WO2023031528A1

WO2023031528A1 - Battery system having a means for measuring an internal pressure in order to manage a charge setpoint

Info

Publication number: WO2023031528A1
Application number: PCT/FR2022/051387
Authority: WO
Inventors: Arnaud Beniere; Bao Kou XIONG; Victor CLOUZET; Jean Parenteau
Original assignee: Psa Automobiles Sa
Priority date: 2021-09-02
Filing date: 2022-07-11
Publication date: 2023-03-09
Also published as: FR3126356A1; CN117940311A

Abstract

The present invention relates to a battery system (1) comprising electrical power storage elements (9), a control means (2) capable of calculating a charge setpoint (CRL) and a means (5) for enclosing the elements (9), which battery system further comprises a means for measuring (4) a parameter representative of a measured pressure which is exerted by the surface elements (9) of the enclosure means (5) and wherein the control means (2) provides a limited charge setpoint (CRL) according to the parameter. The invention also relates to a method for controlling the charge by managing a charge setpoint according to the parameter representative of the measured pressure. The invention is for use, for example, in electric vehicles having a traction battery.

Description

DESCRIPTION

TITLE: BATTERY SYSTEM COMPRISING A MEANS OF

INTERNAL PRESSURE MEASUREMENT TO CONTROL A

RECHARGE INSTRUCTION

The present invention claims the priority of French application No. 2109170 filed on 02.09.2021, the content of which (text, drawings and claims) is incorporated herein by reference.

The field of the invention relates to a battery system and a method for controlling the charging of said system. The invention applies in particular to an electrified vehicle and aims to optimize the service life of a battery.

Electrified vehicles are equipped with a high-power traction battery generally comprising several electrochemical cells, for example of the Lithium-ion type. For this type of technology, a cell comprises a wall and internal elements comprising a positive electrode, a separator and a negative electrode. For the proper functioning of a cell, these elements must be kept in contact within a range of positive force. In operation, the chemical reactions generate gases and an expansion of the electrodes, then producing a pressure pushing the walls.

This pressure increases as a cell ages. This is the pressure resulting from the increase in the passivation layer in proportion to the state of aging. Furthermore, it has been found that the pressure fluctuates significantly during variations in the level of the state of charge in charge and unloading. This results in a force resulting from the expansion of active materials in proportion to the instantaneous state of charge level. This last phenomenon is called breathing or “Breathing” according to the English term.

The increase in pressure resulting from both aging and both cell respiration tends to decrease the pressure between electrodes and separators. To prevent their separation, it is common to enclose a cell or a set of cells in a rigid frame to keep the internal elements in contact.

As a cell is used, the increase in internal pressure affects the aging of the cell and therefore determines the end of life. For electromobility applications, the end of life is generally set at a loss of energy storage capacity of around 20%. With regard to the mechanical deformations observed between cells and the ends of the rigid frame, values of the order of 25 k.N of tensile force were measured on the sides of the frame for a state of aging of 20% and values of 5 k.N for new condition.

Battery system frames are sized for a maximum level of pressure and for a given aging state, linked to an acceptable loss of energy capacity for the intended application. When the force applied to the surface of the cells by the internal elements reaches the expected limit, the use of the battery is terminated to avoid the risk of fire due to a rupture of the cells or a module.

To this end, car manufacturers are developing algorithms for estimating the state of aging of batteries to define the end-of-life period. A known method consists of counting the number of charge and discharge cycles and deciding to replace the battery when a limit is reached. However, the constraint assumptions used are not always realistic because the level of aging mainly depends on the actual use of the battery. It happens in some cases that the use of the battery could be extended without risk of malfunction.

On the other hand, the lifetime of the battery systems could be increased in return for larger, heavier batteries and a reinforced frame as well as a greater reduction in the total capacity. However, these solutions are not recommended in the field of electromobility.

It is also known to implement methods for controlling the temperature and for limiting the charging current, in particular for fast charging. For example, document FR2952235A1 is known describing a charging process in which the voltage measured at the terminals of the battery is compared with a voltage threshold in order to control the end of charging and in which the threshold is provided by a table which is a function of the measured temperature and the current flowing in the battery. The use of this table aims to prevent physical damage to the battery and improve its longevity. Other strategies recommended by certain manufacturers aim to reduce the target state of charge level at the end of recharging, set for example at 80% of the maximum total capacity available, to reduce the stresses on the cells caused by a state of charge pupil.

The invention aims to overcome the aforementioned problems. An object of the invention is to extend the life of a battery. Another objective is to adapt the management of the charging of a battery according to the aging of the electrochemical cells. Another objective is to improve the estimation of the level of aging of a battery and adapt the energy management in accordance with its use.

More specifically, the invention relates to a battery system comprising electrical energy storage elements, a control means able to calculate a charging instruction and a metal frame to enclose all the elements. According to the invention, the system further comprises means for measuring a parameter representative of a measured pressure which is exerted by the surface elements of said metal frame and the control means delivers a limited recharging setpoint as a function of said parameter .

According to a variant, the measuring means comprises at least one strain gauge delivering a measurement of the elongation of the metal frame.

According to a variant, the measuring means comprises at least one strain gauge delivering a measurement of the elongation of the metal frame or a measurement of the elongation of the wall of an electrical energy storage element.

According to a variant, the measuring means comprises at least one pressure sensor fixed between the energy storage elements and the metal frame.

According to a variant of the system in which the energy storage elements are electrochemical cells, the measuring means comprises at least one pressure sensor fixed between two electrochemical cells at the surface of one of said two cells.

There is provided according to the invention an electrified vehicle comprising a battery system according to any one of the preceding embodiments. According to the invention, a charging control method is provided for such a battery system comprising the following steps:

The determination of a parameter representative of a measured pressure which is exerted by the electrical energy storage elements on the surface of said metal frame,

The control of a first charging setpoint limited according to said parameter.

According to a variant, the control of the first limited charging setpoint consists in determining a charging limitation coefficient as a function of the parameter with respect to a charging limitation threshold, the value of the first limited charging setpoint being a function of a second recharging setpoint multiplied by the limitation coefficient.

According to a variant, when the value of the parameter is greater than or equal to the limitation threshold, the limitation coefficient is equal to a first value controlling the stopping of the recharging of the battery system.

According to a variant, when the value of the parameter is lower than the limitation threshold, the limitation coefficient is equal to a second value which is a function of a difference between the value of the parameter and the limitation threshold.

According to a variant, the first charging setpoint is a maximum authorized charging current setpoint, the first value of the coefficient is equal to 0, and the second value is a value strictly greater than 0, between 0 and 1, for example 0 .5, 0.75, 0.90 or 1 .

According to a variant, the first charging setpoint is a maximum authorized state of charge level, when the value of the parameter is greater than or equal to the limitation threshold, the maximum authorized state of charge level is strictly lower than the level of charge available, for example is equal to 90% of the maximum level of charge available, or else 80%, 70%, 60%, 50%, 40%, 30%, 20%, or 10% of the maximum level of charge available.

The invention improves the management of the electric recharge in that it is controlled in a manner adapted to the aging of the battery thanks to the monitoring of the expansion of the electrochemical cells. Thanks to the invention, it is possible to extend the duration life of a battery, by accepting a limited maximum state of charge level and controlled specifically according to the process. The invention makes it possible to monitor the increase in the dilation of the cells and to control the stopping of the recharge in the event of a risk of rupture of the cells.

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

[Fig.1] schematically represents a battery system according to the invention.

[Fig .2] represents a functional diagram describing the recharging control means provided for controlling the recharging control method according to the invention.

[Fig.3] is a graph schematically illustrating the evolution of the aging level of a battery and the recharging control according to the invention as a function of the pressure exerted by the electrical energy storage elements of the battery.

[Fig.4a] schematically represents an alternative embodiment of the battery system comprising a pressure sensor.

[Fig .4b] schematically represents another alternative embodiment of the battery system comprising a pressure sensor.

The invention applies to the field of electrochemical batteries, in particular in the field of electrified vehicles, but not exclusively. The battery system and the associated method find an application in the field of charging control management applications in stationary applications, electromobility and any electronic device with a battery system. By way of non-limiting example, the preferred mode of the invention will be described for an electrified motor vehicle application comprising a high-power traction battery. In the present description, the term approximately means +/-10% of the indicated value and the limits of a range of values are included in the range.

The object of the invention is to stop recharging and/or gradually reduce recharging as a function of a parameter representative of an internal pressure of the battery. The invention has the effect of gradually reducing the maximum authorized state of charge level as a function of the aging of the battery. In Figure 1, there is schematically described a preferred embodiment of the battery system according to the invention for an electrified vehicle. The battery system 1 comprises a module 3 comprising electrical energy storage elements 9 comprising a plurality of electrochemical cells, in this non-limiting example of Lithium-ion type technology. An electrochemical cell comprises a wall and internal elements comprising a positive electrode, a separator and a negative electrode. The internal elements of a cell must be held in contact within a positive force range. The wall of a cell can be cylindrical, prismatic or be in the form of a film (technology known as “Pouch Cell”). The battery system 1 further comprises a means 2 for controlling recharging. The control means 2 is provided for at least developing a charging instruction for the energy storage elements 9 in accordance with the method according to the invention.

The battery system 1 is electrically rechargeable by means of electric lines 8 connected to a charging control device 6 of the electrified vehicle. The charging control device 6 is electrically connected to an electrical charging source 7. The electrical source 7 can be an electricity-generating machine, for example the electric traction machine of the vehicle, or a charging terminal external to the vehicle. For example, the charging control device 6 comprises charging means cooperating with an electrical outlet so as to be able to be electrically connected to the external charging terminal 7 connected to an electrical power supply network, generally operating in alternating voltage. Terminal 7 can deliver direct or alternating current. High voltage contactors are generally provided which ensure the disconnection/connection of the battery 1 with the electrical power circuit of the vehicle, the charging control device 6 and the electrical outlet.

The battery system 1 further comprises means 5 for enclosing the electrochemical cells 9. In this embodiment, the means 5 for enclosing is a metal frame. This metal frame is for example external to the electrochemical cells, made of aluminum type material for example. This frame is then sufficiently rigid to exert a positive pressure against the surface of the walls of the cells 9, this rigid frame 5 surrounding or surrounding a group of several electrochemical cells 9 as can be seen in FIG. 1 so as to exert this positive pressure against the surface of walls of the cells 9. The frame 5 is arranged to apply pressure to only part of the wall of the cells, for example on each side of the cells laterally. It is not excluded that the frame 5 can frame or completely enclose the electrochemical cells, for example in the form of a box. The pressure exerted by the frame 5 is then applied in the latter case to the side faces and the upper and lower faces of a cell.

The frame 5 is commonly designated by the English terms “casing”, “side plate” or “end plate”, or the terms strapping, box, belt. It frames the module 3 of a group of cells 9. In another embodiment, it is envisaged that each cell of a battery can be enclosed by a frame 5. In another embodiment, the means for enclosing 5 forms the outer wall of an electrochemical cell. The pressure applied by the clamping means 5 is provided to keep the electrodes in contact against the separator inside each cell.

In the case of a non-limiting example, of a prismatic cell of dimensions 28mmx7mmx14mm, at the start of its life, the force applied by the frame 5 on the surface of a cell is 5k. N. For a state of aging at the end of life specified for example for a motor vehicle, the force applied by the frame 5 varies between 20k. N and 25k. N, with fluctuations of the order of 5k. N resulting from cell respiration.

The state of aging can be designated by the acronym SOHc for "State of Health on capacity" and corresponds to the aging level parameter of the battery expressed by a ratio between the maximum quantity of electricity that can be stored at a given moment and the quantity maximum storable electricity in new battery condition.

The state of charge level can be designated by the acronym SOC for "State of Charge" and corresponds to the state of charge level of the battery expressed by a ratio between the quantity of energy stored at a given instant and the maximum amount of energy that can be stored at a given time. The SOHc and SOC parameters are expressed in percentages.

The forces applied which have been measured during the life of a cell or during testing make it possible to establish a recharge limitation threshold aimed at stopping expansion of an electrochemical cell resulting from an increase in the state dump.

The battery system 1 further comprises a means 4 for measuring a pressure. The measuring means 4 has the function of measuring a parameter representative of a pressure which is exerted by the electrical energy storage elements 9 of the battery 1 on the surface of the frame 5. In this preferred embodiment of the invention, the measuring means 4 is a strain gauge arranged to measure an elongation of the frame rigid 5 or the elongation of an electrochemical cell 9 of the battery 1. The strain gauge is fixed to the surface of the frame 5 or to the surface of the wall of a cell. The strain gauge 4 delivers a voltage signal to the control means 2, the value of which is proportional to the elongation of the frame 5.

Any other means of measurement is possible without departing from the scope of the invention. The measuring means can be a pressure sensor or a piezoelectric technology sensor for example. Such a sensor is fixed between an electrochemical cell 9 and the frame 5, or alternatively between two electrochemical cells 9.

The monitoring of this parameter allows the control means 2 to develop a recharging setpoint CRL according to the invention, for example an end of recharging command when this parameter exceeds a chosen threshold. Additionally or as an alternative variant, the control means 2 is configured to generate a command to reduce the charging current gradually as a function of said parameter.

The control means 2 is intended for the supervision of the battery system 1 . It is capable of delivering battery status information to other vehicle computers, such as a value representative of the SOC, the SOHc, the temperature, the charging current flowing through the battery or the no-load voltage in particular , as well as instructions intended for the charging control device 6 and/or a charging terminal 7, in particular an authorized charging power, a charging mode, a maximum charging current, or a charging limitation setpoint. fluent. A communication bus is provided, for example of the CAN (Control Area Network) type, allowing the control means 2 to communicate the charging instructions to other computers.

The charging control device 6 has the function of managing the communication between the various charging terminals and of monitoring and controlling the electrical charging at the terminal. The recharging device 6 also comprises an electrical converter of the alternating/direct AC/DC and direct/direct DC/DC type. In terminal charging situations, it performs the conversion of an alternating voltage to an AC/DC direct voltage, in particular when charging in mode 2 or mode 3 in which it is necessary to convert an alternating voltage in 220V (single-phase or three-phase type) to a compatible DC voltage of the battery system, up to 450V or 1000V for example in this embodiment. When driving, another function is the DC/DC conversion between the battery and the vehicle's on-board systems, for example the 14V on-board network, the low voltage battery and the electric traction machine of the powertrain.

In the context of so-called fast or mode 4 charging, the charging voltage is delivered directly by terminal 7, i.e. without modification of the voltage by the voltage converter. The voltage delivered by terminal 7 is of the DC type, generally greater than 300V, in this example between 400V and 500V, and is directly applied to the terminals of battery 1 through the high voltage contactors. For this type of charge, the charging device 6 delivers to terminal 7 the charging setpoint CRL calculated by the control means 2 of the battery system 1 .

The control means 2 is provided with an integrated circuit computer and electronic memories, the computer and the memories being configured to execute a recharging control method according to the invention. But this is not mandatory. Indeed, the computer could be external to the control means 2, while being coupled to the latter. In the latter case, it can itself be arranged in the form of a dedicated computer comprising a possible dedicated program, for example. Consequently, the control means 2, according to the invention, can be produced in the form of software (or computer (or even “software”)) modules, or else of electronic circuits (or “hardware”), or even of a combination of electronic circuits and software modules.

In FIG. 2, the functional module of the control means 2 of the battery system 1 provided to allow the charging control method according to the invention to be implemented has been described. In this embodiment, it conventionally comprises a first module 20 configured to calculate a charging instruction CR.

In this preferred embodiment, the recharge setpoint is a maximum authorized recharge current setpoint. The current setpoint CR is determined as a function of the current state of charge SOC, of the state of aging SOH, of the temperature in particular. The current setpoint CR is delivered for example by a predetermined map, established in design and recorded in the memory of the control unit 2 of the battery system 1, taking as input the current state of charge SOC and the temperature of the battery 1 .

More precisely, the control means 2 receives as input a measured value of the temperature of the battery from one or more temperature sensors, as well as a measured value of the total voltage of the battery 1 . In a manner known per se, the total voltage of the battery 1 can be determined from information measured at the level of the electrochemical cells 9. The current flowing through the battery is determined from current sensors of the battery 1 . In addition, the control means 2 is able to determine the SOC state of charge level of the battery 1 at any time, for example expressed as a % of the total capacity of the battery, from equivalence tables with the measured voltage and an indicator of state of health or state of aging SOH. The table(s) are stored in the memory of the control means 2 and can be consulted at any time by its computer.

The recharging control method according to the invention comprises a step of determining a parameter P representative of a measured pressure which is exerted by the internal elements of the battery on the surface of said means for clamping and a step of controlling the setpoint limited charging CRL as a function of said parameter P. The charging setpoint CRL is a maximum accepted current setpoint.

More precisely, to determine the recharge setpoint CRL, dependent on the internal pressure of the battery in accordance with the invention, the strain gauge 4 delivers an elongation value M of the frame 5 to the computer 2. The value M is proportional to the elongation of the frame 5. The value M is multiplied, illustrated by the multiplier block in FIG. 2, by a coefficient of stiffness K, proportional between the elongation and the force exerted by the internal elements of the battery 1. K is a predetermined coefficient in design and stored in memory. The control means 2 therefore continuously calculates during the use of the battery 1 the value of the parameter P, where P = K*M. P is a parameter whose value is representative of the force exerted by the internal elements of battery 1 on frame 5.

In this preferred embodiment of the method, the control of the limited recharging setpoint CRL consists in determining a recharging limitation coefficient CL as a function of the parameter P with respect to a recharging limitation threshold SL. For this purpose, the control means 2 comprises a second module 21 whose function is to calculate the limitation coefficient CL. The function of the limitation coefficient CL is to limit the recharge setpoint CR and/or to gradually reduce the value of the recharge setpoint CL, until the end of the recharge when the pressure is greater than a predetermined limitation threshold.

In this embodiment, the limitation coefficient CL is multiplied by the value of the current setpoint CR to calculate the limited recharge setpoint CRL, illustrated by the multiplier block in FIG. 2. The limitation coefficient CL takes values in a range delimited by the values 0 and 1 , in a binary or gradual way.

In an embodiment in binary limitation or "all or nothing" type control, the coefficient CL is equal to 1 as long as the value of the parameter P is lower than the pressure limitation threshold SL. The limitation coefficient CL is equal to zero when the value of the parameter P is greater than or equal to the threshold SL. The value 0 therefore controls the stopping of recharging because the maximum authorized current set point is equal to 0 amperes. The threshold SL is calibrated for example at a value of approximately 25k. N. The value of the threshold SL depends on the dimensions and characteristics of the frame 5 and the stress criteria specific to the battery system 1. This value is in no way limiting of the invention.

In an embodiment in gradual limitation control, the coefficient CL is equal to a value between 0 and 1 according to the difference between the value of the parameter P and the value of the threshold SL. The value is equal to 1 when the deviation is greater than 2k. N, i.e. for a pressure P up to 23k. N. The value of CL is equal to 0.5 for a pressure P equal to 24k. N and the value of CL is 0 when P is equal to or greater than 25k. N. Other coefficient values can be envisaged without departing from the scope of the invention.

The limited recharge setpoint CRL is preferably the maximum current setpoint authorized by the battery, that is to say is equal to or less than the setpoint CR. As a variant, the charging setpoint CRL can be a setpoint specifically controlling the stopping of the charging, which can be independent of the setpoint CR used to control the charging of the battery. It does not necessarily express a maximum recharge current. In this case, the setpoint CRL can be any setpoint capable of controlling the end of charging protocol. The CRL setpoint commands the stopping of recharging before reaching the maximum state of charge SOC to avoid degradation of the cells, in particular separation of the electrodes and separators internal to the cells.

In another variant of the method, the charging setpoint is a target maximum state of charge level SOC conditioning the triggering of the stopping of the charging. The method comprises the determination of a maximum SOC charge level authorized for recharging as a function of the value of the parameter P. During recharging, the computer of the battery system continuously monitors the state of charge of the battery and stops charging when the maximum authorized SOC is reached.

For example, a table, saved in the memory of computer 2, comprises values of the maximum battery charge level associated with parameter values P, representative of the pressure or of the elongation measured. Depending on the value P measured, the table delivers the maximum authorized charge level.

In particular, when the parameter P is equal to or greater than the threshold SL, the maximum level of SOC authorized is configured at a value lower than the maximum level of SOC available. This maximum authorized level corresponds to the maximum acceptable pressure with regard to a risk of rupture of the frame or the cells. Thus, according to the method, when the state of charge reaches the maximum authorized level established according to the parameter P, the method controls the stopping of the recharge.

The advantage of this variant is that it also allows the user to be shown a virtual state of charge level, in percentage, based on the authorized load range instead of an available load range. The charge level can thus be reported on a scale of [0%-100%] of the allowed range. This avoids a possible misunderstanding of the limitation function by the user, where the latter would consider the early stopping of the charge as a malfunction of the battery system.

In FIG. 3, a graph is presented illustrating the operation of the invention for controlling battery recharging, in particular for controlling the stopping of recharging when the internal pressure of a battery reaches the predetermined threshold SL .

On the abscissa axis, the evolution of battery aging has been represented as a function of the SOHc parameter, expressed in % by the ratio between the quantity of energy maximum storable at a given moment and maximum quantity of energy storable in the new state of the battery.

On the left ordinate axis, the value of the parameter P which is representative of the internal pressure has been represented. The measured pressure P is between 5k. N, in early battery life situation, and 25k. N, in usual end of battery life situation. The threshold SL, illustrated by the double horizontal line is established in this example at 25k. N. The P _SO co% curve expresses the value of the pressure P measured for a current state of charge of the battery at SOC=0%. The curve P _SO cioo% expresses the value of the pressure P measured for a current state of charge of the battery at SOC=100%. The value of the pressure P measured by the strain gauge varies between these two curves according to the value of the current SOC throughout the life of the battery. This is the breathing phenomenon. Furthermore, it is observed that the average value P increases as the battery ages.

On the right-hand ordinate axis, the value of the maximum state of charge of the battery that can be authorized in accordance with the method according to the invention has been indicated. SOCmax is represented by a double line curve and is between 0% and 100% and corresponds to the authorized battery usage range. The value of SOCmax at the start of life is equal to 100% and remains constant as long as the pressure measured is lower than the threshold SL. The value of SOCmax decreases gradually as a function of the pressure when the pressure P reaches the threshold SL.

There are two life phases of the battery UT1 and UT2. UT1 corresponds to the life phase during which the pressure measured is lower than the threshold SL whatever the value of the SOC. The method according to the invention does not impose any recharging limitation. UT2 corresponds to a phase where the aging SOHc is greater than 20% and corresponds to a life phase where the measured pressure P _SO cioo% can reach the threshold value SL according to the value of the SOC.

For UT2, the control method according to the invention imposes a limitation of the recharging setpoint as soon as the pressure reaches the threshold SL. It can be seen that the value of the pressure P peaks at the value of the threshold SL. This is the consequence of the charging limitation according to the method. In this phase, the maximum rechargeable state of charge value SOCmax becomes lower than the maximum SOC level of the battery, set at SOCmax=100%. The more the pressure increases, the more the SOCmax decreases because the stopping of the recharge is controlled for lower states of charge in accordance with the invention. This makes it possible to prolong the use of a battery in a controlled and optimal manner, in return for a reduction in the SOCmax during the period UT2.

In dotted lines, the value of the pressure Psoc100% has been extended for a SOCmax of 100% and the value of the SOCmax=100%, on the assumption that the recharging control method according to the invention would not be applied. It is observed that by maintaining the maximum authorized SOC at 100% during UT2, the pressure Psoc100% would exceed the threshold SL. This situation is subject to the risk of fire in the cells or rupture of the frame of the cells. Generally, the use of the battery is terminated. The invention avoids this by controlling the end of the refill in accordance with the method to maintain the pressure less than or equal to SL.

Several embodiments of the battery system are now described, differing by the arrangement of the pressure measurement means.

In FIGS. 4a and 4b, a first alternative embodiment of the module 3 of a battery system is described in which the measuring means 4 is a pressure sensor. According to a variant of the first embodiment, as illustrated in FIG. 4a, the sensor 4 is fixed between the frame 5 and an electrochemical cell 9. According to a second variant, as illustrated in FIG. 4b, the sensor 4 is fixed between two electrochemical cells 9.

In a second embodiment, in which the battery system is provided with several modules of electrochemical cells, and in which each module comprises a rigid frame enclosing the group of cells, each module or only a selection of the modules comprises at least one means measurement of parameter P. Each module or the selection of modules can be equipped with a strain gauge and/or a pressure sensor.

In a third embodiment, of so-called "Cell to Pack" technology, the frame forming the pack is equipped with one or more strain gauges and/or one or more pressure sensors between the frame and a cell, and /or between two cells.

In a fourth embodiment, of so-called “Pouch Cell” technology, the pressure measurement means is attached to the surface of the film, or between two cells.

Finally, the battery system can comprise a single electrochemical cell or comprise a plurality of cells.

Claims

1. Battery system (1) comprising elements (9) for storing electrical energy, a control means (2) capable of calculating a charging setpoint (CR, CRL) and a metal frame (5) for enclosing the set of elements (9), characterized in that it further comprises a means (4) for measuring a parameter (P) representative of a measured pressure which is exerted by the elements (9) on the surface of said frame metal (5) and in that the control means (2) delivers a limited recharging instruction (CRL) as a function of said parameter (P).

2. System (1) according to claim 1, characterized in that the measuring means (4) comprises at least one strain gauge delivering a measurement of the elongation (M) of the metal frame (5).

3. System (1) according to claim 1 or 2, characterized in that the measuring means (4) comprises at least a first pressure sensor fixed between the elements (9) and the metal frame (5).

4. System (1) according to any one of claims 1 to 3, wherein the elements (9) are electrochemical cells, characterized in that the measuring means (4) comprises at least one pressure sensor fixed between two electrochemical cells on the surface of one of said two cells.

5. Electrified vehicle comprising a battery system (1) according to any one of claims 1 to 4.

6. Charging control method for a battery system (1) according to any one of claims 1 to 4, characterized in that it comprises the following steps:

- The determination of a parameter (P) representative of a measured pressure which is exerted by the elements (9) for storing electrical energy on the surface of said metal frame (5),

- The control of a first limited recharging setpoint (CRL) according to said parameter (P).

7. Method according to claim 6, characterized in that the control of the first limited recharge setpoint (CRL) consists in determining a coefficient of charging limitation (CL) as a function of the parameter (P) with respect to a charging limitation threshold (SL), the value of the first limited charging set point (CRL) being a function of a second charging set point ( CR) multiplied by the limitation coefficient (R).

8. Method according to claim 7, characterized in that, when the value of the parameter (P) is greater than or equal to the limitation threshold (SL), the limitation coefficient (CL) is equal to a first value controlling the stoppage recharging the battery system (1 ).

9. Method according to claim 7 or 8, characterized in that, when the value of the parameter (P) is lower than the limitation threshold (SL), the limitation coefficient (CL) is equal to a second value which is a function a difference between the value of the parameter (P) and the limit threshold (SL).