Aerosol generating device battery verification

Abstract

An aerosol generating device (100) is disclosed. The device (100) comprises a replaceable battery (112) and charging equipment (114) configured to receive a charging voltage during a charging operation. A sensor (122) is provided to measure an indication of the charging voltage during the charging operation, and a controller (120) is configured to receive a plurality of measured indications of the charging voltage from the sensor (122) during a charging operation. The controller (120) can calculate an indication of a mean charging voltage based on the plurality of measured indications of the charging voltage and determine that the replaceable battery (112) is compatible if the indication of the mean charging voltage is above a compatibility threshold.

Description

[0001] AEROSOL GENERATING DEVICE BATTERY VERIFICATION

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to an aerosol generating device comprising a controller configured to verify a particular battery chemistry within a replaceable battery.

[0004] BACKGROUND

[0005] Consumer interest in reduced-risk or modified-risk aerosol generating devices (also known as vaporisers or electronic cigarettes) has increased significantly in recent years. Vaporisers offer an aid to habitual smokers wishing to quit using traditional tobacco products such as cigarettes, cigars, or rolling tobacco. Traditional tobacco products bum the tobacco to produce an aerosol which the user then inhales. Conversely, vaporisers generate an aerosol or vapour by heating an aerosol forming substrate, which may be a solid such as tobacco, or a liquid, such as e-liquid.

[0006] At present, there is an ever-increasing demand for aerosol generating devices that enable a user to replace components of the device that no longer function as intended, while retaining components that are still fully operational. In particular, there is demand for aerosol generating devices that are provided with a replaceable battery. However, should a user replace the battery of their aerosol generating device with one that is not recommended by the manufacturer, performance issues can arise leading to an unsatisfactory user experience. Furthermore, the manufacturer of the device is not in control of the safety of the replacement battery. As a result, it is desirable that the replacement battery inserted by the user is verified and established as being safe for use. The present application aims to address one or more of these problems.

[0007] SUMMARY OF INVENTION

[0008] In a first aspect of the invention, there is provided an aerosol generating device, comprising: a replaceable battery; a sensor configured to measure an indication of a charging voltage during a charging operation; and a controller configured to, during the charging operation: receive a plurality of measured indications of the charging voltage from the sensor; calculate an indication of an average charging voltage based on the plurality of measured indications of the charging voltage; determine that the replaceable battery is compatible if the indication of the average charging voltage is above a compatibility threshold; and determine that the replaceable battery is incompatible if the indication of the average changing voltage is below the compatibility threshold.

[0009] In this way, it may be determined whether the battery is compatible for use within the aerosol generating device. In this application, “compatible” can be understood to mean that the battery does not pose a risk to the safety of a user who is operating the aerosol generating device, while also allowing the device to operate as intended. In contrast, “incompatible” in this application can be understood to mean that the battery potentially poses a risk to the safety of the user who is operating the aerosol generating device, and / or that the battery does not allow the device to operate as intended. It has been found that it is possible to distinguish between different battery types by analysing the average charging voltage during the charging period. In particular, it has been found that certain battery chemistries can lead to different average charging voltages, and that this can be used to distinguish between compatible batteries and incompatible batteries. In some embodiments the average charging voltage may be calculated as the mean charging voltage, although it would be possible to use different mathematical calculations for the average in different embodiments.

[0010] The device can include charging equipment that can be configured to connect to a power grid or an auxiliary battery source. The charging equipment may receive power using a physical connector such as a socket adaptor or a wireless connection such as an inductive coil.

[0011] Preferably, the controller is further configured to determine a state of charge for the replaceable battery, wherein the controller is configured to calculate the indication of the average charging voltage based on the determined state of charge. The controller can determine state of charge from a number of different sensors, including by monitoring the current supplied to and discharged from the battery over time. As a result, the calculated indication of the average charging voltage may be based on voltage measurements that are taken only for particular state of charge values. In one example, the average charging voltage may be calculated only for voltages that are determined when the determined state of charge is below a particular threshold value at the start of the charging operation (such as below around 70%). In addition, the average charging voltage may be calculated only for voltages that are determined during a charging operation in which a minimum charge has been transferred to the battery. The minimum transferred charge may be around 20%, around 10% or around 5% in other embodiments, with reference to the nominal charging capacity of the battery. These can be helpful filters, leading to a more accurate determination of compatibility. In an alternative arrangement the calculated indication of the average charging voltage may be based on voltage measurements that are taken only during charging operations that have a minimum temporal duration. For example, the average charging voltage may be measured only if the charging operation lasts at least one or two minutes to ensure that there is enough data for a reasonably accurate determination of compatibility.

[0012] Preferably, the average charging voltage is calculated only for voltages that are determined during a constant current charging phase. During the constant current charging phase, the supplied current is maintained substantially constant and the voltage is variable. This means that different voltage behaviours can be observed for different battery chemistries.

[0013] Preferably, the controller is configured to perform an action after determining that the replaceable battery is incompatible. More preferably, the controller is configured to, after determining that the replaceable battery is incompatible, alert the user that the replaceable battery is incompatible and / or suspend operation of the device entirely. In this way, the controller may alert the user to the safety risk posed by operating the aerosol generating device with an incompatible replaceable battery or may suspend operation of the device entirely. This may improve the safety of the device. In some examples, the alert to the user may be through a sound emitted by a speaker positioned on, or within, the aerosol generating device. In other examples, the alert may be a visual indication and displayed on a screen positioned on an exterior of the aerosol generating device, or a vibration generated by a haptic transducer.

[0014] Preferably, the aerosol generating device further comprises a temperature sensor, and the controller is configured to determine whether the replaceable battery is compatible or incompatible only when a measured temperature is above a predetermined minimum threshold temperature and / or below a predetermined maximum threshold temperature. Temperature, in this context, may be the ambient temperature of the battery housing, which may be an indirect measurement of battery temperature. Battery temperature may influence the charging characteristics of the replaceable battery and, as a result, determining the compatibility of the battery only when the temperature is above a threshold value may lead to a more accurate determination of compatibility. Ensuring that the temperature is also below a threshold may further increase the accuracy with which battery compatibility is determined.

[0015] Preferably, the controller is configured to receive, from the sensor, a measured indication of an initial charging voltage at the beginning of the charging operation and determine whether the replaceable battery is compatible or incompatible only when the indication of the initial charging voltage is below a threshold voltage. In one example, the threshold voltage may be around 3.8V. It has been found that the charging voltage increases throughout the charging operation. By performing the determination of whether the battery is compatible only when the initial charging voltage is below the threshold it is possible to focus on charging operations that do not start at too high a state of charge. It has been found that this can lead to more accurate measurements of the average voltage and, therefore, a more accurate determination of compatibility.

[0016] Preferably the controller is configured to determine the indication of the average charging voltage over a plurality of charging cycles. Further, the controller may be configured to determine that the replaceable battery is compatible only when the indication of the average charging voltage is above the compatibility threshold and there have been a minimum number of charging operations. In this way, the average charging voltage can be established across a number of charging cycles, which improves the accuracy of the determination of the average because it increases the number of observations of the charging voltage at different state of charge values. In this way, the results of determining if the battery is compatible or incompatible can be verified over multiple charging cycles. This may lead to a more accurate determination of compatibility. The aerosol generating device may be placed into an operable state only temporarily until a minimum number of charging operations have been performed overwhich the indication of the average charging voltage is above the compatibility threshold. In some examples, the user may receive an indication (perhaps a visual indication on a screen) that the device is in an operable state only temporarily, until the replaceable battery has been determined to be compatible over the minimum number of charging operations. The temporarily operable state may be an operable state with limited functionality in which one or more functions are disabled, in comparison to a fully operable state. In another arrangement, the temporarily operable state may share all of the functionality of the fully operable state, but the device may be rendered inoperable if the battery is not determined to be compatible within a predetermined period of time or within a predetermined number of charging cycles.

[0017] Preferably, determining that the replaceable battery is compatible indicates a compatible battery chemistry of the replacement battery. In this way, it can be determined whether the replacement battery has the preferred properties of the compatible battery chemistry. Batteries with a preferred chemistry may have higher energy density than batteries with other chemistries, which may in-turn allow the aerosol generating device to operate for longer. These batteries may also have a higher power density. Preferred battery chemistries may operate at a higher voltage, which means that they can deliver a comparable power with a smaller current; operating with a smaller current can mean lower heat losses and longer life for all components and interfaces involved in the power flow from the battery to the heater. In some examples of the invention, the preferred battery chemistry may be Lithium Cobalt Oxide (LCO) which is a cathode-based lithium- ion battery. In a further aspect of the invention, there is provided a method for verifying a compatibility of a replaceable battery in an aerosol generating device, the method comprising the steps of, during a charging operation: receiving a charging voltage at the aerosol generating device; receiving a plurality of measured indications of the charging voltage from a sensor; calculating an indication of an average charging voltage based on the plurality of measured indications of the charging voltage; determining that the replaceable battery is compatible if the indication of the average charging voltage is above a compatibility threshold; and determining that the replaceable battery is incompatible if the indication of the average changing voltage is below the compatibility threshold.

[0018] According to another aspect of the present invention there is provided an aerosol generating device, comprising: a replaceable battery; a sensor configured to measure an indication of a charging voltage during a charging operation; and a controller configured to, during the charging operation: calculate an estimated state of charge of the replaceable battery; receive a measured indication of the charging voltage from the sensor; calculate a threshold based on the estimated state of charge; determine that the replaceable battery has a compatible battery chemistry if the measured indication of the charging voltage is above the calculated threshold; and determine that the replaceable battery has an incompatible battery chemistry if the indication of the changing voltage is below the calculated threshold.

[0019] In this way, the aerosol generating device can calculate a dynamic threshold based on the determined characteristic of the replaceable battery. This can be used to perform a rapid estimation of the battery chemistry. The determined characteristic of the replaceable battery may be an estimated state of charge. Therefore, the charging voltage can be compared against the calculated threshold for a particular value of state of charge. This technique may be used in circumstances where the state of charge can be estimated with a reasonable degree of accuracy. The state of charge may be estimated by monitoring the flow of charge into or out of the battery starting from an initial known state of charge. The controller may be configured initially to permit charging up to a known state of charge, which may be a fully charged state so that state of charge can be monitored. Similarly, the controller may be configured to fully discharge the battery initially so that state of charge can be monitored.

[0020] The measured indication of the charging voltage may be a single voltage measurement during a normal charging operation. In this way, the verification method can be performed quickly during standard charging of the battery.

[0021] According to another aspect of the invention there is provided a method for verifying a compatibility of a replaceable battery in an aerosol generating device, the method comprising the steps of, during a charging operation: receiving a charging voltage at the aerosol generating device; receiving a measured indication of the charging voltage from a sensor; calculating a threshold based on a determined characteristic of the replaceable battery; determining that the replaceable battery is compatible if the measured indication of the charging voltage is above the calculated threshold; determining that the replaceable battery has a compatible battery chemistry if the measured indication of the charging voltage is above the calculated threshold; and determining that the replaceable battery has an incompatible battery chemistry if the indication of the changing voltage is below the calculated threshold.

[0022] In a yet further aspect of the invention there is provided a computer readable memory medium comprising executable instructions which, when executed by a computer, cause the computer to perform method steps as outlined above.

[0023] BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 depicts a schematic view of an aerosol generating device;

[0025] Figure 2 depicts a graph comparing the charging characteristics between two batteries of different battery chemistries; Figure 3 outlines a method performed by a controller during a charging operation in order to determine whether a battery is compatible or incompatible with the aerosol generating device; and

[0026] Figure 4 outlines another method performed by a controller during a charging operation in order to determine whether a battery is compatible or incompatible with the aerosol generating device.

[0027] DETAILED DESCRIPTION

[0028] Figure 1 depicts a schematic view of an aerosol generating device 100. The aerosol generating device 100 comprises a battery housing 110 within which a cavity is formed and configured to receive a replaceable battery 112. The battery 112 can be inserted into the battery housing 110 and can further be removed and replaced with a new battery. Charging equipment 114, which in the embodiment shown is a charging cable with a device end 114a and a socket end 114b, can interface with the battery housing 110 through a charging port 116 positioned on the exterior of the battery housing 110. The charging equipment 114 can draw power from a power grid, through the socket and socket end 114b, and transfer it to the charging port 116. The battery housing 110 comprises circuitry (not shown) which is configured to transfer power from the charging port 116 in order to charge the battery 112. In embodiments not shown, the charging equipment 114 may comprise an induction coil to enable wireless charging.

[0029] The aerosol generating device 100 further comprises a controller 120 which may be a microcontroller, a microprocessor or a charging integrated circuit (IC). The controller 120 may be provided with an auxiliary power source (not shown) or receive power from the battery 112. The controller 120 is in communicative connection with a voltage sensor 122 and a temperature sensor 128. In the embodiment shown, the voltage sensor 122 is a voltmeter and the temperature sensor 128 is a thermocouple. The voltmeter 122 is positioned across the terminals of the replaceable battery 112 such that it measures the voltage across the battery 112. The thermocouple 128 is positioned within the battery housing 110. The thermocouple 128 is positioned proximal to the battery 112, and, therefore, indirectly measures its temperature. The controller 120 utilises the measurements received from the sensors 122-128 in order to determine a battery chemistry of the battery 112. A dedicated battery fuel gauge (not shown) can be provided for determining or estimating the state of charge (SOC) of the battery 112 based on a number of measured parameters.

[0030] Figure 2 depicts a graph comparing the charging characteristics of two batteries of different battery chemistries: Lithium nickel manganese cobalt oxides (NMC) and Lithium cobalt oxide (LCO). An x-axis of the graph of Figure 2 shows the capacities of the NCM and the LCO batteries in mAh during a charging operation. A y-axis of the graph of Figure 2 shows a charging voltage being delivered to the batteries during the charging operation, which is dependent on battery capacity. In particular, Figure 2 shows a realisation made by the present inventors, where, during a charging operation, it is observed that the charging voltage of the LCO battery remains higher than the charging voltage of the NCM battery. In this sense, the mean charging voltage of the LCO battery is greater than the mean charging voltage of the NCM battery, when measured over the charging operation. In fact, it has been observed that the mean charging voltage of the LCO battery is greater than the mean charging voltage of the NCM battery across any given interval during the charging operation, except for intervals containing the start and the end of the plot shown in Figure 2.

[0031] A charging operation generally involves two distinct phases: a constant current charging phase (CC-mode) and a constant voltage charging phase (CV-mode). The constant current charging phase is at the start of the charging operation, and the constant voltage charging phase is at the end of the charging operation. In the constant current charging phase, the charging current is maintained substantially constant and the charging voltage is generally increasing. In the constant voltage charging phase the charging voltage is maintained substantially constant and the charging current decreases towards a cutoff value, which marks the end of the charging period. The charging voltages plotted in Figure 2 were determined substantially during the constant current charging phase, and the end of the plot is close to the end of the constant current charging phase and the beginning of the constant voltage charging phase.

[0032] Figure 3 outlines a method performed by the controller 120 during the charging operation in order to determine whether the battery 112 is compatible or incompatible with the aerosol generating device 100. In particular, the method determines a battery chemistry of the battery 112, by analysing the mean charging voltage across a given interval. The battery chemistry indicates whether the battery 112 is of a particular type intended for use in the aerosol generating device 100, or whether it is not of the type intended for use in the aerosol generating device 100. In the former case, the battery 112 is considered to be “compatible” and in the latter case, the battery 112 is considered to be “incompatible”.

[0033] The battery intended for use in the aerosol generating device 100 has a LCO battery chemistry. Therefore, a compatible battery will exhibit the charging characteristics shown by the LCO curve in Figure 2 during a constant current charging phase and, accordingly, the method of Figure 3 determines whether the data received from the sensors 122-128 are indicative of the LCO curve. The method first determines, at step 300, that a new charging cycle has begun. A new charging cycle can be determined by detecting the presence of a charging voltage using the voltmeter 122. Once a charging cycle has been detected, the method determines that battery 112 has an initial state of charge that is below 70% at step 302 of the method. As can be appreciated from Figure 2, the differences between the charging voltages of LCO and NCM batteries are more difficult to distinguish at higher state of charge values, and therefore it is helpful to establish a minimum initial state of charge, which is taken in this example to be 70%. The person skilled in the art will appreciate that different minimum initial state of charge values may be chosen depending on the preferred implementation. To perform this check, the controller 120 determines a state of charge (as a percentage of the nominal capacity) of the battery 112. This calculation can be performed in a number of different ways. In one example, the controller 120 monitors the accumulated charge during a given charging event by integrating the charging current during the charging period. In other arrangements a dedicated battery fuel gauge can gauge the state of charge so that this can be compared with the minimum initial state of charge.

[0034] The controller 120 performs further checks in order to ensure the validity of the charging voltage measurement received from the voltmeter 122. In particular, the temperature of the battery 112 can influence charging voltage measurements, and so the controller 120 thereby uses data from the thermocouple 128 to determine whether the temperature is within a given range. Specifically, in step 304, the controller 120 verifies that the temperature is between 15°C and 40°C. In an alternative embodiment, the data may be considered invalid if a change in temperature over a given time period is greater than 3°C. As a final optional check to ensure the validity of the charging voltage measurements, the controller 120, in step 306, determines whether the charging voltage received from the voltmeter 122 is between 3.5V and 3.8V. At each step 302-306, if the measurements are not within their expected ranges the controller 120 will loop, and thereby continue to perform steps 302, 304, and 306, until the data is within the intended ranges.

[0035] Once the data has been verified, the controller 120 begins monitoring the charging voltage at step 310. The charging voltage is monitored during a period in which the state of charge increases by at least 10% in terms of the overall nominal capacity, and at least 20% in preferred embodiments. Thus, a sustained period of charging is undertaken at step 310. In other embodiments, rather than monitoring the state of charge for a particular increase, the temporal duration of the charging operation may be monitored for a minimum period of at least 1-2 minutes. In some embodiments the monitoring may be stopped after the state of charge has increased by, say, 10%; in other embodiments the monitoring may continue for longer, and perhaps for the full duration of the charging period.

[0036] At step 312 any outliers are removed from the charging voltage measurements. In the implementation shown in Figure 3, outliers are determined by comparing the difference between successive voltage measurements received from the voltmeter 122, and discarding the older of the two points if the difference exceeds 10mV. Once outliers have been removed, the controller 120 increases a counter at step 314. The counter is initially set to zero and is increased by one after each period of measuring the charging voltage, which normally corresponds to one charging cycle. At step 316 the controller 120 checks whether the counter is equal to five, which would indicate that at least five charging operations have been performed. If the counter remains less than five then the controller 120 sets the device so that it operates in a temporarily operable state, and the flow chart returns to step 300 to await the beginning of the next charging cycle.

[0037] In the temporarily operable state the aerosol generating device 100 may display a warning to indicate that the battery 112 has not been fully validated. In another configuration the aerosol generation device 100 may be rendered inoperable should the counter fail to reach five within a predetermined time period (such as one week) after the counter has reached one.

[0038] Once the controller 120 has established that the counter is equal to five the controller calculates a mean charging voltage at step 320. The mean charging voltage is calculated using the following equation: wherein, n represents the number of voltage measurements received from the voltmeter 122 over five discrete charging cycles. As will be appreciated, in any individual charging cycle the calculated mean charging voltage would be dependent on a number of parameters, which includes the battery chemistry as well as the duration of the charging period, the state of charge of the battery at the beginning and the state of charge at the end of the charging period. For this reason, the mean voltage in a single charging cycle would not necessarily be sufficient to unambiguously determine the battery chemistry. The present technique calculates an average charging voltage over at least five charging cycles. It has been found that this generally provides a range of different voltage measurements for different state of charge values. Over five charging events it is possible to distinguish more readily between different battery chemistries. In the presently described method the controller 120 is configured to calculate the mean charging voltage. The skilled person would, however, appreciate that it would be possible to calculate other mathematical representations of an average. For example, with enough measurements it may be possible to distinguish between different battery chemistries using the median voltage. It may also be possible to calculate a weighted mean with different weights being applied to voltage measurements depending on other parameters, like the state of charge. Similarly, in an alternative implementation of the method, a property of the battery 112 related to the mean charging voltage could be used in order to determine compatibility, instead of the mean charging voltage; for example, the mean charging current through a fixed resistor may be used, since current and voltage are proportional to one another in a resistor with a fixed resistance.

[0039] At step 322, the controller 120 determines whether the mean charging voltage is greater than or equal to 3.85V, which is a value that has been found by the present inventors to differentiate an LCO battery chemistry from other battery chemistries. If the mean charging voltage is found to be less than 3.85V, the battery 112 is considered to be incompatible and the user is alerted accordingly at step 340. In these circumstances the controller 120 may render the device inoperable to prevent further use with an incompatible battery. The threshold of 3.85V has been determined empirically based on observations and measurements. In practice, a different value could be chosen, as would be appreciated by the skilled person based on the different behaviour of charging voltages for different battery chemistries, as illustrated in Figure 2. A different value would also be selected, depending on the battery chemistries that need to be distinguished from one another.

[0040] Alerting the user may include displaying a message on a digital screen positioned on an exterior housing of the aerosol generating device 100, and / or may include producing a sound from a speaker located on an exterior surface of, or within, the aerosol generating device 100. If the mean voltage is determined to be greater than 3.85V then the controller 120 is able to validate the battery as compatible at step 350. At step 352 the device can continue to be operated in a fully operable state. .

[0041] In the present technique at step 316 the controller 120 determines whether the counter is equal to 5. The setting used at this step is dependent on the accuracy required for the determination of battery compatibility. It has been found that the battery chemistry can be determined with higher accuracy with larger amounts of voltage data, gathered during charging operations. Therefore, the counter setting may be increased beyond five, if required by the circumstances. Similarly, a lower counter setting can provide a more coarse estimation of battery chemistry, which may be suitable in other embodiments. Even a single charging cycle can provide an estimation of battery chemistry and consequently an estimation regarding battery compatibility, which may be useful in some scenarios. For the present technique it has been found that a counter setting of five provides a reasonable balance between speed and accuracy of the determination of battery compatibility.

[0042] The charging voltage is described here as the voltage measured by the voltmeter 122, which is the voltage measured across the battery 120 terminals. This may be referred to as the quasi open-circuit voltage (qOCV). This is just one technique for measuring the charging voltage during a charging operation. In another technique, the voltmeter may be positioned at the charging port 116 to directly measure the supplied voltage.

[0043] Figure 4 outlines another method that can be performed by the controller 120. At step 400 the controller 120 detects that a new charging cycle has begun. This can involve the detection of a charging voltage using the voltmeter 122. The method may involve some preliminary steps, like those shown in Figure 3, to determine that the temperature is in the correct range and that the battery voltage is within a desirable range. At step 402 the controller 120 calculates an estimated state of charge of the battery 112. The skilled person will appreciate that the accuracy with which state of charge can be determined for a replaceable battery 112 that initially has unknown properties will depend on the circumstances. It is evident from Figure 2 that it is not possible to determine state of charge based only on the charging voltage because the charging voltage has been found to be different for different state of charge values depending on the battery chemistry. A dedicated battery fuel gauge can be provided for determining or estimating the state of charge, but even this may require some time for observations to be performed. The method of Figure 4 is intended to function only when the state of charge can be estimated with reasonable accuracy. This can be achieved, in one scenario, by monitoring evolution in the state of charge from initial known state of charge value. One example known state of charge starting condition is a fully charged battery, where state of charge is 100%. A second example is fully discharged battery where state of charge is 0%. The controller 120 can monitor changes from the initial state of charge value by integrating current flow into and out of the battery in units of mAh during charging and discharging events. The initial known state of charge value may have a predefined validity period, which may be around one day. Similarly, an estimated state of charge based on integrated current flow during charging and discharging events may only be treated as valid for a certain period of time, or a certain value of integrated current flow, based on accumulated errors in the measurements.

[0044] At step 404 the controller 120 calculates a voltage threshold based on the estimated state of charge, which may be expressed as a percentage or in units of mAh. In one example, this can be done by referring to a look-up table that is held in a data storage unit. Alternatively, a function, such as a polynomial function, may provide a relationship between state of charge and the threshold. With reference to Figure 2, a look-up table may be provided as follows, in a simple example:

[0045] The look-up table provides a threshold that can be used to distinguish between voltage measurements at different state of charge values for different battery chemistries. Of course, different voltage threshold values may be used for distinguishing between different battery chemistries. The threshold values may also need to be varied based on the maximum charging current that is available. Other factors such as temperature may also an effect on the threshold values in the look-up table.

[0046] The figures in the look-up table may be appropriate in a particular example based on aerosol generating devices that use a liquid-based aerosol precursor. Other kinds of aerosol generating device would use batteries with other properties. For example, an aerosol generating device based on heated tobacco (a heat-not-burn device) may use a battery having a capacity of around 2800mAh.

[0047] At step 406 the charging voltage is measured using the voltmeter 122. At step 408 the charging voltage is compared with the threshold calculated at step 404. If the voltage is above the threshold, then the battery is determined to be compatible at step 412 because it is determined that the battery chemistry is of a desirable type. Otherwise, the battery is determined to be incompatible at step 410 because the battery chemistry is not supported. In these circumstances an error message can be displayed or the device can be rendered inoperable by the controller 120.

[0048] The skilled person will appreciate that it would be possible to perform other mathematical comparisons at step 408 to distinguish between batteries that are compatible or incompatible. In one example, it would be possible to calculate an inverse of the threshold and the voltage measurements so that the battery is determined to be compatible when the inverse of the charging voltage is below a threshold. Figure 4 illustrates a method for determining battery compatibility in circumstances where the controller 120 is able to estimate the state of charge of the battery at step 402 with reasonable accuracy. This can be achieved by initially charging the battery to a fully charged state and then using an ammeter to monitor the flow of current into or out of the battery during charging or discharging operations. Similarly, the battery may be initially fully discharged so that state of charge can be estimated by monitoring, using an ammeter, the flow of charge into or out of the battery.

[0049] The method shown in Figure 4 may offer an accelerated method for determining compatibility and battery chemistry in comparison with Figure 3, which involves measurements of charging voltage over several charging cycles. The controller 120 may be configured to select between the methods of Figures 3 and 4 depending on the estimated accuracy of a state of charge determination.

Claims

CLAIMS1. An aerosol generating device, comprising: a replaceable battery; a sensor configured to measure an indication of a charging voltage during a charging operation; and a controller configured to, during the charging operation: receive a plurality of measured indications of the charging voltage from the sensor; calculate an indication of an average charging voltage based on the plurality of measured indications of the charging voltage; determine that the replaceable battery is compatible if the indication of the average charging voltage is above a compatibility threshold; and determine that the replaceable battery is incompatible if the indication of the average changing voltage is below the compatibility threshold.

2. The aerosol generating device of claim 1 , wherein the controller is configured to determine a state of charge for the replaceable battery, and the controller is configured to calculate the indication of the average charging voltage based on the determined state of charge.

3. The aerosol generating device of claim 2, wherein the controller is configured to determine whether the replaceable battery is compatible or incompatible only when the determined state of charge is below a threshold value at the beginning of the charging operation.

4. The aerosol generating device of any preceding claim, wherein the controller is configured to, after determining that the replaceable battery is incompatible, alert the user that the replaceable battery is incompatible and / or suspend operation of the device entirely.

5. The aerosol generating device of any preceding claim, further comprising a temperature sensor, and wherein the controller is configured to determine whether the replaceable battery is compatible or incompatible only when ameasured temperature is above a predetermined minimum threshold temperature and / or below a predetermined maximum threshold temperature.

6. The aerosol generating device of any preceding claim, wherein the controller is configured to: receive, from the sensor, a measured indication of an initial charging voltage at the beginning of the charging operation, and determine whether the replaceable battery is compatible or incompatible only when the indication of the initial charging voltage is below a threshold voltage.

7. The aerosol generating device of any preceding claim, wherein the controller is configured to determine the indication of the average charging voltage over a plurality of charging cycles.

8. The aerosol generating device of claim 7, wherein the controller is configured to: determine that the replaceable battery is compatible only when the indication of the average charging voltage is above the compatibility threshold and a minimum number of charging operations have been completed.

9. The aerosol generating device of any preceding claim, wherein determining that the replaceable battery is compatible indicates a compatible battery chemistry of the replaceable battery.

10. The aerosol generating device of any preceding claim, wherein the average charging voltage is calculated only for voltages that are determined during a charging operation in which a minimum charge has been transferred to the replaceable battery.

11. A method for verifying a compatibility of a replaceable battery in an aerosol generating device, the method comprising the steps of, during a charging operation: receiving a charging voltage at the aerosol generating device; receiving a plurality of measured indications of the charging voltage from a sensor; calculating an indication of an average charging voltage based on the plurality of measured indications of the charging voltage; determine that thereplaceable battery is compatible if the indication of the average charging voltage is above a compatibility threshold; and determining that the replaceable battery is incompatible if the indication of the average changing voltage is below the compatibility threshold.

12. An aerosol generating device, comprising: a replaceable battery; a sensor configured to measure an indication of a charging voltage during a charging operation; and a controller configured to, during the charging operation: calculate an estimated state of charge of the replaceable battery; receive a measured indication of the charging voltage from the sensor; calculate a threshold based on the estimated state of charge; determine that the replaceable battery has a compatible battery chemistry if the measured indication of the charging voltage is above the calculated threshold; and determine that the replaceable battery has an incompatible battery chemistry if the indication of the changing voltage is below the calculated threshold.

13. The aerosol generating device of claim 12, wherein the controller is configured to calculate the threshold based on an estimated state of charge of the replaceable battery.

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