A method of determining the maximum allowable temperature of the traction battery of a vehicle with electric powertrain during use of the vehicle

Abstract

A method (10) of determining the maximum allowable temperature of the cells of a traction battery of a vehicle with electric powertrain during use of the vehicle is described. A first value of maximum allowable temperature (TBatt_Cell_Max_Drv_Tgt) associated to a currently selected drive mode is determined (102) as a function of the value of a first input parameter (DriveMod) that indicates the currently selected drive mode and the value of a second input parameter (SOC) that indicates the state of charge of the traction battery. An actual value of maximum allowable temperature (TBatt_Cell_Max_Tgt) is determined (104) as a function of the first value of maximum allowable temperature (TBatt_Cell_Max_Drv_Tgt), the value of the first input parameter (DriveMod), and the values of one or more further input parameters. The further input parameters are selected amongst: a third input parameter (TurtleModeActive) indicative, if asserted, of a request for activation of an energy-saving mode of the vehicle; a fourth input parameter (FastChrgPrecondActive) indicative, if asserted, of the activation of a thermal conditioning function of the traction battery; a fifth input parameter (TBatt_Cell_Max_FCP_Tgt) indicative of a second value of maximum allowable temperature (TBatt_Cell_Max_FCP_Tgt) associated to the thermal conditioning function; a sixth input parameter (TAmb) indicative of ambient temperature; and a seventh input parameter (ΔtEnd_Mission) indicative of the remaining duration of the current driving mission.

Description

[0001] “A method of determining the maximum allowable temperature of the traction battery of a vehicle with electric powertrain during use of the vehicle”

[0002] ****

[0003] TEXT OF THE DESCRIPTION

[0004] Field of the invention

[0005] The present invention relates to vehicles with electric powertrain, particularly BEV-type (Battery Electric Vehicle) or HEV-type (Hybrid Electric Vehicle) vehicles, equipped with a traction battery that stores the chemical energy required for the movement of the vehicle.

[0006] The invention has been developed with reference to the management of the temperature of the cells of the traction battery of the vehicle during use of the vehicle (i.e. , in driving conditions). In particular, the invention relates to a method of determining a value of the maximum allowable temperature of the cells of the traction battery in driving conditions.

[0007] Prior art

[0008] In an electric or hybrid traction vehicle, the temperature of the cells of the traction battery influences the maximum electrical power that can be absorbed by the battery during charging or delivered by the battery during discharging, and also the reserve of thermal capacity of the battery that can be used before reaching a critical high temperature (i.e., the amount of thermal energy that can be absorbed by the battery before reaching a critical temperature). It will be noted that in the present disclosure reference is made to the chemical energy stored by the battery and the thermal energy stored by the battery. Chemical energy is the useful energy stored through a reversible charging process by the battery cells, which can be supplied by the battery in the form of electric current to power the vehicle loads (both propulsive and non-propulsive). Thermal energy is instead the energy stored following an increase in the temperature of the battery pack, which cannot be usefully transformed into electric current, and which is essentially destined to be dissipated as heat.

[0009] Cooling of the battery (carried out by one or more chiller devices provided in the vehicle) involves significant energy consumption. The reserve of thermal capacity of the battery before the critical temperature is reached can be used to reduce the consumption of electric energy due to thermal conditioning (cooling) of the battery in certain driving missions. In other words, substantially, the intervention of the battery cooling system can be eliminated or reduced by exploiting the fact that the battery can absorb a certain amount of thermal energy before reaching a critical temperature. In other driving missions, aimed at maximum vehicle performance (e.g., “race” mode), the reserve of thermal capacity of the battery can be managed to avoid thermal derating, since in such missions the maximum cooling power of the battery is usually lower than the power dissipated as heat (i.e. , in other words, the cooling system removes less heat than that which is generated, per unit of time).

[0010] In known electric or hybrid vehicles, during use (i.e., in driving conditions) an algorithm defines a single value of the maximum allowable temperature of the cells of the traction battery. Defining a single value of maximum allowable temperature, valid in all driving conditions, does not allow for the best management of the balance between obtaining maximum power performance from the battery, using the cooling system to cool the battery, and exploiting the reserve of thermal capacity of the battery to avoid thermal derating.

[0011] Therefore, the need to develop an algorithm to determine the maximum allowable temperature of the cells of the traction battery of the vehicle also as a function of different driving conditions is felt in the art.

[0012] Object of the invention

[0013] The object of the invention is to solve the above-mentioned technical problem. In particular, the object of the invention is to provide a method of determining a value of the maximum allowable temperature of the cells of a traction battery that, also as a function of the driving “mission” requested by the driver, allows obtaining a good balance between the maximum power performance obtainable from the battery, the energy spent for cooling the battery, and the exploitation of the reserve of thermal capacity of the battery to avoid thermal derating. Summary of the invention

[0014] The object of the invention is achieved by a method having the features forming the subject of the claims that follow, which form an integral part of the technical teaching provided herein in relation to the invention.

[0015] The method can be implemented by one or more electronic control units of a vehicle (e.g., by a control unit of the Battery Management System (BMS), and / or by a control unit of the powertrain of the vehicle).

[0016] Brief description of the figures

[0017] The invention will now be described with reference to the attached figures provided purely by way of non-limiting example, in which:

[0018] Figure 1 is a block diagram illustrating the phases of a method of determining a value of the maximum allowable temperature of the cells of the traction battery in driving conditions, according to one or more embodiments of the present disclosure;

[0019] Figures 2 to 4 are block diagrams illustrating some steps of a phase of the method of determining the value of the maximum allowable temperature of the cells of the traction battery in driving conditions, in particular a phase that allows to determine a value of maximum allowable temperature associated to the currently used drive mode;

[0020] Figures 5 to 9 are block diagrams illustrating some steps of another phase of the method of determining the value of the maximum allowable temperature of the cells of the traction battery in driving conditions, in particular a phase that allows to apply corrective factors to the value associated to the drive mode to determine the actual value of the maximum allowable temperature of the cells of the battery; and

[0021] Figure 10 is a block diagram summarizing the phases of a method of determining the value of the maximum allowable temperature of the cells of the traction battery in driving conditions, according to one or more embodiments of the present disclosure.

[0022] Detailed description

[0023] As mentioned, the invention relates to a method that has the object of determining the value of the maximum allowable temperature of the cells of the traction battery of a vehicle in different driving conditions and as a function of the driving mission requested by the driver. The method therefore implements a control algorithm of the battery management system during the use phase of the vehicle, and can be implemented by a control unit of the battery management system (or BMS) and / or by a control unit of the powertrain of the vehicle.

[0024] The different driving missions that can be requested (selected) by the driver are characterized by respective values of nominal propulsive power of the vehicle and maximum duration of the performance. For example, a “race” type driving mission will be characterized by a high power deliverable for a short period of time, while a touring driving mission will be characterized by a lower propulsive power deliverable for a longer period of time. Furthermore, the different driving missions can also envisage different time courses of the thermal conditioning function of the battery, and in particular they can include different time trends with regard to the reduction of the electrical energy consumption by the thermal conditioning system of the battery in order to increase the autonomy of the vehicle. The value of the maximum allowable temperature of the cells of a traction battery influences these aspects of the vehicle, and it is therefore desirable to be able to define this value of the maximum allowable temperature to obtain a good trade-off or balance also as a function of the driving mission required by the driver of the vehicle.

[0025] As illustrated in the block diagram of Figure 1 , the method 10 can substantially comprise two phases indicated by the references 102 and 104. In the phase 102, further described below, a value of maximum allowable temperature TBatt_ceii_Max_Drv_Tgt associated to the currently used drive mode is determined instant by instant, as a function of the values of a first input parameter Drive Mod which indicates the current drive mode selected by the driver of the vehicle, and a second input parameter SOC which corresponds to the state of charge of the traction battery. In the phase 104, further described below, an actual value of the maximum allowable temperature TBatt_ceii_Max_Tgt is determined instant by instant as a function of the value TBatt_ceii_Max_Drv_Tgt associated to the drive mode computed in phase 102, the value of the input parameter DriveMod, and the values of further (corrective) input parameters TAmb, TurtleModeActive, AtEndjviission, FastChrgPrecond Active and TBatt_ceii_Max_pcp_Tgt which will be further described below. Substantially, therefore, the operation block 104 carries out a correction or adjustment of the value TBatt_ceii_Max_Drv_Tgt associated to the drive mode computed in phase 102.

[0026] The functioning of the operation block 102 for determining the value of maximum allowable temperature TBatt_ceii_Max_Drv_Tgt associated to the drive mode will now be described with reference to Figures 2 to 4.

[0027] In particular, as illustrated in Figure 2, the value of maximum allowable temperature TBatt_ceii_Max_Drv_Tgt associated to the drive mode can be determined by choosing, as a function of the parameter DriveMod, one of a plurality of temperature values associated to the different drive modes. For example, in Figure 2, six different values are indicated T Batt_Cell_Max_Drv_ 1_Tgt, T Batt_Cell_Max_Drv_2_ Tgt, T Batt_Cell_Max_Drv_3_Tgt, Batt_Cell_Max_Drv_4_Tgt, Batt_Cell_Max_Drv_5_Tgt, Batt_Cell_Max_Drv_6_Tgt, assuming that the vehicle is equipped with six different drive modes from which the driver can choose. Obviously, in other embodiments the vehicle may provide more or less than six drive modes, and therefore more or less than six temperature values may be present, which will be generically indicated with TBatt_ceii_Max_Drvj_ Tgt with i = 1 , ... , N (N = 6 in the example considered here).

[0028] As exemplified in Figure 3, the ithtemperature value TBatt_ceii_Max_Drvj_Tgt associated to the ithdrive mode can in turn be determined as a function of one or more respective characteristic maps (e.g., implemented by analytical, piecewise or look-up table functions) as a function of the state of charge SOC. The dependence of the temperature value TBatt_ceti_Max_D^_i_Tgt on the state of charge SOC is qualitatively represented by the graph of block 1021 , which illustrates the trend of the temperature Batt_cett_Max_Drv_i_Tgt as a function of the state of charge SOC (obviously, different drive modes are characterized by different characteristic maps of correlation between SOC and Batt_ceti_Max_Drv_i_Tgt, as will be seen in more detail also with reference to Figure 4). Generally, however, the temperature Batt_ceti_Max_Drv_i_Tgt increases as the state of charge SOC decreases, since for low values of the state of charge, a relaxation of the battery cooling requirement allows to reduce the current consumption by the cooling system, thus increasing the vehicle range (i.e. , the reserve of thermal capacity of the battery is exploited to save energy). Furthermore, for low values of the state of charge SOC it is preferable that the battery temperature is high in order to maintain an adequate level of power deliverable by the battery.

[0029] More specifically, Figure 4 is a graph exemplifying six possible characteristic maps (or correlations) between the temperature TBatt_ceii_Max_Drvj_Tgt (with i = 1 , 6) and the state of charge SOC for six different drive modes. In particular, the curve TBatt_ceii_Max_Drv_i_Tgt (thin solid line) corresponds to a first drive mode aiming at the maximum vehicle range (“max range”), the curve TBatt_ceii_Max_Drv_2_Tgt (thin dotted line) corresponds to a second drive mode aiming at a racing style of driving that maximizes the acceleration of the vehicle over short distances, such as in “drag race” type competitions (“race max boost”), the curve TBatt_ceii_Max_Drv_3_Tgt (thin dotted line) corresponds to a third drive mode aiming at a touring drive mode (“GT”), the curve TBatt_ceii_Max_Drv_4_Tgt (thick solid line) corresponds to a fourth drive mode aiming at a sporty drive mode (“sport”), the curve TBatt_ceii_Max_Drv_5_Tgt (thick dotted line) corresponds to a fifth drive mode aiming at a racing drive mode aiming to complete a fast lap (“race fast lap”), and the curve TBatt_ceii_Max_Drv_6_Tgt (thick dotted line) corresponds to a sixth drive mode aiming at a racing drive mode over a long distance (“race endurance”).

[0030] Therefore, depending on the drive mode DriveMod selected by the driver, the method according to the invention determines the type of driving mission requested by the driver, and determines the temperature value TBatt_ceii_Max_Drvj_Tgt as a function of the state of charge SOC and a map or curve among those exemplified in Figure 4. For drive modes that aim to maximize the vehicle range (e.g., the “max range” mode corresponding to the curve Batt_ceii_Max_Drv_i_Tgt, or the “GT” mode corresponding to the curve Batt_ce / / _Max_Drv_3_rgt), the value of maximum allowable temperature TBatt_ceii_Max_D^_Tgt is about between 38°C and 43°C. These temperature values are high enough to allow the reserve of thermal capacity of the battery to be exploited (limiting as much as possible the activation of the battery cooling system, and the consequent consumption of electrical energy), and at the same time allow not to excessively risk suffering from thermal derating (if the vehicle is driven in a “relaxed” manner, as is typical of these drive modes, and also considering that these drive modes are characterized by a reduced propulsive power which therefore results in a lower heat dissipation) and also not to accelerate the battery ageing phenomena. For drive modes that instead aim to maximize vehicle performance (e.g. the “race max boost” mode corresponding to the curve TBatt_ceii_Max_Drv_2_Tgt or the “race fast lap” mode corresponding to the curve TBatt_ceii_Max_Drv_5_Tgt, or the “race endurance” mode corresponding to the curve TBatt_ceii_Max_Drv_6_Tgt), the value of maximum allowable temperature TBatt_ceii_Max_Drv_Tgt depends on the duration of the required driving mission (which is influenced by the reserve of thermal capacity of the battery) and on the maximum power that can be supplied by the battery.

[0031] As an example, the curves TBatt_ceii_Max_Drv_2_Tgt and TBatt_ceii_Max_Drv_6_Tgt corresponding to the “race max boost” and “race endurance” modes, which have different objectives despite both being raceoriented drive modes, are described in detail here. In the “race max boost” mode, the objective is to immediately obtain the maximum power that can be delivered by the battery (one can think of a “drag race” type application that involves accelerating from a standstill for a duration of about 10 seconds and a total distance of about 400 meters), therefore the reserve of thermal capacity of the battery is less important than the pure battery discharge power. For this reason, the maximum allowable temperature TBatt_ceii_Max_Drv_2_Tgt is quite high (e.g., 42°C) even for high SOC values. In the “race endurance” mode, the objective is to obtain the best lap time in a driving mission that develops over a distance of about 20 km (e.g., a single lap on the Nurburgring track or a few laps in a single race on another track), therefore the respective value of maximum allowable temperature TBatt_ceii_Max_D^_6_Tgt is rather low (e.g., 18°C) for high values of the state of charge SOC (at the beginning of the driving mission) and increases as the state of charge SOC decreases to keep the value of the maximum deliverable power of the battery as constant as possible and consistent with the nominal value of the power deliverable by the battery in this drive mode. In this second case, therefore, the reserve of thermal capacity of the battery is more important than the pure discharge power of the battery.

[0032] The functioning of the operation block 104 for determining the actual value of the maximum allowable temperature TBatt_ceii_Max_Tgt will now be described with reference to Figures 5 to 9.

[0033] In particular, as illustrated in Figure 5, in a first step of the operation block 104 a “raw” value of the maximum allowable temperature TBatt_ceii_Max_Raw_Tgt can be determined by selecting the maximum value amongst: the value of the maximum allowable temperature

[0034] TBatt_ceii_Max_Drv_Tgt associated to the drive mode computed by the operation block 102, a value of the maximum allowable temperature

[0035] TBatt_ceii_Max_Tamb_Tgt associated to the ambient temperature, and a value of the maximum allowable temperature TBatt_ceii_Max_EndMis_ Tgt associated to the duration of the driving mission.

[0036] As exemplified in Figure 6, the value of the maximum allowable temperature TBatt_ceii_Max_Tamb_Tgt associated to the ambient temperature can in turn be determined as a function of one or more respective characteristic maps (e.g., implemented by means of analytical, piecewise or look-up table functions) based on the ambient temperature TAmb, which can be detected by one or more sensors of the vehicle. The dependence of the temperature TBatt_ceii_Max_Tamb_Tgt on the ambient temperature TAmb is qualitatively represented by the graph of block 1041 , which illustrates the trend of the temperature TBatt_ceii_Max_Tamb_Tgt as a function of the temperature TAmb. Generally, the maximum allowable temperature TBatt_ceii_Max_Tamb_Tgt increases as the ambient temperature TAmb increases, until it reaches an upper limit beyond which the maximum allowable temperature TBatt_ceii_Max_Tamb_Tgt remains constant even as the ambient temperature TAmb increases. In particular, the temperature TBatt_ceii_Max_Tamb_Tgt is always kept slightly higher than the temperature TAmb (e.g., about 2°C higher than TAmb) until the limit temperature is reached, which can be about 43°C or 44°C. In this way, waste of energy for cooling the battery is avoided (i.e. , “forcing” of the battery temperature to a temperature lower than the ambient temperature, towards which the battery temperature would tend anyway, is avoided), unless the ambient temperature is higher than the safety limit of about 43°C or 44°C.

[0037] As exemplified in Figures 7 and 8, the value of the maximum allowable temperature TBatt_ceii_Max_EndMis_Tgt associated to the duration of the driving mission can be in turn determined as a function of one or more respective characteristic maps (e.g., implemented by means of analytical, piecewise or look-up table functions) as a function of the expected residual duration AtEndjviission of the driving mission, which represents an input parameter of the method according to the present invention, and two constant parameters TBatt_ceii_Max_EndMis and Gradrempinc which represent, respectively, a maximum acceptable value of battery temperature (e.g., equal to 43°C or 44°C as discussed above) and a time gradient of temperature increase. In particular, the value of the maximum allowable temperature TBatt_ceii_Max_Endiviis_Tgt can be computed as the difference between the constant value TBatt_ceii_Max_EndMis and the product of the remaining duration of the driving mission AtEndjviission and the temperature increase gradient Gradrempinc. In this way, essentially, the value of the maximum allowable temperature TBatt_ceii_Max_EndMis_rgt is further away from the maximum acceptable value TBatt_ceii_Max_EndMis the greater the expected remaining duration of the driving mission, so as to be able to accommodate a battery temperature increase that occurs with a constant gradient equal to Gradrempinc. Figure 8 shows the time evolution of the value of the maximum allowable temperature TBatt_ceii_Max_EndMis_Tgt while the vehicle moves towards the final destination (end of mission, EOM), which essentially implements the following equation:

[0038] As illustrated in Figure 9, in a second step of the operation block 104 the actual value of maximum allowable temperature TBatt_ceii_Max_rgt of the battery cells can be determined by carrying out the following operations.

[0039] A binary variable (or flag) ByPassDrvMod is asserted (e.g., set to ‘1 ’) or de-asserted (e.g., set to ‘0’) as a function of a characteristic map (e.g., implemented by an analytic, piecewise or look-up table function) as a function of the value of the parameter DriveMod that indicates the current drive mode selected by the driver of the vehicle. As an indication, the binary variable (or flag) ByPassDrvMod is asserted when an aggressive drive mode is currently selected in which it is appropriate for the battery to be brought to an optimal temperature that allows for high performance (e.g., in the “sport”, “race max boost”, “race fast lap” and “race endurance” modes), while it is de-asserted when a more relaxed drive mode is currently selected in which it is appropriate to reduce energy consumption to increase the vehicle range (e.g., in the “GT” and “max range” modes). In the first case, where the variable ByPassDrvMod is asserted, the starting base for the computation of the actual value of the maximum allowable temperature TBatt_ceii_Max_Tgt must be the value of maximum allowable temperature TBatt_ceii_Max_Drv_Tgt associated to the drive mode; in the second case, where the variable ByPassDrvMod is de-asserted, the starting base for the computation of the value of the maximum allowable temperature TBatt_ceii_Max_Tgt must be the raw value of the maximum allowable temperature TBatt_ceii_Max_Raw_Tgt. Therefore, the output value from selector S1 is egual to TBatt_ceii_Max_Drv_Tgt if ByPassDrvMod — 1 and is egual to TBatt_Cell_Max_Raw_Tgt if ByPaSSDrvMod=0.

[0040] In the method 10, it is checked whether the input binary variable FastChrgPrecond Active is asserted (true) or de-asserted (false). The fact that the variable FastChrgPrecond Active is asserted indicates that the activation of a pre-conditioning (pre-cooling) of the battery is required in order to perform a fast or ultra-fast charge, while if the variable FastChrgPrecond Active is de-asserted, no pre-conditioning of the battery is required (therefore the value of the input binary variable FastChrgPrecond Active is determined by charging control strategies external to the method according to the present invention). Such variable FastChrgPrecond Active is used to control a second selector S2 such that, if the variable FastChrgPrecondActive is asserted, the output value from selector S2 is equal to a temperature value TBatt_ceii_Max_Fcp_Tgt which is determined by a vehicle charging strategy control algorithm (and which, in the method of the present invention, represents an input parameter), while if the variable FastChrgPrecondActive is de-asserted, the output value from selector S2 is equal to the temperature value passed by selector S1 .

[0041] In the method 10, it is checked whether the input binary variable TurtleModeActive is asserted (true) or de-asserted (false). The fact that the variable TurtleModeActive is asserted indicates that the residual energy in the battery has reached a critically low level (and therefore the vehicle must forcibly operate in an energy-saving mode or “turtle” mode), while if the variable TurtleModeActive is de-asserted, the activation of the energysaving mode is not required (therefore the value of the input binary variable TurtleModeActive is determined by battery control strategies external to the method according to the present invention). Such variable TurtleModeActive is used to control a third selector S3 such that, if the variable TurtleModeActive is asserted, the output value from selector S3 is equal to a temperature value TBatt_ceii_Max_Trti_Tgt which is the value of maximum allowable temperature during energy-saving mode (and which, in the method of the present invention, is a constant value high enough - equal to for example 48°C - to exploit the reserve of thermal capacity of the battery to the maximum and delay the activation of the battery cooling system as much as possible, while remaining within the critical temperature limits allowed by the battery cell supplier), while if the variable TurtleModeActive is de-asserted, the output value from selector S3 is equal to the temperature value passed by selector S2.

[0042] Therefore, as can be seen from the preceding description, the method 10 described here to determine the value of the maximum allowable temperature TBatt_ceii_Max_Tgt of the battery cells is substantially divided into two phases, as also exemplified in the block diagram of Figure 10: in phase 102 a value of the maximum allowable temperature TBatt_ceii_Max_Drv_Tgt associated to the currently used drive mode is defined instant by instant, taking into account the current drive mode and the battery charge state; and in step 104, an actual value of the maximum allowable temperature TBatt_ceii_Max_Tgt is defined instant by instant, taking into account the value of maximum allowable temperature associated to the current drive mode and other corrective parameters that take into account the ambient temperature, the estimated remaining duration of the driving mission, the need to pre-condition the battery in view of a rapid charging phase, and / or the need to limit the thermal conditioning of the battery as much as possible to save energy in an energy-saving mode or “turtle mode”.

[0043] Thanks to the present invention, it is possible to improve the temperature management of the cells of a traction battery also as a function of the drive mode selected by the driver, which allows: obtaining the maximum power deliverable by the battery in the case of sporting maneuvers of very short duration (e.g., accelerations over a short distance in a “drag race” scenario), and / or increasing the duration and consistency of the vehicle performance without reducing the nominal propulsive power in a given drive mode, and / or increasing the vehicle range using less energy for cooling the battery, fully exploiting the reserve of thermal capacity of the battery while always remaining within the safety limits of the battery, and / or the possibility of maintaining a small energy reserve to power the basic functions of the vehicle in the event that the activation of the energy-saving mode is required when the battery charge level is extremely low, also in this case always remaining within the safety limits of the battery.

[0044] Of course, the details of construction and the embodiments may be varied widely with respect to what is described and illustrated without departing from the scope of the invention as defined by the attached claims.

Claims

CLAIMS1. A method (10) of determining the maximum allowable temperature of the cells of a traction battery of a vehicle with electric powertrain during use of the vehicle, the method comprising: determining (102) a first value of maximum allowable temperature (TBatt_ceii_Max_Drv_Tgt) associated to a currently selected drive mode, as a function of the value of a first input parameter (DriveMod that indicates the currently selected drive mode and the value of a second input parameter (SOC) that indicates the state of charge of said traction battery; and determining (104) an actual value of maximum allowable temperature (TBatt_ceii_Max_Tgt) as a function of said first value of maximum allowable temperature (TBatt_ceii_Max_Drv_Tgt), the value of said first input parameter (DriveMod), and the values of one or more further input parameters selected amongst:- a third input parameter (TurtleModeActive) indicative, if asserted, of a request for activation of an energy-saving operation mode of the vehicle;- a fourth input parameter (FastChrgPrecondActive) indicative, if asserted, of the activation of a thermal conditioning function of said traction battery and a fifth input parameter ( TBatt_ceii_Max_FCP_Tgt) indicative of a second value of maximum allowable temperature ( TBatt_ceii_Max_Fcp_Tgt) associated to said thermal conditioning function;- a sixth input parameter (TAmb) indicative of ambient temperature; and- a seventh input parameter (AtEndjviission) indicative of the remaining duration of the current driving mission.

2. A method (10) according to claim 1 , wherein the step of determining (102) said first value of maximum allowable temperature ( TBatt_Cell_Max_Drv_Tgt) Comprises: selecting, as a function of the value of said first input parameter (DriveMod), a respective correlation map (1021 ) between the state of charge (SOC) of the traction battery and said first value of maximum allowable temperature (TBatt_ceii_Max_Drv_Tgt), wherein said first value ofmaximum allowable temperature (TBatt_ceii_Max_Drv_Tgt) increases as the state of charge (SOC) decreases; and applying said selected correlation map (1021 ) to the value of said second input parameter (SOC) to determine (102) said first value of maximum allowable temperature (TBatt_ceii_Max_Drv_Tgt).

3. A method (10) according to claim 1 or claim 2, wherein the step of determining (104) said actual value of maximum allowable temperature (TBatt_ceii_Max_Tgt) comprises: checking (S3) whether said third input parameter (TurtleModeActive) is asserted and, in the affirmative case, setting said actual value of maximum allowable temperature (TBatt_ceii_Max_Tgt) to a constant value equal to the upper critical temperature limit (TBatt_ceii_Max_Trti_Tgt) allowed for said traction battery, so as to minimize the activation of a cooling system of said traction battery, wherein said constant value is preferably equal to about 48°C.

4. A method (10) according to claim 3, wherein the step of determining (104) said actual value of maximum allowable temperature (TBatt_Cell_Max_Tgt) Comprises: in case said third input parameter (TurtleModeActive) is deasserted, checking (S2) whether said fourth input parameter (FastChrgPrecondActive) is asserted and, in the affirmative case, setting said actual value of maximum allowable temperature (TBatt_ceii_Max_Tgt) to a value equal to said fifth input parameter ( TBatt_ceii_Max_FCP_Tgt), so as to precondition said traction battery to be able to carry out a fast or ultra-fast charge.

5. A method (10) according to claim 4, wherein the step of determining (104) said actual value of maximum allowable temperature (TBatt_Cell_Max_Tgt) Comprises:- in case said fourth input parameter (FastChrgPrecondActive) is deasserted, checking (S1 ) whether said first input parameter (DriveMod) indicates that the currently selected drive mode is a performance-oriented drive mode or a range-oriented drive mode; and if the currently selected drive mode is a performance- oriented one, setting said actual value of maximum allowable temperature (TBatt_ceii_Max_Tgt) to a value equal to said first value ofmaximum allowable temperature (TBatt_ceii_Max_Drv_Tgt)', if the currently selected drive mode is a range-oriented drive one, setting said actual value of maximum allowable temperature (TBatt_ceii_Max_Tgt) to a value equal to a second value of maximum allowable temperature (TBatt_ceii_Max_Raw_Tgt) determined as a function of said sixth input parameter ( TAmb) and / or said seventh input parameter (AtEndjviission).

6. A method (10) according to claim 5, wherein said second value of maximum allowable temperature ( TBatt_ceii_Max_Raw_Tgt) is determined selecting the maximum value amongst: said first value of maximum allowable temperature ( TBatt_ceii_Max_Drv_Tgt), a third value of maximum allowable temperature ( TBatt_ceii_Max_Tamb_Tgt) associated to the ambient temperature, and a fourth value of maximum allowable temperature ( TBatt_ceii_Max_EndMis_Tgt) associated to the remaining duration of the current driving mission.

7. A method (10) according to claim 6, wherein said third value of maximum allowable temperature ( TBatt_ceii_iviax_Tamb_Tgt) is determined applying a correlation map (1041 ) between the ambient temperature and said third value of maximum allowable temperature ( TBatt eiijviax ramb rgt) to said sixth input parameter ( TAmb), wherein said third value of maximum allowable temperature (TBatt_ceii_Max_Tamb_Tgt) increases as the ambient temperature increases until reaching an upper limit value, wherein said upper limit value is preferably equal to about 43°C or 44°C.

8. A method (10) according to claim 6 or claim 7, wherein said fourth value of maximum allowable temperature ( TBatt_ceii_Max_Endiviis_Tgt) is determined by subtracting, from an upper limit value, the product of said seventh input parameter (AtEndjviission) and a time gradient of temperature increase ( Gradrempinc), wherein said upper limit value is preferably equal to about 43°C or 44°C.

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