PowerPACK: A wireless power distribution system for wearable devices

Motivated by the prevalence of small, battery-powered devices in many pervasive computing research and deployment scenarios, and the frustration encountered when a particular device is found to be useless due to a discharged internal battery, we present a backpack-worn wireless (non-contact) power distribution system. This system is designed to distribute power from a single point of generation or bulk storage to a variety of endpoint devices. Endpoint devices can operate or recharge their internal batteries from the central source when they are stowed in a powered pocket in the backpack. We also demonstrate low bandwidth (10 Kbps) bidirectional communication across the power link. This communication channel could be used to inventory the coupled devices, prioritize power delivery to more important devices, detect the unauthorized removal of a device, authenticate the recipients of power, or distribute cryptographic keys for further data exchange using a Bluetooth, WiFi, or another high data rate connection. Using a 125 KHz resonant inductive coupling mechanism and a dynamic tuning system, we demonstrate a power transfer efficiency of 80% for small (USB class) device loads.