Nikon EN-EL20a – Reliable Power for Your Camera. The Nikon EN-EL20a is a compact, rechargeable lithium-ion battery with a capacity of 1,110 mAh and a voltage of 7.2 V. It provides reliable power for extended shooting sessions and is compatible with Nikon 1 J1, J2, J3, J4, J5, S1, V3, AW1, as well as Coolpix A and P950 cameras. Weighing only 28 g, it is lightweight and ideal as a spare or backup battery.