Ener1, Inc., together with its subsidiaries, engages in designing, developing, and manufacturing rechargeable lithium-ion batteries and battery systems for energy storage in the United States and South Korea. It operates in three segments: Battery, Fuel Cell, and Nanotechnology. The Battery segment offers lithium-ion batteries for hybrid, plug-in hybrid, and electric vehicles, as well as for buses, trucks, and other alternative transportation vehicles. This segment also provides battery cells and battery packs. The Fuel Cell segment develops and markets fuel cells and fuel cell systems. The Nanotechnology segment involves in developing nanotechnology related manufacturing processes and materials. The company offers its products to customers in the transportation, stationary power, military, and small cell markets. Ener1, Inc. was founded in 1985 and is headquartered in New York, New York.