Unfortunately there are many subpar USB power banks on the market that overestimate there capacity. Many people take the posted capacities at face value but it is beneficial to confirm. I have a cheap USB safety tester that reads the voltage and current coming out a usb port and from that can capture capacity.
I ran a new power bank from 100% -> 0% and for those two trials I got a capacity of 7.080Ah & 7.131Ah. The reported capacity was 26.8Ah and other users also reported capacities less than that. I will also be testing the capacity of charging as the tester itself has some power draw that might negatively influence the measurement.
