Method for managing the temperature of a battery for a motor vehicle

Abstract

The invention relates to a method for managing the temperature of a traction battery (1) of a motor vehicle (10) comprising a system (3) for controlling the temperature of the traction battery, the method comprising steps of: measuring a maximum temperature of the traction battery at the instant t, then comparing with at least one threshold temperature among a threshold stop temperature "TemperatureStopCooling", a threshold activation temperature "TemperatureActivateCooling", a first threshold temperature "TemperatureStartDerating" and a second threshold temperature "TemperatureNoPower", wherein, prior to the measurement step, it includes re-evaluating at least one threshold temperature as a function of an instantaneous state of health of the traction battery (1) at the instant t, evaluated by a management system (2) of the battery and a predefined target aging level at this instant t.

Description

DESCRIPTION TITLE: METHOD FOR MANAGING THE TEMPERATURE OF A BATTERY FOR AN AUTOMOBILE VEHICLE

[0001] The present invention claims priority from French application No. 2409229 filed on 29.08.2024, the content of which (text, drawings and claims) is incorporated herein by reference. TECHNICAL FIELD OF THE INVENTION

[0002] The invention relates, in general, to the technical field of thermal management of traction batteries for an electric or hybrid motor vehicle. In particular, the invention relates to a method for managing the temperature of a traction battery, especially a lithium traction battery, for an electric or hybrid motor vehicle. PREVIOUS STATE OF THE ART

[0003] Today, a traction battery, particularly a lithium battery, used in an electric or hybrid vehicle consists of a set of electrical cells. These electrical cells are assembled into a cell module, and several cell modules are assembled to form the traction battery.

[0004] To ensure thermal management of the traction battery, several components are integrated into the vehicle. Internally, a cooling system is most often implemented: air cooling, gas cooling, or water cooling (with a dedicated water circuit). Some traction batteries rely exclusively on natural convection. Externally, a cooling circuit typically includes a conventional cooling system (with or without a cooler), which can vary in complexity depending on the components to be cooled inside the vehicle and the cost.

[0005] Furthermore, to ensure the thermal management of the traction battery, the maximum power (alternatively, the maximum current) allowed during charging, discharging, or regenerative braking by the traction battery is gradually limited from a first threshold temperature, "TemperatureStartDerating," until it drops to OKW at a second threshold temperature, "TemperatureNoPower," which is higher than the first threshold temperature (see Figure 2). This constitutes a primary control function. Most often, these first and second threshold temperatures are set to limit degradation of the traction battery (which is more significant when the traction battery is at a high temperature). These threshold temperatures also protect against safety risks associated with high temperatures.

[0006] Furthermore, the cooling system is activated when the traction battery deviates from its optimal operating range, according to a second control function as follows. When the traction battery's maximum temperature (T_BatMax) exceeds a certain activation threshold (TemperatureDActivationDuCooling), the cooling system can be activated. The cooling system remains activated until the maximum temperature (T_BatMax) falls below a shutdown threshold (TemperatureDArrêtDuCooling) and / or after a predetermined time.

[0007] Most often, the activation (and deactivation) temperatures of the cooling system are constant and fixed once and for all. The activation temperature, "CoolingActivationTemperature," is set to reduce overconsumption related to the cooling system, thereby minimizing the traction battery's charging time and allowing it to remain within its full performance range. By design, the "CoolingActivationTemperature" is therefore close to the traction battery's first threshold temperature, "StartDeratingTemperature."

[0008] For example, if a traction battery reduces its available power from 45°C (Max battery temperature), the cooling system can be advantageously activated from 40°C.

[0009] The above currently allows for a compromise to be made to preserve battery durability by applying the two control functions as early as possible (if the cooling system is not sufficiently activated or if power degradation occurs too late, this results in a rise in the average temperature of the traction battery, leading to its accelerated degradation compared to the expected usage of the traction battery), to preserve full battery performance by applying the two control functions as late as possible (the concept of performance includes not only traction performance (including regenerative braking), but also charging performance (which translates into charging time)), and to minimize overconsumption by the vehicle by applying cooling as late as possible (if the cooling system is activated too often,This leads to increased electrical consumption (activation of the cooler, cooling pumps, compressor, etc.), which can result in a loss of range in the case of electrified vehicles.

[0010] A traction battery thermal management system is most often sized and activated to cover the worst-case scenario for electric vehicles: high annual mileage and severe weather conditions. The sustainability commitment for an electric or hybrid vehicle user is therefore—most of the time—ensured by these strategies (and the intrinsic characteristics of the traction battery chemistry) for all users, but at the expense of: increased vehicle energy consumption to activate the cooling system, a greater occurrence of power degradation, and changes in the vehicle's operating conditions (particularly average ambient temperature).

[0011] While the above is consistent for a "worst-case" user, it becomes far too restrictive for less demanding users who drive their electric or hybrid vehicle less frequently, or who live in a milder climate. For these users, the power limitation is too severe, or their energy consumption is too high relative to their optimal needs. DESCRIPTION OF THE INVENTION

[0012] The invention aims to remedy all or part of the drawbacks of the state of the art by proposing in particular a solution enabling optimal thermal management of a traction battery of an electric or hybrid motor vehicle, regardless of the type of user of said electric or hybrid motor vehicle.

[0013] To this end, according to a first aspect of the invention, a method for managing the temperature of a traction battery of a motor vehicle is proposed, comprising a battery management system, a thermal regulation system connected to the traction battery, the method comprising the following steps: • Measurement of a maximum temperature at time t of the traction battery, then • Comparison with at least one threshold temperature among a threshold stop temperature "CoolingStopTemperature", a threshold activation temperature "CoolingActivationTemperature", a first threshold temperature "StartDeratingTemperature" and a second threshold temperature "NoPowerTemperature", wherein, prior to the maximum temperature measurement step, the process includes a preliminary step of re-evaluation at time t of at least one threshold temperature among the threshold stop temperature "CoolingStopTemperature", the threshold activation temperature "CoolingActivationTemperature", the first threshold temperature "StartDeratingTemperature" and the second threshold temperature "NoPowerTemperature", re-evaluation being a function of an instantaneous health status SOH(BMS) at time t of the traction battery evaluated by the battery management system and a predefined target aging level SOH_Target at that time t.

[0014] According to one embodiment, the target aging level is defined in relation to a mileage travelled and / or a number of years elapsed since the start of the life of the traction battery and / or a number of MWh travelled in the traction battery.

[0015] According to one embodiment, the instantaneous health state and the target aging level are at least one of an energy health state, a European health state as defined by the Euro7 standard, a capacity health state, a power health state and a resistance health state.

[0016] According to one embodiment, the re-evaluation step of the first threshold temperature "TemperatureStartDerating" and the second threshold temperature "TemperatureNoPower" evolve according to an increasing function of the gap between the instantaneous health state and the target aging level.

[0017] According to one embodiment, the step of re-evaluating the threshold stop temperature "CoolingStopTemperature" and the threshold activation temperature "CoolingActivationTemperature" evolve according to an increasing function of the gap between the instantaneous health state and the target aging level.

[0018] According to one embodiment, during the re-evaluation step, the re-evaluation is a function of an instantaneous state of charge of the traction battery estimated by the battery management system.

[0019] According to one embodiment, during the reassessment stage, the reassessment is also a function of the instantaneous state of health of the traction battery, taken alone.

[0020] According to one embodiment, during the re-evaluation step, at least one of the threshold temperatures among the threshold shutdown temperature, the threshold activation temperature, the first threshold temperature and the second threshold temperature is remotely re-evaluated.

[0021] According to another aspect of the invention, a traction battery for a motor vehicle is provided, comprising a battery management system, a thermal regulation system connected to the traction battery, in which the battery management system further comprises a computer arranged to implement the method having at least one of the preceding technical characteristics.

[0022] According to yet another aspect of the invention, a motor vehicle is provided comprising a traction battery, a battery management system, a thermal regulation system connected to the traction battery including an electric machine, the traction battery having one of the preceding technical characteristics. BRIEF DESCRIPTION OF THE FIGURES

[0023] Other features and advantages of the invention will become apparent from the following description, with reference to the attached figures, which illustrate: [Fig. 1]: a schematic view of an electric or hybrid motor vehicle comprising a traction battery and a thermal regulation system for the latter; [Fig. 2]: a curve illustrating the maximum power available as a function of temperature for a traction battery; [Fig. 3]: a curve illustrating the target health status of a traction battery as a function of the time elapsed since the beginning of its life; [Fig. 4]: a curve illustrating the evolution of different threshold temperatures by the implementation of an embodiment of a temperature management method for a traction battery according to the invention.

[0024] For clarity, identical or similar elements are identified by identical reference symbols across all figures. DETAILED DESCRIPTION OF A METHOD OF IMPLEMENTATION

[0025] Figure 1 schematically illustrates an electric or hybrid motor vehicle 10 comprising, as is known per se, a powertrain including an electric traction machine. The motor vehicle 10 further comprises a traction battery 1 electrically connected to the electric machine of the powertrain. The traction battery 1 includes a battery management system 2 [also called BMS, from the English acronym for "Battery Management System"]. The motor vehicle 10 further comprises a thermal circuit 4 connecting a heat exchanger 41 of the traction battery 1 to a thermal regulation system 3 of the motor vehicle 10. The latter will allow the traction battery 1 to be cooled or heated.

[0026] We will now describe in detail a temperature management method for a traction battery according to the invention which is implemented within the motor vehicle 10 previously described.

[0027] In a manner known per se, the temperature management method for a traction battery according to the invention comprises a step of measuring an instantaneous maximum temperature T_BatMax of the traction battery 1. This measurement is performed by the battery management system 2. Following this measurement of the maximum temperature T_BatMax, the temperature management method for a traction battery according to the invention compares it with the various threshold temperatures, which are, in order, the cut-off temperature "CoolingStopTemperature", the activation temperature "CoolingActivationTemperature", the first threshold temperature "StartDeratingTemperature", and the second threshold temperature "NoPowerTemperature". Figure 2 illustrates the order of these threshold temperatures.

[0028] As a reminder, if the maximum temperature T_BatMax measured is less than the threshold stop temperature "CoolingStopTemperature", the temperature management method of a traction battery according to the invention proceeds to a stop of the thermal regulation system 3 if the latter is activated.

[0029] If the maximum temperature T_BatMax measured is greater than the activation threshold temperature "TemperatureDActivationDuCooling", the temperature management method of a traction battery according to the invention activates the thermal regulation system 3 if the latter is not activated.

[0030] If the measured maximum temperature T_BatMax exceeds the first threshold temperature "TemperatureStartDerating", the traction battery temperature management method according to the invention triggers a degradation of the maximum power supplied by the traction battery 1. This degradation increases as the maximum temperature T_BatMax increases. The temperature management method of a traction battery according to the invention cuts off the power supplied by the traction battery 1 when the maximum temperature T_BatMax becomes greater than or equal to the second threshold temperature "TemperatureNoPower".

[0031] Prior to the step of measuring the instantaneous maximum temperature TbatMax, the temperature management method for a traction battery according to the invention performs a step of re-evaluating at least one of the threshold temperatures among the threshold shutdown temperature "CoolingStopTemperature", the threshold activation temperature "CoolingActivationTemperature", the first threshold temperature "StartDeratingTemperature", and the second threshold temperature "NoPowerTemperature". The re-evaluation is a function of an instantaneous health status SOH(BMS) of the traction battery 1 evaluated by the battery management system 2 and a target aging level SOH_Target at that instant as given by the curve in Figure 3. This curve illustrates the evolution of the aging level SOH_Target of the traction battery 1 over time since the beginning of its service life.

[0032] Alternatively, the SOH_Target aging level is defined in a non-limiting manner with respect to mileage traveled and, optionally, with respect to the number of years elapsed since the start of its life cycle (production of the first battery, or delivery of the first vehicle to the user) and / or the number of MWh consumed in traction battery 1 (possibly within each electrical cell, if a health status is calculated for each electrical cell). This SOH_Target aging level can be set by taking into account any under-declaration of energy or energy reserve considered during its life cycle.

[0033] In another variant, the target aging level SOH_Target of traction battery 1 is also defined with regard to regulatory or consumer requirements, by representatively interpolating between: 100% at the beginning of its life (BOL), a target SOCE (European state of health as defined by Euro 7) level (or any parameter of the same nature) after the number of years (or kilometers traveled, or energy that has passed through traction battery 1) set by the regulations. The target SOCE is the maximum of the following SOCE values: a target SOCE interpolated (linearly or non-linearly) on an age basis of traction battery 1 by Compared to regulatory targets at BOL, 5 years, 8 years, etc.; a target SOCE interpolated (linearly or non-linearly) on a virtual mileage basis (as defined by the Euro 7 standard) of the traction battery I compared to regulatory targets at BOL, 5 years, Sans, etc., a virtual mileage as defined by the Euro 7 standard (sum of the actual mileage and the stationary cycle time (V2X) converted into equivalent kilometers, according to the definition adopted by the Euro 7 standard). This interpolation is not necessarily linear, in order to take into account the shape of the aging curve, the degradation slope of which tends to decrease over time (before the traction battery 1 enters sudden failure).

[0034] Thus, the temperature management method for a traction battery according to the invention allows the traction battery 1 to operate at higher temperatures at full power when the instantaneous state of health (SOH(BMS)) is significantly higher than the target aging level. Specifically, the power degradation activation, or the activation of the thermal regulation system, is applied starting at higher maximum temperatures T_BatMax.

[0035] On the other hand, this preserves the durability of traction battery 1 when the instantaneous state of health (SOH(BMS)) is significantly lower than the target aging level (SOH_Target). Specifically, power degradation activation, or activation of the thermal management system, is applied when maximum temperatures (T_BatMax) fall below these levels.

[0036] The instantaneous health state SOH(BMS) and the aging level SOH_Target are chosen at least one from an energy health state, a European SOCE health state as defined by the Euro7 standard, a capacity health state, a power health state and a resistance health state.

[0037] As an alternative embodiment of the traction battery temperature management method according to the invention, the step of re-evaluating the first threshold temperature "TemperatureStartDerating" (from which the maximum permissible power (or current) during charging, discharging, or regenerative braking decreases or degrades) and the second threshold temperature "TemperatureNoPower" (from which the maximum permissible power (or current) during charging, discharging, or regenerative braking decreases or degrades) discharge or regenerative braking becomes zero) evolve according to an increasing function of the gap between the instantaneous health state SOH(BMS) and the target aging level SOH_Target.

[0038] In another variant of the traction battery temperature management method according to the invention, a performance of the thermal regulation system 3 evolves according to a decreasing function of the gap between the instantaneous health state SOH(BMS) and the target aging level SOH_Target.

[0039] In another variant of the traction battery temperature management method according to the invention, the step of re-evaluating the threshold stop temperature "CoolingStopTemperature" and the threshold activation temperature "CoolingActivationTemperature" evolve according to an increasing function of the gap between the instantaneous health state SOH(BMS) and the target aging level SOH_Target.

[0040] In another embodiment of the traction battery temperature management method according to the invention, the re-evaluation step also depends on an instantaneous state of charge (SOC) of the traction battery 1, estimated by the battery management system 2. Thus, the cutoff temperature threshold "CoolingCutOffTemperature" and the activation temperature threshold "CoolingActivationTemperature" are re-evaluated based on the instantaneous state of charge (SOC) at time (t). For example, in the case of a high instantaneous state of charge (SOC), more cooling is required, conversely, in the case of a low instantaneous state of charge, less cooling is required.For some battery chemistries (such as NMC - nickel manganese cobalt), the rate of degradation being greater at high state of charge, the first threshold temperature "TemperatureStartDerating" can be modulated according to the average state of charge, allowing an adaptation of the cooling temperatures according to this average state of charge.

[0041] In another embodiment of the traction battery temperature management method according to the invention, the re-evaluation step also depends on the instantaneous health status (SOH(BMS)) of the traction battery 1, taken The user can choose between less frequent thermal regulation at the beginning of the battery's life, as long as the traction battery remains in good enough condition, or a more conservative thermal regulation strategy. In the first case, the user can minimize consumption (in the vehicle or at the charging point) by less frequently activating the thermal regulation system. In the second case, the user benefits from the traction battery's full performance over a wider and longer operating range.

[0042] Figure 3 illustrates a re-evaluation of the threshold temperatures previously mentioned during the implementation of certain variants of the temperature management process of a traction battery according to the invention previously described.

[0043] In another embodiment of a traction battery temperature management method according to the invention, the re-evaluation step is performed based on a difference between an average temperature observed by the traction battery 1 over its entire lifespan to date, and an average design temperature taken into account to determine the thermal regulation and power degradation strategies. In other words, an implementation of this embodiment of the traction battery temperature management method according to the invention aims to adapt the activation conditions for power degradation and thermal regulation of the traction battery 1, based on the difference between an average temperature observed by the traction battery 1 over its entire usage up to time "t" and the average design temperature.Furthermore, according to an alternative embodiment of this method for managing the temperature of a traction battery according to the invention, the activation of the thermal regulation is delayed based on a damage criterion that depends, without limitation, on the average temperature, the average state of charge (SOC), the number of kWh exchanged, the age, etc. This damage criterion is compared to a target damage criterion based solely on age and mileage.

[0044] In yet another embodiment of a traction battery temperature management method according to the invention, the step of re-evaluating at least one of the threshold temperatures among the threshold stop temperature "CoolingStopTemperature", the threshold activation temperature "CoolingActivationTemperature", the first threshold temperature "StartDeratingTemperature" and the second threshold temperature “TemperatureNoPower” is performed remotely.

[0045] 11 It follows from the above that the implementation of the temperature management method of a traction battery according to the invention as previously described makes it possible to adapt the thermal regulation of the traction battery 1 of an electric or hybrid motor vehicle 10, and, consequently, the aging and degradation of said traction battery 1, to the actual conditions of use of the motor vehicle 10.When the actual degradation of the traction battery is lower (respectively higher) than a maximum permissible degradation (with regard to the guaranteed commitment to the user, regulatory requirements, or the state of the art) for a given period of use, the temperature management method of a traction battery according to the invention aims to activate the thermal regulation of the traction battery 1 more quickly by increasing (respectively reducing) the first threshold temperature "TemperatureStartDerating" of the activation of power degradation and / or the activation threshold temperature "TemperatureDActivationDuCooling" of the thermal regulation system of the traction battery 1. This makes it possible to minimize the consumption of the thermal regulation system and to optimize a charging time (respectively improve durability with regard to the target).

[0046] Naturally, the invention described above is by way of example. It is understood that a person skilled in the art is capable of carrying out different embodiments of the invention without departing from the scope of the invention.

[0047] 11. It is emphasized that all characteristics, as they emerge to a person skilled in the art from the present description, drawings, and attached claims, even if concretely they have only been described in relation to other specific characteristics, both individually and in any combinations, may be combined with other features or groups of features disclosed herein, provided that this has not been expressly excluded or that technical circumstances make such combinations impossible or meaningless.

Claims

DEMANDS 1. A method for managing the temperature of a traction battery (1) of a motor vehicle (10) comprising a battery management system (2), a thermal regulation system (3) connected to the traction battery, the method comprising the steps of: - Measurement of a maximum temperature at time t of the traction battery, then - Comparison with at least one threshold temperature among a threshold stop temperature "CoolingStopTemperature", a threshold activation temperature "CoolingActivationTemperature", a first threshold temperature "StartDeratingTemperature" and a second threshold temperature "TemperatureNoPower", wherein, prior to the maximum temperature measurement step, the process includes a preliminary step of re-evaluation at time t of at least one threshold temperature among the threshold stop temperature "TemperatureDArrêtDuCooling", the threshold activation temperature "TemperatureDActivationDuCooling", the first threshold temperature "TemperatureStartDerating" and the second threshold temperature "TemperatureNoPower", re-evaluation being a function of an instantaneous health status SOH(BMS) at time t of the traction battery (1) evaluated by the battery management system (2) and of a predefined target aging level SOH_Target at that time t.

2. A method according to claim 1, wherein the target aging level is defined in relation to a mileage traveled and / or a number of years elapsed since the start of the traction battery's life and / or a number of MWh traveled in the traction battery.

3. A method according to any one of claims 1 to 2, wherein the instantaneous health state and the target aging level are at least one of an energy health state, a European health state as defined by Euro7, a capacity health state, a power health state and a resistance health state.

4. A method according to any one of claims 1 to 3, wherein the re-evaluation step of the first threshold temperature "TemperatureStartDerating" and the second threshold temperature "TemperatureNoPower" evolve according to an increasing function of the gap between the instantaneous health state and the target aging level.

5. A method according to any one of claims 1 to 4, wherein the step of re-evaluating the threshold stop temperature "CoolingStopTemperature" and the threshold activation temperature "CoolingActivationTemperature" evolve according to an increasing function of the gap between the instantaneous health state and the target aging level.

6. A method according to any one of claims 1 to 5, wherein, during the re-evaluation step, the re-evaluation is a function of an instantaneous state of charge of the traction battery estimated by the battery management system.

7. A method according to any one of claims 1 to 6, wherein, during the re-evaluation step, the re-evaluation is also a function of the instantaneous state of health of the traction battery, taken alone.

8. A method according to any one of claims 1 to 7, wherein, during the re-evaluation step, at least one of the threshold temperatures among the threshold shutdown temperature, the threshold activation temperature, the first threshold temperature and the second threshold temperature is remotely re-evaluated.

9. Traction battery (1) for motor vehicle (10) comprising a battery management system (2), a thermal regulation system (3) connected to the traction battery, wherein the battery management system further comprises a computer arranged to implement the method according to any one of claims 1 to 8.

10. Motor vehicle (10) comprising a traction battery (1), a battery management system (2), a thermal regulation system (3) connected to the traction battery comprising an electric machine, characterized in that the traction battery is according to claim 9.

Images