FR3152888A1 - STORAGE DEVICE FOR BATTERY ACCUMULATOR MANAGEMENT SYSTEM AND BATTERY ACCUMULATOR MANAGEMENT SYSTEM EQUIPPED WITH SUCH A DEVICE - Google Patents

Abstract

The invention relates to a device (6) for storing a deep discharge state of a battery for a battery accumulator management system, said device (6) comprising at least one bistable relay (R) configured to assume a first position and a second position, said bistable relay (R) being configured to switch: – into the first position if a voltage value (V1) indicative of a deep discharge state of the battery is less than or equal to a first threshold value; – into the second position if a voltage value (V2) indicative of a deep discharge state of the battery is greater than a second threshold value; said bistable relay (R) being configured to regulate, depending on its position, the value of the charging current to said battery. Figure to be published with the abstract: [Fig. 2]

Description

STORAGE DEVICE FOR BATTERY ACCUMULATOR MANAGEMENT SYSTEM AND BATTERY ACCUMULATOR MANAGEMENT SYSTEM EQUIPPED WITH SUCH A DEVICE

The technical context of the present invention is that of electric batteries, and in particular batteries with high electric current, in particular a current greater than 50 A, and preferably greater than 500 A, for example for aeronautical and/or aerospace applications.

A battery generally comprises several battery modules forming a set which can also be connected to an external bus allowing data to be sent to a monitoring system, a system generally referred to as a battery accumulator management system (or “Battery Management System” in English).

The battery accumulator management system is notably configured to measure various physical quantities relating to the battery and to the battery modules, such as voltages, currents, temperatures, internal resistances, etc., but also includes protection circuits to prevent the battery from operating under abnormal operating conditions, conditions which may damage the battery and cause human and/or material damage.

Abnormal operating conditions are generally understood to mean: overvoltages, overcurrents, undervoltages, excessively high battery temperature, short circuits, etc., i.e. all parameters that do not correspond to a nominal operating range of the battery.

Battery management systems therefore include safety devices, such as a disconnecting device configured to cut the battery's electrical connections with the outside (and therefore electrically isolate it) in the event that these abnormal operating conditions occur.

Another problem with electric batteries is that they can be in a state of "deep discharge", i.e. when the battery is completely discharged, or charged to less than 10%, the cells or accumulators of the battery then have a very low voltage at their terminals, for example less than 1 Volt.

In this deep discharge state, there is a risk of reduction in the battery capacity, but also of degradation of its electrodes, and a risk linked to the fact that the battery could catch fire, or even explode, when it is recharged with too high a charging current and/or in unsuitable temperature conditions (for example below 10°C or above 60°C).

Thus, current batteries, and more particularly their accumulator management system, are configured to store data, physical quantities, etc., in volatile (or live or non-permanent) memories, data indicative of a physical or electrical state of the battery, but this data is generally lost when the battery is completely discharged and is no longer able to supply electricity to the memory(s) of said accumulator management system intended for storing this state.

This loss of information is therefore dangerous, because reactivating and recharging a battery in a state of deep discharge requires special precautions, especially since a battery can discharge unexpectedly, for example following the failure to disconnect an electrical device, and there is therefore no way of knowing if the battery is in a state of deep discharge.

The present invention thus proposes to remedy at least one of the aforementioned drawbacks by proposing a new type of device for memorizing a deep discharge state of a battery for a battery accumulator management system,
said device comprising at least one bistable relay configured to take a first position and a second position, said bistable relay being configured to switch:
– in the first position if a voltage value indicative of a deep discharge state of the battery is less than or equal to a first threshold value;
– in the second position if a voltage value indicative of a deep discharge state of the battery is greater than a second threshold value;
said bistable relay being configured to regulate, depending on its position, the value of the charging current to said battery.

Such a storage device allows the storage via the bistable relay, and in particular its position, of a deep discharge state of the battery, permanent and modifiable (or rewritable) storage, this independently of the power supply of said bistable relay. In addition, said bistable relay advantageously allows the battery charging current to be regulated, for example to limit the value of the charging current as long as the battery can be considered in a deep discharge state.
This type of storage device also has the advantage of being robust, inexpensive, energy-efficient and suitable for aeronautical or aerospace applications.

According to a possible characteristic, said bistable relay is configured to maintain its position, therefore the first position or the second position, in the absence of electrical power, for example when the battery is in a discharged state and can no longer supply power to the battery accumulator management system, and therefore said bistable relay.
The position of the bistable relay is advantageously retained regardless of the state of the battery and/or the battery accumulator management system (no loss of state therefore), thus making it possible to retain over time information relating to a state of the battery, such as here a deep discharge state of the battery.

According to another possible characteristic, said device comprises an H-bridge assembly configured to control the polarity at the terminals of the bistable relay so as to switch said bistable relay from the first position to the second position and vice versa.
An H-bridge assembly is a simple assembly allowing easy and efficient control of the bistable relay, and in particular the switching of said relay.

According to another possible feature, said H-bridge assembly comprises four switching elements.
Said switching elements, such as switches, allow, by their opening and closing, said relay to be switched from a first position to a second position and vice versa.

According to another possible characteristic, said switching elements are transistors.
Said switching elements are advantageously transistors, for example field effect transistors, operating for example in linear mode, and acting as a switch, the opening and closing of which is controlled by a voltage.

According to another possible characteristic, said transistors are MOSFET type transistors which each have a gate, a source and a drain. Said transistors are for example N-channel and/or P-channel MOSFET transistors.

According to another possible characteristic, said device comprises four Schottky diodes, each associated with one of said transistors acting as a switching element.
Each of the Schottky diodes is therefore connected to the drain-source terminals of one of said transistors, in particular to play the role of freewheel diode (and therefore protect the transistor against destructive overvoltages).
More specifically, Schottky diodes have a cathode and an anode, with the cathode of the Schottky diode connected to the source of the transistor, and the anode of the Schottky diode connected to the drain of the transistor.

According to another possible characteristic, said device comprises at least two logic gates respectively supplied at input by a voltage value indicative of a deep discharge state of the battery, each of said logic gates being connected to at least one switching element.
Said logic gates are advantageously connected to the gate of a transistor acting as a switching element, and are therefore configured to open or close said switch depending on their input voltage value. Said logic gates also have the advantage of having very low static electrical consumption (of the order of a few microwatts).

According to another possible characteristic, one of said logic gates is configured to allow the closing of at least one switching element when the voltage value indicative of a deep discharge state of the battery is less than or equal to a first threshold value and to switch the relay into the first position, while the other logic gate is configured to allow the closing of at least one other switching element when the voltage value indicative of a deep discharge state of the battery is greater than a second threshold value and to switch the relay into the second position.
The first and second threshold values may be different or identical, for example for six 3.3 V cells connected in series, it is considered that there is a deep discharge when the voltage across this set of cells is less than or equal to 14 V, while the deep discharge output voltage is greater than or equal to 13.5 V.

According to another possible characteristic, said switching elements are closed when said logic gates are supplied at the input with voltage values respectively less than or equal to the first threshold value and greater than the second threshold value.

According to another possible characteristic, in the first position, said bistable relay limits the battery charging current to a predetermined current value, for example a charging current value of approximately 0.5 A.
Advantageously, the device according to the invention is configured to limit the value of the charging current intended to charge said battery, if the latter is in a deep discharge state, as soon as the battery has left this deep discharge state, the relay switches to the second position, and there is then no longer any limitation of the charging current (subject to the physical properties of the electronic components).

The invention also relates to a battery accumulator management system, characterized in that said system comprises a locking control device as defined above.

The invention further relates to an electric battery, advantageously for aeronautical applications, characterized in that said battery comprises a battery accumulator management system as defined above.

Other characteristics and advantages of the invention will become apparent from the following description on the one hand, and from several examples of embodiment given for informational and non-limiting purposes with reference to the attached schematic drawings on the other hand, in which:
- there FIG. 1 illustrates a very schematic and side view of an electric battery according to the invention equipped with a battery accumulator management system;
- there FIG. 2 illustrates a schematic view of a device for storing a deep discharge state of a battery intended to be integrated into the battery management system FIG. 1 .

Of course, the features, variants and different embodiments of the invention may be combined with each other, in various combinations, provided that they are not incompatible or mutually exclusive. In particular, variants of the invention may be imagined comprising only a selection of features described below in isolation from the other features described, if this selection of features is sufficient to confer a technical advantage or to differentiate the invention from the prior art.

In particular, all the variants and embodiments described can be combined with each other if there is no technical obstacle to this combination. Furthermore, in the various figures, the elements common to several figures retain the same reference.

There FIG. 1 illustrates a very schematic and functional view of an electric battery 1, for example a lithium-ion battery advantageously intended for aeronautical or aerospace applications, which comprises battery accumulators 2, a battery accumulator management system 3 connected to said accumulators, system 3 also designated by the English acronym “BMS” for “Battery Management System”, as well as a communication circuit 4 connected to said management system 3 and configured to exchange information with the outside (information relating to the environment, the battery, the aircraft, etc.)

Said management system 3 is generally integrated into said battery 1, in order to monitor the various physical or electrical quantities characteristic of a battery 1, and/or of its accumulators 2, for example a voltage, an internal resistance, etc.

Said management system 3 is also configured to prevent the operation of the battery 1 outside its nominal operating range, that is to say that the system is configured to detect abnormal operating conditions of the battery (or its modules), such as overcurrent, overvoltage (in particular when charging it), undervoltage (in particular when discharging it), overheating, etc.

Such a system 3 may also comprise a locking circuit (not shown) configured to prevent the use of the battery 1, and therefore its operation, in particular if an abnormal operating condition has previously occurred.

There FIG. 2 thus illustrates a very schematic view of a device 6 for storing a deep discharge state of the battery according to the invention intended to be integrated into said battery accumulator management system 3.

Said storage device 6 thus comprises at least one bistable relay R configured to take a first position and a second position, said bistable relay R being configured to switch:
– in the first position if a voltage value V ₁ indicative of a deep discharge state of battery 1 is less than or equal to a first threshold value V _S1 ;
– in the second position if a voltage value V ₂ indicative of a deep discharge state of battery 1 is greater than a second threshold value V _{S 2} .

It will be noted that the first V _S1 and the second V _S2 threshold value may be different or identical. In addition, said bistable relay R is configured to regulate, depending on its position, the value of the charging current to said battery 1.

Furthermore, said device 6 advantageously comprises an H-bridge assembly, assembly referenced 8, configured to control the polarity at the terminals of the bistable relay R so as to switch said bistable relay R from the first position to the second position and vice versa.

More particularly, said assembly 8 comprises at least:
– a first branch 81 and a second branch 82 connected in parallel to each other;
– four switching elements T ₁ to T ₄ , respectively designated first, second, third and fourth transistor, these acting as a switch, the opening and closing of which (or on/off state) are controlled by a voltage;
– four Schottky diodes D ₁ to D ₄ , respectively designated first, second, third and fourth diode, each being connected to the terminals of one of said transistors T ₁ to T ₄ .

It should be noted that these transistors are, for example, MOSFET type field effect transistors (English acronym for “Metal Oxide Semiconductor Field Effect Transistor”, i.e. an insulated gate field effect transistor).

The first branch 81 thus comprises the first transistor T ₁ and the fourth transistor T ₄ . The first and fourth transistors T ₁ and T ₄ are connected in series between two contact points N ₁ and N ₂ connected respectively to the battery (or to an electronic card of the system 3) and to an electrical ground G. The first and fourth transistors T ₁ and T ₄ of the first branch 81 are further connected to each other at a first midpoint M ₁ of the H-bridge assembly 8.

The second branch 82 comprises the second transistor T ₂ and the third transistor T ₃ . The second and third transistors T ₂ and T ₃ are connected in series between two contact points N ₁ and N ₂ connected respectively to the battery (or to an electronic card of the system 3) and to an electrical ground G. The second and third transistors T ₂ and T ₃ of the second branch 82 are further connected to each other at a second midpoint M ₂ of the H-bridge assembly 8.

Said bistable relay R is connected to the first and second midpoints M ₁ and M ₂ of the first and second branches 81 and 82 of the H-bridge 8. Furthermore, each of said transistors T ₁ to T ₄ comprises (or has) a gate, a source and a drain. Furthermore, each of said Schottky diodes D ₁ to D ₄ comprises (or has) a cathode and an anode.

Thus, the respective sources of the second and fourth transistors T ₂ and T ₄ are connected to the contact point N ₂ which is connected to the electrical ground G, while the drains of the second and fourth transistors T ₂ and T ₄ are connected respectively to the second and first midpoint M ₂ and M ₁ .

Furthermore, the respective sources of the first and third transistors T ₁ and T ₃ are connected respectively to the first and second midpoint M ₁ and M ₂ , while the drains of the first and third transistors T ₁ and T ₃ are connected to the contact point N ₁ connected to the battery 1.

The first, second, third and fourth Schottky diodes D ₁ to D ₄ are thus connected respectively to the terminals of the first, second, third and fourth transistor T ₁ to T ₄ , respectively the anode of the diode D ₁ , D ₂ , D ₃ or D ₄ being connected to the source of the transistor T ₁ , T ₂ , T ₃ or T ₄ , and the cathode of the diode D ₁ , D ₂ , D ₃ or D ₄ being connected to the drain of the transistor T ₁ , T ₂ , T ₃ or T ₄ .

Each of the Schottky diodes D ₁ to D ₄ is therefore associated with one of said transistors T ₁ , T ₂ , T ₃ or T ₄ acting as a switching element, in order to play the role of freewheel diode.

Said device 6 further comprises at least two logic gates LG ₁ and LG ₂ , respectively designated first and second logic gate, supplied respectively at input by a voltage V ₁ and V ₂ indicative of a state of the battery 1, in particular whether the latter has a deep discharge state or not, each of said logic gates being connected to at least one transistor T ₁ or T ₂ .

More particularly, the first voltage V ₁ indicative of a state of the battery 1 supplies the first logic gate LG ₁ , at its input, and the second transistor T ₂ , at its gate. While the second voltage V ₂ indicative of a state of the battery 1 supplies the second logic gate LG ₂ , at its input, and the fourth transistor T ₄ , at its gate.

The outputs of the first and second logic gates LG ₁ and LG ₂ are, for their part, respectively connected to the gate of the first transistor T ₁ and to the gate of the third transistor T ₃ . Said logic gates LG ₁ and LG ₂ are therefore configured to open or close respectively the first and third transistors T ₁ and T ₃ acting here as a switching element (or switch) according to their value of the input voltages V ₁ and V ₂ .

LG logic gates₁and LG₂are for example logic gates of the inverter type configured to respectively supply the gate of the first transistor T₁and third transistor T₃which are advantageously P-channel type transistors. Thus, LG logic gates₁and LG₂are configured to power the gate of transistors T₁And T₃with a positive voltage, for example of about 1V, to make said transistors conductive (i.e. act as closed switches). LG logic gates₁and LG₂deliver a positive voltage at the output, only when the voltage at their respective input indicates a deep discharge state of the battery, or a deep discharge output.

It should also be noted that device 6 includes:
– at least four capacitors C ₁ to C ₄ , respectively designated first, second, third and fourth capacitor;
– at least two resistors R ₁ and R ₂ , respectively designated first and second resistor.

The first capacitor C ₁ is connected, on the one hand, to the output of the first logic gate LG ₁ and to the gate of the first transistor T ₁ , and on the other hand, to ground G. The third capacitor C ₃ is, for its part, connected, on the one hand, to the output of the second logic gate LG ₂ and to the gate of the third transistor T ₃ , and on the other hand, to ground G. These capacitors C ₁ and C ₃ make it possible to limit, or even avoid, a too rapid rise in the voltage at the gate of the transistor, respectively of the first and third transistors T ₁ and T ₃ .

The first resistor R ₁ and the second capacitor C ₂ are, for their part, mounted to form a first parallel RC circuit connected, on the one hand, to the gate of the second transistor T ₂ and, on the other hand, to the ground G. The second resistor R ₂ and the fourth capacitor C ₄ are, for their part, mounted to form a second parallel RC circuit connected, on the one hand, to the gate of the fourth transistor T ₄ and, on the other hand, to the ground G.

The first and second parallel RC circuits are configured to limit the occurrence of overvoltage at the gate of the transistor, respectively the second and fourth transistors T ₂ and T ₄ , but also to allow the transient closing of the transistor T ₂ or T ₄ when the voltage value V ₁ or V ₂ is lower or higher than predetermined values. More particularly, the first and second resistors R ₁ and R ₂ allow in particular the closing of the second and fourth transistors T ₂ and T ₄ respectively. While the second and fourth capacitors C ₂ and C ₄ make it possible to dampen, or even avoid, the occurrence of oscillation of the voltage at the gate of the transistor T ₂ and T ₄ .

Thus, when the voltage V ₁ is less than or equal to a threshold value V _S1 , the first logic gate LG ₁ is configured to control the closing, or turning on, of the first and second transistors T ₁ and T ₂ (the third and fourth transistors T ₃ and T ₄ being open or non-conducting), this causing the bistable relay R to switch to the first position.

The switching of relay R to the first position occurs when the voltage value V ₁ is less than or equal to a predetermined value (for example the first threshold value V _S1 ), a predetermined value which is indicative that said battery 1 is in a state of deep discharge.

Furthermore, when the voltage V ₂ is greater than a threshold value V _{S 2} , the second logic gate LG ₂ is configured to control the closing, or turning on, of the third and fourth transistors T ₃ and T ₄ (the first and second transistors T ₃ and T ₄ being open or non-conducting), this causing the bistable relay R to switch to the second position.

The switching of relay R into the second position occurs when the voltage value V ₂ is greater than a predetermined value (for example the second threshold value V _{S 2} ), a predetermined value indicating that said battery 1 is not or no longer in a state of deep discharge.

It will also be noted that when these conditions on the voltage values V ₁ and V ₂ which supply the H-bridge assembly 6 are not respected, the different transistors T ₁ to T ₄ are open, that is to say not conducting, and that there can be no switching of said relay R from one position to another. Furthermore, in the absence of electrical power supply, relay R is in a static state, the last position in which relay R is switched is retained until said relay R is supplied in one of the suitable ways described above.

Furthermore, said relay R is advantageously configured to limit the charging current of the battery 1 to a predetermined current value, for example less than or equal to 0.5 A, when said relay R is in the first position. However, when said relay R is in the second position, said battery 1 can be recharged via its power terminals, therefore at high current values.

Claims (10)

Device (6) for storing a deep discharge state of a battery for a battery accumulator management system,
said device (6) comprising at least one bistable relay (R) configured to take a first position and a second position, said bistable relay (R) being configured to switch:
– in the first position if a voltage value (V ₁ ) indicative of a deep discharge state of the battery is less than or equal to a first threshold value (V _S1 );
– in the second position if a voltage value (V ₂ ) indicative of a deep discharge state of the battery is greater than a second threshold value (V _{S 2} );
said bistable relay (R) being configured to regulate, depending on its position, the value of the charging current to said battery. Device (6) according to the preceding claim, characterized in that said device (6) comprises an H-bridge assembly (8) configured to control the polarity at the terminals of the bistable relay (R) so as to switch said bistable relay (R) from the first position to the second position and vice versa. Device (6) according to the preceding claim, characterized in that said H-bridge assembly (8) comprises four switching elements (T ₁ -T ₄ ). Device (6) according to the preceding claim, characterized in that said switching elements (T ₁ -T ₄ ) are transistors. Device (6) according to claim 3 or 4, characterized in that said device comprises at least two logic gates (LG ₁ , LG ₂ ) respectively supplied at input by a voltage value indicative of a deep discharge state of the battery, each of said logic gates (LG ₁ , LG ₂ ) being connected to at least one switching element (T ₁ , T ₃ ). Device (6) according to the preceding claim, characterized in that one of said logic gates (LG ₁ ) is configured to close at least one switching element (T ₁ ) when the voltage value (V ₁ ) indicative of a deep battery discharge state is less than or equal to a threshold value (V _S1 ) and to switch the relay (R) into the first position, while the other logic gate (LG ₂ ) is configured to close another switching element (T ₃ ) when the voltage value (V ₂ ) indicative of a deep battery discharge state is greater than a threshold value (V _S1 ) and to switch the relay into the second position. Device (6) according to claim 5 or 6, characterized in that said switching elements (T ₁ -T ₄ ) are closed when said logic gates (LG ₁ , LG ₂ ) are supplied at the input with voltage values (V ₁ , V ₂ ) respectively less than or equal to the first threshold value and greater than the second threshold value (V _S1 , V _S2 ). Device (6) according to any one of the preceding claims, characterized in that, in the first position, said bistable relay (R) limits the battery charging current to a predetermined current value. Battery accumulator management system (3), characterized in that said system (3) comprises a device (6) for storing a deep discharge state of the battery according to any one of the preceding claims. Electric battery (1), characterized in that said battery (1) comprises a management system (3) of the battery accumulators according to the preceding claim.