Review on Rechargeable AAA Lithium Batteries With Micro USB Charging Port - 1000 Cycle, 1.5V/400MAh - Pre-Charged, 4/Pack by Brittany Williams

On the AAA batteries you plug a supplied micro USB into the side but on the AA batteries you have to take off a cap to reveal the USB charging connector. The cap is attached to the battery by a flimsy thin bungee chord that may not stay attached very long because of the wear-and-tear on the chord every time the battery is charged. The cap is also the positive (+) battery connector so if the chord breaks you'll probably lose the cap soon thereafter and then the battery won't work in any device. And yes, you HAVE to take the caps off to charge the batteries via USB even if the device you're using them in can charge rechargeable batteries.