Review on EN-EL14 & EN-EL14A Battery Dual Charger Kit For Nikon D3500, D3300, D3100, D3200,D3400,D5100,D5200 ,D5300 ,D5500 ,D5600 Coolpix P7000 P7100 P7700 And P7800 Cameras - Artman 2 Pack 1300MAh by Clarence Calcara

If you plug the charger into a USB port that supplies more than 2amps of power, yes you can charge both batteries at once. However, if you think you can charge both batteries at once using port on your computer you have a problem. If you are going to use your Smartphones USB charger, chances are you will only be able to only charge one battery at a time with this charger because most only supply approximately 1 to 1.5 amps and you need a USB charging port that supplies more than 2amps of power to be able to charge both batteries simultaneously with this charger. This is part of the reason that products that use USB for power tend to disappoint. So, you if you only have access to a USB charging port with less than 2 amps you will only be able to charge 1 battery at a time with the supplied battery charger.So, in short, a decent product for the price, I think the batteries themselves are great for the money (although not as long lasting as the OEM's), but the charger while acceptable could have been excellent if supplied with a regular AC adapter instead of just a USB cable.