Electrical energy storage unit

Abstract

The invention relates to an electrical energy storage unit, comprising at least two stages (2, 3), each stage having first and second current collectors (6 to 9) and at least one storage element (10) having an electrical energy storage cell (13) and a current-breaking device (14) coupled in series, the unit having a protection system (20) comprising at least one polarised electrical component (19, 23) and at least one additional current-breaking device (24, 39) coupled together in series and in parallel with at least one stage (2, 3), a polarised electrical component being configured to occupy a polarisation state in which a current passes through the polarised electrical component (23) when the current-breaking device (14) of each storage element (10) of the at least one stage is open, so as to drive the opening of the additional current-breaking device (24).

Description

[0001] "Electrical energy storage unit"

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention relates to electrical energy storage units, such as a battery, and more particularly a lithium-ion battery.

[0004] STATE OF THE ART

[0005] Currently, a multitude of devices are powered by power supply devices that include electrical energy storage units, such as batteries, and in particular lithium-ion batteries. During the lifetime of a device, storage unit malfunctions can occur. In particular, a storage unit can experience overheating or even thermal runaway, during which the temperature of the unit rises abnormally. This poses a risk of producing fumes, or even a fire in the unit, or an explosion.

[0006] Furthermore, battery manufacturers aim to constantly increase the energy of their batteries in order to improve their performance. Thus, the use of materials with high energy capacity but with highly exothermic behavior in the event of thermal runaway of the battery is increasingly common.

[0007] Typically, a battery consists of multiple tiers of electrical energy storage cells, or accumulators. The cells, or accumulators, in a given tier are electrically coupled in parallel, and the tiers are usually electrically coupled in series to increase the total voltage supplied by the battery when operating as an electrical energy generator.

[0008] To limit risks, cells are often equipped with a protection system such as a CID (current interrupting device) or a fuse (also called "wire bonding"). For example, each cell is electrically coupled in series to a CID, and the cell and CID assembly is called an accumulator. A CID is a switch that cuts off the flow of current in the event of overpressure in the accumulator. For example, a CID may include a pressure-sensitive elastic blade, i.e., a protective device configured to interrupt the flow of current during a fault. A CID occupies a closed state in which it allows the flow of current, and an open state in which the flow of current is interrupted.The elastic blade is placed in an airtight chamber inside the accumulator, which, under the effect of an increase in pressure in the accumulator due to a failure of the accumulator, for example an increase in temperature, deforms the elastic blade to open the circuit. More specifically, a CID opens under the effect of the pressure inside the accumulator. For example, at about 10 bar, the CID opens and interrupts the current. If the pressure continues to increase in the accumulator, a vent opens at about 15 bar to release the gases outside the accumulator. The action of the CID to open the circuit is irreversible, once opened, the CID can no longer close the circuit. Furthermore, the accumulator can be protected by a fuse placed outside the accumulator. In other cases, a cell may be electrically coupled in series with a fuse (i.e., the battery includes fuses instead of CIDs).A fuse is a protective device having an electrically conductive filament configured to melt under the effect of a temperature rise generated by an overcurrent passing through the filament. When the filament melts, the fuse opens the circuit, it is also said that the fuse is open. The action of the fuse to open the circuit is also irreversible. CIDs and fuses are also called current cut-off devices. But these current cut-off devices can generate electric arcs that risk causing thermal runaway of the cells, particularly when the last current cut-off device of a stage opens. Indeed, during a failure in the battery, a runaway, or an overcurrent, propagates in the stages of the battery causing the opening of the current cut-off devices of the cells.But not all current cut-off devices open at the same time, and a significant risk of an electric arc occurs when the current cut-off device associated with the last cell in a stage opens. When the last current cut-off device opens, the current cut-off device does not cut off the voltage supplied by a cell, which is a few volts, but the voltage generated by all the stages of the battery, which is potentially several hundred volts. Since the cell current cut-off devices are not sized for this, an electric arc can occur and cause thermal runaway of the cell, or even thermal runaway of the entire battery.

[0009] We can cite the European patent application EP2416405 A1, which discloses a battery pack, comprising a plurality of elements electrically connected in parallel between two collectors. First elements each comprise a cell connected to a fusible interconnection, and a specific element comprises a cell connected to a specific fusible interconnection having a permissible current intensity greater than that of the fusible interconnections of the first elements. In addition, the battery pack comprises an arc suppression system for the specific fusible interconnection. But the arc suppression system aims to protect the specific fusible interconnection of a particular cell, and requires the production of a specific assembly protecting a particular cell.

[0010] SUMMARY OF THE INVENTION

[0011] One aim is to overcome these drawbacks, and more particularly to provide protection suitable for any type of battery, in particular for the various protection systems for the battery's electrical energy storage cells.

[0012] Another objective is to improve the management of electric arcs that can form within a battery stage.

[0013] According to one aspect, there is provided an electrical energy storage unit, comprising at least two stages electrically coupled together in series, each stage comprising first and second current collectors and at least one storage element having first and second electrical terminals coupled respectively to the first and second current collectors of the stage, each storage element comprising an electrical energy storage cell and a current cut-off device electrically coupled in series between the first and second electrical terminals of the storage element.

[0014] The unit comprises a system for protecting a set of stages comprising at least one stage among said at least two stages of the unit, the protection system comprising at least one polarized electrical component and at least one additional current cut-off device electrically coupled together in series and electrically coupled in parallel with said at least one stage of the set of stages, said at least one polarized electrical component being configured to occupy a first polarization state in which a current does not flow through said at least one polarized electrical component when the current cut-off device of at least one storage element of each stage of the set of stages is closed, and a second polarization state in which a current flows through said at least one polarized electrical component when the current cut-off device of each storage element of at least one stage of the set of stages is open,and the current flowing through said at least one polarized electrical component causes said at least one additional current cut-off device to open.,

[0015] Thus, an electrical energy storage unit is provided equipped with a protection system suitable for any type of power cut-off device for the stages of the unit. Advantageously, by providing a protection system for a set of stages of the unit, the protection of the cells of the unit is simplified. Advantageously, the modification of the electrical characteristics of the power cut-off devices of the stages is avoided. Such a protection system is particularly suitable for units which include accumulators for which the CIDs are integrated and which cannot be modified. Furthermore, such a unit is particularly suitable for improving the management of electric arcs which could damage the unit.

[0016] BRIEF DESCRIPTION OF THE FIGURES

[0017] The aims, objects, as well as the characteristics and advantages of the invention will emerge more clearly from the detailed description of embodiments thereof, illustrated by the following accompanying drawings in which: Figure 1, schematically illustrates one embodiment of an electrical energy storage unit; Figure 2, schematically illustrates the storage unit illustrated in Figure 1, where at least one current cut-off device of each stage is closed; Figure 3, schematically illustrates the storage unit illustrated in Figure 1, where each current cut-off device of a stage is open; Figures 4 to 9, schematically illustrate other embodiments of an electrical energy storage unit.

[0018] The drawings are given by way of example and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily to the scale of practical applications.

[0019] DETAILED DESCRIPTION OF THE INVENTION

[0020] Before commencing a detailed review of embodiments and implementations of the invention, optional features which may possibly be used in combination or alternatively are set out below.

[0021] - According to one example, said at least one additional current cut-off device has a nominal voltage, that is to say a maximum voltage that can exist at the terminals of said at least one additional current cut-off device before creating an electric arc, strictly greater than that of the current cut-off device of each storage element of the set of stages.

[0022] - According to one example, the nominal voltage of said at least one additional current cut-off device is greater than or equal to an operating voltage provided by the electrical energy storage unit.

[0023] - According to one example, said at least one stage of the set of stages comprises several storage elements electrically coupled in parallel.

[0024] - According to one example, the storage elements of said at least one floor of the set of floors are identical.

[0025] - According to one example, said at least one polarized electrical component is configured to operate in a passive manner not requiring an external control to operate.

[0026] - According to one example, said at least one polarized electrical component is a diode.

[0027] - According to one example, said at least one polarized electrical component is a thyristor. Preferably, the thyristor has a first electrical terminal coupled to a current collector of said at least one stage of the set of stages, a second electrical terminal coupled to said at least one additional current cutoff device, and a third electrical terminal electrically coupled to the first electrical terminal of the thyristor.

[0028] - According to one example, the protection system comprises, for each stage of the set of stages, a polarized electrical component and an additional current cut-off device electrically coupled together in series between the first and second current collectors of the stage.

[0029] - According to one example, the set of stages comprises at least two stages electrically coupled together in series between first and second electrical terminals of the unit, and the protection system comprises a polarized electrical component and an additional current cut-off device electrically coupled together in series between the first and second electrical terminals of the unit.

[0030] - According to one example, said at least one additional power cut-off device is a fuse.

[0031] - For example, each additional power cut-off device is a fuse.

[0032] - According to one example, said at least one polarized electrical component has a first electrical terminal coupled to a current collector of said at least one stage of the set of stages, said at least one additional current cut-off device is an electropyrotechnic switch comprising an electrical conductor electrically coupled to a current collector of a stage of the unit, a movable cut-off member configured to cut the electrical conductor, and a controlled actuator electrically coupled in series between a second electrical terminal of said at least one polarized electrical component and the other current collector of said at least one stage of the set of stages, the actuator being configured to move the member so as to cut the electrical conductor when the actuator receives the current passing through said at least one polarized electrical component.

[0033] - According to one example, the electrical conductor is electrically coupled between the second current collector of said at least one stage of the set of stages and the first current collector of another stage of the unit.

[0034] - According to one example, the protection system comprises, for each stage of the set of stages, a polarized electrical component having a first electrical terminal electrically coupled to the second current collector of the stage, and the controlled actuator is electrically coupled in series between a second electrical terminal of each polarized electrical component and the first current collector of the stage, the controlled actuator being configured to move the member so as to cut the electrical conductor when the actuator receives the current passing through at least one polarized electrical component.

[0035] - According to one example, said at least one additional current cut-off device is an electro-pyrotechnic switch comprising an electrical conductor electrically coupled between a current collector of said at least one stage of the set of stages and a first electrical terminal of said at least one polarized electrical component, a movable cut-off member configured to cut the electrical conductor, and a controlled actuator electrically coupled in series between a second electrical terminal of said at least one polarized electrical component and the other current collector of said at least one stage of the set of stages, the actuator being configured to move the member so as to cut the electrical conductor when the actuator receives the current passing through said at least one polarized electrical component.

[0036] - According to one example, the unit comprises a control circuit and wherein at least one stage of the set of stages comprises an optocoupler configured to generate a current in the control circuit when a current flows through said at least one polarized electrical component.

[0037] - According to one example, the optocoupler comprises a light-emitting diode electrically coupled in parallel with said at least one polarized electrical component, and a phototransistor for converting the light energy emitted by the light-emitting diode into an electric current, the phototransistor being electrically coupled to the control circuit.

[0038] - In one example, the unit is configured to provide an operating voltage less than or equal to 100 V.

[0039] It is specified that in the context of the present invention, the expression "A coupled to B" or "A electrically coupled to B" is synonymous with "A is in electrical connection with B" and does not necessarily mean that there is no member between A and B. Thus these expressions are understood to mean an electrical connection between two elements, this connection being able or not to be direct, this means that it is possible that between a first device A and a second device B which are electrically connected, a current flows in A, in B, and on the path connecting A to B, this path being able or not to include other electrical equipment.

[0040] Conversely, in the context of the present invention, the term "electrically directly connected" or "directly connected" means a direct electrical connection between two elements. This means that between a first device A and a second device B which are electrically directly connected no other equipment is present, other than one or more electrical connections.

[0041] It is specified that in the context of the present invention, the term "electrically placed" or "electrically located" means positioning a device on a line in which a current flows.

[0042] Figures 1 to 3, 6, 8 and 9 show an electrical energy storage unit.

[0043] I , such as a battery and more particularly a Lithium-ion battery. The unit 1 comprises at least two stages 2, 3 electrically coupled together in series. The unit 1 may further comprise other stages 100, 101 , shown in FIG. 8, electrically coupled together in series or in parallel. The stages 2, 3 are coupled to a load 4, for example a connection circuit, used so that the unit 1 can provide an operating voltage Vf when it operates as an energy generator, or to charge the unit 1 when it operates as an energy accumulator. Preferably, the stages 2, 3 are coupled in series with the load 4 and electrically placed within a main electrical circuit 5.

[0044] Each stage 2, 3 comprises first and second current collectors 6 to 9 and at least one storage element 10.

[0045] Each storage element 10 comprises first and second electrical terminals

[0046] II, 12, an electrical energy storage cell 13 and a current cut-off device 14. The current cut-off device 14 may be a CID, and in this case the storage element 10 is also called an accumulator. In other words, the CID and the cell 13 are included in an enclosure of the accumulator. The CID is intended to protect the cell 13 against thermal runaway. The current cut-off device 14 may also be a fuse. The fuse is intended to protect the cell 13 against overcurrents. Alternatively, a storage element 10 may comprise an accumulator comprising a CID electrically coupled in series with the cell 13, and the unit 1 may further comprise an additional fuse, not shown for simplification purposes, electrically coupled in series between the CID of the accumulator and the second electrical terminal 12. Thus, the cell 13 may be protected against thermal runaway and overcurrents.Furthermore, the first and second electrical terminals 11, 12 are coupled respectively to the first and second collectors 6 to 9 of a stage 2, 3 of the unit 1. The cell 13 and the current cut-off device 14 of a storage element 10 are electrically coupled in series between the first and second terminals 11, 12 of the storage element 10. In particular, when a stage 2, 3 comprises several storage elements 10, the storage elements 10 are mounted in parallel between the collectors 6 to 9 of the stage 2, 3. Thus, the unit 1 can comprise several storage elements 10 associated in series and in parallel. The series connection makes it possible to increase the total voltage of the unit 1. The parallel connection makes it possible to increase the total storage capacity of the unit 1. Preferably, the first and second electrical terminals 11, 12 of each storage element 10 are connected directly to the collectors 6 to 9 of a stage 2, 3 of the unit 1.

[0047] A cell 13 comprises an electrolyte placed between two electrodes to provide a current and a voltage when it is charged. The voltage provided by a cell 13 is denoted cell voltage Vcel. For example, the cells 13 of stages 2, 3 are configured to provide a voltage of a few volts, for example 4.1 Volts, and the storage unit 1 comprises several stages 2, 3 to provide an operating voltage of a few tens of volts, preferably an operating voltage less than or equal to 100 Volts. For example, a stage 2, 3 may comprise several storage elements 10 coupled in parallel between the collectors 6 to 9 of the stage 2, 3. Preferably, the storage elements 10 of a stage 2, 3 are identical.

[0048] A current cut-off device 14 is a protective member intended to protect the cell 13, with which it is associated. A current cut-off device 14 is configured to interrupt the flow of current during a fault. A current cut-off device 14 occupies a closed state (in normal operation) in which it allows the flow of current, and an open state (in the case of a fault) in which the flow of current is interrupted. When the current cut-off device 14 is a CID, it protects the cell 13 against thermal runaway. In particular, a CID opens when overpressure occurs inside the accumulator. The overpressure is generated because the accumulator begins to run away, generating heat and gas formation. A current cut-off device 14 may be, for example, a fuse to protect the cell 13 against overcurrents.A fuse comprises a connection capable of closing the circuit during normal operation, and opening the circuit in the event of a fault. The connection is deliberately “fragile”, for example a small cross-section electrical wire capable of melting in the event of an overcurrent. In particular, when an overcurrent passes through the fuse, it melts and opens the circuit. Furthermore, a storage element 10 may comprise both a CID and a fuse electrically coupled in series between the cell 13 and the second electrical terminal 12 of the storage element 10.

[0049] More particularly, the unit 1 comprises a protection system 20 for a set of stages 50 comprising at least one stage 2, 3 among the stages 2, 3 of the unit 1. In other words, the set of stages comprises one or more stages 2, 3 electrically coupled together in series. It is also noted that the protection system 20 is intended to protect the stage(s) 2, 3 of the set of stages 50. In general, the protection system 20 aims to divert a current when all the current cut-off devices 14 of a stage 2, 3 of the set of stages 50 open, to an additional current cut-off device 24, 39 in order to interrupt the flow of current in the unit 1. When all the current cut-off devices 14 of a stage 2, 3 open, it is said that the stage 2, 3 is faulty, and the diverted current is noted as “image current of a faulty stage”.More particularly, the protection system 20 is configured so that the additional current cut-off device 24, 39 opens when it receives the diverted current in order to interrupt the flow of current in the unit, i.e. to protect the unit. The protection system 20 also aims to eliminate the creation of an electric arc by at least one of the current cut-off devices 14 of a faulty stage 2, 3. In particular, a current cut-off device 14 can generate an electric arc when it opens, because the voltage at its terminals exceeds a voltage, denoted nominal voltage.

[0050] The protection system 20 comprises at least one polarized electrical component 19, 23 and at least one additional current cut-off device 24, 39 electrically coupled together in series and electrically coupled in parallel with at least one stage 2, 3 of the set of stages 50. Thus, a polarized electrical component 19, 23 is configured to allow a current to pass, when a stage 2, 3 is faulty, to an additional current cut-off device 24, 39. The additional current cut-off device 24, 39 is configured to interrupt the flow of a current in the unit 1 when it receives the diverted current. The protection system 20 also has the role of preventing the passage of current, in the additional current cut-off device(s) 24, 39, during normal operation of the storage unit 1, that is to say when the unit 1 supplies an operating voltage from the cell voltages Vcel supplied by the cells 13.In this case, the current does not flow through the additional current cut-off device 24, 39 and in particular the additional current cut-off device 24, 39 is not active in normal operation. Furthermore, when a fault occurs in a stage 2, 3 of the set of stages 50, and all the current cut-off devices 14 of the stage 2, 3 open, the protection system 20 allows the current to flow through an additional current cut-off device 24, 39 so that the current is diverted into the protection system 20 and there is no more current in the current cut-off devices 14 of the stage 2, 3. Thus the current cut-off devices 14, and more particularly the last current cut-off device of the stage 2, 3, open under zero current and there is no creation of an electric arc.Due to the diverted current, the last additional current cut-off device 24, 39 opens to permanently interrupt the current in the storage unit 1.

[0051] A polarized electrical component 19, 23 is configured to occupy a first polarization state, called the blocked state, in which a current does not flow through the polarized electrical component 19, 23 and a second polarization state, called the on state, in which a current flows through the polarized electrical component 19, 23. More particularly, a polarized electrical component 19, 23 of the protection system 20 is configured to occupy the blocked state when the current cut-off device 14 of at least one storage element 10 of each stage 2, 3 of the set of stages 50 is closed. In this case, the current flows in the stage(s) 2, 3 of the set of stages 50, passing through at least one current cut-off device 14 which is closed, without passing through the protection system 20.Furthermore, the polarized electrical component 19, 23 is configured to occupy the on state when the current cut-off device 14 of each storage element 10 of at least one stage 2, 3 of the set of stages 50 is open. In this case, the current flows in the protection system 20. The passage of the current in the protection system 20 will pass through the additional current cut-off device 24, 39 and trigger its opening to interrupt the passage of the current in the set of stages 50 and therefore in the unit 1.

[0052] Generally, a polarized electrical component 19, 23 comprises first and second electrical terminals 22, 21, at least one of which is coupled to an additional current cut-off device 24, 39 and the other of which is coupled to at least one current collector 6 to 9 of a stage 2, 3 of the set of stages 50. For example, a polarized electrical component 19, 23 may be a diode 25, as illustrated in FIGS. 1 to 3 and 5 to 9, or a thyristor 26, as illustrated in FIG. 4. A diode 25 is a polarized electrical dipole, called passive because it does not require the application of a control voltage to operate. The diode 25 allows current to pass in one direction, noted forward direction, that is to say it is conductive, and blocks current in the other direction, noted reverse direction. Furthermore, the diode 25 comprises a first electrical terminal 22, denoted cathode, and a second electrical terminal 21, denoted anode.A thyristor 26 is a three-terminal semiconductor electronic switch. A thyristor 26 is a polarized electrical dipole, called active because it has a first electrical terminal 22, denoted cathode, a second electrical terminal 21 denoted anode, and a third electrical terminal 29, denoted trigger. The thyristor 26 operates as a diode between its first and second terminals 22, 21. The third terminal 29 is used to control the thyristor 26. The third terminal 29 is electrically coupled to the cathode 22 of the thyristor 26.

[0053] In Figure 1, the storage unit 1 is illustrated in a normal operating state. In this case, the storage unit 1 supplies an operating voltage Vf across the load 4. The current cut-off devices 14 of the stages 2, 3 of the set of stages 50 are closed, and a current In flows in the main circuit 5 and in each of the stages 2, 3 of the unit. Each cell 13 supplies a voltage Vcel, and the voltage supplied by a stage 2, 3 of the unit is denoted by the reference Vet. More particularly, the polarized electrical components 19, 23 are in a blocked state, and the voltage at the terminals 21, 22 of the polarized electrical components 19, 23 is represented by the reference Vd. In this case, the current does not flow between the terminals 21, 22 of the polarized electrical components 19, 23, and more particularly, the current does not flow in the additional current cut-off devices 24, 39 of the protection system 20.When the storage unit 1 is in normal operation, the cells 13 operate as current generators and the polarized electrical components 19, 23 are in a blocked state.

[0054] Furthermore, it is also said that the polarized electrical component 19, 23 is configured to operate in a passive manner not requiring an external control to operate. In particular, external control means a control voltage applied to an electrical terminal, called a control terminal and configured to control the opening and closing of a polarized electrical component, the applied control voltage not coming from the main circuit 5. A diode 25 does not have an electrical control terminal and operates passively. A diode 25 is therefore not a controlled electrical component. Furthermore, in the case where the polarized electrical component 19, 23 is a thyristor 26, it is said that the thyristor 26 is mounted passively, that is to say mounted so as to operate without needing to be controlled by an external control.In particular, when the third terminal 29 of the thyristor 26 is coupled to the first terminal 22 of the thyristor 26, the thyristor is said to be passively mounted. When the thyristor 26 is passively mounted, its third terminal 29 receives the voltage from the current collector 6 to 9 coupled to the first terminal 22 of the thyristor 26. Preferably, the third terminal 29 of the thyristor 26 is directly coupled to the first terminal 22 of the thyristor 26. In other words, its third terminal 29 receives a voltage coming directly from the current collector 6 to 9 of the main circuit 5, and not from a circuit external to the main circuit 5. It is also said that the passively mounted thyristor 26 is not controlled. Generally, it is said that a polarized electrical component configured to operate in a passive manner is not controlled.

[0055] In Figure 2, the storage unit 1 is shown when a fault, for example a short circuit or thermal runaway of a cell 13, occurs at a storage element 10. For example, when a storage element 10 comprises an accumulator incorporating a CID, and the accumulator has started its thermal runaway, the accumulator begins its internal reactions. Then there is generation of gas and a pressure increases inside the accumulator, which causes the CID to open. According to another example, when a storage element 10 comprises a fuse and an overcurrent flows in the fuse, the latter opens. In both of the above-mentioned cases, a thermal runaway or an overcurrent occurring in a storage element 10, the current cut-off device 14 of the storage element 10 opens.In Figure 2, a first current cut-off device 14 of a first stage 2 is shown open, that is to say that a fault has appeared in the storage element 10 of the first current cut-off device 14. In this case, the first current cut-off device 14 is open and the current flows in the first stage 2 through the other current cut-off devices 14 of the first stage 2 which are closed. The voltage Vet of the first stage 2 varies little and the polarized electrical components 19, 23 remain in the blocked state. When the fault is maintained, for example the short circuit has not disappeared or the thermal runaway propagates to the other cells 13 of the first stage 2, the current cut-off devices 14 of the first stage 2 will open in cascade until the last current cut-off device 14 of the first stage 2 opens.

[0056] In Figure 3, the storage unit 1 is shown when the last current cut-off device 14 of the first stage 2 opens. It is also said that the first stage 2 is faulty. In this case, all the current cut-off devices 14 of the first stage 2 are open and the cells 13 of the first stage no longer supply voltage. The cells 13 of the first stage 2 no longer operate as generators, while the current cut-off devices 14 of the other stages 3 of the unit can be closed and in this case the cells 13 of the other stages 3 of the unit operate as generators. When the last current cut-off device of the first stage 2 opens, the polarized electrical component 19 of the protection system 20 electrically coupled to the first stage 2 becomes conductive.In particular, the polarized electrical component 19 becomes conductive following the end of the presence of a stabilized voltage for the first stage 2 imposed by a cell 13 connected to one of the closed current cut-off devices 14. With the opening of the last current cut-off device 14 of the first stage 2, this voltage constraint is lifted and the polarized electrical component 19 becomes conductive because it finds itself in a current path imposed by the other stages 3 which are not faulty, as well as by the load 4. The voltage at the terminals 21, 22 of the polarized electrical component 19 is then established at the polarization voltage, i.e. approximately 0.7 V in the case of a diode.The polarized electrical component 19 prevents the last current cut-off device 14 of the first stage 2 from being opened under the sum of the voltages of the stages 3 which are not faulty, but from being opened under a voltage of the order of a voltage Vcel supplied by the faulty cell 13 increased by the polarization voltage Vd. This facilitates the opening of all the current cut-off devices 14 of the first stage 2. Thus, the current passes through the protection system 20, and in particular through the additional current cut-off device 24 which opens. The opening of the additional current cut-off device 24 interrupts the flow of current in the first stage 2, there is then no more current flowing in the last current cut-off device 14, since it is already open. The opening of the additional current cut-off device 24 causes the main circuit 5 to open and stops the operation of the unit 1.

[0057] Generally, at least one additional current cutoff device 24, 39 is electrically coupled to at least one polarized electrical component 19, 23, so as to be able to receive the current diverted by the polarized electrical component 19, 23.

[0058] In Figure 8, an embodiment is shown in which the set of stages 50 comprises at least two stages 2, 3 electrically coupled together in series between first and second electrical terminals 51, 52 of the unit 1. The unit 1 further comprises other stages 100, 101 coupled in series between the load 4 and the second electrical terminal 52 of the unit. Furthermore, the protection system 20 comprises a polarized electrical component 23 and an additional current cut-off device 39 electrically coupled together in series between the first and second electrical terminals 51, 52 of the unit 1.

[0059] In Figures 1 to 7, another embodiment is shown in which the protection system 20 comprises, for each stage 2, 3 of the set of stages 50, a polarized electrical component 19, 23 and an additional current cut-off device 24, 39 electrically coupled together in series between the first and second current collectors 6 to 9 of the stage 2, 3. An additional current cut-off device 24, 39 may be a fuse 30. This makes it possible to provide an effective and simple protection system 20 to be produced. Preferably, each additional current cut-off device 24, 39 of the protection system

[0060] 20 is a fuse. Alternatively, an additional current cut-off device 24, 39 may be a pressure-sensitive spring-loaded switch. According to another embodiment, an additional current cut-off device 24, 39 may be a thermistor, i.e., an electronic component whose resistance varies as a function of temperature. Preferably, the thermistor is made from a carbon polymer whose resistance increases as the temperature increases.

[0061] According to another embodiment, illustrated in Figures 5, 6 and 9, an additional current cut-off device 24, 39 is an electro-pyrotechnic switch 31. Generally, an electro-pyrotechnic switch 31 comprises an electrical conductor 32 electrically coupled to a current collector 6 to 9 of a stage 2, 3 of the unit 1. An electro-pyrotechnic switch 31 further comprises a movable cut-off member 33 configured to cut the electrical conductor 32, and a controlled actuator 34 configured to move the member 33 so as to cut the electrical conductor 32 when the actuator 34 receives the current passing through a polarized electrical component 19, 23. The actuator 34 is further electrically coupled in series between an electrical terminal 21, 22 of a polarized electrical component 19, 23 and a collector 6 to 9 of at least one stage 2, 3 of the set of stages 50.In this case, when a polarized electrical component 19, 23 is in the blocked state, the current does not flow through the controlled actuator 34. When the polarized electrical component 19, 23 is in the passing state, a current flows through the controlled actuator 34 which moves the member 33 to cut the electrical conductor 32 and interrupt the current between the terminals of the electrical conductor 32.

[0062] According to a first embodiment, illustrated in Figure 5, an electropyrotechnic switch 31 comprises an electrical conductor 32 electrically coupled between a second current collector 7, 9 of a stage 2, 3 of the set of stages 50, and a first electrical terminal 22 of a polarized electrical component 19, 23. Furthermore, the controlled actuator 34 is electrically coupled between the second electrical terminal

[0063] 21 of the polarized electrical component 19, 23 and the first current collector 6, 8 of stage 2, 3.

[0064] Alternatively, the electrical conductor 32 may be located anywhere in the main circuit 5 outside a stage 2, 3. For example, the electrical conductor 32 may be electrically coupled between a current collector 7, 9 of a stage 2, 3 and either to a current collector of another stage 6, 8, as shown in Figure 6, or to the load 4, as shown in Figure 9.

[0065] According to another embodiment, illustrated in Figure 6, an electropyrotechnic switch 31 comprises an electrical conductor 32 electrically coupled to a second current collector 7 of a first stage 2 of the set of stages 50, and to the first current collector 8 of a second stage 3 of the set of stages 50. Furthermore, the controlled actuator 34 is electrically coupled between the second electrical terminal 21 of a polarized electrical component 19 and the first current collector 6 of the first stage 2. Thus, when the polarized electrical component 19 of the first stage 2 is in the on state, a current flows through the controlled actuator 34 which moves the member 33 to cut the electrical conductor 32 and interrupt the current between the first and second stages 2, 3, and therefore in the unit 1.

[0066] In Figure 9, another embodiment is shown in which the protection system 20 comprises an additional current cut-off device 24 which is a pyrotechnic switch. Furthermore, the protection system 20 comprises, for each stage 2, 3 of the set of stages 50, a polarized electrical component 19, 23 having a first electrical terminal 22 electrically coupled to the second current collector 7, 9 of the stage 2, 3. Furthermore, the controlled actuator 34 of the pyrotechnic switch is electrically coupled in series between a second electrical terminal 21 of each polarized electrical component 19, 23 and the first current collector 6, 8 of the stage 2, 3. The controlled actuator 34 is further configured to move the member 33 of the pyrotechnic switch so as to cut the electrical conductor 32 of the pyrotechnic switch when the actuator 34 receives the current passing through at least one polarized electrical component 19, 23.Advantageously, the protection system 20 also comprises, for each stage 2, 3 of the set of stages 50, an additional polarized electrical component 53, 54, for example a diode 25, electrically coupled in series between the controlled actuator 34 and the first current collector 6, 8 of the stage 2, 3. Preferably, for each stage 2, 3 of the set of stages 50, the diode 25 has its cathode electrically coupled to the controlled actuator 34 and its anode electrically coupled to the first current collector 6, 8 of the stage 2, 3.

[0067] Advantageously, an additional current cut-off device 24, 39 has a nominal voltage, that is to say a maximum voltage that can exist at the terminals of the additional current cut-off device 24, 39 before creating an electric arc, greater than or equal to the operating voltage Vf supplied by the electrical energy storage unit 1. Such an additional current cut-off device 24, 39 is particularly suitable for operating voltages Vf that are less than or equal to 100 Volts. Furthermore, the nominal voltage of an additional current cut-off device 24, 39 can be strictly greater than that of the current cut-off device 14 of each storage element 10 of the set of stages 50. This prevents the formation of an electric arc at the last current cut-off device 14 of a stage 2, 3 which opens during a fault.

[0068] According to another advantage, an additional current cut-off device 24, 39 has a breaking capacity strictly greater than the breaking capacity of the current cut-off devices 14 of a stage 2, 3 of the set of stages 50. The breaking capacity corresponds to the maximum current that a current cut-off device 14, 24, 39 can cut without deteriorating. Thus, in the event of a short circuit, the additional current cut-off device 24 can cut the short-circuit current of the unit 1. Advantageously, the additional current cut-off device 24 can be configured to cut a current corresponding to at least the sum of the currents that the current cut-off devices 14 of a stage 2, 3 can allow to pass in nominal operation.

[0069] According to another example, illustrated in Figure 7, the unit 1 may comprise a control circuit 40, and a stage 2, 3 of the set of stages 50 comprises an optocoupler 41 configured to generate a current Is in the control circuit 40 when a current flows through a polarized electrical component 19, 23 of the protection system 20.

[0070] According to one embodiment, the optocoupler 41 comprises a light-emitting diode 42 electrically coupled in parallel with a polarized electrical component 19, 23, and a phototransistor 43 for converting the light energy emitted by the light-emitting diode 42 into an electric current Is to the control circuit 40. The phototransistor 43 is electrically coupled to the control circuit 40. Advantageously, the unit 1 may comprise a resistor, not shown for the sake of simplification, electrically coupled in series with the light-emitting diode 42, in order to limit the current flowing in the light-emitting diode 42 to protect it.

Claims

CLAIMS 1. Electrical energy storage unit, comprising at least two stages (2, 3) electrically coupled together in series, each stage (2, 3) comprising first and second current collectors (6 to 9) and at least one storage element (10) having first and second electrical terminals (11, 12) coupled respectively to the first and second current collectors (6 to 9) of the stage (2, 3), each storage element (10) comprising an electrical energy storage cell (13) and a current cut-off device (14) electrically coupled in series between the first and second electrical terminals (11, 12) of the storage element (10), characterized in that the unit comprises a protection system (20) for a set of stages (50) comprising at least one stage (2, 3) among said at least two stages (2, 3) of the unit, the protection system (20) comprising at least a polarized electrical component (19,23) and at least one additional current cut-off device (24, 39) electrically coupled together in series and electrically coupled in parallel to said at least one stage (2, 3) of the set of stages (50), said at least one polarized electrical component (19, 23) being configured to occupy a first polarization state in which a current does not flow through said at least one polarized electrical component (19, 23) when the current cut-off device (14) of at least one storage element (10) of each stage (2, 3) of the set of stages (50) is closed, and a second polarization state in which a current flows through said at least one polarized electrical component (19, 23) when the current cut-off device (14) of each storage element (10) of at least one stage (2, 3) of the set of stages (50) is open, and in that the current flowing through said at least a polarized electrical component (19,23) causes the opening of said at least one additional power cut-off device (24, 39)., 2. Unit according to the preceding claim, in which said at least one additional current cut-off device (24, 39) has a nominal voltage, i.e. a maximum voltage which can exist at the terminals of said at least one additional current cut-off device (24, 39) before creating an electric arc, strictly greater than that of the current cut-off device (14) of each storage element (10) of the set of stages (50).

3. Unit according to the preceding claim, wherein the nominal voltage of said at least one additional current cut-off device (24, 39) is greater than or equal to an operating voltage (Vf) supplied by the electrical energy storage unit.

4. Unit according to any one of the preceding claims, wherein said at least one stage (2, 3) of the set of stages (50) comprises several storage elements (10) electrically coupled in parallel.

5. Unit according to the preceding claim, in which the storage elements (10) of said at least one stage (2, 3) of the set of stages (50) are identical.

6. A unit according to any preceding claim, wherein said at least one polarized electrical component (19, 23) is configured to operate in a passive manner not requiring external control to operate.

7. Unit according to any one of the preceding claims, wherein said at least one polarized electrical component (19, 23) is a diode (25).

8. A unit according to any one of claims 1 to 6, wherein said at least one polarized electrical component (19, 23) is a thyristor (26) having a first electrical terminal (22) coupled to a current collector (6 to 9) of said at least one stage (2, 3) of the set of stages (50), a second electrical terminal (21) coupled to said at least one additional current cut-off device (24, 39), and a third electrical terminal (29) electrically coupled to the first electrical terminal (22) of the thyristor (26).

9. Unit according to any one of the preceding claims, in which the protection system (20) comprises, for each stage (2, 3) of the set of stages (50), a polarized electrical component (19, 23) and an additional current cut-off device (24, 39) electrically coupled together in series between the first and second current collectors (6 to 9) of the stage (2, 3).

10. A unit according to any one of claims 1 to 8, wherein the set of stages (50) comprises at least two stages (2, 3) electrically coupled together in series between first and second electrical terminals (51, 52) of the unit, and the protection system (20) comprises a polarized electrical component (23) and an additional current-breaking device (39) electrically coupled together in series between the first and second electrical terminals (51, 52) of the unit.

11. Unit according to any one of the preceding claims, wherein said at least one additional current cutting device (24, 39) is a fuse (30).

12. A unit according to any preceding claim, wherein each additional current-cutting device (24, 39) is a fuse (30).

13. Unit according to any one of claims 1 to 9, wherein said at least one polarized electrical component (19, 23) has a first electrical terminal (22) coupled to a current collector (6 to 9) of said at least one stage (2, 3) of the set of stages (50), said at least one additional current cut-off device (24, 39) is an electro-pyrotechnic switch (31) comprising an electrical conductor (32) electrically coupled to a current collector (6 to 9) of a stage (2, 3) of the unit, a movable cut-off member (33) configured to cut the electrical conductor (32), and a controlled actuator (34) electrically coupled in series between a second electrical terminal (21) of said at least one polarized electrical component (19, 23) and the other current collector (6 to 9) of said at least one stage (2, 3) of the set of stages (50),the actuator (34) being configured to move the member (33) so as to cut the electrical conductor (32) when the actuator (34) receives the current passing through said at least one polarized electrical component (19, 23)., 14. Unit according to the preceding claim, wherein the electrical conductor (32) is electrically coupled between the second current collector (7, 9) of said at least one stage (2, 3) of the set of stages (50) and the first current collector (6, 8) of another stage (2, 3) of the unit.

15. Unit according to claim 13, wherein the protection system (20) comprises, for each stage (2, 3) of the set of stages (50), a polarized electrical component (19, 23) having a first electrical terminal (22) electrically coupled to the second current collector (7, 9) of the stage (2, 3), and the controlled actuator (34) is electrically coupled in series between a second electrical terminal (21) of each polarized electrical component (19, 23) and the first current collector (6, 8) of the stage (2, 3), the controlled actuator (34) being configured to move the member (33) so as to cut the electrical conductor (32) when the actuator (34) receives the current passing through at least one polarized electrical component (19, 23).

16. Unit according to any one of claims 1 to 9, wherein said at least one additional current cutting device (24, 39) is an electro-pyrotechnic switch (31) comprising an electrical conductor (32) electrically coupled between a current collector (6 to 9) of said at least one stage (2, 3) of the set of stages (50) and a first electrical terminal (22) of said at least one polarized electrical component (19, 23), a movable cutting member (33) configured to cut the electrical conductor (32), and a controlled actuator (34) electrically coupled in series between a second electrical terminal (21) of said at least one polarized electrical component (19, 23) and the other current collector (6 to 9) of said at least one stage (2, 3) of the set of stages (50), the actuator (34) being configured to move the member (33) so as to cut the electrical conductor (32) when the actuator (34) receives the current passing through said at least one polarized electrical component (19, 23).

17. Unit according to any one of claims 1 to 16, comprising a control circuit (40) and wherein at least one stage (2, 3) of the set of stages (50) comprises an optocoupler (41) configured to generate a current (Is) in the control circuit (40) when a current passes through said at least one polarized electrical component (19, 23). 18.Unit according to the preceding claim, in which the optocoupler (41) comprises a light-emitting diode (42) electrically coupled in parallel with said at least one polarized electrical component (19, 23), and a phototransistor (43) for converting the light energy emitted by the light-emitting diode (42) into an electric current (Is), the phototransistor (43) being electrically coupled to the control circuit (40).

19. Unit according to any one of the preceding claims, configured to provide an operating voltage (Vf) less than or equal to 100 V.

Images