Wireless sensor nodes (WSNs) are expected to play an increasing role in multiple application areas. These application areas vary from networks around the human body, sensors in smart tires, sensor networks that can control the safety and comfort levels throughout smart buildings, sensors that monitor the necessity for maintenance and sensors that track the conditions of food throughout the distribution chain. These wireless sensors need energy, which can be supplied by a battery or an energy harvester. However, even when an energy harvester is applied, energy storage is required to serve as energy buffer. In this review, the requirements that different types of wireless sensor networks impose on these batteries are explored, and several suitable types of batteries are reviewed. Moreover, the trends in battery development are described, and the future improvements are predicted. Finally, the possibilities are discussed to select a battery with properties that are matched to the requirements of the sensor nodes. Copyright (C) 2012 John Wiley & Sons, Ltd.