Bistable mechanical discharge cell battery

Abstract

An electrical energy storage battery comprising at least one casing (2) and at least one cell (1), as well as: – at least two internal contact terminals (4); – at least one bistable mechanical discharge element (7) comprising at least two electrical contact interfaces (8), and adapted to occupy two stable positions: a deactivated position in which the electrical contact interfaces (8) are separated from the internal contact terminals (4) and a discharge position in which the electrical contact interfaces (8) are each in contact with one internal contact terminal (4); – a resistive discharge circuit (9) connecting the two electrical contact interfaces (8) of the bistable mechanical discharge element (7). Figure for the abstract: Fig. 1

Description

Title of the invention: Bistable mechanical discharge battery. Technical field

[0001] The invention relates to the field of batteries for storing electrical energy by electrochemical means. More particularly, the invention relates to battery discharge methods that enable, in particular, the recycling of these batteries.

[0002] Electrochemical batteries are available in various technologies and are increasingly common, particularly in high-power, widespread applications such as electric vehicle propulsion. Battery recycling is a crucial operation for this essential and growing sector. Discharge methods for electrochemical batteries are necessary to completely discharge them, regardless of their initial state of charge, even if this state is unknown.

[0003] A high-power battery can indeed store a significant amount of energy which can represent a danger to operators of the recycling process, and which in the most critical cases can cause significant damage by fire or explosion.

[0004] Discharge means are essential to guarantee the safety and reliability of operation required before any battery dismantling operation, especially when it is of high power, and particularly in the context of its recycling, in a context where the number of end-of-life batteries will increase very sharply, with ever-increasing stored energy.

[0005] Such means of discharge are also desirable for destructive recycling operations, such as battery shredding and pyrolysis, because they then make it possible to overcome certain constraints on the size, energy involved, and / or processing rate of the batteries that can be treated. PREVIOUS ART

[0006] Discharge methods currently known in the context of the recycling of electrochemical accumulators are generally manual means, adapted to low rates and exhibiting random operational reliability.

[0007] Numerous research efforts are underway to reduce or eliminate the risks associated with battery recycling, but these operations are proving to be very complex due to the reactivity of the objects involved and the versatility of the products reaching the end of their life (diversity of geometries, chemistries, etc.).

[0008] French patent application FR3094841 further describes discharge means that take advantage of the internal electronics of a battery to discharge it before recycling. This system is inexpensive, but it presents an operational risk due to the fact that the discharge means are electrically powered by the battery itself. When the battery provides only low power at the end of discharge, or when the electronics are defective, the implementation of the discharge process is no longer guaranteed, which is a critical drawback for processes that must guarantee the safety required for a recycling application. Description of the invention

[0009] The invention aims to improve the means of discharging electrochemical batteries of the prior art.

[0010] To this end, the invention relates to an electrical energy storage battery, comprising at least one casing and at least one battery cell disposed in this casing, comprising: - at least two internal contact terminals located inside the housing and each connected to a battery cell connection terminal; - at least one bistable mechanical discharge element accessible from outside the housing and positioned opposite two of said internal contact terminals, the bistable mechanical discharge element comprising at least two electrical contact interfaces, and being adapted to occupy two stable positions: a deactivated position in which the electrical contact interfaces are away from the internal contact terminals and a discharge position in which the electrical contact interfaces are each in contact with an internal contact terminal; - a resistive discharge circuit linking the two electrical contact interfaces of the bistable mechanical discharge element.

[0011] According to another object, the invention relates to a method for discharging a battery as described above, comprising the following steps: - to mechanically stress the bistable mechanical discharge element from outside the battery towards its discharge position; - measure a discharge parameter and declare the battery discharged following the attainment of a discharge criterion.

[0012] The invention guarantees the complete and safe discharge of a battery, in particular before dismantling operations for disposal or recycling.

[0013] A battery thus discharged can therefore be disassembled, crushed, or undergo any other suitable recycling process. The invention is particularly advantageous for the recycling of large batteries containing large amounts of energy, operations which are becoming increasingly essential with the widespread adoption of these batteries. batteries, and current and future regulations, including regulations that will eventually require the recycling of batteries produced.

[0014] Indeed, when a battery, for example an electric vehicle battery made of lithium-ion cells, is received at a recycling center, its state of charge is not necessarily known in advance, and its cells may potentially contain a significant amount of energy. The invention enables recycling without needing to know the battery's state of charge, and therefore without having to carry out physicochemical measurements, electrical measurements, or consult the BMS (Battery Management System) devices possibly associated with the battery. All these measurements or consultations can present risks in the case of a defective or end-of-life battery. Recycling operations can begin safely with the certainty of working on a battery that no longer contains any energy.

[0015] To guarantee such discharge of the batteries, the invention only requires simple operations by devices or operators capable of putting the bistable mechanical discharge element into the discharge position.

[0016] The discharge according to the invention acts upstream and independently of the battery BMS and any other electronic safety device which would prevent access to the power stored in the cells, for example due to the presence of relays in a higher level box (encompassing the battery), which would prevent access from the outside to the internal electrical potentials.

[0017] Discharge is achieved simply by dissipating the battery's residual energy as heat. A high level of safety is ensured by sizing the resistive discharge circuit to achieve a slow discharge and limit thermal management issues for the batteries during discharge. Discharge can be carried out passively and in the background, for example during storage prior to recycling, which reduces the cost impact of the discharge step for recyclers.

[0018] Safety is further enhanced by the fact that the invention also allows for the discharge of batteries that can no longer be discharged via their external terminals. This is particularly the case for batteries whose internal cell terminals are no longer connected to the final battery terminals, for example, defective batteries or batteries where a mechanical or electronic safety cut-off device has been activated (most electric vehicle batteries are equipped with such protections).

[0019] The battery according to the invention may include the following additional features, alone or in combination:

[0020] - the bistable mechanical discharge element is disposed on a wall of said housing;

[0021] - said wall has a substantially median plane, the deactivated position and the discharge position of the bistable mechanical discharge element being located on either side of this median plane;

[0022] - the electrical contact interfaces are fixed on an internal face of said wall of the case;

[0023] - the bistable mechanical discharge element is disposed on a cover of the housing;

[0024] - the bistable mechanical discharge element consists of at least one stamped part the case wall;

[0025] - the resistive discharge circuit includes a resistive conductor;

[0026] - the electrical contact interfaces and said resistive conductor are made of a single piece ;

[0027] - the resistive discharge circuit includes a resistive dipole;

[0028] - the resistive discharge circuit is arranged inside the housing;

[0029] - the resistive discharge circuit is located outside the housing;

[0030] - each electrical contact interface comprises a through-element presenting an external electrical contact;

[0031] - the battery further comprises additional discharge means connected in parallel to the resistive discharge circuit;

[0032] - the resistive discharge circuit is fixed against a wall of said housing;

[0033] - the battery comprises an electrically insulating layer disposed between the circuit resistive discharge and said casing wall;

[0034] - the battery comprises a thermally conductive layer disposed between the resistive discharge circuit and said casing wall;

[0035] - the internal contact terminals are constituted by a free portion of a terminal of connection of one of the battery cells;

[0036] - the internal contact terminals are constituted by a free portion of a conductor power connected to battery cells;

[0037] - the resistive discharge circuit is sized to ensure a discharge of the battery conforming to a predetermined discharge time, for the battery initially fully charged;

[0038] - said predetermined discharge time is a minimum of 3 hours, and preferably for a minimum of 12 hours;

[0039] - said predetermined discharge time is a maximum of 168 hours, and preferably for a maximum of 72 hours;

[0040] The discharge method according to the invention may include the following additional features, alone or in combination:

[0041] - the discharge criterion is a predetermined discharge time;

[0042] - the discharge criterion is a predetermined dissipated thermal power;

[0043] - the discharge process includes a diagnostic step in which a The consistency parameter is checked, and if this consistency parameter is not met, the battery is redirected to a predetermined process. PRESENTATION OF THE FIGURES

[0044] Other features and advantages of the invention will become apparent from the following non-limiting description, with reference to the accompanying drawings in which:

[0045] - Fig. 1 is a schematic cross-sectional view of a battery according to a mode of realization of the invention, with its bistable mechanical discharge elements in the deactivated position;

[0046] - [Fig. 2] is a schematic cross-sectional view of a battery according to a mode of realization of the invention, with its bistable mechanical discharge elements in the deactivated position;

[0047] - [Fig. 3] is a perspective view of a portion (in this example, it is of a wall) of the casing of a battery according to an embodiment of the invention;

[0048] - [Fig. 4] is a perspective view of a portion of a battery casing according to an embodiment of the invention;

[0049] - [Fig. 5] is a schematic cross-sectional view of the battery in [Fig. 1] with its bistable mechanical discharge elements in discharge position;

[0050] - [Fig. 6] is a schematic cross-sectional view according to one embodiment of the invention, with its bistable mechanical discharge elements in the deactivated position;

[0051] - [Fig. 7] is a schematic cross-sectional view of the battery in [Fig. 6] with its bistable mechanical discharge elements in discharge position;

[0052] - [Fig. 8] is a schematic cross-sectional view of a battery according to a mode of realization of the invention, with its bistable mechanical discharge elements in the deactivated position;

[0053] - [Fig.9] is a perspective view of a portion (in this example, it is of a wall) of the casing of a battery according to an embodiment of the invention;

[0054] - [Fig. 10] is a schematic cross-sectional view of the battery in [Fig. 8] with its bistable mechanical discharge elements in discharge position;

[0055] - [Fig. 11] is a schematic cross-sectional view of the battery in [Fig. 10] with the resistive discharge circuit in place;

[0056] - [Fig. 12] is a perspective view of a portion of a battery casing according to an embodiment of the invention. DETAILED DESCRIPTION

[0057] The invention relates to an electrical energy storage battery. It is a device for storing electrical energy by means electrochemicals, regardless of their technology. These can include, for example, lead-acid batteries with liquid electrolyte, gel or AGM ("Absorbed Glass Mat"), or technologies based on nickel, lithium, or other chemistries.

[0058] These batteries are generally made up of one or more modules within which battery cells 1 are assembled and connected to each other. The invention applies to any battery that comprises at least one casing 2 and at least one cell 1 arranged in this casing 2, regardless of the battery's composition, with its various modules, cells, etc.

[0059] The housing 2 can be a closed or open housing, an openwork structure, or any other structural element suitable for holding the cells 1, and for bringing a bistable mechanical discharge element 7 into contact with the cell(s) 1.

[0060] The battery has at least two internal contact terminals 4 located inside the casing 2 and each connected to a connection terminal 5 of a battery cell 1. A connection terminal 5 is a point on the cell 1 that is connected to one of its electrical potentials. These internal contact terminals 4 form an accessible electrical contact inside the casing 2 for the discharge means.

[0061] The internal contact terminals 4 can for example be directly constituted by a free portion of a connection terminal 5 of the cell 1, for example by a flat and bare upper portion of the connection terminal 5, as in the example of [Fig.1].

[0062] According to another example, the internal contact terminals 4 can be made up of free portions of power conductors 6, such as busbars, which are themselves connected to the connection terminals 5 of the cells 1, for example the power conductors which connect in series and / or in parallel the different cells 1 arranged in the housing 2. The internal contact terminals 4 can then be made up of flat and stripped upper portions of these power conductors 6, as in the example of [Fig.2].

[0063] The battery includes at least one bistable mechanical discharge element 7 accessible from outside the housing 2, opposite at least one of said internal contact terminals 4.

[0064] The bistable mechanical discharge element 7 can be disposed on a wall of the housing 2, for example on a cover 3 closing the housing 2. The bistable mechanical discharge element 7 is accessible from outside the housing 2 so that it can be mechanically activated.

[0065] The bistable mechanical discharge element 7 comprises at least two electrical contact interfaces 8, arranged opposite the internal contact terminals 4.

[0066] The housing 2 can include as many bistable mechanical discharge elements 7 as necessary depending on the various internal electrical connections to the battery, including its number of cells and their series and / or parallel connections. [Fig.3] illustrates an example of a large number of bistable discharge mechanical elements 7, and [Fig.4] illustrates an example with a single bistable discharge mechanical element 7 (as illustrated in [Fig.4]).

[0067] Each of these bistable mechanical discharge elements 7 is arranged on the housing 2 so that its electrical contact interfaces 8 are arranged opposite the corresponding internal contact terminals 4.

[0068] The bistable mechanical discharge element(s) 7 can be arranged on any face or portion of the battery casing 2, depending on the arrangement of the cells and their connection means, so that the bistable mechanical discharge elements 7 are opposite the corresponding electrical contact interfaces 8.

[0069] In the example of [Fig. 3], the face of the casing shown corresponds to a battery in which each cell 1 has its own bistable mechanical element 7, adapted to discharge each cell 1; and in the example of [Fig. 4], the face of the casing shown corresponds to a battery in which a single bistable mechanical discharge element 7 can act on all the cells 1 because it acts on power conductors 6 to which all the cells 1 are interconnected, directly or indirectly. Any other configuration is possible, with a suitable number of bistable mechanical discharge elements 7 provided for subsets of cells 1 grouped within the casing 2.

[0070] The bistable mechanical discharge elements 7 are adapted to occupy two stable positions: - a deactivated position (that illustrated, for example, in Figures 1, 2, 6, and 8) in which the electrical contact interfaces 8 are separated from the internal contact terminals 4; and - a discharge position (that illustrated for example in figures 5, 7, 10, and 11), in which the electrical contact interfaces 8 each come into contact with an internal contact terminal 4.

[0071] The bistable mechanical discharge elements 7 are only stable in the two positions indicated above. When sufficient force is exerted on a bistable mechanical discharge element 7 to move it out of its deactivated position, for example by mechanical pressure exerted on this element, this element necessarily returns to its discharge position.

[0072] The bistable mechanical discharge elements 7 can be made by any mechanical means having only two stable positions. Particularly advantageously, these bistable mechanical discharge elements 7 can be formed by stampings on the wall of the housing, as for example in Figures 3, 4, and 9. The bistable mechanical discharge elements 7 can also be made by any other mechanical means such as a flexible blade, a toggle device, or any other known bistable mechanical means.

[0073] The bistable mechanical discharge elements 7 are moved from their deactivated position to their discharge position by a mechanical action, for example manually by an operator pressing or tapping on the bistable mechanical discharge element 7, possibly with a tool. This action can also be performed by a dedicated machine, a robotic arm, etc., and be automated.

[0074] The discharge position is preferably obtained by applying pressure that moves the bistable mechanical discharge element 7 into a depressed position, such that this discharge position is irreversible. This irreversible position has the advantage of preventing confusion between a fully discharged battery and a battery on which the bistable mechanical element 7 has not yet been activated. The bistable mechanical element 7 constitutes, or includes, such a visual indicator of its state.

[0075] The wall of the housing may for example have a substantially median plane (the plane in which the wall extends, outside of the bistable mechanical discharge elements 7), and the bistable mechanical discharge element may be configured so that its deactivated position and its discharge position are located on either side of this median plane (for example, in Figures 1, 2, 6, 8 on the one hand, and in Figures 5, 7, 10 and 11 on the other hand, the bistable mechanical discharge element is located on one side and then on the other side of the median plane).

[0076] The battery further comprises a resistive discharge circuit 9 connecting the two electrical contact interfaces 8 of the same bistable mechanical discharge element 7. The resistive discharge circuit 9 can, for example, be integrated into the wall of the housing 2, engraved on its surface, or consist of an element attached to this surface.

[0077] The resistive discharge circuit 9 can also be implemented using a resistive conductor directly connected to the electrical contact interfaces 8 (as, for example, in Figures 6 and 7). This resistive conductor is then formed from a portion of conductive material whose electrical resistance is calibrated according to the application. In this case, the electrical contact interfaces 8 and the resistive conductor can be made of a single piece, the electrical contact interfaces 8 being directly in line with the resistive conductor. Furthermore, the electrical contact interfaces 8 and the resistive conductor can be made of the same material, which implies an electrical contact with a certain electrical resistance between the electrical contact interfaces 8 and the internal contact terminals 4. This is not at all problematic and, on the contrary, contributes to the dissipation function during discharge.

[0078] The resistive discharge circuit 9 can also be constituted by an external circuit which includes a resistive dipole electrically connected to the electrical contact interfaces (as for example in Figures 11 and 12).

[0079] When the bistable mechanical discharge element 7 is placed in its discharge position, the electrical contact interfaces 8 come into contact with the internal contact terminals 4, so that the resistive conductor closes the circuit between two of the internal contact terminals 4. Note that even if the contact between the electrical contact interfaces 8 and the corresponding internal contact terminals 4 is of poor quality (because this contact is ensured only by the pressure exerted by the bistable mechanical discharge element 7 in the discharge position), this does not impair the discharge operation, and on the contrary it contributes to the function by adding an additional resistive element.

[0080] The example in Figures 8 and 9 illustrates two bistable mechanical discharge elements 7 with their resistive discharge circuit 9, here consisting of a resistive conductor. Each resistive discharge circuit 9 connects the terminals of a cell 1 through this resistive discharge circuit 9, thus enabling controlled discharge of the cell by transforming electrical energy into heat dissipated by Joule heating. Each cell 1 of the battery is thus discharged in a controlled manner by calibrating the electrical resistance value of the resistive discharge circuit 9.

[0081] Such a resistive discharge circuit 9 consisting of a resistive conductor which may be external to the housing 2 is illustrated in the examples of figures 8, 10, 11 and 12.

[0082] In [Fig.9], the resistive discharge circuit 9 is not in place, in order to make visible the structure of the bistable mechanical discharge elements 7.

[0083] Such a resistive discharge circuit 9, consisting of an external resistive conductor, makes it possible, in particular, to dissipate heat outside the housing 2 and to facilitate the cooling of this resistive discharge circuit 9 (cooling which can be natural or active). Advantageously, this construction also allows the connection in parallel with the resistive discharge circuit 9, while keeping the latter in place, of additional, more efficient discharge means 10 (for example, with active cooling means), as illustrated in [Fig. 11]. In [Fig. 11], the additional discharge means 10 comprise resistive elements, heat dissipation elements, and active cooling elements (an airflow is schematically represented by arrows around the additional discharge means 10).When the bistable mechanical discharge elements 7 are in the deactivated position (for example in Figures 1, 2, 3, 4, 6, 8), the electrical contact interfaces 8 are away from the internal contact terminals 4 and, when the bistable mechanical discharge elements 7 are in the discharge position (for example in Figures 5, 7, 10, 11 and 12), the electrical contact interfaces 8 come against the internal contact terminals 4, of . so that a circuit is closed between the internal contact terminals 4 (i.e. between the terminals of one or more cells in series and / or parallel) and the corresponding resistive discharge circuit 9.

[0084] The resistive discharge circuit 9 of each bistable mechanical discharge element 7 is advantageously fixed against a wall of the housing 2, so that the housing 2 acts as a heat dissipation radiator during the discharge of the cells 1. The thermal contact can be improved by a thermally conductive layer (such as a film or thermal paste, for example) which improves the thermal conduction between the resistive discharge circuit 9 and the housing 2. In the example where the bistable mechanical discharge elements 7 are made by stamping into a wall of the housing 2, this heat dissipation function is further enhanced.

[0085] In the case where the portion of the housing 2 which carries the bistable mechanical discharge element 7 is made of electrically conductive material (for example a metal sheet), the resistive discharge circuit 9 is further electrically isolated from the housing 2 by an electrically insulating layer disposed between the resistive discharge circuit 9 and the wall of the housing 2. The electrically insulating layer and the thermally conductive layer can be made of a single piece.

[0086] The resistive discharge circuit 9 of the bistable discharge elements 7 can also be arranged outside the housing 2, for example by means of electrical contact interfaces 8 that pass through the housing 2. Each of the electrical contact interfaces 8 then comprises a through-hole element having an external electrical contact. In the example shown in Figures 9 to 12, each bistable discharge element 7 consists of two stamped portions of the housing 2 into which the internal contact terminals 4 are fixed (for example, by crimping). These internal contact terminals are in the form of a conductive element passing through the wall of the housing 2 with an external electrical contact accessible from outside the housing 2.

[0087] Fig. 9 illustrates such a bistable mechanical discharge element 7, in the deactivated position, with the internal contact terminals 4 away from the electrical contact interfaces 8.

[0088] Fig. 10 illustrates this bistable mechanical discharge element 7 after it has been engaged in the discharge position, with the internal contact terminals 4 coming into contact with the electrical contact interfaces 8.

[0089] Fig. 11 illustrates this same battery with the resistive discharge circuit 9 in place, connected to the internal contact terminals 4 by their external electrical contacts accessible from outside the case 2, and supplemented by additional discharge means 10.

[0090] Fig. 12 is a similar view to Fig. 9, but without additional discharge means 10, with the bistable mechanical discharge element 7 in the discharge position and with the resistive discharge circuit 9 in place.

[0091] The resistive discharge circuit 9 has an electrical resistance sized according to the power of the battery.

[0092] By way of example, for a battery with a total voltage of approximately 400 V and a capacity of approximately 150 Ah, a resistance of approximately 100 Ω allows for controlled heat dissipation during battery discharge (with the bistable mechanical discharge elements 7 in the discharge position), compatible with the removal of this heat through the battery casing, and complete discharge of the battery within 72 hours for a battery arriving at the recycling center fully charged (worst-case scenario). For a battery cell with a capacity of approximately 50 Ah, the resistive discharge circuit 9 can have a resistance of approximately 1 Ω.

[0093] According to one embodiment, the resistive discharge circuit 9 is sized to ensure a discharge of the cells 1 in accordance with a predetermined discharge time for cells 1 initially fully charged.

[0094] Such a predetermined discharge time is advantageously: - a minimum of 3 hours, and preferably a minimum of 12 hours (which corresponds to a maximum discharge current of C / 3, and preferably of C / 12); - a maximum of 1 week (168 hours), and preferably a maximum of 72 hours (which corresponds to a discharge current of a minimum of C / 168, and preferably of a minimum of C / 72).

[0095] During the discharge process, a discharge parameter can be measured, such as, for example, the discharge time, the temperature of the battery's outer casing (the invention makes it possible to locate the temperature rise in the area of ​​the resistive discharge circuit 9, and the temperature profile thus reflects the battery's discharge state), and the voltage across its terminals (if the latter is accessible). When a discharge criterion is reached, the battery is then declared discharged, for example, by an audible or visual indicator, the activation of a software indicator (a "flag") in management software, etc.

[0096] The discharge criterion is, for example, reaching a maximum discharge time (e.g., 72 hours), the return of the battery's outer casing to ambient temperature monitored by a thermal camera or temperature stickers, for example, zero voltage across the battery terminals, etc. More advanced technical solutions could be considered, such as a discharge end indicator light, a Hall effect sensor to evaluate the discharge current, etc.

[0097] In addition, the discharge process may include a diagnostic step in which a consistency parameter is checked, and if this consistency parameter is not met, the battery is redirected to a dedicated process, for example a special recycling line for hazardous batteries.

[0098] The consistency parameter can be, for example, the homogeneity of the heat dissipated in the resistive discharge circuit 9 during discharge. A temperature measurement is taken at different locations in the battery (for example, using a thermal imaging camera), and if cold spots are detected in the resistive discharge circuits 9, whose average temperatures should be high due to overall heat dissipation, this means that certain cells are not in a discharge state even though the corresponding bistable mechanical discharge element 7 is in the discharge position. The diagnostic step can be calibrated so that, beyond a certain inconsistency criterion (for example, ten cold spots corresponding to ten cells that are not in a discharge state), the battery is reoriented.

[0099] The fact that some cells in a battery are not discharged, even though all the other cells are, may reveal an internal anomaly in the battery, such as a fault in the internal power connections, or a fault in those cells, triggering individual safety mechanisms for those cells. This indicates that, potentially, these cells cannot be discharged by the process and therefore potentially contain energy, thus justifying redirecting the battery towards more complete and safer analysis and disassembly methods.

Claims

Demands

1. An electrical energy storage battery, comprising at least one housing (2) and at least one battery cell (1) disposed in this housing (2), this battery being characterized in that it comprises: - at least two internal contact terminals (4) located inside the housing (2) and each connected to a connection terminal (5) of a battery cell (1); - at least one bistable mechanical discharge element (7) accessible from outside the housing (2) and disposed opposite two of said internal contact terminals (4), the bistable mechanical discharge element (7) comprising at least two electrical contact interfaces (8), and being adapted to occupy two stable positions: a deactivated position in which the electrical contact interfaces (8) are away from the internal contact terminals (4) and a discharge position in which the electrical contact interfaces (8) are each in contact with an internal contact terminal (4);- a resistive discharge circuit (9) connecting the two electrical contact interfaces (8) of the bistable mechanical discharge element (7).;

2. Battery according to claim 1, characterized in that the bistable mechanical discharge element (7) is disposed on a wall of said case (2).

3. Battery according to any one of the preceding claims, characterized in that said wall has a substantially median plane, the deactivated position and the discharge position of the bistable mechanical discharge element (7) being located on either side of this median plane.

4. Battery according to any one of the preceding claims, characterized in that the electrical contact interfaces (8) are fixed on an internal face of said wall of the case (2).

5. Battery according to any one of the preceding claims, characterized in that the bistable mechanical discharge element (7) is disposed on a cover of the case (2).

6. Battery according to any one of claims 2 to 5, characterized in that the bistable mechanical discharge element (7) consists of at least one stamped part on the wall of the case (2).

7. Battery according to any one of the preceding claims, characterized in that the resistive discharge circuit (9) comprises a resistive conductor.

8. Battery according to claim 7, characterized in that the electrical contact interfaces (8) and said resistive conductor are made of a single piece.

9. Battery according to any one of claims 1 to 6, characterized in that the resistive discharge circuit (9) comprises a resistive dipole.

10. Battery according to any one of the preceding claims, characterized in that the resistive discharge circuit (9) is arranged inside the casing (2).

11. Battery according to any one of claims 1 to 9, characterized in that the resistive discharge circuit (9) is disposed outside the case (2).

12. Battery according to claim 11, characterized in that the electrical contact interfaces (8) each comprise a through-element having an external electrical contact.

13. Battery according to claim 12, characterized in that it further comprises additional discharge means (10) connected in parallel with the resistive discharge circuit (9).

14. Battery according to any one of the preceding claims, characterized in that the resistive discharge circuit (9) is fixed against a wall of said case (2).

15. Battery according to claim 14, characterized in that it comprises an electrically insulating layer disposed between the resistive discharge circuit (9) and said wall of the case (2).

16. Battery according to any one of claims 14 or 15, characterized in that it comprises a thermally conductive layer disposed between the resistive discharge circuit (9) and said wall of the case (2).

17. Battery according to any one of the preceding claims, characterized in that the internal contact terminals (4) are constituted by a free portion of a connection terminal (5) of one of the battery cells (1).

18. Battery according to any one of claims 1 to 17, characterized in that the internal contact terminals (4) are constituted by a free portion of a power conductor (6) connected to battery cells (1).

19. Battery according to any one of the preceding claims, characterized in that the resistive discharge circuit (9) is sized for ensure battery discharge in accordance with a predetermined discharge time, for the initially fully charged battery.

20. Battery according to claim 19, characterized in that said predetermined discharge time is a minimum of 3 hours, and preferably a minimum of 12 hours.

21. Battery according to claim 19, characterized in that said predetermined discharge time is at most 168 hours, and preferably at most 72 hours.

22. A method for discharging a battery according to any one of claims 1 to 21, characterized in that it comprises the following steps: - mechanically stressing from outside the battery the bistable mechanical discharge element (7) towards its discharge position; - measuring a discharge parameter and declaring the battery discharged following the attainment of a discharge criterion.

23. Method according to claim 22, characterized in that the discharge criterion is a predetermined discharge time.

24. A method according to claim 22, characterized in that the discharge criterion is a predetermined dissipated thermal power.

25. A method according to any one of claims 22 to 24, characterized in that the discharge method comprises a diagnostic step in which a consistency parameter is checked, and in the event that this consistency parameter is not met, the battery is redirected to a predetermined method.

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