In this chapter discusses the use of batteries for the purpose of storing electrical energy. Batteries are, perhaps, the most common approach to energy storage and are used on a wide range of scales. These applications include portable devices such as watches, mobile phones and computers, as well as battery electric vehicles, emergency back-up power systems and grid storage. The present chapter discusses the basic types of batteries and overviews the different battery chemistries that are in common use. The physics and chemistry of the energy storage mechanism in batteries is presented. Finally, battery applications are reviewed with an emphasis on vehicle use, remote and emergency power systems and grid back-up power for renewable energy systems.