ProMaster Dually Charger - USB - Nikon EN-EL15B, EN-EL15A, EN-EL15

The technical details behind this Charger
ProMaster Dually Charger - USB - Nikon EN-EL15B simultaneously charges two batteries. It features a compact design and is convenient with a USB-A input cable that neatly stores itself in the bottom of the charger.
USB Power Source 
 Draws power from USB sources, you can use the Dually Charger with a USB AC Adapter (not included), power bank, car charger, laptop, and more.
 Dual-Charging function