Nikon EN-EL20 Rechargeable Li-ion Battery Description. The Nikon EN-EL20 Rechargeable Li-ion Battery is a replacement or spare battery for the Nikon 1 series digital camera & possible future Nikon cameras. The battery puts out 7. 2V of power & has a capacity of 1020m Ah. Lithium-ion batteries are long-lasting power sources that are immune from the horrible plague of memory effect which kills a battery after repeated charging.