Method and apparatus

Abstract

A method for performing a field mapping of a cell under a load is provided. The method includes the following steps: providing a cell; providing a Hall effect sensor including a graphene conductor for measuring a magnetic field; positioning the Hall effect sensor at a first position adjacent to the surface of the cell; applying a load to the cell; and measuring the output of the Hall effect sensor.

Description

BACKGROUND OF THE DISCLOSURE

[0001] The present disclosure relates to devices for monitoring units.

[0002] Rechargeable batteries (whether a single cell, battery or battery pack) are typically equipped with a battery management system (BMS). A battery management system is an electronic system that manages the battery, particularly to maintain the safety and efficiency of the battery. For example, the battery management system can prohibit the battery from operating outside its safe operating region, monitor its state, calculate secondary data, report the data, control the battery environment, authenticate the battery, and / or balance the battery.

[0003] Typically, the safety and efficiency of the battery are monitored based on temperature data at the overall battery pack level (i.e., across the entire battery, rather than for individual cells). Since this data is limited and imprecise, the safety standards for the battery must be set at an overly cautious level because local problems in the battery may not be detected. The data may be difficult to correlate with specific failure modes of the cell, particularly because it may be masked or obscured by normal temperature fluctuations in the battery.

[0004] As a result, the battery is taken out of service before it is necessary. This results in increased costs for the owner of the device powered by the battery and only a small increase in efficiency. It is also environmentally damaging because old batteries are difficult to dispose of in an environmentally friendly manner.

[0005] Accordingly, there is a need for a device and a method of using the device to better monitor the battery to characterize failure modes so that more accurate safety limits can be set.

[0006] Hall effect sensors (also known as Hall sensors) are components known in the art. It is a transducer that changes its output voltage in response to a magnetic field. In a Hall sensor, a conductor is provided with a current applied along it, and in the presence of a magnetic field, electrons are deflected, thereby generating a voltage perpendicular to the drive current. In particular, for a Hall sensor, a thin strip of conductor has a current applied along it, and in the presence of a magnetic field, electrons are deflected towards one edge of the conductor strip, thereby creating a voltage gradient (perpendicular to the feed current) across the short side of the strip. The conductor is typically disposed on a substrate layer. In contrast to inductive sensors, the advantage of Hall sensors is that they can detect static (unchanging) magnetic fields.

[0007] The current density of a cell in a battery is a parameter that can be monitored to determine the health of the cell. Current density is the amount of electric charge flowing through a unit area of a selected cross-section per unit time, measured in amperes per square meter. This current density can be measured based on the magnetic field generated by the cell.

[0008] A review of possible techniques is presented in "Magnetic tomography for lead acid batteries" by Harrison et al., which explores the measurement of magnetic fields to determine current distribution. This represents a high-level technical review, but does not provide any solutions that are feasible on a commercial scale. The use of Hall effect sensors is discouraged because they are "not sensitive enough to read external magnetic fields".

[0009] US 2015 / 0061602 A1 relates to an electrochemical cell having a magnetic sensor. The magnetic sensor includes an array of magnetic field sensors, each magnetic field sensor having an organic p-n junction. Again, the use of Hall effect sensors is discouraged because "such known sensors are generally inflexible because they are composed of brittle materials... or require a defined geometry that cannot be integrated in the electrode stack", such that "the connection of the sensor to the battery housing would be too far to reliably detect small local currents in the cell with high resolution".

[0010] "Batch-fabricated high-performance graphene Hall elements" by Xu et al. discloses the use of graphene for Hall elements.

[0011] WO 2020 / 010624 A1 discloses a battery testing method and system and a battery analysis device.

[0012] CN 106 750 469A discloses a production device and production process for a graphene film coil.

[0013] US 2017 / 067970 A1 discloses a graphene Hall sensor.

[0014] US 2014 / 346579 A1 discloses a magnetic field sensor device.

[0015] US 2018 / 231620 A1 discloses a charge carrier Hall effect sensor.

[0016] "A New Type of Robot System for High-Resolution FieldMapping" by Haake et al. relates to a field scanner that enables the measurement of the field distribution within a gigahertz transverse electromagnetic cell.

[0017] Therefore, there is a need for an inexpensive device and method for monitoring the current density of a cell.

[0018] The battery management system can also monitor the current input and / or output of the cell to monitor the health of the battery. This will provide an indication of how the resistance changes, but not a direct measurement of the health of the battery itself. Typically, this measurement is carried out via a shunt resistor. The shunt resistor is placed in series with the load of the circuit and the voltage drop across the shunt resistor is measured. The current can then be calculated according to Ohm's law. Typically, the shunt resistor will have a low resistance, such as about 1 mOhm.

[0019] This shunt resistor measurement typically has a low resolution. Additionally, if the shunt resistor fails, the entire circuit (which can be a cell or an entire battery pack) will also fail.

[0020] Therefore, there is a need for an improved method of measuring the input or output current of a cell. Summary of the Invention

[0021] The present invention provides a method for field mapping a cell under load, comprising the steps of: providing a cell; providing a Hall effect sensor comprising a graphene conductor for measuring a magnetic field; positioning the Hall effect sensor at a first position adjacent to the surface of the cell; applying a load to the cell; and measuring the output of the Hall effect sensor. Such a Hall effect sensor is capable of detecting the current density in the cell with high sensitivity and over a wide range. Thus, a single Hall effect sensor can appropriately map the cell for loads with different power levels.

[0022] The method may further comprise the steps of: moving the Hall effect sensor from the first position to a second position adjacent to the surface of the cell; and measuring the output of the Hall effect sensor at the second position. This allows a map of the cell to be formed based on the local current density across the cell.

[0023] The method may further comprise the steps of: moving the Hall effect sensor from the second position to a series of N subsequent positions adjacent to the surface of the cell; and measuring the output of the Hall effect sensor at each of the subsequent positions, wherein the N subsequent positions are distributed over the surface of the cell. This allows the map of the cell to be evenly distributed to give an indication of the overall health of the entire cell.

[0024] The N subsequent positions may form an array on the surface of the cell. The array allows the entire cell to be appropriately mapped.

[0025] The Hall effect sensor may be part of an array of Hall effect sensors, each of the Hall effect sensors being placed adjacent to the cell to detect the magnetic field within the cell. The array allows the entire cell to be appropriately mapped.

[0026] The array can be evenly distributed on the surface of the cell. The even distribution on the surface of the cell reduces the risk of local defects in the cell being missed.

[0027] The method may further include the steps of: monitoring the measured output of the Hall effect sensor; identifying a change in the magnetic field indicative of a cell failure; and determining the location of the cell failure within the cell.

[0028] The present invention also provides a use of a Hall effect sensor including a graphene conductor for measuring the magnetic field of a cell. As above, such a Hall effect sensor can detect the magnetic field in the cell with high sensitivity and over a wide range. Thus, a single Hall effect sensor can appropriately map the cell for loads with different power levels.

[0029] The magnetic field can be converted into a local current density. The local current density provides information about the health of the cell.

[0030] The present invention also provides a use of a Hall effect sensor including a graphene conductor for measuring the input current or output current of a cell. Such a Hall effect sensor can determine the input current or output current of the cell without the need for a shunt resistor. Thus, even if the sensor fails, the circuit itself will not be damaged. This is contrary to a shunt resistor, the failure of which will also cause the failure of the entire circuit.

[0031] The present invention also provides an apparatus for field mapping a cell under load, the apparatus including an array of Hall effect sensors, each Hall effect sensor including a graphene conductor for measuring a magnetic field. The array of Hall effect sensors allows the health of the cell to be monitored at multiple points.

[0032] The present invention also provides an apparatus for field mapping a cell under load, the apparatus including a Hall effect sensor mounted on an actuation system configured to move the Hall effect sensor between a plurality of positions corresponding to positions on the cell. Moving the Hall effect sensor allows the health of the cell to be monitored at multiple points.

[0033] The plurality of positions may form an array. Such a regularly arranged structure can improve the overall mapping of the cell.

[0034] The present invention also provides an apparatus for performing a field mapping of a cell under load, comprising: a pickup coil for being placed adjacent to the cell such that a current is generated in the pickup coil in response to the magnetic field of the cell; a measurement coil in electrical communication with the pickup coil such that the current in the pickup coil is transmitted to generate a current in the measurement coil; and a magnetic field sensor arranged to detect the magnetic field generated by the current in the measurement coil. This provides a simple way to measure the current density of the cell using a technique that can be easily manufactured. In addition, the number of connections from the cell can be reduced, which improves the hermeticity of the cell to the ingress of oxygen and water.

[0035] The pickup coil can be one of a plurality of pickup coils, each pickup coil for being placed adjacent to the cell such that a current is generated in each pickup coil in response to the magnetic field of the cell. The plurality of pickup coils allows determination of a health profile on the cell by making measurements at multiple locations.

[0036] The plurality of pickup coils can include: a plurality of array coils arranged in an array. Array coils are typically regularly repeating patterns, which allows the establishment of the profile of the cell.

[0037] The plurality of pickup coils can include: a plurality of nested coils, each nested coil arranged to overlap with at least one other pickup coil of the plurality of pickup coils. Using such nested coils, one coil can be used to measure the integrated field over a large area, while the inner nested coil can be used to determine the local field. In this way, the relative spatial variation can be measured, helping to cancel out the common-mode field generated by external sources including the Earth's magnetic field.

[0038] At least one pickup coil of the plurality of pickup coils can be both an array coil and a nested coil. This allows the formation of the cell profile while canceling out the spatial variation. Specifically, the entire array can be disposed within an outer nested coil, such as a main coil.

[0039] The plurality of pickup coils can include: a main coil surrounding each of the plurality of pickup coils. The main coil can effectively cancel out the spatial variation of the pickup coil it encloses.

[0040] Each pickup coil of the plurality of pickup coils can be in electrical communication with a corresponding measurement coil such that the current in the pickup coil is transmitted to generate a current in the corresponding measurement coil, and each measurement coil has a corresponding magnetic field sensor arranged to detect the magnetic field generated by the current in the corresponding measurement coil.

[0041] Each of the plurality of pickup coils can be in electrical communication with a multiplexer, and the measurement coils are in electrical communication with the multiplexer, wherein the multiplexer is configured to selectively transmit the current of one of the pickup coils to the measurement coil. This further reduces the number of connections leaving the cell.

[0042] The multiplexer can be configured to sequentially cycle through each of the pick-up coils to transmit the current of each of the pick-up coils to the measurement coil in sequence. In this way, each of the pick-up coils can be sequentially sampled to map the entire unit.

[0043] Each magnetic field sensor can be a Hall effect sensor, preferably a Hall effect sensor including a graphene conductor for measuring a magnetic field. Due to its resolution and sensitivity, such a sensor is particularly effective for this purpose.

[0044] The array can be evenly distributed on the surface of the unit. This uniform distribution reduces the chance of anomalies in the unit being missed.

[0045] The present invention also provides an assembly including the device and the unit. The assembly allows the benefits of the Hall effect sensor discussed above to be realized.

[0046] The assembly can further include a battery management system arranged to receive the outputs of each Hall effect sensor as inputs. The battery management system can use these outputs as part of a larger management system to actively manage the unit.

[0047] The battery management system can be configured to generate a map of the local current density of the unit based on the outputs of each Hall effect sensor. The map can show areas of deviation in the unit and can therefore be used to predict failure rates and / or failure modes.

[0048] In all of the above cases, the Hall effect sensor can include: a substrate having a layer structure thereon; the layer structure including: a lower layer on a first region of the substrate, wherein the lower layer includes one or more graphene layers extending through the lower layer, and an upper layer on the lower layer, and the upper layer is formed of a dielectric material, wherein the graphene and the upper layer are in the shape of a cross with four arms and share a continuous outer edge surface; ohmic contacts provided on another region of the substrate and in direct contact with one or more graphene layers via the continuous outer edge surface; and four ohmic contacts, each provided on another region of the substrate and in direct contact with the distal portion of the edge surface of each of the four arms of the cross; and a continuous anti-air coating surrounding the layer structure or spanning the substrate, the layer structure, and at least one ohmic contact. Such a Hall effect sensor provides improved sensitivity and is therefore particularly useful for the above methods, uses, and devices.

[0049] The substrate can be sapphire, silicon, silicon dioxide, silicon nitride, silicon carbide, germanium, or a III-V semiconductor, preferably sapphire or silicon.

[0050] A Hall effect sensor may include: a sapphire substrate having a layer structure thereon; the layer structure including: a single layer of graphene on a first region of the sapphire substrate, and an alumina layer on the single layer of graphene, wherein the graphene and the alumina are in a cross shape with four arms and share a continuous outer edge surface; four gold ohmic contacts, each contact being disposed on another region of the sapphire substrate and directly contacting a distal portion of the edge surface of each of the four arms of the cross; and a continuous alumina coating that surrounds the layer structure. Such a Hall effect sensor provides improved sensitivity and is thus particularly useful for the above-mentioned methods, uses, and devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A schematic diagram of a device for a monitoring unit is shown;

[0052] Figure 1A A schematic diagram of another device for a monitoring unit is shown;

[0053] Figure 2 A schematic diagram of an alternative device for a monitoring unit is shown;

[0054] Figure 3 A schematic diagram of another alternative device for a monitoring unit is shown;

[0055] Figure 4 A schematic diagram of Figure 3 an alternative arrangement of the device is shown;

[0056] Figure 5 A schematic diagram of Figure 3 another alternative arrangement of the device is shown;

[0057] Figure 6 A schematic diagram of Figure 3 another alternative arrangement of the device is shown; and

[0058] Figure 7 A schematic circuit diagram of a device for monitoring the input current and / or output current of a monitoring unit is shown. DETAILED DESCRIPTION

[0059] For example, a Hall effect sensor suitable for the present application is disclosed in WO 2019 / 138232 A1, the entire content of which is incorporated herein by reference. Specifically, WO 2019 / 138232 A1 discloses that a Hall effect sensor can be configured such that the conductor of the sensor is formed of graphene. As discussed in the background art, a Hall effect sensor includes a conventional thin strip of conductor having a current applied therealong. When a magnetic field is applied to the Hall effect sensor, the electrons in the current are deflected towards one edge of the conductive strip. This then creates a voltage gradient across the strip (i.e., in a direction transverse or perpendicular to the current).

[0060] Graphene is a known material and a large number of applications have been proposed due to the theoretically extraordinary properties of the material. Good examples of such properties and applications are described in detail in “The Rise of Graphene” by A.K. Geim and K.S. Novoselev, Nature Materials, Volume 6, March 2007, 183 - 191.

[0061] A Hall effect sensor having a graphene conductor exhibits high sensitivity and resolution. This is due to the low sheet carrier concentration of graphene. The lower the sheet carrier concentration, the higher the sensitivity of the Hall effect sensor. Any contaminants in the graphene (such as residues from copper catalysts, polymer transfer, etc.) will increase the sheet carrier concentration and thus reduce the sensitivity of the resulting Hall effect sensor.

[0062] High resolution and high sensitivity allow the Hall effect sensor to detect current densities within a wide range of values without the need to replace the Hall effect sensor. Conventional Hall effect sensors are typically only suitable for a relatively narrow range of usage scenarios. Therefore, a conventional Hall effect sensor must be selected to sense a specific usage scenario.

[0063] For example, a specific usage scenario where the current density can be detected is in the battery of a vehicle such as an automobile. Such a battery can be loaded with low - power components (such as a car radio) or high - power components (such as a car starter motor), and this helps to test the battery health on each of these loads. Conventional Hall effect sensors will not be able to detect both of these loads. Instead, a low - power Hall effect sensor and a high - power Hall effect sensor will be required. A Hall effect sensor having a graphene conductor can detect the current density of both low - power loads and high - power loads.

[0064] Therefore, it can be used in operations where the Hall effect sensors of the prior art are not applicable.

[0065] In a specific usage scenario, it can be provided as Figure 1 and Figure 2The device for the monitoring unit as shown in the embodiment.

[0066] Figure 1 Figure 100 depicts a device 100 for a monitoring unit 10. The unit 10 has a plurality of current tabs 12 for connection to a circuit. The device 100 includes a plurality of Hall effect sensors 20. The Hall effect sensors 20 are arranged in an array across the surface of the unit 10. The array forms a series of measurement positions on the surface of the unit 10. The unit 10 may be disposed in a bag, and the Hall effect sensors 20 may be disposed inside or outside the bag. Specifically, the array may be selected such that the perimeter defined by the array defines an area greater than 80% of the surface area of the unit 10 being measured. The array may define a regularly repeating pattern, or may have any other pattern selected to fit a particular unit 10. The array may be evenly distributed over the surface of the unit 10.

[0067] In use, a current (or voltage) is applied to each Hall effect sensor 20. Then, a load is applied to the unit 10. The load may be a charging or discharging load. As a result of the load, a magnetic field is generated by the unit 10. Then, each Hall effect sensor 20 will detect the magnetic field in the portion of the unit 10 aligned with it. The magnetic field is proportional to the local current density. Thus, a detailed map of the current density of the unit 10 can be formed. Then, this detailed map can be used to monitor the unit 10 and to characterize specific fault modes.

[0068] The array of Hall effect sensors 20 may be disposed on a carrier material or layer. Then, the carrier material may be positioned adjacent to or in contact with the surface of the unit 10 being monitored. Alternatively, the array may be formed substantially integrally with the unit 10 or the housing / casing of the unit 10. Thus, the array can be used to test a single integrated unit 10, or to test a plurality of units 10 in proximity to the array in sequence.

[0069] The array may be selected to measure variations in the current density on the unit 10. For example, in regions where a greater current density is desired, there may be a greater number of array positions. Such regions may be near the current tabs 12 of the unit 10. Thus, the array may include more measurement positions near the current tabs.

[0070] Figure 1AAn example array consistent with this is shown. In this array, the cell 10 is divided into a plurality of regions, three in this example. The current region 10a is defined as being closest to the current tab 12. The end region 10c is defined at the end of the cell 10 opposite the current tab 12. The central region 10b is defined between the current region 10a and the end region 10c. The regions 10a, 10b, 10c may be defined as being evenly distributed over the cell. Alternatively, the regions 10a, 10b, 10c may be defined in any suitable manner.

[0071] The current region 10a may have more Hall effect sensors 20 in the array than the end region 10c and / or the central region 10b. In a particular embodiment, as Figure 1A shown, the current region 10a and the central region 10b may have the same number of Hall effect sensors 20, while the end region may have fewer Hall effect sensors 20.

[0072] In experiments conducted with the Figure 1A arrangement, it has been shown that the current density is greatest closest to the current tab 12, and the measurement results are smaller the farther away from the current tab 12.

[0073] In another embodiment, one or more Hall effect sensors 20 may be placed on each current tab 12. This may be used in any of the arrangements disclosed herein. The difference between the readings of these Hall effect sensors 20 may be monitored to determine the internal resistance of the cell 10. This may be monitored as it changes over time to determine the degradation of the cell 10.

[0074] A plurality of cells 10 may be connected together to form a battery pack. The current tabs 12 of the plurality of cells 10 may be connected together via bus bars in the battery pack. One or more Hall effect sensors 20 may be placed on these bus bars to detect the current flowing therein. This may be used as a safety measure to prevent overcurrent being supplied to the cells 10. This may also be used to measure any changes in current draw of the cells over their lifetime. Such changes may be an indication of degradation of the cells 10.

[0075] Additionally or alternatively, one or more Hall effect sensors 20 may be provided at the input of each cell 10 in the battery pack. This allows detection of changes in current draw for each individual cell 10. Using this information, the current flowing into the battery pack may be optimized for efficient charging and / or discharging and to allow use of the full capacity of the battery pack. If an individual cell 10 in the battery pack fails, it may be identified and the failed cell 10 may be isolated. Thus, this may extend the operating life of the battery pack.

[0076] As Figure 2As shown, an alternative embodiment of the apparatus 100 is provided. In this alternative embodiment, one or more Hall effect sensors 20 are provided that are connected to the track system 30. The track system 30 includes a movable arm 32 mounted on a track 34. The Hall effect sensors 20 are mounted on the track such that they can move with the arm 32 to measure the local current density at any position on the surface of the unit 10. Although Figure 2 a simple linear track system 30 is shown, it is contemplated that any suitable actuation system for the Hall effect sensors 20 that is suitable for moving the Hall effect sensors 20 between multiple positions can also be used.

[0077] The Hall effect sensors 20 can be moved to multiple positions on the surface of the unit 10, and the local current density is measured at each of these positions. For example, the Hall effect sensors 20 can be moved to N different positions on the surface of the unit 10. These positions can be selected such that they jointly define an array. For example, these positions can jointly define Figure 1 the array shown.

[0078] At each of the N positions, the output of the Hall effect sensor 20 can be measured and recorded.

[0079] Components of the apparatus 100 and the unit 10 can be provided. For example, the component can be a battery of a vehicle. In such a component, the apparatus 100 and the unit 10 can be co-located for performing operations as described herein.

[0080] Each apparatus 100 is preferably attached to the unit 10. For example, this can be within the housing of the unit 10. Alternatively, each apparatus 100 can be attached to the housing of the unit 10. In a further alternative, each apparatus 100 can be held in place by a larger outer housing that fixes the unit 10 and the apparatus 100 in place. Thus, any vibration of the unit 10 or the Hall effect sensors 20 will be equally felt by each component to avoid introducing additional errors.

[0081] Each apparatus 100 can be incorporated into a broader battery management system. For example, the battery management system can be an overall battery management system for a vehicle such as an automobile, where the unit 10 supplies power to the vehicle. The output of the Hall effect sensors 20 can be used as an input to the battery management system. The battery management system can additionally include any other sensors for detecting parameters of the unit 10 or parameters related to the unit 10. The battery management system can be configured to control the charging and / or discharging of the unit 10 based on the output of the Hall effect sensors 20.

[0082] The battery management system can be configured to warn the user that the unit 10 is degrading and / or failing based on the output of the Hall effect sensor 20. By making multiple measurements at different locations on the surface of the unit 10 (whether via Figure 1 a fixed array of Hall effect sensors 20 or via Figure 2 a mobile device of the Hall effect sensor 20), the current density on the unit 10 can be mapped. This mapping can be performed by the battery management system. Using this mapping, the exact location where a fault is occurring in the unit 10 can be identified, which can allow the identification of early warning signs. Thus, a partial replacement of the defective components of the unit 10 can be performed.

[0083] Additionally, the Hall effect sensor 20 can be continuously monitored, for example, by the battery management system, to evaluate the change in current as a function of the state of charge of the unit 10. The change in current represents a change in the internal resistance of the unit 10. This information can be used to understand the internal mechanism of the unit 10, which can be used to develop improved units 10 or their management strategies.

[0084] Since the temperature of the unit 10 and the Hall effect sensor 20 can also affect the measured voltage, the battery management system can also include temperature compensation features. Specifically, an increase in the temperature of the Hall effect sensor 20 may increase the generated Hall voltage. This relationship can be linearly correlated or can be represented by a more complex relationship. In any case, a correction factor can be applied to the Hall effect sensor 20 to correct for this temperature dependence.

[0085] One or more temperature sensors can be provided near the Hall effect sensor 20, for example, on the Hall effect sensor 20 or on the unit 10. Then, the sensed temperature can be used to determine an appropriate correction factor, which is then applied to the raw voltage readings from the Hall effect sensor 20. Preferably, the temperature sensor is directly applied to the Hall effect sensor 20 because this directly senses the temperature of the sensor that affects the measurement. In any case, there will be a thermal lag between the temperature sensor and the temperature effect on the Hall effect sensor 20. The correction factor can take this temperature lag into account, for example, by adjusting the correction factor accordingly.

[0086] The sensitivity of the present Hall effect sensor 20 enables the direction of the current to be detected as well. That is, it is possible to detect the difference between the charging current and the discharging current of the unit 10. During charging, the magnetic field strength (in Tesla, T) may increase, while during discharging, the magnetic field strength may decrease (and vice versa). The magnetic field strength may also change sign between charging and discharging (i.e., from a positive value to a negative value, or from a negative value to a positive value). In this sense, the rate of change and / or the sign of the magnetic field strength can be used to indicate the direction of the current flow in the unit 10 (i.e., to determine between charging and discharging). If the Hall voltage reading is temperature-corrected as discussed above, this sensing can be specifically identified. It is possible that only certain positions on the unit 10 show the direction of charging, and it may be necessary for the Hall effect sensor 20 to be positioned in a given direction.

[0087] Accordingly, the present disclosure includes using a Hall effect sensor 20 having a graphene conductor to measure the magnetic field of the unit 10. The local current density of the unit 10 can be derived from this magnetic field.

[0088] The present invention also includes another device 200 for field mapping the unit 10 under load. Figures 3 to 6 This other device 200 is generally shown in various arrangements.

[0089] Figure 3 This other device 200 is shown in its simplest state, and this other device 200 is applied to the unit 10 to form an assembly. The device 200 includes a pick-up coil 52, and the pick-up coil 52 is arranged to cover at least a part of the unit 10 in use. The pick-up coil 52 can be a single-turn coil, or can be a coil with multiple turns (multi-turn coil). The number of turns in the pick-up coil 52 is used to increase or decrease the generated current.

[0090] The pick-up coil 52 is a flux transformer coil, and can integrate the field generated by the movement of charges within the unit 10 to cause a current to flow in the pick-up coil 52. The pick-up coil 52 can be inserted into the unit 10 or the bag, printed inside the unit 10 or the bag, printed on the surface of the unit 20 or the bag, or externally applied to the unit 20 or the bag.

[0091] The pick-up coil 52 is in electrical communication (and / or electrically connected) with the measurement coil 54. Like the pick-up coil 52, the measurement coil 54 is a flux transformer coil, and can be a single-turn or multi-turn coil. The simplest solution is a single-turn coil for each of the pick-up coil 52 and the measurement coil 54, because this means that no electrical crossover is required, otherwise multiple lamination or printing steps would be required during the manufacturing process.

[0092] The pick-up coil 52 and the measurement coil 54 can be designed to reduce or concentrate the magnetic flux generated by the measurement coil. This is typically achieved by varying the size and / or number of turns of each coil. The magnetic flux generated in the measurement coil 54 is proportional to the magnetic flux detected by the pick-up coil. When the coils are designed to concentrate the magnetic flux (i.e., generate a greater magnetic flux in the measurement coil 54), the area of the pick-up coil 52 disposed on the unit surface can be larger than the area of the measurement coil 54 on the magnetic sensor 21, or have more turns. For a given magnetic sensor sensitivity, concentrating the magnetic flux allows for a more sensitive magnetic field measurement.

[0093] As Figure 3 shown in the schematic diagram, this communication can typically be direct. Alternatively, the communication can be via an intermediate component, such as Figure 4 the multiplexer (MUX) 60 shown.

[0094] In use, the magnetic flux in the unit 10 will induce a current in the pick-up coil 52. This induced current is then transmitted from the pick-up coil 52 to the measurement coil 54. This causes a current to pass through the measurement coil 54 and thereby generates a magnetic field.

[0095] The magnetic field sensor 21 is arranged to be aligned with the measurement coil 54. The magnetic field sensor 21 is arranged to detect the magnetic field generated in the measurement coil 54. The magnetic field sensor 21 can be any suitable magnetic field sensor. In some embodiments, the magnetic field sensor 21 can be a Hall effect sensor 20, such as the Hall effect sensor 20 having a graphene conductor as described above.

[0096] In this sense, the magnetic flux of the unit 10 can be detected by the magnetic field sensor 21 via the pick-up coil 52 and the measurement coil 54. Thus, no sensor is placed inside the unit 10 or the bag. Thereby, the number of connections from the outside to the inside of the bag is reduced, which makes the sealing of the bag simpler.

[0097] Figure 3 The simplest arrangement of the device 200 is shown, which will detect the magnetic flux over the entire unit.

[0098] Figure 4 An alternative arrangement of the device 200 is shown. In this device 200, a plurality of pick-up coils 52 are provided at a plurality of positions corresponding to different positions on the unit 10. Unless otherwise explicitly stated, each pick-up coil 52 is generally as described above with respect to Figure 3 . The plurality of pick-up coils 52 can each be in electrical communication with the multiplexer 60. For ease of reference, the connections between each pick-up coil 52 and the multiplexer 60 are omitted from Figure 4 .

[0099] The multiplexer 60 can be arranged to selectively transfer the current induced in one of the plurality of pick-up coils 52 to the measurement coil 54 for reading by the magnetic field sensor 21. Specifically, the multiplexer 60 can cycle through each pick-up coil 52, sequentially transferring the current induced in each pick-up coil 52 to the measurement coil 54.

[0100] Alternatively, as described below with respect to Figure 6 each pick-up coil 52 can be in electrical communication with its own measurement coil 54. Then, each measurement coil can be measured by the corresponding magnetic field sensor 21.

[0101] Combinations of these arrangements are also possible, where the plurality of pick-up coils 52 are divided into a plurality of subgroups. Each subgroup of pick-up coils 52 can be in electrical communication with a multiplexer 60, where a measurement coil 54 and a magnetic field sensor 21 are provided for each multiplexer.

[0102] The pick-up coils 52 can be arranged in a regular array, as Figure 4 shown. As discussed above, the array can be evenly distributed on the surface of the unit 10 to allow generation of the complete profile of the unit 10. The array can, for example, place the pick-up coils 52 at locations where a failure or degradation of the unit 100 is expected.

[0103] Figure 5 Shows a Figure 4 modified version of the arrangement, which also includes a main pick-up coil 52. Unless otherwise explicitly stated, the main pick-up coil 52 is generally the same as the pick-up coils 52 previously discussed. The main pick-up coil 52m surrounds the plurality of pick-up coils 52. Specifically, the main pick-up coil 52m can surround every other pick-up coil 52 provided on the unit 10. The main pick-up coil 52 can generally correspond to the outer periphery of the unit 10, for example by surrounding the entire outer periphery and offsetting from the outer periphery of the unit 10 by a constant amount.

[0104] Figure 6 Shows another arrangement of the device 200. In this device 200, the plurality of pick-up coils 52 includes one or more nested pick-up coils 52. The nested pick-up coils 52 overlap with another pick-up coil 52 among the plurality of pick-up coils 52. As Figure 6 can be seen, the degree of overlap can be relatively small, for example between adjacent pick-up coils 52. The main pick-up coil 52m is actually in the form of a nested coil because it overlaps with all other pick-up coils 52.

[0105] In Figure 6 the arrangement, each pick-up coil 52 is in electrical communication with its own corresponding measurement coil 54. Similarly, for ease of reference, from Figure 6The connection between the pick-up coil 52 and the corresponding measurement coil 54 is omitted. Of course, Figure 6 the nested coil 52 arrangement of Figure 6 can be used in conjunction with an arrangement including a multiplexer 60 between the pick-up coil and one or more measurement coils 54.

[0106] Using these nested coils 52 means that any background DC field can be removed from the pick-up coil 52 readings. This is achieved in particular by using the main pick-up coil 52m. For example, this can allow the removal of the background effect of the Earth's magnetic field or any effects caused by the local environment. Thus, a certain degree of compensation is achieved.

[0107] The pick-up coil 52 can be arranged and / or nested in many different ways to provide the required spatial resolution or compensation. The arrangement can also be selected to achieve a cost-effective arrangement that provides sufficient spatial resolution and compensation for a given use.

[0108] Components of the device 200 can be provided in combination with the unit 10. Specifically, the pick-up coil 52 can be arranged to be attached to the unit 10, for example, inside the unit bag. When a measurement is required, external components such as the multiplexer 60, the measurement coil 54, etc. can be selectively attached to the unit 10. Alternatively, this attachment can be permanent. In this sense, an integrated measurable unit 10 is provided. When the unit 10 is an automotive battery, this component or Figures 3 to 6 any arrangement of Figures 3 to 6 may be particularly useful.

[0109] Figures 3 to 6 Any device 200 of Figures 3 to 6 can be connected as an input to the battery management system and used in its control structure in the same manner as described above for the device 100 of Figure 1 and Figure 2 Figure 2 .

[0110] In another embodiment, a Hall effect sensor 20 having a graphene conductor can be used to measure the input current and / or output current of the unit 10, as Figure 7 shown.

[0111] The unit 10 is connected to supply power to a load 40. The load 40 can be any one or more elements that draw power from the unit 10. For example, the load 40 can be an electronic system of a vehicle, and the unit 10 can be an automotive battery. In an existing technology system, a shunt resistor is arranged in series with the load 40. Depending on whether the input current or the output current of the unit 10 is to be measured, the shunt resistor can be arranged on either side of the load 40. A voltage drop reading is taken across the shunt resistor, and the current is calculated according to Ohm's law. Since the shunt resistor is arranged in series with the load 40, if the shunt resistor fails, this will affect or inhibit the flow of current through the load 40.

[0112] In the present disclosure, the shunt resistor is removed. Instead, one or more Hall effect sensors 20 are provided on the input line and / or output line of the cell 10. These Hall effect sensors 20 include the graphene conductor as described above. While Figure 3 Hall effect sensors 20 are shown on both the input and output lines of the cell 10, this is not necessary. Instead, a single Hall effect sensor 20 can be provided on either the input or output line of the cell 10.

[0113] Such Hall effect sensors 20 with graphene conductors will provide greater resolution than shunt resistors. Additionally, these Hall effect sensors 20 require low power draw and will therefore not significantly affect the total power draw of the battery management system.

[0114] Accordingly, the present disclosure relates to using Hall effect sensors 20 with graphene conductors to measure the input current and / or output current of the cell 10.

[0115] While the present disclosure focuses on the cell 10, it should be noted that the technology and apparatus are equally applicable to fuel cells, capacitors, batteries, battery packs, etc.

[0116] While the present disclosure discusses general graphene Hall effect sensors 20, it has been recognized that the performance of the Hall effect sensors 20 can be greatly improved by using graphene manufactured according to the disclosure of UK Patent Application No. 2020131.5, the entire content of which is incorporated herein by reference.

[0117] Such Hall effect sensors include a graphene conductor and a dielectric material layer thereon, which are patterned simultaneously such that only the outer edges of the graphene sheets are exposed during manufacturing. The graphene conductor can be a graphene sheet (single layer) or a graphene layer structure formed by 1 to 10 graphene sheets. Thus, the graphene and the dielectric layer share a continuous outer edge surface. The dielectric layer can be, for example, silicon dioxide, hafnium oxide, or aluminum oxide formed by evaporation or atomic layer deposition (ALD), preferably aluminum oxide. Then ohmic contacts are deposited and thus only contact the outer edge surface of the graphene sheet, which has been found to provide significantly improved current injection into the graphene (relative to ohmic contacts on the surface of the graphene). The edge ohmic contacts also minimize the contact area with the graphene sheet, thereby minimizing any unwanted doping from typically metal contacts (such as one or more of titanium, aluminum, chromium, and gold), which would otherwise limit the sensor sensitivity.

[0118] Although the dielectric layer provides substantial protection against atmospheric contamination as it coats the entire graphene surface, the Hall effect sensor may also include a continuous anti-air coating extending through the coated graphene such that at least the remaining continuous outer edge surface is coated. This fully encapsulates the graphene and protects it from atmospheric contamination. The continuous anti-air coating may also preferably be alumina or hafnium oxide formed by evaporation or ALD. ALD is preferred as this provides a conformal coating across the substrate, thus providing a more effective anti-air coating. Alumina or hafnium oxide can be patterned by evaporation, but there is a risk that some edges of the graphene remain exposed due to shadowing in the directionality of this method. However, patterning allows the ohmic contacts to remain exposed and the dicing of the substrate to remain uncoated such that the dicing of the substrate may be performed at the risk of damaging the coating. The Hall effect sensor can be integrated into a circuit using conventional wire bonding or solder bumps to the ohmic contacts. In the case of forming the coating by ALD, it may be necessary to pierce the coating to reach the ohmic contacts for wire bonding, which poses a risk of damaging or cracking the coating. In an alternative embodiment, the patterned graphene and dielectric layer are coated with an anti-air coating before any ohmic contacts are deposited. The coating can be selectively etched to expose portions of the graphene edges, whereby ohmic contacts can be deposited in the etched portions to contact the graphene edge surfaces. However, there is greater complexity in depositing the ohmic contacts within the selectively etched portions.

[0119] Thus, the Hall effect sensor may include:

[0120] a substrate having a layer structure thereon, the layer structure including:

[0121] a lower layer on a first region of the substrate, wherein the lower layer includes one or more graphene layers extending through the lower layer, and

[0122] an upper layer on the lower layer, and the upper layer is formed of a dielectric material,

[0123] wherein the graphene and the upper layer are cross-shaped and share a continuous outer edge surface, ohmic contacts, which are provided on another region of the substrate and are in direct contact with one or more graphene layers via the continuous outer edge surface, and

[0124] four ohmic contacts, each contact provided on another region of the substrate and in direct contact with the distal portion of the edge surface of each of the four arms of the cross, and

[0125] a continuous anti-air coating that surrounds the layer structure or spans the substrate, the layer structure, and at least one ohmic contact.

[0126] The cross arms mean the four projecting portions forming the cross.

[0127] The substrate can be sapphire, silicon, silicon dioxide, silicon nitride, silicon carbide, germanium, or a III-V semiconductor, preferably sapphire or silicon.

[0128] Preferably, the Hall effect sensor includes:

[0129] A sapphire substrate having a layer structure thereon, the layer structure including:

[0130] A single layer of graphene on a first region of the sapphire substrate, and

[0131] An alumina layer on the single layer of graphene,

[0132] wherein the graphene and the alumina are cross-shaped and share a continuous outer edge surface,

[0133] Four gold ohmic contacts, each contact disposed on another region of the sapphire substrate and in direct contact with a distal portion of the edge surface of each of the four arms of the cross, and

[0134] A continuous alumina coating that surrounds the layer structure.

[0135] The protective coating provided by the method disclosed in UK Patent Application No. 2020131.5 provides excellent protection against atmospheric pollution for the graphene of the graphene Hall effect sensor, thereby improving the stability of the device performance over a longer period of time compared to other known Hall effect sensors, thus extending the device life and minimizing any need to recalibrate the device. This Hall effect sensor produces an immediate sensor response that allows real-time monitoring of the current density on the unit 10.

[0136] It has further been recognized that for any of the Hall effect sensors 20 discussed above, the reliability of the measurement can be increased by incorporating a rotating current modulation technique. A suitable technique is discussed in Mosser et al., "A Spinning Current Circuit for Hall Measurements Down to the Nanotesla Range". This allows for the dynamic cancellation of offsets and low-frequency noise by rapidly and periodically swapping the bias and sense terminals of the Hall effect sensor. This can be used in combination with any of the arrangements and embodiments discussed above.

Claims

1. A method for field mapping of a unit under load, comprising the following steps: Providing a unit; Providing a Hall effect sensor, the Hall effect sensor comprising a graphene conductor for measuring a magnetic field; Positioning the Hall effect sensor at a first position adjacent to a surface of the unit; Applying a load to the unit; And Measuring an output of the Hall effect sensor to detect a magnetic field generated by the unit in a portion of the unit aligned with the first position, Wherein the Hall effect sensor comprises: A substrate having a layer structure thereon, the layer structure comprising: A lower layer on a first region of the substrate, wherein the lower layer comprises one or more graphene layers extending through the lower layer, and An upper layer on the lower layer, and the upper layer is formed of a dielectric material, Wherein the graphene and the upper layer share a continuous outer edge surface, Ohmic contacts, which are provided on another region of the substrate and are in direct contact with the one or more graphene layers via the continuous outer edge surface, and A continuous anti-air coating that surrounds the layer structure or spans the substrate, the layer structure, and the at least one ohmic contact.

2. The method according to claim 1, further comprising the following steps: Moving the Hall effect sensor from the first position to a second position adjacent to a surface of the unit; Measuring an output of the Hall effect sensor at the second position to detect a magnetic field generated by the unit in a portion of the unit aligned with the second position.

3. The method according to claim 2, further comprising the following steps: Moving the Hall effect sensor from the second position to a series of N subsequent positions adjacent to a surface of the unit; And Measuring an output of the Hall effect sensor at each of the subsequent positions to detect a magnetic field generated by the unit in a portion of the unit aligned with the subsequent position, Wherein the N subsequent positions are distributed on a surface of the unit.

4. The method according to claim 3, wherein, The N subsequent positions form an array on a surface of the unit.

5. The method according to claim 1 or 2, wherein The Hall effect sensor is part of a Hall effect sensor array, and each of the Hall effect sensors is placed adjacent to the unit to detect a magnetic field generated by a corresponding portion of the unit aligned with the Hall effect sensor.

6. The method according to any one of claims 1 to 5, further comprising the following steps: Monitoring the measured output of the Hall effect sensor; Identifying a change in the magnetic field indicating a unit failure; And Determining a location of the unit failure in the unit.

7. A device for field mapping of a unit under load, comprising a Hall effect sensor array, each Hall effect sensor comprising: A graphene conductor for measuring a magnetic field in a corresponding portion of the unit aligned with the Hall effect sensor during use; A substrate having a layer structure thereon, the layer structure comprising: A lower layer on a first region of the substrate, wherein the lower layer comprises one or more graphene layers extending through the lower layer, and An upper layer on the lower layer, and the upper layer is formed of a dielectric material, wherein the graphene and the upper layer share a continuous outer edge surface, an ohmic contact, which is disposed on another region of the substrate and is in direct contact with the one or more graphene layers via the continuous outer edge surface; and a continuous anti-air coating, which surrounds the layer structure or spans the substrate, the layer structure, and the at least one ohmic contact.

8. A device for field mapping of a cell under load, comprising a Hall effect sensor mounted on an actuation system configured to move the Hall effect sensor between a plurality of positions corresponding to positions on the cell, each Hall effect sensor comprising: a graphene conductor for measuring a magnetic field in a corresponding portion of the cell aligned with the Hall effect sensor in use; a substrate having a layer structure thereon, the layer structure comprising: a lower layer on a first region of the substrate, wherein the lower layer includes one or more graphene layers extending through the lower layer, and an upper layer on the lower layer, and the upper layer is formed of a dielectric material, wherein the graphene and the upper layer share a continuous outer edge surface, an ohmic contact, which is disposed on another region of the substrate and is in direct contact with the one or more graphene layers via the continuous outer edge surface; and a continuous anti-air coating, which surrounds the layer structure or spans the substrate, the layer structure, and the at least one ohmic contact.

9. A component comprising the device and the cell according to any one of claims 7 to 8.

10. The component according to claim 9, further comprising a battery management system arranged to receive the output of each Hall effect sensor as an input.

11. The component according to claim 10, wherein, The battery management system is configured to generate a map of the local current density of the cell based on the output of each Hall effect sensor.

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