WO2018142168A1

WO2018142168A1 - Range extender control

Info

Publication number: WO2018142168A1
Application number: PCT/GB2018/050335
Authority: WO
Inventors: Asher Bennett; Richard LIDSTONE-SCOTT; David Hampton; Tomasz KUSMIERZ
Original assignee: Tevva Motors Ltd
Current assignee: Tevva Motors Ltd
Priority date: 2017-02-06
Filing date: 2018-02-06
Publication date: 2018-08-09
Anticipated expiration: 2019-08-06
Also published as: GB201706578D0

Abstract

An apparatus is provided for controlling a range extender of an electric vehicle, the apparatus including a controller that determines a value of a battery parameter indicating an amount of charge remaining in a battery of the electric vehicle; determines a distance between the electric vehicle and a charging station; sets a threshold for the battery parameter according to the determined distance; and operates the range extender according to the value of the battery parameter relative to the set threshold.

Description

Range Extender Control

Field

This specification relates to an apparatus and method for controlling a range extender of an electric vehicle, and to an associated computer program.

Background

Electric vehicles take a variety of forms, including pure electric and hybrid forms. Whereas the only source of power in a pure electric vehicle is a battery, a hybrid vehicle uses a secondary power source, e.g. an internal combustion engine, in addition to a battery. Hybrid vehicles include parallel hybrid vehicles, where the secondary power source or battery may each drive the wheels directly, and series hybrid vehicles. The present specification is primarily concerned with the latter. In a series hybrid vehicle the battery is used to drive the wheels while the secondary power source is used to re- charge the battery. The secondary power source is referred to as a range extender of the electric vehicle. A series hybrid electric vehicle can be referred to as a range-extended electric vehicle.

The battery in a series hybrid vehicle can be charged by the range extender and may also be charged by an external power supply. For example, the battery may be charged using an internal combustion engine of the range extender, or by using electric power from a mains power supply. In some cases, therefore, the power supplied by the range extender may be less efficient or more expensive to generate than power supplied by the external power supply.

Summary

According to one aspect of the present specification there is provided an apparatus according to claim 1. According to another aspect of the present specification there is provided a method according to an independent claim.

According to another aspect of the present specification there is provided a computer program according to an independent claim. Further features of the specification are included in the independent and dependent claims.

Any feature in one aspect of the specification may be applied to other aspects of the specification, in any appropriate combination. In particular, method aspects may be applied to apparatus aspects, and vice versa. The specification also provides a computer program and a computer program product comprising software code adapted, when executed on a data processing apparatus, to perform any of the methods described herein, including any or all of their component steps.

The specification also provides a computer program and a computer program product comprising software code which, when executed on a data processing apparatus, comprises any of the apparatus features described herein. The specification also provides a computer program and a computer program product having an operating system which supports a computer program for carrying out any of the methods described herein and/or for embodying any of the apparatus features described herein. The specification also provides a computer readable medium having stored thereon the computer program as aforesaid.

The specification also provides a signal carrying the computer program as aforesaid, and a method of transmitting such a signal.

Furthermore, features implemented in hardware may be implemented in software, and vice versa. Any reference to software and hardware features herein should be construed accordingly. Any apparatus feature as described herein may also be provided as a method feature, and vice versa. As used herein, means plus function features may be expressed alternatively in terms of their corresponding structure, such as a suitably programmed processor and associated memory. It should also be appreciated that particular combinations of the various features described and defined in any aspects of the specification can be implemented and/or supplied and/or used independently.

In this specification the word 'or' can be interpreted in the exclusive or inclusive sense unless stated otherwise. The specification extends to methods and/or apparatus substantially as herein described with reference to the accompanying drawings.

Brief Description of the Drawings

Purely by way of example, the present specification is now described with reference to the accompanying drawings in which:

Figure ι is a schematic diagram of a range-extended electric vehicle;

Figure 2 is a schematic diagram of the range-extender of the electric vehicle shown in Figure l;

Figure 3 is a schematic circuit-diagram of a controller for controlling the operation of the range extender shown in Figure 2;

Figure 4 is a flowchart showing a method of controlling the operation of the range extender shown in Figure 2.

Detailed Description of Embodiments

A range-extended electric vehicle 10 is shown schematically in Figure l. The range- extended electric vehicle 10 comprises a plurality of wheels n, an electric motor 12, a battery pack 13, a charging connection 14 and a range extender 15. The electric vehicle additionally comprises a controller 100.

The electric motor 12 is connected to at least one wheel 11 of the electric vehicle. The electric motor 12 may be directly connected to one or more wheels 11. Alternatively, the electric motor 12 may be indirectly connected to one or more wheels 11 via e.g. a transmission. The electric motor 12 is configured to drive one or more of the wheels 11 to rotate in a first direction or a second direction. The electric motor 12 drives one or more of the wheels 11 to propel the electric vehicle 10 in a forward or backward direction. The electric motor 12 is operated under the control of a driver of the electric vehicle 10. The driver may operate the electric motor 12 via a controller, for example, a processing module or programmable logic for converting an input of the driver into a control signal for the electric motor 12. The controller of the electric motor 12 may be integrated with the controller 100. Alternatively, the controller of the electric motor 12 may be separate from the controller 100. The electric motor 12 is configured to produce movement using electrical power. The battery pack 13 is connected to the electric motor 12 to supply the electric motor 12 with electric power. The electric motor 12 converts electric energy stored in the battery pack 13 to kinetic energy of the electric vehicle 10. The battery pack 13 comprises a plurality of lithium ion battery cells, for example, lithium ferrite phosphate (LFP) cells, or lithium nickel-manganese-cobalt (NMC) cells.

The battery pack 13 is connected to the charging connection 14. The charging connection 14 can be connected with an external power supply to charge the battery pack 13. For example, the charging connection 14 can be connected with a mains power supply e.g. a domestic power outlet or a publicly accessible charging point. The charging connection 14 may be connected to the external power supply through, for example, a charging cable. One or both of the charging connection 14 and the external power supply may comprise a step-down transformer for converting a mains power supply voltage to a voltage level suitable for charging the battery pack 13.

The electric motor 12 can further operate as a generator to charge the battery pack 13 using motion of the electric vehicle 10. Rotation of the one or more wheels 11 to which the electric motor 12 is connected can drive the electric motor 12. Movement of the electric vehicle 10 in a forward or backward direction can rotate the plurality of wheels 11 and drive the electric motor 12. The electric motor 12 can generate electric power when it is driven mechanically. Electric power generated by the electric motor 12 can be supplied to the battery pack 13 to charge the battery pack. Operation of the electric motor 12 in this way converts kinetic energy of the electric vehicle 10 to electric energy stored in the battery pack 13. This is referred to as regenerative braking of the electric vehicle 10.

The range extender 15 is connected to the battery pack 15. The range extender 15 is configured to supply the battery pack 15 with electric power to charge the battery pack 15. The range extender 15 may also be connected to the electric motor 12. The range extender 15 may supply electric power directly to the electric motor 12.

Figure 2 shows a schematic representation of the range extender 15. The range extender 15 comprises an internal combustion engine (ICE) 16, a fuel tank 17 and an electric generator 18. The ICE 16 is configured to drive the electric generator 18 using fuel supplied by the fuel tank 17. The electric generator 18 generates electric power which is supplied to the battery pack 15 and/or the electric motor 12. The ICE 16 of the range extender 15 may be, for example, a petrol or diesel fuelled engine.

The range extender 15 operates under the control of the controller 100. The range extender 15 is activated or deactivated by the controller 100. The range extender 15 may be controlled to operate in one of a plurality of operating modes. An operating mode of the range extender 15 may be a high efficiency mode. In the high efficiency mode, the range extender 15 is operated to maximise the amount of electric power generated for a given volume of fuel consumed. An operating mode of the range extender 15 may be a high power mode. In the high power mode, the range extender 15 is operated to maximise the rate of electric power generation. An operating mode of the range extender 15 may be a low noise mode. In the low noise mode, the range extender 15 is operated to reduce the amount of noise emitted. An operating mode of the range extender 15 may be a discharge mode. In the discharge mode, the range extender 15 is operated to discharge the battery. An operating mode of the range extender 15 may be a charge maintain mode. In the charge maintain mode, the range extender 15 is operated to maintain the state of charge of the battery. An operating mode of the range extender 15 may be a battery charging mode. In the battery charging mode, the range extender 15 is operated to increase the state of charge of the battery.

The controller 100 may control the operating mode of the range extender 15 by controlling an engine speed of the ICE 16. For example, the ICE 16 may be a diesel engine with a 1.6 litre capacity. The ICE 16 may be controlled to operate at i,ooorpm in the low noise mode, i,500rpm in the high efficiency mode and 2,5001pm in the high power mode. The ICE 16 may consume approximately 5 litres per hour in the low noise mode, 10 litres per hour in the high efficiency mode and 24 litres per hour in the high power mode. The range extender 15 may generate approximately 24kW in the low noise mode, 27kW in the high efficiency mode and 3okW in the high power mode. The range extender 15 is operated according to the amount of charge remaining in the battery pack 13. The controller 100 is configured to monitor a parameter of the battery pack 13 associated with an amount of charge remaining in the battery pack 13. For example, the controller 100 may monitor the usable battery capacity, which may be measured in amp-hours. Alternatively, if the voltage produced by the battery pack 13 is dependent on the amount of charge remaining in the battery pack 13, the controller 100 may monitor an output voltage of the battery pack 13. The parameter measured by the controller 100 is compared with a first threshold value. The first threshold value is referred to as an activation threshold. The activation threshold may have a value at, for example, 20% of the total capacity of the battery pack 13. When the measured parameter is above the activation threshold, it indicates that the amount of charge remaining in the battery pack 13 is sufficient. The range extender 13 is not activated by the controller 100 when the measured parameter is above the activation threshold. The electric motor 12 is operated using electric power from the battery pack 13 only.

When the measured parameter falls below the activation threshold, it indicates that the amount of charge remaining in the battery pack 13 is low. The range extender 13 is activated by the controller 100 when the measured parameter falls below the activation threshold. The controller 100 may activate the range extender 15 in the high efficiency mode. When the range extender 15 is active, the battery pack 13 is charged with electric power supplied by the range extender 15.

When the range extender 15 is active, the parameter measured by the controller 100 is compared with a second threshold value. The second threshold value is referred to as a deactivation threshold. The deactivation threshold may be higher than the activation threshold. The deactivation threshold may have a value at, for example, 30% of the total capacity of the battery pack 13. Alternatively, the deactivation threshold may be set at a fixed value above the activation threshold e.g. 10% of the battery capacity above the activation threshold (so 30% for an activation threshold of 20%).

When the measured parameter rises above the deactivation threshold, it indicates that the amount of charge remaining in the battery pack 13 is sufficient. The range extender 13 is deactivated by the controller 100 when the measured parameter rises above the deactivation threshold. The first threshold value and the second threshold value provide a hysteresis effect, to avoid excessive switching of the range extender 15 by the controller 100.

When the electric motor 12 is operated at high speeds, the rate at which the battery pack 13 is drained by the electric motor 12 may be higher than the rate at which the battery pack 13 is charged by the range extender 15 in the high efficiency mode. The parameter measured by the controller 100 may fall while the range extender 15 is operated in the high efficiency mode. The measured parameter may fall to a value lower than the activation threshold. The measured parameter may be compared with a third threshold value. The third threshold value is referred to as a battery depletion threshold. The battery depletion threshold may have a value at, for example, 10% of the total capacity of the battery pack 13. Alternatively, the battery depletion threshold may be set at a fixed value below the activation threshold e.g. 10% of the battery capacity below the activation threshold.

When the measured parameter falls below the battery depletion threshold, it indicates that the amount of charge remaining in the battery pack 13 is very low. The high power mode of the range extender 13 is activated by the controller 100 when the measured parameter falls below the battery depletion threshold. The controller 100 may operate the range extender 15 in the high power mode until the measured parameter rises above the deactivation threshold.

The controller 100 operates the range extender 15 to maintain a target amount of charge in the battery pack 13. In a steady state of operation, the parameter indicating the amount of charge remaining in the battery pack 13 will fluctuate between the first and second threshold values.

The controller 100 is configured to determine a distance between the electric vehicle 10 and a charging station. The charging station is a location where the charging connection 14 can be connected to an external power supply. For example, the charging station may be a driver's home or place of work. The charging station may be a base of operations for e.g. a delivery company or a taxi company operating a plurality of electric vehicles 10. The controller 100 may determine the distance between the electric vehicle 10 and a plurality of charging stations. Alternatively, the controller 100 may determine the closest of the plurality of charging stations and determine the distance between the electric vehicle 10 and the closest charging station.

The controller 100 is configured to set the value of the activation threshold based on the distance between the electric vehicle 10 and the charging station. The controller 100 is configured to reduce the activation threshold as the distance between the electric vehicle 10 and the charging station decreases. Under the operation of the controller 100, the electric vehicle 10 can have a lower amount of charge remaining in the battery 13 when the electric vehicle 10 is driven to the charging station. The controller 100 can reduce the amount of fuel which is consumed by the range extender 15 to charge the battery pack 13 when the electric vehicle 10 is driving to the charging station. A greater proportion of the battery pack 13 can be charged using electric power supplied by the external power supply, which may be cheaper, more efficient and/ or less polluting than electric power supplied by the range extender 15.

The controller 100 may be configured to reduce the activation threshold from a default value when the distance between the electric vehicle 10 and the charging station is below a perimeter distance. The controller 100 may reduce the activation threshold in a linear fashion based on the distance between the electric vehicle 10 and the charging station. For example, the electric vehicle 10 may pass the perimeter distance at a distance of 10km from the charging station. When the distance between the electric vehicle 10 and the charging station is less than 10km, the activation threshold may be reduced by e.g. 1% of the total capacity of the battery pack 13 for each further decrease of lkm. The controller 100 may reduce the activation threshold from a default value of e.g. 20% of the total battery capacity by 1% per kilometre to a lower value of 10% when the electric vehicle reaches the charging station. Alternatively, the controller 100 may reduce the activation threshold based on a logarithmic relationship or an exponential relationship.

The controller 100 is configured to reduce the deactivation threshold and the battery depletion threshold in accordance with the reduction in the activation threshold. The controller 100 may reduce the deactivation threshold and the battery depletion threshold at the same rate as the reduction in the activation threshold. Alternatively, a distinct rate of reduction may be used for each of the activation threshold, deactivation threshold and battery depletion threshold. For example, the deactivation threshold may be reduced at a greater rate, e.g. 1.5% per kilometre, so that the range extender 15 is activated for a shorter period of time as the electric vehicle 10 moves closer to the charging station. The battery depletion threshold may be reduced at a lower rate, e.g. 0.5% per kilometre, to ensure that the battery depletion threshold does not reach zero. Alternatively, the battery depletion threshold may be given a minimum allowable value. Alternatively, the deactivation threshold and the battery depletion threshold may be fixed as a percentage of the activation threshold e.g. 200% and 50% respectively. Figure 3 shows a schematic representation of the controller 100 capable of controlling the range extender 15. The controller 100 comprises a processor arrangement 101. The processor arrangement 101 and other hardware components maybe connected via a system bus (not shown). Each hardware component may be connected to the system bus either directly or via an interface. A battery 104 is arranged to provide power to the controller 100. Alternatively, the controller 100 may be supplied with electric power from the battery pack 13 via, for example, a DC-DC converter.

The processor arrangement 101 controls operation of the other hardware components of the controller 100. The processor arrangement 101 maybe an integrated circuit of any kind. The processor arrangement 101 may for instance be a general purpose processor. It may be a single core device or a multiple core device. The processor arrangement 101 maybe a central processing unit (CPU), a microcontroller unit (MCU, a programmable logic controller (PLC) or a programmed field programmable gate array (FPGA), a RISC processor or programmable hardware with embedded firmware.

Multiple processor arrangements 101 maybe included. The processor arrangement 101 may be termed processing means.

The controller 100 comprises a working or volatile memory 102. The processor arrangement 101 may access the volatile memory 102 in order to process data and may control the storage of data in memory. The volatile memory 102 may be a RAM of any type, for example Static RAM (SRAM), Dynamic RAM (DRAM), or it may be Flash memory. Multiple volatile memories may be included, but are omitted from the Figure.

The controller 100 comprises a non-volatile memory 103. The non-volatile memory 103 stores a set of operation instructions for controlling the normal operation of the processor arrangement 101. The non-volatile memory 103 may be a memory of any kind such as a Read Only Memory (ROM), a Flash memory or a magnetic drive memory. Other non-volatile memories may be included, but are omitted from the Figure. The processor arrangement 101 operates under the control of the operating

instructions. The operating instructions may comprise code (i.e. drivers) relating to the hardware components of the controller 100, as well as code relating to the basic operation of the packaging apparatus. The operating instructions may also cause activation of one or more software modules stored in the non-volatile memory 103. Generally speaking, the processor arrangement 101 executes one or more instructions of the operating instructions, which are stored permanently or semi-permanently in the non-volatile memory 103, using the volatile memory 102 temporarily to store data generated during execution of the operating instructions.

The processor arrangement 101, the volatile memory 102 and the non-volatile memory 103 may be provided as separate integrated circuit chips connected by an off-chip bus, or they maybe provided on a single integrated circuit chip. The processor arrangement 101, the volatile memory 102 and the non-volatile memory 103 may be provided as a microcontroller. The controller 100 comprises a battery sensing module 105. The battery sensing module 105 is connected to the battery pack 13. The battery sensing module 105 is configured to measure a parameter representing the amount of charge remaining in the battery pack 13. The battery sensing module 105 provides a value of the measured parameter to the processor arrangement 101.

The controller 100 comprises a location module 106. The location module 106 is configured to determine a geographic location of the electric vehicle 10. The location module provides the location of the electric vehicle to the processor arrangement 101. The processor arrangement 101 is configured to determine the distance between the electric vehicle 10 and the charging station based on the location of the electric vehicle 10. A location of the charging station maybe stored in the non-volatile memory 103. The processor arrangement 101 may determine the distance between the electric vehicle 10 and the charging station by comparing the location of the electric vehicle 10 to the location of the charging station.

The location module 106 may determine the geographic location of the electric vehicle 10 using, for example, a global navigation satellite system module such as a GPS, Galileo, GLONASS etc. module. Alternatively, the location module 106 may comprise one or more internal or external sensors for measuring motion of the electric vehicle. Sensors may include accelerometers, an electrical or mechanical odometer and sensors to monitor the input of the driver. The location module 106 may calculate the location of the vehicle using odometry, based on an initial location of the electric vehicle 10 and the measured motion of the electric vehicle 10. Alternatively, the location module 106 may be configured to determine the location of the electric vehicle 10 relative to the charging station. The location module 106 may comprise a radio transmitter/receiver configured to detect a radio signal broadcast from the charging station. The location module 106 may determine the distance between the electric vehicle 10 and the charging station based on the strength of the received radio signal. A received radio signal may further include instructions from the charging station relating to e.g. the perimeter distance, the activation threshold and/or the rate of reduction of the activation threshold. Each of a plurality of charging stations may broadcast an individual perimeter distance and/or reduction rate for incoming electric vehicles 10. The controller 100 comprises a data connection 107. The processor arrangement 101 may connect to an external server through the data connection 107. The processor arrangement 101 may receive information or instructions from an external server through the data connection 107. For example, the processor arrangement 101 may receive information relating to the location of one or more charging stations and/or the electric vehicle 10. The processor arrangement 101 may receive information relating to driving conditions e.g. traffic conditions, weather conditions or other route

information. The processor arrangement 101 may receive instructions relating to e.g. the perimeter distance, the activation threshold and/or the rate of reduction of the activation threshold.

With respect to Figure 4, an operation for the controller 100 is shown, according to an embodiment. The operation is carried out by the controller 100 and, in particular, by the processor arrangement 101. Alternatively, the operation ma be carried out by a server in communication with the controller 100 via the data connection 107.

The operation starts at step 4.1.

At step 4.2, the controller 100 determines the distance between the electric vehicle 10 and the charging station. The location module 106 provides the location of the electric vehicle 10 to the processor arrangement 101. The processor arrangement 101 retrieves the location of the charging station from the non-volatile memory 103 and determines a distance between the two locations.

At step 4.3, the processor arrangement 101 determines the activation threshold. If the distance between the electric vehicle 10 and the charging station is greater than a perimeter distance, the processor arrangement 101 sets a default value for the activation threshold. If the distance between the electric vehicle 10 and the charging station is less than a perimeter distance, the processor arrangement 101 reduces the activation threshold based on the distance between the electric vehicle 10 and the charging station. The processor arrangement 101 also sets the deactivation threshold based on the value of the activation threshold.

At step 4.4, the battery sensing module 105 measures a parameter of the battery pack 13 indicating an amount of charge remaining in the battery pack 13. The value of the measured parameter is provided to the processor arrangement 101 by the battery sensing module 105.

At step 4.5, the processor arrangement 101 determines in the range extender 15 is currently active. If the range extender 15 is not currently active, at step 4.6 the processor arrangement 101 determines if the measured parameter is below the activation threshold. If the measured parameter is below the activation threshold, at step 4.7 the processor arrangement 101 activates the range extender 15. Otherwise, the range extender 15 remains inactive and the process ends.

If the range extender 15 is currently active, at step 4.8 the processor arrangement 101 determines if the measured parameter is above the deactivation threshold. If the measured parameter is above the deactivation threshold, at step 4.9 the processor arrangement 101 deactivates the range extender 15. Otherwise, the range extender 15 remains active and the process ends. The process ends at step 4.10.

It will be appreciated that the above described embodiments are purely illustrative and are not limiting on the scope of the claims. Other variations and modifications will be apparent to persons skilled in the art upon reading the present application, and some will now be described.

The electric vehicle may be any form of vehicle including a car, motorbike, van, lorry, bus or any other form of vehicle. The electric vehicle may have any number of wheels from e.g. 2 to 18 wheels. The electric motor may be connected to any number of the wheels from one wheel to all of the wheels. The electric vehicle may have any number of electric motors up to and include one electric motor for each of the wheels on the electric vehicle.

The electric vehicle maybe autonomous or semi-autonomous.

Any form of battery pack may be used. For example, the battery pack may be a plurality of cells or a single cell. The battery pack may be distributed in a plurality of batteries in different locations in the electric vehicle. The battery pack may comprise any chemistry of battery e.g. any form of lithium ion, as described, nickel cadmium or may be a lead acid battery. The battery pack may include one or more capacitors or supercapacitors to stored electrical energy.

The battery pack may be connected to any suitable external power supply. The external power supply may be a renewable energy source such as solar panels or a wind turbine in a fixed location. The external power supply may be a large external battery storage. The battery may be connected to the external power supply using a wireless energy transmission.

The range extender may include any suitable means of power generation e.g. a hydrogen fuel cell engine or any other alternative fuel. The range extender may operate in the low noise operating mode according to the situation of the electric vehicle e.g. the speed or location of the vehicle. Similarly, the controller may activate the high power operating mode of the range extender based on the speed of the vehicle. At high speed, the range extender may supply electric power directly to the electric motor.

It will be understood that the present specification has been described above purely by way of example, and modifications of detail can be made within the scope of the specification. Reference numerals appearing in the claims are by way of illustration only and shall have no limiting effect on the scope of the claims.

Claims

1. An apparatus for controlling a range extender of an electric vehicle, comprising a controller configured to:

determine a value of a battery parameter indicating an amount of charge remaining in a battery of the electric vehicle;

determine a distance between the electric vehicle and a charging station;

set a threshold for the battery parameter according to the determined distance; and

operate the range extender according to the value of the battery parameter relative to the set threshold.

2. The apparatus of claim 1, wherein the controller is configured to set the threshold for the battery parameter based on a preset value, by decreasing the threshold from the preset value as the determined distance is decreased.

3. The apparatus of claim 2, wherein the controller is configured to set the threshold at the preset value if the determined distance is greater than a perimeter distance, and decrease the threshold from the preset value if the determined distance is lower than the perimeter distance.

4. The apparatus of claim 2 or claim 3, wherein the controller is configured to decrease the threshold linearly based on the decreasing distance between the electric vehicle and the charging station.

5. The apparatus of any preceding claim, wherein the threshold is an activation threshold and the controller is configured to activate the range extender if the value of the battery parameter is below the threshold.

6. The apparatus of claim 5, wherein the controller is further configured to set a deactivation threshold at a fixed margin above the activation threshold, and

wherein the controller is configured to deactivate the range extender if the value of the battery parameter rises above the deactivation threshold.

7. The apparatus of claim 5 or claim 6, wherein the controller is further configured to set a battery depletion threshold at a fixed margin below the activation threshold, and

wherein the controller is configured to change an operating mode of the range extender to a high power mode if the value of the battery parameter falls below the battery depletion threshold.

8. A method of controlling a range extender of an electric vehicle, the method comprising:

determining a value of a battery parameter indicating an amount of charge remaining in a battery of the electric vehicle;

determining a distance between the electric vehicle and a charging station; setting a threshold for the battery parameter according to the determined distance; and

operating the range extender according to the value of the battery parameter relative to the set threshold.

9. The method of claim 8, wherein setting the threshold comprises setting the threshold for the battery parameter based on a preset value, by decreasing the threshold from the preset value as the determined distance is decreased.

10. The method of claim 9, wherein setting the threshold comprises setting the threshold at the preset value if the determined distance is greater than a perimeter distance, and decrease the threshold from the preset value if the determined distance is lower than the perimeter distance.

11. The method of claim 9 or claim 10, wherein setting the threshold comprises decreasing the threshold linearly based on the decreasing distance between the electric vehicle and the charging station.

12. The method of any one of claims 8 to 11, wherein the threshold is an activation threshold and operating the range extender comprises activating the range extender if the value of the battery parameter is below the threshold.

13. The method of claim 12, further comprising setting a deactivation threshold at a fixed margin above the activation threshold; l6 wherein operating the range extender comprises deactivating the range extender if the value of the battery parameter rises above the deactivation threshold.

14. The method of claim 12 or claim 13, further comprising setting a battery depletion threshold at a fixed margin below the activation threshold;

wherein operating the range extender comprises changing an operating mode of the range extender to a high power mode if the value of the battery parameter falls below the battery depletion threshold.

15. A computer program configured to, when executed by a processor, execute the method of any one of claims 8 to 14.