Unit and system for wireless balancing for battery cell

Abstract

A balancing unit is installed on a battery cell, and includes an element for measuring state parameters of the cell, a wireless communication element, making it possible to send and receive state parameters, and a wireless power transfer element.

Claims

1. A balancing apparatus installed on a battery cell in a balancing system in which a plurality of balancing appartuses, each installed on a corresponding battery cell, are connected in series, the balancing apparatus comprising: means for measuring state parameters of the battery cell; wireless communication means for sending the measured state parameters to an adjacent balancing apparatus of the plurality of balancing apparatuses, and for receving state parameters from the adjacent balancing apparatus; and wireless power transfer means, wherein the balancing apparatus functions autonomously, and the balancing apparatus is configured to independently determine, based on the measured state parameters and the received state parameters to transfer power to an adjacent battery cell or to receive external power from the adjacent battery cell, and, based on the determination, cause the power transfer means to transfer the power from the battery cell to adjacent battery cell or receive power from adjacent cell.

2. The balancing apparatus according to claim 1, wherein the communication means and the power transfer means are the same.

3. The balancing apparatus according to claim 2, wherein the communication means and the power transfer means are each of an inductive type and formed by two coils that are disposed on respective sides of the battery cell and connected to the balancing apparatus, which is mounted on a flexible printed circuit.

4. The balancing apparatus according to claim 1, wherein the measured state parameters of the battery cell comprise measurements of voltage and temperature of the battery cell, and an operational status of the battery cell.

5. The balancing apparatus according to claim 1, wherein the measured state parameters of the battery cell comprise an operational duration of the battery cell.

6. The balancing unit according to claim 1, further comprising a memory storing parameters for adjusting the battery cell and a history of events relating to the battery cell.

7. The balancing apparatus of claim 6, wherein the balancing apparatus is further configured to determine to transfer the power or receive the external power based on the parameters for adjusting and the history of events stored in the memory.

8. The balancing system of battery cells connected in the series, the system comprising the plurality of balancing apparatuses, each being the balancing apparatus according to claim 1.

9. The balancing system according to claim 8, further comprising a plurality of dissipative elements, each dissipative element being assigned to a corresponding battery cell, and connected in parallel to the battery cell, and each balancing apparatus installed on the cell further comprises means for controlling the dissipative element.

10. The balancing system according to claim 9, wherein the measured state parameters of the battery cell comprise a measurement of the current in the dissipative element connected in parallel to the battery cell.

11. The balancing system according to claim 9, wherein each dissipative element is formed by a metal oxide gate field effect transistor, a drain and a source of which are branched on both sides of the battery cell, and a gate of which is connected to the balancing unit.

12. The balancing apparatus of claim 8, wherein each balancing apparatus in the plurality of balancing apparatuses is configured to independently and autonomously determine to transfer power or receive external power.

13. The balancing apparatus of claim 1, wherein the means for measuring state parameters is configured to measure the state parameters of only the battery cell on which the balancing apparatus is installed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages will emerge clearly from the description which is made hereafter, by way of example and in no way limiting, with reference to the annexed drawings, in which:

(2) FIG. 1, already described, represents a plurality of cells arranged in series, the balancing of which is ensured by a centralised topology BMS, according to prior art,

(3) FIG. 2, already described, represents a plurality of cells arranged in series, the balancing of which is ensured by a distributed topology BMS, according to prior art,

(4) FIG. 3 represents a plurality of cells arranged in series, the balancing of which is ensured by a balancing system by wireless power transfer according to the invention,

(5) FIG. 4 represents a balancing unit of a balancing system by wireless power transfer according to the invention,

(6) FIG. 5 represents a cell with an installed balancing unit according to the invention.

DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT

(7) FIG. 3 represents a battery comprising cells C1-C3 mounted in series and forming a battery, and a balancing system SE of said battery according to the invention. The balancing system comprises a plurality of dissipative elements D1-D3 and a plurality of balancing units U1-U3. There is connected to each cell a dissipative element and a balancing unit. It is noted that in the described example, the cells, the dissipative elements and the balancing units are each three in number but of course this number is not limiting.

(8) Each dissipative element is composed of a MOSFET, the drain and the source of which are branched on both sides of the associated cell, and the gate of which is connected to the associated balancing unit. However, the dissipative element might be any element capable of short-circuiting the cell (for example a resistance, a circuit breaker, a commutator, a bipolar transistor . . . ) when the latter is charged.

(9) Each balancing unit functions autonomously during assignment to a cell. The balancing system according to the invention is completely decentralised. By way of example, FIG. 4 represents the balancing unit U2, it being understood that the other units are identical. The balancing unit U2 comprises: means MC2 for controlling the associated dissipative element D2, means MM2 for measuring state parameters of the associated cell C2, means MD2 for wireless communication with the balancing units U1, U3 assigned to the adjacent cells C1, C3, making it possible in particular to send and to receive state parameters, means ME2 for wireless power transfer with balancing units U1, U3 assigned to the adjacent cells C1, C3, a memory MU2 comprising parameters for adjusting the cell C2 and a history of events relating to the cell.

(10) The control means MC2 make it possible to control the associated dissipative element D2, by short-circuiting or not the associated cell C2.

(11) The measuring means MM2 make it possible to measure state parameters which comprise in particular the voltage of the associated cell C2, the current passing through the dissipative element D2, and the temperature of the cell C2.

(12) The communication means MD2 make it possible for the balancing unit U2 to send its state parameters to the balancing units U1, U3 of the adjacent cells C1, C3, and furthermore to receive their state parameters. The communication means MD2 are therefore bidirectional. The communication means MD2 likewise make it possible, in one embodiment, to receive or send status reports (indicating for example if a cell is in the process of balancing) and commands.

(13) The power transfer means ME2 make it possible for the cell C2 to send to the adjacent cells C1, C3 power from the cell C2, or to receive the power coming from the adjacent cells C1, C3. The power transfer means ME2 are therefore bidirectional. The power transfer is wireless, and managed by the balancing unit. The state parameters transmitted between the cell C2 and the adjacent cells C1, C3 make it possible to adjust the quantity of power to be transmitted.

(14) In the represented example, the communication means MD2 and power transfer means ME2 are of the inductive type and are formed from two coils B21, B23, one B21 of the two coils B21, B23 serving to communicate with one U1 of the two adjacent units U1, U3, the other B23 of the two coils B21, B23 serving to communicate with the other U3 of the two adjacent units U1, U3. Different frequencies are used for data communication and power transfer. It is noted that types of coupling other than inductive coupling between the balancing units are possible. The document “A review on the recent development of capacitive wireless power transfer technology” by Fei Lu, describes, in particular with reference to its FIG. 2, various types of possible couplings.

(15) The memory MU2 comprises parameters for adjusting the cell C2. The adjustment parameters comprise factory parameters inherent to the production of the battery, for example its identification number, and parameters for the balancing, for example a minimum and maximum discharge and charge voltage or even a correspondence table of the state of charge as a function of the voltage of the cell. The memory MU2 likewise comprises a history of events undergone by the cell C2 during its lifespan, for example the duration of use of the cell, alerts, poor electrical handling of the cell, etc. The memory is a protected zone, it might be considered that it concerns a data safe. Only the balancing unit U2 itself and the manufacturer have access to the memory MU2 and can modify the data contained therein. The balancing unit U2 can, for example, be placed on a dedicated wireless support which makes it possible to access, via the communication means MD2, the memory MU2.

(16) The assembly with cell C2, dissipative element D2 and balancing unit U2 form a compact assembly, as illustrated in FIG. 5. The balancing unit U2 is installed in the cell C2. FIG. 5 represents the cell C2, on both sides of which the two coils B21, B23 are placed, the two coils being connected to the balancing unit U2 mounted on a flexible printed circuit. This arrangement ensures a symmetry of structure which makes it possible to disregard the orientation of the assembly during its mounting or its replacement. Miniaturisation of the system makes it possible to minimise its impact in terms of volume and weight. The coils B21, B31 are positioned mechanically in order to guarantee an optimal power transfer yield.

(17) The balancing system according to the invention has numerous advantageous, amongst others: it is flexible, i.e. it allows the addition of an undefined number of cells in series, it allows utilisation in active states (charge and discharge) and inactivity of the cell, it allows communication between adjacent cells for adaptation of the power levels and exchange of data, it allows, by linked wireless communication between all the cells in series, transfer of commands or information to several cells, it allows optimisation of power transfer by mechanical alignment of the cells of the battery, the distances between the cells being relatively short, the yield of the power transfer is improved, it allows remote access to each cell in order to know (and possibly to modify) its characteristics and information about parameters, it optimises communication between balancing cells, through the coupling, and it allows mechanical stability and positioning of the power transfer elements.

(18) Of course the present invention is not limited to the illustrated example and is open to different variants and modifications which will be apparent to the person skilled in the art.