GB2541920A

GB2541920A - System and method for cooling an electric vehicle

Info

Publication number: GB2541920A
Application number: GB1515686.2A
Authority: GB
Inventors: Finnegan Michael
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2015-09-04
Filing date: 2015-09-04
Publication date: 2017-03-08
Also published as: GB2544157A; WO2017037252A1; GB201614922D0; GB201515686D0

Abstract

A method and system for cooling system an electrical vehicle (EV, HEV, hybrid) comprises a radiator, 120, for cooling the prime mover, 110, (electric machine, motor). An air moving means, 128, is used to create an air flow, 124, across the radiator to remove heat therefrom. Air having passed the radiator is redirected via an air duct, 150, across the transmission, 102, (drivetrain, gearbox) of the vehicle. The air may be directed to the underside of the transmission. The air moving means be a fan, 134. There may be a control means, 160, for altering the rotation speed of the fan. The control may be based on the output from heat or temperature sensors, 170. The control may be based on route planning (gps, navigation, sat nav) data, whereby, for example if the speed of the vehicle is expected to rise then the fan speed may be lowered.

Description

SYSTEM AND METHOD FOR COOLING AN ELECTRIC VEHICLE

TECHNICAL FIELD

The present disclosure relates to a system and method for cooling an electric vehicle. Aspects of the invention relate to a cooling system for an electric vehicle, a method of controlling a cooling system, and a vehicle including the cooling system.

BACKGROUND

With improvements in electric motor and battery technology, battery powered electric vehicles are becoming a viable alternative to vehicles powered by internal combustion engines. However, a single battery charge range for battery powered electric vehicles is still significantly less than the range of a full tank of fuel used by a vehicle with an internal combustion engine. It is therefore beneficial to allocate as much battery charge as possible for propelling battery powered electric vehicles and limit battery charge required for cooling vehicle components such as the vehicle’s transmission, inverters and electric machine that provides torque to propel the vehicle.

On congested urban roads, or when in a traffic jam, vehicles repeatedly move for a short distance followed by a short period when they are stationary. This repeated short distance movement typically requires an electric vehicle’s electric machine or motor and associated inverters to generate more heat than when the vehicle is travelling at a constant speed. Furthermore, when an electric vehicle is stationary or travelling at low speed, little or no cooling air will naturally flow into the vehicle’s engine bay. This lack of cooling air may lead to overheating of the vehicle’s electric machine, inverters and transmission. More specifically, such overheating may result in undesirable transmission oil temperature increase which may degrade the lubrication qualities of the transmission oil.

It is an object of embodiments of the invention to at least mitigate one or more of the problems of the prior art.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a cooling system, a vehicle, and a method of controlling a cooling system as claimed in the appended claims.

According to an aspect of the invention there is provided a cooling system for an electric vehicle comprising an air duct arranged to direct an air flow that has passed across a radiator to a transmission of the vehicle.

According to another aspect of the invention there is provided a cooling system for an electric vehicle comprising: a radiator for providing cooling to a prime mover of the vehicle; an air moving means for providing air flow across the radiator and removing heat therefrom; and an air duct arranged to direct the air flow that has passed across the radiator to a transmission of the vehicle. This therefore allows cooling of the transmission by re-using the air flow that has passed across the radiator thereby negating the requirements for dedicated cooling means requiring power.

Suitably, the air duct may be arranged to direct the air flow to an underside of the transmission. This advantageously allows the air flow to flow over a large surface area of the transmission.

The air duct may be arranged to direct some or substantially all of the air flow that has passed across the radiator to the transmission. This provides the advantage of utilizing some or all of the air flow to assist in the cooling of the transmission.

The air moving means may include an electric motor with an output shaft coupled to fan blades.

Suitably, the system may include a control means for providing a signal for controlling an output shaft rotation speed of the electric motor. This advantageously provides for reducing battery drain when the cooling system does not need to operate at the electric motor’s maximum speed.

The system may include heat sensor means for providing temperature dependent signals to the control means.

Suitably, the control means is arranged to process the temperature dependent signals and based on at least the temperature dependent signals, provide the signal to control a rotation speed of the output shaft of the electric motor. This also advantageously provides for reducing battery drain when the cooling system does not need to operate at the electric motor’s maximum speed.

The control means can be coupled to a route planning means, for planning a route for the electric vehicle, and wherein the control means is arranged to process received expected average speed data from the route planning means and based on at least both the temperature dependent signals and expected average speed data, provide a signal to control the rotation speed of the output shaft of the electric motor. This therefore allows for reducing battery drain by reducing the electric motor’s speed, or stopping rotation of the electric motor, in anticipation of future increased air flow over the cooling fins resulting from an expected future speed increase of the vehicle.

The control means may be coupled to a battery charge monitoring means for monitoring a charge of a battery of the vehicle and wherein the control means is arranged to process a battery charge status signal from the battery charge monitoring means and based on at least both the temperature dependent signals and battery charge status signal, control the rotation speed of the output shaft of the electric motor. This advantageously allows for improving a vehicle’s range when the battery charge is low because the low charge of the battery can be prioritized to supply power to the electric machine that provides the torque to the transmission.

Suitably, the sensor means may include at least one transmission heat sensor arranged to provide at least one of the temperature dependent signals indicative of a lubricant temperature of the transmission.

The prime mover may be an electric machine which may have a liquid cooled casing that may be coupled to the radiator by a conduit arrangement and the heat sensor means may include at least one electric machine means heat sensor arranged to provide at least one of the temperature dependent signals indicative of a temperature of the liquid cooled casing.

The system may include a liquid cooled inverter heat sink for cooling an inverter arranged to drive the electric machine, wherein the conduit arrangement couples the radiator to the liquid cooled inverter heat sink.

The system may include a liquid cooled inverter heat sink for cooling an inverter, wherein a conduit arrangement couples the radiator to the liquid cooled inverter heat sink, and wherein the heat sensor means includes at least one inverter heat sensor arranged to provide at least one of the temperature dependent signals indicative of a temperature of the liquid cooled inverter heat sink.

According to yet another aspect of the invention there is provided an electric vehicle comprising the cooling system as described above.

According to yet a further aspect of the invention there is provided a method of controlling a cooling system for an electric vehicle, the method comprising: controlling an air moving means to provide air flow across a radiator; supplying a liquid coolant from the radiator to a prime mover of the vehicle to thereby cool the prime mover; and directing, through an air duct, the air flow that has passed across the radiator, to a transmission of the vehicle. This therefore allows cooling of the transmission by reusing the air flow that has passed across the radiator.

Suitably, the directing, through the air duct, may include directing the air flow to an underside of the transmission. This advantageously allows the air flow to flow over a large surface area of the transmission and cools the area of the transmission where the lubricant is stored before it is splash fed into gears of the transmission.

The directing, through the air duct means, may include directing substantially some or all of the air flow that has passed across the radiator to the transmission. This provides the advantage of utilizing some or all of the air flow to assist in the cooling of the transmission.

The supplying may include supplying the liquid coolant to a liquid cooled inverter heat sink for cooling an inverter.

Suitably, the air moving means may include an electric motor with an output shaft coupled to fan blades, and wherein controlling the air moving means may include: receiving temperature dependent signals from heat sensor means of the system; and adjusting, based on at least the temperature dependent signals, a rotation speed of an output shaft of the electric motor. This advantageously provides for reducing battery drain when the cooling system does not need to operate at the electric motor’s maximum speed.

Controlling the air moving means may include receiving expected average speed data; and adjusting, based on at least both the temperature dependent signals and expected average speed data, the rotation speed of an output shaft of the electric motor. This also advantageously provides for reducing battery drain when the cooling system does not need to operate at the electric motor’s maximum speed. Controlling the air moving means may include receiving battery charge status signals indicative of a charge of a battery of the vehicle; and adjusting, based on at least both the temperature dependent signals and battery charge status signals, the rotation speed of an output shaft of the electric motor. This also advantageously provides for reducing battery drain when the cooling system does not need to operate at the electric motor’s maximum speed.

The prime mover may be an electric machine which may have a liquid cooled casing that may be coupled to the radiator by a conduit arrangement and temperature dependent signals may be indicative of a temperature of the liquid cooled casing of the electric machine.

The temperature dependent signals may be indicative of a temperature of a lubricant of the transmission.

The temperature dependent signals may be indicative of a temperature of a liquid cooled inverter heat sink for cooling an inverter arranged to drive the electric machine.

According to an even further aspect of the invention there is provided a cooling system as described above, wherein: the air moving means providing air flow across the radiator comprises an air moving apparatus, the air moving apparatus includes electric motor with an output shaft coupled to an arrangement of fan blades, the control means comprises a controller with an associated memory, the heat sensor means comprises one or more heat sensors for providing temperature dependent signals to the controller, the route planning means comprises a Satellite Navigation module with a Global Positioning Satellite (GPS) antenna for receiving GPS signals to identify the electric vehicle’s current position, and the battery charge monitoring means comprises a battery charge monitor module.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described by way of example only, with reference to the accompanying figures, in which:

Figure 1 illustrates cooling system for an electric according to an embodiment of the invention;

Figure 2 is a schematic block diagram illustrating an electric circuit of the cooling system of Figurel, according to another embodiment of the invention;

Figure 3 is a flow chart illustrating a method of controlling a cooling system for an electric vehicle, according to a further embodiment of the invention;

Figure 4 is a flow chart illustrating a controlling process of the method of Figure 3, according to a further embodiment of the invention; and

Figure 5 shows an electric vehicle comprising a cooling system according to an embodiment of the invention.

DETAILED DESCRIPTION

Figure 1 illustrates a cooling system 100 for an electric vehicle according to an embodiment of the invention. The cooling system 100 as illustrated is located in an engine bay of an electric vehicle. The cooling system 100 includes a radiator 120 for cooling a liquid contained therein. The radiator 120 includes cooling fins 122 that provide heat transfer from a liquid coolant in the radiator 120 to air passing over the cooling fins 122 of the radiator 120 as indicated by air flow arrows 124.

The system 100 includes an air moving means 128, in the form of an air moving apparatus, for providing air flow 124 across the cooling fins 122 of the radiator 120 and thus removing heat from the radiator 120. In the illustrated embodiment, the air moving means 128 comprises an electric motor 130 with an output shaft 132 coupled to an arrangement of fan blades 134. There is also a conduit arrangement 140 coupling the radiator 120 to a liquid cooled casing 112 of a prime mover in the form of an electric machine 110. The radiator 120 therefore provides for cooling the electric machine 110. Furthermore, the electric machine 110 is arranged to provide torque to a transmission 102 of the vehicle and the conduit arrangement 140 includes a radiator outlet conduit 142A, a conduit interconnection chamber 142B and a radiator inlet conduit 142C.

There is also an air duct 150, arranged to direct the air flow 124 that has passed across the radiator 120 to a casing 104 of the transmission 102. The air duct 150 includes a funnel shaped outlet 152 arranged to direct the air flow, illustrated by air flow arrows 154, to an underside of the casing 104 enclosing a differential 106 that forms part of the transmission 102. In this embodiment the air duct 150 is arranged to direct all of the air flow that has passed across the radiator 120 to the casing 104 of the transmission 102. In another embodiment the air duct 150 is arranged to direct some of the air flow that has passed across the radiator 120 to the casing 104 of the transmission 102

The system 100 includes a liquid cooled inverter heat sink 180 for cooling an inverter which is arranged to drive the electric machine 110. The conduit arrangement 140 couples the radiator 120 to the liquid cooled inverter heat sink 180 to thereby provide coolant to the liquid cooled inverter heat sink 180. As will be apparent to a person skilled in the art, the inverter that is cooled by the liquid cooled inverter heat sink 180 provides for the conversion of a direct current supply into an alternating or pulsed current supply to thereby control the torque generated by the electric machine 110.

The system 100 also includes control means, in the form of a controller 160 with an associated memory, for providing a signal to a motor driver 136 for controlling a rotation speed of the output shaft 132 of the electric motor 130. Coupled to inputs of the controller 160 are heat sensor means in the form of one or more heat sensors for providing temperature dependent signals to the controller 160. As illustrated, the heat sensor means may include: (a) transmission heat sensors 170 arranged to provide temperature dependent signals indicative of a lubricant temperature of the casing 104; (b) electric machine heat sensors 172 arranged to provide temperature dependent signals indicative of a temperature of the liquid cooled casing 112; and/or (c) inverter heat sensors 174 arranged to provide temperature dependent signals indicative of a temperature of the liquid cooled inverter heat sink 180.

In Figure 2 there is a schematic block diagram illustrating an electric circuit 200 of the cooling system 100 according to an embodiment of the invention. The circuit 200 includes the transmission heat sensors 170, the electric machine heat sensors 172, and the inverter heat sensors 174 all coupled to inputs of the controller 160. The motor driver 136 has a control input coupled to an output of the controller 160, and an output of the motor driver 136 has a driver output coupled to an input of the electric motor 130. Thus, the motor driver 136 is arranged to control a rotation speed of the output shaft 132 of the electric motor 130 which thereby controls a rotational speed of the fan blades 134. More specifically, the controller 160 is arranged to process the temperature dependent signals and based on at least the temperature dependent signals, provide a signal to the motor driver 136 to control the rotation speed of the output shaft 132 of the electric motor 130. The fan blades 134 may therefore be operated at a higher speed in response to elevated temperatures.

The electric circuit 200 includes a route planning means for planning a route for the electric vehicle, in the form of a navigation module 220. In this embodiment the route planning means is a Satellite Navigation module with a Global Positioning Satellite (GPS) antenna 230 for receiving GPS signals to identify the electric vehicle's current position, e.g. along a planned route. Furthermore, the controller 160 is arranged to process received expected average speed data for the vehicle from the navigation module 220. Based on at least both the temperature dependent signals from the sensors 170, 172, 174, and expected average speed data, the controller 160 provides a signal to control the rotation speed of the output shaft 132 of the electric motor 130. This therefore has the advantage of reducing battery drain by limiting, or temporarily terminating, power to the motor 130 in anticipation of future increased air flow over the cooling fins resulting from an expected future speed increase of the vehicle.

There is also a battery charge monitoring means for monitoring a charge of a battery of the vehicle, in the form of a battery charge monitor module 230. In this embodiment the controller 160 is arranged to process a battery charge status signal from the battery charge monitor module 230. Based on at least the temperature dependent signals from the sensors 170, 172, 174, and battery charge status signals, the controller 160 controls the rotation speed of the output shaft 132 of the electric motor 130. This advantageously allows for improving a vehicle’s range when the battery charge is low because the low charge of the battery can be prioritized to supply power to the electric machine that provides the torque to the transmission. In this embodiment, the rotation speed of the output shaft 132 can also be additionally dependent on the expected average speed of the vehicle from the navigation module 220.

In Figure 3 there is a flow chart illustrating a method 300 of controlling a cooling system for an electric vehicle according to an embodiment of the invention. The method 300 will be described, for the purpose of illustration only, with reference to the cooling system 100. The method 300 includes a controlling block 310 that performs a process of controlling a speed of the air moving means 128, specifically the electric motor 130, to provide air flow 124 across the radiator 120. At a supplying block 320, a supplying process provides for supplying, through the conduit arrangement 140, a liquid coolant from the radiator 120 to the liquid cooled casing 112 of the electric machine 110. Thus, the supplying of the liquid coolant is to the prime mover of the vehicle which the supplied liquid coolant cools the prime mover. In this embodiment the supplying also includes supplying, through the conduit arrangement 140, the liquid coolant to the liquid cooled inverter heat sink 180.

The method 300, at a directing block 330, performs a directing, through the air duct 150, of the air flow that has passed across the cooling fins 122 to the casing 104 of the transmission 102. In this embodiment the directing, through the air duct 150, directs the air flow to an underside casing of the transmission 102 and typically some or all of the air flow that has passed across the cooling fins 122 of the radiator 120 is directed to the casing of the transmission 102. The method 300 may continually repeat the processes of blocks 310 to 330 whilst power is supplied to the controller 160 as will be understood by a person skilled in the art.

In Figure 4 there is shown a flow chart illustrating the controlling process of block 310, according to a further embodiment of the invention. At a block 410 temperature dependent signals are received from the transmission heat sensors 170, electric machine heat sensors 172, and inverter heat sensors 174. At an optional block 420 expected average speed data is received from the navigation module 220, and at an optional block 430 battery charge status signals indicative of a charge of a battery of the vehicle are received from the battery charge monitor 230. A controlling block 440 comprises the process of adjusting the rotation speed of the output shaft 132 of the electric motor 130. In this embodiment the adjusting is dependent upon: a) the temperature dependent signals; b) the temperature dependent signals and expected average speed data; c) the temperature dependent signals and battery charge status signals; or d) the temperature dependent signals, expected average speed data and battery charge status signals.

In one embodiment the process of adjusting includes the use of a look-up table by the controller 160. The look-up table is essentially a database with look-up fields of ranges for the temperature dependent signals, ranges for the battery charge status signals, and conditions (or numerical values) for the expected average speed data. Thus by searching the database the controller 160 determines the optimal rotation speed of an output shaft 132 of the electric motor 130 and therefore sends an appropriate control signal, indicative of the optimal rotation speed, to the motor driver 136. In response to the control signal, the motor driver 136 provides an appropriate output voltage to control the speed rotation speed of the output shaft 132 of the electric motor 130. For example, if the temperature dependent signals all indicate zero degrees Celsius or below, then the optimal rotation speed of an output shaft 132 may be zero regardless of the expected average speed data and battery charge status signals, since no additional cooling may be required.

As another example, if the temperature dependent signals all indicate 50 degrees Celsius or above and the battery charge status signals indicate a full charge then then additional cooling may be required. As such, the optimal rotation speed of an output shaft 132 may be the maximum speed of the motor 130 if the expected average speed data indicated that the vehicle will be traveling at a constant speed no greater than 3 kilometres per hour for the next ten minutes. However, if the expected average speed data indicated that the vehicle will be traveling at a constant speed between than 4 and 8 kilometres per hour for the next ten minutes, slightly less cooling may be required and the optimal rotation speed of an output shaft 132 may be 95% of the maximum speed of the motor 130. Furthermore, continuing this example, if the expected average speed data indicated that the vehicle will be traveling at a constant speed between than 9 and 12 kilometres per hour for the next ten minutes, the optimal rotation speed of an output shaft 132 may be 75% of the maximum speed of the motor 130.

Referring to Figure 5 there is illustrated an electric vehicle 500 that may include a cooling system according to an embodiment of the invention.

It will be appreciated that embodiments of the present invention can be realised in the form of hardware, software or a combination of hardware and software. Any such software may be stored in the form of volatile or non-volatile storage such as, for example, a storage device like a ROM, whether erasable or rewritable or not, or in the form of memory such as, for example, RAM, memory chips, device or integrated circuits or on an optically or magnetically readable medium such as, for example, a CD, DVD, magnetic disk or magnetic tape. It will be appreciated that the storage devices and storage media are embodiments of machine-readable storage that are suitable for storing a program or programs that, when executed, implement embodiments of the present invention. Accordingly, embodiments provide a program comprising code for implementing a system or method as claimed in any preceding claim and a machine readable storage storing such a program. Still further, embodiments of the present invention may be conveyed electronically via any medium such as a communication signal carried over a wired or wireless connection and embodiments suitably encompass the same.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. The claims should not be construed to cover merely the foregoing embodiments, but also any embodiments which fall within the scope of the claims.

Claims

1. A cooling system for an electric vehicle comprising: a radiator for providing cooling to a prime mover of the vehicle; an air moving means for providing air flow across the radiator and removing heat therefrom; and an air duct arranged to direct the air flow that has passed across the radiator to a transmission of the vehicle.

2. The system as claimed in any preceding claim wherein the air duct is arranged to direct the air flow to an underside of the transmission.

3. The system as claimed in any preceding claim wherein the air duct is arranged to direct some or substantially all of the air flow that has passed across the radiator to the transmission.

4. The system as claimed in any preceding claim wherein the air moving means includes an electric motor with an output shaft coupled to fan blades.

5. The system as claimed in claim 4 including a control means for providing a signal for controlling an output shaft rotation speed of the electric motor.

6. The system as claimed in claim 5 including heat sensor means for providing temperature dependent signals to the control means.

7. The system as claimed in claim 6 wherein the control means is arranged to process the temperature dependent signals and based on at least the temperature dependent signals, provide the signal to control a rotation speed of the output shaft of the electric motor.

8. The system as claimed in claim 7 wherein the control means is coupled to a route planning means, for planning a route for the electric vehicle, and wherein the control means is arranged to process received expected average speed data from the route planning means and based on at least both the temperature dependent signals and expected average speed data, provide a signal to control the rotation speed of the output shaft of the electric motor.

9. The system as claimed in claim 7 or claim 8 wherein the control means is coupled to a battery charge monitoring means for monitoring a charge of a battery of the vehicle and wherein the control means is arranged to process a battery charge status signal from the battery charge monitoring means and based on at least both the temperature dependent signals and battery charge status signal, control the rotation speed of the output shaft of the electric motor.

10. The system as claimed in any one of claims 6 to 9 wherein the heat sensor means includes at least one transmission heat sensor arranged to provide at least one of the temperature dependent signals indicative of a lubricant temperature of the transmission.

11. The system as claimed in any one of claims 6 to 10 wherein the prime mover is an electric machine.

12. The system as claimed in claim 11 wherein the electric machine includes a liquid cooled casing coupled to the radiator by a conduit arrangement and the heat sensor means includes at least one electric machine heat sensor arranged to provide at least one of the temperature dependent signals indicative of a temperature of the liquid cooled casing.

13. The system as claimed in claim 12 including a liquid cooled inverter heat sink for cooling an inverter arranged to drive the electric machine, wherein the conduit arrangement couples the radiator to the liquid cooled inverter heat sink.

14. The system as claimed in any one of claims 7 to 12 including a liquid cooled inverter heat sink for cooling an inverter, wherein a conduit arrangement couples the radiator to the liquid cooled heat sink , and wherein the heat sensor means includes at least one inverter heat sensor arranged to provide at least one of the temperature dependent signals indicative of a temperature of the liquid cooled inverter heat sink.

15. An electric vehicle comprising the cooling system of any preceding claim.

16. A method of controlling a cooling system for an electric vehicle, the method comprising: controlling an air moving means to provide air flow across a radiator; supplying a liquid coolant from the radiator to a prime mover of the vehicle to thereby cool the prime mover; and directing, through an air duct, the air flow that has passed across the radiator, to a transmission of the vehicle.

17. The method as claimed in claim 16 wherein the directing, through the air duct, includes directing the air flow to an underside of the transmission.

18. The method as claimed in claim 16 or claim 17 wherein the directing, through the air duct means, comprises by directing substantially some or all of the air flow that has passed across the radiator to the transmission.

19. The method of claims 16 to 18, wherein the supplying includes supplying the liquid coolant to a liquid cooled inverter heat sink for cooling an inverter.

20. The method as claimed in any one of claims 16 to 19 wherein the air moving means includes an electric motor with an output shaft coupled to fan blades, and wherein the controlling the air moving means includes: receiving temperature dependent signals from heat sensor means of the system; and adjusting, based on at least the temperature dependent signals, a rotation speed of an output shaft of the electric motor.

21. The method as claimed in claim 20, wherein the controlling the air moving means includes: receiving expected average speed data of the vehicle; and adjusting, based on at least both the temperature dependent signals and expected average data, the rotation speed of an output shaft of the electric motor.

22. The method as claimed in claim 20 or claim 21, wherein the controlling the air moving means includes: receiving battery charge status signals indicative of a charge of a battery of the vehicle; and adjusting, based on at least both the temperature dependent signals and battery charge status signals, the rotation speed of an output shaft of the electric motor.

23. The method of claims 20 to 22, wherein the prime mover is an electric machine.

24. The method of claims 23, wherein electric machine includes a liquid cooled casing coupled to the radiator by a conduit arrangement and the temperature dependent signals are indicative of a temperature of the liquid cooled casing of the electric machine.

25. The method of claims 20 to 24, wherein the temperature dependent signals are indicative of a lubricant temperature of the transmission.

26. The method of claims 24 to 25, wherein the temperature dependent signals are indicative of a temperature of a liquid cooled inverter heat sink for cooling an inverter arranged to drive the electric machine.

27. A cooling system for an electric vehicle substantially as hereinbefore described with reference to the drawings.

28. An electric vehicle substantially as hereinbefore described with reference to the drawings.

29. A method of controlling a cooling system vehicle substantially as hereinbefore described with reference to the drawings.