Processing

Please wait...

Settings

Settings

Goto Application

1. WO2020136214 - A SYSTEM AND A METHOD FOR TRANSFERRING POWER BETWEEN A MASTER CONTROL UNIT AND A LOCAL CONTROL UNIT COUPLED TO AN ENERGY STORAGE STRING

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

[ EN ]

Claims

1. An energy storage system (100) comprising

● an energy storage string (10) formed by a plurality of rechargeable cells (2a,2b,2c) connected in series via electrical connectors (5), and wherein said energy storage string (10) has a positive string terminal (BT+) at a first end and a negative string terminal (BT-) at a second end, ● an energy management device comprising a master control unit (4) and at least a first local control unit (3c) associated to a first rechargeable cell (2c) of said plurality of rechargeable cells,

and wherein said master control unit (4) comprises i) a storage string connecting circuit (SCC) electrically connecting said positive string terminal (BT+) with said negative string terminal (BT-), ii) a master AC signal generator (TAC-M) and iii) a master AC signal receiver (RAC- M),

and wherein said first local control unit (3c) comprises i) a cell connecting circuit (CCC) electrically connecting a positive (CT+) and a negative (CT-) cell terminal of said first rechargeable cell (2c), ii) a local AC signal

generator (TAC-L) and iii) a local AC signal receiver (RAC- L),

characterized in that

● said storage string connecting circuit (SCC) comprises a first capacitor device (C1), and wherein said first capacitor device (C1) and said energy storage string (10) are forming part of a first closed-loop LC-circuit (LC-1), and

● said cell connecting circuit (CCC) comprises a second capacitor device (C2), and wherein said second capacitor device (C2) and said first rechargeable cell (2c) are forming part of a second closed-loop LC-circuit (LC-2), and in that

said master AC signal generator (TAC-M) is adapted for transmitting power to said local control unit by supplying a sequence of first AC pulses to said first closed-loop LC-circuit (LC-1), and wherein said local AC signal receiver (RAC-L) is configured for

● detecting the sequence of first AC pulses in said second closed-loop LC-circuit (LC-2) following propagation of the sequence of first AC pulses from the first to the second closed-loop LC-circuit, and

● rectifying the sequence of first AC pulses detected,

thereby generating a first DC current for charging a first capacitor tank (C3) of said first local control unit.

2. An energy storage system (100) according to claim 1 wherein said local AC signal generator(TAC-L) is adapted for transmitting power to said master control unit (4) or to a second local control unit associated to a second

rechargeable cell by supplying a sequence of second AC pulses to said second closed-loop LC-circuit (LC-2).

3. An energy storage system (100) according to claim 2 wherein said master AC signal receiver (RAC-M) is configured for

● detecting the sequence of second AC pulses in said first closed-loop LC-circuit (LC-1) following propagation of the sequence of second AC pulses from the first to the second closed-loop LC-circuit, and for

● rectifying the sequence of second AC pulses detected, thereby generating a second DC current for charging a capacitor tank or any other charge storage device of said master control unit(4).

4. An energy storage system (100) according to claim 2 comprising a second local control unit associated to a second rechargeable cell and wherein a local AC signal receiver of the second local control unit is configured for detecting said sequence of second AC pulses transmitted by the local AC signal generator (TAC-L) of the first control unit and for rectifying the second AC pulses detected, thereby generating a further DC current for charging a capacitor tank of said second local control unit.

5. An energy storage system (100) according to anyone of previous claims wherein said first local control unit comprises a microcontroller (50) and an energy balancing circuit, and wherein the energy balancing circuit includes a DC-DC voltage converter (60) coupled between said first capacitor tank (C3) of said first local control unit and the positive (CT+) and the negative (CT-) cell terminals of the first rechargeable cell (2c) and wherein said

microcontroller (50) is configured for controlling

a) a charging of said first rechargeable cell (2c) by de-charging the first capacitor tank (C3), and/or

b) a de-charging of said first rechargeable cell (2c) by charging the first capacitor tank (C3).

6. An energy storage system (100) according to anyone of previous claims wherein said master AC signal generator (TAC-M) is adapted for transmitting first data to said first local control unit by defining a sequence of modulated first AC pulses and supplying said sequence of modulated AC pulses to said first closed-loop LC-circuit (LC-1) and wherein said local AC signal receiver (RAC-L) is configured for receiving said first data by monitoring the sequence of modulated first pulses transmitted by the master AC signal generator and by demodulating modulated pulses received.

7. An energy storage system (100) according to anyone of previous claims wherein said local AC signal generator(TAC- L) is adapted for transmitting second data to said master control unit (4) by defining a sequence of modulated second AC pulses and by supplying said sequence of modulated second AC pulses to said second closed-loop LC-circuit (LC-1) and wherein said master AC signal receiver (RAC-M) is configured for receiving said second data by monitoring the sequence of modulated second pulses transmitted by the local AC signal generator and by demodulating modulated pulses received.

8. An energy storage system (100) according to anyone of previous claims wherein said master AC signal generator (TAC-M) is operable at at least a first operational

frequency fAC-1 and wherein said local AC signal generator (TAC-L) is operable at at least a second operational

frequency fAC-2.

9. An energy storage system (100) according to claims 8 wherein the first operational frequency fAC-1 is different from the second operational frequency fAC-2 and wherein said master AC signal generator(TAC-M) is further operable at said second operational frequency fAC-2 and configured for transmitting first data to said first local control unit (3a) by defining a sequence of frequency modulated first AC pulses using a communication protocol based on said two signal frequencies fAC-1 and fAC-2 and by supplying said sequence of frequency modulated first AC pulses to said first closed-loop LC-circuit (LC-1), and wherein said local AC signal receiver(RAC-L) is configured for receiving said first data by monitoring the sequence of frequency modulated first pulses transmitted by the master AC signal generator and by demodulating frequency modulated pulses received.

10. An energy storage system (100) according to claim 9 wherein said local AC signal generator(TAC-L) is further operable at said first operational frequency fAC-1 and configured for transmitting second data to said master control unit (4) by defining a sequence of frequency modulated second AC pulses using a communication protocol based on the two operational pulse frequencies fAC-1 and fAC-2 and by supplying said sequence of frequency modulated second AC pulses to said second closed-loop LC-circuit (lC-2), and wherein said master AC signal receiver (RAC-M) is configured for receiving said second data by monitoring the sequence of frequency modulated second AC pulses

transmitted by the local AC signal generator (TAC-L) and by demodulating frequency modulated pulses received.

11. An energy storage system (100) according to anyone of claims 8 to 10 wherein each of said rechargeable cells (2a,2b,2c) is characterized by a frequency-dependent cell impedance ZC, and wherein said cell impedance ZC is

dominated by an inductance behaviour at a frequency above a characteristic frequency fL, and wherein fAC-1 ³ fL and fAC-2 ³ fL.

12. An energy storage system (100) according to anyone of claims 8 to 11 wherein said first closed-loop LC-circuit (LC-1) has a first natural resonant frequency (f1) and a first bandwidth (BW1) and wherein said first operational frequency fAC-1 and said second operational frequency fAC-2 fall within said first bandwidth (BW1).

13. An energy storage system (100) according to any of claims 8 to 11 wherein said second closed-loop LC-circuit (LC-2) has a second natural resonant frequency (f2) and a second bandwidth (BW2) and wherein said first operational frequency fAC-1 and said second operational frequency fAC-2 fall within said second bandwidth (BW2).

14. An energy storage system (100) according to any of claims 8 to 11 wherein said first closed-loop LC-circuit (LC-1) has a first natural resonant frequency (f1) and a first bandwidth (BW1) and said second closed-loop LC-circuit (LC-2) has a second natural resonant frequency (f2) and a second bandwidth (BW2), and wherein

a) said first operational frequency fAC-1 falls within said first bandwidth (BW1) and/or within said second bandwidth (BW2), and

b) said second operational frequency fAC-2 falls within said first bandwidth (BW1) and/or within said second bandwidth (BW2).

15. An energy storage system (100) according to claim 8 wherein said first operational frequency fAC-1 of said master AC signal generator (TAC-M) is selected to be within a first resonant region around a first natural resonant frequency (f1) of said first closed-loop LC-circuit (LC-1) or selected to be within a second resonant region around a second natural resonant frequency (f2) of said second closed-loop LC-circuit,

and wherein said first resonant region is defined by a lower frequency fLC-1-L and an upper frequency fLC-1-H such that ZLC-1(fLC-1-L) = ZLC-1(fLC-1-H) = XC1(f1),

and wherein said second resonant region is defined by a lower frequency fLC-2-L and an upper frequency fLC-2-H such that ZLC-2(fLC-2-L) = ZLC-2(fLC-2-H) = XC2(f2), with f1 and f2 being said first and second natural resonant frequency, ZLC-1 and ZLC-2 being a total impedance associated to respectively said first and said second closed-loop LC-circuit, and XC1 and XC2 being a capacitive reactance associated to

respectively said first (C1) and said second (C2) capacitor device.

16. An energy storage system (100) according to claim 15 wherein said second operational frequency fAC-2 of said local AC signal generator (TAC-L) is selected to be within said second resonant region around said second natural resonant frequency (f2) or selected to be within said first resonant region around said first natural resonant

frequency (f1).

17. A method for transferring power between a master control unit (4) of an energy storage string (10) formed by a plurality of rechargeable cells (2a,2b,2c) connected in series via electrical connectors (5) and a local control unit (3c) associated to a first rechargeable cell (2c) of said plurality of rechargeable cells, the method comprising ● electrically connecting a positive string terminal (BT+) at a first end and a negative string terminal (BT-) at a second end of the energy storage string (10) with a storage string connecting circuit (SCC), and wherein the storage string connecting circuit (SCC) comprises a first capacitor device (C1), and wherein said first capacitor and said energy storage string (10) are forming part of a first closed-loop LC-circuit (LC-1),

● electrically connecting a positive (CT+) and a

negative (CT-) cell terminal of said first rechargeable cell (2c) with a cell connecting circuit (CCC), and wherein

said connecting circuit (CCC) comprises a second capacitor device (C2), and wherein said second capacitor device (C2) and said first rechargeable cell (2c) are forming part of a second closed-loop LC-circuit (LC-2),

● transmitting power from said master control unit to said local control unit by: using a master AC signal

generator (TAC-M) of the master control unit for

supplying a sequence of first AC pulses to said first closed-loop LC-circuit (LC-1), using a local AC signal receiver(RAC-L) of the local control unit for detecting the sequence of first AC pulses in said second closed- loop LC-circuit (LC-2) following propagation of the sequence of first AC pulses from the first to the second closed-loop LC-circuit, and rectifying the sequence of first AC pulses detected, and/or

● transmitting power from said local control unit to said master control unit by: using a local AC signal

generator (TAC-L) of said local control unit for

supplying a sequence of second AC pulses to said second closed-loop LC-circuit (LC-2), using a master AC signal receiver (RAC-M) of the master control unit for detecting the sequence of second AC pulses in said first closed- loop LC-circuit (LC-1) following propagation of the sequence of first AC pulses from the second to the first closed-loop LC-circuit, and rectifying the sequence of second AC pulses detected.

18. An energy storage system (100) comprising

● an energy storage string (10) formed by a plurality of rechargeable cells (2a,2b,2c) connected in series via electrical connectors (5), and wherein said energy storage string (10) has a positive string terminal (BT+) at a first end and a negative string terminal (BT-) at a second end, ● an energy management device comprising a master control unit (4) and at least a first local control unit (3c) associated to a first rechargeable cell (2c) of said plurality of rechargeable cells,

and wherein said master control unit (4) comprises: i) a storage string connecting circuit (SCC) electrically connecting said positive string terminal (BT+) with said negative string terminal (BT-), ii) a master AC signal generator (TAC-M) operable at at least a first operational frequency fAC-1 and iii) a master AC signal receiver (RAC-M), and wherein said first local control unit (3c) comprises: i) a cell connecting circuit (CCC) electrically connecting a positive (CT+) and a negative (CT-) cell terminal of said first rechargeable cell (2c), ii) a local AC signal

generator (TAC-L) operable at at least a second operational frequency fAC-2 and iii) a local AC signal receiver (RAC-L), characterized in that

● said storage string connecting circuit (SCC) comprises a first capacitor device (C1), and wherein said first capacitor device (C1) and said energy storage string (10) are forming part of a first closed-loop LC-circuit (LC-1), and

● said cell connecting circuit (CCC) comprises a second capacitor device (C2), and wherein said second capacitor device (C2) and said first rechargeable cell (2c) are forming part of a second closed-loop LC-circuit (LC-2), and in that said master AC signal generator (TAC-M) is configured for supplying a first AC signal to said first closed-loop LC-circuit (LC-1) and/or said local AC signal generator (TAC-L) is configured for supplying a second AC signal to said second closed-loop LC-circuit (LC-2), and in that said local AC signal receiver (RAC-L) is

configured for detecting the first AC signal in said second closed-loop LC-circuit (LC-1) following propagation of the first AC signal from the first to the second closed-loop LC-circuit and/or said master AC signal receiver (RAC-M) is configured for detecting the second AC signal in said first closed-loop LC-circuit (LC-1) following propagation of the second AC signal from the second to the first closed-loop LC-circuit.

19. An energy storage system (100) according to claim 18 wherein said first AC signal is a power signal or a data signal and said second AC signal is power signal or a data signal.

20. An energy storage system (100) according to claim 18 or claim 19 wherein said first operational frequency fAC-1 of said master AC signal generator (TAC-M) and said second operational frequency fAC-2 of said local AC signal generator (TAC-L) are selected in relation to a first natural resonant frequency (f1) of said first closed- loop LC-circuit (LC-1) and/or in relation to a second natural resonant frequency (f2) of said second closed- loop LC-circuit (LC-2) such that a signal amplitude of the first AC signal when detected by the local AC signal receiver is larger than a signal amplitude of the first AC signal supplied by the master AC signal generator and such that a signal amplitude of the second AC signal when detected by the master AC signal receiver is larger than a signal amplitude of the second AC signal supplied by the local AC signal generator.

21. An energy storage system (100) according to claim 18 or claim 19 wherein said first closed-loop LC-circuit (LC-1) has a first natural resonant frequency (f1) and said second closed-loop LC-circuit (LC-2) has a second natural resonant frequency (f2), and wherein

a) said first operational frequency fAC-1 of said master AC signal generator (TAC-M) is selected to be within a first resonant region around said first natural resonant frequency (f1) or, alternatively, selected to be within a second resonant region around said second natural resonant frequency (f2),

and

b) said second operational frequency fAC-2 of said local AC signal generator (TAC-L) is selected to be within said second resonant region around said second natural resonant frequency (f2) or, alternatively, selected to be within said first resonant region around said first natural resonant frequency (f1),

and wherein said first resonant region is defined by a lower frequency fLC-1-L and an upper frequency fLC-1-H such that ZLC-1(fLC-1-L) = ZLC-1(fLC-1-H) = XC1(f1),

and wherein said second resonant region is defined by a lower frequency fLC-2-L and an upper frequency fLC-2-H such that ZLC-2(fLC-2-L) = ZLC-2(fLC-2-H) = XC2(f2),

with f1 and f2 being said first and second natural resonant frequency, ZLC-1 and ZLC-2 being a total impedance associated to respectively said first (LC-1) and said second (LC-2) closed-loop LC-circuit, and XC1 and XC2 being a capacitive reactance associated to respectively said first (C1) and said second (C2) capacitor device.

22. An energy storage system (100) according to anyone of claims 18 to 21 wherein said master AC signal generator (TAC-M) is adapted for transmitting power to said local control unit by supplying a first power signal comprising a sequence of first AC pulses to said first closed-loop LC-circuit (LC-1).

23. An energy storage system (100) according to claim 22 wherein said local AC signal receiver (RAC-L) is configured for

● detecting the sequence of first AC pulses in said second closed-loop LC-circuit (LC-2) following propagation of the sequence of first AC pulses from the first to the second closed-loop LC-circuit, and

● rectifying the sequence of first AC pulses detected,

thereby generating a first DC current for charging a first capacitor tank (C3) of said first local control unit.

24. An energy storage system (100) according to anyone of claims 18 to 23 wherein said local AC signal generator (TAC- L) is adapted for transmitting power to said master control unit (4) or to a second local control unit associated to a second rechargeable cell by supplying a second power signal comprising a sequence of second AC pulses to said second closed-loop LC-circuit.

25. An energy storage system (100) according to claim 24 wherein said master AC signal receiver (RAC-M) is configured for

● detecting the sequence of second AC pulses in said first closed-loop LC circuit (LC-1) following propagation of the second AC pulses from the second to the first closed-loop LC-circuit, and for

● rectifying the sequence of second AC pulses detected, thereby generating a second DC current for charging a capacitor tank or any other charge storage device of said master control unit(4).

26. An energy storage system (100) according to claim 24 comprising a second local control unit associated to a second rechargeable cell and wherein a local AC signal receiver of the second local control unit is configured for detecting said sequence of second AC pulses transmitted by the local AC signal generator (TAC-L) of the first control unit and for rectifying the second AC pulses detected, thereby generating a further DC current for charging a second capacitor tank of said second local control unit.

27. An energy storage system (100) according to anyone of claims 23 to 26 wherein said first local control unit comprises a microcontroller (50) and an energy balancing circuit, and wherein the energy balancing circuit includes a DC-DC voltage converter (60) coupled between said first capacitor tank (C3) of said first local control unit and the positive (CT+) and the negative (CT-) cell terminals of the first rechargeable cell (2c) and wherein said

microcontroller (50) is configured for controlling

a) a charging of said first rechargeable cell (2c) by de- charging the first capacitor tank (C3), and/or

b) a de-charging of said first rechargeable cell (2c) by charging the first capacitor tank (C3).

28. An energy storage system (100) according to anyone of claims 18 to 27 wherein said master AC signal generator (TAC-M) is adapted for transmitting first data to said first local control unit by defining a first data signal

comprising a sequence of modulated first AC pulses and supplying said sequence of modulated AC pulses to said first closed-loop LC-circuit (LC-1) and wherein said local 35 AC signal receiver (RAC-L) is configured for receiving said first data by monitoring the sequence of modulated first pulses transmitted by the master AC signal generator and by demodulating modulated pulses received.

29. An energy storage system (100) according to anyone of claims 18 to 28 wherein said local AC signal generator (TAC- L) is adapted for transmitting second data to said master control unit (4) by defining a second data signal

comprising a sequence of modulated second AC pulses and by supplying said sequence of modulated second AC pulses to said second closed-loop LC-circuit (LC-2) and wherein said master AC signal receiver (RAC-M) is configured for

receiving said second data by monitoring the sequence of modulated second pulses transmitted by the local AC signal generator and by demodulating modulated pulses received.

30. An energy storage system (100) according to anyone of claims 18 to 27 wherein the first operational frequency fAC- 1 is different from the second operational frequency fAC-2 and wherein said master AC signal generator(TAC-M) is further operable at said second operational frequency fAC-2 and configured for transmitting first data to said first local control unit (3a) by defining a sequence of frequency modulated first AC pulses using a communication protocol based on said two signal frequencies fAC-1 and fAC-2 and by supplying said sequence of frequency modulated first AC pulses to said first closed-loop LC-circuit (LC-1), and wherein said local AC signal receiver(RAC-L) is configured for receiving said first data by monitoring the sequence of frequency modulated first pulses transmitted by the master AC signal generator and by demodulating frequency modulated pulses received.

31. An energy storage system (100) according to claim 30 wherein said local AC signal generator(TAC-L) is further operable at said first operational frequency fAC-1 and configured for transmitting second data to said master control unit (4) by defining a sequence of frequency modulated second AC pulses using a communication protocol based on the two operational pulse frequencies fAC-1 and fAC-2 and by supplying said sequence of frequency modulated second AC pulses to said second closed-loop LC-circuit (LC-2), and wherein said master AC signal receiver (RAC-M) is configured for receiving said second data by monitoring the sequence of frequency modulated second AC pulses

transmitted by the local AC signal generator (TAC-L) and by demodulating frequency modulated pulses received.

32. An energy storage system (100) according to claim 18 or claim 19 wherein each of said rechargeable cells

(2a,2b,2c) is characterized by a frequency-dependent cell impedance ZC, and wherein said cell impedance ZC is

dominated by an inductance behaviour at a frequency above a characteristic frequency fL, and wherein the first

capacitor device is defined such that f1 > fL and the second capacitor device is defined such that f2 > fL, with f1 and f2 being a first and a second natural resonant frequency of respectively said first and said second closed-loop LC-circuit.

33. A method for resonant power and data transfer between a master control unit (4) of an energy storage string (10) formed by a plurality of rechargeable cells (2a,2b,2c) connected in series via electrical connectors (5) and a local control unit (3c) associated to a first rechargeable cell (2c) of said plurality of rechargeable cells, the method comprising

● electrically connecting a positive string terminal (BT+) at a first end and a negative string terminal (BT-) at a second end of the energy storage string with a storage string connecting circuit (SCC) comprising a first

capacitor device (C1), such that said energy storage string (10) and said first capacitor device (C1) are forming part of a first closed-loop LC-circuit (LC-1),

● electrically connecting a positive (CT+) and a

negative (CT-) cell terminal of said first rechargeable cell (2c) with a cell connecting circuit (CCC) comprising a second capacitor device (C1), such that said first

rechargeable cell (2c) and said second capacitor device (C2) are forming part of a second closed-loop LC-circuit (LC-2),

● providing a master AC signal generator (TAC-M) for supplying a first AC signal to said first closed-loop circuit,

● selecting a first operational frequency fAC-1 for said master AC signal generator (TAC-M) in relation to a first natural resonant frequency (f1) of said first closed-loop LC-circuit (LC-1) and/or in relation to a second natural resonant frequency (f2) of said second closed-loop LC-circuit (LC-2) such that a signal amplitude of the first AC signal when detected by the local AC signal receiver is larger than a signal amplitude of the first AC signal supplied by the master AC signal generator,

● providing a local AC signal generator (TAC-M) for supplying a second AC signal to said second closed-loop circuit,

● selecting a second operational frequency fAC-2 for said local AC signal generator (TAC-L) in relation to the first natural resonant frequency (f1) of said first closed-loop LC-circuit (LC-1) and/or in relation to the second natural resonant frequency (f2) of said second closed-loop LC-circuit (LC-2) such that a signal amplitude of the second AC signal when detected by the master AC signal receiver is larger than a signal amplitude of the second AC signal supplied by the local AC signal generator,

● transmitting power or data from the master control unit to said local control unit by supplying AC signals to said first closed-loop LC circuit at said selected first operational frequency and detecting the AC signals supplied in said second closed-loop LC circuit, and/or

● transmitting power or data between from the local control unit to said master control unit by supplying AC signals to said second closed-loop LC circuit at said selected second operational frequency and detecting the AC signals supplied in said first closed-loop LC circuit.

34. A method according to claim 33 wherein the first operational frequency fAC-1 of the master AC signal generator (TAC-M) is selected to be within a first resonant region around the first natural resonant frequency (f1) of said first closed-loop LC-circuit, or, alternatively, the first operational frequency fAC-1 is selected to be within a second resonant region around the second natural resonant frequency (f2) of said second closed-loop LC- circuit, and

wherein the second operational frequency fAC-2 of the local AC signal generator (TAC-L) is selected to be within said second resonant region around said second natural resonant frequency (f2) or, alternatively, selected to be within said first resonant region around said first natural resonant frequency (f1),

and wherein said first resonant region is defined by a lower frequency fLC-1-L and an upper frequency fLC-1-H such that ZLC-1(fLC-1-L) = ZLC-1(fLC-1-H) = XC1(f1),

and wherein said second resonant region is defined by a lower frequency fLC-2-L and an upper frequency fLC-2-H such that ZLC-2(fLC-2-L) = ZLC-2(fLC-2-H) = XC2(f2), with f1 and f2 being said first and second natural resonant frequency, ZLC-1 and ZLC-2 being a total impedance associated to respectively said first and said second closed-loop LC-circuit, and XC1 and XC2 being a capacitive reactance associated to

respectively said first (C1) and said second (C2) capacitor device.

35. A method according to claim 33 or claim 34 comprising ● transmitting power from said master control unit to said local control unit by: supplying a first AC power signal comprising a sequence of first AC pulses to said first closed-loop LC-circuit (LC-1), detecting the sequence of first AC pulses in said second closed-loop LC-circuit (LC-2) following propagation of the sequence of first AC pulses from the first to the second closed-loop LC- circuit, and rectifying the sequence of first AC pulses detected.

36. A method according to anyone of claims 33 to 35 comprising

● transmitting power from said local control unit to said master control unit by: supplying a second AC power signal comprising a sequence of second AC pulses to said second closed-loop LC-circuit (LC-2), detecting the sequence of second AC pulses in said first closed-loop LC-circuit (LC-1) following propagation of the sequence of first AC pulses from the second to the first closed-

loop LC-circuit, and rectifying the sequence of second AC pulses detected.

37. A method according to claim 33 to 36 comprising ● transmitting first data from said master control unit to said first local control unit by: defining a first data signal comprising a sequence of modulated first AC pulses and supplying said sequence of modulated first AC pulses to said first closed-loop LC-circuit (LC-1), detecting said modulated first AC pulses in said second closed-loop circuit (LC-2) and demodulating the

modulated pulses detected.

38. A method according to anyone of claims 33 to 37

comprising

● transmitting second data from said local control unit to said master control unit by: defining a second data signal comprising a sequence of modulated second AC pulses and supplying said sequence of modulated second AC pulses to said second closed-loop LC-circuit (LC-2), detecting said modulated second AC pulses in said first closed-loop circuit (LC-1) and demodulating the

modulated pulses detected.

39. A method according to anyone of claims 33 to 38

wherein each of said rechargeable cells (2a,2b,2c) is characterized by a frequency-dependent cell impedance ZC, and wherein said cell impedance ZC is dominated by an inductance behaviour at a frequency above a

characteristic frequency fL, and wherein the method comprises: defining the first capacitor device such that f1 > fL and defining the second capacitor device is such that f2 > fL , with f1 and f2 being respectively said first and second natural resonant frequency.