The Nitecore UNK1 is a USB battery charger designed exclusively for Nikon cameras and is compatible with a range of models. Offering dual slots on the front and back of the charger, slot 1 is compatible with the EN-EL15 battery and slot 2 with the EN-EL14 or EN-EL14a battery. Please note, the slots are compatible with different batteries and cannot charge two of the same cells simultaneously. The charger features a smart charging management system, monitoring battery types, capacities, internal resistance upon charging initiation and automatically applies the most appropriate charging current based on the monitored data.