A method for charging a low-voltage battery in a vehicle having an electric traction motor and corresponding vehicle

Abstract

A method for charging a first battery comprised in a vehicle having an electric traction motor, said vehicle comprising a second battery and an electronic control unit configured to enable a charge transfer (ChrgSil) from the second battery to the first battery; said method comprising : determining a state of charge ( SOC) of the first battery during a shutdown of said vehicle ( T1); determining, as a function of said determined state of charge ( SOC) of the first battery, a time interval ( T1-T2 ) wherein said electronic control unit is disabled ( ECUSM); and enabling, at the end ( T2 ) of said time interval ( T1- T2 ) via said electronic control unit (ECUaWU), said charge transfer (ChrgSi l) from said second battery to said first battery, until the state of charge of the first battery reaches ( T3) a given state of charge ( THH ).

Description

[0001] "A method for charging a low-voltage battery in a vehicle having an electric traction motor and corresponding vehicle"

[0002] ★★★★

[0003] TEXT OF THE DESCRIPTION

[0004] Field of the Invention

[0005] The embodiments of the present description refer to methods for charging one or more low-voltage batteries in vehicles having electric traction motors.

[0006] Specifically, various embodiments of the present description regard solutions for charging the low- voltage batteries of vehicles having electric traction motors during periods wherein such vehicles are shut down.

[0007] Known Art

[0008] The vehicles having electric traction motors are provided with electric systems comprising a low-voltage electric system, powered by a low-voltage battery, and a high-voltage electric system, powered by a high- voltage battery, which are different as regards the uses and the different voltage levels thereof.

[0009] Such vehicles having electric traction motors usually comprise DC-DC ("Direct Current - Direct Current") converters for transferring energy from the high-voltage battery, which is typically used to power the propulsion of such vehicles, to the low-voltage battery, which is used to power auxiliary electric systems such as lamps, windscreen wipers, infotainment systems and so on.

[0010] Said low-voltage battery is also normally used to power vehicle control systems and control circuits and auxiliary components of the high-voltage electrical equipment, for example a control unit of the contactors configured to close the contactors of the high-voltage battery.

[0011] Said contactors allow the low voltages of the low- voltage electric system to enable, disable, switch off and / or switch on a circuit at an (even much) higher voltage, for example, by coupling the high-voltage battery to the electric traction motor at the moment of turning on the vehicle.

[0012] A problem with the known solutions consists in the fact that, during long periods of shutdown of the vehicle, said low-voltage battery may discharge completely due to current leakages and, as a consequence, preventing the turning on of the vehicle, for example, since the control unit of the contactors, configured to close the contactors of the high-voltage battery, cannot be switched on.

[0013] Moreover, since it is not possible to switch on said control unit of the contactors, it is not possible to use the DC-DC converter for transferring energy from the high-voltage battery to the low-voltage battery, that is, for powering the low-voltage electric system.

[0014] Therefore, it would be advantageous to provide solutions for favouring the turning on of the vehicle even after long periods of shutdown.

[0015] Object of the Invention

[0016] The invention aims at solving the technical problems mentioned in the foregoing. Specifically, the invention aims at providing a method for charging one or more low-voltage batteries in a vehicle having an electric traction motor, by attempting to favour the turning on of the vehicle after long periods of shutdown, for example, by limiting the reduction of a state of charge of said one or more low-voltage batteries, while advantageously also reducing an early aging thereof.

[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] One or more embodiments will now be described, by way of example only, with reference to the annexed Figures, wherein:

[0022] Figure 1 illustrates an exemplary evolution of the state of charge of the low-voltage battery as a function of time, according to embodiments of the present disclosure; and

[0023] Figure 2 illustrates an exemplary block configured to determine the duration of a sleep mode as a function of a present state of charge of the low- voltage battery, according to embodiments of the present disclosure.

[0024] Detailed Description

[0025] In the description set forth in the following, 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 instances, well-known operations, materials or structures are not shown or described in detail in order not to obscure some aspects of the embodiments.

[0026] A reference to "an embodiment" or "one embodiment" in 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", "in one embodiment" or the like, which may be present in one or more parts of the present description, do not necessarily refer to one and the same embodiment.

[0027] Moreover, particular configurations, structures or characteristics may be combined in any suitable fashion in one or more embodiments.

[0028] The headings used herein are provided for convenience only, and therefore do not define the extent of protection or the extent of the embodiments.

[0029] Throughout the annexed Figures and throughout the detailed description provided in the following, unless the context dictates otherwise, the similar parts or elements are denoted with similar references / numbers, and a corresponding description will not be repeated for brevity.

[0030] As stated in the foregoing, solutions as described herein aim at favouring the turning on of vehicles having electric traction motors even after long periods of shutdown, for example, by limiting the reduction of a state of charge of one or more low-voltage batteries comprised in such vehicles, also, advantageously reducing early battery aging.

[0031] It is noted that solutions as described in the present document may be applied to vehicles having electric traction motors and electric systems comprising a low-volage electric system and a high-voltage electric system.

[0032] Moreover, said high-voltage electric system is configured to transfer energy, for example, by means of a DC-DC converter, from a high-voltage battery comprised therein to a low-voltage battery comprised in said low- voltage system.

[0033] During long periods of shutdown of the vehicle, the low-voltage battery comprised in the low-voltage electric system is discharged due to current leakages which take place in such electric system; therefore, a State of Charge of said battery decreases as a function of the time elapsed from the beginning of the shutdown period of said vehicle.

[0034] Solutions as described in the present document enable recurrently, for instance, periodically, recharging the low-voltage battery even when the vehicle is shut down, thus preventing a reduction of the state of charge of said low-voltage battery below a given threshold.

[0035] For example, said recharging operation may prevent the state of charge of the low-voltage battery to fall below a given threshold, for example, a threshold below which the energy is not sufficient to turn the vehicle on, possibly also considering a desired margin.

[0036] It is noted that the reduction of the state of charge of the low-voltage battery below said threshold may also affect the aging and the useful life of such battery, for example, by increasing aging and shortening said useful life.

[0037] Therefore, said recharging operation prevents the low-voltage battery from discharging during long periods of shutdown of the vehicle, hence, preventing that, due to current leakages, the control unit of the contactors, configured to close the contactors of the high-voltage battery, cannot be turned on, allowing the transferring of energy from the high-voltage battery to the low- voltage battery, for instance, by means of the DC-DC converter.

[0038] The recharging of the low-voltage battery takes place recurrently, for instance, automatically, when the vehicle is turned off, that is, during periods of shutdown of the vehicle.

[0039] Therefore, when the vehicle is turned off, the low- voltage battery is recharged recurrently, for instance, via the DC-DC converter, so as to prevent the state of charge of the low-voltage battery to fall below a given threshold, that is, to decrease to values which are critical for turning the vehicle on and for the aging of said battery.

[0040] It is noted that such a recharging operation may be managed via an Electronic Control Unit (ECU) comprised in the vehicle having the electric traction motor.

[0041] It is noted that such a recharging operation may be performed recurrently, either at regular time intervals, that is, periodically, or at non-regular time intervals.

[0042] Figure 1 illustrates an exemplary evolution 10 of the state of charge SOC of the low-voltage battery as a function of time T, according to embodiments of the present description.

[0043] It is noted that the behaviour of the state of charge SOC shown in Figure 1 is provided by way of example only, and therefore it is not meant to limit the extent of protection of the present application.

[0044] In fact, this Figure illustrates a possible application of the recharging operation, but it is possible to consider other behaviours as well, for example: a behaviour wherein the state of charge SOC of the low-voltage battery starts from a value of state of charge which is higher than a lower threshold THL during the period wherein the electronic control unit is in an active state ECUON; and / or a different succession of the states of the electronic control unit, that is, the active state ECUON, a sleep mode ECUSM, and a wake-up mode ECUawu.

[0045] For example, the behaviour of the state of charge SOC shown in Figure 1 starts from a value of state of charge SOC which is lower than a lower threshold THL, that is, lower than the threshold which identifies the value of state of charge below which the energy is not sufficient to turn the vehicle on, possibly considering a desired margin, and there is no increase of aging or decrease of the useful life of the low-voltage battery.

[0046] Since the electronic control unit of the vehicle is in an active state ECUON, that is, since the vehicle is not shut down, said low-voltage battery may be charged, for example, via the DC-DC converter, by the high-voltage battery, that is, via a standard recharge mechanism Chrgstd.

[0047] For example, said low-voltage battery may be recharged until reaching the value of an upper threshold THH, which may correspond, for instance, to a maximum state of charge or to a desired state of charge which said low-voltage battery may reach, said upper threshold THH being greater, that is, related to a greater value of state of charge, than the lower threshold THL.

[0048] The method according to the present disclosure starts during a phase of shutdown of the vehicle, for instance, in correspondence of the time instant Ti, when the electronic control unit configured to manage the recharging operation switches from the active state ECUON to a sleep mode ECUSM, for example, to a first sleep mode ECUSMI.

[0049] During the shutdown sequence of the vehicle, that is, during the passage of the electronic control unit from the active state ECUON to the first sleep mode ECUSMI, a state-of-charge control unit, for instance, a control logic, a microcontroller, a microprocessor or the like, possibly coincident with the electronic control unit of the vehicle, may be configured to determine a present state-of-charge level of the low-voltage battery SOCsatt_LV•

[0050] Said state-of-charge control unit may be further configured to, if there are no malfunctions or faults in the low-voltage battery and, possibly, on the DC-DC converter, determine a time interval indicative of a duration of the sleep mode ECUSMI based on the present state-of-charge level of the low-voltage battery SOCBatt_Lv which has been determined.

[0051] The moment corresponding to the end of said time interval, for instance, which extends from the time instant Ti to a time instant T2 (that is, in the example of Figure 1, said moment of end of the interval corresponds to the time instant T2), is a moment wherein said electronic control unit switches from the sleep mode ECUSM, for example, from the first sleep mode ECUSMI, to a wake-up mode ECUawu.

[0052] Therefore, said state-of-charge control unit may be configured to determine a wake-up instant, for example, corresponding to the time instant T2, wherein said electronic control unit changes its state, entering in a wake-up mode ECUawu, based on said determined present state of charge level SOCBatt_Lv of the low-voltage battery.

[0053] Figure 2 illustrates an exemplary block 20 configured to determine the time interval TNchrg indicative of a duration of a sleep mode ECUSM as a function of said determined present state of charge level SOCBatt_Lv of the low-voltage battery, according to embodiments of the present disclosure.

[0054] Said block 20 may be configured to: contain a map, for example, the graph of Figure 2, of values of the time interval TNchrg indicative of a duration of a sleep mode ECUSM as a function of values of the state-of-charge level SOCsatt_Lv of the low-voltage battery, for instance, a linear map; receive said present state of charge level SOCBatt_Lv of the low-voltage battery; extrapolate from said map a value of the time interval TNchrg indicative of a duration of a sleep mode, based on the received present state of charge level SOCBatt_Lv of the low-voltage battery; and provide as output said extrapolated value of the time interval TNchrg.

[0055] Therefore, said value of the time interval TNchrg and, consequently, said wake-up instant are determined before the electronic control unit of the vehicle enters a sleep mode ECUSM, for example, the first sleep mode ECUSMI in correspondence of the time instant Ti.

[0056] It is noted that the higher is the present state of charge level SOCBatt_Lv of the low-voltage battery determined before the electronic control unit of the vehicle enters in the first sleep mode ECUSMI, the longer is the time interval TNchrg indicative of the duration of a sleep mode, that is, the longer is the time which elapses before the following wake-up instant (that is, before the end of said time interval TNchrg).

[0057] It is noted that the exemplary map shown in Figure 2 may be obtained via fitting of results proportional to a variation of state of charge between: the state of charge level of the low-voltage battery SOCBatt_Lv determined during the shutdown phase of the vehicle (for example, corresponding to a maximum state of charge or to a desired state of charge which said low-voltage battery can reach), and a minimum state of charge level SOCBatt_Lv_min of the low-voltage battery, that is, the level of state of charge related to the lower threshold THL, which identifies the value of state of charge below which the energy is not sufficient to turn the vehicle on, possibly considering a desired margin, and there is no increase of the aging or decrease of the useful life of the low- voltage battery.

[0058] For example, said variation of state of charge may be divided by the eddy currents, that is, by the parasitic currents, which characterize the low-voltage electric system ieddy.

[0059] For example, the time interval TNchrg indicative of a duration of a sleep mode, that is, the time interval after which there is a switch of the electronic control unit from a sleep mode, for example, the first sleep mode ECUSMI, to a wake-up mode ECUawu, may be obtained via the following equation: iymin)*CBatt_LV

[0060] ‘NChrg ■

[0061] Leddy wherein Csatt_Lv is the electrical capacity of the low- voltage battery comprised in the low-voltage electric system.

[0062] It is noted that said time interval TNchrgmay also be calculated directly via the latter equation, without resorting to the exemplary block 20 containing the map.

[0063] Therefore, during said wake-up mode ECUawu of the electronic control unit, the low-voltage battery comprised in the low-voltage electric system is recharged, for example, by means of the DC-DC converter, by withdrawing energy from the high-voltage battery of the high-voltage electric system.

[0064] It is noted that said recharging operation Chrgsii, which takes place during said wake-up mode ECUawu of the electronic control unit, takes place while the vehicle is turned off, that is, during a period of shutdown of the vehicle, by waking up only the components required for the recharging operation Chrgsii.

[0065] It is noted that such recharging operation Chrgsii is possible since the state of charge of the low-voltage battery has not yet fallen below the lower threshold THL (for example, it is higher than or equal to such lower threshold THL), therefore, it is still possible to activate the control unit of the contactors configured to close the contactors of the high-voltage battery. In response to the recharging operation Chrgsii which takes place during said wake-up mode ECUawu of the electronic control unit, the state of charge of the low- voltage battery increases until it reaches again, for example, at a time instant T3, the state of charge level SOCBatt_Lv of the low-voltage battery determined during the phase of shutdown of the vehicle or, for example, a state of charge level corresponding to a maximum state of charge or to a desired state of charge which said low-voltage battery can reach.

[0066] In fact, it is noted that, albeit Figure 1 shows a situation wherein the state of charge of the low-voltage battery exactly reaches the value of state of charge related to the lower threshold THL, said state of charge of the low-voltage battery may reach state of charge levels higher than or equal to said lower threshold THL, possibly different for each recharging cycle Chrgsii taking place during a wake-up mode ECUawu of the electronic control unit.

[0067] Moreover, said recharging operation Chrgsii which takes place during a wake-up mode ECUawu of the electronic control unit may recharge the low-voltage battery until it reaches: a level of state of charge equal to the state of charge level SOCsatt_Lv of the low-voltage battery determined during the phase of shutdown of the vehicle, for example, as shown in Figure 1; a level of state of charge corresponding to a maximum state of charge, for example, which does not coincide with the state of charge level SOCsatt_Lv determined during the phase of shutdown of the vehicle; or a desired level of state of charge which said low-voltage battery can reach during said recharging operation Chrgsii while the vehicle is shut down, for example, a value lower than, greater than or equal to such state of charge level SOCBatt_Lv determined during the shutdown phase of the vehicle.

[0068] For example, it is possible to determine the level of state of charge to be reached during said recharging operation Chrgsii taking place during a wake-up mode ECUawu of the electronic control unit as a function of a state of charge of the high-voltage battery.

[0069] In response to the reaching of the desired state of charge of the low-voltage battery, for example, according to any one of the options described in the foregoing, for example, in correspondence of the time instant T3, the electronic control unit of the vehicle switches from the wake-up mode ECUawu to a sleep mode ECUSM, for example, to a second sleep mode ECUSM2.

[0070] It is noted that, before the electronic control unit enters the second sleep mode ECUSM2 (or, more generally, any further sleep mode), said state-of-charge control unit may be configured again to determine, if no malfunction or fault is present in the low-voltage battery and, possibly, in the DC-DC converter, a second time interval indicative of a duration of the second (or further) sleep mode ECUSM2, based on the desired state of charge of the low-voltage battery.

[0071] It is noted that, if said desired state of charge of the low-voltage battery coincides with the state of charge level SOCBatt_Lv of the low-voltage battery determined during the phase of shutdown of the vehicle, said state-of-charge control unit may use the time interval which has already been defined for the first sleep mode ECUSMI, without determining a second time interval.

[0072] It is noted that, even in such an instance, the moment corresponding to the end of said second time interval (if determined), for example, extending from the time instant T3 until a time instant T4 (that is, in the example of Figure 1, said moment of end of the second time interval corresponds to the time instant T4), is a moment wherein said electronic control unit switches again from a sleep mode, for example, from the second sleep mode ECUSM2, to a wake-up mode ECUawu.

[0073] Therefore, for example, said wake-up moment corresponds to the time instant T4.

[0074] It is noted that the sequence of sleep modes ECUSM and of wake-up modes ECUawu may continue until the vehicle with the electric traction motor is turned on, hence, until the electronic control unit of the vehicle switches from one of said two modes, that is, from the sleep mode ECUSM or from the wake-up mode ECUawu, to an active state ECUON.

[0075] Therefore, by scheduling a recurring recharging operation Chrgsii of the low-voltage battery as described in the foregoing, it is possible to keep the state of charge of said low-voltage battery within a given safety interval (that is, the state-of-charge interval comprised between the lower threshold THL and the upper threshold THH) during the useful life of said battery, thereby facilitating turning on the vehicle even after long periods of shutdown and reducing the aging of said battery.

[0076] As a result of the recurring recharging operation Chrgsii, the state of charge of the low-voltage battery may exhibit a charging-discharging behaviour, for example, as shown in Figure 1, wherein the discharging operations are the result of the flow of the eddy currents ieddyin the low-voltage electric system, and the charging operations are related to such recurring recharging operations Chrgsii.

[0077] Therefore, solutions as described in the present document refer to a method for charging a fist battery, that is, the low-voltage battery comprised in the low- voltage electric system, comprised in a vehicle having an electric traction motor, said vehicle comprising a second battery, that is, the high-voltage battery comprised in the high-voltage electric system, and an electronic control unit configured to enable a charge transfer, for instance, via said recurring recharging operation Chrgsii, from the second battery to the first battery.

[0078] Said method comprises: determining a state of charge of the first battery, that is, the state of charge level of the low- voltage battery SOCBatt_Lv, during a shutdown of said vehicle, for example, in correspondence of the time instant Th; determining, as a function of said determined state of charge of the first battery SOCsatt_Lv, a time interval, that is, the interval TNchrg which extends, for example, from the time instant Ti to the time instant T2, wherein said electronic control unit is disabled, for instance, it is in a sleep mode ECUSM; and enabling, at the end, for example, in correspondence of the time instant T2, of said time interval TNchrg, via said electronic control unit, that is, during a wake-up mode ECUawu of said electronic control unit, said charge transfer, for example, via said recurring recharging operation Chrgsii, from said second battery to said first battery until the state of charge of the first battery reaches, for example, in correspondence of the time instant T3, a given state of charge, for example, the state of charge corresponding to the upper threshold THH, that is, to the determined state of charge of the first battery SOCsatt_Lv, to a maximum state of charge, or to a desired state of charge which said low-voltage battery can reach. Said method may comprise iterating, until the vehicle is turned on, for example, until said electronic control unit switches to an active state ECUON, the operations of: determining, as a function of said given state of charge THH, preferably a maximum state of charge of the first battery, a further time interval, for example, a further time interval TNchrg which extends, for example, from the time instant T3 to the time instant T4, wherein said electronic control unit is disabled, preferably in a sleep mode ECUSM; and enabling, at the end, for example, in correspondence of the time instant T4, of said further time interval TNchrg via said electronic control unit, that is, during a wake-up mode ECUawu of said electronic control unit, said charge transfer, for example, via said recurring recharging operation Chrgsii, from said second battery to said first battery until the state of charge of the first battery reaches said given state of charge THH.

[0079] Alternatively, if said given state of charge THH is equal to said state of charge of the first battery SOCsatt_Lv determined during the shutdown of said vehicle, said method may comprise iterating, until said vehicle is turned on, for example, until said electronic control unit switches to an active state ECUON, the operations of: disabling, preferably via a sleep mode ECUSM, said electronic control unit during a further time interval, for example, a further time interval TNchrg which extends, for instance, from the time instant T3 to the time instant T4, equal to said time interval TNchrg which extends, for example, from the time instant Ti to the determined time instant T2; and enabling, at the end, for example, in correspondence of the time instant T4, of said further time interval TNchrg via said electronic control unit, that is, during a wake-up mode ECUawu of said electronic control unit, said charge transfer, for example, via said recurring recharging operation Chrgsii, from said second battery to said first battery until the state of charge of the first battery reaches said given state of charge THH.

[0080] Said operation of determining, as a function of said determined state of charge of the first battery SOCBatt_Lv, said time interval TNchrg, for example, the time interval which extends from Ti to T2 or the time interval which extends from T3 to T4, may comprise: determining a limit state of charge, for example, the minimum level of state of charge of the low-voltage battery SOCBatt_Lv_min, that is, the level of state of charge related to the lower threshold THL which identifies the value of state of charge below which the energy is not sufficient to turn the vehicle on, of the first battery allowing the turning on of said vehicle; determining a parasitic current, for instance, the eddy currents ieddy, of a system supplied by said first battery, that is, of the low-voltage electric system; and determining said time interval TNchrg by dividing a result of a subtraction operation between said determined state of charge of the first battery SOCBatt_Lv and said limit state of charge SOCBatt_Lv_min of the first battery, said result being preferably multiplied by a factor equal to an electrical capacity of the first battery Csatt_Lv, by said eddy current ieddy.

[0081] As an alternative to the direct calculation via said equation, said operation of determining, as a function of said determined state of charge of the first battery SOCBatt_Lv, said time interval TNchrg, for example, the interval T1-T2 or the interval T3-T4, may comprise extrapolating from a map 20 containing time intervals TNchrg and respective states of charge of the first battery SOCBatt_Lv, said time interval TNchrg related to said determined state of charge of the first battery SOCBatt_Lv.

[0082] Said map 20 may be obtained by interpolating results obtained via the equation described in the foregoing, that is: by determining a limit state of charge SOCBatt_Lv_min of the first battery which allows turning on said vehicle; by determining an eddy current ieddyof a system supplied by said first battery; and by determining the time intervals TNchrg related to respective states of charge of the first battery SOCsatt_Lv by dividing results of subtraction operations between said respective states of charge of the first battery SOCBatt_Lv and said limit state of charge SOCBatt_Lv_min of the first battery, said results being preferably increased by a factor equal to an electrical capacity of the first battery Csatt_Lv, by said eddy current ieddy.

[0083] It is noted that, in embodiments of the present description, the operation of charge transfer Chrgsii from the second battery to the first battery may be performed via a DC-DC converter.

[0084] It is noted that, in embodiments of the present description, said first battery has a first supply voltage, for example, a supply voltage of about 12 volt, and said second battery has a second supply voltage higher than the first supply voltage of the first battery, for example, a supply voltage of 800 volt.

[0085] If, advantageously, the desired level of state of charge of the low-voltage battery is considered to be the state of charge level of the low-voltage battery SOCBatt_Lv determined during the shutdown phase of the vehicle, and if the level of state of charge of the low- voltage battery to be reached during the discharge due to the eddy currents ieddyis considered to be the level of state of charge related to the lower threshold THL, both the state of charge level SOCBatt_Lv determined during the shutdown phase of the vehicle and the time interval TNchrg indicative of a duration of a sleep mode ECUSM may be stored in a non-volatile memory, for example, comprised in a power-latch of the electronic control unit of the vehicle.

[0086] Said stored time interval TNchrgmay be used for programming a timer so that, when said timer reaches a threshold equal to said stored time interval TNchrgand the vehicle is shut down, the electronic control unit may switch from a sleep mode ECUSM THL to a wake-up mode ECUaWU•

[0087] For example, said electronic control unit may, in response to the reaching of the threshold equal to said time interval TNchrg stored by the timer, activate again a communications network of the low-voltage electric system and, when said communications network is active, may activate (for example, if there are no malfunctions or faults in the low-voltage battery and, possibly, in the DC-DC converter) the control unit of the contactors configured to close the contactors of the high-voltage battery (for example, comprised in said electronic control unit), allowing, for example, via the DC-DC converter, the energy transfer from the high-voltage battery comprised in the high-voltage electric system to the low-voltage battery comprised in the low-voltage electric system.

[0088] When, during a wake-up mode ECUawu, the state of charge of the battery reaches the stored level of state of charge SOCBatt_Lv, a maximum time related to the duration of the wake-up mode ECUawu is reached, or when a malfunction or a fault critical for the recharging operation is detected, the wake-up mode ECUawu ends, and the electronic control unit switches to a sleep mode ECUSM.

[0089] For example, during said passage of the electronic control unit from the wake-up mode ECUawu to the sleep mode ECUSM, the supply of the high-voltage electric system is interrupted, for example, by disabling the control unit of the contactors.

[0090] It is noted that, if the passage of the electronic control unit from the wake-up mode ECUawu to the sleep mode ECUSM is due to the reaching of a maximum time related to the duration of the wake-up mode ECUawu or to the detection of a malfunction or fault critical for the recharging operation, it may be advantageous to recalculate the time interval as a function of the actually reached state of charge of the low-voltage battery, so as to avoid discharging said battery below the lower threshold THL.

[0091] It is noted that, in such cases, the recalculated time interval and the state of charge actually reached may be stored in the non-volatile memory, for example, by overwriting the previous values, so as to have subsequent charging-discharging cycles with a state of charge of the low-voltage battery which varies within an interval extending from the lower threshold THL to said value of state of charge which has actually been reached.

[0092] Alternatively, the recalculated time interval may be stored in the non-volatile memory to be used exclusively for the following wake-up of the electronic control unit, so as to have subsequent chargingdischarging cycles with a state of charge of the low- voltage battery which varies in a time interval which extends from the lower threshold THL to the stored level of state of charge SOCBatt_Lv.

[0093] It is noted that said operation of storing and programming the timer may be performed even in other instances, for example, in the cases which have been described in the foregoing, but it has to be repeated each time a further time interval is determined.

[0094] Therefore, the method as described herein may comprise: storing the determined time interval TNchrg and / or the determined state of charge of the first battery SOCBatt_Lv in a non-volatile memory; and / or programming, via the determined time interval TNchrg, a timer configured to detect the end, for example, in correspondence of the time instant T2 or the time instant T4, of said time interval TNchrg.

[0095] If a determined time interval suffers from errors of any kind, a security unit may enable detecting, for example, via a control unit of the low-voltage battery (for example, via an Intelligent Battery System, IBS), whether the state of charge of the low-voltage battery decreases, during a sleep mode, below a given emergency threshold, for example, a threshold related to a value of state of charge which is lower than or equal to the lower threshold THL.

[0096] If a detection is made that said state of charge of the low-voltage battery has fallen below said emergency threshold, it is possible to automatically reactivate the communications network of the low-voltage electric system and, when said communications network is active, it is possible to perform the recharging operation, for example, by reactivating the electronic control unit in such a way as to activate the control unit of the contactors, before the time interval has elapsed.

[0097] The security procedure described in the foregoing may also be enabled in response to detecting, by the security unit, the fact that for any reason the communications on the CAN ("Controller Area Network") have not been interrupted in response to the switching off of the high-voltage electric system and, therefore, the low-voltage battery keeps on consuming energy.

[0098] For example, even in this case, the security procedure may be enabled when the state of charge of the low-voltage battery falls, during a sleep mode, below a given emergency threshold, for example, a threshold related to a value of state of charge lower than or equal to the lower threshold THL.

[0099] Therefore, the method described herein may comprise: defining an emergency state of charge allowing the turning on of said vehicle, that is, the state of charge related to the given emergency threshold; monitoring, for example, via said control unit of the low-voltage battery, a state of charge of the first battery (that is, the low-voltage battery) SOC during said time interval TNchrg, that is, during a sleep mode ECUSM of the electronic control unit; and enabling, if the monitored state of charge SOC of the first battery is lower than the emergency state of charge, said charge transfer, for example, via the recurring recharging operation Chrgsii, from said second battery to said first battery until the state of charge of the first battery reaches said given state of charge THH.

[0100] Therefore, the solution described in detail herein enables obtaining a method for charging one or more low- voltage batteries in a vehicle having an electric traction motor even during shutdown periods of the vehicle.

[0101] Thus, it can be understood that the solution described herein may favour the turning on of vehicles having electric traction motors even after long periods of shutdown.

[0102] It is noted that embodiments of the present description refer to vehicles having an electric traction motor, said vehicles comprising at least one first battery, that is, a low-voltage battery comprised in the low-voltage electric system, at least one second battery, that is, a high-voltage battery comprised in the high-voltage electric system, and at least one electronic control unit configured to enable a charge transfer, for example, via said recurring recharging operation Chrgsii, from the at least one second battery to the at least one first battery; wherein said at least one electronic control unit is configured to perform the steps of the method described in the foregoing.

[0103] Moreover, the aging of the low-voltage battery (which is due to the decrease of the state of charge thereof) is reduced, thereby increasing the useful life of said battery.

[0104] Without prejudice 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.

[0105] The extent of protection is defined by the annexed claims.

Claims

CLAIMS1. Method for charging a first battery comprised in a vehicle having an electric traction motor, said vehicle comprising a second battery and an electronic control unit configured to enable a charge transfer (Chrgsii) from the second battery to the first battery; said method comprising: determining a state of charge of the first battery (SOCBatt_Lv) during a shutdown of said vehicle (Ti); determining, as a function of said determined state of charge of the first battery (SOCBatt_Lv), a time interval (TNchrg; T1-T2) wherein said electronic control unit is disabled (ECUSM); and enabling, at the end (T2) of said time interval (TNchrg; T1-T2) via said electronic control unit (ECUawu), said charge transfer (Chrgsii) from said second battery to said first battery until the state of charge of the first battery reaches (T3) a given state of charge (THH).

2. Method according to claim 1, comprising: storing said determined time interval (TNchrg; T1-T2) and / or said determined state of charge of the first battery (SOCBatt_Lv) in a non-volatile memory; and / or programming, via said determined time interval (TNChrg; T1-T2), a timer configured to detect the end (T2) of said time interval (TNchrg; T1-T2).

3. Method according to claim 1 or claim 2, wherein said method comprises iterating, until said vehicle is turned on (ECUON), the operations of: determining, as a function of said given state of charge (THH), preferably a maximum state of charge of the first battery, a further time interval (TNchrg; T3-T4) wherein said electronic control unit is disabled (ECUSM),preferably in a sleep mode; and enabling, at the end (T4) of said further time interval (TNchrg; T3-T4) via said electronic control unit (ECUawu), said charge transfer (Chrgsii) from said second battery to said first battery until the state of charge of the first battery reaches said given state of charge (THH); wherein, preferably said method comprises: storing said determined further time interval (TNchrg; T3-T4) and / or said given state of charge (THH) in a non-volatile memory; and / or programming, via said determined further time interval (TNchrg; T3-T4), a timer configured to detect the end (T4) of said further time interval (TNchrg; T3-T4).

4. Method according to claim 1 or claim 2, wherein said given state of charge (THH) is equal to said state of charge of the first battery (SOCBatt_Lv) determined during the shutdown of said vehicle; and wherein said method comprises iterating, until said vehicle is turned on (ECUON), the operations of: disabling (ECUSM), preferably via a sleep mode, said electronic control unit during a further time interval (TNchrg; T3-T4) equal to said determined time interval (TNchrg; T1-T2); and enabling, at the end (T4) of said further time interval (TNchrg; T3-T4) via said electronic control unit (ECUawu), said charge transfer (Chrgsii) from said second battery to said first battery until the state of charge of the first battery reaches said given state of charge (THH); wherein, preferably said method comprises: reading said determined further time interval (TNchrg; T3-T4) and said given state of charge (THH) from a non-volatile memory configured to store saiddetermined time interval (TNchrg; T1-T2) and said state of charge of the first battery (SOCsatt_Lv) determined during the shutdown of said vehicle; and / or programming, via said determined further time interval (TNchrg; T3-T4), a timer configured to detect the end (T4) of said further time interval (TNchrg; T3-T4).

5. Method according to any of the previous claims, wherein the operation of determining, as a function of said determined state of charge of the first battery (SOCBatt_Lv), said time interval (TNchrg; T1-T2; T3-T4) comprises: determining a limit state of charge (SOCBatt_Lv_min; THL) of the first battery allowing the turning on of said vehicle; determining an eddy current (ieddy) of a system supplied by said first battery; and determining said time interval (TNchrg; T1-T2; T3-T4) by dividing a result of a subtraction operation between said determined state of charge of the first battery (SOCBatt_Lv) and said limit state of charge (SOCBatt_Lv_min) of the first battery, said result being preferably multiplied by a factor equal to an electrical capacity of the first battery (Csatt_Lv), by said eddy current (Ieddy)•6. Method according to any of claims 1 to 4, wherein the operation of determining, as a function of said determined state of charge of the first battery (SOCBatt_Lv), said time interval (TNchrg; T1-T2; T3-T4) comprises extrapolating from a map (20) containing time intervals (TNchrg) and respective states of charge of the first battery (SOCsatt_Lv), said time interval (TNchrg; Ti- T2; T3-T4) related to said determined state of charge of the first battery (SOCsatt_Lv),wherein said map (20) is obtained: determining a limit state of charge (SOCBatt_Lv_min) of the first battery allowing the turning on of said vehicle; determining an eddy current (ieddy) of a system supplied by said first battery; and determining said time intervals (TNchrg; T1-T2; T3-T4) related to respective states of charge of the first battery (SOCsatt_Lv) by dividing results of subtraction operations between said respective states of charge of the first battery (SOCsatt_Lv) and said limit state of charge (SOCBatt_Lv_min) of the first battery, said results being preferably multiplied by a factor equal to an electrical capacity of the first battery (Csatt_Lv), by said eddy current (ieddy).

7. Method according to any of the previous claims, wherein said charge transfer (Chrgsii) from said second battery to said first battery is performed via a DC-DC converter.

8. Method according to any of the previous claims, wherein said first battery has a first supply voltage, preferably a supply voltage of 12 volt, and said second battery has a second supply voltage higher than the first supply voltage of the first battery, preferably a supply voltage of 800 volt.

9. Method according to any of the previous claims, comprising: defining an emergency state of charge allowing the turning on of said vehicle; monitoring a state of charge of the first battery (SOC) during said determined time interval (TNchrg; Ti- T2); andenabling, if the monitored state of charge of the first battery (SOC) is lower than the emergency state of charge, said charge transfer (Chrgsii) from said second battery to said first battery until the state of charge of the first battery reaches said given state of charge (THH).

10. Vehicle having an electric traction motor, said vehicle comprising at least one first battery, at least one second battery, and at least one electronic control unit configured to enable a charge transfer (Chrgsii) from the at least one second battery to the at least one first battery; wherein said at least one electronic control unit is configured to perform the steps of the method according to any of the previous claims.

Images