Wireless energy transfer for rechargeable batteries

1. An assembly configured to receive power wirelessly through an oscillating magnetic field generated by a wireless power source, the assembly comprising:

a first resonator coil having a first characteristic size and configured to couple to a first electrical load; and

a second resonator coil having a second characteristic size and positioned so that a minimum distance between the first resonator coil and the second resonator coil is less than half as large as a larger of the first and second characteristic sizes,

wherein the second resonator coil is oriented with respect to the first resonator coil so that a value of a coupling parameter k between the first and second resonator coils is smaller by a factor of at least two than a maximum value of k for any orientation of the second resonator coil for the same minimum distance between the first and second resonator coils.

2. The assembly of claim 1 , wherein the first resonator coil is integrated into a first battery structure and the second resonator coil is integrated into a second battery structure.

3. The assembly of claim 1 , wherein the second resonator coil is coupled to the first electrical load.

4. The assembly of claim 1 , wherein the first resonator coil comprises a capacitively loaded conducting loop.

5. The assembly of claim 1 , wherein at least one of the first resonator coil and the second resonator coil is configured to receive power wirelessly through an oscillating magnetic field generated by one or more additional resonators.

6. The assembly of claim 1 , wherein the value of k is less than 20% of the maximum value of k between the first and second resonator coils.

7. The assembly of claim 1 , wherein at least one of the first and second resonator coils has a quality factor of at least 100.

8. An apparatus for wireless energy transfer, comprising:

a first member comprising:

a first magnetic resonator configured to receive wireless energy via oscillating magnetic fields; and

a first housing that at least partially encloses the first magnetic resonator and has a form factor that corresponds to a shape of a battery; and

a second member comprising:

a second magnetic resonator configured to receive wireless energy via oscillating magnetic fields; and

a second housing that at least partially encloses the second magnetic resonator and has a form factor that corresponds to the form factor of the first housing,

wherein the first resonator is positioned asymmetrically in the first housing; and

wherein when the first and second members are positioned antiparallel at a distance d, a value of a coupling parameter k between the first and second magnetic resonators is less than 50% of a maximum value of k for any non-antiparallel positioning of the first and second members at the distance d.

9. The apparatus of claim 8 , wherein the first housing has a substantially cylindrical shape, and wherein the form factor of the first housing corresponds to a form factor of one of a AA sized battery, a AAA sized battery, and a D sized battery.

10. The apparatus of claim 9 , wherein the first magnetic resonator comprises an electrical conductor forming loops within the first housing.

11. The apparatus of claim 10 , wherein the electrical conductor is formed on a flexible substrate.

12. The apparatus of claim 10 , wherein the first member comprises a magnetic material, and wherein the magnetic material is at least partially encircled by the electrical conductor loops.

13. The apparatus of claim 10 , wherein the first member comprises a rechargeable battery connected to the first magnetic resonator.

14. The apparatus of claim 13 , wherein energy captured by the first magnetic resonator is stored in the rechargeable battery.

15. The apparatus of claim 8 , wherein the value of k is less than 20% of the maximum value of k.

16. A wireless battery system comprising a plurality of wireless batteries, each wireless battery comprising:

a cylindrical enclosure, symmetrical around an axis, and comprising a first end and a second end with a positive terminal on the first end and a negative terminal on the second end; and

a magnetic resonator configured to receive energy wirelessly through oscillating magnetic fields, the magnetic resonator comprising a plurality of loops of conductive material oriented coaxially with the symmetry axis of the enclosure,

wherein the magnetic resonator is positioned asymmetrically along the symmetry axis with respect to the first and second ends; and

wherein when any two of the wireless batteries are separated by a distance d and positioned such that their respective symmetry axes are parallel and the first end of one of the two wireless batteries is coplanar with the second end of the other of the two wireless batteries, a value of a coupling parameter k between the two wireless batteries is less than half of a maximum value of k for any orientation of the two wireless batteries at the distance d.