Monitoring Charging Efficiency of a Mobile Computing Device via a Power Bank

A portable power bank for charging a mobile computing device is described, and a dynamic charging efficiency is monitored while the power bank is charging the mobile computing device. Particularly, instantaneous power output of a battery of the power bank is compared to power received by a battery of the mobile computing device to determine efficiency. The charging of the mobile computing device by the power bank is interrupted and/or resumed based upon the charging efficiency at any given time, thereby preventing inefficient use of the power bank.