GB2577088A

GB2577088A - Battery management

Info

Publication number: GB2577088A
Application number: GB1814886.6A
Authority: GB
Inventors: Locke Jacob; Amigues Adrien; Cooke Ashley; O'Neill Laura; Slosarcsyk Krzysztof
Original assignee: Oxis Energy Ltd
Current assignee: Oxis Energy Ltd
Priority date: 2018-09-13
Filing date: 2018-09-13
Publication date: 2020-03-18
Also published as: WO2020053585A1; GB201814886D0

Abstract

A temperature management system 103 for a battery 101 comprises a heat transfer device 104 and a controller 102. The heat transfer device is operable to apply heating and/or cooling to the battery. The controller is configured to control the heat transfer device to apply heating and/or cooling to the battery in order to change the temperature of the battery towards a target temperature, and to vary the target temperature during charging and/or discharging of the battery. This ensures optimum performance of the battery at different stages of the charge-discharge cycle, and is particularly useful for Li-S batteries. Preferably, the controller is configured to increase the target temperature during battery discharge, and to decrease the target temperature during battery charging. The controller may also vary the target temperature according to measurements relating to the state of charge of the battery, e.g. by measuring its voltage such as rate of change of the voltage. The heat transfer device may also be controlled in response to measurements taken from a temperature measurement device 106.

Description

(54) Title of the Invention: Battery management

Abstract Title: Temperature management system for battery (57) A temperature management system 103 for a battery 101 comprises a heat transfer device 104 and a controller 102. The heat transfer device is operable to apply heating and/or cooling to the battery. The controller is configured to control the heat transfer device to apply heating and/or cooling to the battery in order to change the temperature of the battery towards a target temperature, and to vary the target temperature during charging and/or discharging of the battery. This ensures optimum performance of the battery at different stages of the charge-discharge cycle, and is particularly useful for Li-S batteries. Preferably, the controller is configured to increase the target temperature during battery discharge, and to decrease the target temperature during battery charging. The controller may also vary the target temperature according to measurements relating to the state of charge of the battery, e.g. by measuring its voltage such as rate of change of the voltage. The heat transfer device may also be controlled in response to measurements taken from a temperature measurement device 106.

Figure 1

1/3

Figure 1

109

Figure 2

Voyage (V)

2/3

Charge

Figure 3

402*403|₍ 404 |

2$

JO s

i)

500 1008 tsa© 20δ© 2SOO

Cs^scfiy/ mA h g ^! (5)

Discharge

Charge

Figure 4

3/3

3.00 403 600 80S 10® 12®

Capacity / mA h g * (S|

Figure 5

Voltage / V Voltage / V

502 (BB;·...................................... | s -m w io® nos

Capacity / mA h g ^s (S)

Figure 6

Battery Management

FIELD OF THE INVENTION [0001] The present disclosure relates to apparatus and methods for use in controlling a temperature of a battery comprising at least one battery cell. The apparatus and methods may find particular, but not exclusive, application in the field of batteries comprising a lithium sulphur battery cell.

BACKGROUND [0002] Rechargeable batteries typically include a plurality of rechargeable battery cells which are designed to undergo successive charge-discharge cycles. The use of such rechargeable batteries, for the purposes of charging them with stored electrochemical energy for later discharge and use, is gaining increasing importance in a range of applications. Such applications may, for example, include automotive, marine, aerospace and other vehicle applications, domestic and uninterruptable energy supplies, and storage of energy produced from intermittent and renewable electricity sources for demand and load levelling in domestic and grid-tied power networks.

[0003] A typical battery cell comprises an anode, a cathode and an electrolyte disposed between the anode and cathode. The anode, cathode and electrolyte may be contained within a housing, for example, a pouch. Electrical connectors, for example, connector tabs may be coupled to the housing to provide electrical connection with the anode and cathode of the cell.

[0004] A particular type of battery which is contemplated herein is a battery comprising at least one lithium sulphur (Li-S) battery cell. Lithium sulphur is a next generation cell chemistry that, having a theoretical energy density 5 times greater than, for example, lithium ion, may better serve as an electrochemical energy store for a range of applications. A typical lithiumsulphur cell comprises an anode formed from lithium metal or a lithium metal alloy, and a cathode formed from elemental sulphur or other electroactive sulphur material. The sulphur or other electroactive sulphur-containing material may be mixed with an electrically conductive material, such as carbon, to improve its electrical conductivity.

[0005] For at least some battery types the performance of the battery (e.g. during charging and/or discharging of the battery) may be dependent on the temperature of the battery during operation. For example, there may be a temperature range in which optimal performance of the battery is realised. Outside of this temperature range, performance of the battery may be degraded and/or operation of the battery may cause damage to the battery, leading to future performance degradation. In some applications of a battery, the temperature of the battery may therefore be controlled in order to ensure that the battery is operated within a desirable temperature range.

[0006] This may be particularly applicable, for example, when a battery is operated in conditions during which it is exposed to high or low temperatures. For example, one application of a battery which is contemplated herein is as a power source in an aircraft. For example, a battery may be incorporated into an aircraft and used as a power source for propelling the aircraft and/or as a power source for auxiliary systems on the aircraft. One example of an aircraft which may be at least partially powered by a battery is an unmanned aerial vehicle (UAV).

[0007] Aircraft are typically exposed to low ambient temperatures (e.g. temperatures as low as or even lower than 50°C) when flying at altitude and thus there is potential for a battery in an aircraft to be operated at temperatures at which performance of the battery may be degraded and/or operation of the battery may cause damage to the battery. In such applications, a battery may be subjected to heating in order to avoid operation of the battery at low temperatures.

[0008] In the same or other applications, a battery may be subjected to cooling in order to reduce the temperature at which the battery operates.

[0009] It is in this context that the subject matter contained in the present application has been devised.

SUMMARY OF THE INVENTION [0010] As was explained above, in some scenarios it may be desirable to provide heating and/or cooling to a battery, in order to ensure that the battery operates within a given temperature range. For example, active heating may be provided to a battery in order to allow operation of the battery in low temperature conditions (such as on an aircraft flying at altitude). Additionally or alternatively, active cooling may be provided to a battery in order to reduce the temperature of the battery. Typically, heating and/or cooling may be provided to a battery such that the temperature of the battery remains relatively constant, or at least within a given temperature range, throughout charging and/or discharging of the battery.

[0011] It has been found that for at least some batteries, a temperature at which optimum performance of the battery occurs may be different during different portions of a charge/discharge cycle of a battery. Examples are therefore contemplated herein in which the temperature of a battery is controlled so as to vary the temperature of the battery during charging and/or discharging of the battery.

[0012] According to a first aspect of the present disclosure there is provided a temperature management system for a battery, the temperature management system comprising: a heat transfer device operable to apply heating and/or cooling to the battery; a controller configured to control the heat transfer device to apply heating and/or cooling to the battery in order to change the temperature of the battery towards a target temperature, wherein the controller is further configured to vary the target temperature during charging and/or discharging of the battery.

[0013] The target temperature may represent a temperature at which it is desirable to operate the battery during charging and/or discharging. As was explained above, it has been found that a temperature at which advantageous performance characteristics of a battery occur may be different during different portions of a charge/discharge cycle of a battery. For example, advantageous performance characteristics of a battery may occur at a first temperature during a first portion of a charge/discharge cycle of a battery and may occur at a second temperature (different to the first temperature) during a second portion of a charge/discharge cycle. By providing a controller which varies the target temperature during charging and/or discharging, the temperature of the battery may be varied during charging and/or discharging, so as to bring about advantageous performance characteristics at different portions of a charge/discharge cycle of the battery.

[0014] Varying the target temperature during charging and/or discharging may additionally or alternatively allow an amount of energy used to heat and/or cool the battery to be reduced. For example, if a constant target temperature were to be used throughout a charge and/or discharge cycle carried out under low ambient temperature conditions (e.g. on an aircraft flying at altitude), heating may be applied to the battery throughout a charge and/or discharge cycle in order to maintain the temperature of the battery at or near to the constant target temperature.

[0015] However, it has been found that during at least part of a charge cycle and/or discharge cycle, a battery may be operated at a lower temperature (than a constant charging temperature which might be chosen for the entirety of a charge and/discharge cycle) without significantly degrading the performance of the battery. Moreover, in at least some examples, it has been found that charging and/or discharging a battery at a lower temperature (than a constant charging temperature which might be chosen for the entirety of a charge and/discharge cycle) for at least part of a charge and/discharge cycle may be preferable and may improve the performance of the battery. By varying the target temperature during charging and/or discharging, an amount of heating which is provided to the battery may therefore be reduced and the temperature of the battery may be allowed to fall (relative to a constant charging temperature which might be chosen for the entirety of a charge and/discharge cycle). The amount of energy used to heat the battery during a charge and/or discharge cycle may therefore be reduced and the efficiency with which the temperature of the battery is controlled may be increased.

[0016] Controlling the heat transfer device to apply heating and/or cooling to the battery in order to change the temperature of the battery towards a target temperature may, for example, comprise maintaining the temperature of the battery substantially at or near to the target temperature once the target temperature has been reached.

[0017] Varying the target temperature during charging and/or discharging of the battery may, for example, comprise maintaining a first constant target temperature for a first portion of a charge and/or discharge cycle and switching the target temperature to a second constant target temperature for a second portion of a charge/discharge cycle. That is, varying the target temperature may comprise making one or more step changes between two or more different target temperatures during charging and/or discharging. Alternatively, the target temperature may be varied in a continuous manner for at least part of a charge and/or discharge cycle. For example, the target temperature may be gradually increased or decreased during at least a portion of a charge and/or discharge cycle.

[0018] The controller may be further configured to increase the target temperature during discharge of the battery.

[0019] For at least some batteries it has been found that a first portion of a discharge cycle of a battery can be carried out at a lower temperature than a second portion of the discharge cycle, where the first portion occurs before the second portion during discharge of the battery. For example, during the first portion of the discharge cycle, acceptable performance may be achieved over a relatively wide range of temperatures. During the first portion of the discharge cycle the temperature of the battery may be allowed to drop to a first temperature, which is relatively low in the range of temperatures, without substantially degrading battery performance. Operating the battery at the first, relatively low, temperature may conserve energy which might otherwise be used to heat the battery to a higher temperature.

[0020] During the second portion of the discharge cycle the performance of the battery may be substantially improved by increasing the temperature of the battery to a temperature which is greater than the first temperature. The target temperature may therefore be increased during discharge of the cycle in order to improve the performance of the battery.

[0021] In some examples, the target temperature may be set to a first target temperature during a first portion of the discharge cycle and may be changed to a second target temperature, which is greater than the first target temperature, for a second portion of the discharge cycle. In some examples, the target temperature may be changed between more than two different target temperatures during discharge. In some examples, the target temperature may be gradually and/or continuously varied during at least a portion of a discharge cycle of the battery.

[0022] The controller may be further configured to decrease the target temperature during charging of the battery.

[0023] For at least some batteries it has been found that a second portion of a charge cycle of a battery can be carried out at a lower temperature than a first portion of the charge cycle, where the first portion occurs before the second portion during charging of the battery. For example, during the second portion of the charge cycle, acceptable performance may be achieved over a relatively wide range of temperatures. During the second portion of the charge cycle the temperature of the battery may be allowed to drop to a second temperature, which is relatively low in the range of temperatures, without substantially degrading battery performance. Operating the battery at the second, relatively low, temperature may conserve energy which might otherwise be used to heat the battery to a higher temperature.

[0024] During the first portion of the charge cycle the performance of the battery may be substantially improved by setting the temperature of the battery to a temperature which is greater than the second temperature. The target temperature may therefore be decreased during charging of the cycle in order to improve the performance of the battery and to conserve energy used to heat the battery.

[0025] In some examples, the target temperature may be set to a first target temperature during a first portion of the charge cycle and may be changed to a second target temperature, which is lower than the first target temperature, for a second portion of the charge cycle. In some examples, the target temperature may be changed between more than two different target temperatures during charging. In some examples, the target temperature may be gradually and/or continuously varied during at least a portion of a charge cycle of the battery.

[0026] The controller may be further configured to vary the target temperature in dependence on one or more properties indicative of the state of charge of the battery.

[0027] As has been alluded to above, it may be desirable to vary the target temperature such that the target temperature is different during different portions of a charge and/or a discharge cycle. A time at which to change the target temperature during charge and/or discharge may be determined in dependence on at least one property which is indicative of the state of charge of the battery. For example, it may be desirable to change the target temperature once a given state of charge or equivalently discharge is reached during a charge and/or discharge cycle. The target temperature may therefore be varied according to at least one property which is at least indicative of the state of charge of the battery.

[0028] The one or more properties indicative of the state of charge of the battery may comprise a voltage of the battery.

[0029] In some examples, the target temperature may be varied when the voltage of the battery reaches a threshold voltage during charge and/or discharge. For example, during the discharge of the battery, the target temperature may be varied when the voltage of the battery decreases to a first threshold voltage. Additionally or alternatively, during charge of the battery, the target temperature may be varied when the voltage of the battery increases to a second threshold voltage.

[0030] In some examples, the target temperature may be varied gradually and/or continuously in dependence on changes in the voltage of the battery.

[0031] The one or more properties indicative of the state of charge of the battery may comprise a rate of change of a voltage of the battery.

[0032] In some examples, a rate of change of the voltage of the battery may be indicative of a given stage of charge or discharge having been reached. The rate of change of voltage may be a rate of change with respect to time. Alternatively, the rate of change of voltage may be with respect to another factor which changes during charge and/or discharge. For example, the rate of change of voltage may be with respect to a capacity of the battery and/or an amount of charge which has been provided to or discharged from the battery.

[0033] In some examples, a rate of change of the voltage of the battery may undergo some significant changes during charge and/or discharge of the battery. Points at which the rate of change of voltage undergoes a relatively large change may be indicative of a change of reaction state occurring in the battery. For example, one or more of a change in reaction mechanism occurring in the battery, a change in reaction rate occurring in the battery and/or physio-chemical processes such as precipitation and/or dissolution occurring in the battery, may bring about a change in the rate of change of voltage of the battery. An optimal temperature or temperature range under which a battery may be charged or discharged may vary with variations in a reaction state in the battery. Since a change in the rate of change of the voltage of the battery may be indicative of a change in reaction state, it may also be indicative of a change in an optimal temperature and/or temperature range under which a battery may be charged or discharged. In at least some examples, the target temperature may therefore be varied in dependence on the rate of change of voltage of the cell.

[0034] The controller may be configured to vary the target temperature in dependence on the rate of change of the voltage of the battery undergoing a transition between a period in which the voltage of the battery monotonically increases or decreases during charging or discharging and a period in which the voltage remaining substantially constant during charging or discharging.

[0035] As was alluded to above, in at least some batteries, a rate of change of the voltage of the battery may undergo some significant changes during charge and/or discharge of the battery For example, the voltage of the battery may remain relatively constant (and therefore the rate of change of the voltage is relatively low or substantially zero) during at least one portion of a charge and/or discharge cycle and may monotonically increase or decrease during at least one other portion of a charge and/or discharge cycle. In at least some examples, the target temperature may be varied in dependence on observing a transition in the rate of change of voltage between two portions.

[0036] The one or more properties indicative of the state of charge of the battery may comprise an amount of charge discharged or charged to or from the battery.

[0037] In some examples, an amount of charge which is discharged from and/or provided to the battery may be monitored. For example, a current flowing through the battery may be measured and integrated over time to determine an amount of charge which is discharged from and/or provided to the battery. Such measurements may be referred to as coulomb counting. The target temperature may be controlled in dependence on an amount of charge which is discharged from and/or provided to the battery. For example, the target temperature may be charged when a threshold amount of charge has been discharged from the battery during discharged. Additionally or alternatively, the target temperature may be changed when a threshold amount of charge has been provided to the battery during charging.

[0038] The heat transfer device may comprise at least one component operable to apply active heating to the battery.

[0039] The heat transfer device may, for example, comprise at least one heating element (such as a heating plate) thermally coupled to the battery. Additionally or alternatively, the heat transfer device may comprise one or more conduits through which a heat transfer fluid may be forced to pass, where the one or more conduits are thermally coupled to the battery. The heat transfer device may further comprise at least one heating element arranged to heat the heat transfer fluid passing through the one or more conduits. The battery may therefore be heated by active heating of the heat transfer fluid. In at least some examples, the battery may be arranged in a chamber and the heat transfer device may be arranged to heat the chamber so as to increase the ambient temperature in the chamber.

[0040] The controller may be configured to turn off the active heating of the battery during at least a portion of a charging or discharging cycle of the battery.

[0041] In at least some examples, the temperature of the battery may be controlled by turning on and off active heating of the battery at different times. For example, in a situation in which the target temperature is greater than a current temperature of the battery, active heating of the battery may be turned on in order to increase the temperature of the battery towards the target temperature. In a situation in which the target temperature is lower than a current temperature of the battery, active heating of the battery may be turned off in order to allow the temperature of the battery to decrease towards the target temperature.

[0042] The heat transfer device may comprise at least one component operable to apply active cooling to the battery.

[0043] The heat transfer device may, for example, comprise at least one cooling element (such as a cooling plate) thermally coupled to the battery. Additionally or alternatively, the heat transfer device may comprise one or more conduits through which a heat transfer fluid may be forced to pass, where the one or more conduits are thermally coupled to the battery. The heat transfer device may further comprise at least one cooling element arranged to cool the heat transfer fluid passing through the one or more conduits. The battery may therefore be cooled by active cooling of the heat transfer fluid. In at least some examples, the battery may be arranged in a chamber and the heat transfer device may be arranged to cool the chamber so as to reduce the ambient temperature in the chamber.

[0044] The controller may be configured to turn off the active cooling of the battery during at least a portion of a charging or discharging cycle of the battery.

[0045] In at least some examples, the temperature of the battery may be controlled by turning on and off active cooling of the battery at different times. For example, in a situation in which the target temperature is lower than a current temperature of the battery, active cooling of the battery may be turned on in order to reduce the temperature of the battery towards the target temperature. In a situation in which the target temperature is greater than a current temperature of the battery, active cooling of the battery may be turned off in order to allow the temperature of the battery to increase towards the target temperature.

[0046] The temperature management system may further comprise a temperature measurement device arranged to measure a temperature indicative of the temperature of the battery. The controller may be configured to control the heat transfer device in dependence on the temperature measurements.

[0047] In some examples, the temperature of the battery may be controlled using feedback in the form of at least one measurement of a temperature which is at least indicative of the temperature of the battery. In other examples, the temperature of the battery may be controlled in dependence on a known or predicted temperature response of the battery. For example, active temperature measurements may not be necessary since a temperature response of the battery to heating and/or cooling applied to the battery may be known or may be modelled or predicted.

[0048] The temperature management system may be configured to control the temperature of a battery comprising at least one lithium sulphur battery cell.

[0049] According to a second aspect of the present disclosure there is provided a battery system comprising a battery and a temperature management system of any preceding claim, wherein the temperature management system is configured to control the temperature of the battery.

[0050] The battery may comprise at least one lithium sulphur battery cell.

[0051] According to a third aspect of the present disclosure there is provided a method of managing the temperature of a battery, the method comprising: controlling a heat transfer device to apply heating and/or cooling to the battery in order to change the temperature of the battery towards a target temperature; and varying the target temperature during charging and/or discharging of the battery.

[0052] Varying the target temperature during charging and/or discharging of the battery may comprise increasing the target temperature during discharge of the battery.

[0053] Varying the target temperature during charging and/or discharging of the battery may comprise decreasing the target temperature during charging of the battery.

[0054] Varying the target temperature during charging and/or discharging of the battery may comprise varying the target temperature in dependence on one or more properties indicative of the state of charge of the battery.

[0055] The one or more properties indicative of the state of charge of the battery may comprise a voltage of the battery.

[0056] The one or more properties indicative of the state of charge of the battery may comprise a rate of change of a voltage of the battery.

[0057] Varying the target temperature during charging and/or discharging of the battery may comprise varying the target temperature in dependence on the rate of change of the voltage of the battery undergoing a transition between a period in which the voltage of the battery monotonically increases or decreases during charging or discharging and a period in which the voltage remaining substantially constant during charging or discharging.

[0058] The one or more properties indicative of the state of charge of the battery may comprise an amount of charge discharged or charged to or from the battery.

[0059] The heat transfer device may comprise at least one component operable to apply active heating to the battery.

[0060] Controlling the heat transfer device may comprise turning off the active heating of the battery during at least a portion of a charging or discharging cycle of the battery.

[0061] The heat transfer device may comprise at least one component operable to apply active cooling to the battery.

[0062] Controlling the heat transfer device may comprise turning off the active cooling of the battery during at least a portion of a charging or discharging cycle of the battery.

[0063] The method may further comprise measuring a temperature indicative of the temperature of the battery, and wherein the controlling the heat transfer device comprises controlling the heat transfer device in dependence on the temperature measurements.

[0064] The battery may comprise at least one lithium sulphur battery cell.

[0065] According to a fourth aspect of the present disclosure there is provided software which, when executed by a processer, is arranged to perform a method according to the third aspect. The software may be stored on a computer readable medium. The computer readable medium may comprise a non-transitory computer readable medium.

[0066] Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all examples and/or features of any example can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF FIGURES [0067] One or more embodiments of the invention are shown schematically, by way of example only, in the accompanying drawings, in which:

Figure 1 is a schematic illustration of an example of a battery including a temperature management system;

Figure 2 is a schematic illustration of an example of a battery including a temperature management system and a battery monitoring device;

Figure 3 is a schematic representation of the voltage of a Lithium Sulphur battery during discharge and charge at different temperatures;

Figure 4 is a schematic representation of the voltage of a Lithium Sulphur battery during discharge and charge during which a target temperature of the battery is varied;

Figure 5 is a schematic representation of the voltage of a Lithium Sulphur battery during discharge when subjected to different temperature control regimes; and

Figure 6 is a schematic representation of the voltage of a Lithium Sulphur battery during charging when subjected to different temperature control regimes.

DETAILED DESCRIPTION [0068] Before particular examples of the present invention are described, it is to be understood that the present disclosure is not limited to the particular battery management apparatus, battery or method described herein. It is also to be understood that the terminology used herein is used for describing particular examples only and is not intended to limit the scope of the claims.

[0069] In describing and claiming the battery management apparatus, batteries and methods of the present invention, the following terminology will be used: the singular forms a, an, and the include plural forms unless the context clearly dictates otherwise. Thus, for example, reference to a battery cell includes reference to one or more of such elements.

[0070] Figure 1 is a schematic illustration of an example of a battery 100 according to the present disclosure. The battery 100 comprises a battery cell 101 and a temperature management system 103. The temperature management system 103 includes a heat transfer device 104 and a controller 102. The controller may, for example, comprise one or more processors and/or analogue control electronics. Optionally, and as shown in the example depicted in Figure 1, the temperature management system may further include a temperature measurement device 106.

[0071] The battery cell 101 comprises a rechargeable battery cell 101. That is, the battery cell 101 is operable to undergo successive charge and discharge cycles. The battery cell 101 includes connectors 120 for connecting the cell 101 across a load to which the cell 101 is discharged and/or a power source from which the cell 101 is charged. The connectors 120 may, for example, comprise connector tabs 120.

[0072] In the example depicted in Figure 1, the battery 100 is shown as including a single battery cell 101. However, some examples of a battery 100 may include a plurality of cells 101. For example, a battery 100 may include a plurality of cells 101 connected in series with each other, in parallel with each other or in a combination of series and parallel connections.

Typically, cells 101 connected in series with each other will serve to increase the voltage of the battery 100 and cells 101 connected in parallel with each other will serve to increase the total capacity of the battery 100.

[0073] In at least some examples according to the present disclosure, the battery cell 101 may comprise a lithium sulphur (Li-S) battery cell. For the purposes of this description, a battery 100 comprising one or more lithium sulphur battery cells 101 may be referred to as a lithium sulphur battery.

[0074] Whilst examples are described herein with reference to lithium sulphur battery cells, the methods and apparatus described herein may additionally or alternatively be used in examples including one or more battery cells other than a lithium sulphur battery cell. For instance, some examples contemplated herein may include one or more lithium ion battery cells.

[0075] The heat transfer device 104 is operable to transfer heat to or from the battery 100. For example, the heat transfer device 104 may be arranged to apply heating and/or cooling to the cell 101. The heat transfer device 104 may comprise any component or combination of components suitable for transferring heat to or from the battery 100.

[0076] In examples in which the heat transfer device 104 is arranged to apply heating to the battery 100, the heat transfer device 104 may comprise at least one heating element (such as a heating plate) thermally coupled to the battery 100. Additionally or alternatively, the heat transfer device 104 may comprise one or more conduits (not shown) through which a heat transfer fluid (e.g. water or other fluid) may be forced to pass, where the one or more conduits are thermally coupled to the battery 100. The heat transfer device 104 may further comprise at least one heating element (not shown) arranged to heat the heat transfer fluid passing through the one or more conduits. The battery 100 may therefore be heated by active heating of the heat transfer fluid. Additionally or alternatively, the battery 100 may be arranged in a sealed chamber (not shown) and the heat transfer device 104 may be arranged to heat the chamber so as to increase the ambient temperature in the chamber and apply heating to the battery 100.

[0077] In examples in which the heat transfer device 104 is arranged to apply cooling to the battery 100, the heat transfer device 104 may, for example, comprise at least one cooling element (such as a cooling plate) thermally coupled to the battery 100. Additionally or alternatively, the heat transfer device 104 may comprise one or more conduits (not shown) through which a heat transfer fluid (e.g. water or other fluid) may be forced to pass, where the one or more conduits are thermally coupled to the battery 100. The heat transfer device 104 may further comprise at least one cooling element (not shown) arranged to cool the heat transfer fluid passing through the one or more conduits. The battery 104 may therefore be cooled by active cooling of the heat transfer fluid. Additionally or alternatively, the battery 100 may be arranged in a sealed chamber (not shown) and the heat transfer device 104 may be arranged to cool the chamber so as to reduce the ambient temperature in the chamber.

[0078] In at least some examples, the heat transfer device 104 may be operable to apply heating and cooling to the battery 100 (at different times). For example, the heat transfer device 104 may comprise at least one heating element (such as a heating plate) and at least one cooling element (such as a cooling plate), both thermally coupled to the battery 100. The heating element and the cooling elements may be operated at different times to heat and cool the battery 100 according to the temperature requirements of the battery 100.

[0079] In examples in which the heat transfer device 104 comprises one or more conduits (thermally coupled to the battery) through which a heat transfer fluid is forced to pass, the heat transfer device 104 may further include at least one heating element and at least one cooling element arranged to heat and cool the heat transfer fluid respectively. The heating element and the cooling element may be operated at different times to heat and cool the heat transfer fluid in order to heat or cool the battery 100 according to the temperature requirements of the battery 100.

[0080] In examples in which the battery 100 is arranged in a sealed chamber, the heat transfer device 104 may be operable to heat and cool the chamber at different times. The heat transfer device 104 may be operated to heat or cool the chamber according to the temperature requirements of the battery 100.

[0081] In general, the heat transfer device 104 may comprise any component or collection of components operable to cause heating and/or cooling of the battery 100 and is not limited by any specific implementations described herein.

[0082] The controller 102 is configured to control the heat transfer device 104 to apply heating and/or cooling to the battery 100. For example, as is indicated in the example shown in Figure 1, the controller 102 may provide an input 105 to the heat transfer device 104. The heat transfer device 104 may operate to provide heating or cooling to the battery 100 in dependence on the input 105 received from the controller 102.

[0083] In some examples, the input 105 may comprise a signal indicative of instructions to be carried out by the heat transfer device 104. In some examples, the input 105 may comprise a variable power supply. For example, the controller 102 may be configured to vary the magnitude of power provided to the heat transfer device 104 in order to vary an amount of heating and/or cooling provided to the battery 100. In some examples, the controller 102 may be configured to turn on a power supply provided to the heat transfer device 104 at times when heating and/or cooling of the battery 100 is desired and to turn off a power supply provided to the heat transfer device 104 at times when no heating and/or cooling of the battery 100 is desired.

[0084] Whilst, the example shown in Figure 1 indicates a single input 105 being provided to the heat transfer device 104, it will be appreciated that in some examples, the heat transfer device 104 may include a plurality of components which may be provided with separate inputs from the controller 102. For example, the heat transfer device 104 may include at least one component arranged to provide heating to the battery 100 and at least one component arranged to provide cooling to the battery 100. In such an example, the controller 102 may provide separate inputs 105 to the heating and cooling components.

[0085] As was explained above, in some examples (such as the example shown in Figure 1), the temperature control system 103 may further comprise a temperature measurement device 106. The temperature measurement device 106 is arranged to measure a temperature, which is at least indicative of the temperature of the battery 100 (e.g. the temperature of the cell 101). The temperature measurement device 106 may, for example, comprise a thermometer positioned in proximity to or otherwise thermally coupled to the cell 101. The controller 102 may be configured to control the heat transfer device in dependence on measurements made by the temperature measurement device 106. As is indicated in Figure 1, the controller 102 may receive an input 107 from the temperature measurement device 106. The input 107 is indicative of temperature measurements made by the temperature measurement device 106.

[0086] The controller 102 may control the heat transfer device 104 in dependence on the input 107 provided from the temperature measurement device 106. For example, the controller 102 may control the heat transfer device 104 in order to change the temperature of the battery towards a target temperature and may respond to an input 107 which indicates that a measured temperature differs from the target temperature. For instance, if the input 107 suggests that a measured temperature is below a target temperature then the controller 102 may respond by providing an input 105 to the heat transfer device 104 to cause the heat transfer device to provide heating to the battery, in order to increase the temperature of the battery towards the target temperature. Additionally or alternatively, the controller 102 may respond by providing an input 105 to the heat transfer device 104 to cause the heat transfer device to reduce an amount of cooling provided to the battery (e.g. by turning off or reducing any active cooling) in order to allow the temperature of the battery 100 to increase towards the target temperature.

[0087] If the input 107 suggests that a measured temperature is above a target temperature then the controller 102 may respond by providing an input 105 to the heat transfer device 104 to cause the heat transfer 104 device to provide cooling to the battery 100 in order to decrease the temperature of the battery towards the target temperature. Additionally or alternatively, the controller 102 may respond by providing an input 105 to the heat transfer device 104 to cause the heat transfer device 104 to reduce an amount of heating provided to the battery (e.g. by turning off or reducing any active heating) in order to allow the temperature of the battery 100 to decrease towards the target temperature.

[0088] Whilst, the example shown in Figure 1 indicates a single input 107 being provided to the controller 102 from a single temperature measurement device 106, it will be appreciated that in some examples, the temperature measurement device 106 may include a plurality of components which may, for example, provide separate inputs 107 to the controller 102. For example, the temperature measurement device 106 may include a plurality of components arranged to measure temperature at different locations (e.g. distributed around the battery 100). In such an example, the controller 102 may be provided with separate inputs 107 indicative of separate temperature measurements which are made at different locations.

[0089] Whilst examples were described above in which the controller 102 controls the heat transfer device 104 in dependence on temperature measurements made by a temperature measurement device 106, in other examples, the controller 102 may control the heat transfer device 104 without receiving temperature measurements. For example, the controller 102 may control the heat transfer device 104 in dependence on a known or predicted temperature response of the battery 100. For example, an amount of heating and/or cooling which is to be provided to the battery 100 may be pre-determined and the controller 102 may control the heat transfer device 104 according to a pre-configured control schedule. In such embodiments, the controller 102 may control the heat transfer device 104 to change the temperature of the battery 100 towards a target temperature, according to a pre-configured control schedule.

[0090] As was mentioned above, the controller 102 may be configured to control the heat transfer device 104 to apply heating and/or cooling to the battery in order to change the temperature of the battery 100 towards a target temperature. This may, for example, include applying heating and/or cooling to the battery 100 in order to maintain the temperature of the battery 100 substantially at or near to the target temperature once the target temperature has been reached. In some situations, the temperature of the battery 100 may not reach the target temperature and/or may reach a temperature different to the target temperature. In general, the heat transfer device 104 may merely be controlled in order to move the temperature of the battery towards the target temperature.

[0091] As will be explained in further detail below, the target temperature may represent a temperature at which it is desirable to operate the battery 100 during charging and/or discharging. The target temperature may additionally or alternatively be chosen in order to reduce an amount of energy required to heat and/or cool the battery 100 towards the target temperature. According to examples contemplated herein, the target temperature is varied during charging and/or discharging. That is, the target temperature does not remain constant through an entire charge and/or discharge cycle of the battery 100.

[0092] In at least some examples, the controller 102 may be configured to vary the target temperature in dependence on one or more properties indicative of the state of charge of the battery 100. The one or more properties indicative of the state of charge of the battery 100 may be determined, for example, by a battery monitoring device.

[0093] Figure 2 is a schematic illustration of a further example of a battery 100 according to the present disclosure. The battery 100 depicted in Figure 2 comprises corresponding components to those shown in Figure 1 and described above, where the corresponding components are provided with the same reference numerals. These corresponding components will not be described again in detail with reference to Figure 1.

[0094] The battery depicted in Figure 2 further includes (in addition to the components shown in Figure 1) a battery monitoring device 108. The battery monitoring device 108 is arranged to detect one or more electrical properties associated with the battery 100 and determine at least one property indicative of the state of charge of the battery 100. The at least one property which is indicative of the state of charge of the battery 100 may, for example, comprise a voltage of the battery 100. Additionally or alternatively, the at least one property which is indicative of the state of charge of the battery 100 may comprise a rate of change of a voltage of the battery 100. Additionally or alternatively, the at least one property which is indicative of the state of charge of the battery 100 may comprise an amount of charge which has been discharged from or charged to the battery 100.

[0095] In the example which is depicted in Figure 2 the battery monitoring device 108 may include at least one component electrically connected across the cell 101 which may, for example, be arranged to measure a voltage across the cell 101. Additionally or alternatively, the battery monitoring device 108 may include at least one component arranged to measure an electrical current flowing through the cell 101 and/or the electrical resistance of the cell 101. In some examples, the battery monitoring device 108 may include components arranged to measure a plurality of electrical properties associated with the cell 101. For example, the battery monitoring device 108 may comprise components arranged to measure the voltage across the cell 101, the current flowing through the cell and/or the resistance of the cell 101.

[0096] In examples in which the battery 100 comprises a plurality of cells 101, the battery monitoring device 108 may be arranged to measure one or more electrical properties of the plurality of cells 101 as a whole and/or may be arranged to measure one or more electrical properties of separate cells 101 (or groups of cells) individually. For example, the battery monitoring device 108 may be arranged to measure the voltage, current and/or resistance of a plurality of cells electrically connected together (e.g. connected in series, in parallel and/or in a combination of series and parallel connections). Additionally or alternatively, the battery monitoring device 108 may be arranged to separately measure the voltage, current and/or resistance of one or a subset of the plurality of cells 101.

[0097] As is shown in Figure 2, the battery monitoring device 108 may be arranged to provide an input 109 to the controller 102. The input 109 is indicative of the at least one property determined by the battery monitoring device 108, which is indicative of the state of charge of the battery 100. The controller may be configured to control the heat transfer device based, at least partially, on the input 109 provided from the battery monitoring device 108.

[0098] As was explained above, the controller 102 controls the heat transfer device 104 to change the temperature of the battery 100 towards a target temperature. The target temperature may be a temperature at which it is desirable to operate the battery 100. For example, it may be desirable to operate the battery 100 (e.g. charge and/or discharge the battery) at a given temperature or at least within a given temperature range. Operation of the battery 100 at temperatures other than the target temperature or at temperatures outside of a given temperature range may degrade performance of the battery and/or may cause damage to the battery, leading to future performance degradation. For example, operation of the battery 100 at temperatures other than the target temperature or at temperatures outside of a given temperature range may reduce the useable capacity and/or the voltage of the battery.

[0099] Figure 3 is a schematic representation of the voltage of a lithium sulphur (Li-S) battery during several charge and discharge cycles carried out at different temperatures. The voltage of the battery is shown as a function of battery capacity (in milliamp hours per gram of sulphur) during charge and discharge. The capacity of the battery is indicated in Figure 3 as increasing during charging from an initial capacity of 0. That is, the voltage of the battery is at a minimum at the start of the charging cycles and generally increases during charging.

[00100] The capacity of the battery indicated in Figure 3 during discharge represents capacity which is discharged from the battery and is also shown as increasing from an initial discharged capacity of 0 during discharge. That is, the voltage of the battery is at a maximum at the start of the discharge cycle and generally decreases during discharging (although it will be appreciated from Figure 3 that there is at least a portion of the discharge cycle during which voltage briefly increases during discharge).

[00101] The voltage of the Li-S battery is shown in Figure 3 during four different chargedischarge cycles carried out at four different temperatures (0°C, 10°C, 20°C and 30°C). In the examples represented in Figure 3, the battery is first discharged at a given temperature and then charged at the same temperature. For example, the charge cycles at the respective temperatures (0°C, 10°C, 20°C and 30°C) follow the discharge cycles at the same respective temperatures. The charging curves shown in Figure 3 may therefore be at least partially influenced by the discharge cycle which occurred prior to the represented charge cycles (and at the same temperature).

[00102] As can be seen from Figure 3, the voltage and capacity characteristics of the battery are dependent on temperature, for at least part of a charge-discharge cycle. For example, during at least a portion of a discharge cycle of the battery, the voltage of the battery decreases earlier and at a smaller discharge capacity when discharging at lower temperatures. For example, the voltage drops earliest towards the end of discharge when discharging at 0°C (it will however be appreciated that this may not hold true for all portions of the discharge cycle). More charge can therefore be drawn from the battery during discharge when discharge is carried out at higher temperatures (at least within the range of temperatures shown in Figure 3), which may allow a larger proportion of the total capacity of the battery to be utilised.

[00103] In the range of temperatures shown in Figure 3, during charging of the battery the voltage of the battery at a given capacity tends to be lower at higher temperatures. Put another way, the voltage of the battery increases at a lower capacity state during charging at lower temperatures. However, at least some of this difference may be attributed to the temperature at which the battery was discharged prior to being charged. For example, the discharge curve at 0°C in Figure 3 shows that less than 1000 mAh/g is discharged from the battery, whereas when the battery is discharged at 30°C, close to 1200 mAh/g is discharged. A larger proportion of the total available capacity of the battery has therefore been discharged at 30°C than at 0°C. When the same battery is subsequently charged, there will be more discharged active species in the battery available to be recharged in the battery which was discharged at 30°C than the battery which was discharged at 0°C. Consequently, more capacity can be added to the battery discharged at 30°C than the battery discharged at 0°C before the battery reaches its maximum capacity (at which point the voltage of the battery rapidly increases above 2.45 V as shown in Figure 3). The difference in the charging curves at different temperatures shown in Figure 3 may therefore be at least partially attributed to the different temperatures at which they were discharged prior to being charged.

[00104] As was explained above with reference to Figure 3, at least some of the performance characteristics of a Li-S battery are at least partially dependent on the temperature at which the battery is discharged and/or charged. For example, at least within the range of temperatures contemplated in Figure 3, more capacity may be discharged from a Li-S battery at higher temperatures (for example 20-30°C) than at lower temperatures (for example 010°C). The temperature of a battery might therefore be controlled during charging and/or discharging in order to realise desired performance characteristics of a battery.

[00105] In order to realise desired performance characteristics of a Li-S battery, the temperature of the battery might typically be controlled to be at a constant target temperature or at least within a target temperature range throughout charge and/or discharge. For example, the battery may be heated or cooled to bring it to a temperature of approximately 20-30°C during charge and/or discharge.

[00106] Such temperature control of a battery may find particular application when a battery is used in particularly warm or cool environments. For example, batteries of the type contemplated herein may be used as a power source on an aircraft. For example, a battery may be used as a power source for propelling the aircraft and/or as a power source for auxiliary systems on the aircraft. One example of an aircraft which may be at least partially powered by a battery is an unmanned aerial vehicle (UAV).

[00107] Aircraft are typically exposed to low ambient temperatures when flying at high altitude and thus a battery on an aircraft may be exposed to low ambient temperatures during operation. For example, aircraft such as UAVs may be operated at altitudes of greater than about 4000 feet at which the ambient temperature may be as low as -50°C or even lower. In such an application, the battery may be heated in order to operate the battery at a desired temperature, such as at around 20-30°C. However, such heating uses energy. Energy used to heat the battery may be provided by the battery itself or from another power source situated on the aircraft and therefore diminishes the total energy available on the aircraft.

[00108] According to examples disclosed herein, a target temperature of the battery 100 is varied during charging and/or discharging of the battery 100. It has been realised that the temperature dependence of a battery may not be the same throughout a discharge and/or charge cycle. For example, performance characteristics of a battery may be strongly dependent on temperature during a first portion of a discharge and/or charge cycle but may be only weakly dependent on temperature during a second portion of a discharge and/or charge cycle (the first portion of the discharge and/or charge cycle may occur before or after the second portion of the discharge and/or charge cycle). The target temperature of the battery may therefore be varied during discharge and/or charge of the battery in accordance with the variable temperature dependence of the battery during discharge and/or charge.

[00109] Additionally or alternatively, a temperature which brings about desired performance characteristics during a first portion of a discharge and/or charge cycle may be different to a temperature which brings about desired performance characteristics during a second portion of a discharge and/or charge cycle. The target temperature of the battery may therefore be varied during discharge and/or charge of the battery in order to realise desired performance characteristics of the battery during different portions of a discharge and/or charge cycle.

[00110] Figure 4 is a schematic representation of the temperature of a battery 100 during a discharge and charge cycle, where the temperature of the battery is controlled by an example of a temperature management system according to the present disclosure. Also shown in Figure 4 is the voltage of the battery 100 during the discharge and charge cycle. The temperature and voltage are both shown as a function of capacity discharged and charged from and to the battery and time in hours. The portions of Figure 4 during which the battery is discharging and charging are clearly marked in Figure 4.

[00111] As is shown in Figure 4, the temperature of the battery is varied between a first target temperature Ti and a second target temperature T₂, where the second target temperature is higher T₂ than the first target temperature T1. During a first portion 401 of the discharge cycle (until approximately 4000 mAH has been discharged from the battery), the target temperature is set at the first target temperature T1. That is, during the first portion 401, the controller 102 controls the heat transfer device 104 to change the temperature of the battery towards the first target temperature T1. As is indicated in Figure 4, this may comprise maintaining the temperature of the battery substantially at the first target temperature T1.

[00112] During a second portion 402 of the discharge cycle, the target temperature is set at the second target temperature T₂. That is, during the first portion 401, the controller 102 controls the heat transfer device 104 to change the temperature of the battery towards the second target temperature T₂. As is indicated in Figure 4, the temperature of the battery may take some time before it reaches the second target temperature T₂. Once the temperature of the battery reaches the second target temperature T₂, the temperature control process comprises maintaining the temperature of the battery substantially at the second target temperature T₂.

[00113] As can be seen from Figure 3, during an initial portion of a discharge cycle, the voltage curves at different temperatures are closely matched to each other. That is, the voltage and capacity characteristics of the battery are not strongly dependent on temperature during an initial portion of the discharge cycle. The initial portion of the discharge cycle shown in Figure 3, during which the battery is relatively invariant with changes in temperature, roughly corresponds to the first portion 401 of the discharge cycle shown in Figure 4. Since the voltage and capacity characteristics during the first portion 401 of the discharge cycle are relatively invariant to temperature, a target temperature may be chosen which reduces an amount of energy used to heat or cool the battery during the first portion 401, without degrading significantly performance characteristics of the battery.

[00114] In the example represented in Figure 4, it is assumed that the ambient temperature is lower than a given temperature range in which it is desirable to operate the battery (for example, about 0-30°C). The battery is therefore heated in order to bring the temperature of the battery into the given temperature range and thus a lower target temperature requires less energy to heat the battery to the target temperature. As is shown in Figure 4, a relatively low first target temperature Ti is chosen for the first portion 401 of the discharge cycle. For example, the first target temperature Ti may about 0-5°C. By setting a relatively low target temperature Ti during the first portion of the discharge cycle, an amount of energy used to heat the battery during the first portion of the discharge cycle is reduced when compared to a higher target temperature (e.g. a target temperature of about 20°C or more).

[00115] Furthermore, whilst the voltage and capacity characteristics during the first portion 401 of the discharge cycle are not strongly dependent on temperature, to the extent that they are, the voltage profile at lower temperatures may exhibit preferred properties when compared to the voltage profile at higher temperatures (at least within the range of temperatures displayed in Figure 3). Choosing a relatively low target temperature Ti during the first portion 401 of the discharge cycle may therefore improve battery performance in addition to or alternatively to reducing an amount energy used to heat the battery.

[00116] During later stages of the discharge cycle, the voltage curves at different temperatures shown in Figure 3, differ from each other and thus the voltage and capacity characteristics of the battery are dependent on temperature. For example, the higher the temperature, the larger the capacity that is discharged from the battery before the voltage of the battery drops. A later portion of the discharge cycles shown in Figure 3, during which the discharge characteristics are dependent on temperature, roughly corresponds to the second portion 402 of the discharge cycle shown in Figure 4. As was discussed above, during this portion of the discharge cycle it may be desirable to discharge the battery at a higher temperature (e.g. about 20-30°C) in order to allow a larger proportion of the available capacity of the battery to be discharged. A second target temperature T2 which is greater than the first target temperature Ti may therefore be set for the second portion 402 of the discharge cycle (as is shown in Figure 4). Whilst more energy may be used to heat the battery to the second target temperature T2 during the second portion of the discharge cycle, the use of a lower target temperature Τι during the first portion 401 of the discharge cycle reduces the total energy used during the discharge cycle (when compared to maintaining the second target temperature T2 throughout the entire discharge cycle).

[00117] In order to further reduce an amount of energy used to heat the battery, the target temperature may be reduced to the first target temperature T1 during at least part a charge cycle of the battery. For example, as is shown in Figure 4 the target temperature may be held at the second target temperature T2 during a first portion 403 of the charge cycle before being reduced to the first target temperature T1 during a second portion 404 of the charge cycle. As will be explained further below, it has been found that for at least some batteries, the target temperature may be reduced during at least part of the charging cycle of the battery without significantly adversely affecting performance characteristics of the battery.

[00118] In order to better explain the effects of the use of a variable target temperature during discharge and charge of a Li-S battery, a comparison between discharge and charge cycles carried out under different temperature control regimes is presented in Figures 5 and 6. Figure is a schematic representation of the voltage of a Li-S battery as a function of capacity during three discharge cycles carried out under three different temperature control regimes. Figure is a schematic representation of the voltage of a Li-S battery as a function of capacity during three charge cycles carried out under three different temperature control regimes.

[00119] The voltage curves shown in Figures 5 and 6 and labelled “5°C” and “20°C” represent discharge and charge cycles carried out using constant target temperatures of 5°C and 20°C respectively. That is, the same target temperature (of 5°C and 20°C) is maintained throughout the discharge and charge cycles. The voltage curves shown in Figures 5 and 6 and labelled “variable temperature” represent discharge and charge cycles carried out whilst varying the target temperature during discharging and charging. In particular, the variable temperature cycles represented in Figures 5 and 6 were carried out using a temperature control regime similar to that which was described above with reference to Figure 4. That is, during discharge of the battery, a first target temperature T1 is set during a first portion 401 of the discharge cycle and a second target temperature T2 is set during a second portion 402 of the discharge cycle. The point at which the target temperature is switched between the first target temperature T1 and the second target temperature T2 is denoted with an arrow labelled 501 in Figure 5. During charging of the battery, the second target temperature T2 is set during a first portion 403 of the charge cycle and the first target temperature T2 is set during a second portion 404 of the charge cycle. The point at which the target temperature is switched between the second target temperature T2 and the first target temperature T1 is denoted with an arrow labelled 502 in Figure 6. In the example represented in Figures 5 and 6, the first target temperature T1 is about 5°C and the second target temperature T2 is about 20°C.

[00120] As can be seen in Figure 5, the voltage curve representing the variable temperature control regime during discharge closely matches the voltage curve representing discharge at a constant temperature of 20°C. Without wishing to be bound to any particular theory, this may be because performance characteristics of the battery are relatively invariant with temperature during a first portion of the discharge cycle (as shown in Figure 3). Using a lower target temperature (e.g. of about 5°C) during the first portion of the discharge cycle, before increasing the target temperature (to about 20°C) during the second portion of the discharge cycle, therefore has only a relatively small effect on performance of the battery when compared to maintaining the temperature of the battery at 20°C throughout the discharge cycle. However, when compared to maintaining the temperature of the battery at 20°C throughout the discharge cycle, the amount of energy used to heat the battery during the discharge cycle is reduced by using the variable temperature regime (as was described above).

[00121] As can be seen in Figure 6, the voltage curve representing the variable temperature control regime during charging, matches the voltage curve representing the discharge at a constant temperature of 20°C for much of the charge cycle. As was explained above, during a first portion of the charge cycle, the target temperature is held at 20°C. It is therefore to be expected that during the first portion of the charge cycle, the variable temperature voltage curve closely matches the 20°C voltage curve.

[00122] During a second portion of the charge cycle, the target temperature (using the variable temperature regime) is reduced to 5°C. It might therefore be expected that the variable temperature voltage curve would tend towards the 5°C voltage curve during the second portion of the charging cycle. However, as can be seen in Figure 6, whilst the variable temperature curve does show some deviation from the 20°C voltage curve, for the most part the variable temperature curve remains more closely matched to the 20°C voltage curve than the 5°C voltage curve, even after the target temperature is reduced to 5°C. Without wishing to be bound to any particular theory, this may be at least partially due to the discharge cycle which the battery underwent (as represented in Figure 5) prior to the charge cycle represented in Figure 6.

[00123] As was explained above with reference to Figure 5, when using the variable temperature regime, the battery is discharged to approximately the same extent as discharging the battery at a constant temperature of 20°C. A battery discharged using the variable temperature regime therefore has a similar number of discharged active species available to be recharged as a battery discharged at a constant temperature of 20°C. During subsequent charging of the same battery, it is therefore possible to charge the battery to a higher capacity when compared to, for example, the 5°C charging regime, even if the temperature of the battery drops to 5°C during at least part of the charging cycle. The voltage curve of the variable temperature charging regime therefore extends to a similar capacity as the constant temperature 20°C charging regime, and a similar proportion of the available capacity of the battery is utilised.

[00124] As was explained above, the voltage curve representing the variable temperature charging regime closely matches the voltage curve representing charging at a constant temperature of 20°C, and allows a similar extent of the available capacity of the battery to be utilised. However, similarly to the variable temperature discharge regime described above with reference to Figure 5, by using a variable temperature charging regime the amount of energy used to heat the battery during charging is significantly reduced when compared to charging the battery at a constant temperature of 20°C. For example, during a second portion of the charge cycle, the target temperature of the battery is reduced to 5°C which uses less energy than heating the battery to 20°C.

[00125] A particular example of a variable temperature control regime during discharge and charge of a battery has been described above with reference to Figures 4-6. However, according to other examples disclosed herein, different variable temperature control regimes may be utilised. In general, any temperature control may be utilised which includes varying a target temperature of the battery during charging and/or discharging of the battery.

[00126] In some examples, varying the target temperature during charging and/or discharging may comprise setting a first target temperature for at least a first portion of a charge and/or discharge cycle and switching the target temperature to a second target temperature for at least a second portion of a charge and/or discharge cycle (as is the case for the example described above with reference to Figures 4-6). That is, varying the target temperature may comprise one or more step changes between two or more different target temperatures during charging and/or discharging. In some examples, the target temperature may be varied between more than two different target temperatures during a charge and/or a discharge cycle. For example, in addition to first and second target temperatures described above, the target temperature may be set to a third target temperature for at least a third portion of a charge and/or discharge cycle.

[00127] In some examples, the target temperature may be varied in a continuous manner for at least part of a charge and/or discharge cycle. For example, the target temperature may be gradually increased or decreased during at least a portion of a charge and/or discharge cycle. In some examples, the target temperature may be gradually increased or decreased between one or more target temperatures at which the target temperature is held constant for at least a portion of a charge and/or discharge cycle.

[00128] According to at least some examples disclosed herein, the controller 102 may be configured to increase the target temperature during discharge of the battery. For instance, according to the specific example described above with reference to Figures 4-6, the target temperature is increased during discharge of the battery. As was explained above, increasing the target temperature during discharge of the battery may be particularly advantageous in situations in which the ambient temperature under which the battery is operated, is lower than the target temperature. In such situations, the battery is generally heated in order to change the temperature of the battery towards the target temperature and thus the lower the target temperature, the less energy is used to heat the battery to the target temperature. However, a battery may also be operated in situations in which the ambient temperature is higher than the target temperature. In such situations, the battery is generally cooled in order to change the temperature of the battery towards the target temperature and thus the higher the target temperature, the less energy is used to cool the battery to the target temperature. In such situations a different temperature control regime may be used in order to reduce an amount of energy used to heat or cool the battery during discharge.

[00129] According to at least some examples disclosed herein, the controller 102 may be configured to decrease the target temperature during charging of the battery. For instance, according to the specific example described above with reference to Figures 4-6, the target temperature is decreased during discharge of the battery. As was explained above, decreasing the target temperature during discharge of the battery advantageously reduces an amount of energy used to heat the battery during a second portion of a charge cycle of the battery (particularly in situations in which the ambient temperature is lower than the target temperature). However, in some examples a different temperature control regime during charging may be used. For instance, in some examples a relatively low target temperature may be used during an initial portion of a charge cycle. As can be seen from Figure 3, the voltage curve during a charging cycle may be relatively invariant to temperature at least during an initial portion of a charging cycle. According to some examples, this may utilised to maintain a relatively low target temperature (e.g. less than about 15°C, less than about 10°C or even 5°C or less) during an initial portion of a charging cycle. According to such examples, the target temperature may be further decreased during charging of the battery, or in some alternative examples may even be increased during charging.

[00130] In some examples, the target temperature may be varied during one of a discharge cycle and a charge cycle and may held substantially constant during the other of a discharge cycle and a discharge cycle. For example, the target temperature may be varied during discharge of the battery and may be held substantially constant during charging of the battery.

[00131] The temperature control regime which is used in a particular example may depend on a number of factors such as the dependence of the performance of a battery on temperature, desired performance characteristics of the battery during operation, and/or the ambient temperature conditions in which the battery is to be operated. For example, in situations in which the ambient temperature is lower than a temperature range in which the battery is to be operated, a temperature control regime may be chosen which seeks to reduce the target temperature during at least a portion of a discharge and/or charge cycle (when compared to a typical constant temperature control regime) so as to reduce an amount of energy used to heat the battery to the target temperature. However, in situations in which the ambient temperature is higher than a temperature range in which the battery is to be operated, a temperature control regime may be chosen which seeks to increase the target temperature during at least a portion of discharge and/or charge cycle (when compared to a typical constant temperature control regime) so as to reduce an amount of energy used to cool the battery to the target temperature.

[00132] According to at least some examples disclosed herein, the target temperature may be varied within a given temperature range in which a battery may be operated. For example, the target temperature may in general be higher than about -10°C. The target temperature may in general be less than about 40°C. However, it will be appreciated that a given temperature range in which a battery may be operated may depend on the particular chemistry and properties of the battery to be used.

[00133] As was briefly explained above, according to at least some examples disclosed herein, the controller 102 may be configured to vary the target temperature in dependence on one or more properties indicative of the state of charge of the battery. It will be appreciated that there are a number of different methods and properties used to determine or indicate a state of charge of the battery, which may depend on the particular chemistry and properties of the battery in question. In general, any suitable property or combination of properties which are at least indicative of the stage in a discharge and/or charge cycle of a battery which has been reached may be used to control the target temperature of the battery.

[00134] In some examples, the target temperature may be varied in dependence on a voltage of the battery. For example, with reference to the particular example represented in Figure 4, the target temperature may be increased from the first target temperature Ti to the second target temperature T2 in dependence on the voltage of the battery decreasing below a given threshold voltage, which may be indicative of a given state of discharge having been reached. Additionally or alternatively, the target temperature may be decreased from the second target temperature T2 to the first target temperature in dependence on the voltage of the battery increasing above a given threshold voltage which may be indicative of a given state of charge having been reached.

[00135] In some examples, the target temperature may be varied in dependence on a rate of change of a voltage of the battery. As can be seen for example, in Figures 3-6 the rate of change of the voltage of a Li-S battery undergoes a number of distinctive changes during discharge and charging. For example, during an initial portion of a discharge cycle the voltage monotonically decreases before reaching a local minimum voltage. The voltage then increases slightly to a voltage plateau during which the voltage remains approximately constant before monotonically decreasing again towards the end of the discharge cycle. The rate of change of voltage may therefore be used to determine that a given point in a discharge cycle has been reached. For example, the rate of change of voltage may be used to determine that the voltage has reached or is approaching a local minimum voltage and/or that the voltage plateau region of the discharge cycle has been reached.

[00136] According to at least some examples, the target temperature may be changed when the rate of change of the voltage of the battery undergoes a transition between a period in which the voltage of the battery monotonically increases or decreases during charging or discharging and a period in which the voltage remains approximately constant during charging or discharging. For example, as can be seen in Figure 3, the voltage curves at different temperatures begin to deviate from each other as the voltage curves approach or reach a transition period at which the voltage reaches a local minimum voltage and then settles at a voltage plateau. This may therefore represent a point in the discharge cycle at which it may be advantageous to change the target temperature of the battery in order to bring about advantageous performance characteristics of the battery which are dependent on temperature. In at least some examples, (for example as is shown in the particular example represented in Figure 4) the target temperature may be increased during discharge when the voltage approaches or reaches the voltage plateau region (during which the voltage remains approximately constant during discharge). For example, as the voltage of the battery approaches or reaches a local minimum voltage, the target temperature may be increased.

[00137] In some examples, the target temperature may be varied in dependence on an amount of charge discharged from or charged to the battery. For example, the current flowing from or to the battery during discharge or charge may be measured and may be integrated over time in order to determine an amount of charge which has been discharged from or charged to the battery (which may be referred to as coulomb counting). The amount of charge discharged from or charged to the battery may be used to at least approximate a stage of a discharge or charge cycle which has been reached, and may therefore be used to control the target temperature of the battery.

[00138] In some examples, the target temperature may be varied in dependence on one or more other measured properties not specifically described above. For example, the target temperature may be varied in dependence on changes in the internal resistance of the battery, which may vary as a function of the state of charge of the battery.

[00139] Examples have been described above in which a battery is heated by applying to active heating to the battery and/or cooled by applying active heating to the battery. However, in at least some examples, a battery may be heated through absence of active cooling of the battery and/or the battery may be cooled through absence of active heating of the battery. For example, active heating of the battery may be reduced or turned off during at least part of a charge and/or discharge cycle in order to reduce the temperature of the battery. Additionally or alternatively, active cooling of the battery may be reduced or turned off during at least part of a charge and/or discharge cycle in order to increase the temperature of the battery.

[00140] It will be appreciated that embodiments of the present invention can be realised in the form of hardware, software or a combination of hardware and software. Any such software may be stored in the form of volatile or non-volatile storage such as, for example, a storage device like a ROM, whether erasable or rewritable or not, or in the form of memory such as, for example, RAM, memory chips, device or integrated circuits or on an optically or magnetically readable medium such as, for example, a CD, DVD, magnetic disk or magnetic tape. It will be appreciated that the storage devices and storage media are embodiments of machine-readable storage that are suitable for storing a program or programs that, when executed, implement embodiments of the present invention. Accordingly, embodiments provide a program comprising code for implementing a system or method as claimed in any preceding claim and a machine readable storage storing such a program. Still further, embodiments of the present invention may be conveyed electronically via any medium such as a communication signal carried over a wired or wireless connection and embodiments suitably encompass the same.

[00141] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing examples. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A temperature management system for a battery, the temperature management system comprising:

a heat transfer device operable to apply heating and/or cooling to the battery;

a controller configured to control the heat transfer device to apply heating and/or cooling to the battery in order to change the temperature of the battery towards a target temperature, wherein the controller is further configured to vary the target temperature during charging and/or discharging of the battery.

2. The temperature management system of claim 1, wherein the controller is further configured to increase the target temperature during discharge of the battery.

3. The temperature management system of claim 1 or 2, wherein the controller is further configured to decrease the target temperature during charging of the battery.

4. The temperature management system of any preceding claim, wherein the controller is further configured to vary the target temperature in dependence on one or more properties indicative of the state of charge of the battery.

5. The temperature management system of claim 4, wherein the one or more properties indicative of the state of charge of the battery comprises a voltage of the battery.

6. The temperature management system of claim 4 or 5, wherein the one or more properties indicative of the state of charge of the battery comprises a rate of change of a voltage of the battery.

7. The temperature management system of claim 6, wherein the controller is configured to vary the target temperature in dependence on the rate of change of the voltage of the battery undergoing a transition between a period in which the voltage of the battery monotonically increases or decreases during charging or discharging and a period in which the voltage remaining substantially constant during charging or discharging.

8. The temperature management system of any of claims 4-7, wherein the one or more properties indicative of the state of charge of the battery comprises an amount of charge discharged or charged to or from the battery.

9. The temperature management system of any preceding claim, wherein the heat transfer device comprises at least one component operable to apply active heating to the battery.

10. The temperature management system of claim 9, wherein the controller is configured to turn off the active heating of the battery during at least a portion of a charging or discharging cycle of the battery.

11. The temperature management system of any preceding claim, wherein the heat transfer device comprises at least one component operable to apply active cooling to the battery.

12. The temperature management system of claim 11, wherein the controller is configured to turn off the active cooling of the battery during at least a portion of a charging or discharging cycle of the battery.

13. The temperature management system of any preceding claim, wherein the temperature management system further comprises a temperature measurement device arranged to measure a temperature indicative of the temperature of the battery, and wherein the controller is configured to control the heat transfer device in dependence on the temperature measurements.

14. The temperature management system of any preceding claim, wherein the temperature management system is configured to control the temperature of a battery comprising at least one lithium sulphur battery cell.

15. A battery system comprising a battery and a temperature management system of any preceding claim, wherein the temperature management system is configured to control the temperature of the battery.

16. The battery system of claim 15, wherein the battery comprises at least one lithium sulphur battery cell.

17. A method of managing the temperature of a battery, the method comprising: controlling a heat transfer device to apply heating and/or cooling to the battery in order to change the temperature of the battery towards a target temperature; and varying the target temperature during charging and/or discharging of the battery.

18. Software which, when executed by a processer, is arranged to perform a method according to claim 17; optionally the software is stored on a computer readable medium.

Intellectual

Property

Office

Application No: GB1814886.6