A method for charging the battery of a vehicle having an electric traction motor and a corresponding vehicle

Abstract

A method for charging at least one battery of a vehicle having an electric traction motor, said method comprising: - determining a plurality of profiles comprising a respective state of charge (SOC) and a respective battery temperature (TBatt) as a function of a given state of charge (SOCTgt) and of a given battery temperature (TBatt_Tgt), said given state of charge (SOCTgt) and said given battery temperature (TBatt_Tgt) being the state of charge (SOC) and the battery temperature (TBatt) to be reached at the end of the charging of the at least one battery; - determining, for each profile in said plurality of profiles, a battery input current limit (IBatt_Lim_1, IBatt_Lim_2, …, IBatt_Lim_n) as a function of the respective state of charge (SOC) and of the respective battery temperature (TBatt), said battery input current limit (IBatt_Lim_1, IBatt_Lim_2, …, IBatt_Lim_n) being determined so as to generate, flowing in said at least one battery, an amount of heat less than or equal to a maximum cooling power of said battery Formula (I); - selecting, as a function of an actual state of charge of the battery, a battery input current limit (IBatt_Lim_1, IBatt_Lim_2, …, IBatt_Lim_n) out of the determined battery input current limits (IBatt_Lim_1, IBatt_Lim_2, …, IBatt_Lim_n); and - using the selected battery input current limit (IBatt_Lim_1, IBatt_Lim_2, …, IBatt_Lim_n) to limit a maximum battery acceptable current (IBatt_Acc).

Description

[0001] "A method for charging the battery of a vehicle having an electric traction motor and a corresponding vehicle"

[0002] TEXT OF THE DESCRIPTION

[0003] Field of the Invention

[0004] The embodiments of the present description refer to methods for charging batteries of vehicles having electric traction motors .

[0005] Specifically, various embodiments of the present description regard solutions for minimizing the charging and thermal pre-conditioning time of batteries of vehicles having electric traction motors .

[0006] Known Art

[0007] The charging process of the batteries of vehicles having electric traction motors is of paramount importance, since it influences the drivers ' waiting time before they can resume driving .

[0008] Said waiting time may influence the drivers ' activities and, if it is excessive, it may discourage using said vehicles having electric traction motors , especially in commercial activities wherein it is preferable to minimize the waiting times .

[0009] Moreover, said waiting times may affect the performances of a vehicle having an electric traction motor during a race or on track, when it is important to have as short a waiting time as possible, so as to increase the vehicle performances .

[0010] In this regard, the known art comprises solutions which attempt to minimize the waiting time needed for charging a battery, for example by trying to achieve, as rapidly as possible, the desired "State of Charge" (SOC) , i . e . the desired level of charge of an electric battery expressed with respect to the capacity thereof, for example as a percentage, wherein a percentage of 0% corresponds to a flat battery, while a percentage of 100% corresponds to a fully charged battery .

[0011] A problem of said known solutions consists in the fact that a driver of a given vehicle having an electric traction motor undergoing a battery charging phase cannot restart driving directly after the end of said charging phase .

[0012] Actually, even though the time needed to achieve the state of charge is minimized, the driver cannot restart the vehicle at the end of the charging phase, since the temperatures reached by the batteries of the vehicle during said charging phase may be very high, and therefore the driver will have to wait for the end of a battery conditioning phase, i . e . he / she will have to wait for the temperature of said batteries to decrease into limits which are compatible with driving, before he / she can restart the vehicle .

[0013] Therefore, the waiting time of a driver of a vehicle implementing a known solution for managing the charging phase comprises both the time needed for said charging phase and the time needed for the conditioning phase of the vehicle batteries, therefore delaying the starting of the vehicle for a non-negligible time with respect to the moment when the charging phase ends .

[0014] Solutions for favouring a reduction of said waiting time for the drivers before resuming driving would therefore be advantageous .

[0015] Object of the Invention

[0016] The invention aims at solving the technical problems outlined in the foregoing . Specifically, the invention aims at providing a method for charging one or more batteries of a vehicle having an electric traction motor while attempting to minimize the waiting time for the drivers .

[0017] Summary of the Invention

[0018] The object of the invention is achieved by means of a method having the features set forth in the claims that follow, which are an integral part of the technical teaching provided herein in relation to the invention .

[0019] One or more embodiments refer to a corresponding vehicle .

[0020] Brief Description of the Figures

[0021] The invention will now be described with reference to the annexed Figures, which are provided by means of non-limiting example only and wherein :

[0022] - Figure 1 is a graph showing a relationship between a maximum battery acceptable current as a function of a state of charge and of a temperature of said battery, according to embodiments of the present description;

[0023] - Figure 2 is a graph showing a possible evolution of temperature profiles of a battery, according to embodiments of the present description;

[0024] - Figure 3 is a graph showing a possible evolution of temperature profiles of a battery, comprising a knee profile, according to embodiments of the present description;

[0025] - Figure 4 is a graph showing a situation wherein a battery input current is higher than an input current limit defined via the knee profile, according to embodiments of the present description;

[0026] - Figure 5 is a map employed for obtaining a knee value of the battery temperature based on a maximum cooling power of the battery, and on a target battery temperature, according to embodiments of the present description;

[0027] - Figure 6 is a map employed to obtain a value of the knee state of charge based on the maximum cooling power of the battery and on the target battery temperature, according to embodiments of the present description;

[0028] - Figure 7 is a block diagram showing a method for selecting a profile of a battery input current limit according to embodiments of the present description; and

[0029] - Figure 8 is a flow chart of a control function according to embodiments of the present description .

[0030] Detailed Description

[0031] In the following description one or more specific details are given in order to provide a thorough understanding of exemplary embodiments of the present description . The embodiments may be implemented without one or more of the specific details, or with other methods, components , materials, etc . In other cases , well-known operations , materials or structures are not shown or described in detail in order not to obscure various aspects of the embodiments .

[0032] A reference to "an embodiment" or "one embodiment" within the present description indicates that a particular configuration, structure or characteristic described with reference to the embodiment is comprised in at least one embodiment . Therefore, phrases such as "in an embodiment" or "in one embodiment" and the like, which may be present in one or more points of the present description, are not necessarily all referred to one and the same embodiment .

[0033] Moreover, particular configurations , structures or characteristics may be combined in any suitable fashion in one or more embodiments .

[0034] The headings provided herein are for convenience only, and therefore they do not limit the extent of protection or the scope of the embodiments .

[0035] Throughout the Figures annexed herein and throughout the detailed description provided in the following, unless the context dictates otherwise, the similar parts or elements are denoted by similar references / numbers, and a corresponding description will be omitted for the sake of brevity . It should be noted that the solution described herein may be applied to any vehicle having an electric traction motor and comprising an electric battery configured to be charged by systems external to the vehicle .

[0036] As described in the foregoing, solutions as described in the present document aim at providing a method for charging one or more batteries of a vehicle having an electric traction motor, while trying to minimize the drivers7waiting time before they can resume driving .

[0037] In this regard, the solutions described herein aim at minimizing both the time needed for the charging phase of the batteries and the time needed for the thermal pre-conditioning phase thereof .

[0038] Therefore, solutions as described herein take into account :

[0039] - both a target state of charge SOChgt, i . e . a battery state of charge which is desired to be reached at the end of the charging phase;

[0040] - and a target battery temperature TBatt_Tgt< i . e . a battery temperature which is desired to be reached at the end of the charging phase, e . g . a temperature which is already comprised within the admissible limits for driving, so as to avoid executing the pre-conditioning phase .

[0041] Therefore, said operation of minimizing the waiting time corresponds to an operation of minimizing the time employed to reach both the target state of charge SOChgt and the target battery temperature TBatt_Tgt .

[0042] In this fashion, advantageously, the driver must wait for a minimum time before resuming driving . It will be noted that such an advantage is particularly useful, for example, in a race or on track, in order to maximize the vehicle performances . For example, in order to obtain better performances on track, a vehicle having an electric traction motor may be configured to have :

[0043] - a battery temperature before starting equal to the target battery temperature TBatt_Tgt, wherein said target battery temperature TBatt_Tgt is comprised in the admissible limits for driving and is calculated, for example, as a function of the kilometres of the race, and

[0044] - a state of charge before starting equal to the target state of charge SOCTgt, wherein said target state of charge SOCTgt may be for example the highest state of charge, i . e . corresponding to a full charge of the battery, in such a way as to increase a maximum discharge power .

[0045] For this reason, e . g . before a race, the one or more batteries of a corresponding vehicle having an electric traction motor are charged in a respective charging phase and are thermally conditioned .

[0046] During the charging phase of said one or more batteries, a great amount of heat is generated in response to the flow of a charging current within said batteries (Joule effect ) , and therefore the temperature of said batteries increases up to (very) high temperatures .

[0047] Solutions as described herein provide a control function adapted to manage one or more profiles of battery input current limits , in such a way as to limit the maximum battery acceptable current or the maximum current deliverable by the charging system, as a function of an actual state of charge and of an actual temperature value of the batteries .

[0048] Therefore, limiting, based on the selected profile of input current limit , a maximum battery acceptable current lBatt_ cc, i . e . the maximum current acceptable by the battery or the maximum current deliverable by the charging system, to a corresponding battery input current limit IBatt_Lim, wherein said given battery input current limit has a value less than or equal to said maximum battery acceptable current IBatt_Acc .

[0049] Thus , said control function may minimize the total waiting time, i . e . the total time employed to reach the target temperature TBatt_Tgt and the target state of charge SOCTgt .

[0050] For example, said control function may be configured to enable reaching said target battery temperature TBatt_Tgt and said target state of charge SOCTgt at the end of the charging phase, thereby avoiding a conditioning phase of the battery subsequent to the charging phase thereof .

[0051] It should be noted that the amount of heat , specifically a heat flow, generated by the Joule effect HRBatt is proportional to the square of the battery input current IBatt, according to the equation : wherein RBatt is the average electrical resistance of the battery .

[0052] It should be noted that the dynamic variation of the battery temperature TBatt over time t may be obtained via the following equation : wherein QcigBatt is the battery cooling power and CThrm Battis the battery thermal capacity, i . e . a characteristic value of the battery which remains constant .

[0053] It should be noted that the dynamic variation of the battery state of charge SOC over time t may be obtained via the following equation : wherein CElect Battis the electrical capacity of the battery .

[0054] Figure 1 is a qualitative graph 10 showing a relationship between the maximum battery acceptable current, i . e . the maximum current which may flow in the battery IBatt_Acc, as a function of a state of charge SOC of said battery and of a temperature TBatt of said battery according to embodiments of the present description .

[0055] It should be noted that, as shown in Figure 1 , the maximum battery acceptable current IBatt_Acc depends both on the battery state of charge SOC and on the battery temperature TBatt •

[0056] Said maximum battery acceptable current IBatt_Acc increases in response to the increase of the battery temperature TBatt, for example, it is noted that in Figure 1 TBatt4 , TBatt3, TBatt2, and TBattl assume increasing temperature values , with TBatt4 assuming a lower temperature value and TBattl assuming a higher temperature value, and it decreases as the state of charge SOC increases .

[0057] During the charging phase of a vehicle having an electric traction motor, the amount of heat - specifically, the heat flow - generated by the Joule effect HRBatt in response to the flow of a charging current in the battery IBatt may be higher than the battery cooling power QcigBatt •

[0058] Therefore, said control function may be configured to manage said one or more profiles of the battery input current limits, so as to prevent the heat flow generated by the Joule effect HRBatt from exceeding the battery cooling power QcigBatt -

[0059] In this way, at the end of the charging phase, the target battery temperature TBatt_Tgt may already have been reached, and therefore the battery conditioning phase may be omitted .

[0060] In fact , by managing the profiles of the battery input current limits in such a way as to limit the maximum battery acceptable current IBatt_Acc to a lower value, corresponding to said battery input current limit lBatt_Lim, it is possible to correspondingly limit the amount of heat - specifically the heat flow - generated by the Joule effect HRBatt and, consequently, the battery temperature .

[0061] Said control function may comprise the following steps :

[0062] - determining one or more profiles of the battery temperature TBatt as a function of the respective states of charge SOC;

[0063] - calculating a battery input current limit IBatt_Lim, i . e . a respective profile of battery input current limit, for each of the temperature profiles defined as a function of the profile of the considered battery temperature profile TBatt and of the respective state of charge SOC, said battery input current limit IBatt_Lim being calculated in such a way as to prevent the amount of heat - specifically the heat flow - generated by the Joule effect HRBatt from exceeding the battery cooling power QcigBattand in such a way as to minimize the total waiting time;

[0064] - selecting one of the determined battery input current limits IBatt_Lim as a function of the value of an actual state of charge SOCAct of the battery, i . e . of a value of a present state of charge; and

[0065] - employing the selected battery input current limit IBatt_Lim, i . e . the respective profile of battery input current limit, for limiting the maximum battery acceptable current Isatt_Acc for a given time interval, e . g . until the battery actual state of charge SOCAct increases so much as to enable the selection of a different battery input current limit IBatt_Lim .

[0066] It should be noted that , in order to perform said calculation step of the battery input current limit lBatt_Lim, it is possible to consider that the best solution for minimizing the total waiting time is the one which enables to simultaneously reach, at the end of the charging phase, both the target state of charge SOChgt and the target battery temperature TBatt_Tgt .

[0067] Figure 2 is a qualitative graph 20 showing a possible evolution of temperature profiles of a battery TBatt according to embodiments of the present description .

[0068] Such battery temperature profiles TBatt, which are represented by a plurality of points TP, lBatt_Lim_i , lBatt_Lim_2 , ... , lBatt_Lim_n, comprise a respective state of charge SOC and a respective battery temperature TBatt •

[0069] Said battery temperature profiles TBatt may be considered in an ordered fashion, for example starting from a first temperature profile, represented by a starting point TP, up to a last temperature profile represented by an n-th point lBatt_Lim_n .

[0070] It should be noted that the battery temperature TBatt comprised in a given temperature profile is obtained as a function of the state of charge SOC comprised in the same given temperature profile, for example according to the formula described in the following .

[0071] Therefore, said ordered battery temperature profiles TBatt may be determined :

[0072] - by identifying a first temperature profile, represented by a starting point TP , having as coordinate values the target state of charge SOCTgt and the target battery temperature TBatt_Tgt that must be reached at the end of the charging phase; and

[0073] - by executing the following operations for each further temperature profile to be determined, for example a second temperature profile represented by a first point lBatt_Lim_i, a third temperature profile represented by a second point IBatt_Lim_2, ..., and the last temperature profile represented by an n-th point lBatt_Lim_n I determining a respective state of charge SOC by subtracting a given amount of state of charge dSOC from a state of charge comprised in a profile that precedes , in the order of the temperature profiles, the further profile to be determined, moving towards lower values of state of charge SOC; and determining, as a function of the respective determined state of charge SOC, a respective battery temperature TBatt, said respective battery temperature TBatt being higher than the battery temperature comprised in the profile that precedes , in the order of the temperature profiles , the further profile to be determined, resulting therefore in a temperature increase of a respective value dTBatt ( see Figure 2 : dTBatt_l , dTBatt_2 , ••• , dTBatt_n ) •

[0074] The given amount of state of charge dSOC considered for a given time period dt may be considered as a battery discharge which takes place during said time period dt, considering both the state of charge SOC and the time period dt backwards, i . e . considering an order moving from higher values towards lower values .

[0075] Said given amount of the state of charge dSOC and said time period dt may be put into mutual relationship via the following equation :

[0076] The temperature increase of a respective value dTBatt ( dTBatt_i , dTBatt_2 , ... , dTBatt_n ) may be obtained as a function of :

[0077] - said given amount of the state of charge dSOC,

[0078] - said battery input current limit IBatt_Lim (based on the state of charge SOC and on the battery temperature

[0079] TBatt) , and a maximum cooling power available to the battery QcigBattMax , for example, via the following equation :

[0080] It should be noted that a temperature profile is characterized by a value of the battery TBatt which is higher with respect to a profile which precedes it , since the following inequality holds :

[0081] It should be noted that each of the battery temperature profiles TBatt may be associated with a respective battery input current limit IBatt_Lim, i . e . with a respective profile of battery input current limit, corresponding to the maximum input current which can be accepted by the battery when said temperature profile (i . e . , said respective profile of battery input current limit ) is selected by the control function .

[0082] Therefore, each of said battery temperature profiles TBatt corresponds to an input current limit profile, and the selection of one of said battery temperature profiles TBatt corresponds to the selection of the corresponding input current limit profile .

[0083] For example, in Figure 2 said maximum battery input currents IBatt_Lim are represented by the first point lBatt_Lim_i , the second point IBatt_Lim_2 , ... , and the n-th point IBatt_Lim_n .

[0084] Normally, for high values of the state of charge SOC, the amount of heat - specifically the heat flow - generated by the Joule effect HRBatt in response to the flow of the maximum battery acceptable current IBatt_Acc in the battery is smaller than the maximum cooling power available to the battery QcigBattMax > since, according to what has been described with reference to Figure 1 , said maximum battery acceptable current IBatt_Acc has a low value . Therefore, for high values of the state of charge SOC, the battery input current limit lBatt_L±m associated with a respective battery temperature profile TBatt may coincide with the maximum battery acceptable current lBatt_Acc, for example, if the method makes use of the maximum conditioning of the battery thermal power, i . e . the maximum cooling power available to the battery QcigBattMax •

[0085] In this way, it is possible to minimize the charging time of the battery, since the target state of charge SOChgt and the target battery temperature TBatt_Tgt will be reached simultaneously at the end of the charging phase .

[0086] Indeed, the control function may be configured to activate the battery temperature profiles TBatt according to an order reversed with respect to the previously defined order (i . e . , in an order reversed with respect to the order used for defining said temperature profiles ) , e . g . :

[0087] - by activating first the last (n-th) temperature profile, by charging the battery through a current having a value equal to the battery input current limit lBatt_Lim_n r

[0088] - by activating, when the actual state of charge SOC increases up to the value of the state of charge SOC of the following profile, i . e . of an n-l-th temperature profile, said n-l-th temperature profile, by charging the battery through a current having a value equal to the battery input current limit lBatt_Lim_n-i ;

[0089] - by iterating said step of activating the following profile ( in the order IBatt_Lim_n-2 , ... , lBatt_Lim_2 , and lBatt_Lim_i ) when the value of the state of charge SOC of said following profile is reached, by charging the battery through a current having a value equal to the battery input current limit (respectively IBatt_Lim_n-2 , ... , lBatt_Lim_2 , and IBatt_Lim_i ) relating to said following profile; and

[0090] - by reaching, when the second temperature profile is activated and the battery is being charged through a current having a value equal to the battery input current limit IBatt_Lim_1 related to said second temperature profile lBatt_Lim_i, the first temperature profile, i . e . the starting point TP, having the target state of charge SOChgt and the target battery temperature Tsatt_Tgt , thereby ending the charging phase .

[0091] While moving towards lower and lower values of the state of charge SOC, the battery temperature TBatt gradually increases . Therefore, according to what has been described with reference to Figure 1 , the value of the maximum battery acceptable current Isatt_Acc increases accordingly .

[0092] In response to the increase of the maximum battery acceptable current lBatt_Acc, an increase of the amount of heat takes place - specifically the heat flow - generated by the Joule effect HRaatt in response to the flow of said maximum battery acceptable current lBatt_Acc in the battery .

[0093] Therefore, it is possible to define a profile of the battery temperature TBatt wherein the amount of heat - specifically the heat flow - generated by the Joule effect HRsatt equals the maximum cooling power available to the battery QcigBattMax - Said temperature profile takes the name of a "knee" profile, and it is represented by a so-called "knee point" KP , which for example coincides with the last temperature profile lBatt_Lim_n .

[0094] Figure 3 is a qualitative graph 30 showing a possible evolution of temperature profiles TBatt of a battery comprising a knee profile KP, lB tt_Lim_n according to embodiments of the present description .

[0095] Said knee profile KP is characterized by a state of charge SOC which is named knee state of charge SOCKnee, and by a battery temperature TBatt which is named knee battery temperature TBatt_ _Knee •

[0096] Said knee state of charge SOCKnee and said knee battery temperature TBatt_Knee are the values of the state of charge SOC and of the battery temperature TBatt which may enable obtaining a battery input current limit IBatt_Lim_Knee having a value equal to the maximum battery acceptable current IBatt_Acc that enables to obtain, by flowing within the battery, an amount of heat generated by the Joule effect HRBatt which equals the maximum cooling power available to the battery QcigBattMax -

[0097] Said battery input current limit IBatt_Lim_Knee may be obtained via the equation :

[0098] Said knee state of charge SOCKnee may be considered as a separation point , in fact , the battery temperature profiles TBatt characterized by a value of the state of charge SOC higher than said knee state of charge SOCKnee are managed (activated) by the control function, as stated in the foregoing .

[0099] Moreover, for such profiles of the battery temperature TBatt characterized by a value of the state of charge SOC higher than said knee state of charge SOCKnee / the corresponding battery input current limit lBatt_Lim is equal to the maximum battery acceptable current lBatt_Acc in the conditions of the state of charge SOC and of the battery temperature TBatt of the corresponding temperature profile .

[0100] If the actual state of charge SOC of the battery has a value lower than the knee state of charge SOCKnee , the control function is configured to activate the knee profile KP, thus limiting the maximum battery acceptable current lBatt_Acc to the value of the battery input current limit lBatt_Lim_Knee related to the knee profile KP . In this way, the waiting time is minimized, since the battery input current IBatt is limited in such a way as to balance the amount of heat - specifically the heat flow - generated by the Joule effect HRBatt with the maximum cooling power available to the battery QcigBattMax r thereby simultaneously reaching, at the end of the charging phase, both the target state of charge SOChgt and the target battery temperature TBatt_Tgt, and therefore avoiding a subsequent pre-conditioning phase .

[0101] To sum up, embodiments of solutions as described herein enable obtaining a method for charging at least one battery of a vehicle having an electric traction motor, said method comprising :

[0102] - determining a plurality of temperature profiles comprising a respective state of charge SOC and a respective battery temperature TBatt as a function of a given state of charge, i . e . the target state of charge SOCTgt , and of a given battery temperature, i . e . the target battery temperature TBatt_Tgt, the given state of charge SOCTgt and the given battery temperature TBatt_Tgt being the state of charge SOC and the battery temperature TBatt to be reached at the end of the charging of the at least one battery, i . e . at the end of the charging phase, preferably simultaneously;

[0103] - determining, for each temperature profile in the plurality of temperature profiles , a battery input current limit lBatt_Lim as a function of the respective state of charge SOC and of the respective battery temperature TBatt , the battery input current limit IBatt_Lim being determined so as to generate, while flowing in the at least one battery, an amount of heat HRBatt smaller than or equal to a maximum cooling power of the battery QcigBattMax r

[0104] - selecting, as a function of the actual state of charge SOC ct of the battery, a battery input current limit lBatt_Lim out of the determined battery input current limits and

[0105] - using the selected battery input current limit lBatt_Lim to limit a maximum battery acceptable current Isatt_Acc •

[0106] It is possible to demonstrate that, for values of the state of charge SOC lower than the value of the knee state of charge SOCKnee, it is not convenient, as regards the waiting times, to have a battery input current iBatt higher than the battery input current limit lBatt_Lim_Knee defined for the knee profile KP .

[0107] In fact, the time increase resulting from the execution of a battery pre-conditioning phase at the end of the battery charging phase Atimecig ( such preconditioning phase being required since, by using an input current higher than the battery input current limit lBatt_Lim_Knee defined for the knee profile KP , the battery temperature TBatt exceeds the value of the knee battery temperature TBatt_Knee) is higher than the time reduction resulting from a faster charging phase Atimechrg .

[0108] Figure 4 is a qualitative graph 40 showing a situation wherein the battery input current Isatt is higher than the input current limit lBatt_Lim_Knee defined in the knee profile KP according to embodiments of the present description .

[0109] For example, it is assumed to increase the value of the battery input current limit lB tt_Lim_Knee defined for the knee profile KP by an amount equal to x ( shown in Figure 4 ) , and ASOCxnee is assumed to indicate the difference between the value of the knee state of charge SOCKnee and the value of the state of charge SOC± existing at the beginning of the charging phase, i . e . the starting value of the state of charge SOCi .

[0110] The value of the reduction of the time needed for the charging phase Atimechrg deriving from the use of an input current value amounting to IBatt_Lim_Knee+x, instead of a current value equal to the battery input current limit IBatt_Lim_Knee defined for the knee profile KP, in order to obtain a variation of the state of charge SOC amounting to ASOCKnee, may be expressed as :

[0111] Such equation may be simplified as follows :

[0112] By using an input current value amounting to lBatt_Lim_Knee+x , instead of an input current value equal to the battery input current limit IBatt_Lim_Knee for a variation of the state of charge SOC amounting to ASOCKnee , it is possible to observe an increase of the variation of the battery thermal energy ECigBatt which must be dissipated .

[0113] Such battery thermal energy EclgBattmay be expressed as :

[0114] Such equation may be simplified as follows :

[0115] Therefore, the increase of time Atimecig resulting from the execution of a battery pre-conditioning phase at the end of the battery charging phase in order to dissipate the battery thermal energy EclgBattby means of the maximum cooling power available to the battery QcigBattMax , may be expressed via the following equations :

[0116] Such equation may be simplified as follows :

[0117] Therefore, it is possible to demonstrate that said increase of time resulting from the further preconditioning phase Atimeclg is greater than said decrease of time relating to the charging phase Atimechrg, i . e . :

[0118] Said inequality may be simplified as follows :

[0119] Said inequality is always verified for any value of x > 0,i . e . for any increase of the battery input current

[0120] Isatt with respect to the input current limit Isatt. _Lim_Knee defined in the knee profile KP .

[0121] Therefore, it is not convenient to increase the battery input current Isatt with respect to the input current limit lB tt_Lim_Knee defined in the knee profile KP for temperatures higher than the knee battery temperature TBtt_Knee, since the total waiting time of a driver before resuming driving would be longer .

[0122] Thus , the evolution of the battery temperature TBatt during the charging phase is characterized by a flat area, wherein the battery temperature TBatt assumes a value equal to the knee battery temperature TBatt_Knee defined in the knee profile KP .

[0123] Said flat area is maintained until the value of the state of charge SOC of the battery reaches the value of the knee state of charge SOCKnee defined in the knee profile KP, and therefore said battery temperature TBatt starts decreasing .

[0124] Said reduction is due to the fact that, when the state of charge SOC of the battery is higher than the knee state of charge SOCKnee, the maximum cooling power available to the battery QctgBattMax is higher than the amount of heat - specifically the heat flow - generated by the Joule effect HRBatt due to the flow of the maximum battery acceptable current IBatt_Acc in the battery .

[0125] In embodiments of the present solution, the battery temperature profiles TBatt may be calculated, e . g . , offline, i . e . , by means of a method which has at its disposal the input signals required to calculate the respective output signals already in a moment preceding the calculation of said output signals, as a function of the maximum cooling power available to the battery QcigBattMax r of the target battery temperature TBatt_Tgt, and of the target state of charge SOCTgt .

[0126] For example, in various embodiments, a driver may choose among a plurality of values of the target state of charge SOCTgt, for example between two values amounting to 80% and 100% . It should be noted that both the value and the number of the target states of charge SOCTgt which may be chosen are provided by way of example only, and they do not limit the extent of protection of the present application .

[0127] In various embodiments, said target battery temperature Tsatt_Tg may be determined by the control function based e . g . on the length of a race or of a route .

[0128] The values of the knee battery temperature TBatt_Knee and of the knee state of charge SOCKnee may be derived from maps based on the maximum cooling power available to the battery QcigBattMax and on the target battery temperature TBatt_Tgt .

[0129] Figure 5 and Figure 6 show examples 50 and 60 of such maps .

[0130] Figure 5 shows a map 50 used for obtaining the value of the knee battery temperature TBatt_Knee based on the maximum cooling power available to the battery QcigBattMax and on the target battery temperature Tsatt_Tgt .

[0131] Figure 6 shows a map 60 used for obtaining the value of the knee state of charge SOCKnee based on the maximum cooling power available to the battery QcigBattMaxand onthe target battery temperature TBatt_Tgt .

[0132] Said values of the knee battery temperature TBatt_Knee and of the knee state of charge SOCKnee may be respectively derived from the map of Figure 5 and from the map of Figure 6, for example, via a linear extrapolation .

[0133] It should be noted that the evolution of the temperatures TBatt_profiie determined for the profiles of the battery temperature TBatt may exhibit ( for example, see Figure 3 ) :

[0134] - a first flat area, which extends for values of the actual state of charge SOCAct lower than the knee state of charge SOCKnee, wherein the battery temperature TBatt assumes a value equal to the knee battery temperature TBatt_Knee defined in the knee profile KP ; and

[0135] - a second linear area, which extends for values of the actual state of charge SOCAct higher than or equal to the knee state of charge SOCKnee, wherein the battery temperature TBatt decreases linearly starting from the knee battery temperature TBatt_Knee down to the target battery temperature TBatt_Tgt .

[0136] Therefore, the evolution of the temperatures

[0137] TBatt_Profiie determined for the battery temperature profiles TBatt may be determined via the following system of equations :

[0138] Figure 7 is a block diagram 70 showing a method for selecting one of the profiles of the battery input current limits IBatt_ _Lim_Profile •

[0139] A battery input current limit block IBatt_Lim_in may be configured to determine the maximum battery acceptable current IBatt_Acc as a function of the current battery temperature TBatt and of the present state of charge SOC, for example based on the graph and on the considerations provided with reference to Figure 1 .

[0140] Said battery input current limit block lBatt_Lim_m may be further configured to provide, to a minimization block M, the determined maximum battery acceptable current lBatt_Acc •

[0141] An open loop block OL may be configured to determine the value of the battery input current limit lBatt_Lim_Knee relating to the knee profile KP, for example via the formula described in the foregoing with reference to Figure 3 .

[0142] Alternatively, said open loop block OL may be configured to store in a memory said previously calculated value of the battery input current limit lBatt_Lim_Knee •

[0143] Said open loop block OL may be further configured to provide, to a summing block Si, said battery input current limit lBatt_Lim_Knee related to the knee profile KP, said battery input current limit IBatt_ _Lim_Knee being the current which enables balancing the maximum cooling power available to the battery QcigBattMax with the amount of heat - specifically, the heat flow - generated by the Joule effect HRBatt .

[0144] A closed loop block CL is configured to implement a proportional control function, so as to :

[0145] - reduce the battery input current limit lBatt_Lim when the present battery temperature TBatt (i . e . , an actual battery temperature TBatt_Act) is higher than an expected temperature according to the temperature evolution TBatt j>rof tie, said expected temperature being obtained as a function of the present state of charge SOC via the formula of the temperature evolution TBatt_Profiie described in the foregoing; and

[0146] - increase the battery input current limit IBatt_Lim when the current battery temperature TBatt is lower than an expected temperature according to the temperature evolution TBatt_profile, said expected temperature being obtained as a function of the present state of charge SOC via the formula of temperature evolution TBatt_profile described in the foregoing .

[0147] Therefore, said closed loop block CL may be configured to subtract, for example in a subtractor block S2, from the value of the battery temperature TBatt the temperature expected according to the temperature evolution TBatt_profiie, thereby obtaining a temperature difference ATBatt, and to determine, as a function of the temperature difference ATBatt, a corresponding current difference relating to the battery input current limit ΔIBatt_Lim which is provided to the summing block Si .

[0148] The summing block Si may be configured to sum the current received from the open loop block OL, i . e . the battery input current limit lBatt_Lim_Knee related to the knee profile KP, with the current received from the closed loop block CL, i . e . the current difference relating to the battery input current limit AIBatt_Lim, in order to obtain the battery input current limit lBatt_Lim .

[0149] Said summing block Si may be further configured to provide to the minimization block M said battery input current limit IBatt_ _Lim •

[0150] The minimization block M may be configured to determine the minimum current between the current received by the battery input current limit block lBatt_Lim_in, i . e . the maximum battery acceptable current lBatt_ cc, and the current received by the summing block Si, i . e . the battery input current limit IBatt_Lim, and to provide said minimum current as output .

[0151] It should be noted that said minimum current corresponds to the current selected by the control function, i . e . to a profile IBatt_ _Lim_Prof ile selected out of the profiles of the battery input current limits .

[0152] Figure 8 is a flow chart 80 of a control function according to embodiments of the present description .

[0153] Said control function may be configured to :

[0154] - determine, in a first step 802 , whether the actual state of charge SOCAct is smaller than the knee state of charge SOCKnee, and, in this case, define a present temperature value TBatt_Profileequal to the knee battery temperature TBatt_Kneedefined in the knee profile KP ;

[0155] - determine, in said first step 802 , whether the actual state of charge SOCAct is higher than or equal to the knee state of charge SOCKnee, and, in this case, define the present temperature value TBatt_Profileas a function of a linear relationship between the knee battery temperature TBatt_Kneeand the target battery temperature TBatt_Tgt; and

[0156] - select, as a function of the present temperature value TBatt_Profile, a profile of battery input current limit out of one or more profiles of the battery input current limits, thus determining a limit current IBatt_Lim_Profilewhich may be accepted by the battery when said selected profile is being used .

[0157] Said operation of selecting a profile of battery input current limit may comprise the following operations :

[0158] - determining a maximum battery acceptable current IBatt_Accbased on the present battery temperature TBattand on the present state of charge SOC;

[0159] - determining a battery input current limit lBatt_Limby summing the battery input current limit IBatt_ _Lim_Kneerelating to the knee profile KP and a proportional term P (TBatt_Profiie ~TBatt_Act ') r wherein TBatt Actindicates an actual battery temperature TBatt, related to the current difference described in the foregoing; and

[0160] - determining as the profile of battery input current limit to be activated the profile characterized by a limit current lBatt_Lim_profiie equal to the lower value between the maximum battery acceptable current lBatt_Acc and the battery input current limit lBatt_Lim .

[0161] Therefore, the solution described in detail in the present document enables obtaining a method for charging one or more batteries of a vehicle having an electric traction motor in such a way as to reach both a desired state of charge and a desired battery temperature at the end of the charging phase .

[0162] Thus , it may be easily understood that the solution described in the present detailed description may enable minimizing the drivers7waiting time before they can resume driving after a charging phase of the vehicle, in fact, embodiments of the present solution enable avoiding a battery pre-conditioning phase after the charging phase of the vehicle .

[0163] Without pre judice to the basic principles , the details and the embodiments may vary, even appreciably, with respect to what has been described, by way of example only, without departing from the extent of protection .

[0164] The extent of protection is defined by the annexed claims .

Claims

CLAIMS1 . Method for charging at least one battery of a vehicle having an electric traction motor, said method comprising :- determining a plurality of profiles comprising a respective state of charge ( SOC) and a respective battery temperature (TBatt) as a function of a given state of charge (SOCTgt ) and of a given battery temperature ( TBatt_Tgt )tsaid given state of charge (SOCTgt) and said given battery temperature (TBatt_Tgt) being the state of charge (SOC) and the battery temperature (TBatt) to be reached at the end of the charging of the at least one battery;- determining, for each profile in said plurality of profiles, a battery input current limit ( lBatt_Lim) as a function of the respective state of charge (SOC) and the respective battery temperature (TBatt) , said battery input current limit ( IBatt_Lim) being determined so as to generate an amount of heat (HRBatt) in said battery less than or equal to a maximum cooling power of said battery ( QcigBattMax ) ;- selecting, as a function of an actual state of charge (SOCAct) of the battery, a battery input current limit ( IBatt_ im) out of the determined battery input current limits ( IBatt_Lim) ; and- using the selected battery input current limit ( lBatt_Lim) to limit a maximum battery acceptable current ( lBatt_Acc ) •2 . Method according to claim 1 , wherein said operations of selecting and using are iteratively repeated following changes in said actual state of charge ( SOCAct ) of the battery until :- said actual state of charge (SOCAct) of the battery is equal to said given state of charge ( SOCTgt ) ; and- an actual battery temperature (TBatt_Act) is equal to said given battery temperature ( TBatt_Tgt ) ; preferably, wherein said given state of charge ( SOChgt ) and said given battery temperature ( TBatt_Tgt ) are reached simultaneously .

3. Method according to claim 1 or claim 2 , wherein said plurality of profiles is ordered and is determined :- identifying a first profile (TP ) comprising said given state of charge (SOChgt) and said given battery temperature ( TBatt_Tgt ) ; and- performing the following operations for each further profile ( IBatt_Lim_l , lBatt_Lim_2 ,determining a respective state of charge ( SOC) by subtracting a given amount of state of charge (dSOC) from a state of charge (SOC) comprised in a profile that precedes, in the ordered plurality of profiles, said further profile; and determining, as a function of said respective state of charge (SOC) , a respective battery temperature ( TBatt ) , said respective battery temperature (TBatt) being higher ( dTsatt ) than the battery temperature ( TBatt ) comprised in the profile that precedes , in the ordered plurality of profiles, said further profile .

4. Method according to claim 3, wherein the difference between the battery temperature ( TBatt ) comprised in the profile that precedes said further profile and the respective battery temperature ( TBatt ) comprised in said further profile is determined as a function of :- said respective state of charge (SOC) ;- said selected battery input current limit ( lBatt_Lim) r and- said maximum cooling power of said battery QcigBattMax •5. Method according to any of the previous claims ,wherein said plurality of profiles is determined offline .

6. Method according to any of the previous claims , wherein said plurality of profiles comprises a knee profile (KP ) comprising a knee state of charge (SOCKnee) and a knee battery temperature ( TBatt_Knee ) , and the battery input current limit ( lBatt_Lim_Knee ) corresponding to said knee profile (KP ) is determined as a function of said knee state of charge (SOCKnee) and said knee battery temperature (TBatt_Knee) and generates , flowing in said at least one battery, an amount of heat (HRBatt ) equal to the maximum cooling power of said battery (QcigBattMax) •7. Method according to claim 6, wherein said operation of selecting, as a function of the actual state of charge (SOCAct) of the battery, a battery input current limit (lBatt_Lim) out of the battery input current limits ( lBatt_Lim) determined for each profile in the plurality of profiles, comprises :- selecting, if said actual state of charge ( SOCAct ) is higher than said knee state of charge ( SOCKnee ) , a battery input current limit ( lBatt_Lim) corresponding to a profile : comprising a respective state of charge ( SOC) smaller than or equal to said actual state of charge (SOCAct) , and preceded by, in the ordered plurality of profiles , a profile comprising a state of charge (SOC) higher than said actual state of charge (SOCAct) ; and- selecting, if said actual state of charge ( SOCAct ) is smaller than or equal to said knee state of charge (SOCKnee) , the battery input current limit ( lBatt_Lim_Knee ) corresponding to said knee profile (KP ) .

8. Method according to claim 6 or claim 7 , whereinsaid operation of determining, for each profile in said plurality of profiles , the battery input current limit ( lBatt_Lim) comprises :- selecting (OL) the battery input current limit ( lBatt_Lim_Knee ) corresponding to said knee profile (KP ) as battery input current limit (IBatt_Lim) corresponding to a given profile;- reducing (CL) , if an actual battery temperature (TBatt_Act) is higher than the respective battery temperature (TBatt) comprised in said given profile, said battery input current limit ( IBatt_Lim) corresponding to said given profile; and- increasing (CL) , if the actual battery temperature (TBatt_Act) is smaller than the respective battery temperature (TBatt) comprised in said given profile, said battery input current limit ( IBatt_Lim) corresponding to said given profile .

9. Method according to claim 8 , wherein said operation of reducing (CL) and said operation of increasing (CL) are performed in a summing block ( Si) configured to :- receive, via a first input terminal, the battery input current limit ( IBatt_Lim_Knee) corresponding to said knee profile (KP ) ;- receive, via a second input terminal, a difference of battery input current limit (AIBatt_Lim) obtained as a function of a difference (S2) between said actual battery temperature (TBatt_Act) and said respective battery temperature (TBatt) comprised in said given profile; and- summing said battery input current limit ( IBatt_Lim_Knee ) corresponding to said knee profile (KP ) to said difference of battery input current limit (Al Batt_ im) r obtaining the battery input current limit ( lBatt_Lim) corresponding to said given profile .

10. Method according to claim 8 or claim 9, wherein said operation of determining, for each profile in said plurality of profiles , the battery input current limit ( lBatt_Lim) further comprises a minimization operation (M) configured to determine said battery input current limit ( lBatt_Lim) as the minimum between :- the battery input current limit ( lBatt_Lim) corresponding to said given profile; and- the maximum battery acceptable current ( lBatt_Acc ) ■11. Method according to any of the previous claims , wherein said maximum battery acceptable current (Isatt_Acc) is determined as a function of an actual battery temperature (TBatt_Act) and of said actual state of charge ( SOC ct ) of the battery .

12. Vehicle having an electric traction motor and comprising at least one battery and at least one electronic control unit, wherein :- said at least one electronic control unit is configured to perform the steps of the method according to any of the previous claims and to send a battery input current limit (iBattj m) to the at least one battery; and- said at least one battery is configured to vary a maximum battery acceptable current ( lBatt_Acc) based on said battery input current limit ( lBatt_Lim) .

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