Electrical energy storage device, motor vehicle and associated process

Abstract

The invention relates to an electrical energy storage system (1) comprising a housing (5) and electrical energy storage cells connected between two electrical terminals. According to the invention, the housing comprises a sealed reservoir (12) having an opening (13) through which the reservoir is adapted to be filled with an electrically conductive liquid, and two electrical conductors (26) which are electrically connected respectively to the two electrical terminals and which each have a portion disposed within said reservoir, at a distance from each other. Figure for the abstract: Fig. 1

Description

Title of the invention: Electrical energy storage device, motor vehicle and associated method Technical field of the invention

[0001] The present invention relates generally to the electrical discharge of electrical storage devices.

[0002] It relates more particularly to an electrical energy storage system equipped with a means for discharging electrical energy.

[0003] The invention finds a particularly advantageous application in electrical energy storage systems equipping motor vehicles.

[0004] It also relates to a motor vehicle comprising such an electrical energy storage system and a method associated with the electrical energy storage system. State of the art

[0005] Electric or hybrid motor vehicles are generally equipped with a battery pack comprising a casing housing electrochemical cells connected together in order to provide a high voltage at the battery terminals, which can reach several hundred volts in order to power the motor vehicle.

[0006] These high voltage values ​​at the battery terminals then represent a danger, particularly when the motor vehicle is involved in an accident, or during the battery dismantling cycle.

[0007] This danger is multifaceted, involving, on the one hand, a risk of thermal runaway, and, on the other hand, an electrical risk for an operator working on the battery. Special precautions are therefore necessary to ensure the safest possible handling and / or storage of accumulator batteries from motor vehicles.

[0008] Thus, operators who handle accumulator batteries must obtain electrical authorization, and they are advised to use specific personal protective equipment.

[0009] Similarly, in order to reduce the risk of thermal runaway, a solution adopted in the prior art consists of immersing the battery in a salt water bath, particularly during its processing at a dismantling center. Such a bath effectively discharges the battery cells. However, this procedure is logistically demanding, time-consuming, and still presents uncontrolled risks.

[0010] These risk limitation measures therefore remain restrictive, and sometimes difficult to implement in certain situations, for example, at an accident site, in order to quickly discharge the electric battery. Presentation of the invention

[0011] In order to remedy the aforementioned drawbacks of the prior art, the present invention proposes an electrical energy storage system adapted to receive an electrically conductive liquid in order to be able to easily discharge electrical energy which is accumulated therein, the liquid, once in contact with the electrical terminals of the system, acting as a bleeding resistance.

[0012] More particularly, the invention proposes an electrical energy storage system comprising a case and electrical energy storage cells connected between two electrical terminals, the case housing a sealed reservoir which is provided with an opening through which the reservoir is adapted to be filled with an electrically conductive liquid, and two electrical conductors which are electrically connected respectively to the two electrical terminals and which each have a part disposed within the reservoir, at a distance from the part of the other of the two electrical terminals.

[0013] Thus, thanks to the invention, rapid and in-situ management of electrical energy accumulated on energy storage systems is made possible, allowing its danger to be limited.

[0014] Indeed, bringing the two electrical terminals into contact by means of a liquid with controlled resistivity makes it possible to safely and certainly empty the electrical energy stored in the storage cells in a controlled time.

[0015] In addition, the use of a liquid as the equivalent of a bleeding resistance has the advantage of better heat dissipation, particularly through the use of a reservoir.

[0016] The fact that the reservoir is integrated within the energy storage system allows for simplified intervention, whether at an accident site or during the dismantling process. Furthermore, the advantageous use of space within the casing allows the invention to be implemented without wasting space, which is often a desirable feature for automotive manufacturers.

[0017] Other advantageous and non-limiting features of the electrical energy storage system according to the invention, taken individually or in all technically possible combinations, are as follows: - The housing includes a waterproof optical system through which the inside of the tank can be observed, - the casing comprises a wall, one area of ​​which is more elastically deformable compared to the remaining part of the wall, the mouthpiece being located at the level of this area, - the casing has a double wall which internally delimits an internal volume which is in fluidic communication with the inside of the tank (which means that the liquid can circulate between the internal volume and the tank), - the housing includes an evacuation outlet, located at a distance from the mouth, the evacuation outlet is in fluidic communication with the mouth.

[0018] The invention also proposes a motor vehicle comprising at least one electrical energy storage system according to the invention, in which the inlet is in fluidic communication with an external surface of the motor vehicle, the external surface being located at a distance from the electrical energy storage system and being preferably accessible from outside the vehicle.

[0019] The invention also relates to a method of electrical discharge of an electrical energy storage system, the electrical energy storage system comprising a casing, electrical energy storage cells connected between two electrical terminals, the casing comprising a sealed tank provided with an opening through which the tank is adapted to be filled with an electrically conductive liquid, and two electrical conductors which are electrically connected respectively to the two electrical terminals and which each have a portion disposed within the tank, at a distance from each other, the method comprising the following step: - injection of an electrically conductive liquid into the tank via the opening, so that the portion of each of the two electrical conductors is at least partially immersed in the electrically conductive liquid.

[0020] Other advantageous and non-limiting features of the process according to the invention, taken individually or in all technically possible combinations, are as follows: - The casing includes a sealed optical system through which the inside of the tank can be observed; the injected electrically conductive liquid contains an electrochromic compound. - the injection step is carried out using a tool which allows the electrically conductive liquid to be simultaneously injected and collected through the mouth, - the housing includes an evacuation outlet located at a distance from the mouth, the evacuation outlet being in fluidic communication with the mouth, the injection step includes at least a partial emptying of the reservoir through the evacuation outlet to put the electrically conductive liquid into circulation between the mouth and the evacuation outlet.

[0021] Of course, the various features, variants, and embodiments of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive. Detailed description of the invention

[0022] The following description with regard to the attached drawings, given by way of non-limiting examples, will make it clear what the invention consists of and how it can be carried out.

[0023] On the attached drawings:

[0024] [Fig-1] is a schematic perspective view of a cross-section of a system of electrical energy storage according to the invention, comprising an opening leading to a reservoir;

[0025] [Fig.2] is a schematic perspective view of a cross-section of the mouth and reservoir of [Fig.1] and of a stopper adapted to close the mouth;

[0026] [Fig.3] is a schematic cross-sectional view of the electrical energy storage system of [Fig.1], where a nozzle of a tank filling means is connected with the mouthpiece;

[0027] [Fig.4] is a cross-sectional view of the mouth of a variant embodiment of the electrical energy storage system according to the invention;

[0028] [Fig.5] Schematic cross-sectional view of a second embodiment of the electrical energy storage system according to the invention.

[0029] Figure [1] illustrates a first embodiment of an electrical energy storage system 1 integrated for example into an electric or hybrid motor vehicle, in order, in particular, to power an electric traction system equipping this vehicle.

[0030] Here, the electrical energy storage system 1 refers to a battery pack (more simply called a battery or battery bank, from the English expression). This battery pack comprises a casing 2 which houses several electrochemical cells, or accumulators. These electrochemical cells are assembled and electrically connected to each other, and are adapted to store electrical energy and deliver it between two electrical terminals (a first electrical output terminal and a second electrical output terminal) in the form of a required voltage. In the case of a motor vehicle, the voltage between the electrical output terminals can be equal to several tens of volts or more (up to several hundred volts), in particular 60 V, or 400 V, or 800 V, or even more, depending on the vehicle. These voltage values ​​are thus well beyond the electrical danger threshold, set at 50 V.Beyond this threshold value, an operator in contact with both electrical terminals is exposed to an electrical risk.

[0031] Here, the cells are distributed in the housing 2 by modules. By way of non-limiting example, the electrical energy storage system 1 comprises eight, ten or twelve modules, grouped into a block of modules 5. These modules are electrically connected to each other in order to provide a voltage equal to 800 V in the context of this first embodiment.

[0032] The electrical energy storage system 1 also includes a mechatronic connection unit 3 housed in the casing 2, one of whose functions is to regulate or even cut off the flow of electrical current between the system's output terminals. This mechatronic connection unit 3 and the module block 5 are connected in series between these output terminals via two electrical conductors 4.

[0033] For example, these two electrical conductors 4 comprise two busbars, according to Anglo-Saxon terminology, of appropriate cross-section, made of a current-conducting material, for example, a metal such as copper, or aluminum.

[0034] The housing 2, also sometimes called the battery casing, comprises six rectangular walls assembled to present a parallelepiped shape.

[0035] In the first embodiment, it is assumed that the electrical energy storage system 1 supplies power to an electric motor of an electric or hybrid motor vehicle, for example, a car. Therefore, this housing is, for example, located on the floor of the vehicle, close to the ground when the vehicle is in an operating position. When arranged in this way, the housing 2 comprises a lower wall 6 near the ground, and an upper wall 7 located opposite the lower wall 6. These two walls are connected by side walls, comprising a front wall 8, a rear wall 9 (not shown in [Fig. 1]), a left wall 10, and a right wall (not shown here).

[0036] It is considered, in order to facilitate the rest of the description, that the casing 2 of the electrical energy storage system 1, is oriented on the [Fig.1] in its operating orientation.

[0037] The housing 2 occupies a relatively large area of ​​the vehicle floor area, due to space required for the modules of the electrical energy storage system 1.

[0038] The housing 2 extends over a length, for example, of between one meter and three meters, measured between the front wall 8 and the rear wall 9 of the housing 2. The housing 2 also extends over a width, for example, of between half a meter and one and a half meters, measured between the left wall 10 and the right wall of the housing 2. A height of the housing 2, measured between the upper wall and the lower wall, is estimated to be on the order of a few tens of centimeters, for example twenty centimeters.

[0039] This casing 2 is, for example, made of aluminum in order to limit the overall weight of the electrical energy storage system 1. However, to increase mechanical rigidity and also to protect the contents of the casing 2, the lower wall 6 of the casing 2 is made of extruded aluminum. The lower wall 6 thus forms a double bottom comprising two plates separated by an internal space 11.

[0040] The walls of the housing 2 are joined together, for example by welding. It is considered in particular that these welds are such that the lower space 11 is sealed against fluids, in particular against an electrically conductive liquid as described below.

[0041] In this first embodiment, the module block 5 and the mechatronic connection unit 3 rest on an internal surface of the lower wall.

[0042] It may happen that electrochemical cells are charged and that it is desired to discharge them easily and safely, for example after an accident.

[0043] For this purpose, the electrical energy storage system 1 includes a reservoir 12 adapted to receive a liquid. This reservoir 12 is located within the housing and is preferably sealed.

[0044] This reservoir 12, represented by a cross-sectional view in [Fig.2], has a wall of arbitrary shape which delimits a volume for the liquid, in particular the electrically conductive liquid described below.

[0045] Here, it comprises a lower cylindrical portion (which delimits a main chamber 23), with a tubular side wall of revolution closed on the top and bottom by circular walls. The upper circular wall has an opening bordered on the top by a tubular collar 16.

[0046] The lower part forms a main chamber 23 with a diameter between 10 centimeters and 30 centimeters, for example equal to 15 centimeters, and a height between 5 centimeters and 15 centimeters, for example equal to 10 centimeters.

[0047] Preferably, the reservoir 12 is made in one piece. For example, the reservoir 12 is made of a plastic material, or, as here, of aluminum, or of any other material that is both electrically insulating and thermally conductive.

[0048] The reservoir 12 has at least one opening 13 which opens here onto the upper wall 6 of the housing 2, for its filling.

[0049] Preferably, it has in its lower circular wall a lower opening through which it communicates with the lower space 11 delimited by the double bottom.

[0050] The mouth 13, corresponding to a portion of the reservoir 12 emerging in relief above the upper wall 7 of the housing 2, is here formed by the upper end of the collar 16.

[0051] This collar 16 has a diameter between a few centimeters and a few tens of centimeters, for example, between 5 centimeters and 10 centimeters, for example 7 centimeters.

[0052] Here, the mouth 13 emerges above an area 18 of the upper wall of the housing 2. This area 18 is located inset with respect to the remaining part 17 of the upper wall 7 of the housing 2.

[0053] This zone 18, which forms a recess in relation to the remaining part 17 of the upper wall 7 of the housing 2, is made of a material that is more elastically deformable than this remaining part 17.

[0054] For example, this remaining part 17 can be made of aluminum sheet or by metal extrusion, while the area 18 is made of rubber or plastic, or any other material capable of protecting the mouth 13 in case of impact.

[0055] While the remaining portion 17 is flat, this area 18 is frustoconical in shape (with the truncated apex pointing downwards), the mouth 13 being located at the center of area 18, i.e., at the apex of the truncated cone. Advantageously, the depth of this recess is such that the mouth 13 does not protrude from the upper wall 7 of the housing 2. In other words, the mouth 13 is also recessed from the external surface of the upper wall 7 of the housing 2, thus protecting it.

[0056] Furthermore, zone 18 is set back from the side walls of the housing 2 to increase its resistance to violent impacts, for example, during an accident. This, in addition to the fact that zone 18 is made of a deformable material, prevents the reservoir tube 12 from rupturing in the event of an impact.

[0057] In one embodiment, this inlet 13 is fluidly connected to a hatch located at a distance from the electrical energy storage system 1, for example, by a hose. This hatch is advantageously positioned for easy access. Easy access means that the hatch can be accessed without tools and / or without requiring force from an operator. For example, this hatch is located in the vehicle's passenger compartment or in the vehicle's body. It includes, for example, an opening that leads to the hose and a cap for closing this opening.

[0058] On the contrary, in the first embodiment, the opening 13 is left free. As shown in [Fig. 2], it is then hermetically sealed by a removable stopper 19. Thus, once the stopper 19 is in place, an internal volume defined by the reservoir 12 and the double bottom is hermetically sealed.

[0059] This plug 19 can, for example, be screwed or clipped onto the collar 16 of the mouthpiece 13.

[0060] In the first embodiment shown in [Fig. 1], the housing 2 includes a sealed optical system 20 through which the internal volume of the reservoir 12 can be observed. In other words, the inside of the reservoir 12 is observable thanks to the optical system 20. In particular, in the first embodiment, the sealed optical system 20 is arranged on the cap 19.

[0061] Thus, the optical system 20 comprises a first optical lens 21 positioned at one apex of the cap 19 (near the outer surface of the upper wall 7 when the cap 19 is closed), while a second optical lens 22 is held at a distance from the first lens 21, the two lenses 21 and 22 sharing a common optical axis. The cap 19 has an opening for this purpose, which accommodates the first lens 21. The opening is bordered on its lower side by a tube, the end of which holds the second lens 22.

[0062] The second lens 22 is arranged within the reservoir 12 (in its lower part). For this reason, the tube has a diameter smaller than that of the collar 16.

[0063] This optical system 20 allows visualization of the interior of the reservoir 12, for example, from the upper wall of the housing, as detailed below. It thus allows visualization of whether the main chamber 23 of the reservoir 12 is filled or not, in particular whether the electrically conductive liquid used to fill it is colored.

[0064] According to one possible variant, the cap 19 does not include an optical system 20.

[0065] The housing 2 of the electrical energy storage system 1 preferably has an exhaust outlet 24. This is located, for example, on the upper wall 7. However, it is possible, according to variants, to place this exhaust outlet 24 elsewhere, for example on the lower wall 6.

[0066] This evacuation outlet 24 is in fluidic communication with the lower space 11, here via a cannula 25, placed at a distance from the reservoir 12.

[0067] Like the mouth 13, the evacuation outlet 24 can be placed in a recess relative to the remaining part 17 of the upper wall 7.

[0068] This discharge outlet 24 can, for example, serve as an outlet for the liquid when it is desired to circulate the liquid during battery discharge. This circulation of the liquid advantageously improves the cooling of the electrical energy storage system 1.

[0069] The reservoir 12 as described is adapted to be filled with an electrically conductive liquid, for the purpose of discharging the battery.

[0070] To this end, two electrical conductors 26 connected to two electrical terminals are to be placed in the reservoir 12. These two electrical conductors 26 are located a distance apart. In this way, the electrically conductive liquid will form an electrical resistance between these electrical terminals, so that the electrochemical cells of electrical energy storage system 1 can discharge.

[0071] The two aforementioned electrical terminals will, for example, be those of the electric battery. However, alternatively, they could be those of a module (in which case a reservoir 12 will be provided in each module) or, more broadly, electrical terminals between which any number of electrochemical cells will be connected.

[0072] Thus, a first part 261 of a first electrical conductor 26, for example a first end of a first busbar, is disposed in the main chamber 23 of the tank 12. A second part 262 of the first electrical conductor 26, for example a second end of the first busbar, is electrically connected to one of the electrical terminals of the module block 5. For example, in the first embodiment, and as shown in [Fig.2], the second end is fixed on one of the electrical conductors 4 of the aforementioned module block 5.

[0073] The first electrical conductor 26 is therefore inserted through an opening made in the main chamber 23, in a manner sealed against the electrically conductive liquid.

[0074] A first part 261 of a second electrical conductor 26, for example a first end of a second busbar, is disposed in the main chamber 23 of the tank 12. The first two parts 261 of the two electrical conductors 26 are disposed at a distance from each other.

[0075] For example, a distance of between 10 millimeters and 15 millimeters separates the first two parts of the two electrical conductors 26, for a nominal voltage of the storage system equal to 800 V. In the case where the nominal voltage is equal to 400 V, the distance between the first two parts of the two electrical conductors 26 is, for example, greater than or equal to 8 millimeters and less than or equal to 15 millimeters.

[0076] A second part 262 of the second electrical conductor 26, for example a second end of a second busbar, is electrically connected to another of the electrical terminals of the module block 5. For example, the second end is fixed to one of the electrical conductors 4 of the module block 5.

[0077] The second electrical conductor 26 is inserted through another opening into the main chamber 23. This other opening is located at a distance from the first opening, and is also made in the main chamber 23 in a manner sealed against the electrically conductive liquid.

[0078] Thus, when the reservoir 12 is empty, due to the distance separating them, the first two parts 261 of the two electrical conductors 26 respectively connected Electrically, the two electrical terminals of the module block 5 are electrically isolated from each other. Indeed, the air acts as an insulator.

[0079] The reservoir 12 thus described is adapted to be filled with an electrically conductive liquid, in order to implement the process detailed below.

[0080] This process allows the electrical discharge of the electrical energy storage system 1. In other words, this process allows an electrical charge accumulated in the system to be emptied.

[0081] The process consists of injecting an electrically conductive liquid into the reservoir 12, in order to electrically contact the first two parts 261 of the two electrical conductors 26 placed in the main chamber 23.

[0082] This process includes at least one step of injecting an electrically conductive liquid into the reservoir 12 via the mouth 13. This injection step allows the first parts 261 of the electrical conductors 26 arranged within the main chamber 23 of the reservoir 12 to be immersed.

[0083] During the dissipation of electrical energy, the liquid experiences a temperature increase due to the Joule effect. However, heat, i.e., thermal energy emitted during the discharge of electrical energy, is advantageously dissipated due to the large transfer surface area represented by the lower space 11 connected to the reservoir 12. The large contact area of ​​the liquid with the lower wall 7 promotes heat transfer and thus allows for faster heat dissipation.

[0084] The liquid injected into the reservoir 12 is described as electrically conductive, and has, for example, ions suitable for conducting electric current. Electrically conductive means, in particular, a liquid having an electrical conductivity at 25°C, for example, greater than 1.25 S / m (siemens per meter) for an 80 kWh battery at 800 volts, and, for example, greater than 5 S / m for an 800 kWh battery at 400 volts.

[0085] This liquid also exhibits a resistivity, equal to the inverse of its electrical conductivity, the value of which is controlled, in order to allow a gradual discharge over a desired period of time of the electrical energy stored within the electrical energy storage system. Thus, the liquid acts as a bleeding resistor.

[0086] In practice, a resistance per unit measurement of the liquid is 80 ohms / cm, with, for example, a distance of 10 millimeters between the electrical conductors. Thus, in the area considered (i.e., between the electrical conductors), the resistance will be on the order of 80 ohms / cm for an 80 kWh battery at 800 volts. In the case of an 80 kWh battery at 400 volts, a liquid with a resistance of per unit of measurement is 20 Ohms / cm, to have a resistance of 20 Ohms in the area.

[0087] For example, the electrically conductive liquid used here corresponds to an aqueous solution of salt, for example sodium chloride with the chemical formula NaCl. A salt concentration in the aqueous solution is controlled, and depends in particular on a nominal voltage across the system terminals, as well as the time duration after which a discharge of electrical energy is desired.

[0088] In the first embodiment, where the nominal voltage of the storage system is 800 V, the distance between the electrical conductors 26 is 10 millimeters, and the desired discharge time is, for example, ten hours, the salt concentration of the liquid is chosen to be equal to a mass fraction expressed as a percentage of 0.88 wt% of sodium chloride (NaCl). In this example, it is assumed that the battery capacity is 100 Ah, with a discharge rate of 0.1 C.

[0089] Alternatively, in the case of a battery voltage of 400 V, with a distance between the electrical conductors 26 of 10 millimeters and a desired discharge time of ten hours, a salt concentration of the liquid is chosen to be equal to a mass fraction expressed as a percentage of 3.5 wt% of Sodium Chloride (NaCl). Here, the battery capacity is 200 Ah, and the operating rate is 0.1 C.

[0090] Thus, in a simplistic embodiment, the process consists of injecting an adequate volume of liquid into the reservoir 12 via the mouth 13, closing it with the plug 19, and then waiting for the electrical discharge of the electrical energy storage system 1. In this embodiment, the discharge outlet 24 can serve as a vent or is superfluous.

[0091] This embodiment of the process can be applied, for example, at an accident site, in order to secure an electrical energy storage system 1 that has suffered a violent shock.

[0092] Preferably, a liquid comprising an electrochromic compound can be used, that is, a chemical compound adapted to change color when subjected to an electric current. For example, it could be a viologenic compound (of the 4,4'-bipyridyl or 4,4'-bypyridine type) and / or polyaniline (PANI).

[0093] The process then includes an additional step consisting of observing the color of the electrically conductive liquid through the sealed optical system 20. This step makes it possible to assess, based on the color of the liquid, whether or not the accumulated electrical energy has indeed been dissipated. Alternatively, this control of the remaining electrical energy in the energy storage system is verified by measuring the voltage using, for example, a voltmeter.

[0094] In another embodiment, in order to improve the evacuation of the heat emitted within the liquid during the discharge of electrical energy, the liquid is put into circulation, through the reservoir 12, for example between the mouth 13 and the discharge outlet 24.

[0095] For this purpose, the step of injecting the liquid into the reservoir 12 through the mouth 13 is carried out simultaneously with an extraction of liquid out of the reservoir 12 through the discharge outlet 24.

[0096] This embodiment is particularly suitable for the case where the process is implemented within a dismantling plant for electrical energy storage systems 1, as part of the management of the end of life of electric batteries.

[0097] A first example of injecting the liquid into the reservoir 12 and the lower space 11 is shown in [Fig.3].

[0098] In this example, a nozzle of a liquid dispensing gun is connected to the mouthpiece 13, so as to inject the electrically conductive liquid through an inlet pipe 27. Rather than a defined volume of liquid, in this example, a continuous flow is injected through the mouthpiece 13, so as to fill the main chamber 23 of the reservoir 12, and the lower space 11. In particular, the liquid is injected with sufficient pressure so that when the internal volume defined by the reservoir 12 and the lower space 11 is filled with liquid, the liquid flows out through the drain outlet 24. A drain pipe 28 is connected to this drain outlet 24, in order to collect the liquid flowing out of the housing 2 of the electrical energy storage system 1.

[0099] This liquid evacuated from the housing 2 is for example to be cooled remotely from the housing 2, before being reinjected into the same housing 2 through its mouth 13.

[0100] In one embodiment, it is possible to connect several housings 2 of electrical energy storage systems 1 in series, i.e., to connect the inlet 13 of a first electrical energy storage system 1 to the inlet, before connecting the discharge outlet 24 of the first electrical energy storage system 1 to the inlet 13 of a second electrical energy storage system 1, whose discharge outlet 24 is connected to the inlet 13 of a third electrical energy storage system 1, and so on. Thus, a volume of liquid circulates from housing to housing, the liquid being optionally cooled between each electrical energy storage system 1.

[0101] A second example of injecting the liquid into the reservoir 12 and the lower space 11 is shown in [Fig.4].

[0102] In this embodiment, the electrical energy storage system 1 does not include a drain outlet 24. The nozzle of the dispensing gun is modified and has two parallel hoses. This nozzle is connected to the first mouthpiece 13. A first pipe of the mouthpiece serves as an inlet pipe 27, through which the liquid is injected, while a second pipe of the mouthpiece serves as an outlet pipe 28 through which the liquid exits the housing 2, as described previously.

[0103] Figure 5 represents a second electrical energy storage system 1, exhibiting some of the characteristics of the electrical energy storage system 1 presented previously. This second electrical energy storage system 1 corresponds to a module, comprising several cells.

[0104] This module comprises a parallelepiped-shaped housing 29. This housing 29 contains electrochemical cells electrically connected to each other in order to generate an electrical voltage between two electrical terminals. These electrical terminals are connected to electrical conductors 30, for example, busbars. Note that these electrical terminals of the electrochemical cells also correspond here to the electrical terminals of the module.

[0105] Such a module delivers, for example, a voltage of several tens of volts, for example 60 V.

[0106] When the module is in use, these two electrical terminals are in electrical connection with other elements, not shown here.

[0107] This housing 29 is adapted to accommodate a reservoir 31 by means of a rim, positioned opposite the electrical conductors 30. In other words, the electrical conductors 30 are cantilevered from the rim. Thus, the parallelepiped-shaped reservoir 31, slightly smaller than the housing, fits within a space defined by the electrical conductors 30 and the rim.

[0108] This reservoir 31 includes an opening 32 located on an upper wall of the housing 29, this opening 32 being closed by a plug 33.

[0109] Here, two electrical conductors 34 are provided, placed within the reservoir 31, at a distance from each other. A part, for example, the upper end of each electrical conductor 34, is in electrical contact with one of the two electrical terminals of the module.

[0110] Thus, like the system described above, this module is adapted to be filled with an electrically conductive liquid, so as to at least partially immerse the two electrical conductors 34 within the reservoir 31. This electrically conductive liquid then acts as a bleeding resistor, dissipating stored electrical energy. Due to the relatively low voltage of such an electrical energy storage system 1, the liquid heats up only slightly during the dissipation of electrical energy. A relatively small internal volume is therefore sufficient for this type of application.

[0111] The present invention is in no way limited to the embodiments described and represented, but a person skilled in the art will be able to make any variation in accordance with the invention.

[0112] For example, the shape and / or volume of the main chamber 23 and / or the lower space 11 can be modified from that described above in order to optimize the circulation of the liquid within the casing between the first inlet 13 and the discharge outlet 24. This can optimize the injection and discharge flow rate of the reservoir 12, thus avoiding any risk of overheating. As detailed previously, the injection of the electrically conductive liquid can be carried out directly via the inlet located on the casing, or via an auxiliary inlet located remotely and more easily accessible to an operator. It is also possible to monitor the state of charge of the electrical energy storage system by measuring the temperature during the implementation of the process.

Claims

Demands

1. Electrical energy storage system (1) comprising a housing (2), electrical energy storage cells connected between two electrical terminals, characterized in that said housing (2) contains: - a sealed reservoir (12) which is provided with an opening (13) through which the reservoir (12) is adapted to be filled with an electrically conductive liquid, and - two electrical conductors (26) which are electrically connected respectively to the two electrical terminals and which each have a portion (261) disposed within said reservoir (12), said two portions (261) being located at a distance from each other.

2. Electrical energy storage system (1) according to claim 1, wherein said housing comprises a sealed optical system (20) through which the interior of the tank (12) is observable.

3. Electrical energy storage system (1) according to any one of claims 1 to 2, wherein the housing (2) comprises a wall of which a zone (18) is more elastically deformable compared to a remaining part (17) of the wall, said mouth (13) being disposed at said zone (18).

4. Electrical energy storage system (1) according to any one of claims 1 to 3, wherein said casing (2) has a double wall which internally delimits an internal volume which is in fluidic communication with the interior of said tank (12).

5. Electrical energy storage system (1) according to any one of claims 1 to 4, wherein said housing (2) includes an evacuation outlet (24) disposed at a distance from the mouth (13), said evacuation outlet (24) being in fluidic communication with said mouth (13).

6. Motor vehicle comprising at least one electrical energy storage system (1) according to any one of claims 1 to 5, wherein said mouth (13) is in fluidic communication with an external surface of said motor vehicle, said external surface being located at a distance from said electrical energy storage system (1) and preferably being accessible from outside the vehicle.

7. Method for electrically discharging an electrical energy storage system (1), said system comprising a casing (2), electrical energy storage cells connected between two electrical terminals, said casing (2) housing a sealed reservoir (12) having an opening (13) through which the reservoir (12) is adapted to be filled with an electrically conductive liquid and two electrical conductors (26) which are electrically connected respectively to the two electrical terminals and which each have a portion disposed within said reservoir (12), at a distance from each other, said method comprising the following step: - injecting an electrically conductive liquid into said reservoir (12) via said opening (13), such that said portion of each of the two electrical conductors (26) is at least partially immersed in said electrically conductive liquid.

8. Electrical discharge method according to claim 7, wherein said housing (2) comprises a sealed optical system (20) through which the interior of said reservoir (12) is observable, said injected electrically conductive liquid comprises an electrochromic compound.

9. Electrical discharge method according to any one of claims 7 or 8, wherein said injection step is carried out using a tool enabling simultaneous injection and collection of said electrically conductive liquid through said mouthpiece (13).

10. Electrical discharge method applied to a system according to claim 5, in said injection step includes at least partial emptying of said reservoir (12) through said discharge outlet (24) to put said electrically conductive liquid into circulation between the mouth (13) and the discharge outlet (24).