Coil constructions for improved inductive energy transfer

An inductor coil for an inductive energy transfer system includes multiple layers of a single wire having windings that are interlaced within at least two of the multiple layers such that both an input end and an output end of the wire enter and exit the coil on a 5 same side of the coil. The input end and the output end of the wire may abut one another at the location where the input and output wires enter and exit the inductor coil. The wire can include one or more bundles of strands and the strands in each bundle are twisted around an axis extending along a length of the wire, and when there are at least two bundles, the bundles may be twisted around the axis. At least one edge of the inductor 10 coil can be formed into a variety of shapes, such as in a curved shape. WO 2015/184063 PCT/US2015/032826