Contactless charging system with priority consideration

A charging system comprising: a charger 121 capable of generating a field, for example using an inductive coil 120; two or more discrete devices 1, 30, 40, each comprising a rechargeable energy store 10, 31, 41 capable of powering the device, a pickup 12, 32, 42 for harnessing energy from the field, a switching device 14, 34, 44 having a first state in which it couples the pickup to the energy store for charging and a second in which it isolates the pickup; a data store storing an operating priority for each of the devices; and a controller having access to the data store and configured to control the switching device of one or more of the devices depending on the operating priority for that device. The system may estimate device power requirements and priority data may be transferred to other systems. The devices may be a datalogger and sensors.