BATTERY MANAGEMENT SYSTEM AND METHOD FOR EQUALIZING CHARGE OF ACCUMULATOR CELLS OF A BATTERY - Patent application

Abstract

The management system (1) for managing a battery (2) of accumulator cells of an electric vehicle comprises a plurality of secondary controllers (7) respectively coupled to a plurality of accumulator cells (10) of the battery (2) and a primary controller (6) configured to determine a time period for equalizing the charges of the accumulator cells (10) when the management system (1) is in an active mode, the management system (1) comprising an inactive mode in which the time period for which the charges are equalized is determined solely by the secondary controller (7).

Description

Summary of the Invention

[0001] Technical Field The present invention generally relates to a system for managing an accumulator battery.

[0002] In particular, the present invention relates to a system for wireless management of an accumulator battery of an electric vehicle.

[0003] Background technology Electric vehicles, such as motor vehicles, include a traction accumulator battery, which is a high-voltage battery that powers the vehicle's electric motor, and a service battery, which is a low-voltage battery common to any vehicle, typically 12V or 14V, intended to power other functions, such as various on-board equipment.

[0004] An electric vehicle traction battery comprises a number of accumulators, also called cells. Typically, an electric motor vehicle battery comprises 96 or more accumulators grouped together in eight accumulator nodes. For example, the accumulators in an electric or hybrid vehicle are li-ion accumulators.

[0005] In order to optimize the life and maintenance of the traction battery and its performance level, a system for managing the accumulator battery is used to manage the equalization of the charge of the accumulators of the battery by discharging the most charged accumulator into a resistor, the aim being to have all of the accumulators at the same charge level.

[0006] The accumulator battery management system generally comprises a master controller powered by the vehicle's low-voltage battery and a number of slave controllers, each of which is coupled to a node of the number of accumulators that it guarantees its power supply, the master controller comprising a computer that determines the equalization period to be applied by each slave controller to the node to which it is coupled in order to equalize the charge of the accumulators of the battery.

[0007] To limit overheating of the resistors, the power dissipated is reduced and the equalization time is extended. To increase this time, it is a known practice to periodically wake up the system to restart the equalization of the accumulators. Current management systems therefore comprise an active mode and an inactive mode. The active mode generally corresponds to switching-on the vehicle and the inactive mode corresponds to switching-off the vehicle.

[0008] Document WO2019 / 017595 describes a management system comprising a plurality of slave controllers, which are configured to operate in active and inactive modes by using energy provided by the accumulator nodes to which the plurality of slave controllers are coupled. In the active mode, the slave controllers wirelessly transmit detection signals indicative of the state of the accumulator nodes to which the slave controllers are coupled, and the master controller wirelessly transmits control signals including an equalization period indicative of the scan period and scan time required for the slave controllers to discharge the accumulator nodes to which the slave controllers are coupled.

[0009] In general, the operation of the system is the same in active and inactive modes. In the inactive mode, the master controller sends signals to the slave controller, but at a lower frequency. In the inactive mode, the low-voltage battery thereby reduces the autonomy of the low-voltage battery to power the master controller.

[0010] The object of the present invention is therefore to propose a system for managing the traction accumulator battery of an electric vehicle, which comprises a non-active mode that does not cause discharging of the low-voltage battery without losing efficiency, and which alleviates the above-mentioned drawbacks.

[0011] The subject of the present invention is therefore a system for managing an accumulator battery of an electric vehicle, comprising a number of slave controllers respectively coupled to a number of accumulators of the battery, and a master controller configured to determine a period for equalizing the charge of the accumulators in an active mode of the management system, the management system having an inactive mode in which the charge equalization period is determined exclusively by the slave controllers.

[0012] Advantageously, during the inactive mode, each slave controller determines a period of time for equalizing the multiple accumulators to which it is coupled.

[0013] Advantageously, the master controller is powered by a low voltage battery and the slave controller is powered by the traction battery.

[0014] Preferentially, the master controller and the slave controllers use wireless communication means.

[0015] The subject of the invention is also a method for equalizing the charge of each of the accumulators of an accumulator battery of an electric vehicle, which can be implemented by a management system defined above.

[0016] Advantageously, the master controller communicates, in active mode, the current circulating in the battery to the slave controller, and the method comprises, in inactive mode, the following steps: a slave controller becoming a slave master controller; - a slave-master controller requesting the other slave controllers to transmit the minimum voltage among their multiple accumulators; - the slave master controller sending to each of the other slave controllers a minimum battery voltage from among the minimum voltages of the plurality of accumulators of each slave controller; - each slave controller determining an equalization need and an equalization period for its plurality of accumulators; Includes.

[0017] Preferentially, the method is implemented periodically at a very low frequency in a non-active mode.

[0018] Advantageously, the step of determining the need for equalisation comprises determining, by said slave controller, an indicator of the state of a plurality of accumulators.

[0019] Preferentially, the status indicators include the battery's state of health and state of charge.

[0020] Advantageously, each time the method is implemented the slave controller which becomes the slave master controller changes.

[0021] Thus, the charges in the accumulators associated with each slave controller remain equalized during the inactive mode.

[0022] The subject of the invention is also an electric vehicle comprising a traction battery, a low-voltage battery and a traction battery management system as defined above, this system being capable of implementing the method previously defined.

[0023] Advantageously, the management system comprises a master controller powered by the vehicle's low voltage battery and a slave controller powered by the traction battery.

[0024] Preferentially, the active mode corresponds to switching the vehicle on and the inactive mode corresponds to switching the vehicle off.

[0025] Other objects, features and advantages of the present invention will become apparent on reading the following description, given purely by way of non-limiting example and with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0026] [Figure 1] 1 shows a schematic diagram of a management system according to the invention, powered by the battery of an electric vehicle; [Diagram 2] FIG. 2 shows a schematic topology of the management system of FIG. 1 in active mode. [Diagram 3] FIG. 2 shows a schematic time organization of exchanges in active mode of the management system according to FIG. 1 in active mode. [Figure 4] FIG. 2 shows a schematic diagram of the time organization of exchanges in the inactive mode of a management system according to the state of the art; [Diagram 5] FIG. 2 shows a schematic topology of the management system of FIG. 1 in an inactive mode. [Figure 6] FIG. 2 shows a schematic diagram of the time organization of exchanges in the inactive mode of the management system according to the invention; [Figure 7] FIG. 2 shows a schematic diagram of an equalization method according to the invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] FIG. 1 shows diagrammatically a system 1 for managing an accumulator battery 2 according to the invention.

[0028] The accumulator battery 2 is an accumulator battery of an electric vehicle, for example an electric drive motor vehicle.

[0029] More specifically, the accumulator battery 2 is a traction battery of an electric vehicle, i.e. the battery that powers the electric motor of the electric vehicle. In particular, the traction battery 2 is a high-voltage battery, commonly referred to as a battery pack.

[0030] In addition to the traction battery 2 the electric vehicle comprises a low-voltage battery 3 .

[0031] The low voltage battery 3 is a conventional battery present in all vehicles with electric, internal combustion or hybrid motors, powering the various on-board equipment and is also called the service battery. The low voltage battery 3 is typically a 12V battery.

[0032] The electric vehicle comprises a BCM 4, BCM being the acronym for Body Control Module, a standard name for an on-board computer that controls the vehicle's electronic accessories, such as air regulation or central locking. The electric vehicle further comprises a supervisor of the powertrain 5, which is controlled by the BCM 4.

[0033] The management system 1 includes a master controller 6 and a plurality of slave controllers 7 .

[0034] The powertrain supervisor 5 controls the power-up of the master controller 6 .

[0035] The BCM 4, supervisor 5 and master controller 6 are powered by a low voltage battery 3 via a CAN bus 8, and the multiple slave controllers 7 are powered by the traction battery 2.

[0036] The management system 1 comprises an active mode corresponding to switching on the vehicle and an inactive mode corresponding to switching off the vehicle. The management system 1 is capable of switching between the active and inactive modes upon the occurrence of a triggering event. For example, a triggering event may be the stopping of the vehicle at the end of use, i.e. switching off the vehicle by the user, which causes a switchover from the active to the inactive mode. Another triggering event may be the occurrence of an end of charging of the traction battery 2 of the vehicle.

[0037] FIG. 2 shows the topology of the management system 1 in active mode.

[0038] The topology of the management system 1 in active mode is a star with a central gateway 9 coupled to the master controller 6 by a CAN bus 8 and powered by a low voltage battery 3 .

[0039] An assembly comprising a master controller 6 and a central gateway 9 communicates wirelessly with the slave controllers 7 .

[0040] The traction battery 2 comprises a set of accumulators 10 grouped together into a number of nodes 11. Each slave controller 7 is coupled to a number of accumulators 10 that form a node 11.

[0041] For example, the traction battery 2 comprises 96 or 100 accumulators grouped together in 12 nodes of 8 accumulators.

[0042] Each slave controller 7 communicates only with the assembly that comprises the gateway 9 and the master controller 6 .

[0043] In the active mode, the master controller 6 is configured to determine equalization periods for the charging of the accumulators 10. More specifically, the master controller 6 uses measurements of data such as voltage or temperature at the accumulators 10 to calculate condition indicators and infers therefrom an equalization period 10 to be applied for each accumulator 10 such as to equalize all of the charges of the accumulators 10 of the traction battery 2.

[0044] More specifically, an equalization period aimed at equalizing an accumulator 10 is applied by the slave controller 7 to this accumulator 10 to which it is coupled.

[0045] Figure 3 shows the timeline of exchanges between the controllers of the management system 1 in active mode, the x-axis being the time axis.

[0046] In active mode, the exchange is continuous and with a given periodicity P1, for example 100 ms. The periodicity P1 of the exchange is divided into several time slots, typically 3 ms, for example of equal duration. The synchronization is performed by sending an initial beacon 6a emitted by the master controller 6 via the gateway 9 to all of the slave controllers 7. According to this initial beacon 6a, each slot is dedicated to sending information to the assembly comprising the gateway 9 and the master controller 6. This information is sent in beacons 7a, 7b, etc. by the slave controllers 7 and includes measurements of the voltage and of the temperature of the accumulator to which the slave controller 7 is coupled. Each slave controller 7 thus knows the slot in which it has to send its information.

[0047] In parallel, the master controller 6 receives information from each slave controller 7 and determines an equalization period for each accumulator 10 of the battery 2. This equalization period is determined in particular by calculation of state indicators relating to the accumulator 10 and battery 2 in question. These state indicators comprise SOH and SOC, acronyms for "State Of Health" and "State Of Charge", respectively, which specify the state of health and state of charge of the battery 2.

[0048] After determining the equalization period for an accumulator 10, the master controller 6 sends this period to the slave controller 7 to which the accumulator 10 is coupled. This sending is not shown in Figure 3. The slave controller 7 then applies this equalization period to the accumulator 10 in question.

[0049] Thus, the charges of the different accumulators 10 of the traction battery 2 are equalized during the active mode.

[0050] The operation of the management system 1 in active mode is similar to the operation of state of the art management systems in active mode.

[0051] In the example shown in FIG. 3, the traction battery 2 comprises 12 nodes of accumulators 10, the period P1 is 100 ms and the slots have a duration equal to 3 ms.

[0052] Figure 4 shows the chronology of exchanges between the controllers of a state-of-the-art management system in inactive mode, where the X-axis represents the time axis.

[0053] State of the art management systems, in inactive mode, maintain the topology shown in FIG.

[0054] In the inactive mode of the state of the art management system, the periodicity of the exchange is extended, for example, to a duration P2 of 300 milliseconds. Furthermore, the exchange comprises only one initial synchronization beacon 6a sent by the master controller 6 to all of the slave controllers 7. The slave controllers 7 do not send any information unless the beacon 6a comprises a wake-up command. On the other hand, when the beacon 6a comprises a wake-up command, the state of the art management system performs an exchange similar to that of the active mode, even if the vehicle is switched off. Generally, during the inactive mode, the emitted beacon 6a does not comprise a wake-up command for several hours. For example, a wake-up command may occur every 8 hours.

[0055] The inactive mode therefore makes it possible to prolong the equalization of the charges of the accumulators, thereby limiting overheating of the resistors into which the accumulators are discharged according to their equalization period.

[0056] Nevertheless, this inactive mode according to the state of the art requires keeping the gateway 9 on to send the beacon 6a and periodically waking up the master controller 6. To wake up the master controller 6, the BCM 4 must be started, which wakes up the supervisor 5 which wakes up the master controller 6. Since the BCM 4, the supervisor 5 and the master controller 6 are powered by the low-voltage battery 3, an excessive draw of the autonomy of this low-voltage battery 3 is induced in the inactive mode.

[0057] FIG. 5 shows the topology of a management system 1 according to the invention in inactive mode.

[0058] More specifically, when the management system 1 switches from an active mode to an inactive mode, its topology is changed from the topology shown in FIG. 2 to the topology shown in FIG.

[0059] In the inactive mode, the master controller 6 is no longer the coordinator of the network formed by the controllers. In fact, one of the slave controllers 7 becomes the coordinator of the network and is therefore charged with organizing the exchanges in the management system 1. In the following, this slave controller will be called the slave master controller 12.

[0060] Preferentially, the slave controller 7 selected to become the slave master controller 12 in the inactive mode is chosen according to the location of the slave controller 7 in the battery pack 2. More specifically, it is the slave controller 7 coupled to the central node 11.

[0061] Alternatively, the role of the slave master 12 may change periodically between the slave controllers 7. More specifically, in each period of the implementation of the method, a different slave controller 7 may become the slave master controller 12 and send a synchronization beacon to the other slave controllers 7. Similarly, it is possible that each slave controller 7 has acted once as a slave master controller 12 before a slave controller 7 becomes the master slave controller 12 for the second time. More comprehensively, the slave controllers 7 that become the slave master controllers 12 may be designated in such a way that each slave controller becomes a slave master controller successively in the course of the periodic implementation of the method and each slave controller 7 becomes a slave master controller 12 an equal number of times in the inactive mode. This allows no inequality between the charging of the accumulators of the different slave controllers 7 and all slave controllers 7 to have the same energy consumption in the inactive mode. Thus, the equalization of the batteries is not affected.

[0062] FIG. 6 shows the time organization of exchanges between the controllers of the management system 1 in the inactive mode, and FIG. 7 shows a method for equalizing the charge of each of the accumulators 10 of the traction battery 2 that can be implemented by the management system 1.

[0063] The equalization method is implemented by the management system 1 at a very low frequency, for example in frames with a periodicity P3 of 10 minutes, since in the inactive mode the equalization needs change very slowly. In this way, the use of the traction battery 2 is economical in the inactive mode.

[0064] In a first step 13, the slave controller 7 becomes the slave master controller 12. The term "slave master controller" means that the slave master controller is one of the slave controllers 7 that becomes the coordinator of the network and of the equalization in the inactive mode, this role being played by the master controller 6 in the active mode. Thus, in the inactive mode, the slave controller 7 does not communicate with the master controller 6, but with the slave master controller 12, and conversely, the master controller 6 does not communicate with the slave controller 7, but it is the slave master controller 12 that communicates with the slave controller 7.

[0065] In a second step 14 , the slave master controller 12 asks the other slave controllers 7 to transmit the minimum voltage among their multiple accumulators 10 .

[0066] More specifically, the slave master controller 12 sends an initial beacon 15 to all of the slave controllers 7 to determine voltage measurements of the multiple accumulators 10 to which the slave controllers 7 are coupled and to send the minimum voltage of these measured voltages to the slave master controller 12.

[0067] Each slave controller 7 of the management system is equipped with computers and sensors that enable each slave controller 7 to perform such operations.

[0068] In a third step 16 , the slave master controller 12 sends to each of the other slave controllers 7 the minimum voltage of the traction battery 2 from among the minimum voltages of the multiple accumulators of each slave controller 7 .

[0069] More specifically, in step 14, the slave master controller 12 receives all of the minimum voltages 17 of each of the nodes of the accumulators 10 coupled to the slave controllers 7, determines the minimum of these received voltages and returns this minimum value in a beacon 18 to all of the slave controllers 7. In the time organization shown in Figure 6, the step of sending the minimum voltages 17 by all of the slave controllers 7 is performed in a periodic frame following the periodic frame of the first initial beacon 15. However, this could also be done later or immediately following the reception of the first initial beacon 15, with each slave controller 7 having to observe its sending slot. The same applies for sending the beacon 18.

[0070] In a fourth step 19, each slave controller 7 determines the equalization need and possibly the equalization period for the multiple accumulators 10 to which it is coupled.

[0071] More specifically, each slave controller 7 receives the minimum voltage of the traction battery 2 in a beacon 18. Furthermore, in active mode, and unlike the state of the art, the master controller 6 transmits the current circulating in the traction battery 2 to all of the slave controllers 7 via the gateway 9. The master controller 6 comprises a sensor 20 that enables the master controller 6 to determine the current circulating in the battery 2.

[0072] Thus, the slave controller 7 has the necessary information to determine the status indicators of the multiple accumulators 10 to which it is coupled. These status indicators are, for example, the state of health or state of charge of the battery 2.

[0073] To determine whether an accumulator 10 to which a slave controller 7 is coupled requires equalization, the slave controller 7 can perform a comparison between the voltage of that accumulator and the minimum voltage of the battery 2 received in the beacon 18. If the difference between the voltage of the accumulator 10 and the minimum voltage is less than a predefined threshold S, there is no need for equalization of said accumulator 10 and therefore the equalization period is 0. Conversely, when the difference is greater than the threshold S, there is a need for equalization and an equalization period is determined and then applied by the slave controller 7.

[0074] The threshold S is, for example, 5 millivolts if the measurement accuracy is less than 2 millivolts.

[0075] Thus, the need for equalization and the equalization duration are determined in the inactive mode only by the slave controller 7 and not by the master controller 6. In this way, the autonomy of the low-voltage battery 3 is not reduced since in the inactive mode the master controller 6 is not used, since the slave controller 7 is powered by the traction battery 2 and not by the low-voltage battery 3. Furthermore, there is no handicap in using the traction battery 2 in the inactive mode due to the use of the slave controller 7, since the traction battery 2 has a large autonomy.

Claims

1. 1. A system (1) for managing an accumulator battery (2) of an electric vehicle, comprising: a plurality of slave controllers (7) respectively coupled to a plurality of accumulators (10) of the battery (2); and a master controller (6) configured to determine, in an active mode of the management system (1), a period for equalizing the charges of the accumulators (10), the management system (1) having an inactive mode in which the period for equalization is determined solely by the slave controllers (7).

2. 2. The system (1) of claim 1, wherein during the inactive mode, each slave controller (7) determines the period for equalizing the plurality of accumulators (10) to which each slave controller (7) is coupled.

3. 3. The system according to claim 1 or 2, wherein the master controller (6) is powered by a low voltage battery (3) and the slave controller (7) is powered by a traction battery (2).

4. 3. The system (1) according to claim 1 or 2, wherein the master controller (6) and the slave controller (7) use wireless communication means.

5. A method for equalizing the charge of each of the accumulators (10) of an accumulator battery (2) of an electric vehicle, which can be implemented by a management system (1) according to claim 1 or 2.

6. The master controller (6) communicates in the active mode the current circulating in the battery (2) to the slave controller, and the method comprises in the inactive mode the following steps: - the slave controller (7) becomes the slave master controller (12); - the slave-master controller (12) requests the other slave controllers (7) to transmit the smallest voltage among their accumulators (10); - the slave master controller (12) transmitting to each of the other slave controllers (7) the minimum voltage of the battery (2) from among the minimum voltages of the plurality of accumulators (10) of each slave controller (7); each slave controller (7) determining the need for equalization and the duration of equalization for its accumulators (10); The equalization method of claim 5, comprising:

7. 6. The equalization method according to claim 5, characterized in that the equalization method is implemented periodically at a very low frequency in the inactive mode.

8. 7. The method of claim 6, wherein the step of determining (19) the need for equalization includes determining, by the slave controller (7), an indicator of the state of the plurality of accumulators (10).

9. The method of claim 8, wherein the status indicators include a state of health and a state of charge of the battery (2).

10. 7. The method of claim 6, wherein each time the method is implemented, the slave controller (7) that becomes the slave master controller (12) changes.

11. An electric motor vehicle comprising a traction battery (2), a low-voltage battery (3) and a traction battery (2) management system (1) as described in claim 1 or 2, wherein the system (1) is capable of implementing the method as described in claim 5.

12. 12. The vehicle of claim 11, wherein the management system (1) comprises a master controller (6) powered by the low-voltage battery (3) of the vehicle and a slave controller (7) powered by the traction battery (2).

13. The vehicle of claim 11 , wherein the active mode corresponds to the vehicle being switched on and the inactive mode corresponds to the vehicle being switched off.

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