Controlling navigation system of a vehicle

Abstract

Aspects of the present invention relate to a control system (100) and method for controlling a navigation system (114) of a vehicle (200). The control system (100) is configured to identify a conditio

Description

TECHNICAL FIELD The present disclosure relates to a controlling a navigation system of a vehicle. Aspects of the invention relate to a control system, a vehicle system comprising such a control system and a navigation system, a vehicle and a method. BACKGROUND It is known to provide a navigation system within a vehicle. Where the vehicle has a plug-in rechargeable traction battery, the navigation system can be configured to identify the location of chargers that the vehicle can use for recharging its battery. It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide a control system, a vehicle system comprising such a control system and a navigation system, a vehicle and a method, as claimed in the appended claims. According to an aspect of the present invention there is provided a control system for controlling a navigation system of a vehicle, the control system comprising one or more processors collectively configured to: identify a condition of a charging circuit of the vehicle, the condition being indicative of: at least a first charging mode being unavailable; and at least a second charging mode being available; and responsive to the identification of the condition: identify at least one charging point that is configured to provide charging that is compatible with the second charging mode; and output a signal indicative of the at least one charging point to the navigation system. This may allow a user (or the vehicle, if autonomous for example) to navigate to a charging point that allows charging despite the condition. The control system comprises one or more controllers collectively comprising at least one electronic processor having an electrical input for receiving an input signal and at least one memory device electrically coupled to the at least one electronic processor and having instructions stored therein. The at least one electronic processor is configured to access the at least one memory device and execute the instructions thereon so as to: identify a condition of a charging circuit of the vehicle, the condition being indicative of: at least a first charging mode being unavailable; and at least a second charging mode being available; and responsive to the identification of the condition: identify at least one charging point that is configured to provide charging that is compatible with the second charging mode; and output a signal indicative of the at least one charging point to the navigation system. The first charging mode may be at least partly defined by a first DC voltage and the second charging mode may at least partly be defined by a second DC voltage, wherein the first DC voltage is different to the second DC voltage. This may allow a user (or the vehicle, if autonomous for example) to navigate to a charging point that allows charging despite the condition. The condition may be a condition associated with a DC-to-DC converter of the charging circuit. The one or more processors may be collectively configured to identify the condition by testing at least one component of the charging circuit. This may optionally allow determination of the condition even when the vehicle is not connected for charging. The at least one component may comprise at least one switch, operation of the at least one switch determining the charging mode, the one or more processors being configured to identify the condition of the charging circuit by identifying incorrect operation of one or more of the switches of the charging circuit. Testing one or more of the switches may comprise: sending a control signal to each of the switches to be tested, the control signal being for opening and / or closing each of the switches being tested; and determining whether a value of a circuit signal, within the charging circuit and associated with the opening and / or closing of each of the switches being tested, is within an predetermined range of values. The control system may be configured to: retrieve information indicative of the condition having previously been identified; test whether the condition persists; and if the condition persists, output the signal indicative of the at least one charging point to the navigation system. According to a further aspect of the present invention there is provided a vehicle system comprising the control system of a preceding aspect, and a navigation system. The navigation system may be configured to, responsive to the signal indicative of the at least one charging point, provide a navigation signal to proceed to a geographical location associated with the at least one charging point for recharging. The navigation signal may cause the vehicle to autonomously or semi-autonomously drive to the geographical location associated with the at least one charging point for recharging. The navigation signal may cause the outputting of a navigation instruction to a user, directing them to drive the vehicle to the geographical location. According to an aspect of the present invention there is provided a control system for controlling a navigation system of a vehicle, the control system comprising one or more processors collectively configured to: identify a condition of a charging circuit of the vehicle, the condition being indicative of at least a first charging mode being unavailable and a second charging mode being available; and responsive to the identification of the condition, output a signal indicative of the first charging mode being unavailable and / or the second charging mode being available, the signal being for informing a user about the condition and / or for use in identifying a charger that is compatible with the second charging mode. According to a further aspect of the present invention there is provided a vehicle comprising the control system of any earlier aspect, or the vehicle system of any earlier aspect. According to a further aspect of the present invention there is provided a method for controlling a navigation system of a vehicle, the vehicle comprising a charging circuit for charging a battery, the method comprising: identifying a condition of the charging circuit, the condition being indicative of: at least a first charging mode being unavailable; and at least a second charging mode being available; and responsive to identifying the condition: identifying at least one charging point that offers charging that is compatible with the second charging mode; and outputting a signal indicative of the at least one charging point to the navigation system. According to a further aspect of the present invention there are provided computer readable instructions that, when executed by a computer, are arranged to perform a method according to a preceding aspect. 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 drawings, in which: Figure 1 shows a vehicle in accordance with an embodiment of the invention; Figure 2 shows a schematic view of the vehicle of Figure 1, including a control system in accordance with an embodiment of the invention; Figures 3 to 8 show an embodiment of a charging circuit and battery of the schematic of Figure 2; Figures 9 to 13 show a further embodiment of a charging circuit and battery of the schematic of Figure 2; Figure 14 shows a method in accordance with an embodiment of the invention; Figure 15 shows a method in accordance with a further embodiment of the invention; Figures 16 to 18 show a charging circuit and battery for use with a further embodiment of the invention; and Figure 19 shows an embodiment of a display of the vehicle of Figures 1 and 2. DETAILED DESCRIPTION A control system 100 and vehicle 200 in accordance with embodiments of the present invention are described herein with reference to the accompanying drawings. As shown in Figures 1 and 2, the control system 100 is installed within a vehicle 200, which comprises a charging circuit 102 that is electrically coupled to a charging port 104 via isolating relays 168, 170, and to a traction battery 106, as described in more detail below. The relays 168, 170 are controlled to selectively couple the charging port 104 to the charging circuit 102 under the control of the control system 100, as described in more detail below. The charging circuit 102 includes a sensing circuit 108 configured to output a condition signal 110 indicative of a condition of the charging circuit 102, the condition being indicative of at least a first charging mode being unavailable and at least a second charging mode being available. Based on the condition signal 110, the control system 100 may identify at least one charging point (not shown) that is configured to provide charging that is compatible with the second charging mode, and to output an output signal 112 indicative of the at least one charging point to a navigation system 114. A GPS unit 148 is coupled to provide location data to the navigation system 114, and the navigation system is coupled to a display 150, as described in more detail below. The control system 100 comprises one controller 124, although it will be appreciated that this is merely illustrative and that two or more controllers 124 can be used in other implementations. The controller 124 comprises processing means 116 and memory means 118. The processing means 116 may be one or more electronic processing device 116 that operably executes computer-readable instructions. The memory means 118 may be one or more memory device 118. The memory means 118 is electrically coupled to the processing means 116. The memory means 118 is configured to store instructions, and the processing means 116 is configured to access the memory means 118 and execute the instructions stored thereon. The controller 124 comprises an input means 120 and an output means 122. The input means 120 may comprise an electrical input 120 of the controller 124. The output means 122 may comprise an electrical output 122 of the controller 124. The input 120 is arranged to receive the condition signal 110 from the sensing circuit 108. The condition signal 110 is an electrical signal that is indicative of the condition of the charging circuit 102, as described above and in more detail below. The output 122 is arranged to output the output signal 112, which is indicative of the at least one charging point. Figure 1 illustrates a vehicle 200 according to an embodiment of the present invention. The vehicle 200 comprises the control system 100, charging circuit 102, and optionally other components as shown in Figure 2. In the implementation of Figures 3 to 8, the battery 106 comprises sub-batteries in the form of a first battery pack 126 and a second battery pack 128. The first battery pack 126 and the second battery pack 128 each contain rechargeable cells (not shown), which are coupled such that the nominal DC voltage of each battery pack is 400 V. It will be appreciated that the first battery pack 126 and the second battery pack 128 need not be packaged separately. It will be appreciated that the first battery pack 126 and the second battery pack 128 need not be packaged separately. In other implementations, the battery packs 126,128 may have nominal voltages that are higher or lower than 400 V. Batteries having a nominal voltage of 400 V may have an actual maximum no-load voltage considerably higher or lower than 400 V. Batteries having a nominal voltage of 400 V may have a maximum no-load voltage of between 200 V and 500 V, for example. Similarly, batteries having a nominal voltage of 800 V may have an actual maximum no-load voltage considerably higher or lower than 800 V. Batteries having a nominal voltage of 800 V may have a maximum no-load voltage of between 400 V and 920 V, for example. The ranges above are examples only, and nominally 400 V and 800 V batteries may have actual maximum no-load voltages outside of those ranges. Similarly, a charging point having a nominal charging voltage of 400 V DC (or 800 V DC) may provide a maximum charging voltage that exceeds 400 V DC (or 800 V DC). Subsequent references to voltage values are all nominal, but for brevity, the word “nominal” will be omitted in the rest of the description. Actual battery voltages will also depend on the state of charge, cell temperature, battery age, and other factors. For simplicity, all voltages will be referred to based on the nominal values of the batteries being described. For example, references to detecting “400 V” or “800 V” are intended to cover detecting a range of possible voltages associated with a nominally 400 V or 800 V battery. In at least some embodiments, the control system can also estimate expected voltages of the battery packs 126,128 based on the current state of charge, which may assist in detecting failures as described in more detail below. The first battery pack 126 has a positive terminal 130 and a negative terminal 132. Similarly, the second battery pack 128 has a positive terminal 134 and a negative terminal 136. The positive terminal 130 of the first battery pack 126 is coupled to a positive terminal 144 of the charging port 104 via the relay 168, and the negative terminal 136 of the second battery pack 128 is coupled to a negative terminal 146 of the charging port 104 via the relay 170. The first battery pack 126 and the second battery pack 128 are also connected to an inverter (not shown) that is used to selectively provide drive current to an electric machine (not shown) to drive the vehicle 200, and to convert electrical power from the electric machine into a DC charging current when the vehicle is in a power regeneration mode. For clarity, the additional connections and circuitry required for this functionality are not shown. The charging circuit 102 includes a first switch 138, a second switch 140, and third switch 142. The first switch 138 is coupled between the negative terminal 132 of the first battery pack 126 and the positive terminal 134 of the second battery pack 128. The second switch 140 is coupled between the negative terminal 132 of the first battery pack 126 and the battery side of the relay 170. The third switch 142 is coupled between the battery side of the relay 168 and the positive terminal 134 of the second battery pack 128. The first switch 138, the second switch 140, and the third switch 142 are individually controllable by way of control signals from the control system 100 (for clarity, connections for the control of the switches are not shown). By controlling the first switch 138, the second switch 140, and the third switch 142, the control system 100 can place the charging circuit 102 into a number of different modes, which will be described with reference to Figures 3 to 8. The charging circuit 102 also controls operation of the relays 168 and 170. The relays 168 and 170 are configured and controlled to operate in a known manner, and so their operation will not be described in detail. For simplicity, they are therefore shown as being open in all Figures. The charging circuit 102 can include components other than those illustrated. For example, the charging circuit 102 can include filtering components, safety components, monitoring components, isolating components, and communication components, all of which are known within the art. Figure 3 shows a non-charging mode, in which the first switch 138, the second switch 140, and the third switch 142 are open. In this mode, there is no circuit through the first battery pack 126 and the second battery pack 128. As such, the charging circuit 102 cannot provide a charge current to charge the first and second battery packs 126 and 128. Typically, this non-charging mode is enabled when the vehicle is not plugged in, or when the vehicle is plugged in but charging is not intended. Figure 4 shows a high-voltage DC charging mode, in which the first switch 138 is closed, and the second switch 140 and the third switch 142 are open. In this mode, there is a series circuit from the relay 168 through the first battery pack 126, the first switch 138, the second battery 128, and back to the relay 170. As such, the first battery pack 126 is in series with the second battery pack 128. The charging circuit 102 therefore “sees” an 800 V battery due to the 400 V voltages of the first battery pack 126 and the second battery pack 128 being summed. Figure 5 shows a low-voltage DC charging mode, in which the first switch 138 is open, and the second switch 140 and the third switch 142 are closed. In this mode, there is a first circuit from the relay 168, through the first battery pack 126, the second switch 140, and back to the relay 170. There is also a second circuit from the relay 168, through the third switch 142, the second battery pack 128, and back to the relay 170. As such, the first battery pack 126 is in parallel with the second battery pack 128. The charging circuit 102 therefore “sees” a 400 V battery. The high-voltage DC charging mode of Figure 4 and the low-voltage DC charging mode of Figure 5 require different DC charging voltages, to match the relatively higher and lower battery voltages seen at the charging circuit 102. The first switch 138, the second switch 140, and the third switch 142 can take the form of physical relays or power switching devices, depending upon the particular implementation. While such switches are typically highly reliable, there is a natural failure rate over time. Such failures can result in a switch being temporarily or permanently stuck in an open or closed state. Should one or more of the switches fail, either temporarily or permanently, it may be impossible to reliably switch between the low-voltage and high-voltage modes described above. A number of examples of switch condition scenarios will now be described with reference to Figures 6 to 8. Testing for the existence of such scenarios can be undertaken at any suitable time, such as periodically, at vehicle start-up, when the vehicle state of charge and / or range falls below a threshold (which is optionally customisable by the end user), or when the vehicle is to be navigated to a charging point. Figure 6 shows a situation in which the control system 100 is initially attempting to control the switches 138,140, and 142 so as to place the charging circuit 102 into the non-charging mode shown in Figure 3. This is done by the control system 100 outputting suitable control signals to each switch. However, the third switch 142 is stuck in the closed position. In the event the third switch 142 is a physical relay, for example, the relay contacts may have welded shut, or the relay may be physically stuck in the closed position. Other stuck-closed modes for relays and other switching devices are known to the skilled person. The sensing circuit 108 can receive a status signal indicative of a response of at least one of the switches to the corresponding control signal. The status signal in this case comprises an indication that there is 400 V between the positive and negative terminals 130 and 136 despite the control system 100 attempting to control all switches 138, 140, 142 to be open. In some implementations, it is possible to determine from a calculated voltage of each battery pack 126,128 whether the second switch 140 or the third switch 142 (or both) is stuck closed, so as to cause the 400 V to be present. Even if both battery packs have identical voltages, this will change once charging commences. Even if it is not possible to determine exactly which switch 140,142 is stuck closed, the fact that the sensed voltage is not 800 V shows that it is not the first switch 138 that is stuck closed. The high-voltage charging mode of Figure 4 is unavailable, because it is unsafe to close the first switch 138 while one or both of the second switch 140 and third switch 142 are (stuck) closed. However, the fact that at least one of the second switch 140 and the third switch 142 is stuck closed means that the low-voltage charging mode of Figure 5 is still available. Accordingly, the sensing circuit 108 outputs the condition signal 110 indicative of a condition of the charging circuit 102, the condition being indicative of: at least a first charging mode (the high-voltage mode, in this case) being unavailable; and at least a second charging mode (the low-voltage mode, in this case) being available. Figure 7 shows a situation in which the control system 100 is attempting to control the switches 138,140, and 142 so as to place the charging circuit 102 into the non-charging mode shown in Figure 3. This is done by the control system 100 outputting suitable control signals to each switch. However, the first switch 138 is stuck in the closed position. The cause of this condition can correspond with the reasons set out above in in relation to the third switch 142 being stuck closed. The sensing circuit 108 can receive a status signal indicative of a response of at least one of the switches to the corresponding control signal. The status signal in this case comprises an indication that there is 800 V between the positive and negative terminals 130 and 136, showing that the first switch 138 is stuck closed. The low-voltage charging mode of Figure 5 is unavailable, because it is unsafe to close the second switch 140 and third switch 142 while the first switch 138 is (stuck) closed. However, the fact that the first switch 138 is stuck closed means that the high-voltage charging mode of Figure 4 is still available. Accordingly, the sensing circuit 108 outputs the condition signal 110 indicative of a condition of the charging circuit 102, the condition being indicative of: at least a first charging mode (the low-voltage mode, in this case) being unavailable; and at least a second charging mode (the high-voltage mode, in this case) being available. Figure 8 shows a situation in which the control system 100 is attempting to control the switches138,140, and 142 so as to place the charging circuit 102 into the high-voltage charging mode shown in Figure 4. This is done by the control system 100 outputting suitable control signals to each switch. However, the first switch 138 is stuck in the open position. In the event the first switch 138 is a physical relay, for example, the relay may be physically stuck in the open closed position. Other open circuit failure modes for relays and other switching devices are known to the skilled person. The sensing circuit 108 receives a status signal indicative of a response of at least one of the switches to the corresponding control signal. The status signal in this case comprises an indication that there is 0 V between the positive and negative terminals 130 and 136. However, the control system 100 is attempting to control the first switch 138 to be closed to place the charging circuit 102 into the high-voltage charging mode of Figure 4, which should result in 800 V being present across the positive and negative terminals 144 and 146. From this, it can be determined that the first switch 138 is stuck open. The high-voltage charging mode of Figure 4 is unavailable, because it is not possible to close the first switch 138. However, the second switch 140 and the third switch 142 are not stuck in this scenario, meaning that the low-voltage charging mode of Figure 5 is still available. Accordingly, the sensing circuit 108 outputs the condition signal 110 indicative of a condition of the charging circuit 102, the condition being indicative of: at least a first charging mode (the high-voltage mode, in this case) being unavailable; and at least a second charging mode (the low-voltage mode, in this case) being available. The skilled person will appreciate that there are other possible combinations of failure types applied to various combinations of the first, second, and third switches 138, 140, 142, each leading to the availability of at least one mode and the unavailability of at least another mode. Responsive to receiving the condition signal 110, the control system 100 is configured to identify at least one charging point that is configured to provide charging in a manner compatible with the second (i.e., available) charging mode. Fer example, where the second charging mode is a low-voltage (i.e., 400 V (input) DC) charging mode, the control system can identify at least one charging point that is configured to provide a suitable charging voltage. Identifying such charging point(s) can be done in any suitable manner. For example, the memory 118 (and / or another memory within the vehicle 200) can store a list or database of charging points, including information about the charging mode compatibility of each charging point, and the charging point’s location. Alternatively, such a list or database can be wholly or partly stored remotely, such as in a cloud-hosted database, and accessed by way of a network such as a wireless telecommunications network. Wherever it is hosted, such a database can be accessed by sending a request including information regarding the second charging mode. A list of one or more compatible charging points can be provided in response to the request. The list can include information such as an address, GPS coordinates, and / or any other location-related information associated with the charging point(s). Alternatively, the request can be for a list of charging points, optionally based on a location of the vehicle, or a location input by the user, for example. The received list of charging points can then be filtered based on the available charging mode(s) indicated by the condition signal 110. The control system 100then outputs the output signal 112 indicative of the at least one charging point to the navigation system 114. The navigation system 114 is configured to, responsive to the output signal 112, provide a navigation signal to proceed to a geographical location associated with the at least one charging point for recharging. The navigation signal can cause the vehicle 200 to autonomously or semi-autonomously drive to the geographical location associated with the at least one charging point for recharging. Alternatively, or in addition, the navigation signal can cause the outputting of a navigation instruction to a user, directing them to drive the vehicle to the geographical location. Such a navigation instructions can include audio, visual, and / or haptic instructions, for example, as are well understood in the field of vehicle navigation. For example, the navigation system 114 can use the car’s current location (using, for example, the GPS unit 148 - see Figure 2) and the output signal 112 to generate instructions for navigating to at least one of the compatible charging point(s). Where more than one compatible charging point is identified, which charging point to navigate to can be selected in any suitable manner. The user can select a charging point from the list by interacting with a user interface such as a touch interface on the display screen, buttons, sliders, dials, and the like. Alternatively, or in addition, the user interface can accept vocal commands (using, for example, a microphone (not shown)) and / or gesture commands (using, for example, a camera (not shown)). For example, compatible charging points can be listed on a display screen associated with the navigation system 114 and / or the control system 100. Figure 19 showsanexampleof such a display screen 150, which is mounted within the vehicle 200. The display screen shows a map 162 that indicates three compatible charging points 1,2, and 3, and the current location 166 of the vehicle 200. The display screen 150 also displays a list 164 of the charging points 1, 2, and 3. The charging points 1, 2, and 3 can be listed with reference to the name (not shown) of the place and / or the supplier of the charging services offered by the charging points. The name can be that of a carpark, service station, or any other location, for example, and can optionally include a full or abbreviated address for each charging point. Additional information for each compatible charging point can be listed to help the driver or occupant decide which charging point to which to navigate. Such information can include, for example, a distance Dn (in miles or kilometres, for example) to the charging point, the cost Xn of using the charging point (cost / kWh, for example), how many charging units Zn are at the charging point, and how many charging unit(s) Yn at the / each charging point are presently occupied. Where an existing navigation journey is already under way, the information can include distance and / or time added to that journey for each of the charging points, for example. The driver or other occupant can manually select their preferred charging point from the list by interacting with the touch sensitive screen, although a selection can also (or alternatively) be made by using vocal commands and / or gestures in other embodiments. Alternatively, the charging point can be selected automatically by the control system 100 or other system within the vehicle 200. Such a selection can be made in any suitable manner, including on the basis of information such as stored user preference, any current journey programmed into the navigation system 114, the current range of the vehicle 200, and other factors that will suggest themselves to the skilled person. The driver or occupant can then navigate the vehicle 200 to a charging point that allows charging despite the identified condition. The driver can follow navigation instructions, and / or, if the vehicle has autonomous capability, the vehicle can drive itself. An alternative approach to sensing a condition of the switches is to individually control the switches and to determine whether a value of a circuit signal, within the charging circuit and associated with the opening and / or closing of each of the switches being tested, is within a predetermined range of values. For example, changes in continuity or voltage across the switches can be measured as they are controlled with “open” and “close” signals. For example, each of switches 138,140,142 can be provided with individual control signals during a test mode, such as a switch-testing mode. Such a mode can be entered at any suitable time, such as periodically, at vehicle start-up, when the vehicle state of charge and / or range falls below a threshold (which is optionally customisable by the end user), or when the vehicle is to be navigated to a charging point. An example sequence of opening and closing the switches 138, 140, 142 for testing will now be described. First, the control system 100 attempts to place the charging circuit 102 into the non-charging mode of Figure 3, in which all switches to be open. The sensing circuit 108 measures the continuity across the first switch 138. If the first switch 138 is closed, this may indicate that the first switch 138 is stuck closed, as it should be open in the non-charging mode if it is functioning correctly. Optionally, the control system 100 can attempt to “unstick” the switch by attempting to toggle it open and closed a number of times. If the first switch 138 remains in the closed state, then it can be concluded that it is stuck closed. If the first switch 138 is open as expected, then the charging circuit 102 attempts to close the first switch 138, and again measures continuity across it. If the continuity suggests that the first switch 138 remains open, this may indicate that the first switch 138 is stuck open. Optionally, the control system 100 can attempt to “unstick” the switch by attempting to toggle it closed and open a number of times. If the first switch 138 remains in the open state, then it can be concluded that it is stuck open. The process described in relation to the first switch 138 is repeated for each of the second and third switches 140,142. Once complete, a full picture of the condition of the switches will be known. If any of the switches is found to not be operating correctly, then a corresponding error message can be communicated to the driver, allowing them to take remedial action, such as booking the car in with a suitable service centre for diagnosis and repair. The condition of each switch, optionally along with results of any attempts to toggle the state of the switches 138,140,142 can optionally be logged for later review. Assuming that a subset of the first, second and third switches 138,140,142 is found to not be operating correctly, the sensing circuit 108 outputs the condition signal 110 indicative of a condition of the charging circuit 102, the condition being indicative of: at least a first charging mode being unavailable; and at least a second charging mode being available. For example, if the first switch 138 is stuck closed, then the high voltage charging mode is available, but the low-voltage charging mode is unavailable. Other combinations of operable and stuck (open or closed) switches will result in different charging modes being available and unavailable. It will be appreciated that there may be certain combinations of switch conditions that will leave no charging mode available. In that case, a corresponding error message can be communicated to the driver, allowing them to take remedial action, such as booking the car in with a suitable service centre for diagnosis and repair. The condition of each switch, optionally along with results of any attempts to toggle the state of the switches 138,140,142 can optionally be logged for later review. Figures 16 to 18 show a further implementation of a charging circuit and battery. The implementation of Figure 16 to 18 shares a number of components with the implementation of Figures 3 to 8, and like components are indicated with like reference signs. The implementation of Figures 16 to 18 uses the first and second battery packs 126, 128, charging of which is controlled by the control system 100 described in relation to Figure 2. The relays 168,167 selectively connect the charging port 104 to the battery packs 126,128, again under the control of the control system 100. A switch 172 selectively connects the positive terminal 130 of the first battery pack 126 to the relay 168. Similarly, a switch 174 selectively connects the negative terminal 136 of the second battery pack 128 to the relay 170. A double-pole, double-throw (DPDT) switch 176 includes a first switch 178 and a second switch 180. The DPDT switch can take the form of, for example, a mechanically screw-driven double-throw dual-pole device. In other embodiments, the first and second switches 178,180 can take the form of separate switches / relays. An advantage of using a DPDT switch is that, depending upon its construction, it is more likely to fail in one of the two stable operating modes described below, whereas individual switches can fail in any combination of open and closed, leading to less-predictable failure modes. The common pole of the first switch 178 is connected to the negative terminal 132 of the first battery pack 126. The other two poles of the first switch 178 are connected respectively to the relay 170 and to one pole of the second switch 180. The first switch 178 is controllable by the control system 100 such that the negative terminal 132 can be selectively connected to the relay 170 or the pole of the second switch 180. The common pole of the second switch 180 is connected to the positive terminal 134 of the second battery pack 128. The other two poles of the second switch 180 are connected respectively to the relay 168 and to one pole of the first switch 178 (as described in the preceding paragraph). The second switch 180 is controllable by the control system 100 such that the positive terminal 134 can selectively be connected to the relay 168 or the pole of the first switch 178. First and second switches 178,180 are controlled together. That is, a single control signal changes the connection state of both of the first and second switches 178,180. The charging circuit comprises the switches 172,174 and 176. The sensing circuit 108 is connected similarly to that in the Figures 3 to 8, to sense a voltage between the positive terminal 130 of the first battery pack 126 (via the switch 172) and the negative terminal 136 of the second battery pack 128 (via the switch 174). In other embodiments, the sensing circuit 108 can also be connected to other points in order to sense one or more voltages and / or currents that enable it to determine whether one or more switches is not operating as intended. In use, the DPDT switch 176 can be controlled to place the battery 106 into a 400 V mode or an 800 V mode. Figure 17 shows the DPDT switch 176 controlled such that the battery 106 is in the 400 V charging mode. The switch 178 connects the negative terminal 132 to the relay 170, and the switch 180 connects the positive terminal 134 to the relay 168. Switches 172 and 174 are closed. Relays 168 and 170 remain open, ready to be closed once charging is ready to commence. In this configuration, the first and second battery packs 126 and 128 are connected in parallel with each other, for parallel charging from an 800 V charger. Figure 18 shows the DPDT switch 176 controlled such that the battery 106 is in the 800 V charging mode. The switch 178 connects the negative terminal 132 to the pole of switch 180, and the switch 180 connects the positive terminal 134 to the corresponding pole of switch 178. Switches 172 and 174 are closed. Relays 168 and 170 remain open, ready to be closed once charging is ready to commence. In this configuration, the first and second battery packs 126 and 128 are connected in series with each other, for series charging from a 400 V charger. In the embodiment of Figures 16 to 18, one or more of the switches 172, 174, and 176 becoming stuck open or closed may disable one charging mode but allow another charging mode. For example, if the switch 172 sticks open, then the 800 V charging mode is not available, because the first and second battery packs 126 and 128 cannot be connected in series. However, it is still possible to charge the second battery pack 128 with a 400 V charger by placing the switch 176 into the state shown in Figures 16 and 17. Similarly, if the switch 174 sticks open, then the 800 V charging mode is not available, because the first and second battery packs 126 and 128 cannot be connected in series. However, it is still possible to charge the first battery pack 126 with a 400 V charger by placing the switch 176 into the state shown in Figures 16 and 17. In either case, the sensing circuit 108 therefore outputs the condition signal 110 indicative of a condition of the charging circuit 102, the condition being indicative of: at least a first charging mode (i.e., the 800 V charging mode) being unavailable; and at least a second charging mode (i.e., the 400 V charging mode) being available. If the DPDT switch 176 becomes stuck in either the Figures Wand 17 state or the Figure 18 state, then only the charging mode associated with that state will be available. If the DPDT switch 176 becomes stuck in the Figure 16 and 17 state, then only the 400 V (parallel) charging mode will be available. The sensing circuit 108 therefore outputs the condition signal 110 indicative of a condition of the charging circuit 102, the condition being indicative of: at least a first charging mode (i.e., the 800 V charging mode) being unavailable; and at least a second charging mode (i.e., the 400 V charging mode) being available. If the DPDT switch 176 becomes stuck in the Figure 18 state, then only the 800 V (series) charging mode will be available. The sensing circuit 108 therefore ou^uts the condition signal 110 indicative of a condition of the charging circuit 102, the condition being indicative of: at least a first charging mode (i.e., the 400 V charging mode) being unavailable; and at least a second charging mode (i.e., the 800 V charging mode) being available. In the embodiment of Figures 16 to 18, the condition of the switches 172, 174, 176 can be determined based on voltages sensed by the sensing circuit 108, in a similar manner as was the case in the embodiment of Figures 3 to 8. An alternative approach to sensing a condition of the switches is to individually control the switches and to determine whether a value of a circuit signal, within the charging circuit and associated with the opening and / or closing of each of the switches being tested, is within an predetermined range of values. For example, changes in continuity or voltage across the switches can be measured as they are controlled to open and close. For example, each of switches 172,174 and 176 can individually be controlled during a switch-testing mode. Such a mode can be entered at any suitable time, such as periodically, at vehicle start-up, when the vehicle state of charge and / or range falls below a threshold (which is optionally customisable by the end user), or when the vehicle is to be navigated to a charging point. The first charging mode may be defined by a first DC voltage and the second charging mode may be defined by a second DC voltage, where the first DC voltage is different to the second DC voltage. In the embodiments described above, the condition relates to the operability of various switches in the charging circuit 102 for a multi battery pack, where the charging voltage of the battery can be altered by using the switches to change the series / parallel configuration of battery packs. In other implementations, instead of reconfiguring the battery pack to account for changes in the available charging voltage of a charging point, the charging circuit 102 includes a DC-DC converter for, if needed, stepping up or down the DC voltage supplied by a charging point, to an appropriate voltage for charging the battery. For example, if the battery is nominally 800 V, then an 800 V charging point can be used directly. However, if only a 400 V charging point is available, then a DC-DC step-up converter is used to step the voltage of the charging point up to the higher voltage necessary to charge the vehicle’s 800 V battery. Figures 9 to 13 show an alternative arrangement comprising a charging circuit 102 and battery pack 126. In this implementation, the battery pack 126 is an 800 V battery pack, but it will be appreciated that different voltages may be employed in other implementations. The charging circuit 102 includes a DC-DC converter 152 configured for converting a first DC voltage to a second, different DC voltage. For example, the DC-DC converter 152 can be configured to step up the voltage supplied by a connected charging point (not shown) to the higher voltage necessary to charge the 800 V battery pack 126. The charging circuit 102 includes a first switch 154 coupled between the relay 168 and the positive terminal 130 of the battery pack 126, and a second switch 156 coupled between the output of the DC-DC converter 152 and the positive terminal 130 of the battery pack 126. A third switch 158 is coupled between the negative terminal 132 of the battery pack 126 and the relay 170. The sensing circuit 108 is connected to sense two voltages: a first voltage between the relay 168 side of the first switch 154 and the negative terminal 132 of the battery pack 126, and a second voltage between the output of the DC-DC converter 152 and the negative terminal 132 of the battery pack 126. The first switch 154, the second switch 156, and the third switch 158 are individually controllable by the control system 100. By controlling the status of the first switch 154, the second switch 156, and the third switch 158, the control system 100 can place the charging circuit 102 into a number of different modes, which will be described with reference to Figures 9 to 11. Figure 9 shows a non-charging mode, in which the first switch 154, the second switch 156, and the third switch 158 are open. In this mode, there is no circuit through the battery pack 126. As such, the charging circuit 102 cannot provide a charge current to charge the battery pack 126. Typically, this non-charging mode is enabled when the vehicle is not plugged in, or when the vehicle is plugged in but charging is not intended. Figure 10 shows an 800 V (input) DC charging mode, in which the first switch 154 and the third switch 158 are closed, and the second switch 156 is open. In this mode, there is a series circuit from the positive terminal of the charging port 104, through the relay 168, the first switch 154, the battery pack 126, the third switch 158, the relay 170, and back to the negative terminal 146 of the charging port 104. Because the voltage supplied via the charging point 104 is suitable for charging an 800 V battery, it can be used directly to charge the battery pack 126 without the need for voltage conversion as was described in relation to Figure 10. Figure 11 shows a 400 V (input) DC charging mode, in which the second switch 156 and the third switch 158 are closed, and the first switch 154 is open. In this mode, there is a series circuit from the positive terminal of the charging port 104, through the relay 168, the DC-DC converter 152, the second switch 156, the battery pack 126, the third switch 158, the relay 170, and back to the negative terminal 146 of the charging port 104. The DC-DC converter 152 steps up the voltage supplied by charging point to the higher voltage necessary to charge the 800 V battery pack 126. As with the first, second, and third switches 138, 140, and 142, the first switch 154, the second switch 156, and the third switch 158 can take the form of physical relays or power switching devices, depending upon the particular implementation. While such switches are typically highly reliable, there is a natural failure rate over time. Such failures can result in a switch being temporarily or permanently stuck in an open or closed state. Should one or more of the switches fail, either temporarily or permanently, it may be impossible to reliably switch between the low-voltage and high-voltage modes described above. Examples of switch condition scenarios will now be described with reference to Figures 12 and 13. Figure 12 shows a situation in which the control system 100 is initially attempting to control the switches 154, 156, and 158 so as to place the charging circuit 102 into the non-charging mode shown in Figure 9. This is done by the control system 100 outputting suitable control signals to each switch. However, the second switch 156 is stuck in the closed position. In the event the second switch 156 is a physical relay, for example, the relay contacts may have welded shut, or the relay may be physically stuck in the closed position. Other closed circuit failure modes for relays and other switching devices are known to the skilled person. The sensing circuit 108 can sense 800 V due to the closed second switch 156 the negative terminal 132 of the battery pack 126 and the side of the second switch 156 opposite to that of the positive terminal 130 of the battery pack 126. As such, it can be determined that the condition of the second switch 156 is closed. The high (input) voltage charging mode of Figure 10 is unavailable, because the lower voltage supplied via the 400 V charging point would be connected simultaneously with the higher voltage supplied via the DC-DC converter 152. However, the closed condition of the second switch 156 means that the low (input) voltage charging mode of Figure 11 is still available. Accordingly, the sensing circuit 108 outputs the condition signal 110 indicative of a condition of the charging circuit 102, the condition being indicative of: at least a first charging mode (the high (input) voltage charging mode, in this case) being unavailable; and at least a second charging mode (the low (input) charging mode, in this case) being available. Figure 13 shows a situation in which the control system 100 is attempting to control the switches 154, 156, and 158 so as to place the charging circuit 102 into the high (input) voltage charging mode shown in Figure 10. This is done by the control system 100 outputting suitable control signals to each switch. However, the first switch 154 is in the open position. In the event the first switch 154 is a physical relay, for example, the relay may be physically stuck in the open position. Other open circuit failure modes for relays and other switching devices are known to the skilled person. The sensing circuit 108 can sense that there is 0 V to the left of the first switch 154. However, the control system 100 is attempting to control the first switch 154 to be closed to place the charging circuit 102 into the high (input) charging mode of Figure 10 which should result in 800 V being present. From this, it can be determined that the first switch 154 is in the open position. The high (input) voltage charging mode of Figure 10 is unavailable, because it is not possible to close the first switch 154. However, the second switch remains operable in this scenario, meaning that the low (input) voltage charging mode of Figure 11 is still available. Accordingly, the sensing circuit 108 outputs the condition signal 110 indicative of a condition of the charging circuit 102, the condition being indicative of: at least a first charging mode (the high (input) voltage charging mode, in this case) being unavailable; and at least a second charging mode (the low (input) voltage charging mode, in this case) being available. The third switch 158 sticking open disables both charging modes, and the third switch 158 sticking closed enables both charging modes. The skilled person will appreciate that there are other possible combinations of sticking first, second, and third switches 154,156, and 158, each leading to the availability of one mode and the unavailability of another mode. Another condition leading to the availability of one mode and the unavailability of another mode will now be described, in which the converter 152 no longer functions correctly. The sensing circuit 108 can determine that the expected voltage at the output of the converter 152 is incorrect. For example, if the converter 152 has failed, the voltage may be 0 V or another unexpected voltage. Alternatively, the sensing circuit 108 can be configured and connected to determine that the converter 152 no longer functions correctly via any other mechanism, including the converter 152 outputting a suitable signal to the sensing circuit 108. If the converter 152 can no longer convert a 400 V input to the 800 V charging voltage, then the low (input) voltage charging mode of Figure 11 is not available. However, it is still possible to charge by connecting to an 800 V charging point. Accordingly, the sensing circuit 108 outputs the condition signal 110 indicative of a condition of the charging circuit 102, the condition being indicative of: at least a first charging mode (the low (input) voltage charging mode, in this case) being unavailable; and at least a second charging mode (the high (input) voltage charging mode, in this case) being available. Responsive to receiving the condition signal 110, the control system 100 is configured to identify at least one charging point that is configured to provide charging in a manner compatible with the second (i.e., available) charging mode, for example as described above. In other implementations, the charging circuit can be configured to operate with both DC and AC charging sources. The charge current from an AC source is converted to the appropriate DC by an AC-DC converter (not shown). DC can be used to charge the battery directly (or, if not at the appropriate voltage, can be converted to the correct voltage with a converter, for example as described above with reference to Figures 10 to 13). If the AC-DC converter becomes incapable of performing conversion to DC, then the AC (input) charging mode is not available. This may be for any number of reasons, such as a circuit malfunction (similar to the DC-DC converter becoming inoperable as described above) or one or more switches not operating correctly (for example, as described above in relation to other implementations). A sensing circuit, such as sensing circuit 108, can sense that the AC charging mode is not available. If DC charging remains available despite the unavailability of AC charging, then the sensing circuit outputs a condition signal indicative of a condition of the charging circuit, the condition being indicative of: at least a first charging mode (the AC charging mode, in this case) being unavailable; and at least a second charging mode (the DC charging mode, in this case) being available. Any condition leading to the condition signal 110 being output by the sensing circuit 108 can be stored for future reference. For example, information indicative of the condition can be stored in the memory 118. The information can, for example, identify the particular component (e.g., switch, or converter) that is not functioning correctly, and optionally specify the nature of the condition (e.g., stuck open, stuck closed, or potential malfunction). Alternatively, or in addition, such information can be stored remotely, such as in a cloud-hosted database, and accessed by way of a network such as a wireless telecommunications network. The results of testing for the conditions described above can be compared with the stored information regarding the outcome of one or more earlier tests. Such a comparison can be performed at any suitable time, such as periodically, at vehicle start-up, when the vehicle state of charge and / or range falls below a threshold (which is optionally customisable by the end user), or when the vehicle is to be navigated to a charging point. By comparing the information with any condition determined by subsequent testing, it may be determined whether the previously condition persists. If the condition persists, the control system 100 can output the signal 110 as described above. Optionally, the control system 100 can output a different message, indicating that the condition previously occurred and persists. One advantage of storing information regarding the outcome of one or more earlier tests is that any adverse outcomes can be retested, and / or the driver reminded of any issues, when the vehicle is re-started, rather than waiting until (for example) charging is required. In another embodiment, the control system is configured, upon identification of the condition, to output a signal indicative of the first charging mode being unavailable and / or the second charging mode being available. The signal can inform a user about the condition, or trigger the outputting of information to the user regarding the condition. For example, a warning message can be displayed on the display and / or output as a vocal message via the vehicle’s entertainment system. The signal can alternatively, or in addition, trigger the sending of a message to a user’s device, such as a mobile phone, tablet, computer, or other device. Alternatively, or in addition, the signal can be used (for example, as described above) to identify a charger or charger type that is compatible with the second charging mode. That information can be relayed to the user as described above, and / or used by the control system to select a suitable charging point. The vehicle 200 can comprise a vehicle system comprising the control system 100 and the navigation system 114, and optionally the charging circuit 10 and any other component shown in Figure 2. Figure 14 illustrates a method 400 according to an embodiment of the invention. The method 400 is a method of controlling a navigation system of a vehicle, such as the vehicle 200. The method 400 can be performed by the control system 100. In particular, the memory 118 may comprise computer-readable instructions that, when executed by the processor 116, perform the method 400 according to an embodiment of the invention. The method 400 comprises identifying 402 a condition of the charging circuit 102. The condition is indicative of: at least a first charging mode being unavailable; and at least a second charging mode being available. The method 400 also comprises, responsive to identifying the condition: identifying 404 at least one charging point that offers charging that is compatible with the second charging mode; and outputting 406 a signal indicative of the at least one charging point to the navigation system. Figure 15 illustrates a method 500 according to a further embodiment of the invention. The method 500 can be performed by the control system 100. In particular, the memory 118 may comprise computer-readable instructions that, when executed by the processor 116, perform the method 500 according to an embodiment of the invention. The method 500 comprises receiving 502 a first status signal indicative of a status of at least one component of a charging circuit. The method 500 also comprises, based at least in part on the first status signal, identifying 504 a first condition of the charging circuit, the first condition being indicative of: at least one charging mode being unavailable; and at least one further charging mode being available. The method 500 comprises outputting 506 a first signal indicative of the first condition. Embodiments have been described using two battery packs configurable between parallel and series arrangements. In other embodiments, three more battery packs can be provided, which are also configurable between two or more parallel and series arrangements. Embodiments have been described that use 400 V and 800 V battery arrangements, whether in a single battery pack, or two or more series or parallel coupled battery packs presenting a 400 V or 800 V battery to the charging circuit. Other high / low voltages may apply in other embodiments. Also, the battery may be configurable between more than two voltage arrangements. Embodiments have been described that accept 400 V and 800 V DC charging sources, optionally including DC-DC conversion to a different DC voltage that is compatible with the battery to be charged. Other supply voltages (AC and / or DC) may apply in other embodiments. Also, the charging circuit may be capable of accepting more than two AC and / or DC voltages. References to signals include an absence of a signal. For example, a relay can have one state (open or closed) when no control voltage is applied to its control terminals, and another when a suitable control voltage is applied. The control signal in such an arrangement includes the presence or absence of the control voltage. Similarly, the condition signal 110 and / or the output signal can represent a value (such as a voltage or number) and the absence of such a value. Where actions are described as being performed by particular circuits or systems (such as the charging circuit 102 or the sensing circuit 108, for example), it will be understood that some or all of those actions can be performed by one or more other circuits or systems. For example, at least some of the functionality of the charging circuit and / or the sensing circuit can be performed by the control system or any other vehicle system. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

1. A control system for controlling a navigation system of a vehicle, the control system comprising one or more processors collectively configured to:identify a condition of a charging circuit of the vehicle, the condition being indicative of:at least a first charging mode being unavailable; andat least a second charging mode being available; andresponsive to the identification of the condition:identify at least one charging point that is configured to provide charging that is compatible with the second charging mode; andoutput a signal indicative of the at least one charging point to the navigation system.

2. The control system of claim 1, wherein the first charging mode is at least partly defined by a first DC voltage and the second charging mode is at least partly defined by a second DC voltage, wherein the first DC voltage is different to the second DC voltage.

3. The control system of claim 1 or 2, wherein the condition is a condition associated with a DC-to-DC converter of the charging circuit.

4. The control system of any preceding claim, the one or more processors being collectively configured to identify the condition by testing at least one component of the charging circuit.

5. The control system of claim 4, wherein the at least one component comprises at least one switch, operation of the at least one switch determining the charging mode, the one or more processors being configured to identify the condition of the charging circuit by identifying incorrect operation of one or more of the switches of the charging circuit.

6. The control system of claim 5, wherein testing one of more of the switches comprises:sending a control signal to each of the switches to be tested, the control signal being for opening and / or closing each of the switches being tested; anddetermining whether a value of a circuit signal, within the charging circuit and associated with the opening and / or closing of each of the switches being tested, is within an predetermined range of values.

7. The control system of any one of the preceding claims, configured to:retrieve information indicative of the condition having previously been identified;test whether the condition persists; andif the condition persists, output the signal indicative of the at least one charging point to the navigation system.

8. A vehicle system comprising the control system of any preceding claim and a navigation system.

9. The vehicle system of claim 8, wherein the navigation system is configured to, responsive to the signal indicative of the at leastone charging point, provide a navigation signal to proceed to a geographical location associated with the at least one charging point for recharging.

10. The vehicle system of claim 9, wherein the navigation signal causes the vehicle to autonomously or semi-autonomously drive to the geographical location associated with the at least one charging point for recharging.

11. The vehicle system of claim 9, wherein the navigation signal causes the outputting of a navigation instruction to a user, directing them to drive the vehicle to the geographical location.

12. A vehicle comprising the control system of any one of claims 1 to 7 or the vehicle system of any one of claims 8 to 11.

513. A method for controlling a navigation system of a vehicle, the vehicle comprising a charging circuit for charging a battery, the method comprising:identifying a condition of the charging circuit, the condition being indicative of:at least a first charging mode being unavailable: and10 at least a second charging mode being available; andresponsive to identifying the condition:identifying at least one charging point that offers charging that is compatible with the second charging mode; and outputting a signal indicative of the at least one charging point to the navigation system.15 14. Computer readable instructions that, when executed by a computer, are arranged to perform a method according to claim 13.18

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