AUTONOMOUS ELECTRICAL ENERGY STORAGE UNIT WITH ELECTRONIC PROTECTION FOR VEHICLES

Abstract

The invention relates to a self-contained electrical energy storage unit (1), otherwise called a battery, having a negative external terminal (BX-) and a positive external terminal (BX+), the unit comprising a set of electrochemical cells (5), the set of cells having a negative internal terminal (BC-) and a positive internal terminal (BC+), the unit comprising at least one current sensor (4), a control unit (3), the unit comprising a main switch (2) interposed between the positive terminal (BC+) and the negative positive terminal (BX+), controlled by the control unit, the main switch being a semiconductor member, and optionally a foot isolation switch (6) interposed between the negative internal terminal (BC-) and the negative external terminal. Figure 1

Description

Title of the invention: AUTONOMOUS ELECTRICAL ENERGY STORAGE UNIT WITH ELECTRONIC PROTECTION FOR VEHICLE

[0001] The present invention relates to a self-contained electrical energy storage unit. In practice, this self-contained electrical energy storage unit is also called a self-contained electric battery.

[0002] Such an autonomous storage unit has a negative terminal and a positive terminal to which electrical consumers can generally be connected.

[0003] In certain life circumstances, charging equipment may also be connected to the negative and positive terminals, in order to recharge the autonomous storage unit. This may be an on-board charger (OBC) in the case of a vehicle, but other charging situations are also encompassed by the present invention.

[0004] In the context of the present invention, the focus is in particular on batteries for light electromobility vehicles. Of course, other types of vehicles are not excluded from the use of the batteries presented here.

[0005] Usually, these batteries comprise a set of electrochemical cells based on Lithium-Ion chemistry.

[0006] The autonomous storage unit of interest here is equipped with an electronic computer, also called here a control unit, and called in the jargon of the trade BMS (for 'Battery Management System').

[0007] In the electrical architectures of known vehicles, the on-board charger exchanges with the BMS computer to receive from the BMS what the possible charging power is. The charger then adapts the voltage level injected into the battery.

[0008] A dialogue between two computers is therefore required for the recharge to occur correctly. This implies that there is compatibility of the dialogue between the two computers, which turns out to be a limitation of flexibility in practice.

[0009] Thus there remains a need to propose new solutions to make the battery more independent of the vehicle architecture, and more flexible with regard to the different means and equipment of recharging.

[0010] To this end, the present invention proposes an autonomous electrical energy storage unit having a negative external terminal and a positive external terminal, the autonomous storage unit comprising a set of electrochemical cells, the set of cells having a negative internal terminal and a positive internal terminal, the autonomous storage unit comprising at least one current sensor, a control unit, the autonomous storage unit comprising a main switch interposed between the positive internal terminal and the positive external terminal, controlled by the control unit.

[0011] The autonomous storage unit is characterized in that the main switch is a semiconductor device, and the control unit is configured to control the main switch as a function of a current value delivered by the current sensor.

[0012] Advantageously, thanks to the current sensor and a modulated control (PWM or other) of the main switch, the control unit can adjust the electrical power entering and leaving the battery.

[0013] Thanks to the above provisions, whatever the configuration of the charger, recharging can be carried out while protecting the autonomous storage unit, even if the voltage and / or current transmitted by the charger are too high.

[0014] We can thus really speak of an autonomy function of the storage unit which adapts itself to all recharging sources.

[0015] It should be noted that, in addition to the charge regulation discussed above, the control unit can also protect the storage unit for excessively high output currents, without necessarily completely cutting off the output, i.e. by using modulated control to limit the current delivered by the battery.

[0016] The self-contained storage unit may be permanently installed in a vehicle, but given its self-contained nature, the unit may also be formed as an exchangeable energy reserve cartridge.

[0017] According to one embodiment, a foot isolation switch is further provided interposed between the negative internal terminal and the negative external terminal.

[0018] This foot isolation switch allows the battery to be isolated in the event that the main switch can no longer effectively interrupt the positive line, if battery isolation conditions are required.

[0019] It should be understood that in the absence of a foot isolation switch, the negative external terminal is connected directly to the negative internal terminal.

[0020] According to one embodiment, a wired monitoring circuit is provided, configured to control the foot isolation switch.

[0021] This wired circuit is independent of any software operation, and allows extremely rustic and reliable protection of the battery. Isolation by opening the foot isolation switch is obtained simply in wired logic as a function of a voltage at the terminals of the battery or even an image of the current flowing into or out of the battery.

[0022] According to one embodiment, the foot isolation switch is a semiconductor device. This solution proves to be economically relevant. The semiconductor switch conductors can be reliably opened while a significant current flows through it.

[0023] According to one embodiment, the foot isolation switch is controlled bistably, for example via a flip-flop. Thanks to such bistable control, it is possible to minimize the electrical consumption during nominal operation and / or in steady state.

[0024] According to an alternative embodiment, the foot isolation switch takes the form of a relay. Opening the relay contact generates galvanic isolation. This is a rustic solution with very good efficiency and reliability.

[0025] According to one embodiment, the main switch comprises at least one MOSFET transistor. This solution allows all-or-nothing controls and also, of course, modulated PWM-type controls, which will be discussed in detail later.

[0026] It is noted that it is not excluded to use other semiconductor solutions such as IGBTs.

[0027] According to one embodiment, the electrochemical cells are based on Lithium-Ion chemistry. This solution has very good compactness from the point of view of the stored energy in relation to the occupied volume. Other electrochemical couples are of course possible.

[0028] According to one embodiment, the autonomous storage unit may further comprise one or more protective fuses, and / or a voltage converter.

[0029] According to one embodiment, the autonomous storage unit may have a nominal voltage of between a few tens of volts and a few hundred volts. According to a particular example, the nominal voltage may be 48V.

[0030] The invention further relates to a method for protecting a self-contained electrical energy storage unit having a negative external terminal and a positive external terminal, the unit comprising a set of electrochemical cells, at least one control unit, a main semiconductor switch interposed between the positive external terminal and the set of electrochemical cells, the method comprising: - control the main switch by means of the control unit in a modulated manner with a variable duty cycle to ensure a pre-charging function for consumer circuits and a recharge regulation function.

[0031] According to one embodiment, the autonomous storage unit may further comprise a foot isolation switch interposed between the negative external terminal and the set of electrochemical cells, the method then providing for controlling, by means of a wired monitoring circuit, at least one opening of the foot isolation switch.

[0032] The invention further relates to a motor vehicle comprising an autonomous storage unit as described above.

[0033] The invention further relates to an electrical energy storage system comprising at least two autonomous storage units as described above, connected in parallel.

[0034] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: [Fig.l] is a schematic representation of an autonomous electrical energy storage unit according to a first exemplary embodiment of the invention; [Fig.2] is a schematic representation of an autonomous electrical energy storage unit according to a second exemplary embodiment; [Fig.3] illustrates a functional block diagram relating to the control unit; [Fig.4] schematically shows an electrical energy storage system, comprising three autonomous storage units, recharged in parallel by chargers using various energy sources.

[0035] In the various figures, the same references designate identical or similar elements. For reasons of clarity of the description, certain elements are not necessarily represented to scale.

[0036] We are interested here in an electrical energy storage battery referenced 1, also called here 'storage unit' or simply 'battery'. This unit comprises a set of electrochemical cells 5. According to one example, the electrochemical cells are based on Lithium-Ion chemistry. However, it should be noted that the invention covers all types of electrochemical couples possible for the cells of the battery. The number of electrochemical cells can be any; they are generally arranged in series.

[0037] The set of cells having a negative internal terminal BC- and a positive internal terminal BC+.

[0038] The autonomous storage unit comprises a positive external terminal BX+ and a negative external terminal BX-. These are the terminals accessible from outside the storage unit. According to a particular example, these are the only accessible terminals.

[0039] The electrical voltage on the negative external terminal BX- corresponds to the vehicle mass denoted V-. The electrical voltage which prevails on the positive external terminal BX+ is denoted V+.

[0040] According to the first embodiment, a foot isolation switch 6 is provided interposed between the negative internal terminal BC- and the negative external terminal BX-. The control logic applied to this switch will be seen later.

[0041] The unit comprises a current sensor 4. This may be a Hall effect current sensor. Other technological types of current sensors may also be suitable. It is noted that it is possible for the current sensor to be arranged on the line of the negative terminal of the battery.

[0042] The current sensor delivers a current value noted ii.

[0043] The current ii is measured in real time by the current sensor 4.

[0044] The unit comprises a control unit 3, (also identified and called BMS).

[0045] The control unit 3 is an electronic computer responsible for protecting the battery. The control unit 3 collects temperature information from at least some cells, voltage information at the terminals of each cell, and the total current ii that leaves or enters the battery.

[0046] The control unit 3 is electrically powered locally from all of the electrochemical cells.

[0047] The unit comprises a main switch 2 interposed between the positive internal terminal BC+ and the positive external terminal BX+.

[0048] The main switch 2 is controlled by the control unit via the control line 20.

[0049] Advantageously, the main switch 2 is a semiconductor device. It may be, for example, one or more MOSFET transistor components. Other IGBT type solutions are also not excluded.

[0050] A temperature sensor is provided placed on certain cells. A voltage measurement is provided at the terminals of each cell, this voltage being fed back to the control unit 3.

[0051] All of the sensors are connected to the control unit 3 via a bundle of conductors marked 35 in [Fig.l].

[0052] As illustrated in [Fig.3], the control unit 3 receives as input the external positive voltage V+, the current value ii measured by the current sensor 4, the voltage Vcell prevailing at the terminals of each electrochemical cell, the temperature Tcell of each of the cells on which a temperature sensor is installed.

[0053] Furthermore, the control unit 3 comprises in memory calibration tables 30 or mapping information which characterizes the normal operation of the electrochemical cells of the battery, in particular with respect to the maximum discharge current and the maximum recharge current, as a function of a plurality of parameters including in particular the voltage at the terminals and the temperature.

[0054] The control unit 3 can control the main switch 2 in all-or-nothing mode, i.e. OFF or ON, but also in pulsed / modulated cyclic control. [Fig. 3] illustrates a control modulated according to a signal with a variable opening duty cycle and fixed frequency known in the jargon of the trade under the term PWM.

[0055] The period of the control signal is noted TL. According to an exemplary embodiment, Tl has the value 1 millisecond, which corresponds to a control frequency of 1 kHz.

[0056] The modulation of the control makes it possible to limit the average current leaving the battery on the one hand, and on the other hand it also makes it possible to limit the incoming current during recharging.

[0057] The inventors noticed that a pulsed command to finish the recharge at a state of charge close to 100% was advantageous, better than an end of recharge at constant voltage.

[0058] According to an optional embodiment, the foot isolation switch 6 is a semiconductor member.

[0059] According to an alternative solution, the foot isolation switch takes the form of a relay.

[0060] According to an advantageous aspect, the control circuit of the foot isolation switch may be of the bistable type.

[0061] Still according to the first embodiment, a wired monitoring circuit 7 is provided, configured to control the foot isolation switch 6.

[0062] In the wired monitoring circuit 7, a voltage comparator 70 is provided, which makes it possible to trigger an action to isolate the battery by opening the foot isolation switch if the voltage on the V+ terminal becomes higher than a critical threshold and incidentally if current flows on the positive line.

[0063] A flip-flop 71 is provided to implement the bistable control of the foot isolation switch as already mentioned above.

[0064] Reset foot isolation switch 6

[0065] The autonomous storage unit comprises in the example illustrated a fuse 14, which forms a secondary safety device against a possible short circuit downstream of the autonomous storage unit 1.

[0066] The autonomous storage unit comprises in the illustrated example a voltage converter 9. In the illustrated example, the voltage converter 9, also called DC / DC converter, delivers a voltage of 12 volts.

[0067] The consumers present downstream of the battery have a fairly significant equivalent electrical capacity 16 which must be charged when the on-board network is switched on from 0.

[0068] A pre-charge function is provided for this purpose to limit the current draw on the battery. To this end, the control unit 3 controls the main switch 2 with an increasing opening duty cycle starting from a low value, where appropriate with a maximum outgoing current criterion ii. This regulation to manage the initial charge of the downstream capacitors 16 is a fairly short phase which lasts a few milliseconds or a few tens of milliseconds.

[0069] The autonomous storage unit 1 is notably recharged by a 10 CHG charger. The illustrated example shows a charger operating from the 220 volt network.

[0070] The unit comprises a protective casing 8. The protective casing forms a protective envelope with respect to the mechanical and physicochemical environment. Said envelope may have the qualified protection level of IP67.

[0071] The electrochemical cells 5, the control unit 3, the main switch 2, and when present, the foot isolation switch 6, are housed in the protective casing 8.

[0072] Still according to the first embodiment, the protective casing also houses the voltage converter 9. In this configuration, the autonomous storage unit 1 comprises a third terminal marked 19 corresponding to the output of the voltage converter 9.

[0073] The battery, otherwise known as an autonomous storage unit, can be installed on board electric or hybrid motor vehicles, or any type of small electromobility vehicle.

[0074] The vehicles in question may be private vehicles or utility vehicles, they may be road or non-road vehicles, for example a quad, a car without a license, etc.

[0075] According to the second embodiment illustrated in [Fig.2], the autonomous storage unit is devoid of a foot isolation switch. The negative external terminal BX- is connected directly to the negative internal terminal BC-.

[0076] The other elements of the second embodiment are identical or similar to those of the first embodiment and therefore not described again here.

[0077] According to an advantageous aspect, the autonomous electrical energy storage unit 1 can be presented as an exchangeable cartridge which can be recharged in specific equipment dedicated to recharging and which can be used on board a small electromobility type vehicle.

[0078] As illustrated in [Fig.4], several storage units 1A, 1B, 1C can be associated in parallel, either in a vehicle or in equipment of another nature, for example in recharging equipment. This produces a natural balancing, each autonomous storage unit regulates its own recharging, either from the charger or from neighboring unit(s).

[0079] It is noted that recharging can be done via a charger 10 using renewable energy such as photovoltaic panels 82 or wind turbines 84.

Claims

Claims

1. Autonomous electrical energy storage unit (1) having a negative external terminal (BX-) and a positive external terminal (BX+), the autonomous storage unit comprising a set of electrochemical cells (5), the set of cells having a negative internal terminal (BC-) and a positive internal terminal (BC+), the autonomous storage unit comprising at least one current sensor (4), a control unit (3, BMS), the autonomous storage unit comprising a main switch (2) interposed between the positive internal terminal (BC+) and the positive external terminal (BX+), controlled by the control unit, characterized in that the main switch (2) is a semiconductor member, and the control unit is configured to control the main switch as a function of a current value delivered by the current sensor.

2. Self-contained storage unit according to claim 1, characterized in that a foot isolation switch is further provided interposed between the negative internal terminal (BC-) and the negative external terminal (BX-).

3. Self-contained storage unit according to claim 2, characterized in that a wired monitoring circuit (7) is provided, configured to control the foot isolation switch (6).

4. Autonomous storage unit according to one of claims 2 to 3, characterized in that the foot isolation switch is a semiconductor member.

5. Autonomous storage unit according to one of claims 1 to 4, characterized in that the main switch (2) comprises at least one MOSFET transistor.

6. Autonomous storage unit according to one of claims 1 to 5, characterized in that the electrochemical cells (5) are based on Lithium-Ion chemistry.

7. Method for protecting an autonomous electrical energy storage unit having a negative external terminal (BX-) and a positive external terminal (BX+), the unit comprising a set of electrochemical cells, at least one control unit (3), a main semiconductor switch (2) interposed between the positive external terminal (BX+) and the set of electrochemical cells, the method comprising: - controlling by means of the control unit (3) the switch

8.

9.

10. main in a modulated manner with a variable duty cycle (PWM) to ensure a precharging function for consumer circuits and a recharge regulation function. Method according to claim 7, in which the autonomous storage unit further comprises a foot isolation switch (6) interposed between the negative external terminal (BX-) and the set of electrochemical cells, characterized in that the method provides for controlling, by means of a wired monitoring circuit (7), at least one opening of the foot isolation switch (6). Motor vehicle comprising an autonomous storage unit (1) according to any one of claims 1 to 6. Electrical energy storage system, comprising at least two autonomous storage units (1) according to any one of claims 1 to 6, connected in parallel.

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