Traction battery system

Abstract

A traction battery system (114) for a vehicle (100) comprises a battery (116) comprising a plurality of voltaic cells and a first side (124) at which a voltaic cell of the battery (116) can emit infrared electromagnetic radiation. A thermal measurement apparatus (118) in also provided for measuring a temperature in respect of the first side (124) and detecting overheating of the voltaic cells. The apparatus also comprises an infrared reflector (122) substantially overlying the first side (124) in spaced relation thereto, the infrared reflector (122) and the first side (124) cooperating to provide a cavity waveguide (120). An infrared electromagnetic radiation measurement sensor apparatus is also provided comprising an infrared electromagnetic radiation sensor device (128) having a field of view that is directed into a space between the infrared reflector (122) and the first side (124) of the battery (116).

Description

TRACTION BATTERY SYSTEM

[0001] The present invention relates to a traction battery system for a vehicle of the type that, for example, comprises a battery comprising a plurality of voltaic cells.

[0002] In the field of electrically-driven or partially electrically-driven vehicles that employ a traction system comprising a battery pack and an electric motor to provide traction for the vehicle, it is known for thermal requirements of the battery to be fairly constrained, owing to a mixture of optimum performance and safety requirements. As such, in addition to typical thermal management practices to ensure optimum performance of the voltaic cells of the battery pack, it is also necessary to monitor the temperature of the battery in order to detect one or more voltaic cells that may be overheating, which can possibly lead to so-called “thermal runaway” conditions and / or complete failure of the battery. Early detection of such occurrences is therefore beneficial not only to prevent potential hazard conditions but also to minimise any damage to the battery.

[0003] During normal operation of the battery pack, the temperature of a voltaic cell within the battery pack may be up to about 20 to about 60 degrees Celsius, but if the temperature raises over about 70 degrees Celsius, this can be an indication of malfunction that can lead to the thermal runaway within the battery mentioned above, particularly if overheating spreads to other voltaic cells in the battery pack. Owing to the normal operation temperature of the battery pack being relatively close to the temperature that needs to be detected, an approach to measurement that relies upon the detection of the average temperature inside the battery pack is unlikely to detect unexpected thermal events until thermal instability has already spread to several voltaic cells of the battery pack. Therefore, several solutions have been proposed to detect such a temperature increase with greater precision.

[0004] For example, it is known to place one or more thermal sensor on top of a battery pack of a vehicle drive system in order to monitor battery performance, for example as described in US patent no. US 9,651 ,428 and German patent publication no. DE 102012024454 A1. These solutions are direct measurement systems, i.e. infrared electromagnetic radiation emissions propagate directly to thethermal sensors employed. As such, it is necessary either to provide a sufficient number of thermal sensors to monitor the entire battery pack, or the distance from thermal sensors to the top of the battery pack to increase. Both these design options therefore attract an increased bill of materials and / or result in the overall size of the battery pack increasing, which is undesirable where manufacturing costs and / or space constraints are important considerations.

[0005] In order to avoid such design difficulties, US patent no. 7,939,192 and US patent publication no. 2022 / 144094 A1 propose siting the thermal sensors to the side of the battery pack. In US patent no. 7,939,192, another example of a direct measurement system, multiple thermal sensors are arranged at a side of the battery pack. In order to facilitate infrared electromagnetic radiation reaching the sensors, the voltaic cells can have a reflective outer layer. Particularly for voltaic cells more deeply located within the battery pack, infrared electromagnetic radiation emitted by these voltaic cells relies upon reflection of the infrared electromagnetic radiation off surfaces of other voltaic cells between the emitting voltaic cell and the sensor measuring the emitted infrared electromagnetic radiation. Consequently, in US patent no. 7,939,192, the provision of thermal sensors to the side of the battery pack also does not enable individual problematic voltaic cells to be identified and the use of multiple thermal sensors elevates the bill of materials of the battery measurement system. In US patent publication no. 2022 / 144094 A1 , an example of an indirect measuring system, a top cover of the battery pack lies parallel with the surface of the cells and provides an uniform clearance over the top side of the cells. A matrix thermal sensor is disposed to a side of the battery pack and points towards an inner surface of the top cover to receive infrared electromagnetic radiation emitted from one or more voltaic cell of the battery pack after reflection off the internal surface of the top cover. However, in order to identify a problematic voltaic cell amongst voltaic cells of the battery pack at temperatures within normal operating parameters, very high quality optical lenses are employed to image each voltaic cell of the battery pack individually to a pixel of the matrix thermal sensor. To implement such an arrangement is both extremely difficult and expensive. As such, the cost of manufacture of such a solution is high.

[0006] US patent publication no. 2023 / 261274 A1 relates to another example of an indirect measurement system, where a battery monitoring system is provided that comprises an inclined reflector arranged opposite a surface of a battery pack for reflecting infrared electromagnetic radiation towards a sensor placed away from the surface. The system typically employs multiple reflectors and sensors to monitor more than one surface of the battery pack. The battery monitoring system therefore lacks complete coverage of all voltaic cells of the battery pack without the use of multiple thermal sensors. The battery monitoring system also employs mapping optics to correct distortions of mapping of emission locations on the surface of the battery pack to the sensor. Owing to the limited space available in a battery, such mapping optics are impractical to implement. For this reason, and also the generally high cost of mapping optics, such a mapping optics based solution is uneconomic to implement.

[0007] It is also noted that the battery monitoring systems described above measure infrared electromagnetic radiation, but these measurements contain background noise from detection of normal operating temperatures from some voltaic cells, which are considered ambient in this context.

[0008] According to a first aspect of the present invention, there is provided a traction battery system for a vehicle, the system comprising: a battery comprising a plurality of voltaic cells and having a first side at which a voltaic cell of the battery can emit infrared electromagnetic radiation; a thermal measurement apparatus for measuring a temperature in respect of the first side of the battery and detecting overheating of the voltaic cell, the apparatus comprising: an infrared reflector substantially overlying the first side of the battery in spaced relation thereto, the infrared reflector and the first side of the battery cooperating to provide a cavity waveguide; and an infrared electromagnetic radiation measurement sensor apparatus comprising an infrared electromagnetic radiation sensor device having a field of view; wherein the field of view of the infrared electromagnetic radiation measurement sensor apparatus is directed into a space between the infrared reflector and the first side of the battery.

[0009] Each of the plurality of voltaic cells may emit the infrared electromagnetic radiation from the first side of the battery unobstructed by any other voltaic cells of the plurality of voltaic cells.

[0010] The infrared reflector may substantially overly the plurality of voltaic cells.

[0011] The infrared reflector may extend away from the first side of the battery.

[0012] The cavity waveguide may be configured to direct, when in use, infrared electromagnetic radiation towards the infrared electromagnetic radiation sensor device.

[0013] The infrared electromagnetic radiation sensor device may have a plane of reception and the plane of reception may be oriented so as to be crossed, when in use, by a propagation path of the infrared electromagnetic radiation.

[0014] The infrared electromagnetic radiation measurement sensor apparatus may comprise an array of sensing pixels.

[0015] The infrared electromagnetic radiation measurement sensor apparatus may comprise an array of sensing pixels for measuring a spatial temperature profile across the first side of the battery caused, when in use, by the plurality of voltaic cells.

[0016] The system may further comprise: an infrared electromagnetic radiation measurement circuit configured to analyse the spatial temperature profile across the first side of the battery and to identify a location of an overheated voltaic cell of the plurality of voltaic cells.

[0017] The infrared electromagnetic radiation measurement sensor apparatus may comprise a single sensing pixel.

[0018] The infrared electromagnetic radiation measurement sensor apparatus may further comprise a low-pass filter disposed between the infrared reflector and an infrared sensing element of the infrared electromagnetic radiation sensor device.

[0019] The low-pass optical filter may be disposed against a reception window of the infrared electromagnetic radiation sensor device. The low-pass optical filter may be transmissive to electromagnetic radiation corresponding to a predetermined temperature range.

[0020] The low-pass optical filter may be integrally formed with the infrared electromagnetic radiation sensor device. The low-pass optical filter may be spatially separated from the infrared electromagnetic radiation sensor device.

[0021] The infrared reflector may be, at least in part, in the field of view of the infrared electromagnetic radiation sensor device.

[0022] The first side of the battery may also be, at least in part, in the field of view of the infrared electromagnetic radiation sensor device.

[0023] A first edge of the infrared reflector at a second side of the battery may be closer to the battery than a second edge of infrared reflector at a third side of the battery; the first edge of the infrared reflector may be opposite the second edge of the infrared reflector.

[0024] The first edge of the infrared reflector may meet the first side of the battery.

[0025] The infrared reflector may be shaped.

[0026] The infrared reflector may be curved.

[0027] The infrared reflector may comprise a fold.

[0028] The fold may create a ridge in the infrared reflector.

[0029] The ridge may extend diagonally with respect to the first side of the battery.

[0030] The fold may create a valley in the infrared reflector.

[0031] The infrared reflector may comprise an overhang return portion that extends towards a level of the first side of the battery.

[0032] The overhang return portion may be cowl-like.

[0033] The infrared reflector may comprise a main portion contiguous with the overhang return portion; the overhang return portion may subtend an obtuse angle with the main portion.

[0034] The infrared electromagnetic radiation sensor device may be disposed at the third side of the battery.

[0035] The infrared electromagnetic radiation measurement sensor apparatus may comprise another infrared electromagnetic radiation sensor device; and the another infrared electromagnetic radiation sensor device may be disposed at the second side of the battery and may have a field of view directed into the space between the first side of the battery and the infrared reflector.

[0036] The infrared electromagnetic radiation measurement sensor apparatus may comprise another infrared electromagnetic radiation sensor device; and the battery may be elongate and may comprise a first end longitudinally separated and distal from a second end; the infrared electromagnetic radiation sensor device may be disposed at the first end; and the another infrared electromagnetic radiation sensor device may be disposed at the second end of the battery and may have a field of view directed into the space between the first side of the battery and the infrared reflector.

[0037] The infrared electromagnetic radiation sensor device may be disposed at a first corner of the first side of the battery.

[0038] The battery may comprise a first group of interconnected voltaic cells electrically coupled to a second group of interconnected voltaic cells; a space may be provided between the first and second groups of voltaic cells; and the infrared electromagnetic radiation sensor device may be disposed in the space between the first and second groups of voltaic cells.

[0039] The infrared electromagnetic radiation sensor device may have a reception window substantially level with the first side of the battery.

[0040] The infrared electromagnetic radiation sensor device may be disposed beneath the overhang return portion; the infrared electromagnetic radiation sensordevice may comprise a plane of reception; the plane of reception may be substantially parallel with the first side of the battery; and the infrared electromagnetic radiation sensor device may be disposed to a side of the battery adjacent a peripheral boundary wall of the battery.

[0041] According to a second aspect of the present invention, there is provided a traction battery system for a vehicle, the system comprising: a battery comprising a plurality of voltaic cells and having a first side at which each a voltaic cell of the battery can emit infrared electromagnetic radiation; a thermal measurement apparatus for measuring a temperature in respect of the first side of the battery and detecting overheating of the voltaic cell, the apparatus comprising: an infrared reflector substantially overlying the first side of the battery in spaced relation thereto, the infrared reflector extending away from the first side of the battery; and an infrared electromagnetic radiation measurement sensor apparatus comprising an infrared electromagnetic radiation sensor device having a field of view; wherein the infrared reflector comprises a first reflector part and a second reflector part, the first and second reflector parts being non-parallel and non-coplanar and respectively cooperating with the first side of the battery to provide one or more cavity waveguides; and the field of view of the infrared electromagnetic radiation measurement sensor apparatus is directed into the one or more cavity waveguides.

[0042] Each of the plurality of voltaic cells may emit the infrared electromagnetic radiation form the first side of the battery unobstructed by any other voltaic cells of the plurality of voltaic cells.

[0043] The infrared reflector may substantially overlie the plurality of voltaic cells.

[0044] The first reflector part may be contiguous with the second reflector part.

[0045] The infrared reflector may comprise a ridge line; the ridge line may extend away from the first side of the battery.

[0046] The ridge line may extend diagonally with respect to the first side of the battery.

[0047] The ridge line may be a hip.

[0048] The plurality of voltaic cells of the battery may comprise a periphery adjacent the first surface of the battery; the periphery may comprise a first side adjacent a second side; the first reflector part may extend away from the first side of the battery and towards the second reflector part from the first side of the periphery; and the second reflector part may extend away from the first side of the battery and towards the first reflector part from the second side of the periphery.

[0049] The first and second reflector parts may cooperate to form a valley or valley-like shape therebetween; the first reflector part may extend towards the second reflector part.

[0050] The infrared electromagnetic radiation sensor device may be disposed on the first side of the battery and substantially centrally with respect to a periphery of the battery.

[0051] The plurality of voltaic cells of the battery may comprise a periphery adjacent the first side of the battery; the periphery may comprise a first side opposite a second side; the first reflector part may extend from first side of the periphery towards the second side of the periphery; and the second reflector part may extend from the second side of the periphery towards the first side of the periphery.

[0052] The first and second reflector part may extend toward the first side of the battery from the first and second sides of the periphery, respectively, and may meet to form the valley.

[0053] The plurality of voltaic cells of the battery may comprise a periphery adjacent the first side of the battery; the periphery may comprise a first side opposite a second side; the first reflector part may extend away from the first side of the periphery and the first side of the battery in a first direction; the second reflector part may extend away from the second side of the periphery and the first side of the battery in a second direction; and the first and second directions may be opposite directions.

[0054] The first reflector part may be closest to the first side of the battery at the second side of the periphery; and the second reflector part may be closest to the first side of the battery at the first side of the periphery.

[0055] The first and second reflector parts may be respectively trapezoidal in shape.

[0056] The infrared reflector may further comprise: a third reflector part; a fourth reflector part; and the third reflector part may be contiguous with the second reflector part and the fourth reflector part may be contiguous with the first and third reflector parts.

[0057] The plurality of voltaic cells of the battery may comprise a periphery adjacent the first side of the battery; the first, second, third and fourth reflector parts may extend away from the first side of the battery and towards each other; the first, second, third and fourth reflector parts may each have a first edge closest to the first side of the battery; and the first edge of each of the first, second, third and fourth reflector parts may be closest to the periphery.

[0058] The first, second, third and fourth reflector parts may be triangular in shape.

[0059] The first and third reflector parts may be the same size and the second and fourth reflector parts may be the same size.

[0060] The first, second, third and fourth reflector parts and the first side of the battery together may form a pentahedral structure.

[0061] The first, second, third and fourth reflector parts may converge towards an apex point.

[0062] The system may further comprise an aperture at the apex point.

[0063] The one or more cavity waveguides may be oriented to direct, when in use, infrared electromagnetic radiation towards the infrared electromagnetic radiation sensor device.

[0064] The infrared electromagnetic radiation sensor device may have a plane of reception and the plane of reception may be oriented so as to be crossed, when in use, by a propagation path of the infrared electromagnetic radiation.

[0065] The infrared electromagnetic radiation measurement sensor apparatus may comprise an array of sensing pixels for measuring a spatial temperature profile across the first side of the battery caused, when in use, by the plurality of voltaic cells.

[0066] The system may further comprise: an infrared electromagnetic radiation measurement circuit configured to analyse the spatial temperature profile across the first side of the battery and to identify a location of an overheated voltaic cell of the plurality of voltaic cells.

[0067] The infrared electromagnetic radiation measurement sensor apparatus may comprise a single sensing pixel.

[0068] The infrared electromagnetic radiation measurement sensor apparatus may further comprise a low-pass optical filter disposed between the infrared reflector and an infrared sensing element of the infrared electromagnetic radiation sensor device.

[0069] The low-pass optical filter may be disposed against a reception window of the infrared electromagnetic radiation sensor device. The low-pass optical filter may be transmissive to electromagnetic radiation corresponding to a predetermined temperature range.

[0070] The low-pass optical filter may be integrally formed with the infrared electromagnetic radiation sensor device. The low-pass optical filter may be spatially separated from the infrared electromagnetic radiation sensor device.

[0071] The infrared reflector may be, at least in part, in the field of view of the infrared electromagnetic radiation sensor device.

[0072] The first side of the battery may also be, at least in part, in the field of view of the infrared electromagnetic radiation sensor device.

[0073] The infrared electromagnetic radiation measurement sensor device may be disposed at a first corner of the first side of the battery.

[0074] The infrared electromagnetic radiation measurement sensor apparatus may comprise another infrared electromagnetic radiation sensor device; and the infrared electromagnetic radiation sensor device may be disposed at the first side of the periphery and the field of view thereof may be directed into a first space between the first reflector part and the first side of the battery; and the another infrared electromagnetic radiation sensor device may be disposed at the second side of the periphery and may have a field of view directed into a second space between the second reflector part and the first side of the battery.

[0075] The space between the one or more cavity waveguides may comprise the first space and the second space.

[0076] The electromagnetic radiation measurement sensor apparatus may comprise another infrared electromagnetic radiation sensor device; and the infrared electromagnetic radiation sensor device may be disposed at a first corner of the first side of the battery; and the another electromagnetic radiation sensor device may be disposed at a second corner of the first side of the battery; the second corner may be diagonally opposite the first corner.

[0077] The infrared electromagnetic radiation sensor device may be disposed in the aperture at the apex point facing towards the first side of the battery.

[0078] The infrared electromagnetic radiation sensor device may be disposed at a level of the first side of the battery and directed towards the apex point.

[0079] The battery may comprise a first group of interconnected voltaic cells electrically coupled to a second group of interconnected voltaic cells; a space may be provided between the first and second groups of voltaic cells; and the infrared electromagnetic radiation sensor device may be disposed in the space between the first and second groups of voltaic cells.

[0080] The infrared electromagnetic radiation sensor device may have a reception window substantially level with the first side of the battery.

[0081] The infrared reflector may comprise an overhang return portion that extends towards a level of the first side of the battery.

[0082] The overhang return portion may serve as a cowl.

[0083] The first reflector part may comprise an overhang return portion that extends towards a level of the first side of the battery.

[0084] The infrared electromagnetic radiation sensor device may be disposed beneath the overhang return portion; the infrared electromagnetic radiation sensor device may comprise a plane of reception; the plane of reception may be substantially parallel with the first side of the battery; and the infrared electromagnetic radiation sensor device may be disposed to a side of the battery adjacent a periphery of the plurality of voltaic cells.

[0085] According to a third aspect of the present invention, there is provided a traction battery system for a vehicle, the system comprising: a battery comprising a plurality of voltaic cells and having a first side from which each of the plurality of voltaic cells can emit infrared electromagnetic radiation unobstructed by any of the other voltaic cells of the plurality of voltaic cells; a thermal measurement apparatus for measuring a spatial temperature profile across the first side of the battery caused, when in use, by the plurality of voltaic cells, the apparatus comprising: an infrared reflector substantially overlying the battery in spaced relation thereto, the infrared reflector and the first side of the battery cooperating to provide a cavity waveguide; an infrared electromagnetic radiation measurement sensor apparatus comprising an infrared electromagnetic radiation sensor device having a field of view and a reception window; and the infrared electromagnetic radiation measurement sensor apparatus further comprises a low-pass optical filter disposed between the planar cavity waveguide and an infrared sensing element of the infrared electromagnetic radiation sensor device; wherein the field of view of the infrared electromagnetic radiation measurement sensor apparatus is directed into a space between the infrared reflector and the first side of the battery.

[0086] The infrared electromagnetic radiation sensor device may comprise an array of sensing pixels.

[0087] The infrared electromagnetic radiation sensor device may comprise a single sensing pixel.

[0088] It is thus possible to provide a battery measurement system that is capable of identifying individual voltaic cells in a battery that are overheating. In this regard, the system can employ fewer thermal sensors than known battery measurement systems. The detection of thermal runaway events can also be detected faster than by other known techniques and systems. The battery measurement system also preserves compactness of the battery as much as possible, and enables a centralised monitoring of the complete battery using one or a small number of sensors, which is a considerably smaller number than the number of voltaic cells being monitored. By removing the influence of ambient temperatures from correctly operating voltaic cells, the battery measurement system is able to identify regions of elevated temperature with reduced errors. For example, an on / off type trigger can be implemented that reacts only to overheating, thereby eliminating the need for complex calculations. This facilitates the more precise identification of an overheating cell and / or region of the battery.

[0089] At least one embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0090] Figure 1 is a schematic perspective diagram of an electrically or part- electrically driven vehicle comprising a traction battery system constituting an embodiment of the invention;

[0091] Figure 2 is a schematic diagram of a battery monitoring system of the battery traction system of Figure 1 ;

[0092] Figure 3 is a schematic perspective diagram of a cavity waveguide and an infrared electromagnetic radiation sensor device of the battery monitoring system of Figure 2;

[0093] Figure 4 is a schematic diagram of geometries associated with reflections of infrared electromagnetic radiation emitted by an overheating cell into the cavity waveguide of Figure 3;

[0094] Figure 5 is a schematic side view of the cavity waveguide and the infrared electromagnetic radiation sensor device of Figure 3 comprising the infrared electromagnetic radiation sensor device mounted to have a first orientation and constituting an embodiment of the invention;

[0095] Figure 6 is a schematic side view of the cavity waveguide and the infrared electromagnetic radiation sensor device of Figure 3 comprising the infrared electromagnetic radiation sensor device mounted to have a second orientation and constituting another embodiment of the invention;

[0096] Figure 7 is a schematic side view of a variation to the cavity waveguide and the infrared electromagnetic radiation sensor device of Figure 3 comprising the infrared electromagnetic radiation sensor device mounted to have a third orientation and constituting a further embodiment of the invention;

[0097] Figure 8 is a schematic side view of another variation to the cavity waveguide and the infrared electromagnetic radiation sensor device of Figure 3 comprising the infrared electromagnetic radiation sensor device mounted to have the third orientation and constituting yet another embodiment of the invention;

[0098] Figure 9 is a schematic perspective diagram of another cavity waveguide and the infrared electromagnetic radiation sensor device of the battery monitoring system of Figure 2 constituting a further embodiment of the invention;

[0099] Figure 10 is a schematic perspective diagram of a multi-part cavity waveguide and the infrared electromagnetic radiation sensor device of the battery monitoring system of Figure 2 constituting yet a further embodiment of the invention;

[0100] Figure 11 is a schematic perspective diagram of another multi-part cavity waveguide and the infrared electromagnetic radiation sensor device of the battery monitoring system of Figure 2 constituting yet another embodiment of the invention;

[0101] Figure 12 is a schematic perspective diagram of yet another multi-part cavity waveguide and the infrared electromagnetic radiation sensor device of thebattery monitoring system of Figure 2 constituting yet another embodiment of the invention;

[0102] Figure 13 is a schematic side view of a further multi-part cavity waveguide and the infrared electromagnetic radiation sensor device of the battery monitoring system of Figure 2 constituting an embodiment of the invention;

[0103] Figure 14 is a schematic perspective diagram of a polyhedral-type cavity waveguide and the infrared electromagnetic radiation sensor device of the battery monitoring system of Figure 2 constituting another embodiment of the invention;

[0104] Figure 15 is a schematic perspective diagram of the polyhedral-type cavity waveguide of Figure 14 employing an alternative siting of the infrared electromagnetic radiation sensor device and constituting a further embodiment of the invention; and

[0105] Figures 16 to 18 are schematic side views of a centrally mounted infrared electromagnetic radiation sensor device between two groups of voltaic cells employing different alternative cavity waveguides and constituting respective further embodiments of the invention.

[0106] Throughout the following description, identical reference numerals will be used to identify like parts.

[0107] Referring to Figure 1 , a vehicle 100 driven by electricity, for example a fully electric vehicle, or part-driven by electricity, for example a hybrid electric vehicle, comprises a body 101 , front wheels 102 operably coupled to a front wheel drive system 104 by front half shafts 106, rear wheels 108 operably coupled to a rear wheel drive system 110 by rear half shafts 112. The vehicle 100 also comprises a traction battery system 114 comprising a battery 116 operably coupled to the front and rear wheel drive systems 104, 110, and thermal measurement apparatus 118. The battery 116 comprises a plurality of voltaic cells. The plurality of voltaic cells can be organised in any number of different ways. For example, the plurality of voltaic cells can be stored in a single housing, or the plurality of voltaic cells can be respectively housed in smaller groups of electrically interconnected voltaic cells,the groups of voltaic cells nevertheless being electrically coupled together to form the battery 116. In some examples, the battery 116 can be configured to provide a space, for example a recess, to accommodate an infrared electromagnetic radiation measurement circuit described later herein. The groupings and number of groups of voltaic cells can be selected depending upon application requirements. The number of groups can be as few as two. Furthermore, the plurality of voltaic cells can be oriented in different ways, for example vertically, horizontally or a combination of the two orientations. The vehicle 100 is being described for the sake of overview and context and so for the sake of clarity and conciseness of description, the vehicle 100 will not be described in further detail herein.

[0108] Turning to Figure 2, the traction battery system 114 also comprises a cavity waveguide 120 formed between an infrared reflector 122 and a first side surface 124 at a first side 125 of the battery 116. In this regard, the infrared reflector 122 overlies the first side surface 124 of the battery in spaced relation thereto to provide a space between the infrared reflector 122 and the first side surface 124 of the battery. In some examples, the first side surface 124 of the battery 116 comprises a reflective layer (not shown), which contributed to the guiding of infrared electromagnetic waves by the cavity waveguide 120. However, in other examples, a degree of guiding of electromagnetic radiation can be achieved by virtue of the natural reflective properties of the first side surface 124 of the battery 116 in combination with the infrared reflector 122. In this and other examples, the cavity waveguide 120 need not be closed. The cavity waveguide 120 defines a volume through which electromagnetic radiation, for example infrared electromagnetic radiation, can be guides from a first location to a second location. The first location can be where a voltaic cell emitting the electromagnetic radiation is sited and the second location can be where an infrared electromagnetic radiation sensor device is sited to receive the emitted electromagnetic radiation. The volume can be defined between a first and a second waveguide surface, for example opposing surfaces, and the volume between the first and second waveguide surfaces constitutes the cavity of the waveguide cavity 120. Other surfaces can be provided to further or completely surround the volume, although in some examples the cavity can possess one or more openings, which can be an aperture, slot, gap or spacing.

[0109] An infrared electromagnetic radiation measurement apparatus 126 of the traction battery system 114 comprises an infrared electromagnetic radiation sensor apparatus comprising an infrared electromagnetic radiation sensor device 128 operably coupled to an infrared electromagnetic radiation measurement circuit 129, the infrared electromagnetic radiation sensor device 128 having a reception surface 131. Optionally, the infrared electromagnetic radiation sensor apparatus can comprise a filter 132, for example a filter configured to be transmissive to a predetermined range of electromagnetic radiation. In one example, the filter 132 is a low-pass filter, such as a filter that is transmissive only to wavelengths of electromagnetic radiation corresponding to temperatures above a predetermined temperature, for example above a predetermined temperature, such as about 70 degrees Celsius. In this example, the filter 132 is an optical filter that blocks light with a wavelength longer than a specific wavelength determined by the predetermined threshold temperature. The filter 132 is disposed between the cavity waveguide 120 and an infrared sensing array of the infrared electromagnetic radiation sensor device 128. The filter 132 can, as in this example, be external to the infrared electromagnetic radiation sensor device 128 or, in other examples, can be integrally formed with the infrared electromagnetic radiation sensor device 128, for example internal to the package of the infrared electromagnetic radiation sensor device 128. In this example, the filter 132 is spatially separated from the infrared electromagnetic radiation sensor device 128, the infrared electromagnetic radiation sensor device 128 comprising a field of view from the reception surface 131 thereof and the filter 132 can be disposed adjacent the reception surface 131 so that the field of view thereof is filtered without reducing the field of view. The filter 132 can abut the reception surface 131 of the infrared electromagnetic radiation sensor device 128. The infrared electromagnetic radiation sensor device 128 (with or without the filter 132) is oriented so that a propagation path of infrared electromagnetic radiation emitted by the battery 116 extends into the field of view of the infrared electromagnetic radiation sensor device 128.

[0110] In this example, the infrared electromagnetic radiation sensor device 128 comprises an array of sensing pixels. However, in other examples, the infrared electromagnetic radiation sensor device 128 can comprise a single sensing pixel.

[0111] Referring to Figure 3, in this example the infrared reflector 122 is planar, conforming to a linear function in a mathematical sense and is inclined at an angle of inclination, a , so that the planar cavity waveguide formed is, in this example, wedge-shaped. However, it should be appreciated that in other examples, the infrared reflector can provide a curved surface and so the cavity waveguide will not be planar. A first edge 130 of the infrared reflector 122 at a second side 133 of the battery 116 is closer to the first side surface 124 of the battery 116 than a second edge 134 of the infrared reflector 122 at a third side 136 of the battery 116. The battery 116 comprises a second side surface (not shown in Figure 3) at the second side 133 thereof and a third side surface 138 at the third side 136 thereof. The first edge 130 of the infrared reflector 122 is opposite the second edge 134 of the infrared reflector 122. The first edge 130 of the infrared reflector 122, in this example, meets the first side surface 124 of the battery 116. However, in other examples, the first edge 130 of the infrared reflector 122 can be spaced from the first side surface 124 of the battery 116. The infrared reflector 122 can be differently shaped to this example and alternative shapes and configurations will be described later herein.

[0112] In this example, the field of view of the infrared electromagnetic radiation sensor device 128 is directed into the cavity waveguide 120 between the infrared reflector 122 and the first side surface 124 of the battery 116. The field of view captures both the infrared reflector 122 and the first side surface 124 of the battery 116, but minimises capturing regions outside of this “scene” as much as possible. However, in other examples, the field of view captures the infrared reflector 122 but very little of or none of the first side surface 124 of the battery 116. Furthermore, a central reception axis (not shown in Figure 3) of the infrared electromagnetic radiation sensor device 128 is, in this example, substantially parallel with the first side surface 124 of the battery 116. In this example, the reception surface 131 of the infrared electromagnetic radiation sensor device 128 is located in or substantially parallel with a plane of the third side surface 138 at the third side 136 of the battery 116.

[0113] In the above example, one side of the infrared reflector 122 meets or is very close to the first side surface 124 of the battery 116. However, in another example, a greater spacing can be provided between the first edge 130 of the infrared reflector 122 and the first side surface 124, thereby providing an opening at the second side 133 of the battery 116, but still smaller than the opening at the third side 136 of the battery 116. An additional infrared electromagnetic radiation sensor device (not shown) of the infrared electromagnetic radiation sensor apparatus can be placed at the second side 133 of the battery 116, the field of view of the additional infrared electromagnetic radiation sensor device captures both the infrared reflector 122 and the first side surface 124 of the battery 116, but minimises capturing regions outside of this “scene” as much as possible. However, in other examples, the field of view of the additional infrared electromagnetic radiation sensor device captures the infrared reflector 122 but very little of or none of the first side surface 124 of the battery 116. Infrared electromagnetic radiation emitted by cells of the battery 116 can be detected by both infrared electromagnetic radiation sensor devices and any “hot spots” (regions of unusually high temperature) can be cross-referenced by the images captured by both infrared electromagnetic radiation sensor devices in order to improve identification of the location of any hot spots. It is also possible, in other examples, to position the infrared electromagnetic radiation sensor device 128 and the another infrared electromagnetic radiation sensor device at corners of the third side surface 138 and direct the respective fields of view into the cavity waveguide 120 between the infrared reflector 122 and the first side surface 124 of the battery 116, the respective fields of view of the infrared electromagnetic radiation sensor device 128 and the another infrared electromagnetic radiation sensor device overlapping. In such an example, the field of view of each of the infrared electromagnetic radiation sensor device 128 and the another infrared electromagnetic radiation sensor device can be oriented towards opposite corners of the cavity waveguide 120 where no infrared electromagnetic radiation sensor devices are sited.

[0114] In the above example, the infrared reflector 122 is inclined and overlies the first side surface 124 of the battery 116. However, in other examples, the infrared reflector 122 can extend substantially parallel with the first side surface 124 of thebattery 116. The respective fields of view of the infrared electromagnetic radiation sensor device 128 and the additional infrared electromagnetic radiation sensor device again capture both at least part of the infrared reflector 122 and the first side surface 124 of the battery 116, respectively, but minimises capturing regions outside of this “scene” as much as possible. However, in other examples, the respective fields of view of the infrared electromagnetic radiation sensor device 128 and the additional infrared electromagnetic radiation sensor device capture the infrared reflector 122 but very little of or none of the first side surface 124 of the battery 116.

[0115] Returning to the example of Figure 3, the voltaic cells of the battery 116 are arranged such that each of the plurality of voltaic cells can emit infrared electromagnetic radiation unobstructed by any of the other voltaic cells of the battery 116. For example, the plurality of voltaic cells can be generally cylindrical in shape and oriented in a generally upright position so that infrared electromagnetic radiation emitted from ends of the voltaic cells is not obstructed by neighbouring voltaic cells. However, in operation (Figure 4), a cell 200 of the battery 116 can develop a fault and overheat. In such circumstances, the cell 200 acts as a hot spot at the first side surface 124, in this example an upper side, of the battery 116. The cells of the battery 116, in any event, emit infrared electromagnetic radiation and contribute to a temperature profile across the first side 125 of the battery 116: the wavelength of the infrared electromagnetic radiation emitted by each cell of the battery 116 depends upon the individual temperature of each cell. As such, by measuring and analysing the wavelengths of infrared electromagnetic radiation emitted from the first side surface 124 of the battery 116, one or more regions of the first side surface 124 corresponding to one or more cells, respectively, emitting electromagnetic radiation below a predetermined wavelength can be identified and hence temperatures above a predetermined temperature can be identified. The infrared electromagnetic radiation measurement circuit 129 measures this temperature profile across the first side surface 124 of the battery 116 in order to identify one or more voltaic cells are overheating. Consequently, if one or more cells are malfunctioning and not operating within a temperaturewindow corresponding to normal operation, the cell or cells can be identified and appropriate steps taken.

[0116] Taking the example of the flat inclined infrared reflector 122 forming the cavity waveguide 120 with the first side surface 124 at the first side 125 of the battery 116, geometry can be employed to determine the position of the cell 200 relative to the position of the infrared electromagnetic radiation sensor device 128, which in this example comprises an array of sensing pixels.

[0117] In this regard, the infrared electromagnetic radiation sensor device 128 is located at a first height, hi , above the first side surface 124 of the battery 116 and the cell 200 is located a first distance, di, from the third side surface 138 of the battery 116 and hence horizontally from the infrared electromagnetic radiation sensor device 128. The central axis 140 of the infrared electromagnetic radiation sensor device 128 intersects the infrared reflector 122 at an additional, second distance, d2, beyond the first distance, di. A total distance, a, between the third side surface 138 and a second side surface 142 of the battery 116 is an additional, third, distance ds, beyond the sum of the first and second distances, di , d2. The height of the second edge 134 of the infrared reflector 122 is an additional, second, height, h2, above the first height, hi, of the infrared electromagnetic radiation sensor device 128 above the first side surface 124. As such, the first and second heights, hi, h2 and the total distances, a, are known, as is the angle, a , formed between the first side surface 124 and the infrared reflector 122.

[0118] In this and other examples described herein, when infrared electromagnetic radiation is emitted from the first side surface 124 of the battery 116, the cavity waveguide 120 is configured to direct the infrared electromagnetic radiation emitted towards the infrared electromagnetic radiation sensor device 128. In general, herein, the one or more cavity waveguides described direct or guide infrared electromagnetic radiation emitted from the first side surface 124 of the battery 116 to one or more respective infrared electromagnetic radiation sensor devices. In the present example, the infrared electromagnetic radiation is emitted from the first side surface 124 of the battery 116 at the first distance, di , from the third side 138 of the battery 116, the first distance, di, being measured along a lineparallel with the central axis 140 of the infrared electromagnetic radiation sensor device 128. The infrared electromagnetic radiation emitted by the cell 200 from the first side surface 124 of the battery 116 propagates towards the infrared reflector 122. The infrared electromagnetic radiation is reflected by the infrared reflector 122 at a region 143, which in practice is somewhat closer to the infrared electromagnetic radiation sensor device 128 than shown in Figure 4. However, owing to the law of reflection (angle of incidence being equal to the angle of reflection), it is possible to simplify to the representation shown in Figure 4, where the reflection region 143 d is generally above the cell 200. The emitted infrared electromagnetic radiation is reflected at the reflection region 143 towards the infrared electromagnetic radiation sensor device 128. It should also be noted that the reflection region 143 is generally larger than the cell 200. In this regard, the reflection point 143 is an additional, third, height, hs, above the first height, hi , when measures along a straight perpendicular line to the first side surface 124 of the battery 116 in this simplified example.

[0119] As the reflection point 143, presents as a hot spot in the field of view of the infrared electromagnetic radiation sensor device 128, the third height, h3is effectively known though simple calculation and is relative to the central axis 140 of the infrared electromagnetic radiation sensor device 128. Using the above known parameters associated with the infrared reflector 122 and third height, hs, it is possible to derive an algebraic expression for the first distance, di, to the cell 200 from the third side surface 138. In this regard, the following trigonometric relation can be used to derive an expression for the third distance, ds, in terms of the angle of inclination, a , and the first height, hi:

[0120] Equation (1 ) can be rearranged to give an expression for the third distance, d3:

[0121] Using the equivalence between two right-angled triangles:

[0122] Based upon the relation a = di + d2 + d3: di+ d2 = a - d3(4)

[0123] Substituting equation (2) into equation (4):

[0124] Equation (5) can then be used to substitute for (di + d2) in equation (3):

[0125] Rearranging equation (6), an expression for d2 can be obtained:

[0126] Rearranging equation (4) further, di can be expressed in terms of the total distance, a, and the second and third distances d2, d3: d1= a - d2- d3(8)

[0127] Equations (2) and (7) can then be substituted into equation (8) to yield:

[0128] Providing equation (9) with a denominator of h2-tan a and collecting like terms gives an expression for the first distance, di , in terms of the overall length, a, the angle of inclination, a , and the second and third heights, h2, h3:

[0129] As such, given the overall length, a, the angle of inclination, a , the first and second heights, hi, h2, are known and the position of the reflection point 143can be determined using the infrared electromagnetic radiation sensor device 128 and the third height, hs, calculated by the infrared electromagnetic radiation measurement circuit 129, the infrared electromagnetic radiation measurement circuit 129 can then calculate the first distance, di , from the third side surface 138 to the cell 200. This is, of course, simply in one dimension, but the infrared electromagnetic radiation sensor device 128 can also be used by the infrared electromagnetic radiation measurement circuit 129 to calculate a horizontal position to the reflection point 143 from the thermal image captured by the infrared electromagnetic radiation sensor device 128 and thus a horizontal distance of the reflection region 143 from one side of battery 116. The infrared electromagnetic radiation measurement circuit 129 can also comprise a storage device, for example a digital memory, to store a map of the cells of the battery 116 and the angle and distance calculated can be used to identify the cell 200 logically in order that action can be taken to mitigate the over-heating of the cell 200.

[0130] In the above example, the central axis 140 of the infrared electromagnetic radiation sensor device 128 is substantially horizontal and the reception surface 131 of the infrared electromagnetic radiation sensor device 128 is spaced from the third side surface 138 so that the field of view of the infrared electromagnetic radiation sensor device 128 captures both the infrared reflector 122 and the first side surface 124 of the battery 116, but minimises capturing regions outside of this “scene” as much as possible. However, in another example, the central axis 140 of the infrared electromagnetic radiation sensor device 128 can be oriented at an angle relative to the plane of the third side surface 138 (Figure 5) and hence, in this example the horizontal, thereby capturing very little or none of the first side surface 124 of the battery 116. Additionally or alternatively, the infrared electromagnetic radiation sensor device 128 can be oriented so that a field of view 144 of the infrared electromagnetic radiation sensor device 128 points towards the infrared reflector 122 (Figure 6) and therefore faces the infrared reflector 122. In this regard, the reflection regions 143 occupies an increased region of the thermal image captured by the infrared electromagnetic radiation sensor device 128 and thus improves sensitivity to lower temperatures as compared with directing the field of view of the infrared electromagnetic radiation sensor device 128 to capture moreof the first side surface 124 of the battery 116. In this regard, the field of view of the infrared electromagnetic radiation sensor device 128 captures the infrared reflector 122 but very little of the first side surface 124 of the battery 116. Additionally, the longitudinal detection range from the infrared electromagnetic radiation sensor device 128 and resolution are also increased. Furthermore, the orientation of the infrared electromagnetic radiation sensor device 128 lends itself well to incorporation onto a general battery control circuit board typically already provided to the side of the battery 116, thereby obviating the need for a separate dedicated circuit board for the infrared electromagnetic radiation sensor device 128 and thus reducing the overall manufacturing cost and complexity. In this example, the field of view of the infrared electromagnetic radiation sensor device 128 captures both the infrared reflector 122 and the first side surface 124 of the battery 116, but minimises capturing regions outside of this “scene” as much as possible. However, in other examples, the field of view of the infrared electromagnetic radiation sensor device 128 captures the infrared reflector 122 but very little of or none of the first side surface 124 of the battery 116. As such, the infrared reflector 122 is, at least in part, in the field of view 144 of the infrared electromagnetic radiation sensor device 128. In this and other examples, the first side surface 124 of the battery 116 can be, at least in part, in the field of view 144 of the infrared electromagnetic radiation sensor device 128. As in the previous example, the orientation of the infrared electromagnetic radiation sensor device 128 lends itself well to incorporation onto a general battery control circuit board typically already provided to the side of the battery 116, thereby obviating the need for a separate dedicated circuit board for the infrared electromagnetic radiation sensor device 128 and thus reducing the overall manufacturing cost and complexity.

[0131] In other examples, the infrared reflector 122 comprises a main portion 145 contiguous with an overhang return portion, for example a cowl portion 146 (Figure 7), which depends downwardly from the second edge 134 of the infrared reflector 122 at a side, for example the third side 136, of the battery 116 where the infrared electromagnetic radiation sensor device 128 is to be located, for example adjacent the third side surface 138, which is part of a peripheral boundary wall of the battery 116 in this example. The overhang return portion can extend as far as a level ofthe first side surface 124 of the battery 116. In this example, the cowl portion 146 forms an obtuse angle with the main portion 145.

[0132] The infrared electromagnetic radiation sensor device 128 is located beneath the cowl portion 146 and oriented so as to direct the field of view 144 thereof towards the cowl portion 146. It should also be appreciated that provision of the cowl portion 146 permits the infrared electromagnetic radiation sensor device 128 to be parallel and substantially level with the first side surface 124. In this regard, the plane of reception of the infrared electromagnetic radiation sensor device 128 is substantially parallel with the first side surface of the battery 118. In this example, the plane of reception of the infrared electromagnetic radiation sensor device 128 is substantially level with the first side surface 124 of the battery 116.

[0133] Turning to Figure 8, in another example, the main portion 145 of the infrared reflector 122 is substantially parallel with and overlies the first side surface 124 of the battery 116. The infrared reflector 122 also comprises the overhang return portion, for example the cowl portion 146, which depends downwardly from the second edge 134 of the infrared reflector 122 at a side, for example the third side 136, of the battery 116 where the infrared electromagnetic radiation sensor device 128 is to be located, for example adjacent the third side surface 138, which is part of the peripheral boundary wall of the battery 116 in this example. The overhang return portion can extend as far as the level of the first side surface 124 of the battery 116. Again, in this example, the cowl portion 146 forms an obtuse angle with the main portion 145.

[0134] The infrared electromagnetic radiation sensor device 128 is located beneath the cowl portion 146 and oriented so as to direct the field of view 144 thereof towards the cowl portion 146. It should also be appreciated that in this example, as in the previous example, provision of the cowl portion 146 permits the reception surface 131 of the infrared electromagnetic radiation sensor device 128 to be parallel and substantially level with the first side surface 124. In this example, the plane of reception of the infrared electromagnetic radiation sensor device 128 is substantially level with the first side surface 124 of the battery 116.

[0135] Although in the above examples, the infrared reflector 122 is a planar arrangement, whereby the infrared reflector 122 extends away from the first side surface 124 of the battery 116 according to a linear function, in another example the shape of the infrared reflector 122 can be non-linear in nature and the infrared reflector 112 can be curved. Referring to Figure 9, the infrared reflector 122 overlies and extends away from the first side surface 124 of the battery 116 in a non-linear manner. In this regard, the infrared reflector 122 is closest to two side edges of the battery 116, for example a first battery edge 148 where the second side surface 142 of the battery 116 meets the first side surface 124 and a second battery edge 150 where a fourth side surface 152 of the battery 116, adjacent the second side surface 142, meets the first side surface 124. The infrared reflector 122 extends away from the two edges 148, 150 (to which it is closest) in a curved manner until the infrared reflector 122 reaches a corner 154 of the first side surface 124 at the third side 136 of the battery 116. The infrared electromagnetic radiation sensor device 128 is positioned at the corner 154 where the infrared reflector 122 is farthest from the first side surface 124 and the field of view of the infrared electromagnetic radiation sensor device 128 captures both the infrared reflector 122 and the first side surface 124 of the battery 116, but minimises capturing regions outside of this “scene” as much as possible. However, in other examples, the field of view of the infrared electromagnetic radiation sensor device 128 captures the infrared reflector 122 but very little of or none of the first side surface 124 of the battery 116.

[0136] In the above examples, the infrared reflector 122 or the part of the infrared reflector 122 extending over the first side surface 124 is a formed as a single monotonically increasing surface. In this regard, the infrared reflector 122 or the part of the infrared reflector 122 extending over the first side surface 124 is a single part. However, as will now be described, the infrared reflector 122 can be formed from more than one portion.

[0137] Turning to Figure 10, the infrared reflector 122 loosely resembles the form of the infrared reflector 122 of Figure 9. However, the infrared reflector 122 is not curved in this example, although some curvature is possible as will be explained shortly herein. In this example, the infrared reflector 122 is formed from a firstplanar reflector part 156 and a second planar reflector part 158, which together overlie the first side surface 124 of the battery 116. The first and second reflector parts are non-parallel and non-coplanar. The first reflector part 156 is closest to the first battery edge 148 where the second side surface 142 of a periphery of the battery 116 meets the first side surface 124, and the second reflector part 158 is closest the second battery edge 150 where the fourth side surface 152 of the periphery of the battery 116, adjacent the second side surface 142, meets the first side surface 124. The first reflector part 156 extends away from the first battery edge 148 and the first side surface 124 to provide, with the first side surface 124, a first cavity waveguide part, and the second reflector part 158 extends away from the second battery edge 150 and the first side surface 124 to provide, with the with the first side surface 124, a second cavity waveguide part. The first and second reflector parts 154, 156 meet along a fold line to form a ridge 158 and the infrared reflector 122 is monotonic in two dimensions. The fold line does not necessarily require a single reflector to be folded and two parts, in this example, can be brought together at respective inclines relative to the first side surface 124 of the battery 116.

[0138] The ridge 160 is inclined at the angle of inclination, a , and is closest to the first side surface 124 at a first corner 153 of the battery 116 where the first battery edge 148 meets the second battery edge 150. The ridge 160 is farthest from the first side surface 124 above a second corner 154 of the battery 116, the second corner 154 being diagonally opposite the first corner 153. In this example, the fold line extends diagonally with respect to the first side surface 124 of the battery 116 and away from the first side surface 124 of the battery 116. The ridge 160 resembles a hip, for example like a hip of a roof. The infrared electromagnetic radiation sensor device 128 is positioned at the second corner 154 where the infrared reflector 122 is farthest from the first side surface 124 and the field of view of the infrared electromagnetic radiation sensor device 128 captures both the infrared reflector 122 and the first side surface 124 of the battery 116, but minimises capturing regions outside of this “scene” as much as possible. However, in other examples, the field of view of the infrared electromagnetic radiation sensor device128 captures the infrared reflector 122 but very little of or none of the first side surface 124 of the battery 116.

[0139] Although, in this example, the first and second reflector parts 156, 158 are planar, in other examples the first and second reflector parts 156, 158 can be curved surfaces that meet at the fold line 160.

[0140] Referring to Figure 11 , in another example, the fold line is a valley 162. The first and second planar reflector parts 156, 158 meet in a generally central position along the length of the battery 116 that notionally bisects the length of the battery 116. The first reflector part 156 of the infrared reflector 122 is furthest from the first side surface 124 at the second side 133 of the battery 116 and the second reflector part 158 of the infrared reflector 122 is furthest from the first side surface 124 at the third side 136 of the battery 116. The first and second reflector parts 156, 158 linearly extend towards each other and the first side surface 124 of the battery 116, and meet along the fold line, which in this example is close to or in contact with the first side surface 124 of the battery 116. The first and second reflector parts 156, 158 are, in this example, of equal dimensions. They are nonparallel and non-coplanar. In this example, the fold line is substantially parallel with the first side surface 124 of the battery 116. The first and second reflector parts 156, 158 overlie the first side surface 124 of the battery 116 and respectively form the angle of inclination, a , with the first side surface 124 of the battery 116, and with the first side surface 124 of the battery 116 cooperate to provide a first cavity waveguide part and a second cavity waveguide part.

[0141] The infrared electromagnetic radiation sensor device 128 is positioned at the second side 133 of the battery 116 and the field of view of the infrared electromagnetic radiation sensor device 128 is directed into a first space 164 between the first reflector part 156 and the first side surface 124 of the battery 116 and captures both the first reflector part 156 and the first side surface 124 of the battery 116, but minimises capturing regions outside of this “scene” as much as possible. However, in other examples, the field of view of the infrared electromagnetic radiation sensor device 128 captures the first reflector part 156 but very little of or none of the first side surface 124 of the battery 116. Anotherinfrared electromagnetic radiation sensor device 166 is positioned at the third side 136 of the battery 116 and the field of view of the another infrared electromagnetic radiation sensor device 166 is directed into a second space 168 between the second reflector part 158 and the first side surface 124 of the battery 116 and captures both the second reflector part 158 and the first side surface 124 of the battery 116, but minimises capturing regions outside of this “scene” as much as possible. However, in other examples, the field of view of the another infrared electromagnetic radiation sensor device 166 captures the second reflector part 158 but very little of or none of the first side surface 124 of the battery 116. One or both of the infrared electromagnetic radiation sensor devices 128, 166 can be oriented differently to as described above, for example so that the field of view of the infrared electromagnetic radiation sensor devices 128 is directed to the first reflector part 156 and / or the another infrared electromagnetic radiation sensor devices 128 is oriented towards the second reflector part 158.

[0142] As in the case of the previous example, in this example, the first and second reflector parts 156, 158 are planar, but in other examples the first and second reflector parts 156, 158 can be curved surfaces that meet at the fold line 160.

[0143] Turning to Figure 12, in another example, the first and second reflector parts 156, 158 mentioned above in relation to Figure 11 can be separate parts and hence the infrared reflector 122 is non-contiguous, but nevertheless overlies the first side surface 124 of the battery 116. The first planar reflector part 156 is trapezoidal in shape having a first side edge 170 closest to the first battery edge 148 where the second side surface 142 of the battery 116 meets the first side surface 124. The second planar reflector part 158 is also trapezoidal in shape and has a first side edge 172 closest a third battery edge 174 where the third side surface 138 of the battery 116, opposite the second side surface 142, meets the first side surface 124.

[0144] A second side edge 176 of the first reflector part 156 is opposite to and shorter than the first side edge 170 of the first reflector part 156. The second side edge 176 of the first part 156 is further from the first side surface 124 of the battery116 than the longer first side edge 170 of the first planar reflector part 156. The first reflector part 156 extends away from the first side surface 124 of the battery 116, from the first side edge 170 of the first reflector part 156, linearly and monotonically, and cooperates with the first side surface 124 of the battery 116 to provide a first cavity waveguide part. A second side edge 178 of the second reflector part 158 is opposite to and shorter than the first side edge 172 of the second reflector part 158. The second side edge 178 of the second reflector part 158 is further from the first side surface 124 of the battery 116 than the longer first side edge 172 of the second reflector part 158, and cooperates with the first side surface 124 of the battery 116 to provide a second cavity waveguide part. The second reflector part 158 extends away from the first side surface 124 of the battery 116, from the first side edge 172 of the second reflector part 158, linearly and monotonically.

[0145] The first reflector part 156 has a sloped contact edge 180 extending between the first and second side edges 170, 176 of the first reflector part 156. Similarly, the second reflector part 156 has a sloped contact edge 182 extending between the first and second side edges 172, 178 of the second reflector part 158. The sloped contact edges 180, 182 are disposed opposite each other and can touch at a contact point 184. In this example, the first and second reflector parts 156, 158 slope in opposite directions. Each of the first, and second reflector parts 156, 158 respectively form the angle of inclination, a, with the first side surface 124.

[0146] One or both of the infrared electromagnetic radiation sensor devices 128, 166 can be oriented differently to as described above, for example so that the field of view of the infrared electromagnetic radiation sensor devices 128 is directed to the first reflector part 156 and / or the another infrared electromagnetic radiation sensor devices 128 is oriented towards the second reflector part 158. As in the case of the previous example, in this example, the first and second reflector parts 156, 158 are planar, but in other examples the first and second reflector parts 156, 158 can be curved surfaces that meet at the fold line 160.

[0147] In some examples, the infrared reflector 122 can be formed from more than two reflector parts that together form a contiguous surface. The reflector parts can be planar or curved surfaces. Referring to Figure 13, the type of infrared reflector122 of Figure 3 can be formed from two or more planar reflector parts, for example the first planar reflector part 156, the second planar reflector part 158 and a third planar reflector part 186. As mentioned above, the first, second and third reflector parts 156, 158, 186 together form a contiguous surface that monotonically increases. As with the infrared reflector 122 of Figure 3, the infrared reflector 122 of Figure 13 is closest to the first side surface 124 of the battery 116 at the second side 133 thereof and furthest from the first side surface 124 at the third side 136 of the battery 116. In this example, the lateral sides of the infrared reflector 122 extending between the second side 133 and the third side 136 are open. The infrared electromagnetic radiation sensor device 128 is directed into the space between the infrared reflector 122 and the first side surface 124 of the battery 116, namely the cavity waveguide 120.

[0148] Turning to Figure 14, a closed or substantially closed infrared reflector configuration 188 comprises the first planar reflector part 156, the second planar reflector part 158, the third planar reflector part 186 and a fourth planar reflector part 190. In this example, the first, second, third, and fourth planar reflector parts 156, 158, 186, 190 are each triangular in shape and cooperate with the first side surface 124 of the battery 116 to form a pentahedral shape, for example a squarebased pyramid shape, that overlies the first side surface 124 of the battery 116. Of course, other polyhedral shapes are also possible. The first, second, third and fourth reflector parts 156, 158, 186, 190 are non-parallel and non-coplanar. In this regard, the third reflector part 186 is contiguous with the second reflector parts 158, and the fourth reflector part 190 is contiguous with the first reflector part 186 and the third reflector part 186. The first, second, third and fourth reflector parts 156, 158, 186, 190 cooperate with the first side surface 124 of the battery 116 to provide the cavity waveguide 120.

[0149] The first side surface 124 of the battery comprises a periphery 192, and the first, second, third and fourth reflector parts 156, 158, 186, 190 extend away from the first side surface of the battery 116 towards each other. Each of the first, second, third and fourth planar reflector parts 156, 158, 186, 190 have a first edge 194 closest to the first side surface 124 of the battery 116, the first edges 194 beingclosest to the periphery 192. In order examples, a clearance can be provided between the first edges 194 and the first side surface 124 of the battery 116.

[0150] As can be seen from Figure 14, the first side surface 124 is rectangular in shape and so the first and third reflector parts 156, 186 are the same size and the second and third reflector parts 158, 190 are the same size. Since the infrared reflector 122 is part of a pentahedral shape, the first, second, third and fourth reflector parts 156, 158, 186, 190 converge towards an apex point 196. Each of the first, second, third and fourth reflector parts 156, 158, 186, 190 form the angle of inclination, a, with the first side surface 124.

[0151] In this example, the infrared electromagnetic radiation sensor device 128 is disposed centrally within the pentahedral structure formed and is oriented so that the field of view 144 of the infrared electromagnetic radiation sensor device 128 is directed towards the apex point 196. In this regard, a recess or aperture (not shown) can be provided within the battery 116 to accommodate the infrared electromagnetic radiation sensor device 128. The infrared electromagnetic radiation sensor device 128 can, in order examples, be placed on the first side surface 124.

[0152] Turning to Figure 15, a variant of the configuration of Figure 15 comprises an aperture 198 at the apex point 196 and instead of the infrared electromagnetic radiation sensor device 128 being inside the pentahedral structure aimed towards the apex point 196, the infrared electromagnetic radiation sensor device 128 is disposed above the aperture 198 and the field of view 144 of the infrared electromagnetic radiation sensor device 128 is directed towards the first side surface 124.

[0153] In some examples, the battery 116 comprises the plurality voltaic cells of the battery 116 can be organised as a first group of voltaic cells 200 and a second group of voltaic cells 202, a siting space 204 being provided between the first and second groups of voltaic cells 200, 202. In such examples, the first group of voltaic cells 200 is electrically coupled to the second group of voltaic cells 202. The infrared electromagnetic radiation sensor device 128 is placed in the siting space204 between the first and second groups of voltaic cells 200, 202 (Figures 16, 17 and 18). In other examples, a single battery can be provided comprising a recess in which to site the infrared electromagnetic radiation sensor device 128. In the examples of Figures 16, 17 and 18, the infrared reflector 122 is wing-like and comprises a central valley 206 where the first reflector portion 156 and the second reflector portion 158 meet. In some examples, for example those of Figures 17 and 18, the first and second reflector portions 156, 158 are not planar but curved surfaces instead. Although shown as relatively short, the infrared reflectors 122 of Figures 16, 17 and 18 are sufficiently dimensioned to provide a reflecting surface or surfaces for all cells of the battery 116.

[0154] As mentioned in previous examples above, the infrared electromagnetic radiation sensor device 128 comprises a reception surface 131 , and in the examples of Figures 16, 17 and 18, and indeed the examples where battery 116 comprises a generally central recess serving as the siting space, the reception surface 131 of the infrared electromagnetic radiation sensor apparatus 128 is substantially level with the first side surface 124 of the battery 116.

[0155] In the above examples, the first side surface 124 on the first side 125 of the battery 116 is considered the side most informative for the purpose of detection of overheating voltaic cells. In this regard, the side is considered most informative owing to an assumed vertical orientation of the plurality of voltaic cells such that the electromagnetic emissions from more voltaic cells are detectable as compared with other sides of the battery 116 where emissions can be obstructed by structural features of the battery 116 and / or other voltaic cells making accurate detection more challenging. However, in other examples, depending upon the construction of the battery 116, another side of the battery 116 can be considered most informative and so treated as the first side 125 of the battery 116 and the surface of the battery 116 on that first side 125 treated as the first side surface 124. In one example, this can be a peripheral boundary wall of the battery 116.

Claims

35Claims1 . A traction battery system for a vehicle, the system comprising: a battery comprising a plurality of voltaic cells and having a first side at which a voltaic cell of the battery can emit infrared electromagnetic radiation; a thermal measurement apparatus for measuring a temperature in respect of the first side of the battery and detecting overheating of the voltaic cell, the apparatus comprising: an infrared reflector substantially overlying the first side of the battery in spaced relation thereto, the infrared reflector and the first side of the battery cooperating to provide a cavity waveguide; and an infrared electromagnetic radiation measurement sensor apparatus comprising an infrared electromagnetic radiation sensor device having a field of view; wherein the field of view of the infrared electromagnetic radiation measurement sensor apparatus is directed into a space between the infrared reflector and the first side of the battery.

2. A system as claimed in Claim 1 , wherein the infrared reflector extends away from the first side of the battery.

3. A system as claimed in Claim 1 or Claim 2, wherein the cavity waveguide is configured to direct, when in use, infrared electromagnetic radiation towards the infrared electromagnetic radiation sensor device.

4. A system as claimed in Claim 1 or Claim 2 or Claim 3, wherein the infrared electromagnetic radiation sensor device has a plane of reception and the plane of reception is oriented so as to be crossed, when in use, by a propagation path of the infrared electromagnetic radiation.

5. A system as claimed in any one of the preceding claims, wherein the infrared electromagnetic radiation measurement sensor apparatus comprises an array of sensing pixels.

366. A system as claimed in any one of Claims 1 to 4, wherein the infrared electromagnetic radiation measurement sensor apparatus comprises an array of sensing pixels for measuring a spatial temperature profile across the first side of the battery caused, when in use, by the plurality of voltaic cells.

7. A system as claimed in Claim 6, further comprising: an infrared electromagnetic radiation measurement circuit configured to analyse the spatial temperature profile across the first side of the battery and to identify a location of an overheated voltaic cell of the plurality of voltaic cells.

8. A system as claimed in any one of the preceding claims, wherein the infrared electromagnetic radiation measurement sensor apparatus further comprises a low-pass filter disposed between the infrared reflector and an infrared sensing element of the infrared electromagnetic radiation sensor device.

9. A system as claimed in any one of the preceding claims, wherein the infrared reflector is, at least in part, in the field of view of the infrared electromagnetic radiation sensor device.

10. A system as claimed in any one of the preceding claims, wherein a first edge of the infrared reflector at a second side of the battery is closer to the battery than a second edge of infrared reflector at a third side of the battery, the first edge of the infrared reflector being opposite the second edge of the infrared reflector.

11. A system as claimed in any one of the preceding claims, wherein the infrared reflector is shaped.

12. A system as claimed in any one of the preceding claims, wherein the infrared reflector is curved.

13. A system as claimed in any one of Claims 1 to 11 , wherein the infrared reflector comprises a fold.

14. A system as claimed in Claim 12, wherein the fold creates a ridge in the infrared reflector.

15. A system as claimed in Claim 14, wherein the ridge extends diagonally with respect to the first side of the battery.

16. A system as claimed in Claim 13, wherein the fold creates a valley in the infrared reflector.

17. A system as claimed in any one of the preceding claims, wherein the infrared reflector comprises an overhang return portion that extends towards a level of the first side of the battery.

18. A system as claimed in Claim 17, wherein the infrared reflector comprises a main portion contiguous with the overhang return portion, the overhang return portion subtending an obtuse angle with the main portion.

19. A system as claimed in Claim 10, wherein the infrared electromagnetic radiation sensor device is disposed at the third side of the battery.

20. A system as claimed in Claim 19, wherein: the infrared electromagnetic radiation measurement sensor apparatus comprises another infrared electromagnetic radiation sensor device; and the another infrared electromagnetic radiation sensor device is disposed at the second side of the battery and has a field of view directed into the space between the first side of the battery and the infrared reflector.21 . A system as claimed in any one of Claims 1 to 9 or 16, wherein: the infrared electromagnetic radiation measurement sensor apparatus comprises another infrared electromagnetic radiation sensor device; and the battery is elongate and comprises a first end longitudinally separated and distal from a second end;the infrared electromagnetic radiation sensor device is disposed at the first end; and the another infrared electromagnetic radiation sensor device is disposed at the second end of the battery and has a field of view directed into the space between the first side of the battery and the infrared reflector.

22. A system as claimed in any one of Claims 12 to 15, wherein the infrared electromagnetic radiation sensor device is disposed at a first corner of the first side of the battery.

23. A system as claimed in Claim 16, wherein the battery comprises a first group of interconnected voltaic cells electrically coupled to a second group of interconnected voltaic cells, a space being provided between the first and second groups of voltaic cells; and the infrared electromagnetic radiation sensor device is disposed in the space between the first and second groups of voltaic cells.

24. A system as claimed in Claim 17 of Claim 18, wherein the infrared electromagnetic radiation sensor device is disposed beneath the overhang return portion; the infrared electromagnetic radiation sensor device comprises a plane of reception, the plane of reception being substantially parallel with the first side of the battery; and the infrared electromagnetic radiation sensor device is disposed to a side of the battery adjacent a peripheral boundary wall of the battery.

25. A traction battery system for a vehicle, the system comprising: a battery comprising a plurality of voltaic cells and having a first side at which each a voltaic cell of the battery can emit infrared electromagnetic radiation; a thermal measurement apparatus for measuring a temperature in respect of the first side of the battery and detecting overheating of the voltaic cell, the apparatus comprising:39 an infrared reflector substantially overlying the first side of the battery in spaced relation thereto, the infrared reflector extending away from the first side of the battery; and an infrared electromagnetic radiation measurement sensor apparatus comprising an infrared electromagnetic radiation sensor device having a field of view; wherein the infrared reflector comprises a first reflector part and a second reflector part, the first and second reflector parts being non-parallel and non- coplanar and respectively cooperating with the first side of the battery to provide one or more cavity waveguides; and the field of view of the infrared electromagnetic radiation measurement sensor apparatus is directed into the one or more cavity waveguides.

26. A system as claimed in Claim 25, wherein the first reflector part is contiguous with the second reflector part.

27. A system as claimed in Claim 25 or Claim 26, wherein the infrared reflector comprises a ridge line, the ridge line extending away from the first side of the battery.

28. A system as claimed in Claim 27, wherein the ridge line extends diagonally with respect to the first side of the battery.

29. A system as claimed in any one of Claims 25 to 28, wherein the plurality of voltaic cells of the battery comprises a periphery adjacent the first surface of the battery; the periphery comprises a first side adjacent a second side; the first reflector part extends away from the first side of the battery and towards the second reflector part from the first side of the periphery; and the second reflector part extends away from the first side of the battery and towards the first reflector part from the second side of the periphery.4030. A system as claimed in Claim 25 or Claim 26, wherein the first and second reflector parts cooperate to form a valley or valley-like shape therebetween, the first reflector part extending towards the second reflector part.31 . A system as claimed in Claim 30, wherein the plurality of voltaic cells of the battery comprises a periphery adjacent the first side of the battery; the periphery comprises a first side opposite a second side; the first reflector part extends from first side of the periphery towards the second side of the periphery; and the second reflector part extends from the second side of the periphery towards the first side of the periphery.

32. A system as claimed in Claim 31 , wherein the first and second reflector parts extend towards the first side of the battery from the first and second sides of the periphery, respectively, and meeting to form the valley.

33. A system as claimed in Claim 25, wherein the plurality of voltaic cells of the battery comprises a periphery adjacent the first side of the battery; the periphery comprises a first side opposite a second side; the first reflector part extends away from the first side of the periphery and the first side of the battery in a first direction; the second reflector part extends away from the second side of the periphery and the first side of the battery in a second direction; and the first and second directions are opposite directions.

34. A system as claimed in Claim 33, wherein the first reflector part is closest to the first side of the battery at the second side of the periphery, and the second reflector part is closest to the first side of the battery at the first side of the periphery.

35. A system as claimed in Claim 33 or Claim 34, wherein the first and second reflector parts are respectively trapezoidal in shape.4136. A system as claimed in Claim 25, wherein the infrared reflector further comprises: a third reflector part; a fourth reflector part; and the third reflector part is contiguous with the second reflector part and the fourth reflector part is contiguous with the first and third reflector parts.

37. A system as claimed in Claim 36, wherein the plurality of voltaic cells of the battery comprises a periphery adjacent the first side of the battery; the first, second, third and fourth reflector parts extend away from the first side of the battery and towards each other; the first, second, third and fourth reflector parts each have a first edge closest to the first side of the battery; and the first edge of each of the first, second, third and fourth reflector parts is closest to the periphery.

38. A system as claimed in Claim 36 or Claim 37, wherein the first, second, third and fourth reflector parts are triangular in shape.

39. A system as claimed in Claim 36 or Claim 37 or Claim 38, wherein the first and third reflector parts are the same size and the second and fourth reflector parts are the same size.

40. A system as claimed in any one of Claims 36 to 39, wherein the first, second, third and fourth reflector parts and the first side of the battery together form a pentahedral structure.41 . A system as claimed in any one of Claims 36 to 40, wherein the first, second, third and fourth reflector parts converge towards an apex point.4242. A system as claimed in Claim 41 , further comprising an aperture at the apex point.

43. A system as claimed in any one of Claims 25 to 42, wherein the one or more cavity waveguides are oriented to direct, when in use, infrared electromagnetic radiation towards the infrared electromagnetic radiation sensor device.

44. A system as claimed in any one of Claims 25 to 43, wherein the infrared electromagnetic radiation sensor device has a plane of reception and the plane of reception is oriented so as to be crossed, when in use, by a propagation path of the infrared electromagnetic radiation.

45. A system as claimed in any one of Claims 25 to 44, wherein the infrared electromagnetic radiation measurement sensor apparatus comprises an array of sensing pixels for measuring a spatial temperature profile across the first side of the battery caused, when in use, by the plurality of voltaic cells.

46. A system as claimed in Claim 45, further comprising: an infrared electromagnetic radiation measurement circuit configured to analyse the spatial temperature profile across the first side of the battery and to identify a location of an overheated voltaic cell of the plurality of voltaic cells.

47. A system as claimed in any one of Claims 25 to 44, wherein the infrared electromagnetic radiation measurement sensor apparatus comprises a single sensing pixel.

48. A system as claimed in any one of Claims 25 to 47, wherein the infrared electromagnetic radiation measurement sensor apparatus further comprises a low-pass optical filter disposed between the infrared reflector and an infrared sensing element of the infrared electromagnetic radiation sensor device.4349. A system as claimed in any one of Claims 25 to 48, wherein the infrared reflector is, at least in part, in the field of view of the infrared electromagnetic radiation sensor device.

50. A system as claimed in any one of Claims 25 to 29, wherein the infrared electromagnetic radiation measurement sensor device is disposed at a first corner of the first side of the battery.51 . A system as claimed in Claim 31 or Claim 32, wherein: the infrared electromagnetic radiation measurement sensor apparatus comprises another infrared electromagnetic radiation sensor device; and the infrared electromagnetic radiation sensor device is disposed at the first side of the periphery and the field of view thereof is directed into a first space between the first reflector part and the first side of the battery; and the another infrared electromagnetic radiation sensor device is disposed at the second side of the periphery and has a field of view directed into a second space between the second reflector part and the first side of the battery.

52. A system as claimed in Claim 33 or Claim 34 or Claim 35, wherein: the electromagnetic radiation measurement sensor apparatus comprises another infrared electromagnetic radiation sensor device; and the infrared electromagnetic radiation sensor device is disposed at a first corner of the first side of the battery; and the another electromagnetic radiation sensor device is disposed at a second corner of the first side of the battery, the second corner being diagonally opposite the first corner.

53. A system as claimed in Claim 42, wherein the infrared electromagnetic radiation sensor device is disposed in the aperture at the apex point facing towards the first side of the battery.4454. A system as claimed in Claim 41 , wherein the infrared electromagnetic radiation sensor device is disposed at a level of the first side of the battery and directed towards the apex point.

55. A system as claimed in any one of Claims 25 to 54, wherein the battery comprises a first group of interconnected voltaic cells electrically coupled to a second group of interconnected voltaic cells, a space being provided between the first and second groups of voltaic cells; and the infrared electromagnetic radiation sensor device is disposed in the space between the first and second groups of voltaic cells.

56. A system as claimed in Claim 25, wherein the infrared reflector comprises an overhang return portion that extends towards a level of the first side of the battery.

57. A system as claimed in Claim 25, wherein the first reflector part comprises an overhang return portion that extends towards a level of the first side of the battery.

58. A system as claimed in Claim 56 or Claim 57, wherein the infrared electromagnetic radiation sensor device is disposed beneath the overhang return portion; the infrared electromagnetic radiation sensor device comprises a plane of reception, the plane of reception being substantially parallel with the first side of the battery; and the infrared electromagnetic radiation sensor device is disposed to a side of the battery adjacent a periphery of the plurality of voltaic cells.

59. A traction battery system for a vehicle, the system comprising: a battery comprising a plurality of voltaic cells and having a first side from which each of the plurality of voltaic cells can emit infrared electromagnetic radiation unobstructed by any of the other voltaic cells of the plurality of voltaic cells;45 a thermal measurement apparatus for measuring a spatial temperature profile across the first side of the battery caused, when in use, by the plurality of voltaic cells, the apparatus comprising: an infrared reflector substantially overlying the battery in spaced relation thereto, the infrared reflector and the first side of the battery cooperating to provide a cavity waveguide; an infrared electromagnetic radiation measurement sensor apparatus comprising an infrared electromagnetic radiation sensor device having a field of view and a reception window; and the infrared electromagnetic radiation measurement sensor apparatus further comprises a low-pass optical filter disposed between the planar cavity waveguide and an infrared sensing element of the infrared electromagnetic radiation sensor device; wherein the field of view of the infrared electromagnetic radiation measurement sensor apparatus is directed into a space between the infrared reflector and the first side of the battery.

60. A system as claimed in Claim 59, wherein the infrared electromagnetic radiation sensor device comprises an array of sensing pixels.

61. A system as claimed in Claim 59 or Claim 60, wherein the infrared electromagnetic radiation sensor device comprises a single sensing pixel.

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