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 at least one polarised electrical component (19, 23, 24, 39) coupled in parallel with at least one stage (2, 3), the 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.

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. The cells in a tier are electrically coupled in parallel, and the tiers are usually electrically coupled in series to increase the total voltage provided 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 Cl D, 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. 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 can 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 rise in temperature 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 fuse's action of opening the circuit is also irreversible. CIDs and fuses are also called current-cutting devices. However, these current-cutting devices can generate electric arcs that risk causing thermal runaway of the cells, particularly when the last current-cutting device in a stage opens. Indeed, during a fault in the battery, a runaway, or overcurrent, propagates through the battery stages, causing the cell current-cutting devices to open. However, not all current-cutting devices open at the same time, and a significant risk of electric arcing occurs when the current-cutting device associated with the last cell in a stage opens.When the last current cut-off device is opened, 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. In addition, when all the CIDs of a stage are open, the main circuit is open and the battery stops functioning.

[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 of 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. When the fusible interconnections and the arc suppression system of a stage are open, the battery also ceases to function.

[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] Another object is to isolate a faulty stage while keeping the battery operating.

[0014] 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.

[0015] The unit comprises a set of stages comprising at least one stage among said at least two stages of the unit, and at least one polarized electrical component having first and second electrical terminals electrically coupled in parallel to 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.

[0016] Thus, an electrical energy storage unit is provided equipped with a polarized electrical component suitable for any type of current cut-off device of the stages of the unit. Advantageously, by providing a polarized electrical component 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 current cut-off devices of the stages is avoided. Such a polarized electrical component is particularly suitable for units which include accumulators for which the CIDs are integrated and which cannot be modified. Such a unit is particularly suitable for improving the management of electric arcs which can damage the unit. Furthermore, such a component is particularly suitable for maintaining the storage unit in operation in the event of a fault occurring in a stage of the unit.The polarized electrical component also makes it possible to isolate the stage where the fault occurs while allowing the unit to continue to supply electrical power, i.e. to operate.

[0017] BRIEF DESCRIPTION OF THE FIGURES

[0018] 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:

[0019] Figure 1 schematically illustrates an embodiment of an electrical energy storage unit;

[0020] Figure 2 schematically illustrates the storage unit illustrated in Figure 1, where at least one power cut-off device on each floor is closed;

[0021] Figure 3 schematically illustrates the storage unit shown in Figure 1, where each power cut-off device on a floor is open;

[0022] Figures 4 to 7 schematically illustrate other embodiments of an electrical energy storage unit.

[0023] 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.

[0024] DETAILED DESCRIPTION OF THE INVENTION

[0025] 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.

[0026] According to one example, said at least one polarized electrical component has a capacity to carry a current greater than or equal to a sum of the currents supplied by the cell of each storage element of the set of stages.

[0027] According to one example, when at least one polarized electrical component of at least one stage of the set of stages is in the second polarization state, the current cut-off device of each storage element of said at least one stage opens under a voltage strictly lower than an operating voltage supplied by the unit.

[0028] For example, the unit comprises, for each stage of the set of stages, at least one polarized electrical component having first and second electrical terminals coupled respectively to the first and second collectors of the stage, and when said at least one polarized electrical component of the stage of the set of stages is in the second polarization state, the current cut-off device of each storage element of the stage opens under a voltage equal to a sum of the voltage supplied by a cell and the voltage across said at least one polarized electrical component.

[0029] According to one example, said at least one stage of the set of stages comprises several storage elements electrically coupled in parallel.

[0030] According to one example, the storage elements of said at least one stage of the set of stages are identical.

[0031] According to one example, the unit comprises, for each stage of the set of stages, at least one polarized electrical component having first and second electrical terminals coupled respectively to the first and second collectors of the stage.

[0032] According to one example, the unit comprises, for each stage of the set of stages, at least two polarized electrical components each having first and second electrical terminals coupled respectively to the first and second collectors of the stage.

[0033] In one example, the set of stages includes at least two stages electrically coupled together in series between first and second electrical terminals of the unit, and the unit includes at least one polarized electrical component having first and second electrical terminals coupled respectively to the first and second electrical terminals of the unit.

[0034] According to one example, the at least one polarized electrical component is configured to operate in a passive manner not requiring an external control to operate.

[0035] According to one example, said at least one polarized electrical component is a diode.

[0036] According to one example, the at least one polarized electrical component is a thyristor. Preferably, the thyristor has a first electrical terminal coupled to a current collector of the at least one stage of the set of stages, a second electrical terminal coupled to another current collector of the set of stages, and a third electrical terminal electrically coupled to the first electrical terminal of the thyristor.

[0037] In one example, each biased electrical component is a diode. In one example, the at least one biased electrical component has a first electrical terminal coupled to the second current collector of the at least one stage of the set of stages, and the unit includes an electro-pyrotechnic switch including first and second electrical terminals electrically coupled in parallel to the at least one stage of the set of stages, a normally open electrical conductor between the first and second electrical terminals of the electro-pyrotechnic switch, a movable closing member configured to close the electrical conductor, and a controlled actuator electrically coupled in series between the second electrical terminal of the at least one biased electrical component and the first current collector of the at least one stage of the set of stages,the actuator being configured to move the member so as to close the electrical conductor when the actuator receives the current passing through said at least one polarized electrical component. 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 passes through said at least one polarized electrical component.,

[0038] According to one example, the optocoupler comprises a light-emitting diode electrically coupled in parallel with said at least one biased electrical component, and a phototransistor for converting light energy emitted by the light-emitting diode into a current, the phototransistor being electrically coupled to the control circuit.

[0039] In one example, the unit is configured to provide an operating voltage strictly greater than 100 V.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] In Figures 1 to 3, and 6 there is shown an electrical energy storage unit 1, such as a battery and more particularly a Lithium-ion battery. The unit 1 comprises at least two stages 2, 3 coupled together electrically in series. The unit 1 may further comprise other stages 100, 101, shown in Figure 6, coupled together electrically 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 11, 12, a cell 13 for storing electrical energy 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 envelope 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 can be protected against thermal runaways 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 increases the total voltage of unit 1. The parallel connection increases the total storage capacity of 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.

[0046] 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 several hundred volts, for example an operating voltage strictly greater than 100 Volts. For example, a stage 2, 3 may comprise several storage elements 10 coupled in parallel between the collectors 6 to 9 of stage 2, 3. Preferably, the storage elements 10 of a stage 2, 3 are identical.

[0047] 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 connector capable of closing the deliberately “fragile” circuit, for example a small-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.

[0048] More particularly, the unit 1 comprises at least one polarized electrical component 19, 23, 24, 39 for protecting 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 polarized electrical component 19, 23, 24, 39 is intended to protect the stage(s) 2, 3 of the set of stages 50. Generally, the polarized electrical component 19, 23, 24, 39 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, while maintaining a flow of current in the stage 2, 3 in order to keep the unit 2 in operation. When all the current cut-off devices 14 of a stage 2, 3 open, we say that stage 2, 3 is faulty, and we note the diverted current "image current of a faulty stage".The polarized electrical component 19, 23, 24, 39 also aims to eliminate the creation of an electric arc by at least one of the current breaking devices 14 of a faulty stage 2, 3. In particular, a current breaking device 14 can generate an electric arc when it opens, because the voltage at its terminals exceeds a voltage, denoted nominal voltage. The polarized electrical component 19, 23, 24, 39 is configured to allow a current to pass, when a stage 2, 3 is faulty, to isolate the faulty stage 2, 3 and maintain the unit 1 in normal operation, that is to say when the unit 1 provides an operating voltage from the cell voltages Vcel provided by the cells 13 of the stages which are not faulty.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 polarized electrical component 19, 23, 24, 39 allows the current to pass into a parallel circuit of the faulty stage 2, 3 so that the current is diverted by the polarized electrical component 19, 23, 24, 39 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 storage unit 1 can continue to operate using the stages which are not faulty.Generally, a polarized electrical component 19, 23, 24, 39 is configured to occupy a first polarization state, called the off state, in which a current does not flow through the polarized electrical component 19, 23, 24, 39 and a second polarization state, called the on state, in which a current flows through the polarized electrical component 19, 23, 24, 39. More particularly, a polarized electrical component 19, 23, 24, 39 is configured to occupy the off 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 polarized electrical component 19, 23, 24, 39.Furthermore, the polarized electrical component 19, 23, 24, 39 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 stage 2, 3 by passing through the polarized electrical component 19, 23, 24, 39; the current is also said to be diverted. The passage of the current in the polarized electrical component 19, 23, 24, 39 will flow in the storage elements 10 of the stages 3 which are not faulty and thus allow the storage unit 1 to continue to operate.

[0049] Generally, a polarized electrical component 19, 23, 24, 39 comprises first and second electrical terminals 22, 21, at least one of which is coupled to a current collector 6 to 9 of a stage 2, 3 of the set of stages 50 and the other is coupled to another current collector of the set of stages 50. For example, as illustrated in FIGS. 1 to 5 and 7, the unit comprises, for each stage 2, 3 of the set of stages 50, at least one polarized electrical component 19, 23, 24, 39 having first and second electrical terminals 21, 22 respectively coupled to the first and second collectors 6 to 9 of the stage 2, 3. It is also said that at least one polarized electrical component 19, 23, 24, 39 is associated with a stage 2, 3 of the 50-story complex.Advantageously, as illustrated in Figures 1 to 3, the unit 1 comprises at least two polarized electrical components 19, 23, 24, 39 electrically coupled in parallel with the first and second current collectors 6 to 9 of a stage 2, 3 of the set of stages 50. According to another example, illustrated in Figure 6, 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. The unit 1 comprises at least one polarized electrical component 19, 23, 24, 39 having first and second electrical terminals 21, 22 coupled respectively to the first and second electrical terminals 51, 52 of the unit 1.In this case, each polarized electrical component 19, 23, 24, 39 is electrically coupled in parallel to the first and second electrical terminals 51, 52 of the unit 1. In this case, it is said that at least one polarized electrical component 19, 23, 24, 39 is associated with several stages 2, 3 of the set of stages 50.

[0050] For example, a polarized electrical component 19, 23, 24, 39 may be a diode 25, as illustrated in Figures 1 to 3 and 5 to 7, or a thyristor 26, as illustrated in Figure 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 flow in one direction, noted as the forward direction, that is to say it is conductive, and blocks current in the other direction, noted as the reverse direction. In addition, the diode 25 has a first electrical terminal 22, noted as the cathode, and a second electrical terminal 21, noted as the anode. A thyristor 26 is a three-terminal semiconductor electronic switch. A thyristor 26 is a polarized electric dipole, called active because it has a first electrical terminal 22, noted cathode, a second electrical terminal 21 noted anode, and a third electrical terminal 29, noted trigger.Thyristor 26 operates as a diode between its first and second terminals 22, 21. Third terminal 29 serves to control thyristor 26. Third terminal 29 is electrically coupled to cathode 22 of thyristor 26.

[0051] 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, 24, 39 are in a blocked state, and the reference Vd represents the voltage at the terminals 21, 22 of the polarized electrical components 19, 23, 24, 39. In this case, the current does not flow between the terminals 21, 22 of the polarized electrical components 19, 23, 24, 39.When the storage unit 1 is in normal operation, the cells 13 operate as current generators and the polarized electrical components 19, 23, 24, 39 are in a blocked state.

[0052] Furthermore, it is also said that the polarized electrical component 19, 23, 24, 39 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, 24, 39 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 speaking, it is said that a polarized electrical component configured to operate in a passive manner is not controlled.

[0053] In Figure 2, the storage unit 1 is shown when a fault, for example a short circuit or thermal runaway of a cell 13, appears 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.

[0054] 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 cases, a thermal runaway or an overcurrent occurs 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 a fault has occurred 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 into 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, 24, 39 remain in the blocked state.When the fault is maintained, for example the short circuit has not disappeared or the thermal runaway spreads 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.

[0055] In Figure 3, the storage unit 1 is shown when the last power cut-off device 14 of the first stage 2 opens. The first stage 2 is also said to be faulty. In this case, all the power cut-off devices 14 of the first stage 2 are open and the cells 13 of the first stage no longer supply current. The cells 13 of the first stage 2 no longer operate as generators, while the power 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 power cut-off device 14 of the first stage 2 opens, each polarized electrical component 19, 23 associated with the first stage 2 becomes conductive.In particular, the polarized electrical components 19, 23 become conducting 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 components 19, 23 become conducting because they find themselves 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 components 19, 23 is then established at the polarization voltage, i.e. approximately 0.7 V in the case of a diode.A polarized electrical component 19, 23 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 voltage of the polarization Vd. In other words, before a polarized electrical component 19, 23 passes from the blocked state to the conducting state, the last current cut-off device 14 opens under a voltage close to the voltage Vcel supplied by the cell 13 to which the last current cut-off device 14 is coupled.This facilitates the opening of all the current cut-off devices 14 of the first stage 2. Thus, when a stage 2 is faulty, the polarized electrical components 19, 23 associated with stage 2 allow the current cut-off devices 14 of stage 2 to open under a voltage strictly lower than the operating voltage Vf supplied by the storage unit 1. More particularly, the last current cut-off device 14 which opens will have at its terminals a voltage approximately equal to a sum of the voltage Vcel of the faulty cell 13 and the voltage Vd at the terminals 21, 22 of the polarized electrical component 19, 23, 24, 39.

[0056] For example, the voltage across the terminals of the last open current cut-off device 14 will be equal to the voltage of a cell (i.e., for example, 4.2 or 4.3 V if the cell 13 is fully charged) plus the voltage of the polarized electrical component 19, 23, 24, 39 (i.e., for example, 0.7 V), i.e., a voltage approximately equal to 5 V. For example, in the case where a polarized electrical component 23 is associated with four stages of the set of stages 50, the last current cut-off device 14 that opens will have at its terminals a voltage, called a fault voltage, approximately equal to a sum of the voltage supplied by the three stages in operation (i.e., 3 x 4.2 V if the cells 13 are fully charged), the voltage Vcel of the faulty cell 13 (i.e., 4.2 V if the cell 13 is fully charged), and the voltage Vcel of the faulty cell 13. full charge) and the voltage Vd at terminals 21, 22 of the polarized electrical component 23 (i.e. 0.7 V for a diode).In other words, the fault voltage will be approximately equal to 17.5 V. A current cut-off device 14 can be configured to cut off voltages of approximately 24 V. A polarized electrical component 23 is therefore suitable for being associated with several stages 2, 3, preferably between two and four stages.

[0057] When all the power cut-off devices 14 of the faulted stage 2 are open, stage 2 is isolated and the polarized electrical components 19, 23 associated with the isolated stage 2 allow the current to pass so that unit 1 can continue to operate.

[0058] Advantageously, a polarized electrical component 19, 23, 24, 39 has a capacity to carry a current greater than or equal to a sum of the currents supplied by the cell 13 of each storage element 10. In other words, the component 19, 23, 24, 39 is configured to switch to the on state in the event of a fault in the unit 1, without deteriorating.

[0059] According to another advantage, at least one stage 2, 3 comprises at least two diodes 25 coupled in parallel with a storage element 10 of stage 2, 3. Thus, the capacity to carry a current of each of the two diodes 25 can be reduced. In this way, the production of the unit 1 can be facilitated.

[0060] According to another embodiment, illustrated in Figure 7, the unit 1 comprises an electro-pyrotechnic switch 31, said to be normally open. Generally, a normally open electro-pyrotechnic switch 31 comprises an electrical conductor 32, a movable closing member 33, and a controlled actuator 34. In particular, the electrical conductor 32 is said to be normally open, that is to say that it occupies an open state in which the electrical conductor 32 does not allow a current to pass. Furthermore, the electro-pyrotechnic switch 31 comprises first and second electrical terminals 55, 56 electrically coupled in parallel with at least one stage 2, 3 of the set of stages 50. The electrical conductor 32 is further normally open between the first and second electrical terminals 55, 56 of the electro-pyrotechnic switch 31. The movable closing member 33 is configured to close the electrical conductor 32.The controlled actuator 34 is electrically coupled in series between the second electrical terminal 2 of a polarized electrical component 19, 23, 24, 39 and the first current collector 6 to 9 of a stage 2, 3 of the set of stages 50. Furthermore, the actuator 34 is configured to move the member 33 so as to close the electrical conductor 32 when the actuator 34 receives the current passing through the polarized electrical component 19, 23, 24, 39. In this case, when a polarized electrical component 19, 23, 24, 39 is in the blocked state, the current does not pass through the controlled actuator 34 and the electrical conductor 32 is open without a current passing through the electrical conductor 32.When the polarized electrical component 19, 23, 24, 39 is in the on state, a current flows through the controlled actuator 34 which moves the member 33 to close the electrical conductor 32 and allow the flow of current, i.e. the diverted current, between the terminals 55, 56 of the electro-pyrotechnic switch 31.

[0061] According to another example, illustrated in Figure 5, 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, 24, 39.

[0062] According to one embodiment, the optocoupler 41 comprises a light-emitting diode 42 electrically coupled in parallel with a polarized electrical component 19, 23, 24, 39, 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. Thus, information, of the alarm type, can be sent back to the control circuit 40 to indicate that a stage 2, 3 has been isolated and that the storage unit 1 is operating in a degraded mode. 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 set of stages (50) comprising at least one stage (2, 3) among said at least two stages (2, 3) of the unit, and at least one polarized electrical component (19, 23, 24, 39) having first and second electrical terminals (21,22) 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, 24, 39) 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, 24, 39) 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, 24, 39) 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., 2. Unit according to the preceding claim, in which said at least one polarized electrical component (19, 23, 24, 39) has a capacity to carry a current greater than or equal to a sum of the currents supplied by the cell (13) of each storage element (10) of the set of stages (50).

3. Unit according to any one of the preceding claims, in which, when at least one polarized electrical component (19, 23, 24, 39) of at least one stage (2, 3) of the set of stages (50) is in the second polarization state, the current cut-off device (14) of each storage element (10) of said at least one stage (2, 3) opens under a voltage strictly lower than an operating voltage (Vf) supplied by the unit.

4. Unit according to any one of the preceding claims, wherein the unit comprises, for each stage (2, 3) of the set of stages (50), at least one polarized electrical component (19, 23, 24, 39) having first and second electrical terminals (21, 22) coupled respectively to the first and second collectors (6 to 9) of the stage (2, 3), and when said at least one polarized electrical component (19, 23, 24, 39) of the stage (2, 3) of the set of stages (50) is in the second polarization state, the current cut-off device (14) of each storage element (10) of the stage (2, 3) opens under a voltage of the order of the sum between the voltage supplied by a cell (13) and the voltage at the terminals (21, 22) of said at least one polarized electrical component (19, 23, 24, 39).

5. 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.

6. 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.

7. Unit according to any one of the preceding claims, wherein the unit comprises, for each stage (2, 3) of the set of stages (50), at least one polarized electrical component (19, 23, 24, 39) having first and second electrical terminals (21, 22) coupled respectively to the first and second collectors (6 to 9) of the stage (2, 3).

8. Unit according to the preceding claim, in which the unit comprises, for each stage (2, 3) of the set of stages (50), at least two polarized electrical components (19, 23, 24, 39) each having first and second electrical terminals (21, 22) coupled respectively to the first and second collectors (6 to 9) of the stage (2, 3).

9. A unit according to any one of claims 1 to 6, 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 unit comprises at least one polarized electrical component (19, 23, 24, 39) having first and second electrical terminals (21, 22) coupled respectively to the first and second electrical terminals (51, 52) of the unit.

10. Unit according to any one of the preceding claims, wherein said at least one polarized electrical component (19, 23, 24, 39) is configured to operate in a passive manner that does not require an external command to operate.

11. Unit according to any one of the preceding claims, wherein said at least one polarized electrical component (19, 23, 24, 39) is a diode (25).

12. A unit according to any one of claims 1 to 10, wherein said at least one polarized electrical component (19, 23, 24, 39) 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 another current collector of the set of stages (50), and a third electrical terminal (29) electrically coupled to the first electrical terminal (22) of the thyristor (26).

13. Unit according to any one of claims 1 to 11, in which each polarized electrical component (19, 23, 24, 39) is a diode (25).

14. A unit according to any preceding claim, wherein said at least one polarized electrical component (19, 23, 24, 39) has a first electrical terminal (22) coupled to the second current collector (7, 9) of said at least one stage (2, 3) of the set of stages (50), and the unit comprises an electro-pyrotechnic switch (31) comprising first and second electrical terminals (55, 56) electrically coupled in parallel to said at least one stage (2, 3) of the set of stages (50), a normally open electrical conductor (32) between the first and second electrical terminals (55, 56) of the electro-pyrotechnic switch, a movable closing member (33) configured to close the electrical conductor (32), and a controlled actuator (34) electrically coupled in series between the second electrical terminal (21) of said at least one polarized electrical component (19, 23, 24, 39) and the first 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 close the electrical conductor (32) when the actuator (34) receives the current passing through said at least one polarized electrical component (19, 23, 24, 39)., 15. Unit according to any one of the preceding claims, comprising a control circuit (40) and in which 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 flows through said at least one polarized electrical component (19, 23, 24, 39).

16. 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, 24, 39), and a phototransistor (43) for converting the light energy emitted by the light-emitting diode (42) into a current (Is), the phototransistor (43) being electrically coupled to the control circuit (40).

17. Unit according to any one of the preceding claims, configured to provide an operating voltage (Vf) strictly greater than 100 V.

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