5 to the expansion valve 7. Controlled by the sensor 13, the expansion valve 7 (i.e. the refrigerant flow) is preferably adjusted such that the refrigerant is only in gaseous form when it enters the compressor 2. In the evaporator 8, the refrigerant evaporates and thereby cools the liquid coolant, which is led from the battery 12 to the evaporator 8 via the coolant pump 11.

[0050] At low ambient temperatures, compressor 2 is switched off and instead refrigerant pump 6 is switched on, second valve 10 in compressor bypass line 16 is opened, and first valve 5 in refrigerant pump bypass line 15 is closed. Pump 6 then pumps the liquid refrigerant via expansion valve 7 to evaporator 8, where it cools the coolant circulated by coolant pump 11. Refrigerant pump 6 is preferably dimensioned such that, even with low cooling capacities and correspondingly strong throttling of the refrigerant flow rate by expansion valve 7, the pump's minimum flow rate is not undercut. This advantageously eliminates the need for partial recirculation of the liquid refrigerant via a throttle (or a corresponding feature of first valve 5). To ensure this, speed control of the refrigerant pump can also be used.The gaseous refrigerant flows into the condenser 3 via the open second valve 10. There it condenses due to the low temperature of the ambient air 9 even without an increase in pressure.

[0051] If the maximum possible cooling capacity is to be achieved, the expansion valve is controlled with the help of sensor 13 such that the refrigerant has completely evaporated at the outlet from the evaporator 8 but is preferably not yet overheated. Alternatively, it is possible to control the delivery rate of the pump 6 with the help of a level sensor (not shown) on the receiver 4, preferably using a speed control, and thus ensure that there is sufficient liquid in every operating situation so that no gaseous refrigerant reaches the refrigerant pump 6. When the compressor 2 is at a standstill, any liquid refrigerant present at the compressor inlet is harmless. For partial load operation, the expansion valve or, alternatively, the delivery rate of the refrigerant pump is further throttled.

[0052] Figure 2shows an embodiment of the second variant, in which the arrangement of the expansion valve 7 is different from the first variant. The expansion valve 7 is arranged in the bypass line 15 of the refrigerant pump 6, i.e., parallel to the refrigerant pump. The basic mode of operation at high or low ambient temperatures corresponds to that in connection with Figure 1explained. A third valve 14 is connected in series with the refrigerant pump; at high ambient temperatures, it can be used to prevent the flow of refrigerant through the non-operational pump 6. Since the expansion valve 7 is bypassed during pump operation, it can be designed conventionally, e.g. as a so-called thermostatic expansion valve, and does not have to be suitable for being sufficiently open during pump operation. Assuming typical pressure losses through the evaporator, condenser, and piping of a refrigeration machine, a drive power of the refrigerant pump of less than 1 W per 1000 W of cooling power is sufficient. The refrigerant pump 6 is correspondingly small and only insignificantly increases the weight of the cooling system.

[0053] The refrigerant flow is controlled by a sensor 19 on the collector, which controls the refrigerant pump 6.

[0054] For illustrative purposes only, Figure 2Examples of temperature values ​​of the refrigerant or coolant at various points in the respective circuit are given, specifically for so-called compressor operation at high ambient temperatures (marked with V) and for so-called pump operation at low ambient temperatures (marked with P) when using propane as the refrigerant and water as the coolant. In the given example, at low ambient temperatures of 0°C, the refrigerant after the condenser 3 has a temperature of 10°C and can cool the coolant to 20°C in the evaporator. This ensures the optimal operating temperature of the vehicle battery 12. Depending on the dimensioning of the cooling device and the design of its individual components, other values ​​may apply in a system according to the invention.

[0055] Figure 3shows an embodiment in which the collector 4 is omitted. This makes the design simpler and even more space-saving. The refrigerant flow is controlled using sensor 13, which controls or regulates the refrigerant pump 6.

[0056] Figure 4 shows an embodiment in which the compressor 2 has an integrated bypass. At low ambient temperatures, the refrigerant is passed through the compressor 2 without the compressor being in operation. An additional refrigerant line 16 and the second valve 10 can therefore be omitted. The control or regulation of the refrigerant flow is carried out as in Figure 2 using a level sensor 19.

[0057] According to another embodiment, a refrigerant pump is used which is impermeable to the refrigerant when at a standstill, so that the third valve 14 can be omitted.

[0058] According to a further embodiment, an expansion valve is used that can additionally assume the function of the first valve 5, for example, an electronic expansion valve. In this case, the first valve 5 can be omitted.

[0059] Figure 5 shows an embodiment in which the collector 4 is omitted. The refrigerant flow is controlled by a sensor 18 located at the evaporator outlet. This sensor measures the pressure and temperature of the refrigerant in a similar manner to the expansion valve sensor 13. The third valve 14 is controlled or regulated based on the measured values.

[0060] Figure 6shows an embodiment in which two refrigeration circuits 20, 20a are nested and, in addition, two vehicle batteries 121, 122 are cooled in the coolant circuit. The condensers 3, 3a are arranged in series on the air side, and the evaporators 8, 8a are arranged in series on the coolant side in reverse order. The second refrigeration circuit 20a can be constructed similarly to the first refrigeration circuit. The vehicle batteries 121, 122 can be arranged in parallel as shown here. Due to the counter-rotating series connection of the evaporators and condensers, the refrigeration circuits operate at different temperature levels (in the case shown, the left one at a slightly higher temperature than the right one). This creates a cascade connection, which leads to higher performance and efficiency.

[0061] The control of the refrigerant flow takes place in both refrigerant circuits; for the sake of clarity, it is not shown here or in the following figures.

[0062] Figure 7 shows an embodiment in which two refrigeration circuits 20, 20a are arranged in parallel and which has a condenser 3 with nested refrigerant flow. The condenser 3 with nested refrigerant flow provides the full heat exchanger surface on the air side when only one refrigeration circuit is operating. This can be done in the same way as the Figure 1 - 5 explained embodiments can be provided with a cooling circuit with several vehicle batteries 121, 122, wherein the vehicle batteries can be connected in parallel and / or in series.

[0063] Figure 8 shows an embodiment with a cooling circuit 20 of the second variant and a cooling circuit with two vehicle batteries 121, 122 connected in series. This is a simple and advantageous embodiment if the vehicle batteries have different optimal operating temperatures from one another.

[0064] Figure 9shows an embodiment with an internal heat exchanger 17 that couples two sections of the refrigerant circuit. This cools the liquid refrigerant and heats the gaseous refrigerant upstream of the compressor.

[0065] Figure 10 shows an embodiment in which the condenser 3, the compressor 2, and any components present, such as the compressor bypass line 16, the fan 1, and the collector 4, are arranged on the roof of a rail vehicle 23. The evaporator 8 and the expansion valve 7, as well as the third valve 14 parallel to the expansion valve, can be arranged beneath the car body floor. The coolant pump 11 and the vehicle battery 12 to be cooled are then also housed beneath the car body floor. Due to the height difference, the necessary pressure builds up to circulate the refrigerant, so that the refrigerant pump 6 and the first valve 5 can be omitted.

Claims

1. Cooling device for a vehicle battery, - with a coolant circuit (21), which comprises a coolant pump (11) and is in thermal contact with the vehicle battery (12), - with a refrigerant circuit (20), which has: - a condenser (3), - a refrigerant pump (6), which is arranged downstream of the condenser (3), - a sensor (13, 18, 19) for controlling the flow of refrigerant, - an expansion valve (7), which is arranged downstream of or parallel to the refrigerant pump (6), - an evaporator (8), which is arranged downstream of the expansion valve (7) and the refrigerant pump (6), - a compressor (2), which is arranged downstream of the evaporator (8), - a bypass (15) to the refrigerant pump (6), - a bypass (16) to the compressor (2), wherein the coolant circuit (21) and the refrigerant circuit (20) are coupled via the evaporator (9) as a heat exchanger.

2. Cooling device according to claim 1, characterised in that the sensor is formed by a fill level sensor (19) for the refrigerant upstream of the refrigerant pump (6).

3. Cooling device according to one of the preceding claims, characterised in that the sensor is formed by a sensor (18) at the output of the evaporator (8).

4. Cooling device according to claim 3, characterised in that the sensor is formed by a sensor (13) for controlling the expansion valve (7).

5. Cooling device according to one of the preceding claims, characterised in that the sensor is embodied to control the refrigerant pump (6) or a valve (13, 14) connected in series with the refrigerant pump.

6. Cooling device according to one of the preceding claims, characterised in that the bypass (15) to the refrigerant pump (6) and / or the bypass (16) to the compressor (2) is designed as a refrigerant line with a stop valve (5, 10).

7. Cooling device according to one of the preceding claims, characterised in that the refrigerant pump (6) and / or the compressor (2) has an integrated bypass.

8. Cooling device according to one of the preceding claims, characterised in that the refrigerant pump (6) has a speed control and / or an active throttling and / or an active feedback.

9. Cooling device according to one of the preceding claims, characterised in that a collector (4) is arranged between the condenser (3) and the refrigerant pump (6).

10. Cooling device according to one of the preceding claims, characterised in that the sensor is embodied to control the flow of refrigerant in order to throttle the expansion valve (7) if liquid refrigerant is detected at the evaporator output and / or in the event of a specific overheating state.

11. Cooling device according to one of the preceding claims, characterised in that the cooling device is designed to use R290, R134a or 407c as a refrigerant.

12. Cooling device according to one of the preceding claims, characterised in that a further refrigerant circuit (20a) is connected, wherein its condenser (3a) is arranged in series with the condenser (3) of the first refrigerant circuit (20) on the air side and its evaporator (8, 8a) is arranged in series on the coolant side.

13. Cooling device according to one of claims 1 - 11, characterised in that a further refrigerant loop (20a) is arranged in parallel, wherein the refrigerant loops have a condenser (3) through which both flows of refrigerant pass.

14. Cooling device according to one of the preceding claims, characterised in that an inner heat exchanger (17) is provided, which couples two sections of the refrigerant circuit to one another.

15. Vehicle with a cooling device according to one of the preceding claims.

16. Rail vehicle with a cooling device according to one of claims 1 - 14.

17. Rail vehicle according to claim 16, characterised in that - the condenser (3) and the compressor (2) are higher than the evaporator (8) and the expansion valve (7), wherein in particular the components that are positioned higher are arranged on the roof of the rail vehicle (23) and the components that are positioned lower are arranged below the floor of the vehicle (23).

18. Rail vehicle according to claim 17, characterised in that the higher position of the condenser (3) and the compressor is used to generate the requisite pressure instead of the refrigerant pump and the refrigerant pump (6) is omitted.

19. Method for cooling a vehicle battery, - in which a refrigerant circuit (20) and a coolant circuit (21) coupled thereto are used, wherein the coolant circuit comprises a coolant pump (11) and is in thermal contact with the vehicle battery (12), - in which the refrigerant circuit has the following components: - a condenser (3), - a refrigerant pump (6) which is arranged downstream of the condenser (3), - a sensor (13, 18, 19) for controlling the flow of refrigerant, - an expansion valve (7), which is arranged downstream of or parallel to the refrigerant pump, - an evaporator (8), which is arranged downstream of the expansion valve (7) and the refrigerant pump (6), - a compressor (2) which is arranged downstream of the evaporator (8), - a bypass (15) to the refrigerant pump (6) - a bypass (16) to the compressor (2), wherein the coolant circuit and the refrigerant circuit are coupled via the evaporator (8) as a heat exchanger, in which with a low ambient temperature the refrigerant is guided via the compressor bypass and the refrigerant pump (6) pumps the refrigerant through the refrigerant circuit, wherein the flow of refrigerant is controlled with the aid of the sensor, and with a high ambient temperature the compressor (2) is in operation and the refrigerant is guided via the refrigerant pump bypass.

20. Method according to claim 19, characterised in that a sensor (13, 18) is used at the output of the evaporator in order to control the flow of refrigerant.

21. Method according to one of the preceding claims, characterised in that a fill level sensor (19) upstream of the refrigerant pump is used in order to control the flow of refrigerant.

22. Method according to one of the preceding claims, characterised in that the sensor controls the refrigerant pump (6).

23. Method according to one of the preceding claims, characterised in that the control is carried out such that sufficient refrigerant liquid is present at the input of the refrigerant pump.

24. Method according to one of the preceding claims, characterised in that the control is carried out such that the refrigerant is present at the output of the evaporator (8) in essentially gaseous form or in the event of a predefined overheating state.

25. Method according to one of the preceding claims, characterised in that R290, R134a or 407c is used as a refrigerant.