TECHNICAL FIELD

The present disclosure relates to a control method and control module and particularly, but not exclusively, to a control method and control module for a hybrid energy storage system. Aspects of the invention relate to a method of managing a capacitor module of a vehicle, to a capacitor control module for a vehicle, and to a hybrid energy storage system, to a vehicle and to computer software. BACKGROUND

A hybrid energy storage system (HESS) for a vehicle includes at least two energy storage systems having complimentary energy storage characteristics such as one or more of energy and power density, self-discharge rate etc.

A first energy storage system of the HESS may provide for high power demand at the expense of one or both of a relatively low energy capacity and a high self-discharge rate, whilst a second energy storage system may provide high energy storage with a low self- discharge rate. The first energy storage system may be charged by one or both of a generator, which may be coupled to an engine of the vehicle, and the second energy storage system. The first energy storage system may comprise a capacitor module. The capacitor module may comprise one or more capacitors with a high charge capacity to volume ratio, such capacitors are often referred to as supercapacitors or ultracapacitors. The second energy storage system may comprise a battery formed by a plurality of cells. The capacitor module may provide energy to operate a starter motor to crank the engine for starting. As can be appreciated, the starter motor may have a high power demand to crank the engine.

When the engine is operational, the capacitor module may be charged by the engine via the generator. When the engine is not operational, the capacitor module is charged by the battery. Figure 1 illustrates a period of time during which the engine is not operational and, as illustrated by line 1 10, an output voltage of the capacitor module drops over time, such as over a period of a few hours. In dependence on the engine start command the capacitor module is charged from the battery and the output voltage of the capacitor module gradually rises as illustrated by line 130 at least until a time when an engine cranking voltage is reached following which the starter motor may be energised with sufficient voltage to crank the engine. However a delay time t _D between the time of the engine start command being received and the time the capacitor module being charged to the engine cranking voltage by the battery to an engine cranking voltage at which the starter motor is able to crank the engine is undesirable.

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 method, a control module, a hybrid energy storage system (HESS), a vehicle and computer software as claimed in the appended claims. According to an aspect of the present invention, there is provided a method of managing a capacitor module of a vehicle, comprising determining when an output voltage of the capacitor module is less than or equal to a minimum cranking voltage and charging the capacitor module from a battery module of the vehicle. In an example, the method of managing a capacitor module of a vehicle includes managing at least one supercapacitor and/or ultracapacitor.

According to an aspect of the present invention, there is provided a method of managing a capacitor module of a vehicle, comprising receiving a signal indicative of a likelihood of future engine cranking and charging a capacitor module from a battery module of the vehicle in dependence on the received signal. Advantageously the capacitor module is charged based on the likelihood of the engine being cranked. In an example, the capacitor module comprises at least one super capacitor. According to another aspect of the present invention, there is provided a method of managing a capacitor module of a vehicle, comprising determining when state of charge of the capacitor module is less than a minimum state of charge for engine cranking, charging the capacitor module from a battery module of the vehicle, such that the state of charge of the capacitor module is at least the minimum state of charge for engine cranking, and providing electrical power solely from the capacitor module to a starter motor associated with the engine to crank the engine for starting. In an example, the capacitor module comprises at least one supercapacitor and/or ultracapacitor. Advantageously, even when the engine is non-operational, the capacitor module is maintained at a state of charge capable of cranking the engine.

The determining of the state of charge of the capacitor module may be performed whilst an engine of the vehicle is non-operational. The method may comprise, prior to the determining stopping the running of the engine of the vehicle.

The state of charge of the capacitor module may be determined based on an output voltage of the capacitor module. Advantageously the output voltage of the capacitor module may be conveniently determined.

The charging of the capacitor module may be performed whilst the engine of the vehicle is non-operational. Advantageously the charging of the capacitor module does not require the engine to be operational, thus being available for cranking the engine.

The determining when the state of charge of the capacitor module is less than the minimum state of charge for engine cranking may comprise periodically determining the state of charge of the capacitor module. Optionally the state of charge may be compared with the minimum state of charge. Advantageously the state of charge of the capacitor module is determined at periods during the engine being non-operational.

The periodically determining the state of charge of the capacitor module is performed at intervals of at least 5 minutes, 10 minutes, 15 minutes, 30 minutes or 1 hour. Advantageously, the state of charge of the capacitor module is determined at relatively long intervals of the order of minutes, thus the state of charge may be maintained over relatively long durations, such as hours or days.

The method may comprise determining the minimum state of charge for engine cranking based on one or more of a temperature of the capacitor module, a temperature of the engine, or an ambient temperature. Advantageously environmental conditions are taken into account when determining the state of charge of the capacitor module.

The battery module may be a Li-ion battery module. The capacitor module may comprise at least one supercapacitor or ultracapacitor.

The method optionally comprises determining one or more of a temperature of the capacitor module, a temperature of the engine, or an ambient temperature, and performing the method when the one or more determined temperatures is less than a predetermined temperature. Advantageously the method may be performed, perhaps only performed, when the capacitor module is more likely to self-discharge. Optionally said predetermined temperature is based on a temperature-power delivery relationship for the battery module. According to a further aspect of the present invention, there is provided a capacitor control module for a vehicle, comprising input means for receiving a signal indicative of state of charge of the capacitor module, processing means for determining, whilst an engine of the vehicle is non-operational, when the state of charge of the capacitor module is less than minimum state of charge for engine cranking, output means, operative by the processing means, for providing an output to cause charging of the capacitor module from a battery module of the vehicle, such that the state of charge of the capacitor module is at least the minimum state of charge for engine cranking. In an example, the capacitor module comprises at least one supercapacitor or ultracapacitor. A capacitor control module as described above, wherein the processing means may comprise one or more electronic processors which may operably execute computer-readable instructions stored in a memory.

The processing means may be arranged to periodically compare the state of charge of the capacitor module with the minimum state of charge for engine cranking.

The processing means may be arranged to periodically compare the output voltage of the capacitor at intervals of at least 30 minutes. The processing means may be arranged to determine the minimum state of charge for engine cranking based on one or more of a temperature of the capacitor module, a temperature of the engine, or an ambient temperature.

Optionally the processing means is arranged to provide the output to cause charging of the capacitor module from the battery module of the vehicle whilst the engine of the vehicle is non-operational.

The processing means may be arranged to determine the state of charge of the capacitor module based on an output voltage of the supercapacitor module.

The battery module may be a Li-ion battery module. The capacitor control module may be arranged to determine one or more of a temperature of the capacitor module, a temperature of the engine, or an ambient temperature, wherein the output is provided to cause charging of the capacitor module from the battery module when the one or more determined temperatures is less than a predetermined temperature.

Optionally said predetermined temperature is based on a temperature-power delivery relationship for the battery module.

According to a yet further aspect of the present invention, there is provided a hybrid energy storage system (HESS) for a vehicle, comprising starter means for cranking an engine of the vehicle, capacitor means selectively connectable to the starter means to provide electrical energy for the starter means to crank the engine, capacitor monitoring means for determining state of charge of the capacitor means and providing data indicative thereof, battery means for providing electrical energy for one or more vehicle systems and for selectively charging the capacitor means, control means arranged to receive the data indicative of the state of charge of the capacitor means, wherein the control means is arranged to determine, whilst the engine of the vehicle is non-operational, when the state of charge of the capacitor means is less than minimum state of charge for engine cranking and, in dependence thereon, to control the battery means to provide electrical energy to charge the capacitor means to at least the minimum state of charge for engine cranking.

A HESS as described above, wherein the starter means comprises a starter motor, the capacitor means comprises a capacitor module, the capacitor monitoring means comprises a capacitor monitoring device, the battery means comprises at least one battery, the control means comprises one or more electronic processors which may operably execute computer- readable instructions stored in a memory. The capacitor module may comprise one or more supercapacitors. In an example, the capacitor means comprises at least one supercapacitor and/or ultracapacitor. In an example, the battery comprises at least one Li-ion battery cell. The starter means may be provided with electrical energy for cranking the engine solely by the capacitor means.

The control means may be arranged to periodically compare the data indicative of the output voltage of the capacitor means with the minimum cranking voltage.

The HESS may comprise temperature monitoring means for determining a temperature of one or more of the capacitor module, a temperature of the engine, or an ambient temperature and outputting temperature data indicative thereof. The control means may be arranged to determine the minimum state of charge for engine cranking based on the temperature data. Optionally the control means is arranged to control the battery means to charge the capacitor means whilst the engine of the vehicle is non-operational.

The battery means optionally comprises a Li-ion battery. The HESS may comprise a DC-to-DC convenor for converting a first voltage level associated with the battery means to a second voltage level associated with the capacitor means. The DC-to-DC convenor may comprise at least one DC-to-DC convenor.

According to a still another aspect of the present invention, there is provided a vehicle comprising a control module according to an aspect of the invention, or a HESS according to an aspect of the invention.

In an example, the vehicle comprises an internal combustion engine and the starter means of the vehicle is a starter motor arranged to crank the internal combustion engine. In an example, the starter motor is supplied electrical power solely from a capacitor module comprising at least one supercapacitor and/or ultracapacitor.

According to a still further aspect of the present invention, there is provided computer software which, when executed by a computer, is arranged to perform a method according to an aspect of the invention. The computer software may be stored on a computer- readable medium. Optionally the software is tangibly stored on the computer-readable medium.

According to another aspect of the present invention, there is provided a method of managing a capacitor module of a vehicle, comprising receiving a signal indicative of a likelihood of future engine cranking, charging a capacitor module from a battery module of the vehicle in dependence on the received signal, such that a state of charge of the capacitor module is at least a minimum state of charge for engine cranking, and providing electrical power solely from the capacitor module to a starter means associated with the engine, in dependence on a signal indicative of a requirement for engine cranking, to crank the engine for starting. Advantageously, the capacitor module is charged when cranking of the engine may be required in future. Advantageously a delay before cranking of the engine is possible may be reduced. Advantageously the capacitor module comprises at least one supercapacitor and/or ultracapacitor.

The signal indicative of a likelihood of future engine cranking may be based on a trigger event. Advantageously the trigger event may indicate that cranking of the engine is possible in future.

The trigger event optionally comprises a signal indicative of opening of a vehicle access aperture. Advantageously the opening of the aperture may indicate that cranking of the engine will be required. The vehicle access aperture may be one of a door of the vehicle, boot, a tailgate or a roof of the vehicle.

The trigger event may comprise a signal indicative of unlocking of the vehicle. Advantageously the unlocking of the vehicle may indicate that future cranking of the engine is likely.

The trigger event may comprise on one or more of pre-heating of the vehicle, a schedule means indicative of a vehicle user's schedule, or a vehicle user's location. Advantageously other events may be used to indicate the likelihood of engine cranking.

Optionally the trigger event is not an engine starting command. Advantageously the capacitor module is charged before engine starting is requested.

The method may comprise determining a temperature associated with the battery module, wherein the charging of the capacitor module is performed in dependence on the received signal when said temperature associated with the battery module is equal to or greater than a predetermined temperature. Advantageously the capacitor module may be charged in dependence on the signal when the temperature is equal to or greater than a predetermined temperature.

Optionally, when said temperature associated with the battery module is less than the predetermined temperature, said method comprises determining, whilst an engine of the vehicle is non-operational, when the state of charge of the capacitor module is less than the minimum state of charge for engine cranking. The method may comprise charging the capacitor module from a battery module of the vehicle, such that the state of charge of the capacitor module is at least the minimum state of charge for engine cranking. The method optionally comprises providing electrical power solely from the capacitor module to a starter motor associated with the engine to crank the engine for starting. The charging of the capacitor module may be performed whilst the engine of the vehicle is non-operational. The method may comprise determining the minimum state of charge for engine cranking based on one or more of a temperature of the capacitor module, a temperature of the engine, and an ambient temperature.

The battery module may be a Li-ion battery module.

According to yet another aspect of the present invention, there is provided a capacitor control module for a vehicle, comprising input means for receiving a signal indicative of a likelihood of future engine cranking, processing means for receiving the signal indicative of the likelihood of future engine cranking and controlling an output means to provide an output to cause charging of a capacitor module from a battery module of the vehicle in dependence on the received signal, such that a state of charge of the capacitor module is at least a minimum state of charge for engine cranking.

In an example, the capacitor module comprises at least one supercapacitor and/or ultracapacitor.

The signal indicative of a likelihood of future engine cranking is optionally based on a trigger event. The trigger event may comprise a signal indicative of opening of a vehicle access aperture. Optionally the vehicle access aperture is one of a door of the vehicle, boot, a tailgate or a roof of the vehicle.

The trigger event may comprise a signal indicative of unlocking of the vehicle.

The processing means may be arranged to determine, in dependence on the received signal, whether the state of charge of the capacitor module is less than the minimum state of charge for engine cranking, and to provide the output in dependence thereon. The capacitor control module may comprise input means for receiving a signal indicative of a temperature associated with the battery module, wherein the processing means is arranged to output the signal to cause charging of the capacitor module when said temperature associated with the battery module is equal to or greater than a predetermined temperature.

When said temperature associated with the battery module is less than the predetermined temperature, the processing means may be arranged to determine when state of charge of the capacitor module is less than a minimum state of charge for engine cranking. The processing means may be arranged to provide the output to cause charging of the capacitor module from the battery module, such that the state of charge of the capacitor module is at least the minimum state of charge for engine cranking.

The processing means may be arranged to determine the minimum state of charge for engine cranking based on one or more of a temperature of the capacitor module, a temperature of the engine, or an ambient temperature. The processing means may be arranged to provide the output to cause charging of the capacitor module from the battery module of the vehicle whilst the engine of the vehicle is non-operational.

According to still further aspect of the present invention, there is provided a hybrid energy storage system (HESS) for a vehicle, comprising starter means for cranking an engine of the vehicle, capacitor means selectively connectable to the starter means to provide electrical energy for the starter means to crank the engine, capacitor monitoring means for determining a state of charge of the capacitor module and providing data indicative thereof, battery means for providing electrical energy for one or more vehicle systems and for selectively charging the capacitor module, control means arranged to receive a signal indicative of a likelihood of future engine cranking, wherein the control means is arranged, in dependence on the signal, to control the battery means to provide electrical energy to charge the capacitor means to at least a minimum state of charge for engine cranking. In an example, the capacitor module of the hybrid energy storage system (HESS) comprises at least one supercapacitor and/or ultracapacitor.

The signal indicative of a likelihood of future engine cranking optionally comprises a signal indicative of opening of a vehicle access aperture.

The vehicle access aperture may be one of a door of the vehicle, boot, a tailgate or a roof of the vehicle. The signal indicative of a likelihood of engine cranking optionally comprises a signal indicative of unlocking of the vehicle.

The starter means may be provided with electrical energy for cranking the engine solely by the capacitor means. Optionally the battery means comprises a Li-ion battery.

The HESS may comprise a DC-to-DC convenor for converting a first voltage level associated with the battery means to a second voltage level associated with the supercapacitor means.

According to a still another aspect of the present invention, there is provided a vehicle comprising a control module according to an aspect of the invention, or a HESS according to an aspect of the invention. According to a still further aspect of the present invention, there is provided computer software which, when executed by a computer, is arranged to perform a method according to an aspect of the invention. The computer software may be stored on a computer- readable medium. Optionally the software is tangibly stored on the computer-readable medium.

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

One or more embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 illustrates self-discharging and charging in a prior art hybrid energy storage system.

Figure 2 shows a hybrid energy storage system according to an embodiment of the invention; Figure 3 shows a method according to an embodiment of the invention;

Figure 4 shows an illustration of discharging and charging according to an embodiment of the invention;

Figure 5 shows a method according to another embodiment of the invention; Figure 6 shows a method according to a further embodiment of the invention; and

Figure 7 shows a vehicle comprising a hybrid energy storage system according to an embodiment of the invention.

DETAILED DESCRIPTION

Figure 2 illustrates a capacitor control means, which will be referred to from here as a supercapacitor control means 200 for a vehicle according to an embodiment of the invention. The supercapacitor control means 200 may be implemented as a capacitor control module or supercapacitor control module 200 in some embodiments of the invention. The supercapacitor control module 200 may form part of a hybrid energy storage system (HESS), generally denoted as 220, as illustrated in Figure 2. The HESS 220 may be used in a vehicle. The vehicle may be a land-going vehicle, an aircraft or a watercraft. The vehicle comprises an engine which is cranked for starting, or turned over, by a starter motor 230 electrically coupled to the HESS 220. The engine may be an internal combustion engine such as powered by one of petrol, diesel, propane, biofuel or hydrogen, although other fuels may be envisaged.

The HESS 220 comprises a capacitor means which, in some embodiments, comprises one or more supercapacitors or ultracapacitors and is referred to as a supercapacitor module 240. A supercapacitor is a type of capacitor capable of storing a large amount of electrical energy, typically at least an order of magnitude more energy per unit mass or per unit volume as compared to electrolytic capacitors of comparable charge capacities. A supercapacitor is also known as an ultracapacitor, or a double-layer electrolytic capacitor.

The HESS comprises a generator means 250 which may be an electric generator 250 in some embodiments of the invention. The generator 250 is arranged to generate electrical energy from rotation caused by the engine. The HESS 220 comprises a battery means 270 which in some embodiments of the invention is a battery module 270 which may comprise a plurality of cells. A convenor 260 is provided in some embodiments for converting a voltage of the supercapacitor module 230, which may vary, to a voltage for one or both of powering an electrical load 280 and charging the battery module 270 in an engine running condition. The convenor may be a DC-DC convenor 260 in some embodiments. The battery module 270 is provided for supplying electrical power to one or more electrical loads 280, such as one or more electrical systems 280 of the vehicle. The battery module 270 may be a Li-ion battery module. To start the engine, electrical power is provided solely from the supercapacitor module 240. In other words, the battery module 270 does not provide electrical power directly to the starter 230. Advantageously, since the battery module 270 does not need to deliver high power, this allows battery types, such as for example Li-ion, which do not have a high power delivery capacity, but which are one or more of lightweight and small in size. The control means 200 may be a control device in some embodiments of the invention. The control device 200 comprises input means 212 for receiving a signal indicative of a state of charge of the supercapacitor module 240. In some embodiments the state of charge of the supercapacitor module 240 is determined based on an output voltage of the supercapacitor module 240. The signal may refer to a capacitor voltage or supercapacitor voltage (SV) signal 212. The control device 200 comprises a processing means 210 which may be formed by one or more electronic processors which may operably execute computer- readable instructions stored in a memory (not shown) of the control device 200. The control device 200 further comprises an output means 214, for providing an output to cause charging of the supercapacitor module from a battery module 270. The output means may be an electrical output 214. As illustrated in Figure 2 the output is provided to control a switch means 275 to control charging of the supercapacitor module 240 from the battery module 270. The switching means 275 may be one or more electrical switching devices, such as MOS transistors although it will be realised that other switching devices may be used. The output means 214 is operable by the processing means 210. In some embodiments the control device 200 comprises an input 215 for receiving one or more signals. In some embodiments, such as particularly the embodiment described with reference to Figure 3, the input 215 receives temperature data indicative of at least one temperature, as will be described. In some embodiments, the input 215 is provided for receiving a future engine cranking signal indicative of a likelihood of future engine cranking, as will explained. The input 215 may in some embodiments receive both the temperature data and the future engine cranking signal. All of inputs 212, 214, 215 may be embodied by the control device 200 being connected to a communication bus of a vehicle to receive the respective signals and data.

In use, the control device 200 is able to determine the state of charge of the supercapacitor module 240 based on the output voltage of the supercapacitor module 240 via data received at the input 212 and to control the switching means 275 via the output 214 to cause charging of the supercapacitor module 240 from the battery module 270. Embodiments of the invention aim to at least ameliorate one or more problems associated with ensuring that the supercapacitor module 240 is able to provide sufficient power to the starter motor 230 for engine cranking to start the engine. The control device 200 is arranged to cause charging of the supercapacitor module 240 such that the output voltage of the supercapacitor module 240 is at least a minimum state of charge for engine cranking. In some embodiments the minimum state of charge for engine cranking is such that the output voltage of the supercapacitor module is at least a minimum cranking voltage or is within a cranking voltage range.

In the HESS 220 the supercapacitor module 240 provides sufficiently high power delivery to the starter motor 230 to crank the engine. However, the supercapacitor module 240 must be sufficiently charged to guarantee the cranking performance. When the vehicle is left standing (for example overnight or after a period of parking) the supercapacitor 240 self-discharges. Thus, even if the supercapacitor module 240 was fully charged at the end of the a drive cycle, when the driver returns to the vehicle the supercapacitor module 240 may have discharged, even partly, and cranking performance is not guaranteed. Thus cranking of the engine may be delayed whilst the supercapacitor module 240 is charged.

In one embodiment of the invention, the control device 200, in particular the processing means 210, is arranged to determine when the output voltage of the supercapacitor module 240 is less than or equal to the minimum cranking voltage. Said determination is performed whilst the engine of the vehicle is non-operational i.e. stopped, such that the supercapacitor module 240 is not being charged by the generator 250. The determination may be performed periodically. The periodic determination of the output voltage of the supercapacitor module 240 may be performed at intervals of at least 5, 10, 15, 30 or 60 minutes, although it will be realised that other periods of time may be envisaged. In embodiments of the invention, the processing means 210 is arranged to determine the minimum cranking voltage. As can be appreciated, the voltage required for the starter 230 to crank the engine may not be a predetermined voltage. For example, at low temperatures oil within the engine may be more viscous and starting of the engine may prove more difficult than at higher temperatures. Other factors may also influence the voltage required to be provided to the starter 230 to crank the engine, such as a temperature-dependent efficiency of the supercapacitor module 230. The processing means may determine the minimum cranking voltage based on one or more of a temperature of the supercapacitor module 240, a temperature of the engine, or an ambient temperature i.e. proximal to the vehicle. Data indicative of one or more of these temperatures may be provided to the control device 200 via an input (not shown). The processing means 200 may be provided with a predetermined relationship between cranking voltage and the one or more temperatures, where data indicative of the relationship may be stored in the memory of the control device 200.

Figure 3 illustrates a method 300 of managing a supercapacitor module 140 of a vehicle according to an embodiment of the invention. The method 300 may be implemented by the control device 200 illustrated in Figure 1 in relation to the HESS 220. In some embodiments, the method 300 is performed when a temperature is less than or equal to a predetermined temperature. The temperature may be an ambient temperature or a temperature associated with the battery module 270. Thus the method 300 illustrated in Figure 3 may be a method of ensuring the supercapacitor module 240 is able to support cranking of the engine during cold weather. For example the predetermined temperature may be 5 °C, 3 °C or 0 °C, although it will be realised that other temperatures may be chosen.

The method 300 comprises a step 310 of determining when the engine of the vehicle is turned off or stopped. In other words, the subsequent steps of the method 300 are performed following the engine becoming non-operational. Thus the steps 320-370 are performed whilst the engine of the vehicle is non-operational.

In step 320 the minimum cranking voltage for the starter motor 230 is determined. As discussed above, the minimum cranking voltage may be determined based on one or more of a temperature of the supercapacitor module 240, a temperature of the engine, or an ambient temperature i.e. proximal to the vehicle.

In step 330 it is determined when the output voltage of the supercapacitor module 240 is less than or equal to the minimum cranking voltage. If the output voltage of the supercapacitor module 240 is greater than the minimum cranking voltage, indicative of the starter motor 230 being able to crank the engine when provided with electrical power from the supercapacitor module 240, the method moves to step 340 which introduces a predetermined delay before steps 320-330 are repeated. The delay time may be one of 5, 10, 15, 30 or 60 minutes, although it will be realised that other periods of time may be envisaged. If, however, the output voltage of the supercapacitor module 240 is less than or equal to the minimum cranking voltage, the method moves to step 350. When moving to step 350 it is assumed that should cranking of the engine by the starter motor 230 be required, the supercapacitor module 240 would be unable to provide sufficient voltage without charging from the battery module 270, which would cause an undesirable delay to the starting of the engine. In step 350 the supercapacitor module 240 is charged from the battery module 270, such that the output voltage of the supercapacitor module 240 is within a cranking voltage range. The cranking voltage range may be between the minimum cranking voltage, as determined in step 320, and a supply voltage of the supercapacitor, such as output by the DC-DC convenor 260. In other embodiments, a lower voltage of the cranking voltage range may be higher than the minimum cranking voltage in order to allow for some self-discharging of the supercapacitor module 240 before the minimum cranking voltage is reached.

In step 360 it is determined whether an engine start signal is received. The engine start signal is indicative of a vehicle user's desire to start the engine. The engine start signal may be issued responsive to a user input such as depression of a start button or activation of other control associated with the vehicle. If the engine start signal is received then electrical power is provided solely from the supercapacitor module 240 to the starter motor 230 associated with the engine to crank the engine for starting. If, however, an engine start signal is not received then the method returns to step 320. Step 360 may comprise determining whether the engine start signal is received within a predetermined period of time. The predetermined period of time may be one of 5, 10, 15, 30 or 60 minutes, although it will be realised that other periods of time may be envisaged.

In step 370 the engine is cranked by the starter motor 230. Step 370 may comprise the output voltage of the supercapacitor module 240 being provided to the starter motor 230 to electrically power the starter motor 230. As described above, for cranking the engine the starter motor is solely powered by the supercapacitor module 240. During step 370 the engine may be controlled to start whilst being cranked, as will be appreciated. It will be appreciated from the above that in one embodiment of the invention there is provided an apparatus an method wherein when the output voltage of the supercapacitor module 240 is less than or equal to a minimum cranking voltage, the supercapacitor module 240 is charged from the battery module 270, such that the output voltage of the supercapacitor module 240 is sufficient to crank the engine. In this way, when it is desired to crank the engine the supercapacitor module 240 is more likely to be able to provide sufficient voltage to the starter motor 230 without an appreciable delay.

Figure 4 illustrates a relationship 410 between state of charge (x-axis) and output voltage (y- axis) for the supercapacitor module 240. As can be appreciated, the relationship between state-of-charge (SoC) and output voltage is illustrated as a straight line 410, although it will be appreciated that the relationship may be more complex leading to a non-linear output voltage against SoC. Assuming that the supercapacitor module 240 is fully charged (100% SoC) when the engine is turned off, the supercapacitor module 240 ceases to be continually charged by the generator 250. When not being charged, the supercapacitor module 240 self-discharges as indicated by arrow 420. When self-discharging the output voltage of the supercapacitor module 240 falls as indicated by arrow 420. The output voltage of the supercapacitor module 240 may fall initially from the supply voltage of the generator (V _s ) at 100% SoC. The output voltage of the supercapacitor module 240 may be controlled by the apparatus and method according to one embodiment of the invention, as discussed above, to substantially always be above the minimum cranking voltage V _c corresponding to a SoC indicative in Figure 4 as y. In an iteration of step 330, it is determined that the output voltage of the supercapacitor module 240 is less than or equal to the minimum cranking voltage and thus the supercapacitor module 240 is charged from the battery module 270, thereby causing the output voltage to rise as illustrated by arrow 430 in Figure 4. Whilst it is illustrated that the supercapacitor module 240 is charged to 100% SoC, it will be realised that an upper voltage of the cranking voltage range may be lower than 100% SoC or V _s .

Figure 5 illustrates a method 500 according to another embodiment of the invention. The method 500 may be performed by the supercapacitor control means 200 or control device 200 as illustrated in Figure 2. In some embodiments of the method 500 the supercapacitor module 240 is charged in response to anticipation of future cranking of the engine, as will be explained.

The method 500 comprises a step 510 of determining when the engine of the vehicle is turned off or stopped. In other words, the subsequent steps of the method 500 are performed following the engine becoming non-operational. Thus the steps 520-550 are performed whilst the engine of the vehicle is non-operational. The method 500 may be performed when a temperature is at least a predetermined temperature. The predetermined temperature may be 5 °C, 3 °C or 0 °C, although it will be realised that other temperatures may be chosen. The temperature may be the temperature associated with the battery module 270. In warmer temperatures the battery module 270 may be expected to deliver charge more quickly to the supercapacitor module 240 than in colder temperatures, thus charging of the supercapacitor module 240 may be performed responsive to a future engine cranking signal, as will be explained, without excessive delay.

In step 520 it is determined whether a future engine cranking signal indicative of a likelihood of future engine cranking is received. It will be appreciated that the future engine cranking signal is not issued in response to an engine starting command. That is, the future engine cranking signal is a signal which indicates that engine cranking may shortly be requested.

The signal indicative of a likelihood of future engine cranking is based on a trigger event. The trigger event may be an event preceding starting of the vehicle engine i.e. from which it may be inferred that the engine will be desired to start within a relatively short amount of time i.e. up to five minutes, although other periods of time may be chosen.

The future engine cranking signal may be indicative of opening of a vehicle access aperture. The vehicle access aperture may be one of a door of the vehicle, boot, a tailgate or a roof of the vehicle. The vehicle access aperture may be opened by a user of the vehicle operating a control, such as a button or sensor, or a mechanism such as a door handle associated with the access aperture to cause the access aperture to open.

The future engine cranking signal is indicative of unlocking of the vehicle. The vehicle may be unlocked responsive to a signal wirelessly received from a control device associated with the vehicle, such as a key fob or the like, although it will be realised that the control device may be a computing device such as a smartphone executing control software, such as an app, associated with the vehicle. In other embodiments, unlocking of the vehicle may be performed responsive to successful facial recognition of the user or voice recognition of the user. Other method of confirming the identity of a user are envisaged.

In other embodiments, the future engine cranking signal may be provided based on one or more of pre-heating of the vehicle i.e. in dependence on an instruction being received to preheat the vehicle, a schedule means indicative of a vehicle user's schedule, for example a diary module indicating that the user has an upcoming appointment and may require the vehicle to travel to the appointment or a vehicle user's location. The vehicle user's location may be indicative of the user approaching the vehicle and thus intending to use the vehicle. The charging of the supercapacitor module is performed whilst the engine of the vehicle is non-operational.

The method may comprising determining the minimum cranking voltage based on one or both of a temperature of the supercapacitor module, a temperature of the engine, and an ambient temperature.

In step 520 if the future engine cranking signal is not received, the method loops i.e. waits in step 520 until the future engine cranking signal is received. Once the future engine cranking signal is received, the method 500 moves to step 530.

In step 530 the supercapacitor module 240 is charged from the battery module 270. The supercapacitor module 240 may be charged such that the output voltage of the supercapacitor module 240 is at least a predetermined voltage. The predetermined voltage may substantially be the supply voltage, or the supercapacitor module 240 may be charged until its output voltage is within a cranking voltage range. The cranking voltage range may be between a minimum cranking voltage, which may be determined as described above in conjunction with Figure 3, and a supply voltage of the supercapacitor module 240, such as output by the DC-DC convenor 260.

In step 540 it is determined whether an engine start signal is received. The engine start signal is indicative of a vehicle user's desire to start the engine. The engine start signal may be issued responsive to a user input such as depression of a start button or activation of other control associated with the vehicle. If the engine start signal is received then electrical power is provided solely from the supercapacitor module 240 to the starter motor 230 associated with the engine to crank the engine for starting. If, however, an engine start signal is not received then the method returns to step 520. Step 540 may comprise determining whether the engine start signal is received within a predetermined period of time. The predetermined period of time may be one of 5, 10, 15, 30 or 60 minutes, although it will be realised that other periods of time may be envisaged.

In step 550 the engine is cranked by the starter motor 230. Step 550 may comprise the output voltage of the supercapacitor module 240 being provided to the starter motor 230 to electrically power the starter motor 230. As described above, for cranking the engine the starter motor is solely powered by the supercapacitor module 240. During step 550 the engine may be controlled to start whilst being cranked, as will be appreciated. It will be appreciated from the above that in one embodiment of the invention there is provided an apparatus and method wherein the supercapacitor module 240 is charged in dependence on receipt of the future engine cranking signal. Advantageously the supercapacitor module 240 is not kept in a charged or near-charged state i.e. it is allowed to self-discharge until the future engine cranking signal is received. In response to the future engine cranking signal, the supercapacitor module 240 is charged from the battery module 270 such that sufficient voltage may be provided to the starter motor 230 without significant delay. Figure 6 illustrates a further method 600 according to an embodiment of the invention. The method 600 is a method of selecting a supercapacitor module charging strategy. In step 610 it is determined whether a temperature is greater than a predetermined temperature. The temperature may be an ambient temperature or a temperature associated with the battery module 270. The temperature of the battery module 270 may be indicative of its ability to charge the supercapacitor module 240 within an acceptable period of time in dependence on the battery module's charge transfer capacity at that temperature. The predetermined temperature may be 5 °C, 3 °C or 0 °C, although it will be realised that other temperatures may be chosen. If the temperature is greater than the predetermined temperature in step 610, then the method of managing the supercapacitor module described with reference to Figure 5 is performed. If, however, the temperature is less than or equal to the predetermined temperature the method of managing the supercapacitor module described with reference to Figure 3 is performed.

Figure 7 illustrates a vehicle 700 according to an embodiment of the invention. The vehicle 700 comprises an HESS 120 as illustrated in Figure 1 or is arranged to perform one or both of the methods 300, 500 described with reference to Figures 3 and 5. 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.