CONTACT-LESS POWER TRANSFER

• US 20090189565A1
• Filed: 04/02/2009
• Published: 07/30/2009
• Est. Priority Date: 05/13/2002
• Status: Active Grant

• Current Assignee: Philips IP Ventures B.V. (Koninklijke Philips N.V.)
• Original Assignee: Access Business Group International LLC (Alticor Incorporated)
• Inventors: Beart, Pilgrim Giles William, Cheng, Lily Ka-Lai, Hay, James Westwood
• Granted Patent: US 7,714,537 B2
• Time in Patent Office: Days
• US Class Current: 320/108
• CPC Class Codes: H01F 27/245 made from sheets, e.g. grain-oriented H01F27/26 takes precedence
• CPC Class Codes: H01F 27/25 made from strips or ribbons H01F27/26 takes precedence
• CPC Class Codes: H01F 27/2804 Printed windings
• CPC Class Codes: H01F 3/02 made from sheets
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H01F 41/0226 from amorphous ribbons
• CPC Class Codes: H01F 41/0233 Manufacturing of magnetic circuits made from sheets magnetic cores made from sheets H01F27/245; soft magnetic alloys in the form of sheets H01F1/16
• CPC Class Codes: H01F 5/003 Printed circuit coils
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/70 involving the reduction of electric, magnetic or electromagnetic leakage fields
• CPC Class Codes: H02J 7/0042 characterised by the mechanical construction

Abstract

There is disclosed a system and method for transferring power without requiring direct electrical conductive contacts. There is provided a primary unit having a power supply and a substantially laminar charging surface having at least one conductor that generates an electromagnetic field when a current flows therethrough and having an charging area defined within a perimeter of the surface, the at least one conductor being arranged such that electromagnetic field lines generated by the at least one conductor are substantially parallel to the plane of the surface or at least subtend an angle of 45° or less to the surface within the charging area; and at least one secondary device including at least one conductor that may be wound about a core. Because the electromagnetic field is spread over the charging area and is generally parallel or near-parallel thereto, coupling with flat secondary devices such as mobile telephones and the like is significantly improved in various orientations thereof.

Claims

1. A system for transferring power without requiring direct electrical conductive contacts, the system comprising:

a power transfer surface shaped and arranged such that a secondary device can be placed in a working disposition on or in proximity to the surface to receive power when the system is in use;

a primary unit having a field generating means, distributed in two dimensions across a generating area at or substantially parallel to said power transfer surface, for generating an electromagnetic field over a power transfer area of said surface within which area the secondary device can couple flux effectively when in its said working disposition and which area is not substantially smaller than said generating area; and

a secondary device separable from the primary unit and including at least one electrical conductor with which the electromagnetic field generated by the field generating means couples with and induces a current to flow in the conductor when the secondary device is in said working disposition;

wherein the field generating means is configured such that, when a predetermined current is supplied thereto and the primary unit is effectively in electromagnetic isolation, field lines of the electromagnetic field generated by the field generating means are distributed in two dimensions over said power transfer area and, when considering the angles subtended by the field lines to a measurement plane that is parallel to the power transfer surface and is at the same distance therefrom as the secondary device when that device is in its said working disposition, an average of said angles over any quarter length part of said power transfer area, measured parallel to the direction of the field lines, is 45°

or less.

2. A system as claimed in claim 1 wherein said secondary device is carried in or by an object requiring power and can receive power from the primary unit when said object is placed on or in proximity to said power transfer surface so that the carried secondary device has its said working disposition.

3. A system as claimed in claim 2 wherein said object comprises at least one battery or cell and said secondary device is in the form of a flat adapter which is fitted over said battery or cell and which has thin electrodes insertable between terminals of the battery or cell and terminals of the object.

4. A system as claimed in claim 1 wherein said secondary device is carried in or by a rechargeable battery or cell fitted, or adapted to be fitted, into an object requiring power.

5. A system as claimed in claim 4 wherein, when said battery or cell is fitted into said object and said object is placed on or in proximity to said power transfer surface so that said secondary device has its said working disposition, the battery or cell can be recharged without removing it from said object.

6. A system as claimed in claim 4 wherein said rechargeable battery or cell is an industry-standard-sized battery or cell.

7. A system as claimed in claim 4 wherein said rechargeable battery or cell is of a size and/or shape dedicated or customized for a particular application.

8. A system as claimed in claim 4 wherein said rechargeable battery or cell further comprises an energy-storage means and a power conversion means for converting power received inductively by the secondary device into a form suitable for delivery to outside said battery or cell through external electrical connections thereof, or into a form suitable for recharging the energy-storage means, or into both said forms.

9. A system as claimed in claim 8 wherein said rechargeable battery or cell has charge-control means operable, when the secondary device is receiving power inductively, to meter the supply of inductively-received power to the external electrical connections and to the energy-storage means.

10. A system as claimed in claim 4 wherein the rechargeable battery or cell further comprises a flux concentrating means, and said at least one conductor is wound about said flux concentrating means.

11. A system as claimed in claim 10 wherein the flux concentrating means is at least partially wrapped around a central part of the battery or cell.

12. A system as claimed in claim 2 wherein said object is portable.

13. A system as claimed in claim 2 wherein said object is a portable electrical or electronic device.

14. A system as claimed in claim 2 wherein said object is a mobile communication device.

15. A system as claimed in claim 2 wherein said power transfer area is large enough to accommodate simultaneously two or more such secondary devices carried in or by different respective such objects.

16. A system as claimed claim 2 wherein said primary unit is part of an enclosure for said object.

17. A system as claimed in claim 1 wherein said primary unit is incorporated in an item of furniture having a surface which provides said power transfer surface.

18. A system as claimed in claim 1 wherein the power transfer area is large enough to contain a footprint area of said secondary device in more than one position and/or orientation in which the secondary device can be placed, said footprint area being an area parallel to said power transfer surface occupied by at least one of said at least one electrical conductor and a core of the secondary device when the secondary device is in its said working disposition.

19. A system as claimed in claim 18 wherein said power transfer area is large enough to contain said footprint area of said secondary device in any said orientation.

20. A system as claimed in claim 1 wherein said power transfer area is provided with a flux guide having a relative permeability less than that of a core of said secondary device.

21. A system as claimed in claim 1 wherein the at least one conductor in the secondary device is wound about a core that serves to concentrate flux therein.

22. A system as claimed in claim 21 wherein the core is made of a magnetically permeable materials.

23. A system as claimed in claim 22 wherein the core is made of an amorphous magnetic material.

24. A system as claimed in claim 23 wherein the core is made of a substantially non-annealed amorphous magnetic material.

25. A system as claimed in claim 21 wherein the core is formed as a flexible ribbon.

26. A system as claimed in claim 21 wherein a thickness of said core is 2 mm or less.

27. A system as claimed in claim 21 wherein a thickness of said core is 1 mm or less.

28. A system as claimed in claim 1 wherein the secondary device has a substantially laminar form factor.

29. A system as claimed in claim 1 wherein the secondary device has a primary axis and couples with the electromagnetic field when located on or in proximity to the power transfer area in any rotation about its axis.

30. A system as claimed in claim 1 wherein the secondary device comprises a coil which provides said at least one conductor and which is arranged such that a central axis of the coil is substantially non-perpendicular to the power transfer area when the secondary device is in its said working disposition.

31. A system as claimed in claim 30 wherein said central axis is substantially parallel to the power transfer area when the secondary device is in its said working disposition.

32. A system as claimed in claim 21 wherein said core is arranged such that a longitudinal axis thereof is substantially non-perpendicular to the power transfer area when the secondary device is in its said working disposition.

33. A system as claimed in claim 32 wherein said longitudinal axis is substantially parallel to the power transfer area when the secondary device is in its said working disposition.

34. A primary unit for use in a power transfer system having a power transfer surface shaped and arranged such that a secondary device, separable from the primary unit, can be placed in a working disposition on or in proximity to the surface to receive power from the primary unit without requiring direct electrical conductive contacts between the primary unit and the secondary device, the primary unit comprising:

a field generating means, distributed in two dimensions across a generating area at or substantially parallel to said power transfer surface, for generating an electromagnetic field over a power transfer area of said surface within which area the secondary device can couple flux effectively when in its said working disposition and which area is not substantially smaller than said generating area;

wherein the field generating means is configured such that, when a predetermined current is supplied thereto and the primary unit is effectively in electromagnetic isolation, field lines of the electromagnetic field generated by the field generating means are distributed in two dimensions over said power transfer area and, when considering the angles subtended by the field lines to a measurement plane that is parallel to the power transfer surface and is at the same distance therefrom as the secondary device when that device is in its said working disposition, an average of said angles over any quarter length part of the power transfer area, measured parallel to the direction of the field lines, is 45°

or less.

35. A primary unit as claimed in claim 34 wherein a height of said field generating means, measured in said generating area and in a direction substantially perpendicular thereto, is less than either a width or a length of said power transfer area on said power transfer surface.

36. A primary unit as claimed in claim 35 wherein said height is no more than half of the length or half of the width of the power transfer area.

37. A primary unit as claimed in claim 35 wherein said height is no more than ⅕

of the length or ⅕

of the width of the power transfer area.

38. A primary unit as claimed in claim 34 wherein said power transfer area is substantially coextensive with said generating area.

39. A primary unit as claimed in claim 34 wherein the primary unit is in the form of a flat platform having a main face which provides said power transfer surface.

40. A primary unit as claimed in claim 34 wherein said power transfer surface is substantially planar.

41. A primary unit as claimed in claim 34 wherein said power transfer surface is curved.

42. A primary unit as claimed in claim 34 wherein said field generating means comprises at least one electrical conductor that is distributed in two dimensions at or substantially parallel to the power transfer surface.

43. A primary unit as claimed in claim 34 wherein said field generating means comprises at least one electrical conductor wound onto at least part of a magnetically permeable former that is distributed in two dimensions at or substantially parallel to the power transfer surface.

44. A primary unit as claimed in claim 34 wherein the primary unit includes a pair of conductors, each conductor having adjacent coplanar windings which have mutually substantially parallel linear sections arranged so as to produce a substantially uniform electromagnetic field extending generally parallel to the plane of the windings but substantially at right angles to the parallel sections.

45. A primary unit as claimed in claim 44 wherein the windings of each conductor of the pair are formed in a generally spiral shape comprising a series of turns having substantially parallel straight sections.

46. A primary unit as claimed in claim 44 wherein the primary unit includes first and second such pairs of conductors which are superimposed in substantially parallel planes with the substantially parallel linear sections of the first pair arranged generally at right angles to the substantially parallel linear sections of the second pair, and further comprising a driving circuit which is arranged to drive the conductors in such a way as to generate a resultant field which rotates in a plane substantially parallel to the planes of the windings.

47. A primary unit as claimed in claim 34 wherein said field generating means includes a plurality of conductors and the primary unit has a driving means for driving the plurality of conductors so as to cause a directional component of the electromagnetic field lines, resolved onto the power transfer area, to be changed over time.

48. A primary unit as claimed in claim 47 wherein the driving means is operable to drive the plurality of conductors so as to cause the resolved directional component of the field lines to be switched between at least two different directions.

49. A primary unit as claimed in claim 47 wherein the driving means is operable to drive the plurality of conductors so as to cause the resolved directional component of the field lines to be moved through an angle.

50. A primary unit as claimed in claim 47 wherein the driving means is operable to drive the plurality of conductors so as to cause the resolved directional component of the field lines to be rotated.

51. A primary unit as claimed in claim 34 wherein the field lines over said power transfer area are substantially parallel to each other when projected onto the power transfer area.

52. A primary unit as claimed in claim 34 wherein an instantaneous net flow of current in said field generating means when energized is in substantially one direction.

53. A primary unit as claimed in claim 34 wherein said field generating means does not project beyond the power transfer surface.

54. A primary unit as claimed in claim 34 wherein said power transfer area is provided with a substrate of a magnetic material.

55. A primary unit as claimed in claim 34 wherein said primary unit includes at least one selectively operable capacitor and control means operable to employ said at least one capacitor to selectively change a capacitance of a circuit including said field generating means and the at least one capacitor in response to a detected presence of one or more secondary devices.

56. A primary unit as claimed in claim 34 wherein the primary unit includes a power supply.

57. A primary unit as claimed in claim 34 having two or more such power transfer areas in different parts of the power transfer surface.

58. A primary unit as claimed in claim 57 wherein said field generating means is configured to generate an electromagnetic field over more than one of said two or more power transfer areas.

59. A primary unit as claimed in claim 34 having a plurality of such field generating means configured to generate an electromagnetic field over the one said power transfer area.

60. A method of transferring power from a primary unit to a secondary device, separable from the primary unit, without requiring direct electrical conductive contacts between the primary unit and the secondary device, the method comprising:

generating an electromagnetic field over a power transfer area of a power transfer surface using a field generating means distributed in two dimensions across a generating area at or substantially parallel to said power transfer surface, the power transfer surface being shaped and arranged such that the secondary device can be placed in a working disposition on or in proximity to the power transfer surface to receive power from the primary unit, and the power transfer area being an area of said surface within which the secondary device can couple flux effectively when in its said working disposition and being not substantially smaller than said generating area, and said field being such that, when the primary unit is effectively in electromagnetic isolation, field lines of the field are distributed in two dimensions over said power transfer area and, when considering the angles subtended by the field lines to a measurement plane that is parallel to the power transfer surface and is at the same distance therefrom as the secondary device when that device is in its said working disposition, an average of said angles over any quarter length part of the power transfer area, measured parallel to the direction of the field lines, is 45°

or less; and

placing such a secondary device in said working disposition so that the electromagnetic field couples with at least one electrical conductor of said secondary device and induces a current to flow therein.

61. A method as claimed in claim 60 comprising changing over time a directional component of the electromagnetic field lines resolved onto the power transfer area.

62. A method as claimed in claim 61 comprising switching the resolved directional component of the field lines between at least two different directions.

63. A method as claimed in claim 61 comprising moving the resolved directional component of the field lines through an angle.

64. A method as claimed in claim 61 comprising rotating the resolved directional component of the field lines.

65. A method as claimed in claim 60 comprising generating field lines over said power transfer area that are substantially parallel to each other when projected onto the power transfer area.

66. A method as claimed in claim 60 comprising driving the field generating means such that an instantaneous net flow of current therein is in substantially one direction.

67. A method as claimed in claim 60 comprising detecting a presence of one or more secondary devices on or in proximity to said power transfer surface and, in response to the detected presence, employing at least one selectively operable capacitor to selectively change a capacitance of a circuit including said field generating means the at least one capacitor.

68. A method as claimed in claim 60 comprising guiding the flux, at least within said power transfer area, using a flux guide having a relative permeability less than that of a core of said secondary device.

69. A method as claimed in claim 60 wherein said electromagnetic field generated by said field generating means is such that the secondary device can couple flux effectively when placed in its said working disposition anywhere within a perimeter of said power transfer area.

70. A system for transferring power without requiring direct electrical conductive contacts, the system comprising:

a power transfer surface shaped and arranged such that a secondary device can be placed in a working disposition on or in proximity to a power transfer area of the surface to receive power when the system is in use;

a primary unit having a field generating means for generating an electromagnetic field distributed over the power transfer area; and

a secondary device separable from the primary unit and having an inductive coupling circuit which is arranged to couple with the electromagnetic field generated by the primary unit when the secondary device is in its said working disposition, said coupling circuit being adapted to couple primarily with field lines of the field that are generally parallel to the power transfer surface;

wherein the field generating means comprises a spiral coil arranged generally parallel to the power transfer surface at or beneath the power transfer area; and

when the secondary device is in its said working disposition the inductive coupling circuit extends over a plurality of radially-spaced portions of the spiral coil, the part of the power transfer area over which the inductive coupling means extends being sufficiently small, relative to the coil, that within said part said coil portions extend generally in parallel with one another in one general direction.

71. A system as claimed in claim 70 wherein the inductive coupling circuit is arranged to couple with said field when field lines of the field pass through the coupling means in a predetermined coupling direction, and the said coil portions within said part extend generally perpendicularly to said predetermined coupling direction.

72. A system as claimed in claim 70 wherein said field generating means comprises a first coil having a generally flat spiral shape and a second coil wound in a toroidal form through the center of the first coil and out to the perimeter thereof in a radial fashion.

73. A system as claimed in claim 72 having driving means for driving said first and second coils alternately.

74. A system as claimed in claim 72 having driving means for driving said first and second coils in quadrature.

75. A system as claimed in claim 70 wherein the or each said coil comprises conductive tracks formed on a planar surface.

76. A system as claimed in claim 70 wherein said primary unit further comprises a magnetic core across which the or each said coil extends.

77. A system as claimed in claim 70 wherein said inductive coupling means comprises at least one electrical conductor.

78. A system as claimed in claim 70 wherein said inductive coupling circuit comprises a coil.

79. A system as claimed in claim 78 wherein said coil of said inductive coupling circuit is arranged such that a central axis thereof is substantially non-perpendicular to the power transfer surface when the secondary device is in its said working disposition.

80. A system as claimed in claim 79 wherein said central axis is substantially parallel to said power transfer surface when the secondary device is in its said working disposition.

81. A system as claimed in claim 70 wherein said inductive coupling means comprises a flux-concentrating core.

82. A system as claimed in claim 81 wherein said core of said inductive coupling means is arranged such that a longitudinal axis thereof is substantially non-perpendicular to the power transfer surface when the secondary device is in its said working disposition.

83. A system as claimed in claim 82 wherein said longitudinal axis is substantially parallel to the power transfer surface when the secondary device is in its said working disposition.

84. A system as claimed in claim 70 wherein said secondary device is carried in or by an object requiring power and can receive power from the primary unit when said object is placed on or in proximity to said power transfer surface so that the carried secondary device has its said working disposition.

85. A system as claimed in claim 84 wherein said object comprises at least one battery or cell and said secondary device is in the form of a flat adapter which is fitted over said battery or cell and which has thin electrodes insertable between terminals of the battery or cell and terminals of the object.

86. A system as claimed in claim 70 wherein said secondary device is carried in or by a rechargeable battery or cell fitted, or adapted to be fitted, into an object requiring power.

87. A system as claimed in claim 86 wherein, when said battery or cell is fitted into said object and said object is placed on or in proximity to said power transfer surface so that said secondary device has its said working disposition, the battery or cell can be recharged without removing it from said object.

88. A system as claimed in claim 86 wherein said rechargeable battery or cell is an industry-standard-sized battery or cell.

89. A system as claimed in claim 86 wherein said rechargeable battery or cell is of a size and/or shape dedicated or customized for a particular application.

90. A system as claimed in claim 86 wherein said rechargeable battery or cell further comprises an energy-storage means and a power conversion means for converting power received inductively by the secondary device into a form suitable for delivery to outside said battery or cell through external electrical connections thereof, or into a form suitable for recharging the energy-storage means, or into both said forms.

91. A system as claimed in claim 90 wherein said rechargeable battery or cell has charge-control circuitry operable, when the secondary device is receiving power inductively, to meter the supply of inductively-received power to the external electrical connections and to the energy-storage means.

92. A system as claimed in claim 86 wherein the rechargeable battery or cell further comprises a flux concentrating means, and said at least one conductor is wound about said flux concentrating means.

93. A system as claimed in claim 92 wherein the flux concentrating means is at least partially wrapped around a central part of the battery or cell.

94. A system as claimed in claim 84 wherein said object is portable.

95. A system as claimed in claim 84 wherein said object is a portable electrical or electronic device.

96. A system as claimed in claim 84 wherein said object is a mobile communication device.

97. A system as claimed in claim 84 wherein said power transfer area is large enough to accommodate simultaneously two or more such secondary devices carried in or by different respective such objects.

98. A system as claimed in claim 84 wherein said primary unit is part of an enclosure for said object.

99. A system as claimed in claim 70 wherein said primary unit is incorporated in an item of furniture having a surface which provides said power transfer surface.

100. A system as claimed in claim 70 wherein a height of said field generating means, measured in a direction substantially perpendicular to the power transfer surface, is less than either a width or a length of said power transfer area on said power transfer surface.

101. A system as claimed in claim 100 wherein said height is no more than half of the length or half of the width of the power transfer area.

102. A system as claimed in claim 100 wherein said height is no more than ⅕

of the length or ⅕

of the width of the power transfer area.

103. A system as claimed in claim 70 wherein the primary unit is in the form of a flat platform having a main face which provides said power transfer surface.

104. A system as claimed in claim 70 wherein said power transfer surface is substantially planar.

105. A system as claimed in claim 70 wherein said power transfer surface is curved.

106. A system as claimed in claim 70 wherein said field generating means does not project beyond the power transfer surface.

107. A system as claimed in claim 70 wherein the primary unit further comprises driving means for applying electrical drive signals to said field generating means such that, in at least one said part of the power transfer area, said field lines, when resolved onto the power transfer area, change in direction over time.

108. A system as claimed in claim 107 wherein said driving means are operable to apply electrical drive signals to said field generating means such that said field lines are switched between two or more different predetermined directions over time.

109. A system as claimed in claim 107 wherein the driving means are operable to apply electrical drive signals to said field generating means such that the field line directions are rotated through an angle over time.

110. A system as claimed in claim 107 wherein said driving means are operable to apply electrical drive signals to said field generating means such that the field line directions are rotated through a complete circle over time.

111. A portable electrical or electronic device, adapted to receive power inductively from an external unit that has a field generating surface and a field generator which generates an electromagnetic field at or over the field generating surface, the device being adapted to receive power from the external unit when placed in an intended power-receiving disposition on or in proximity to said field generating surface and being separable from the external unit when not receiving power therefrom, the device comprising:

a housing including a predetermined portion having an external surface which faces said field generating surface when the device is placed in said power-receiving disposition, said predetermined portion also having an internal surface; and

a magnetic core component arranged within said housing on or in proximity to said internal surface of said predetermined portion so that the core component couples with said field when the device is in its said power-receiving disposition, the magnetic core component including a thin sheet of magnetic material and also including a coil wound around said sheet for receiving power inductively from the external unit, the sheet and the coil being arranged so that a longitudinal axis of said sheet and a central axis of said coil each extend generally parallel to said field generating surface when the device is in said power-receiving disposition.

112. A portable electrical or electronic device as claimed in claim 111 wherein said thin sheet is substantially flat.

113. A portable electrical or electronic device as claimed in claim 111 wherein said thin sheet is curved.

114. A portable electrical or electronic device as claimed in claim 111 wherein said coil extends in its axial direction over a distance that is large compared to a thickness of said magnetic core component.

115. A portable electrical or electronic device as claimed in claim 111 wherein the largest dimension of said thin sheet is in the direction of said central axis of said coil.

116. A portable electrical or electronic device as claimed in claim 111 wherein said magnetic material is amorphous magnetically permeable material.

117. A portable electrical or electronic device as claimed in claim 111 wherein said magnetic core component has two such coils, the respective central axes of said two coils extending in mutually orthogonal directions generally parallel to said field generating surface when the device is in said power-receiving disposition.

118. A rechargeable battery adapted to receive power inductively from a primary unit when fitted into a space in a portable electrical or electronic device, the device comprising a cover element having a substantially planar portion with inner and outer surfaces and being adapted to be placed with said outer surface on or in proximity to such a primary unit when the battery is to be recharged, and the device being adapted to retain the battery in the space with its longitudinal axis extending generally parallel to a plane of said planar portion, the battery comprising:

a power-receiving element comprising a coil which is in close proximity to said inner surface of said cover element when the cell is so retained in said space and which has a central axis that extends generally parallel to a plane of said planar portion, for receiving power inductively from the primary unit when the device is so placed on or in proximity to the primary unit; and

a rechargeable energy-storing element connected to the power-receiving element for storing the power received inductively by the power-receiving element, said power-receiving element in the form of a thin sheet.

119. A rechargeable battery as claimed in claim 118 wherein said thin sheet is substantially flat.

120. A rechargeable battery as claimed in claim 118 wherein said thin sheet is curved.

121. A rechargeable battery as claimed in claim 118 wherein said power-receiving element further comprises a core of magnetic material, said core having a longitudinal axis which extends generally parallel to said plane.

122. A rechargeable battery as claimed in claim 121 wherein said coil is wound about said core.

123. A rechargeable battery as claimed in claim 121 wherein said coil extends in its axial direction over a distance that is large compared to a thickness of said power-receiving element.

124. A rechargeable battery as claimed in claim 121 wherein said core is made of amorphous magnetically permeable material.

125. A rechargeable battery as claimed in claim 118 wherein said power-receiving element has two such coils, the respective central axes of said two coils extending in mutually orthogonal directions generally parallel to said plane.

126. A rechargeable battery as claimed in claim 118 wherein said portable electrical or electronic device has a metal plane extending generally parallel to said plane of said planar portion of said cover element.

127. A rechargeable battery as claimed in claim 118, wherein the portable electrical or electronic device has a printed circuit board extending generally parallel to a plane of said planar portion of said cover element.

128. A rechargeable battery as claimed in claim 118 wherein said planar portion of said cover element includes metal.

129. A rechargeable battery as claimed in claim 121 wherein, when the battery is retained in said space, said core is located between said cover element and components of the device susceptible to electromagnetic fields so that the core can serve to reduce the effects on such components of an electromagnetic field generated by the primary unit.

130. A rechargeable battery as claimed in claim 118 wherein said rechargeable battery further comprises a power conversion unit which converts power received inductively by the power-receiving element into a form suitable for delivery to outside said battery through external electrical connections thereof, or into a form suitable for recharging the energy-storing element, or into both said forms.

131. A rechargeable battery as claimed in claim 130 wherein said rechargeable battery has a charge-control unit operable, when the power-receiving element is receiving power inductively, to meter the supply of inductively-received power to the external electrical connections and to the energy-storing element.

132. A rechargeable battery as claimed in claim 118 having an enclosure and external electrical connections similar in dimensions to an industry-standard battery.

133. A rechargeable battery adapted to receive power inductively from a primary unit when fitted into a space in a portable electrical or electronic device, the device comprising a cover element having a substantially planar portion with inner and outer surfaces and being adapted to be placed with said outer surface on or in proximity to such a primary unit when the battery is to be recharged, and the device being adapted to retain the battery in the space with its longitudinal axis extending generally parallel to a plane of said planar portion, the battery comprising:

a power-receiving element comprising a coil which is in close proximity to said inner surface of said cover element when the cell is so retained in said space and which has a central axis that extends generally parallel to a plane of said planar portion, for receiving power inductively from the primary unit when the device is so placed on or in proximity to the primary unit; and

a rechargeable energy-storing element connected to the power-receiving element for storing the power received inductively by the power-receiving element;

wherein a thickness of said power-receiving element, measured in a direction perpendicular to said plane, is small relative to the dimensions of the power-receiving element parallel to said plane.

142. A rechargeable battery as claimed in claim 133 wherein said rechargeable battery has a charge-control unit operable, when the power-receiving element is receiving power inductively, to meter the supply of inductively-received power to the external electrical connections and to the energy-storing element.

134. A rechargeable battery adapted to receive power inductively from a primary unit, the battery comprising:

a generally cylindrical body having a central axis;

a power-receiving element, comprising a coil having a central axis extending generally in parallel with said central axis of said body, for receiving power inductively from the primary unit when the battery is placed on or in proximity to a power transfer surface of the primary unit with said central axis of said body lying across the surface; and

a rechargeable energy-storing element connected to said power-receiving element for storing the power received inductively by the power-receiving element;

wherein said power-receiving element is in the form of a thin sheet.

135. A rechargeable battery as claimed in claim 134 wherein said thin sheet is curved.

136. A rechargeable battery as claimed in claim 134 wherein said thin sheet is wrapped circumferentially around said body or around another generally cylindrical component of the battery.

137. A rechargeable battery as claimed in claim 134 wherein said power-receiving element further comprises a core of magnetic material, said core having a longitudinal axis which extends generally parallel to said central axis of said body.

138. A rechargeable battery as claimed in claim 137 wherein said coil is wound about said core.

139. A rechargeable battery as claimed in claim 137 wherein said coil extends in its axial direction over a distance that is large compared to a thickness of said power-receiving element.

140. A rechargeable battery as claimed in claim 137 wherein said core is made of amorphous magnetically permeable material.

141. A rechargeable battery as claimed in claim 134 wherein said rechargeable battery further comprises a power conversion unit which converts power received inductively by the power-receiving element into a form suitable for delivery to outside said battery through external electrical connections thereof, or into a form suitable for recharging the energy-storing element, or into both said forms.

143. A rechargeable battery as claimed in claim 134 having an enclosure and external electrical connections similar in dimensions to an industry-standard battery.