Two batteries are better than one, but only if they are charged and ready for action. The ProMaster Dually Charger can charge two batteries simultaneously, or just 1 if required. It is compact and convenient with a USB-A input cable that neatly stores itself in the bottom of the charger. Since it draws power from USB sources, you can use the Dually Charger with a USB AC Adapter (not included), laptop, power bank, car charger, and more.