Possible battery systems and current performance were reviewed, with a summary of battery architectures, fabrication and potential miniaturization. In the near future, more and more biocompatible batteries will be employed to power medical devices. Once their current shortcomings, mainly limited energy and power capacities, have been brought under control, biocompatible batteries could also play more prominent roles in devices not necessarily related to medical implants and health monitoring devices, but also in electronic appliances, e.g. autonomous robots, drones, and environmental sensing systems.