BATTERY PRESSURE APPLICATION SYSTEM

Abstract

The invention relates to a system for applying pressure to an electric battery, which comprises a pack (11, 12) of several battery cells arranged against each other along a longitudinal axis (X) between a movable downstream end plate (15, 16) and an upstream end plate (13, 14).The application system comprises: i) two ball screws (20, 21) on either side of the pack, each ball screw being free to rotate about an upstream support (22, 23) fixed to the upstream end plate (13, 14) and a downstream nut (24, 25) fixed to the downstream end plate (15, 16), ii) a pressure measuring device (17, 18) for the pressure exerted on the battery cells, iii) an electric motorization device (26, 27) capable of rotating the two ball screws (20, 21) so as to vary the pressure applied to the battery cells by the end plates (13, 14, 15, 16), iv) an electronic control module (29) connected to the pressure measuring device (17, 18) and responsible for controlling the rotation of the motorization device (26, 27). (Fig. 1).

Description

Title of the invention: BATTERY PRESSURE APPLICATION SYSTEM Technical field of the invention

[0001] The invention relates generally to the technical field of electric batteries, in particular lithium-ion (or Li-ion) type batteries which are notably used to supply energy to the powertrains of hybrid or electric motor vehicles.

[0002] The invention relates more specifically to a system for managing the pressurization and maintenance of such batteries during the different phases of their life cycle. Prior art

[0003] Li-ion type batteries for motor vehicles are usually composed of one or more rows, each having a plurality of battery cells held against each other between two end plates. These end plates exert a pressure force on the battery cells.

[0004] Indeed, it is known that charging a Li-ion battery significantly increases the volume of the cells composing that battery, and conversely, discharging the battery decreases the volume of the cells. These volume variations during successive charge / discharge cycles cause significant mechanical stress on the battery, potentially leading to premature aging. It is therefore important to be able to control these volume variations as effectively as possible by applying appropriate pressure to the battery cells at all times, typically by applying higher pressure to the battery cells when they are charging and releasing this pressure during the discharge phase.

[0005] Document DE102009035482A1 already describes a Li-ion type battery comprising several cells fixed between two end plates, thus forming a cell stack. A pressure force is applied to this cell stack by means of a simple passive actuator, such as a spring, or an active actuator, such as a servomotor or linear motor, which acts on the end plates.

[0006] For improved reliability, the application system must operate continuously, even during a power outage. Therefore, it is important to find a simple solution to ensure that the pressure exerted on the battery cells continues to be applied even in the event of energy loss, in order to prevent a pressure drop that could be harmful to the battery.

[0007] Furthermore, a significant number of parameters constantly influence the pressure strategy to be applied and therefore the calculation of the optimal pressure to be applied to the battery. These parameters include various electrical measurements such as voltage, current, and resistivity at the battery cell terminals, as well as measurements related to the battery's environment, such as ambient temperature or the temperature of the body and electrical connections of the battery. However, the parameters to be considered may also include data specific to each battery, such as its current state (in production in a vehicle or in after-sales maintenance), its age, the number of charge / discharge cycles already performed, etc. It would therefore be advantageous to take these various parameters into account to develop the best strategy to adopt in real time. Description of the invention

[0008] For this purpose the invention describes a system for applying pressure to an electric battery, which comprises a pack of several battery cells arranged against each other along a longitudinal axis between a downstream end plate and an upstream end plate.The pressure application system comprises: two longitudinal ball screws positioned on either side of the pack, each ball screw being free to rotate around an upstream support and a downstream nut, the upstream support being fixed to the upstream end plate and the downstream nut being fixed to the downstream end plate, a device for measuring the pressure exerted on the battery cells, an electric motorization device capable of rotating the two ball screws so as to vary the pressure applied to the battery cells by the end plates, an electronic control module connected to the pressure measurement device and responsible for controlling the rotation of the motorization device.

[0009] According to one feature, the pressure application system also includes a battery management system communicating with the control module, the management system comprising a processing unit and a storage unit, the storage unit storing in real time representative data of the battery and its environment which are transmitted by the control module.

[0010] According to another feature, the representative data of the battery and its environment include measurements of electrical quantities, temperature measurements, pressure measurements, and parameters specific to the battery. The battery management system's processing unit determines one or more pressure setpoints to be applied to the battery and transmitted to the control module, based on the representative data of the battery and its environment.

[0011] According to another feature, the pressure application system comprises two rows arranged side-by-side transversely, each row comprising a The battery cell plurality and pressure measurement device includes a pressure sensor for each row of cells. The pressure sensors are placed between the upstream end plates and the cells.

[0012] According to another feature, the drive device comprises two electric motors, each motor being kinematically coupled to a ball screw. Alternatively, the drive device comprises one electric motor kinematically coupled to both ball screws.

[0013] According to another feature, in the absence of power supply to the pressure application system, the two ball screws remain stationary, thus maintaining the pressure exerted on the battery cells. Brief description of the figures

[0014] Other features and advantages of the invention will become apparent from the following description, with reference to the attached figure which illustrates: • [Fig.1]: a simplified perspective diagram of a pressure application system according to the invention. detailed description of an implementation method

[0015] According to the invention, a pressure application system is intended to manage and regulate the pressure applied to a lithium-ion battery. This battery consists of a pack comprising N rows of battery cells, N being one, two, or more. In the embodiment shown in [Fig. 1], the pressure application system 10 manages a battery comprising a pack of two rows 11, 1, 2, each row having fifteen battery cells. These cells are parallelepiped in shape and are arranged side by side along a longitudinal axis X. Within the pack, the two rows 11, 1, 2 are placed next to each other in a transverse direction perpendicular to the axis X.

[0016] The cells of the first row 11 are sandwiched between a first end plate 13 called upstream, and a first end plate 15 called downstream. Similarly, the cells of the second row 12 are sandwiched between a second upstream end plate 14 and a second downstream end plate 16.

[0017] The upstream end plates 13, 14 may or may not be mechanically fixed to each other, and the downstream end plates 15, 16 may or may not be mechanically fixed to each other. If they are not fixed, this would require two ball screws per row (one ball screw on each side of the row) but would nevertheless provide better precision in managing the pressure applied to each row. To exert a pressure force on the cells, the downstream end plates 15, 16 (or the upstream end plates 13, 14) are movable in translation along the X axis under the action of a rotational movement of an actuator (see below).

[0018] The pressure application system includes a device for measuring the pressure exerted on the battery cells. In the example of [Fig. 1], the pressure measuring device consists of a force sensor or pressure sensor 17, 18 for each row 11, 12. The sensors 17, 18 are installed between an end plate and the cells, for example between the upstream plate 13, 14 and the cells, so as to measure in real time the pressure exerted by the end plates on the battery cells. The sensors 17, 18 can also be installed between two adjacent cells. These pressure sensors 17, 18 are, for example, piezoelectric sensors.

[0019] To exert pressure on the cells, the pressure application system 10 includes an actuator comprising two longitudinal ball screws 20, 21 which are positioned on either side of the battery pack. Each ball screw 20, respectively 21, is free to rotate about a fixed upstream support 22, respectively 23, and a movable downstream nut 24, respectively 25. The upstream support 22 of the first ball screw 20 is fixed to the first upstream end plate 13 and the downstream nut 24 of the first screw 20 is fixed to the first downstream end plate 15. Similarly, the upstream support 23 of the second ball screw 21 is fixed to the second upstream end plate 14 and the downstream nut 25 of the second screw 21 is fixed to the second downstream end plate 16.

[0020] Thus, a simple rotation of the ball screw 20, respectively 21, in one direction or another, causes a corresponding translation of the downstream nut 24, respectively 25, which leads to the longitudinal displacement of the downstream end plate 15, respectively 16, and therefore a variation in the pressure force exerted on the battery cells of the rows 11, respectively 12.

[0021] To drive the ball screws 20, 21 in rotation, the application system 10 preferably comprises an electric motor coupled to the ball screws 20, 21. A manual drive or a drive based on any type of energy (for example, pneumatic) could also be considered. In the embodiment presented, the motor comprises two separate electric motors 26, 27. The first motor 26 is mechanically coupled to the first ball screw 20, and the second motor 27 is mechanically coupled to the second ball screw 21. The details of these mechanical couplings are conventional and are not detailed in [Fig. 1].

[0022] Having a separate motor for each ball screw allows, if necessary, for a different pressure force to be applied to each row of cells, for example in the event that the expansion in one row of cells is greater than in the other. But it could also be envisaged that the device The motorization system consists of a single electric motor driving both ball screws 20 and 21. This motor would then be mechanically coupled to the two screws. In this case, the pressure exerted by screws 20 and 21 would necessarily be the same for both rows of cells 11 and 12. This solution would also be well-suited for a pack containing only one row of cells.

[0023] According to a preferred embodiment, the two motors 26, 27 are DC motors, for example of the brushless type, because they have to perform small movements with high precision.

[0024] Thanks to this solution, when the ball screws stop rotating, the end plates remain stationary, and the force exerted on the battery cells advantageously remains constant without needing to maintain any control signal on the motor(s). Thus, in the absence of power to the application system 10 or the drive device 26, 27 (for example, following an unexpected power outage), the ball screws 20, 21 are not driven to rotate and remain stationary. The pressure exerted on the cells then remains identical and does not undergo any variation, which provides a safer solution for the battery.

[0025] Moreover, since the actuator comprises only ball screws placed laterally and driven by an electric motor, the invention provides a simple, space-saving and easily accessible solution for installing the cell rows in the application system and for removing them during after-sales operations.

[0026] The application system 10 includes a local electronic control module 29. This control module 29 receives real-time information signals from various sensors and sends a control command to the motorization device 26, 27.Among the sensors connected to the control module 29 are: i) the pressure sensors 17, 18 mentioned previously for each row of cells, ii) one or more temperature sensors to measure the ambient temperature near the battery as well as the body temperature and the temperature of certain electrical connections within the battery cells, iii) position sensors for the downstream end plates 15, 16 and ball screw displacement sensors 20, 21 (of the incremental or absolute encoder type, for example), and iv) voltage, current, and resistivity sensors at the terminals of the battery cells or any type of sensor capable of recording other data representative of the cells. The connections between these various sensors and the control module 29 are generally wired but can also be wireless.

[0027] The application system 10 also includes a central battery management system (BMS: Battery Management System), not shown in the figures. The The battery management system comprises a data processing unit and a data storage unit. This battery management system communicates with the control module 29, which regularly sends all sensor data to the battery management system. Furthermore, the battery management system can also collect battery-specific information related to the vehicle in which the battery is installed (battery status, number of charge / discharge cycles already completed, current cycle, operating or maintenance phase, etc.).

[0028] Advantageously, all information received by the battery management system is stored in the data storage unit, so as to create and continuously update for each battery a personalized database containing data representative of the battery throughout its life cycle and representative of the vehicle in which it is installed.

[0029] This customized database is then used by the processing unit to develop various algorithms for controlling the pressure applied to the battery cells. Advantageously, these control algorithms are differentiated according to, for example, the desired battery performance, the age and condition of the battery, and the current operating mode (during operation in a vehicle or during maintenance and after-sales service). After analyzing the dataset and determining the appropriate algorithm to use, the battery management system is then able to transmit one or more pressure commands to the local control module 29. These commands may, for example, be in the form of a pressure profile or diagram to be applied over time.Next, the control module 29 controls and regulates the rotation of the motorization device 26, 27 in real time according to this or these instructions.

[0030] According to a first embodiment, the battery management system is positioned near the battery pack, for example on a battery socket 19, and can communicate with the local control module 29 via a wired connection using, for example, a standard OBD (On-Board Diagnostic) connection. According to another embodiment, the battery management system is positioned elsewhere in the vehicle and can then communicate with the local control module 29 via a wireless connection, for example, Bluetooth.

[0031] Naturally, the invention is described above by way of example. It is understood that a person skilled in the art is able to carry out different embodiments of the invention without departing from the scope of the invention.

[0032] It is emphasized that all features, as they are apparent to a person skilled in the art from the present description, drawings and attached claims, even if in practice they have only been described in relation to other specific features, both individually and in combinations any, may be combined with other features or groups of features disclosed herein, provided that this has not been expressly excluded or that technical circumstances make such combinations impossible or meaningless.

Claims

Demands

1. A system for applying pressure to an electric battery, comprising a pack (11, 12) of several battery cells arranged side by side along a longitudinal axis (X) between a movable downstream end plate (15, 16) and an upstream end plate (13, 14), characterized in that the pressure application system (10) comprises: - two longitudinal ball screws (20, 21) positioned on either side of the pack, each ball screw being rotatable about an upstream support (22, 23) and a downstream nut (24, 25), the upstream support (22, 23) being fixed to the upstream end plate (13, 14) and the downstream nut (24, 25) being fixed to the downstream end plate (15, 16), - a device for measuring the pressure exerted on the battery cells, - an electric motorization device (26, 27) capable of rotating the two ball screws (20,21) so as to vary the pressure applied to the battery cells by the end plates (13, 14, 15, 16), - an electronic control module (29) connected to the pressure measuring device (17, 18) and responsible for controlling the rotation of the motorization device (26, 27).

2. Pressure application system according to claim 1, characterized in that it also comprises a battery management system communicating with the control module (29), the management system comprising a processing unit and a storage unit, the storage unit storing in real time representative data of the battery and its environment which are transmitted by the control module (29).

3. Pressure application system according to claim 2, characterized in that the data representative of the battery and its environment include measurements of electrical quantities, temperature measurements, pressure measurements and parameters specific to the battery.

4. A pressure application system according to claim 3, characterized in that, based on representative data of the battery and its environment, the processing unit of the battery management system determines one or more pressure setpoints to be applied to the battery and transmitted to the control module (29).

5. Pressure application system according to claim 1, characterized in that it comprises two rows (11, 12) arranged side-by-side transversely, each row comprising a plurality of battery cells and the pressure measuring device comprises a pressure sensor (17, 18) for each row of cells.

6. Pressure application system according to claim 5, characterized in that the pressure sensors (17, 18) are placed between the upstream end plates (13, 14) and the cells.

7. Pressure application system according to claim 5, characterized in that the drive device comprises two electric motors (26, 27), each motor being kinematically coupled to a ball screw (20, 21).

8. Pressure application system according to claim 1, characterized in that the drive device comprises an electric motor (26) kinematically coupled to the two ball screws (20, 21).

9. Pressure application system according to claim 1, characterized in that, in the absence of power supply to the pressure application system, the two ball screws (20, 21) remain stationary, thus maintaining the pressure exerted on the battery cells.