METHOD FOR CONTROLLING A CURRENT BASED ON A MODULAR INCREASE COUNTER FOR A BATTERY SYSTEM

Abstract

The present invention relates to a method for controlling the maximum charging current of a battery system (1) comprising an energy storage element (10), the method comprising the calculation of a variable counter (CP) in a variation range delimited by a maximum limit (LimH) for a first maximum continuous current (IDC1) applicable during a determined duration, the calculation of the counter (CP) comprising the determination of a corrective component of an integrator of the instantaneous current (ICR) configured so as to control the incrementation and decrementation of the counter (CP) as a function of the value of the instantaneous current (ICR) with respect to at least the first maximum continuous current (IDC1) and the control of the current as a function of the counter (CP). Figure 1.

Description

Title of the invention: METHOD FOR CONTROLLING A CURRENT BASED ON A MODULAR INCREASE METER FOR A BATTERY SYSTEM

[0001] The field of the invention relates to a method for controlling the current of a battery system, in particular of an electrified vehicle.

[0002] Power battery systems, in particular for electrified vehicles, conventionally comprise a set of electrochemical cells connected in series and / or parallel in the system. The term energy storage element refers to an electrochemical cell or an assembly of cells that can be connected in series and / or in parallel. Conventionally, in electromobility applications, the energy storage elements are lithium-ion type electrochemical cells. In operation, these cells are likely to degrade if they are not used under nominal operating conditions, i.e. within the thermal, current and voltage limits defined by the cell manufacturers.Indeed, if the temperature is too low or if currents are too high, the electrodes of a cell can become saturated with lithium atoms on the surface, which can lead to the formation of dendrites that cause internal short circuits. The management of cell charge and discharge currents must be carried out under safe conditions while ensuring optimal energy management and the least restrictive use of the battery possible, particularly in terms of charging time and driving range.

[0003] Lithium transport in a negative graphite electrode is generally slower than in positive electrodes and, therefore, is the limiting phenomenon of the charging current. This phenomenon is called lithium deposition or lithium plating, also referred to as "Lithium Plating" in English. Too high a lithium concentration can lead to the formation of dendrites and cause an increase in internal resistance, or even a short circuit. During charging, lithium ions are reduced to lithium metal on the surface of the graphite structure during the exchange of electrons. The rate of reduction of lithium ions is proportional to the current and diffusion in the graphite structure follows the diffusion laws. The diffusion rate depends on the lithium metal concentration gradient and a diffusion coefficient, which depends on the state of charge, temperature and aging of a cell.Fick's law governs the diffusion of lithium ions into the various components of the battery, such as the electrolyte and electrodes. This law is well . known to those skilled in the art in the field of batteries. For example, the following bibliographic reference describing principles of application of Fick's law in the field of lithium-ion cells may be cited: "Wu Musheng, Xu Bo, Ouyang Chuying. Physics of electron and lithium-ion transport in electrode materials for Li-ion batteries. Chinese Physics B, 2016, 25(1): 018206". Further, patent document EP-A1-2266181 may be cited describing an adaptive charging method based on a technique for estimating a diffusion time and a surface lithium concentration from the diffusion time, the cell capacity and the measured charging current. Then, from the concentration, a charging current is calculated. This document teaches measuring the diffusion time during a relaxation phase from the measurement of an open-circuit voltage following the application of a direct current for a fixed duration.This technique for estimating the surface lithium concentration concerns charges connected to the terminal, commonly called “Plug-in” charges. This technique is therefore not applicable to regenerative braking due to the driving dynamics and the impossibility of imposing cell relaxation, particularly in the case of a vehicle with a fully electric motor.

[0004] However, to improve energy management, the majority of electrified vehicles are equipped with a regenerative braking system in order to optimize the energy management of the vehicle. The management of the powertrain is then provided on the one hand to promote regenerative electric braking and on the other hand to control maximum charging current values ​​specific to braking situations while respecting the electrochemical and safety constraints linked to lithium-ion storage cells.

[0005] Document WO-A1-2022237476 is known from the state of the art, which teaches a solution for calibrating charging current pulse tables from electrochemical and thermal models established experimentally. These electrochemical models also include a law of diffusion coefficient of lithium ions at the electrodes. This document teaches a principle of control by current pulse of a given duration, for example 10 seconds, of which a stopping condition can be dependent on the cell voltage relative to a high voltage threshold, an electrode potential value between the negative electrode and the separator or a cell temperature. These pulse tables are intended to control maximum currents respecting the electrochemical constraints of the cells, in particular with regard to the lithium deposition.

[0006] Patent document WO-A 1-2022032460 is also known, describing a solution comprising a method for detecting lithium plating on a battery cell electrode comprising determining a potential value in real time of the negative electrode and in which, if this potential becomes less than or equal to a threshold of zero volts, the method detects a lithium plating. This document teaches the use of an embedded model in a vehicle to determine this potential as a function of the charging current, state of charge and temperature. This document teaches a principle of controlling the charging current aimed at reducing the current value as a function of this potential. The disadvantage of a real-time calculation model is that it is particularly energy-intensive.

[0007] The current control tables described in the documents mentioned above provide information on current values ​​that can be applied from an estimation of the instantaneous state of charge and the temperature of a cell, generally for a relaxed state of the cell. However, although the estimation of the state of charge of a cell can be considered as the image of the lithium saturation level of the core of the graphite structure of the electrode, the saturation level of the surface area of ​​the electrode is not always identical to that of the core of the graphite structure, in particular during the rolling phase during which the dynamics of the electrical stresses during charging and discharging modify the concentration level of the lithium atoms on the surface.This implies that, following an electrical charge in regenerative braking, the surface may be at an already critical saturation level, higher than that estimated from the cell's State of Charge (SOC) or, following a discharge, may be at a level lower than that estimated from the State of Charge. In the first case, there is a risk of lithium deposition if the current resulting from the table obtained experimentally is applied. In the second case, the opportunity for energy recovery is limited.

[0008] There is therefore a need to optimize current control solutions for the charging and discharging phases of a battery. One objective of the invention is to overcome the aforementioned problems. Another objective of the invention is to implement an optimized current control solution increasing the opportunities for controlling the maximum charging current, in particular in the regenerative braking phases, while limiting the risk of lithium deposition. One objective of the invention is to increase the recharging capacity of a regenerative braking system.

[0009] More specifically, the invention relates to a method for controlling the maximum current of a battery system comprising an energy storage element, the method being implemented by a control unit of said battery system, the method comprising the following steps of measuring electrical parameters of the storage element, determining a first current delivered by a first direct current table taking said measured electrical parameters as input, and according to the invention the method further comprises the following steps: - the determination of a maximum limit corresponding to the quantity of electricity exchanged with the storage element by applying the value of the first current for a first duration, - the calculation of a variable counter within a variation range delimited by the maximum limit, the calculation of the counter comprising the determination of a corrective component of an integrator of the instantaneous current configured so as to control the incrementation and decrementation of the counter as a function of the value of the instantaneous current relative to at least the first current, - controlling the current of the storage element comprising providing maximum current information applicable to the storage element, when the counter is less than the maximum limit, said information being the first maximum current and, when the counter is equal to the maximum limit, said information is a second direct current delivered by a second direct current table taking said measured electrical parameters as input.

[0010] The first and second direct current tables record charging currents or discharging currents, called “Boost” currents.

[0011] The method according to the invention may include the following additional characteristics, alone or in combination:

[0012] - The calculation of the meter involves the determination of a balance current in function of the counter value and the second current according to the following relationship: IEQ= CP / LhnH * IDC2, CP being the instantaneous value of the counter, LimH the maximum limit and IDC2 being the second current, the comparison of the instantaneous current with respect to the equilibrium current, when the instantaneous current is lower than the equilibrium current, the corrective component is configured to decrement the counter.

[0013] - The corrective component is configured to decrement the counter according to a first correction dependent on the difference between the instantaneous current and the equilibrium current.

[0014] - The corrective component is configured to increment the counter when the instantaneous current is greater than the second direct current.

[0015] - The calculation of the meter involves the comparison of the instantaneous current with respect to at least two predetermined current ranges between the first current and the second current, and selecting a second predetermined correction based on the result of the comparison to calculate the corrective component.

[0016] - The calculation of the counter involves the determination of a first ratio defined by the ratio between the instantaneous current and the first maximum current, the determination of a third correction delivered by a correction table taking the first ratio as input to calculate the corrective component.

[0017] - The calculation of the meter involves the comparison of the instantaneous current with respect to at least two predetermined current ranges between the first current and the second current, the calculation of a fourth correction corresponding to a second ratio defined by the ratio between the instantaneous current and a maximum limit selected according to the result of the comparison to calculate the corrective component.

[0018] - The counter calculation and current control steps are controlled during a regenerative braking phase or an acceleration phase of an electrified vehicle.

[0019] A battery system is contemplated comprising an energy storage element and a control unit configured specifically for implementing the current control method according to any of the preceding embodiments.

[0020] Further contemplated is an electrified vehicle comprising such a battery system.

[0021] The invention further provides a control unit comprising means specifically configured to implement the current control method according to the invention, a computer program comprising instructions which, when the program is executed by the control unit, cause the control unit to implement any one of the embodiments of the current control method, and a computer-readable recording medium comprising instructions which, when executed by a computer, cause the computer to implement the current control method according to the invention.

[0022] The invention is a software solution, with simplified calculation, implementing a lithium reduction estimator providing an optimal estimate taking into account the phases of decrease in the concentration on the surface of the electrode to increase the charging opportunities in regenerative braking at a maximum current value. In particular, the estimator is advantageous in that it allows the incrementation and decrementation of the current control counter to be modulated as a function of the intensity of the current actually commanded. More concretely, in the case of regenerative braking on a gentle slope and lifting the foot, at low current, the counter will be incremented little or not at all because in this situation the rate of reduction of the lithium is similar to the rate of diffusion in the body of the electrode. The invention is a low-cost real-time calculation estimator requiring few computing resources.The invention makes it possible to increase the driving range of an electrified vehicle.

[0023] Other characteristics and advantages of the present invention will appear more clearly on reading the detailed description which follows, comprising embodiments of the invention given as non-limiting examples and illustrated by the appended drawings, in which:

[0024] [Fig.l] schematically represents a battery system according to the invention.

[0025] [Fig.2] schematically represents a negative electrode structure illustrating the principle of diffusion of lithium atonias in a graphite particle structure.

[0026] [Fig.3] represents graphs illustrating the evolution of the lithium concentration on the surface of a graphite structure of a negative electrode for different continuous charging currents at different states of charge of the storage element.

[0027] [Fig.4] represents the modeling of the lithium concentration according to a simplified function implemented by the method according to the invention for a continuous charging current of fixed duration.

[0028] [Fig.5] represents a first embodiment of the calculation of the counter according to the invention.

[0029] [Fig.6] represents a second embodiment of the calculation of the counter according to the invention.

[0030] [Fig.7] represents a third embodiment of the calculation of the counter according to the invention.

[0031] [Fig.8] represents a fourth embodiment of the calculation of the counter according to the invention intended to decrement the counter during a charge.

[0032] [Fig.9] represents an example of a charging sequence illustrated by curves representing a simulation of the lithium concentration, the calculation of the meter according to the invention and the charging current.

[0033] [Fig. 10] represents by a functional block diagram the current control method according to the invention.

[0034] [Fig. 11] represents an electrified vehicle intended for the implementation of the invention.

[0035] The invention applies to electrified vehicles, that is to say comprising an electric motor machine and power electronics, 100% electric or hybrid, preferably motor vehicles, but not only such as aircraft, tractors, bicycles, ships.

[0036] [Fig.l] schematically represents an energy storage system 1 comprising an energy storage element 10 comprising at least one electrochemical cell 11 in accordance with the invention. The storage element 10 may comprise a plurality of cells 11 or groups of cells (also called cell clusters) electrically connected in parallel and / or in series.

[0037] An electrochemical cell is an electrical energy accumulator having two terminals and having a voltage of a few volts, most often between 2.3V and 4.2V, approximately. The cells can be of the Lithium-ion type (a lithium Nickel Manganese Cobalt oxide NMC or a lithium iron phosphate LFP can be cited as examples of positive electrode active materials), Nickel Cadmium (Ni-cd), Nickel-Metal-Hydride (Ni-MH) for example. More precisely, a Lithium-ion cell is composed mainly of a porous positive electrode, a porous negative electrode, a separator and an electrolyte (which can be liquid, polymeric or solid). The operating principle of a lithium-ion cell is based on the reversible exchange of lithium ions between the two porous electrodes.

[0038] The storage system 1 further comprises means for measuring, estimating or sensing electrical parameters, including at least one current sensor 12 capable of measuring or estimating a current value ICR in real time passing through the storage element 10, a voltage sensor and a temperature sensor for cells 11 or each cell 11 of the energy storage element 10. The storage system 1 further comprises a control unit 13 (also called ECU for “Electronic Control Unit” or BMS for “Battery Management System”).

[0039] An objective of the invention is to control maximum currents temporarily in the charging or discharging phase and for this it is necessary to know an estimate of the lithium concentration of the surface of the structure of a negative electrode or a thermal state of the internal mechanical structure of a cell between an electrode and the associated current collector. The invention is based on a principle of modeling the phenomenon of lithium diffusion on the surface of an electrode, in particular Fick's law applied to lithium cells. For this purpose, the control unit 13 is provided with an integrated circuit computer and electronic memories, the computer and the memories being configured to execute the current control method according to the invention. But this is not obligatory. Indeed, the computer could be external to the battery control unit, while being coupled to the latter.The control unit 13, according to the invention, can be produced in the form of software modules (or computer modules (or even “software”)), or electronic circuits (or “hardware”), or even a combination of electronic circuits and software modules.

[0040] The invention proposes a current control method based on the physical properties of lithium diffusion on the surface of an electrode in which the diffusion of lithium on the surface of an electrode is modeled and simplified according to a first-order differential equation. This equation has the effect of simplifying the calculation of the lithium concentration on the surface of the graphite particle structure by calculating a representative counter in the charging phase of the chemical process of lithium reduction on the surface of an electrode. The counter can be a variable expressed by a quantity of electricity exchanged with the storage element or by a ratio of a quantity of electricity compared to a maximum limit. The counter is updated in the charging and discharging phases of the battery.

[0041] In this embodiment, an estimator 15 of the control unit 13 of the battery system calculates a counter from a current integrator. In addition, the estimator 15 determines a variation range representative of a lithium concentration level and delimited by a maximum limit LimH and a limit minimum. Current control is based on the value of this counter relative to the maximum limit to control the maximum current allowed in regenerative braking phases. The counter is variable within a range of positive and negative values. This simplified estimation function 15 requires reduced computing resources and is particularly suitable for real-time estimation during highly dynamic driving phases, such as regenerative braking.

[0042] To illustrate the lithium deposition phenomenon, in [Fig.2], a graphite negative electrode structure is schematically shown for different charge rates. Diagram 2a shows the zero current electrode where the surface concentration is uniform to the internal concentration of the graphite structure. Diagram 2b shows the electrode for moderate charge current where the surface concentration is higher than the internal concentration but remains below a saturation level. Diagram 2c shows the electrode for high charge current where lithium deposits form on the surface of the electrode. The reduced lithium is proportional to the current and cannot be inserted in its entirety. Lithium deposition appears, represented by the oval-shaped patterns. Diagram 2d shows the electrode for discharge current. In discharge, the lithium concentration is lower than that of the core of the electrode.

[0043] From these observations, it is considered that current values, when they are higher than the rate of lithium reduction and diffusion in the electrode core, will cause lithium deposition on the surface of the electrode. Other values, when they are lower than the rate of lithium reduction and diffusion in the electrode core, will cause surface deposition equivalent to the saturation level of the electrode core. In other situations, when the surface is already at a deposition level higher than that of the electrode core, current values ​​lower than a so-called reduction equilibrium current cause delithiation of the electrode surface. This latter situation appears for example in relaxation, in a low-current charging phase or in discharge, after a charging phase having saturated the electrode surface.One objective of the process is to optimize the estimation of the meter and current control to increase the opportunities for controlling the charging current to maximum values, particularly in regenerative braking.

[0044] The lithium concentration at the electrode surface can be expressed by a first-order differential equation that indicates the evolution of the concentration curve for a direct current profile of a fixed duration as a function of time. In graph 3a, the curves in the upper part illustrate concentration curves Cx for three different current profiles, in the lower part, from a state of charge of 0% (SOC) of the total capacity of a lithium-ion cell. In the Figure 3b, the curves illustrate the situation for a state of charge of 70% of the total capacity of a lithium-ion cell. The concentration level is expressed on a scale of 0% and 100% of the saturation level. The x-axis is the duration. Three direct current profiles are represented for fixed durations of 10 seconds, 30 seconds and 180 seconds. It is observed that for durations of 10 seconds and 30 seconds, current values ​​of 350A and 180A are applicable respectively until reaching the saturation level at the end time of the fixed duration. It is further observed that the concentration value at the start time of the pulse is dependent on the state of charge of the cell. For example, for 0% capacity, the core and electrode surface concentration is at 0% of the saturation level and for a 70% capacity condition, the surface and structure concentration level is at 70% of the saturation level.The assumption is that the concentration expressed as a ratio of the saturation level is proportional to the state of charge of a cell.

[0045] Furthermore, as illustrated in graph 3c, if a current profile involves an immediately successive charging and discharging phase, the lithium concentration at the surface of the structure in the graph reaches a lithium concentration level lower than that of the internal structure of the electrode, due to the phenomenon of reduction in the lithium concentration, also referred to as "delithiation", of the surface during discharge. This phenomenon implies that in reality it is possible to apply, following a discharge, a charging current for a duration greater than that defined in the calibration tables.The method according to the invention makes it possible, in one embodiment, to judiciously exploit this situation to control either a maximum current of a value greater than that provided in the current table for the same fixed duration, in this example 235A for 10 seconds, or the maximum current for a duration greater than that provided by the calibration table, in this example 110A for 20 seconds.

[0046] From these observations, calibration information for direct current tables is obtained either by numerical modeling or by experimental means for a fixed duration, taking as input electrical parameters including the state of charge (SOC) and the temperature of an energy storage element, a cell or a group of cells. These direct current tables deliver current values ​​applicable during the fixed duration. An experimental protocol carried out on cells under controlled conditions can be a numerical modeling from the lithium concentration equations described above. Another experimental protocol can be the measurement of a reference potential of the negative electrode corresponding to a voltage measured between the negative electrode and a so-called reference electrode, generally made of lithium, connected to the electrolyte.During charging, when this voltage reaches 0 volts, this condition indicates that the saturation level has been reached.

[0047] A first table delivers values ​​of a first continuous charging current applicable for the first duration at most as a function of measured electrical parameters. The current values ​​are applicable until a saturation level of lithium deposition is reached on the surface of a negative electrode of said storage element at the end of the first duration. The measured parameters include the state of charge SOC and the temperature of a storage element, for a range of [0%, 100%] in SOC and for a temperature range [-20°C, 60°C] for example. It is envisaged to obtain several first tables for different applicable durations, for example durations between 10 seconds and 180 seconds, for example a table for a duration of 10 seconds, another table for a duration of 30 seconds and another table for a duration of 180 seconds.These are current tables designed for a dynamic load situation while a vehicle is running, such as regenerative braking for example.

[0048] A second table, for controlling a direct current for a second given duration, differs from the first table in that the second applicable duration of the current is greater than that of the first table or tables, i.e. greater than several minutes, between several minutes and possibly several hours. The direct current value delivered by the second table corresponds to a lithium reduction rate close to that of the diffusion of atoms in the core of the electrode structure. This second current can be controlled constantly, i.e. until the voltage limit of a cell corresponding to the so-called “Cut-off voltage” is reached without the lithium deposition phenomenon appearing. These are current values ​​suitable for charging at a terminal, for example.The second table provides current values ​​applicable without risk of lithium deposition depending on the SOC state of charge and temperature parameters of a storage element, for a range of [0%, 100%] in SOC and for a range of [-20°C, 60°C] for example. It is envisaged to obtain several second tables for durations of 180 seconds or more.

[0049] In [Fig.4], the first-order differential equation corresponding to the lithium concentration at the surface of a graphite structure is represented by the curve C1 and a linear regression implemented to estimate the concentration by a simplified calculation method is represented by the curve C2. The principle of the method for calculating the meter is to assimilate the lithium concentration curve by a linear regression of incrementation of a quantity of electricity generated by a continuous charging current. As a result, it is possible to obtain an image of the lithium concentration level by a simplified calculation by measuring the quantity of electricity necessary to reach the lithium saturation threshold, where the threshold corresponds to the maximum current value applied during the associated fixed duration. The linear regression C2 presents the advantage that the lithium concentration estimate is underestimated compared to the actual evolution illustrated by the Cl curve. This calculation method is a solution requiring few computer resources that can be integrated into an on-board vehicle control unit. It also has the advantage of securing the current control protocol because the calculated level is lower than the actual concentration level.

[0050] With reference to [Fig.l], the control unit 13 comprises, stored in memory, at least a first direct current table 151 and a second direct current table 152. The control unit may comprise a plurality of tables 151 and a plurality of tables 152 for different durations. For example, first tables 151 are stored for direct currents associated with first durations DI of 10 seconds, 30 seconds and 180 seconds. Second tables 152 are stored for direct currents of longer durations, for example, 360 seconds or more. First tables and second tables specific to charging currents or discharging currents may also be provided.The control unit 13 is configured to deliver maximum current values ​​applicable during the first and second durations specific to each table as a function of instantaneous electrical parameters P including the state of charge and the temperature of the storage element.

[0051] It is further envisaged that the control method also applies to ensure the safety of the positive electrode during a discharge with regard to the temperature of the internal mechanical elements of a cell. A temperature model similar to the diffusion principle is applicable. Another type of first table may therefore be a table delivering direct discharge current values ​​applicable for a given duration until reaching, from a reference state of the storage element, a critical temperature or undervoltage level of a positive electrode of said storage element at the end of the first duration.The person skilled in the art will be able to obtain, either by numerical modeling or by experimental means, calibration information for direct current tables for a fixed duration, taking as input electrical parameters including the state of charge (SOC) and the temperature of an energy storage element, a cell or a group of cells.

[0052] Conventionally, the control unit 13 of the battery system further comprises an estimator of the aging state of the cells providing an SOH parameter representative of the aging state. The estimator 15 further comprises a table delivering a current correction factor as a function of the SOH aging parameter. The current correction factor is provided to correct a value of the current IDC1, IDC2 delivered by the first and second tables 151 and 152 respectively.

[0053] Furthermore, the estimator 15 comprises a calculation module 153 receiving in real time the current value ICR passing through the storage element 10 of the battery system 1. This calculation module 153 has the function of calculating a counter CP corresponding to a quantity of electricity exchanged with the storage element during a calculation period. The counter CP is implemented by a current integrator over the calculation period where by convention, a charge current is of negative value and a discharge current of positive value.

[0054] The calculation period begins, for example, when the storage system is started, in particular when an electrified vehicle is started. The CP counter is delimited within a variation range by a maximum limit LimH and a minimum limit. The CP counter is a parameter expressed in Ah taking positive values ​​to count the charged energy and negative values ​​for the discharged energy.

[0055] Furthermore, according to the invention, the counter CP is calculated in real time and is based on a corrective component of an integrator of the instantaneous charging current ICR configured so as to control the incrementation and decrementation of the counter CP during charging. The incrementation and decrementation are determined as a function of the value of the instantaneous charging current ICR relative to at least the first current IDC1. The corrective component has the function of adapting the incrementation value INC when the current ICR is distinct from the value of the current IDC1 delivered by the first table 151. Indeed, when the current ICR is lower than the first current IDC1, the maximum limit LimH, which is determined from the first table 151, underestimates the lithium saturation level, which would have the effect of limiting the recharging opportunities.For example, for currents that can be applied for 30 seconds until saturation is reached, the maximum limits, expressed in amperes.h, are distinct and have values ​​higher than the 10-second current limit. For these currents, the corrective component allows the meter incrementation to be attenuated so that the surface saturation estimate is closer to the actual saturation. Several variants for implementing the corrective component of the INC incrementation will be described in more detail later in the description to optimize current control.

[0056] Furthermore, the estimator 15 may be configured to calculate at least one or more counters for the protection of the current-limiting electrode. For example, a first counter may be provided for monitoring the negative electrode of a storage element in the charging phase and a second counter for monitoring the positive electrode of a storage element in the discharging phase. A counter is preferably variable in a range of positive and negative values, or only in positive values ​​in an absolute value calculation mode. Each counter is associated with tables of charging or discharging currents according to the case for determining the limit values ​​of the meter variation range and the predetermined current ranges.

[0057] Furthermore, a module 154 calculates the maximum limit LimH of the variation range from the first table 151 determining the maximum applicable current IDC1 and the first associated duration Dl, LimH=IDCl*Dl. This information is obtained as a function of the instantaneous electrical parameters P including the state of charge SOC and temperature during the current control of the battery system. The limit LimH corresponds to the quantity of electricity charged from the reference state of the storage element to reach the saturation level. For example, for a continuous charging current of 350A for a fixed duration of 10 seconds, the first limit LimH is equal to approximately 1 Ah, for a continuous charging current of 150A for a fixed duration of 30 seconds, the first limit is equal to 1.25 Ah

[0058] In another case, if tables of maximum discharge currents associated with a fixed duration are recorded in the memory of the control unit, it may be provided that the first limit LimH is calculated from one of these tables. This may be, for example, a so-called “Boost” current table making it possible to increase the acceleration of the vehicle after a recharging phase. The invention therefore provides sets of tables specific to discharge currents for fixed durations and therefore a variation range specifically provided for the so-called Boost discharge currents. These discharge current tables are obtained experimentally or by digital modeling according to techniques known to those skilled in the art, in particular by monitoring, under controlled discharge conditions, the value of the voltage of a cell in relation to an undervoltage threshold or a thermal threshold.

[0059] It will be noted that the maximum limit used to frame the counter value remains identical throughout the current control duration. A current table is selected, for example table 151, which determines the value of the limit as well as the value of the corrective component which depends on the value of the load current relative to the current delivered by the same table used to calculate the limit.

[0060] Furthermore, the control unit 13 comprises a current controller 16 comprising a control function 161 delivering current control information CCI, which may be a current setpoint value, a maximum current value authorized at the given time or an authorized electrical power value in charge or discharge. The function 161 takes as input information comprising at least the current values ​​delivered by the first and second direct current tables 151 and 152, and the value of the CP counter calculated by the calculation module 153. The CCI information is delivered via communication means to other electrical systems consuming and / or generating energy, for example a voltage converter, electric motor, charger.

[0061] More precisely, the control function 161 monitors that the counter CP is included in the variation range delimited by the maximum limit LimH. If the counter CP is strictly lower (in absolute value) than the value of the first limit LimH then the current control information CCI is the direct current value delivered by the first table 151 applicable during the first fixed duration associated with said first table, for example 10 seconds, 30 seconds or 180 seconds. This configuration makes it possible on the one hand to increase the energy recovery potential by using the maximum current by taking the lithium concentration state, and on the other hand makes it possible to secure the operation of the storage system with regard to the lithium deposition. In discharge, this configuration makes it possible to control a so-called “Boost” current.

[0062] If the parameter CP is equal to the first limit LimH, then the current control information CCI is the direct current value delivered by the second table 152. For example, if the driving situation is followed by several successive regenerative braking operations, the estimator of the CP counter makes it possible to evaluate the surface condition taking into account these repetitive braking operations, independently of the state of charge of the storage system, and makes it possible to detect lithium saturation and prevent the application of the maximum current.

[0063] In [Fig.5], a functional block diagram represents a first embodiment of the determination of the corrective component of the charging current integrator to determine an increment value INC when calculating the CP counter and controlling the current of the battery system. This first embodiment makes it possible to adjust the increment of the counter according to a comparison of the instantaneous charging current with predetermined DC current ranges in calibration. In this example, the charging current ICR is compared with respect to four predetermined current ranges. The maximum limit LimH is fixed and is determined by the 10-second current table.

[0064] In a first block 51, the calculation of the corrective component takes as input charging current values ​​IDC1, IDC3 and IDC4 delivered by three direct current tables each associated with a fixed application duration which are respectively, in this non-limiting example 10 seconds, 30 seconds and 180 seconds. At equivalent temperature and state of charge, IDC1 is greater than IDC3, IDC3 is greater than IDC4, and IDC4 is greater than IDC2. The current values ​​IDC1, IDC3 and IDC4 are applicable until a saturation level of lithium deposition is reached on the surface of a negative electrode at the end of the first respective duration. Another table delivers the current IDC2 corresponding to a lithium reduction rate close to that of the diffusion of atoms in the core of the electrode structure. This second current can be controlled constantly, that is to say until the voltage limit of a cell corresponding to the so-called “Cut-off voltage” without the phenomenon of lithium deposit appearing.

[0065] Furthermore, the current table IDC1 is associated with a current correction F1, for the current table IDC2 is associated with a current correction F2, for the current table IDC3 is associated with a current correction F3 and for the current table IDC4 is associated with a current correction F4. These correction values ​​adapt the incrementation of the current integrator of the counter CP in the following manner:

[0066] If the instantaneous charging current ICR is between IDC1 and IDC3 then the correction Fl is selected and the incrementation of the integrator is calculated according to the following relation: INC=ICR*F1*SP, where INC is the incrementation, ICR the value of the charging current, Fl the correction and SP the duration of the step of the current integrator. If the instantaneous charging current ICR is between IDC3 and IDC4 then the correction F3 is selected and the incrementation of the integrator is calculated according to the following relation: INC=ICR*F3*SP. If the instantaneous charging current ICR is between IDC2 and IDC4 then the correction F4 is selected and the incrementation of the integrator is calculated according to the following relation: INC=ICR*F4*SP. If the instantaneous charging current ICR is between 0 and IDC2 then the F2 correction is selected and the increment of the integrator is calculated according to the following relation: INC=ICR*F2*SP.Block 51 may compare the ICR current against at least two current ranges delimited by at least IDC1 and IDC2, a first less than IDC2 and a second between IDC2 and IDC1, or three or more ranges for finer segmentations.

[0067] Furthermore, the current control method implements in a second block 52 the calculation of the counter CP in which CP is incremented at each calculation step by the incrementation value INC according to the following relation: CP(t)=CP(tl) - INC(t).

[0068] Then, the current control method implements a current control step where the counter CP(t) is used by a third functional block 53 of the current control function which compares the value of the counter CP(t) to the maximum limit LimH. If CP(t) is equal to the limit LimH, this means that the lithium saturation level at the surface of an electrode has been reached. The CCI information then commands a current limitation setpoint equal to the value IDC2 delivered by the associated current table. If CP(t) is lower than the limit LimH, this means that the saturation level has not yet been reached. The CCI information then commands a current limitation setpoint equal to the value IDC1 which corresponds to the maximum charging current configured in calibration delivered by the 10-second current table.

[0069] Furthermore, it should be noted that this embodiment also applies to the control of a discharge current with respect to a positive electrode. which is the limiting one of the current intensity. Identical to the charge current, the discharge current is compared to current ranges determined by discharge current tables to then determine the value of a correction to be applied for the incrementation or decrementation of the counter.

[0070] In [Fig.6], a functional block diagram represents a second embodiment of the determination of the corrective component of the charging current integrator for the calculation of the CP counter and the current control of the battery system. This second embodiment differs from the first in that a single direct current table, here the 10-second current table, is used to determine the correction of the current integrator. For this purpose, a first block 61a has the function of determining a ratio R defined by the ratio between the instantaneous current ICR and the first maximum current IDC1, where R=ICR / IDC1, and of determining a correction RCOR delivered by a correction table taking the ratio R as input to calculate the corrective component. The ratio makes it possible to compare the current ICR with the current IDC1.The correction table scales correction values ​​between 1.5 and 0, for example for ratio values ​​between 0% and 120% for charge currents and 0% and -120% for discharge currents. In absolute value, the current intensity is close to the value of the first maximum current IDC1, and the more the correction increases the increment of the counter. Conversely, for low currents, the correction decreases the increment of the counter. The correction has the effect of adapting the variation of the counter according to the actual current measured and of optimizing the lithium reduction estimator.

[0071] Then, the increment INC is calculated according to the following relation: INC=ICR*RCOR*SP, where ICR is the instantaneous load current, RCOR the correction and SP the duration of the step of the current integrator. Then, the current control method implements the calculation of the CP counter and the current control by the two functional blocks 62 and 63 identically to the first embodiment.

[0072] In [Fig.7], a functional block diagram represents a third embodiment of the determination of the corrective component of the charging current integrator for the calculation of the CP counter and the current control of the battery system. Unlike the first and second embodiments, the incrementation of the counter is determined by a ratio defined by the relationship between the instantaneous charging current and a maximum limit determined from a direct current table associated with a duration. This ratio has the effect of adapting the incrementation of the CP counter according to the value of the instantaneous charging current. Then, the counter is compared to a variation range defined by a ratio of [0.1] or [0%, 100%] and no longer to a limit defined in quantity of electricity.

[0073] In this third embodiment, three direct current tables taking into account input the temperature parameters T and state of charge SOC and associated with three durations of 10s, 30s and 180s are implemented. Each table makes it possible to determine a maximum limit expressed in amperes.h. A first limit Liml0 corresponds to the current value 10s multiplied by the duration 10s, a second limit Lim30 corresponds to the current value 30s multiplied by the duration 30s and a third limit Lhnl80 corresponds to the current value 180s multiplied by the duration 180s. According to the current control method of the invention, a block 71 calculates a scaled increment value INC based on the result of the comparison of the value of the instantaneous charging current ICR with respect to current ranges delimited by the currents 10s, 30s and 180s. For each range, an increment value is equal to the ratio of the charge current to the maximum limit associated with the current range.More precisely, if the instantaneous charging current ICR is less than IDC4, then the corrective component of the current integrator is equal to l / Liml80, if the instantaneous charging current ICR is between IDC4 and IDC3, then the corrective component of the current integrator is equal to l / Lhn30, and if the instantaneous charging current ICR is between IDC3 and IDC1, then the corrective component of the current integrator is equal to l / Lhnl80. The block 71 can compare the current ICR with respect to at least two current ranges delimited by at least IDC1, a first less than IDC4 and a second between IDC4 and IDC1, or to three or more ranges for finer segmentations.

[0074] An increment value is calculated at each calculation step and the counter is updated by block 72 according to the value of the previous step and the new increment value, similarly to the first and second embodiments. In a third block 73, the counter is compared to the maximum limit which is this time expressed by the ratio 1 or 100% in order to determine the maximum current information.

[0075] The current control method implements the control step where, if the CP counter is equal to 1, this indicates that the lithium saturation level is reached and the maximum authorized current setpoint CCI information is the current IDC2 delivered by the direct current table that can be applied constantly. If the CP counter is less than 1 or 100%, the maximum authorized current setpoint CCI information is the current IDC1 delivered by the direct current table of duration 10s.

[0076] Furthermore, it should be noted that this third embodiment also applies to the control of a discharge current with respect to a positive electrode which is the one limiting the intensity of the current. Identical to the charging current, the currents and the limits used for the comparison of the instantaneous current with current ranges and to calculate the corrective component of the counter increment are determined from discharge current tables.

[0077] In [Fig.8], a functional block diagram represents a fourth embodiment of the determination of the corrective component of the charging current integrator for calculating the CP counter and current control of the battery system. This fourth mode comprises a functional block decrementing the counter when the charging current is lower than a so-called equilibrium current IEQ, i.e. corresponding to a lithium reduction rate which is lower than the diffusion in the core of the negative electrode. This has the effect, when the lithium saturation level at the surface of the electrode is higher than that of the core of the electrode structure, of reducing the lithium concentration at the surface of the electrode. This makes it possible to estimate more precisely the lithium concentration at the surface of the electrode in a relaxation phase situation and when the charging current is low, lower than the so-called equilibrium current.This fourth embodiment is complementary and not exclusive to the first three embodiments described previously. It has the advantage of increasing the opportunities for controlling an IDC1 charging current in regenerative braking.

[0078] More precisely, in accordance with the control method, the equilibrium current IEQ is calculated from the value of the direct current IDC2 delivered by the second direct current table to which the ratio CP(t) / LimH is applied in order to take into account the lithium saturation level of the surface, where CP(t) is the instantaneous value of the counter and LimH is the maximum limit of the variation range of the counter, these two variables being expressed in amperes.h. In addition, a block 81 compares the current ICR to the equilibrium current IEQ. If the instantaneous charging current ICR is greater than the equilibrium current IEQ, then the incrementation of the counter INC is positive and can be determined according to one of the three embodiments described previously. Conversely, if the charging current ICR is less than the equilibrium current IEQ, the lithium concentration decreases. The counter is decremented according to a value INC equal to (ICR-IEQ) *SP, where SP is the duration of the integration step.

[0079] Then, the current control method implements the calculation of the CP counter and the current control by the two functional blocks 82 and 83 identically to the first embodiment.

[0080] This fourth mode also applies to the control of a discharge current. The current IDC2 is delivered by a discharge current table and the decrementation of the counter is determined identically as a function of the difference between the instantaneous discharge current and the current IDC2.

[0081] In [Fig.9], a current control simulation for a charging sequence according to the method of the invention is shown from an initial charge state of 70%. The The upper graph represents a simulation of a lithium concentration level on the surface of an electrode of an energy storage element referenced in a variation range between 0 and 1. A first solid line curve illustrates the value of the lithium concentration and a second dotted line curve the concentration level of the core of the structure of the negative electrode. The horizontal line positioned at 0.85 represents a saturation level at 50% of the limit for the surface of the electrode.

[0082] In the middle graph, the values ​​of the charging current ICR of the charging sequence are represented. A first dotted horizontal line is the value of a current II associated with a duration of 10 seconds, a second horizontal line is a current I2 associated with a duration of 30 seconds and a third horizontal line is a current I3 associated with a duration of 180 seconds.

[0083] In the lower graph, the meter is shown during the charging sequence and is expressed in quantity of electricity. The maximum limit LimH is indicated on the y-axis. Two embodiment variants of the meter are indicated by a CPI curve and a CP2 curve. CPI where the meter depends on the corrective component allowing to control the incrementation according to the value of the instantaneous charging current ICR with respect to the current II. For CP2, the corrective component allows to control the incrementation as well as the decrementation when the charging current is lower than the equilibrium current.

[0084] In a first phase PHI of the sequence, the charging current ICR is controlled to the value II which corresponds to the maximum current value delivered by the first table associated with a pulse duration of 10 seconds. The counters CPI and CP2 are incremented until reaching the value of the maximum limit after 10 seconds. After this instant, in a second phase PH2, the control command controls the maximum current setpoint to the current value 13 because the counters CPI and CP2 have a value equal to the maximum limit LimH. The current table delivering the value 13 is associated with a pulse duration of 180 seconds. It will be noted that in the implementation of the current control method, the direct current table 13 for a charging pulse of 180 seconds can be replaced by the direct current table applicable for longer durations. It is observed that during the phase PH2, the counters CPI and CP2 remain stable.

[0085] In this example in the following phase PH3, a charging current having a ratio value of 50% of the current 13 is applied, which has the effect of decrementing the counter CP2 and making its value converge towards a ratio of 50% of the maximum limit. The counter CPI remains stable during the rest of the charging sequence. In the following phase PH4, an equivalent charging current ICR of value 13 causes the counter to be incremented according to a value dependent on the corrective component. The increment is more attenuated than for the IDC1 current. The CP2 counter stabilizes at the maximum limit during the rest of the sequence. During the last phase PH4, because the counter is below the limit, it is possible to command a charging current of a value greater than 13, which makes it possible to increase the energy capacity in regenerative braking and thus improve the autonomy of a vehicle.

[0086] The embodiments described above implement counters for controlling the charging currents. However, it is envisaged that these embodiments also apply to controlling the discharging currents by implementing specific counters. The control unit may therefore comprise one or two or more counters according to one of the embodiments described in FIGS. 5 to 8 and which are calculated simultaneously for the current control function.

[0087] In [Fig. 10], the current control method according to the invention is shown. The current control method is implemented by the control unit of the energy storage system as described in detail in [Fig.l]. This method applies during the driving phase of an electrified vehicle when it is moving at non-zero speed. In this type of situation, the vehicle is not connected to a charging station and the charging currents controlled by the method according to the invention are currents generated by the electric motor of the vehicle during regenerative braking. It should be noted that the control method applies to the control of a charging or discharging current to control the current protection of the current-limiting electrode, which may be the positive or negative electrode of a storage element.

[0088] In a first step 91, the control unit is started and initialized. The value of the counter is initialized to the value of the first limit LimH of the variation range. Alternatively, the counter is initialized to 0 Ah if a relaxation period prior to start-up is detected.

[0089] The method comprises a second step 92 of measuring or estimating the electrical parameters P of the storage element of the battery, the parameters comprising at least the temperature T and the state of charge SOC of each storage element of the battery, the no-load voltage, an aging state parameter SOH of the cells, the exchanged current I(t) in particular. The measurement is carried out periodically during operation of the battery.

[0090] Then, the method comprises a third step 93 of determining the first maximum current IDC1 delivered by the first direct current table 151 taking as input said measured electrical parameters and determining the second current IDC2 delivered by the second direct current table 152. IDC1 is associated with a maximum application duration of 10 seconds for example. IDC2 is applicable for durations greater than 180 seconds without exceeding lithium saturation.

[0091] Then, the method further comprises a fourth step 94 of determining the maximum limit LimH. The maximum limit is calculated according to the table selected from the recorded tables where each table is associated with a specific current application duration. The selection criterion is the chosen current duration. In this example, LimH is the limit associated with the current IDC1 for a duration of 10 seconds. LimH is expressed in Amperes.h.

[0092] Then, the method further comprises a fifth step 95 of calculating the variable counter CP in a variation range delimited by the maximum limit LimH. The calculation of the counter CP comprises the determination of the corrective component of an integrator of the instantaneous current ICR, of charge or discharge, configured so as to control the incrementation and the decrementation of the counter CP according to the value of the instantaneous current ICR with respect to at least the first current IDC1. According to this method, several variants of calculation of the counter are conceivable. In a first variant, the calculation 95 of the counter CP comprises a step of comparing the instantaneous current ICR with respect to the equilibrium current IEQ, and when the instantaneous current is less than the equilibrium current, the corrective component is configured so as to decrement the counter.In case of decrement of the counter, the counter is calculated according to a first correction dependent on the difference between the instantaneous load current ICR and the equilibrium current IEQ. The functional implementation has been described in [Fig.8].

[0093] For the incrementation, when the instantaneous charging current ICR is greater than the second direct current IDC2 or the equilibrium current IEQ, three embodiments can be provided, the functional implementations of which have been described in [Fig.5], [Fig.6] and [Fig.7],

[0094] More precisely, in a first embodiment illustrated by [Fig.5], the calculation 95 of the counter comprises the comparison of the instantaneous load current ICR with respect to predetermined current ranges between the first current IDC1 and the second current IDC2, and the selection of a second predetermined correction from among the corrections F1, F2, F3 and F4 as a function of the result of the comparison for the calculation of the incrementation INC.

[0095] In a second embodiment illustrated by [Fig.6], the calculation 95 of the counter comprises a step of determining a first ratio R defined by the ratio between the instantaneous charging current ICR and the first maximum charging current IDC1, where R=ICR / IDC1 and the determination of a third correction RCOR delivered by a correction table taking as input the first ratio R to calculate the corrective component RCOR of the incrementation INC.

[0096] Finally, in a third embodiment illustrated by [Fig.7], the calculation 95 of the counter includes a step of comparing the instantaneous charging current ICR by in relation to predetermined current ranges between the first current and the second current, here between IDC4, IDC3 and IDC1 for which maximum limits have been calculated respectively, and the calculation of a fourth correction corresponding to a second ratio defined by the ratio between the instantaneous load current and a selected maximum limit, Liml80, Lim30 or Liml0 depending on the result of the comparison. This variant embodiment aims to relate the variation range of the meter to a ratio between 0 and 1 and determine an increment specific to each current range predetermined by the direct current tables.

[0097] In [Fig. 11], an electrified vehicle 100 having a battery system 103 according to the invention is schematically shown. The vehicle may be a hybrid or fully electric vehicle. The vehicle 100 has an electric prime mover 101 for moving the vehicle and powered by the battery system 103. Some or all of the functions of the vehicle 100 are controlled by a control unit 102. The control unit 102 may include at least one processor that executes instructions stored in a computer-readable medium such as non-volatile memory. The control unit 102 may also be multiple computing devices that control individual components or subsystems of the vehicle 100 in a distributed manner. The processor may be any conventional processor, such as a commercially available central processing unit.Alternatively, the processor may be a dedicated device such as an application-specific integrated circuit (ASIC) or other hardware processor.

[0098] The prime mover 101 and the battery system 103 can be controlled in regenerative braking operation. The battery system comprises a control unit 104 comprising a computer and memories configured for implementing the current control method according to the invention. In particular, the memories have a recorded program comprising instructions which, when the program is executed by the control unit of the battery system, cause the latter to implement any one of the embodiments of the control method according to the invention. Furthermore, the control unit 104 is connected in communication with computers of the vehicle by means of an on-board communication bus 108, for example of the CAN (Control Area Network) type, to deliver the current control information determined from the method according to the invention.The control unit 104 informs the powertrain, for example, of a maximum permissible current determined according to the meter. The maximum permissible current is, for example, the charge current that can be controlled in regenerative braking or a discharge current for supplying the electric machine. The current value is a direct current that is associated with a maximum permissible fixed duration. The vehicle further comprises a voltage converter 105 of the DC / DC or AC / DC type. The . vehicle further comprises an electrical relay or switch 106 provided for selectively disconnecting and connecting the battery system 103 from the vehicle's electrical systems and, possibly, from a charging box 107. The charging box is an interface allowing the connection of a charging cable to an external energy source connected to an extended electrical supply network operating at alternating voltage.

[0099] The invention is described in the above by way of example. It is understood that the person skilled in the art is able to produce different variant embodiments of the invention by associating, for example, the different characteristics above taken alone or in combination, without departing from the scope of the invention.

Claims

Claims

1. Method for controlling the maximum current of a battery system (1) comprising an energy storage element (10) comprising at least one electrochemical cell (11), the method being implemented by a control unit (13) of said battery system (1), the method comprising the following steps: - the measurement (92) of electrical parameters (P) of the storage element, - the determination (93) of a first current (IDC1) delivered by a first direct current table (151) taking as input said measured electrical parameters (P), the method being characterized in that it further comprises the following steps: - determining (94) a maximum limit (LimH) corresponding to the quantity of electricity exchanged with the storage element by applying the value of the first current (IDC1) for a first duration (Dl), - the calculation (95) of a variable counter (CP) in a variation range delimited by the maximum limit (LimH), the calculation of the counter (CP) comprising the determination of a corrective component of an integrator of the instantaneous current (ICR) configured so as to control the incrementation and decrementation of the counter (CP) as a function of the value of the instantaneous current (ICR) with respect to at least the first current (IDC1), - the control (96) of the current of the storage element (10) comprising the supply of information (CCI) of maximum current applicable to the storage element (10), when the counter is less than the maximum limit (LimH) said information (CCI) being the first current (IDC1) and, when the counter (CP) is equal to the maximum limit (LimH), said information (CCI) is a second direct current (IDC2) delivered by a second direct current table (152) taking as input said measured electrical parameters (P).

2. Method according to claim 1 in which the calculation (95) of the counter (CP) comprises: - the determination of an equilibrium current (IEQ) as a function of the value of the meter (CP) and the second current (IDC2) according to the following relation: IEQ = CP / LimH * IDC2, CP being the instantaneous value of the meter, LimH the maximum limit and IDC2 being the second current, - the comparison of the instantaneous current (ICR) with the equilibrium current (IEQ), - when the instantaneous current (ICR) is lower than the equilibrium current (IEQ), the corrective component is configured to decrement the counter (CP).

3. Method according to claim 2 in which the corrective component is configured so as to decrement the counter (CP) according to a first correction dependent on the difference between the instantaneous current (ICR) and the equilibrium current (IEQ).

4. Method according to any one of claims 1 to 3 in which the corrective component is configured so as to increment the counter (CP) when the instantaneous current (ICR) is greater than the second direct current (IDC2).

5. Method according to claim 4 in which the calculation (95) of the meter comprises: - the comparison of the instantaneous current (ICR) with respect to at least two predetermined current ranges between the first current (IDC1) and the second current (IDC2), - and the selection of a second predetermined correction (F1; F2; F3; F4) according to the result of the comparison to calculate the corrective component.

6. Method according to claim 4 in which the calculation (95) of the meter comprises: - the determination of a first ratio (R) defined by the ratio between the instantaneous current (ICR) and the first current (IDC1), - the determination of a third correction (RCOR) delivered by a correction table taking as input the first ratio (R) to calculate the corrective component.

7. Method according to claim 4 in which the calculation (95) of the counter (CP) comprises: - the comparison of the instantaneous current (ICR) with respect to at least two predetermined current ranges between the first current (IDC1) and the second current (IDC2), - the calculation of a fourth correction corresponding to a second ratio defined by the ratio between the instantaneous current (ICR) and a selected maximum limit (Liml0, Lim30, Liml80) as a function of the result of the comparison to calculate the corrective component.

8. Method according to any one of claims 1 to 7 in which the steps of calculating (95) the counter (CP) and controlling (96) the current are controlled during a regenerative braking phase or an acceleration phase of an electrified vehicle.

9. Battery system (1) comprising an energy storage element (10) comprising at least one electrochemical cell (11) and a control unit (13) configured specifically for implementing the current control method according to any one of claims 1 to 8.

10. An electrified vehicle (100) comprising a battery system (103) according to claim 9.

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