Unit and system for wireless balancing of battery cells

Abstract

The invention relates to a balancing unit (U2) mounted on a battery cell (C2), comprising: means (MM2) for measuring a state parameter of the cell (C2); a wireless communication device (MD2) capable of transmitting and receiving the state parameter; and a wireless power transmission device (ME2).

Description

[0001] This application is a divisional application of the Chinese patent application “Unit and system for wireless balancing of battery cells” with application number 201910680406.1 (filing date July 26, 2019). Technical Field

[0002] The present invention relates to the technical field of battery balancing systems including battery packs. Background Art

[0003] A battery pack is formed by a number of cells connected in series. These cells have standard different characteristics in terms of production, temperature distribution or even life cycle, they usually have different states of charge, which degrades the battery pack and reduces its operating efficiency. Therefore, in order to optimize the capacity and life of the battery pack, a BMS (Battery Management System) is used as standard, which is an electronic system that can control the state of charge of the battery pack cells. This element ensures the balance of the charge of the batteries by short-circuiting some of the batteries or by redistributing the power between the batteries.

[0004] exist Figure 1 In FIG. 1 , multiple batteries C1-C3 arranged in series are shown, each of which is connected to a centralized BMS BMS_C via a wired link. Therefore, the BMS has access to the state parameters of each battery, so that it can decide whether balancing is required and achieve balancing when necessary. The disadvantage of this system is that a large number of connecting cables are required, which makes the system complex and bulky to install, and it is difficult to add new batteries. The BMS is usually able to handle only a predetermined number of batteries.

[0005] In order to limit these drawbacks, it is known to use a BMS with a distributed topology, such as in the present application. Figure 2 In this case, each battery CX (X=1..3) is connected to a printed circuit board BMS_X (called "BMS board"), and these boards are connected to each other and to the controller CTRL through wired links.

[0006] Although the number of connecting cables is reduced relative to the centralized topology, many wired connections are still required, which complicates the installation and maintenance of the system. In addition, even if the addition of auxiliary batteries is simplified, it is still cumbersome because the boards need to be disconnected and reconnected to each other, and the controller needs to be adapted according to the number of batteries added, which requires returning the balancing system to the factory.

[0007] Therefore, there is a need for a system for balancing cells forming a battery pack that has better scalability and requires fewer wired connections than prior art systems. Summary of the invention

[0008] The present invention relates to a balancing unit mounted on a battery pack, comprising:

[0009] - means for measuring a state parameter of a battery,

[0010] - means for wireless communication, capable of sending and receiving status parameters,

[0011] - Device for wireless power transmission.

[0012] The present invention also relates to a system for balancing battery cells connected in series, comprising a plurality of balancing units, such as the balancing units described above, each balancing unit being mounted on a battery cell, a communication device of each balancing unit being capable of sending status parameters to an adjacent balancing unit and receiving status parameters from an adjacent balancing unit, and a power transmission device being capable of sending power to an adjacent balancing unit and receiving power from an adjacent balancing unit.

[0013] The balancing unit can determine whether the battery is charged too much or too little relative to the adjacent batteries based on its own state parameters and the state parameters received from the adjacent balancing unit via the wireless communication device. Then, the power transmission device can transmit part of the power from the battery to one or two adjacent batteries, or conversely receive power from the adjacent batteries.

[0014] It should be noted that power transfer is operational during charging, discharging and inactive states of the battery, since the balancing unit is permanently powered by the battery.

[0015] Furthermore, no cables are required between the various balancing units. Moreover, each balancing unit operates autonomously, therefore, they do not need to be connected to a central unit in order to activate balancing. All this limits the connections, system complexity, space requirements, weight, etc.

[0016] Furthermore, the balancing system is completely flexible: it is enough to place two balancing units side by side so that data communication or power transfer is possible, which facilitates the addition or removal of batteries.

[0017] In one non-limiting embodiment, the communication means and the power transmission means are identical. This makes it possible to limit the number of components of the balancing unit, which has advantages in terms of complexity, space requirements, weight, cost and power consumption.

[0018] Advantageously, these are inductive means, in particular formed by two coils arranged on two sides of the battery. Each coil makes it possible to communicate with one balancing unit assigned to an adjacent battery. Advantageously, the coils can be calibrated for optimal data communication and power transfer. Both data communication and inter-unit balanced power transfer are more optimized when the distance between the balancing units is small.

[0019] In one non-limiting embodiment, a battery's state parameters include measurements of the battery's voltage and temperature as well as the battery's operating state.

[0020] In one non-limiting embodiment, the status parameter includes the operating duration of the battery.

[0021] In one non-limiting embodiment, the balancing unit includes a memory including parameters for regulating the battery and an event history related to the battery. The balancing unit can access the memory to record and save the event history. The event history of the battery and the control parameters of the installation can be accessed via wireless data communication means, for example from a maintenance device external to the battery.

[0022] Advantageously, the balancing unit takes into account the regulation parameters and the event history in order to decide whether to transmit or receive power.

[0023] In one non-limiting embodiment, the balancing system comprises a plurality of energy consuming elements, each of which is assigned to a battery and connected in parallel to said battery, the balancing unit mounted on said battery comprising means for controlling the energy consuming elements. The energy consuming elements are used at the end of charging the battery. The energy consuming elements make it possible to consume a portion of the power that is not needed by the battery because the battery is charged as a whole.

[0024] In a non-limiting embodiment, the state parameter comprises a measurement of current in the energy consuming element.

[0025] In one non-limiting embodiment, each dissipative element is formed by a metal oxide gate semiconductor field effect transistor (MOSFET) with its drain and source separated on two sides of the associated battery and its gate connected to the associated balancing unit. However, the dissipative element can be any element capable of short-circuiting the battery when it is charged (e.g., resistor, circuit breaker, commutator, bipolar transistor, ...). BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other features and advantages will become apparent from the following description given by way of example and not limitation with reference to the accompanying drawings, in which:

[0027] Figure 1 (described) represents a plurality of batteries arranged in series according to the prior art, the balancing of which is ensured by a centralized topology BMS,

[0028] Figure 2 (described) represents a plurality of batteries arranged in series according to the prior art, the balancing of which is ensured by a distributed topology BMS,

[0029] Figure 3 represents a plurality of batteries arranged in series according to the invention, the balancing of which is ensured by a balancing system via wireless power transmission,

[0030] Figure 4 represents a balancing unit of a balancing system by wireless power transmission according to the present invention,

[0031] Figure 5 A battery with a mounted balancing unit according to the invention is shown. DETAILED DESCRIPTION

[0032] Figure 3 : represents a battery pack according to the present invention comprising batteries C1-C3 installed in series and forming a battery pack, and a balancing system SE of the battery pack. The balancing system comprises a plurality of energy consumption elements D1-D3 and a plurality of balancing units U1-U3. Each battery is connected to an energy consumption element and a balancing unit. It should be noted that in the described example, the number of batteries, energy consumption elements and balancing units is three, but of course, this number is not restrictive.

[0033] Each dissipative element consists of a MOSFET with its drain and source separated on the two sides of the associated battery and its gate connected to the associated balancing unit. However, the dissipative element can be any element capable of short-circuiting the battery when it is charged (e.g. resistor, circuit breaker, commutator, bipolar transistor...).

[0034] Each balancing unit operates autonomously during the period allocated to the battery. The balancing system according to the invention is completely decentralized. As an example, Figure 4 It represents the balancing unit U2, and it should be understood that the other units are the same. The balancing unit U2 includes:

[0035] means MC2 for controlling the associated energy consuming element D2,

[0036] means MM2 for measuring a state parameter of an associated battery C2,

[0037] means MD2 for wireless communication with balancing units U1 , U3 assigned to adjacent batteries C1 , C3 , so that in particular state parameters can be sent and received,

[0038] means ME2 for wireless power transmission with balancing units U1, U3 assigned to adjacent batteries C1, C3,

[0039] The memory MU2 includes parameters for regulating the battery C2 and a history of events related to the battery.

[0040] The control device MC2 can control the associated energy consumption element D2 by determining whether to short-circuit the associated battery C2.

[0041] The measuring device MM2 can measure state parameters including in particular the voltage of the associated battery C2 , the current flowing through the energy-consuming element D2 , and the temperature of the battery C2 .

[0042] The communication device MD2 enables the balancing unit U2 to send status parameters to the balancing units U1, U3 of the adjacent batteries C1, C3, and also receive their status parameters. Therefore, the communication device MD2 is bidirectional. In one embodiment, the communication device MD2 can also receive or send status reports (e.g., indicating whether the battery is in the balancing process) and commands.

[0043] The power transmission device ME2 enables the battery C2 to send power from the battery C2 to the adjacent batteries C1, C3, or to receive power from the adjacent batteries C1, C3. Therefore, the power transmission device ME2 is bidirectional. The power transmission is wireless and managed by the balancing unit. The state parameters sent between the battery C2 and the adjacent batteries C1, C3 can adjust the amount of power to be sent.

[0044] In the example shown, the communication device MD2 and the power transmission device ME2 are of the inductive type and are formed by two coils B21, B23, one coil B21 of the two coils B21, B23 being used to communicate with one U1 of two adjacent units U1, U3, and the other coil B23 of the two coils B21, B23 being used to communicate with the other U3 of the two adjacent units U1, U3. Different frequencies are used for data communication and power transmission. It should be noted that the coupling between the balancing units can be any type of coupling except inductive coupling. Fei Lu's article "A review on the recent development of capacitive wireless power transfer technology", especially with reference to its Figure 2 , describing various types of possible couplings.

[0045] The memory MU2 includes parameters for regulating the battery C2. The regulating parameters include factory parameters inherent to the production of the battery pack (such as an identification number) and parameters for balancing (such as minimum and maximum charge and discharge voltages, or even a correspondence table of the state of charge according to the voltage of the battery). The memory MU2 also includes the history of events experienced by the battery C2 during its life, such as the duration of use of the battery, alarms, bad electrical treatment of the battery, etc. The memory is a protected area and it can be considered that it involves data security. Only the balancing unit U2 itself and the manufacturer can access the memory MU2 and can modify the data contained therein. The balancing unit U2 can, for example, be placed on a dedicated wireless bracket, which makes it possible to access the memory MU2 via the communication device MD2.

[0046] The assembly with the battery C2, the energy consumption element D2 and the balancing unit U2 forms a compact assembly, such as Figure 5 As shown, the balancing unit U2 is installed in the battery C2. Figure 5 Represents a battery C2, on both sides of which are placed two coils B21, B23, which are connected to a balancing unit U2 mounted on a flexible printed circuit. This arrangement ensures the symmetry of the structure, which makes it possible to ignore the orientation of the assembly during installation or replacement. The miniaturization of the system makes it possible to minimize the impact in terms of volume and weight. The coils B21, B31 are mechanically positioned to ensure an optimal power transmission yield.

[0047] The balancing system according to the invention has many advantages, among which:

[0048] - it is flexible, i.e. it allows adding an unlimited number of cells in series,

[0049] - it allows use in both active (charging and discharging) and inactive states of the battery,

[0050] - it allows communication between adjacent batteries to adapt power levels and exchange data,

[0051] - it allows the transmission of commands or information to multiple batteries through wireless communication of the links between all the batteries connected in series,

[0052] - it allows to optimize the power transmission through the mechanical alignment of the cells of the battery pack,

[0053] - The distance between batteries is relatively short, improving the output of power transmission,

[0054] - it allows remote access to each battery in order to know (and possibly modify) its characteristics and information about its parameters,

[0055] - It optimizes the communication between balanced cells through coupling, and

[0056] - It allows mechanical stabilization and positioning of power transmission elements.

[0057] Of course, the invention is not limited to the examples shown and is subject to different variants and modifications that are obvious to a person skilled in the art.

Claims

1. A balancing unit mounted on a battery pack cell, comprising: - means for measuring a state parameter of said battery, - wireless communication means capable of sending and receiving status parameters, and - wireless power transmission device, Characterized in that the balancing unit operates autonomously, is connected to the battery cells, and the power transmission means managed by the balancing unit are able to transmit a portion of the power from the battery cells to one or two adjacent battery cells, or conversely, receive power from adjacent cells.

2. The balancing unit according to claim 1, characterized in that: The communication means and the power transmission means are identical.

3. The balancing unit according to claim 2, characterized in that: The communication means (MD2) and the power transmission means are of the inductive type, in particular formed by two coils arranged on two sides of the battery and connected to the balancing unit mounted on a flexible printed circuit.

4. The balancing unit according to claim 1, characterized in that: The state parameters of the battery include measurements of the voltage and temperature of the battery and the operating state of the battery.

5. The balancing unit according to claim 1, characterized in that: The state parameter of the battery comprises an operating duration of the battery.

6. The balancing unit according to claim 1, characterized in that: It comprises a memory including parameters for conditioning the battery and a history of events associated with the battery.

7. A balancing system for battery cells connected in series, comprising a plurality of balancing units according to claim 1, each balancing unit being mounted on a corresponding battery of the battery pack, the communication device of each balancing unit operating autonomously and being capable of sending status parameters to and receiving status parameters from the adjacent balancing unit, and the power transmission device of each balancing unit being capable of sending power to or receiving power from the adjacent balancing unit.

8. The balancing system according to claim 7, characterized in that: It comprises a plurality of energy consuming elements, each of which is assigned to a battery and connected in parallel with the battery, and the balancing unit mounted on the battery comprises a device for controlling the energy consuming elements.

9. The balancing system according to claim 8, characterized in that: The state parameter of the battery comprises a measurement of the current in the energy consuming element connected in parallel with the battery.

10. The balancing system according to claim 8, characterized in that: Each dissipative element is formed by a metal oxide gate field effect transistor, with its drain and source separated on two sides of the battery and its gate connected to the balancing unit.

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