Systems and methods for the wireless transfer of power between two hermetically sealed devices are described herein. An example system may include a battery package and a hermetically sealed body-implantable electronic device having an electronics package. The battery package may include one or more alignment structures, configured to removably align the battery package with the electronic device, a battery, and a wireless power transceiver. At least the battery and the wireless power transceiver of the battery package may be contained within a hermetic material separate from the electronic device. Power may be wirelessly transferred between the devices by any means, including inductive coupling or capacitive coupling. In some examples, the hermetically-sealed devices may be implanted in a living body.