TP-LINK TL-MR22U

Overview
Battery: Li-Ion, 3.7V, 5200 mAh

Default device firmware: 3.17.1 Build 140123 Rel.31844n
 * Default firmware contains backdoor account with username admin and password adminpwd.
 * Not sure what it is used for since the regular user has only password field on login screen.

USB port provides between 0.8A and 1.2A of current
 * in both charge and power-on modes.

Links of Interest

 * TP-Link TL-MR22U on OpenWrt wiki
 * TP-Link TL-MR22U on OpenWrt forums