A wearable device for wirelessly charging a chargeable device 171, the wearable device comprising means for generating a magnetic field that comprises at least two transmitting coils (200-1 - 200-8), each configured to generate a respective component of the magnetic field； and means for shaping the magnetic field, in dependence on at least one of a location, orientation and shape of the chargeable device, by configuring the respective magnetic field component generated by each transmit coil to optimise the magnetic field for charging the chargeable device. Also disclosed is a device for wirelessly charging a chargeable device comprising two transmitting coils mechanically coupled to one another for movement into a plurality of different positions relative to one another to minimise magnetic coupling between the two. Also disclosed is a method of calibrating an apparatus for charging a chargeable device comprising determining an impedance of each of a plurality of transmitting coils and determining a voltage to apply to each coil based on this impedance.
